iSCSI 5-August-02 IPS Julian Satran Internet Draft Kalman Meth draft-ietf-ips-iscsi-15.txt IBM Category: standards-track Costa Sapuntzakis Cisco Systems Mallikarjun Chadalapaka Hewlett-Packard Co. Efri Zeidner SANGate iSCSI Julian Satran Expires February 2003 1 iSCSI 5-August-02 Status of this Memo This document is an Internet-Draft and fully conforms to all provi- sions of Section 10 of [RFC2026]. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for at most six months and may be updated, replaced, or made obsolete by other documents at any time. It is inappropriate to use Internet- Drafts as reference mate- rial or to cite them except as "work in progress." The list of Internet-Drafts can be accessed at http://www.ietf.org/ ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Abstract The Small Computer Systems Interface (SCSI) is a popular family of protocols for communicating with I/O devices, especially storage devices. This document describes a transport protocol for SCSI that works on top of TCP. The iSCSI protocol aims to be fully compliant with the rules laid out in the SCSI Architecture Model - 2 [SAM2] document. The current version of iSCSI is 0. Acknowledgements This protocol was developed by a design team that, beside the authors, included Daniel Smith, Ofer Biran, Jim Hafner and John Hufferd (IBM), Mark Bakke (Cisco), Randy Haagens (HP), Matt Wakeley (Agilent, now Sierra Logic), Luciano Dalle Ore (Quantum), Paul Von Stamwitz (Adaptec, now TrueSAN Networks). Also, a large group of people contributed to this work through their review, comments and valuable insights. We are grateful to all them. We are especially grateful to those who found the time and patience to take part in our weekly phone conferences and intermediate meet- ings in Almaden and Haifa, so helping to shape this document: Prasen- jit Sarkar, Meir Toledano, John Dowdy, Steve Legg, Alain Azagury (IBM), Dave Nagle (CMU), David Black (EMC), John Matze (Veritas - now Okapi Software), Steve DeGroote, Mark Schrandt (Cisco), Gabi Hecht (Gadzoox), Robert Snively and Brian Forbes (Brocade), Nelson Nachum Julian Satran Expires February 2003 2 iSCSI 5-August-02 (StorAge), Uri Elzur (Broadcom). Many more helped clean and improve this document within the IPS working group. We are especially grate- ful to David Robinson and Raghavendra Rao (Sun), Charles Monia, Joshua Tseng (Nishan), Somesh Gupta (Silverback), Michael Krause, Pierre Labat, Santosh Rao, Matthew Burbridge, Bob Barry, Robert Elliott, Nick Martin (HP), Stephen Bailey (Sandburst), Steve Senum, Ayman Ghanem, Dave Peterson (Cisco), Barry Reinhold (Trebia Net- works), Bob Russell (UNH), Eddy Quicksall (iVivity, Inc.), Bill Lynn and Michael Fischer (Adaptec), Vince Cavanna, Pat Thaler (Agilent), Jonathan Stone (Stanford), Luben Tuikov (Splentec), Paul Koning (EqualLogic)), Michael Krueger (Windriver), Martins Krikis (Intel), Doug Otis (Sanlight), John Marberg (IBM), Robert Griswold and Bill Moody (Crossroads), Yaron Klein (Sanrad). The recovery chapter was enhanced with help from Stephen Bailey (Sandburst), Somesh Gupta (Silverback) and Venkat Rangan (Rhapsody Networks). Eddy Quicksall contributed some examples and began the Definitions Section. Michael Fischer and Bob Barry started the Acronyms Section. Last, but not least, thanks to Ralph Weber for keeping us in line with T10 (SCSI) standardization. We would like to thank Steve Hetzler for his unwavering support and for coming up with such a good name for the protocol, Micky Rodeh, Jai Menon, Clod Barrera and Andy Bechtolsheim for helping this work happen. In addition to this document, the following must be considered in order to get a full understanding of the iSCSI specification "iSCSI Naming & Discovery"[NDT], "Bootstrapping Clients using the iSCSI Pro- tocol" [BOOT], "Securing Block Storage Protocols over IP"[SEC-IPS] documents as well as "iSCSI Requirements and Design Considerations" [ISCSI-REQ]. The "iSCSI Naming & Discovery" document is authored by: Mark Bakke (Cisco), Jim Hafner, John Hufferd, Kaladhar Voru- ganti (IBM), Marjorie Krueger (Hewlett-Packard). . The "Bootstrapping Clients using the iSCSI Protocol" document is authored by: Prasenjit Sarkar (IBM), Duncan Missimer (HP) and Costa Sapuntz- akis (Cisco). Julian Satran Expires February 2003 3 iSCSI 5-August-02 The "Bootstrapping Clients using the iSCSI Protocol" document is authored by: Bernard Aboba (Microsoft), Joshua Tseng (Nishan), Jesse Walker (Intel), Venkat Rangan (Rhapsody Networks), Franco Travos- tino (Nortel Networks). The "iSCSI Requirements and Design Considerations" document is authored by: Marjorie Krueger, Randy Haagens (HP), Costa Sapuntzakis and Mark Bakke (Cisco). We are grateful to all of them for their good work and for helping us correlate this document with the ones they produced. Change Log The following changes were made from draft-ietf-ips-iSCSI-14 to draft-ietf-ips-iSCSI-15: - Text cleanup - TargetPortalGroup is a binary string (not a numerical value) - Decimal encoding restricted - Removed BidiInitialR2T - Total text space requirement reduced to 8k - Proposed IANA registry for keys and options - New SNACK code - Added vendor specific digests, authentication methods and keys as well as a way to register them with IANA - changed the words vendor-specific into "private or public extensions" The following changes were made from draft-ietf-ips-iSCSI-13 to draft-ietf-ips-iSCSI-14: - Text cleanup - Clarification on COLD RESET - required by SAM - fixed in 9.5 recommendation on empty data (was inconsistent with R2T) - 9.4.6.2 text refers only to firstburstsize changed error code to "incorrect amount of data" - changed size to length everywhere - Reinstated I bit in text request (typo) - StatSN is retransmitted R2T should be the new value Julian Satran Expires February 2003 4 iSCSI 5-August-02 - Fixed DefaultTime2Wait and changed selection function format in Section 11 The following changes were made from draft-ietf-ips-iSCSI-12 to draft-ietf-ips-iSCSI-13: - Text cleanup - Limited decimal encoding to 64 bit integers - Logout Request reason code moved to byte 1 - Renamed MaxRecvPDULength to MaxRecvDataSegmentLength - Large Numbers allowed only if explicitly stated - CHAP is the mandatory to implement in-band authentication and SRP is optional - A negotiation answer is permitted only if all key=value pairs are complete. A flag indicates completion. - Clearing effects appendix simplified - SCSI effects are now part of [SPC3] - Made explicit a rule a bout checking when committing a nego- tiation - Added code 4 for Async Message - request negotiation The following changes were made from draft-ietf-ips-iSCSI-11 to draft-ietf-ips-iSCSI-12: - Clarify the use of A bit and DataACK at the end of data - Clarified checking to be done for abort task and removed Ref- erenced task tag from task management response - Range separator is tilde. - Fixed the paragraph numbering in the appendices. - Clarified the expected target behavior in a lost F-bit sce- nario when responding to Abort Task Set/Clear Task Set. - Added the TargetPortalGroupTag key as a Login/operational key, and its usage semantics were added to Section 4.3 Login Phase. - Clarified the language in Section 5.2.2 Allegiance Reassign- ment and Section 5.3 Usage Of Reject PDU in Recovery. - Clarified the states corresponding to full-feature phase operation in connection and session state diagrams in Chap- ter 6. - Delivering all negotiated unsolicited data are mandatory - Delivering all the data for an R2T is mandatory - Added a timeout guidance section to Chapter 8 - Added normative naming text (previously in NDT) - Clarified no duplicate parameter for login - Added a minimum required to support to text length (16k/64k) - Changed the name of TSID to TSIH to better reflect its mean- ing - Security - IPsec transport mode is MAY and authentication MUST be used when encryption is used Julian Satran Expires February 2003 5 iSCSI 5-August-02 - Added to logout a section clarifying the actions to be taken on task termination by the target - Removed CRN - Changed default time2wait & retain to better express typical ratio - Changes SCSI port element separator to comma - Async Event data format same as for SCSI response The following changes were made from draft-ietf-ips-iSCSI-10 to draft-ietf-ips-iSCSI-11: - ACA is SHOULD - New format for ISID that allows factory presets - New wording in section 9.5.5 that makes it clear that initia- tor must discard discontiguous data PDUs during reassignment. - Removed Parameter1 field definition for "drop the session" Async Message. - In state transitions chapter, added Logout timeout to the event set causing T17, and removed the "session close" event from the event set for T6. Changed "status class" to Status- Class. - Clarified that for ErrorRecoveryLevel < 2, a restart Login PDU terminates all the tasks. - Clarified the various subcases of interpretation for Time2Retain and Time2Wait in the Logout Response section. - Added a new section in the recovery chapter on connection timeout management. - The LogoutLoginMinTime and LogoutLoginMaxTime keys are respectively renamed to DefaultTime2Wait and DefaultTime2Retain, because they are used only on non-Logout events and also to better align with the notion of Time2Wait and Time2Retain that the draft already defines. - Added the new Appendix on clearing effects. - Retired the X-bit in Login PDU to make the bit position reserved. Moved the content under X-bit description to a new section 4.3.4 that describes "connection reinstatement". - Added text to section 5.2.2 that clarifies the expectations on targets during allegiance reassignment. - Minor changes in error recovery algorithms to change NextC- mdSN to CmdSN in the Session data structure. - Added a new section 4.3.5 defining the term "session rein- statement". - Added a new transition N11 to target session state diagram, to address the session reinstatement event. Enhancing the event set for N3(T) and N6(I & T) for the same event. Adding the same event to the event sets for target transitions T8, T13, T15, T16, T17, T18, and M2 (I & T). - Addressed the case of active TTTs when ABORT TASK SET/CLEAR TASK SET is in progress in section 9.5 and section 9.6. Julian Satran Expires February 2003 6 iSCSI 5-August-02 - Added a new Section 9.6.2 Task Management actions on task sets that describes the exact timeline of events on a task set task management function. - Clarified the usage of ITT for DataACK type of SNACK. - Added error code for inexistent session to login response - Changed the FIM SHOULD to should(!) - Added a TTT field for Data-In when A bit is 1 and to the cor- responding SNACK. To make it consistent changed slightly the layout of Data-IN, SCSI Response and SNACK. - Clarified the use of LUN with all PDUs holding TTT - Removed the? value from negotiations - Unified text negotiations (login, ffp and formats) in one chapter - Clarified AHSLength and DataLength for all PDUs - Clarified use of Reject - Replaced Protocol Error with Negotiation Failure in negotia- tions - Removed FFP command before login from Reject Causes - Added Invalid Request During Login to Login Errors - Added tape text - Clarified Security Text - Aligned marker negotiations with the overall negotiations and added numeric range to the negotiation forms - Changed target network architecture example in Overview - Clarified T bit use in Login Reject - Version back to 00 Julian Satran Expires February 2003 7 iSCSI 5-August-02 Status of this Memo . . . . . . . . . . . . . . . . . . . . . . . . . 2 Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Definitions and Acronyms . . . . . . . . . . . . . . . . . . . . .16 1.1 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . .16 1.2 Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . .21 1.3 Conventions used in this document . . . . . . . . . . . . . . .23 1.3.1 Word Rule . . . . . . . . . . . . . . . . . . . . . . . .23 1.3.2 Half-Word Rule . . . . . . . . . . . . . . . . . . . . . .24 1.3.3 Byte Rule . . . . . . . . . . . . . . . . . . . . . . . .24 2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25 2.1 SCSI Concepts . . . . . . . . . . . . . . . . . . . . . . . . .25 2.2 iSCSI Concepts and Functional Overview . . . . . . . . . . . .26 2.2.1 Layers and Sessions . . . . . . . . . . . . . . . . . . .26 2.2.2 Ordering and iSCSI Numbering . . . . . . . . . . . . . . .27 2.2.2.1 Command Numbering and Acknowledging . . . . . . . . .28 2.2.2.2 Response/Status Numbering and Acknowledging . . . . .31 2.2.2.3 Data Sequencing . . . . . . . . . . . . . . . . . . .32 2.2.3 iSCSI Login . . . . . . . . . . . . . . . . . . . . . . .32 2.2.4 iSCSI Full Feature Phase . . . . . . . . . . . . . . . . .34 2.2.4.1 Command Connection Allegiance . . . . . . . . . . . .34 2.2.4.2 Data Transfer Overview . . . . . . . . . . . . . . .35 2.2.4.3 Tags and integrity checks . . . . . . . . . . . . . .36 2.2.5 iSCSI Connection Termination . . . . . . . . . . . . . . .37 2.2.6 iSCSI Names . . . . . . . . . . . . . . . . . . . . . . .37 2.2.6.1 iSCSI Name Requirements . . . . . . . . . . . . . . .38 2.2.6.2 iSCSI Name Encoding . . . . . . . . . . . . . . . . .40 2.2.6.3 iSCSI Name Structure . . . . . . . . . . . . . . . .40 2.2.6.3.1 Type "iqn." (iSCSI Qualified Name) . . . . . . .41 2.2.6.3.2 Type "eui." (IEEE EUI-64 format) . . . . . . . .42 2.2.7 Persistent State . . . . . . . . . . . . . . . . . . . . .43 2.2.8 Message Synchronization and Steering . . . . . . . . . . .43 2.2.8.1 Sync/Steering and iSCSI PDU Length . . . . . . . . .45 2.3 iSCSI Session Types . . . . . . . . . . . . . . . . . . . . . .45 2.4 SCSI to iSCSI Concepts Mapping Model . . . . . . . . . . . . .45 2.4.1 iSCSI Architecture Model . . . . . . . . . . . . . . . . .46 2.4.2 SCSI Architecture Model . . . . . . . . . . . . . . . . .48 2.4.3 Consequences of the Model . . . . . . . . . . . . . . . .50 2.4.3.1 I_T Nexus State . . . . . . . . . . . . . . . . . . .51 2.5 Request/Response Summary . . . . . . . . . . . . . . . . . . .52 2.5.1 Request/Response types carrying SCSI payload . . . . . . .52 2.5.1.1 SCSI-Command . . . . . . . . . . . . . . . . . . . .52 Julian Satran Expires February 2003 8 iSCSI 5-August-02 2.5.1.2 SCSI-Response . . . . . . . . . . . . . . . . . . . .52 2.5.1.3 Task Management Function Request . . . . . . . . . .53 2.5.1.4 Task Management Function Response . . . . . . . . . .54 2.5.1.5 SCSI Data-out and SCSI Data-in . . . . . . . . . . .54 2.5.1.6 Ready To Transfer (R2T) . . . . . . . . . . . . . . .55 2.5.2 Requests/Responses carrying SCSI and iSCSI Payload . . . .55 2.5.2.1 Asynchronous Message . . . . . . . . . . . . . . . .55 2.5.3 Requests/Responses carrying iSCSI Only Payload . . . . . .55 2.5.3.1 Text Request and Text Response . . . . . . . . . . .55 2.5.3.2 Login Request and Login Response . . . . . . . . . .56 2.5.3.3 Logout Request and Response . . . . . . . . . . . . .57 2.5.3.4 SNACK Request . . . . . . . . . . . . . . . . . . .57 2.5.3.5 Reject . . . . . . . . . . . . . . . . . . . . . . .58 2.5.3.6 NOP-Out Request and NOP-In Response . . . . . . . . .58 3. SCSI Mode Parameters for iSCSI . . . . . . . . . . . . . . . . . .59 4. Login and Full Feature Phase Negotiation . . . . . . . . . . . . .60 4.1 Text Format . . . . . . . . . . . . . . . . . . . . . . . . . .61 4.2 Text Mode Negotiation . . . . . . . . . . . . . . . . . . . . .64 4.2.1 List negotiations . . . . . . . . . . . . . . . . . . . .67 4.2.2 Simple-value negotiations . . . . . . . . . . . . . . . .68 4.3 Login Phase . . . . . . . . . . . . . . . . . . . . . . . . . .69 4.3.1 Login Phase Start . . . . . . . . . . . . . . . . . . . .71 4.3.2 iSCSI Security Negotiation . . . . . . . . . . . . . . . .74 4.3.3 Operational Parameter Negotiation During the Login Phase .74 4.3.4 Connection reinstatement . . . . . . . . . . . . . . . . .75 4.3.5 Session reinstatement, closure and timeout . . . . . . . .76 4.3.5.1 Loss of Nexus notification . . . . . . . . . . . . .77 4.3.6 Session continuation and failure . . . . . . . . . . . . .77 4.4 Operational Parameter Negotiation Outside the Login Phase . . .77 5. iSCSI Error Handling and Recovery . . . . . . . . . . . . . . . .79 5.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . .79 5.1.1 Background . . . . . . . . . . . . . . . . . . . . . . . .79 5.1.2 Goals and the resulting features . . . . . . . . . . . . .79 5.1.3 State expectations . . . . . . . . . . . . . . . . . . . .80 5.2 Retry and Reassign in Recovery . . . . . . . . . . . . . . . .81 5.2.1 Usage of Retry . . . . . . . . . . . . . . . . . . . . . .81 5.2.2 Allegiance Reassignment . . . . . . . . . . . . . . . . .82 5.3 Usage Of Reject PDU in Recovery . . . . . . . . . . . . . . . .83 5.4 Connection timeout management . . . . . . . . . . . . . . . . .83 5.4.1 Timeouts on transport exception events . . . . . . . . . .84 5.4.2 Timeouts on planned decommissioning . . . . . . . . . . .84 5.5 Implicit termination of tasks . . . . . . . . . . . . . . . . .84 5.6 Format Errors . . . . . . . . . . . . . . . . . . . . . . . . .85 Julian Satran Expires February 2003 9 iSCSI 5-August-02 5.7 Digest Errors . . . . . . . . . . . . . . . . . . . . . . . . .85 5.8 Sequence Errors . . . . . . . . . . . . . . . . . . . . . . . .87 5.9 SCSI Timeouts . . . . . . . . . . . . . . . . . . . . . . . . .88 5.10 Negotiation Failures . . . . . . . . . . . . . . . . . . . . .88 5.11 Protocol Errors . . . . . . . . . . . . . . . . . . . . . . .89 5.12 Connection Failures . . . . . . . . . . . . . . . . . . . . .89 5.13 Session Errors . . . . . . . . . . . . . . . . . . . . . . . .90 5.14 Recovery Classes . . . . . . . . . . . . . . . . . . . . . . .91 5.14.1 Recovery Within-command . . . . . . . . . . . . . . . . .91 5.14.2 Recovery Within-connection . . . . . . . . . . . . . . .92 5.14.3 Connection Recovery . . . . . . . . . . . . . . . . . . .93 5.14.4 Session Recovery . . . . . . . . . . . . . . . . . . . .94 5.15 Error Recovery Hierarchy . . . . . . . . . . . . . . . . . . .94 6. State Transitions . . . . . . . . . . . . . . . . . . . . . . . .97 6.1 Standard Connection State Diagrams . . . . . . . . . . . . . .97 6.1.1 State Descriptions for Initiators and Targets . . . . . .97 6.1.2 State Transition Descriptions for Initiators and Targets .98 6.1.3 Standard Connection State Diagram for an Initiator . . . 102 6.1.4 Standard Connection State Diagram for a Target . . . . . 104 6.2 Connection Cleanup State Diagram for Initiators and Targets . 106 6.2.1 State Descriptions for Initiators and Targets . . . . . 108 6.2.2 State Transition Descriptions for Initiators and Targets 108 6.3 Session State Diagrams . . . . . . . . . . . . . . . . . . . 110 6.3.1 Session State Diagram for a Target . . . . . . . . . . . 111 6.3.2 State Descriptions for Initiators and Targets . . . . . 112 6.3.3 State Transition Descriptions for Initiators and Targets 113 7. Security Considerations . . . . . . . . . . . . . . . . . . . . 115 7.1 iSCSI Security Mechanisms . . . . . . . . . . . . . . . . . . 115 7.2 In-band Initiator-Target Authentication . . . . . . . . . . . 116 7.2.1 CHAP Considerations . . . . . . . . . . . . . . . . . . 117 7.2.2 SRP Considerations . . . . . . . . . . . . . . . . . . . 117 7.3 IPsec . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118 7.3.1 Data Integrity and Authentication . . . . . . . . . . . 118 7.3.2 Confidentiality . . . . . . . . . . . . . . . . . . . . 119 7.3.3 Policy, Security Associations and Key Management . . . . 119 8. Notes to Implementers . . . . . . . . . . . . . . . . . . . . . 121 8.1 Multiple Network Adapters . . . . . . . . . . . . . . . . . . 121 8.1.1 Conservative Reuse of ISIDs . . . . . . . . . . . . . . 121 8.1.2 iSCSI Name, ISID and TPGT Use . . . . . . . . . . . . . 122 8.2 Autosense and Auto Contingent Allegiance (ACA) . . . . . . . 124 8.3 iSCSI timeouts . . . . . . . . . . . . . . . . . . . . . . . 124 8.4 Command Retry and Cleaning Old Command Instances . . . . . . 125 8.5 Synch and Steering Layer and Performance . . . . . . . . . . 125 Julian Satran Expires February 2003 10 iSCSI 5-August-02 8.6 Considerations for State-dependent devices and long lasting SCSI operations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 8.6.1 Determining the proper ErrorRecoveryLevel . . . . . . . 126 9. iSCSI PDU Formats . . . . . . . . . . . . . . . . . . . . . . . 128 9.1 iSCSI PDU Length and Padding . . . . . . . . . . . . . . . . 128 9.2 PDU Template, Header, and Opcodes . . . . . . . . . . . . . . 128 9.2.1 Basic Header Segment (BHS) . . . . . . . . . . . . . . . 129 9.2.1.1 I . . . . . . . . . . . . . . . . . . . . . . . . . 130 9.2.1.2 Opcode . . . . . . . . . . . . . . . . . . . . . . 130 9.2.1.3 Final (F) bit . . . . . . . . . . . . . . . . . . . 131 9.2.1.4 Opcode-specific Fields . . . . . . . . . . . . . . 131 9.2.1.5 TotalAHSLength . . . . . . . . . . . . . . . . . . 131 9.2.1.6 DataSegmentLength . . . . . . . . . . . . . . . . . 132 9.2.1.7 LUN . . . . . . . . . . . . . . . . . . . . . . . . 132 9.2.1.8 Initiator Task Tag . . . . . . . . . . . . . . . . 132 9.2.2 Additional Header Segment (AHS) . . . . . . . . . . . . 132 9.2.2.1 AHSType . . . . . . . . . . . . . . . . . . . . . . 132 9.2.2.2 AHSLength . . . . . . . . . . . . . . . . . . . . . 133 9.2.2.3 Extended CDB AHS . . . . . . . . . . . . . . . . . 133 9.2.2.4 Bidirectional Expected Read-Data Length AHS . . . . 133 9.2.3 Header Digest and Data Digest . . . . . . . . . . . . . 134 9.2.4 Data Segment . . . . . . . . . . . . . . . . . . . . . . 134 9.3 SCSI Command . . . . . . . . . . . . . . . . . . . . . . . . . 135 9.3.1 Flags and Task Attributes (byte 1) . . . . . . . . . . . 135 9.3.2 CmdSN - Command Sequence Number . . . . . . . . . . . . 136 9.3.3 ExpStatSN . . . . . . . . . . . . . . . . . . . . . . . 136 9.3.4 Expected Data Transfer Length . . . . . . . . . . . . . 136 9.3.5 CDB - SCSI Command Descriptor Block . . . . . . . . . . 137 9.3.6 Data Segment - Command Data . . . . . . . . . . . . . . 137 9.4 SCSI Response . . . . . . . . . . . . . . . . . . . . . . . . 138 9.4.1 Flags (byte 1) . . . . . . . . . . . . . . . . . . . . . 138 9.4.2 Status . . . . . . . . . . . . . . . . . . . . . . . . . 139 9.4.3 Response . . . . . . . . . . . . . . . . . . . . . . . . 140 9.4.4 SNACK Tag . . . . . . . . . . . . . . . . . . . . . . . 140 9.4.5 Residual Count . . . . . . . . . . . . . . . . . . . . . 141 9.4.6 Bidirectional Read Residual Count . . . . . . . . . . . 141 9.4.7 Data Segment - Sense and Response Data Segment . . . . . 141 9.4.7.1 SenseLength . . . . . . . . . . . . . . . . . . . . 142 9.4.7.2 Sense Data . . . . . . . . . . . . . . . . . . . . 142 9.4.8 ExpDataSN . . . . . . . . . . . . . . . . . . . . . . . 143 9.4.9 StatSN - Status Sequence Number . . . . . . . . . . . . 143 9.4.10 ExpCmdSN - Next Expected CmdSN from this Initiator . . 143 9.4.11 MaxCmdSN - Maximum CmdSN from this Initiator . . . . . 143 Julian Satran Expires February 2003 11 iSCSI 5-August-02 9.5 Task Management Function Request . . . . . . . . . . . . . . . 145 9.5.1 Function . . . . . . . . . . . . . . . . . . . . . . . . 145 9.5.2 TotalAHSLength and DataSegmentLength . . . . . . . . . . 148 9.5.3 LUN . . . . . . . . . . . . . . . . . . . . . . . . . . 148 9.5.4 Referenced Task Tag . . . . . . . . . . . . . . . . . . 148 9.5.5 RefCmdSN . . . . . . . . . . . . . . . . . . . . . . . . 148 9.5.6 ExpDataSN . . . . . . . . . . . . . . . . . . . . . . . 149 9.6 Task Management Function Response . . . . . . . . . . . . . . 150 9.6.1 Response . . . . . . . . . . . . . . . . . . . . . . . . 150 9.6.2 Task Management actions on task sets . . . . . . . . . . 152 9.6.3 TotalAHSLength and DataSegmentLength . . . . . . . . . . 152 9.7 SCSI Data-out & SCSI Data-in . . . . . . . . . . . . . . . . . 153 9.7.1 F (Final) Bit . . . . . . . . . . . . . . . . . . . . . 155 9.7.2 A (Acknowledge) bit . . . . . . . . . . . . . . . . . . 155 9.7.3 Flags (byte 1) . . . . . . . . . . . . . . . . . . . . . 156 9.7.4 Target Transfer Tag . . . . . . . . . . . . . . . . . . 156 9.7.5 DataSN . . . . . . . . . . . . . . . . . . . . . . . . . 157 9.7.6 Buffer Offset . . . . . . . . . . . . . . . . . . . . . 157 9.7.7 DataSegmentLength . . . . . . . . . . . . . . . . . . . 158 9.8 Ready To Transfer (R2T) . . . . . . . . . . . . . . . . . . . 159 9.8.1 TotalAHSLength and DataSegmentLength . . . . . . . . . . 160 9.8.2 R2TSN . . . . . . . . . . . . . . . . . . . . . . . . . 161 9.8.3 StatSN . . . . . . . . . . . . . . . . . . . . . . . . . 161 9.8.4 Desired Data Transfer Length and Buffer Offset . . . . . 161 9.8.5 Target Transfer Tag . . . . . . . . . . . . . . . . . . 161 9.9 Asynchronous Message . . . . . . . . . . . . . . . . . . . . . 162 9.9.1 AsyncEvent . . . . . . . . . . . . . . . . . . . . . . . 163 9.9.2 AsyncVCode . . . . . . . . . . . . . . . . . . . . . . . 164 9.9.3 LUN . . . . . . . . . . . . . . . . . . . . . . . . . . 164 9.9.4 Sense Data and iSCSI Event Data . . . . . . . . . . . . 165 9.9.4.1 SenseLength . . . . . . . . . . . . . . . . . . . . 165 9.10 Text Request . . . . . . . . . . . . . . . . . . . . . . . . 166 9.10.1 F (Final) Bit . . . . . . . . . . . . . . . . . . . . . 167 9.10.2 C (Continue) Bit . . . . . . . . . . . . . . . . . . . 167 9.10.3 Initiator Task Tag . . . . . . . . . . . . . . . . . . 167 9.10.4 Target Transfer Tag . . . . . . . . . . . . . . . . . . 167 9.10.5 Text . . . . . . . . . . . . . . . . . . . . . . . . . 168 9.11 Text Response . . . . . . . . . . . . . . . . . . . . . . . . 170 9.11.1 F (Final) Bit . . . . . . . . . . . . . . . . . . . . . 170 9.11.2 C (Continue) Bit . . . . . . . . . . . . . . . . . . . 171 9.11.3 Initiator Task Tag . . . . . . . . . . . . . . . . . . 171 9.11.4 Target Transfer Tag . . . . . . . . . . . . . . . . . . 171 9.11.5 StatSN . . . . . . . . . . . . . . . . . . . . . . . . 172 Julian Satran Expires February 2003 12 iSCSI 5-August-02 9.11.6 Text Response Data . . . . . . . . . . . . . . . . . . 172 9.12 Login Request . . . . . . . . . . . . . . . . . . . . . . . . 173 9.12.1 T (Transit) Bit . . . . . . . . . . . . . . . . . . . . 174 9.12.2 C (Continue) Bit . . . . . . . . . . . . . . . . . . . 174 9.12.3 CSG and NSG . . . . . . . . . . . . . . . . . . . . . . 174 9.12.4 Version . . . . . . . . . . . . . . . . . . . . . . . . 174 9.12.4.1 Version-max . . . . . . . . . . . . . . . . . . . 174 9.12.4.2 Version-min . . . . . . . . . . . . . . . . . . . 175 9.12.5 ISID . . . . . . . . . . . . . . . . . . . . . . . . . 175 9.12.6 TSIH . . . . . . . . . . . . . . . . . . . . . . . . . 176 9.12.7 Connection ID - CID . . . . . . . . . . . . . . . . . . 176 9.12.8 CmdSN . . . . . . . . . . . . . . . . . . . . . . . . . 177 9.12.9 ExpStatSN . . . . . . . . . . . . . . . . . . . . . . . 177 9.12.10 Login Parameters . . . . . . . . . . . . . . . . . . . 178 9.13 Login Response . . . . . . . . . . . . . . . . . . . . . . . 179 9.13.1 Version-max . . . . . . . . . . . . . . . . . . . . . . 179 9.13.2 Version-active . . . . . . . . . . . . . . . . . . . . 180 9.13.3 TSIH . . . . . . . . . . . . . . . . . . . . . . . . . 180 9.13.4 StatSN . . . . . . . . . . . . . . . . . . . . . . . . 180 9.13.5 Status-Class and Status-Detail . . . . . . . . . . . . 180 9.13.6 T (Transit) bit . . . . . . . . . . . . . . . . . . . . 183 9.13.7 C (Continue) Bit . . . . . . . . . . . . . . . . . . . 183 9.13.8 Login Parameters . . . . . . . . . . . . . . . . . . . 184 9.14 Logout Request . . . . . . . . . . . . . . . . . . . . . . . 185 9.14.1 Reason Code . . . . . . . . . . . . . . . . . . . . . . 187 9.14.2 TotalAHSLength and DataSegmentLength . . . . . . . . . 187 9.14.3 CID . . . . . . . . . . . . . . . . . . . . . . . . . . 188 9.14.4 ExpStatSN . . . . . . . . . . . . . . . . . . . . . . . 188 9.14.5 Implicit termination of tasks . . . . . . . . . . . . . 188 9.15 Logout Response . . . . . . . . . . . . . . . . . . . . . . . 189 9.15.1 Response . . . . . . . . . . . . . . . . . . . . . . . 189 9.15.2 TotalAHSLength and DataSegmentLength . . . . . . . . . 190 9.15.3 Time2Wait . . . . . . . . . . . . . . . . . . . . . . . 190 9.15.4 Time2Retain . . . . . . . . . . . . . . . . . . . . . . 190 9.16 SNACK Request . . . . . . . . . . . . . . . . . . . . . . . 192 9.16.1 Type . . . . . . . . . . . . . . . . . . . . . . . . . 193 9.16.2 Data Acknowledgement . . . . . . . . . . . . . . . . . 193 9.16.3 Resegmentation . . . . . . . . . . . . . . . . . . . . 194 9.16.4 Initiator Task Tag . . . . . . . . . . . . . . . . . . 195 9.16.5 Target Transfer Tag or SNACK Tag . . . . . . . . . . . 195 9.16.6 BegRun . . . . . . . . . . . . . . . . . . . . . . . . 195 9.16.7 RunLength . . . . . . . . . . . . . . . . . . . . . . . 195 9.17 Reject . . . . . . . . . . . . . . . . . . . . . . . . . . . 196 Julian Satran Expires February 2003 13 iSCSI 5-August-02 9.17.1 Reason . . . . . . . . . . . . . . . . . . . . . . . . 197 9.17.2 DataSN . . . . . . . . . . . . . . . . . . . . . . . . 198 9.17.3 StatSN, ExpCmdSN and MaxCmdSN . . . . . . . . . . . . . 198 9.17.4 Complete Header of Bad PDU . . . . . . . . . . . . . . 198 9.18 NOP-Out . . . . . . . . . . . . . . . . . . . . . . . . . . . 199 9.18.1 Initiator Task Tag . . . . . . . . . . . . . . . . . . 200 9.18.2 Target Transfer Tag . . . . . . . . . . . . . . . . . . 200 9.18.3 Ping Data . . . . . . . . . . . . . . . . . . . . . . . 200 9.19 NOP-In . . . . . . . . . . . . . . . . . . . . . . . . . . . 201 9.19.1 Target Transfer Tag . . . . . . . . . . . . . . . . . . 202 9.19.2 StatSN . . . . . . . . . . . . . . . . . . . . . . . . 202 9.19.3 LUN . . . . . . . . . . . . . . . . . . . . . . . . . . 202 10. iSCSI Security Keys and Authentication Methods . . . . . . . . 203 10.1 AuthMethod . . . . . . . . . . . . . . . . . . . . . . . . . 203 10.1.1 Kerberos . . . . . . . . . . . . . . . . . . . . . . . 205 10.1.2 Simple Public-Key Mechanism (SPKM) . . . . . . . . . . 206 10.1.3 Secure Remote Password (SRP) . . . . . . . . . . . . . 207 10.1.4 Challenge Handshake Authentication Protocol (CHAP) . . 208 11. Login/Text Operational Keys . . . . . . . . . . . . . . . . . . 210 11.1 HeaderDigest and DataDigest . . . . . . . . . . . . . . . . 210 11.2 MaxConnections . . . . . . . . . . . . . . . . . . . . . . . 213 11.3 SendTargets . . . . . . . . . . . . . . . . . . . . . . . . 213 11.4 TargetName . . . . . . . . . . . . . . . . . . . . . . . . . 213 11.5 InitiatorName . . . . . . . . . . . . . . . . . . . . . . . 214 11.6 TargetAlias . . . . . . . . . . . . . . . . . . . . . . . . 214 11.7 InitiatorAlias . . . . . . . . . . . . . . . . . . . . . . . 215 11.8 TargetAddress . . . . . . . . . . . . . . . . . . . . . . . 215 11.9 TargetPortalGroupTag . . . . . . . . . . . . . . . . . . . . 216 11.10 InitialR2T . . . . . . . . . . . . . . . . . . . . . . . . 216 11.11 ImmediateData . . . . . . . . . . . . . . . . . . . . . . . 217 11.12 MaxRecvDataSegmentLength . . . . . . . . . . . . . . . . . 218 11.13 MaxBurstLength . . . . . . . . . . . . . . . . . . . . . . 219 11.14 FirstBurstLength . . . . . . . . . . . . . . . . . . . . . 219 11.15 DefaultTime2Wait . . . . . . . . . . . . . . . . . . . . . 219 11.16 DefaultTime2Retain . . . . . . . . . . . . . . . . . . . . 220 11.17 MaxOutstandingR2T . . . . . . . . . . . . . . . . . . . . . 220 11.18 DataPDUInOrder . . . . . . . . . . . . . . . . . . . . . . 221 11.19 DataSequenceInOrder . . . . . . . . . . . . . . . . . . . . 221 11.20 ErrorRecoveryLevel . . . . . . . . . . . . . . . . . . . . 222 11.21 SessionType . . . . . . . . . . . . . . . . . . . . . . . . 222 11.22 The Private or Public Extension Key Format . . . . . . . . 223 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 225 12.1 Naming Requirements . . . . . . . . . . . . . . . . . . . . 226 Julian Satran Expires February 2003 14 iSCSI 5-August-02 12.2 Mechanism Specification Requirements . . . . . . . . . . . . 226 12.3 Publication Requirements . . . . . . . . . . . . . . . . . . 227 12.4 Security Requirements . . . . . . . . . . . . . . . . . . . 227 12.5 Registration Procedure . . . . . . . . . . . . . . . . . . . 227 12.5.1 Present the KAD to the Community . . . . . . . . . . . 227 12.5.2 KAD review and IESG approval . . . . . . . . . . . . . 227 12.5.3 IANA Registration . . . . . . . . . . . . . . . . . . . 228 12.5.4 Location of Registered KAD List . . . . . . . . . . . . 228 12.6 IANA Procedures for Registering KADs . . . . . . . . . . . . 228 References and Bibliography . . . . . . . . . . . . . . . . . . . . 229 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 231 Appendix A. Sync and Steering with Fixed Interval Markers . . . . . 233 A.1 Markers At Fixed Intervals . . . . . . . . . . . . . . . . . 233 A.2 Initial Marker-less Interval . . . . . . . . . . . . . . . . 234 A.3 Negotiation . . . . . . . . . . . . . . . . . . . . . . . . 234 OFMarker, IFMarker 234 OFMarkInt, IFMarkInt 235 Appendix B. Examples . . . . . . . . . . . . . . . . . . . . . . . 237 B.2 Write Operation Example . . . . . . . . . . . . . . . . . . 238 B.3 R2TSN/DataSN use Examples . . . . . . . . . . . . . . . . . 238 B.4 CRC Examples . . . . . . . . . . . . . . . . . . . . . . . . 242 Appendix C. Login Phase Examples . . . . . . . . . . . . . . . . . 244 Appendix D. SendTargets Operation . . . . . . . . . . . . . . . . . 253 Appendix E. Algorithmic Presentation of Error Recovery Classes . . 258 E.2 Within-command Error Recovery Algorithms . . . . . . . . . . 259 Procedure Descriptions 259 Initiator Algorithms 260 Target Algorithms 262 E.3 Within-connection Recovery Algorithms . . . . . . . . . . . 265 Procedure Descriptions 265 Initiator Algorithms 266 Target Algorithms 268 E.4 Connection Recovery Algorithms . . . . . . . . . . . . . . . 269 Procedure Descriptions 269 Initiator Algorithms 269 Target Algorithms 272 Appendix F. Clearing effects of various events on targets . . . . . 275 F.1 Clearing effects on iSCSI objects . . . . . . . . . . . . . 275 F.2 Clearing effects on SCSI objects . . . . . . . . . . . . . . 280 Full Copyright Statement . . . . . . . . . . . . . . . . . . . . . 282 Julian Satran Expires February 2003 15 iSCSI 5-August-02 1. Definitions and Acronyms 1.1 Definitions - Alias: An alias string can also be associated with an iSCSI Node. The alias allows an organization to associate a user-friendly string with the iSCSI Name. However, the alias string is not a substitute for the iSCSI Name. - CID (Connection ID): Connections within a session are identified by a connection ID. It is a unique ID for this connection within the session for the initiator. It is generated by the initiator and pre- sented to the target during login requests and during logouts that close connections. - Connection: A connection is a TCP connection. Communication between the initiator and target occurs over one or more TCP connections. The TCP connections carry control messages, SCSI commands, parameters, and data within iSCSI Protocol Data Units (iSCSI PDUs). - iSCSI Device: A SCSI Device using an iSCSI service delivery sub- system. Service Delivery Subsystem is define by [SAM2] as transport mechanism for SCSI commands and responses. - iSCSI Initiator Name: The iSCSI Initiator Name specifies the world- wide unique name of the initiator. - iSCSI Initiator Node: The "initiator". - iSCSI Layer: This layer builds/receives iSCSI PDUs and relays/ receives them to/from one or more TCP connections that form an initi- ator-target "session". - iSCSI Name: The name of an iSCSI initiator or iSCSI target. - iSCSI Node: The iSCSI Node represents a single iSCSI initiator or iSCSI target. There are one or more iSCSI Nodes within a Network Entity. The iSCSI Node is accessible via one or more Network Por- tals. An iSCSI Node is identified by its iSCSI Name. The separation of the iSCSI Name from the addresses used by and for the iSCSI node allows multiple iSCSI nodes to use the same addresses, and the same iSCSI node to use multiple addresses. Julian Satran Expires February 2003 16 iSCSI 5-August-02 - iSCSI Target Name: The iSCSI Target Name specifies the worldwide unique name of the target. - iSCSI Target Node: The "target". - iSCSI Task: An iSCSI task is an iSCSI request for which a response is expected. - iSCSI Transfer Direction: The iSCSI transfer direction is defined with regard to the initiator. Outbound or outgoing transfers are transfers from the initiator to the target, while inbound or incoming transfers are from the target to the initiator. - ISID: The initiator part of the Session Identifier. It is explic- itly specified by initiator during Login. - I_T nexus: According to [SAM2], the I_T nexus is a relationship between a SCSI Initiator Port and a SCSI Target Port. For iSCSI, this relationship is a session, defined as a relationship between an iSCSI Initiator's end of the session (SCSI Initiator Port) and the iSCSI Target's Portal Group. The I_T nexus can be identified by the con- junction of the SCSI port names; that is, the I_T nexus identifier is the tuple (iSCSI Initiator Name + ',i,'+ ISID, iSCSI Target Name + ',t,'+ Portal Group Tag). - Network Entity: The Network Entity represents a device or gateway that is accessible from the IP network. A Network Entity must have one or more Network Portals, each of which can be used to gain access to the IP network by some iSCSI Nodes contained in that Network Entity. - Network Portal: The Network Portal is a component of a Network Entity that has a TCP/IP network address and that may be used by an iSCSI Node within that Network Entity for the connection(s) within one of its iSCSI sessions. A Network Portal in an initiator is iden- tified by its IP address. A Network Portal in a target is identified by its IP address and its listening TCP port. - Originator - in a negotiation or exchange the party that initiates the negotiation or exchange. Julian Satran Expires February 2003 17 iSCSI 5-August-02 - PDU (Protocol Data Unit): The initiator and target divide their communications into messages. The term "iSCSI protocol data unit" (iSCSI PDU) is used for these messages. - Portal Groups: iSCSI supports multiple connections within the same session; some implementations will have the ability to combine con- nections in a session across multiple Network Portals. A Portal Group defines a set of Network Portals within an iSCSI Node that collec- tively supports the capability of coordinating a session with connec- tions spanning these portals. Not all Network Portals within a Portal Group need participate in every session connected through that Por- tal Group. One or more Portal Groups may provide access to an iSCSI Node. Each Network Portal as utilized by a given iSCSI Node belongs to exactly one portal group within that node. - Portal Group Tag: This 16 bit bitstring identifies the Portal Group within an iSCSI Node. All Network Portals with the same portal group tag in the context of a given iSCSI Node are in the same Portal Group. - Recovery R2T: An R2T generated by a target upon detecting the loss of one or more Data-Out PDUs through one of the following means - a digest error, a sequence error, or a sequence timeout. A recovery R2T carries the next unused R2TSN, but requests part of or the entire data burst that an earlier R2T (with a lower R2TSN) had already requested - Responder: In a negotiation or exchange, the party that responds to the originator of the negotiation or exchange. - SCSI Device: This is the SAM2 term for an entity that contains one or more SCSI ports that are connected to a service delivery sub- system and supports a SCSI application protocol. For example, a SCSI Initiator Device contains one or more SCSI Initiator Ports and zero or more application clients; a Target Device contains one or more SCSI Target Ports and one or more device servers and associated logi- cal units. For iSCSI, the SCSI Device is the component within an iSCSI Node that provides the SCSI functionality. As such, there can be at most one SCSI Device within a given iSCSI Node. Access to the SCSI Device can only be achieved in an iSCSI normal operational ses- sion. The SCSI Device Name is defined to be the iSCSI Name of the node. Julian Satran Expires February 2003 18 iSCSI 5-August-02 - SCSI Layer: This builds/receives SCSI CDBs (Command Descriptor Blocks) and relays/receives them with the remaining command execute [SAM2] parameters to/from the iSCSI Layer. - Session: The group of TCP connections that link an initiator with a target form a session (loosely equivalent to a SCSI I-T nexus). TCP connections can be added and removed from a session. Across all con- nections within a session, an initiator sees one and the same target. - SSID (Session ID): A session between an iSCSI initiator and an iSCSI target is defined by a session ID that is a tuple composed of an initiator part (ISID) and a target part (Target Portal Group Tag). The ISID is explicitly specified by the initiator at session estab- lishment. The Target Portal Group Tag is implied by the initiator through the selection of the TCP endpoint at connection establish- ment. The TargetPortalGroupTag key may also be returned by the tar- get as a confirmation during session establishment. - SCSI Initiator Port: This maps to the endpoint of an iSCSI normal operational session. An iSCSI normal operational session is negoti- ated through the login process between an iSCSI initiator node and an iSCSI target node. At successful completion of this process, a SCSI Initiator Port is created within the SCSI Initiator Device. The SCSI Initiator Port Name and SCSI Initiator Port Identifier are both defined to be the iSCSI Initiator Name together with (a) a label that identifies it as an initiator port name/identifier and (b) the ISID portion of the session identifier. - SCSI Port: This is the SAM2 term for an entity in a SCSI Device that provides the SCSI functionality to interface with a service delivery subsystem. For iSCSI, the definition of the SCSI Initiator Port and the SCSI Target Port are different. - SCSI Port Name: A name made up as UTF-8 characters and includes the iSCSI Name + 'i' or 't' + ISID or Portal Group Tag. - SCSI Target Port: This maps to an iSCSI Target Portal Group. - SCSI Target Port Name and SCSI Target Port Identifier: These are both defined to be the iSCSI Target Name together with (a) a label that identifies it as a target port name/identifier and (b) the por- tal group tag. Julian Satran Expires February 2003 19 iSCSI 5-August-02 - Target Portal Group Tag: a numerical identifier (16 bit) for an iSCSI Target Portal Group - TSIH (Target Session Identifying Handle) is a target assigned tag for a session with a specific named initiator. The target generates it during session establishment and its internal format and content are not defined by this protocol except for the value 0 that is reserved and used by the initiator to indicate a new session. It is given to the target during additional connection establishment for the same session. Julian Satran Expires February 2003 20 iSCSI 5-August-02 1.2 Acronyms Acronym Definition -------------------------------------------------------------- 3DES Triple Data Encryption Standard ACA Auto Contingent Allegiance AEN Asynchronous Event Notification AES Advanced Encryption Standard AH Additional Header (not the IPsec AH!) AHS Additional Header Segment API Application Programming Interface ASC Additional Sense Code ASCII American Standard Code for Information Interchange ASCQ Additional Sense Code Qualifier BHS Basic Header Segment CBC Cipher Block Chaining CDB Command Descriptor Block CHAP Challenge Handshake Authentication Protocol CID Connection ID CO Connection Only CRC Cyclic Redundancy Check CRL Certificate Revocation List CSG Current Stage CSM Connection State Machine DES Data Encryption Standard DNS Domain Name Server DOI Domain of Interpretation ESP Encapsulating Security Payload EUI Extended Unique Identifier FFP Full Feature Phase FFPO Full Feature Phase Only Gbps Gigabits per Second HBA Host Bus Adapter HMAC Hashed Message Authentication Code IANA Internet Assigned Numbers Authority ID Identifier IDN Internationalized Domain Name IEEE Institute of Electrical & Electronics Engineers IETF Internet Engineering Task Force IKE Internet Key Exchange I/O Input - Output IO Initialize Only IP Internet Protocol Julian Satran Expires February 2003 21 iSCSI 5-August-02 IPsec Internet Protocol Security IPv4 Internet Protocol Version 4 IPv6 Internet Protocol Version 6 IQN iSCSI Qualified Name ISID Initiator Session ID ITN Initiator Task Name ITT Initiator Task Tag KRB5 Kerberos V5 LFL Lower Functional Layer LTDS Logical-Text-Data-Segment LO Leading Only LU Logical Unit LUN Logical Unit Number MAC Message Authentication Codes NA Not Applicable NIC Network Interface Card NOP No Operation NSG Next Stage OS Operating System PDU Protocol Data Unit PKI Public Key Infrastructure R2T Ready To Transfer R2TSN Ready To Transfer Sequence Number RDMA Remote Direct Memory Access SAM SCSI Architecture Model SAM2 SCSI Architecture Model - 2 SAN Storage Area Network SCSI Small Computer Systems Interface SN Sequence Number SNACK Selective Negative Acknowledgment - also Sequence Number Acknowledgement for data SPKM Simple Public-Key Mechanism SRP Secure Remote Password SSID Session ID SW Session Wide TCB Task Control Block TCP Transmission Control Protocol TPGT Target Portal Group Tag TSIH Target Session Identifying Handle TTT Target Transfer Tag UFL Upper Functional Layer ULP Upper Level Protocol URN Uniform Resource Names Julian Satran Expires February 2003 22 iSCSI 5-August-02 UTF Universal Transformation Format WG Working Group 1.3 Conventions used in this document In examples, "I->" and "T->" show iSCSI PDUs sent by the initiator and target respectively. The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC2119. iSCSI messages - PDUs - are represented by diagrams as in the follow- ing example: Byte/ 0 | 1 | 2 | 3 | / | | | | |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7| +---------------+---------------+---------------+---------------+ 0| Basic Header Segment (BHS) | +---------------+---------------+---------------+---------------+ ---------- +| | +---------------+---------------+---------------+---------------+ The diagrams include byte and bit numbering. The following representation and ordering rules are observed in this document: - Word Rule - Half-word Rule - Byte Rule 1.3.1 Word Rule A word holds 4 consecutive bytes. Whenever a word is having a numeric content it is considered an unsigned number in base 2 positional rep- resentation with the lowest numbered byte (e.g., byte 0) bit 0 repre- senting 2**31, bit 1 representing 2**30 and through Lowest numbered byte + 3 (e.g., byte 3) bit 7 representing 2**0. Julian Satran Expires February 2003 23 iSCSI 5-August-02 Decimal and hexadecimal representation of word values map this repre- sentation to decimal or hexadecimal positional notation. 1.3.2 Half-Word Rule A half-word holds 2 consecutive bytes. Whenever a half-word is hav- ing a numeric content it is considered an unsigned number in base 2 positional representation with the lowest numbered byte (e.g., byte 0) bit 0 representing 2**16, bit 1 representing 2**15 and through Lowest numbered byte + 1 (e.g., byte 1) bit 7 representing 2**0. Decimal and hexadecimal representation of half-word values map this representation to decimal or hexadecimal positional notation. 1.3.3 Byte Rule For every PDU, bytes are sent and received in increasing numbered order (network order). Whenever a byte has a numerical content it is considered an unsigned number in base 2 positional representation with bit 0 representing 2**7, bit 1 representing 2**6 and through bit 7 representing 2**0. Julian Satran Expires February 2003 24 iSCSI 5-August-02 2. Overview 2.1 SCSI Concepts The SCSI Architecture Model-2 [SAM2] describes in detail the archi- tecture of the SCSI family of I/O protocols. This section provides a brief background of the SCSI architecture and is intended to famil- iarize readers with its terminology. At the highest level, SCSI is a family of interfaces for requesting services from I/O devices, including hard drives, tape drives, CD and DVD drives, printers, and scanners. In SCSI terminology, an individ- ual I/O device is called a "logical unit" (LU). SCSI is a client-server architecture. Clients of a SCSI interface are called "initiators". Initiators issue SCSI "commands" to request ser- vice from components, logical units, of a server known as a "tar- get". The "device server" on the logical unit accepts SCSI commands and processes them. A "SCSI transport" maps the client-server SCSI protocol to a spe- cific interconnect. Initiators are one endpoint of a SCSI transport. The "target" is the other endpoint. A target can contain multiple Logical Units (LUs). Each Logical Unit has an address within a tar- get called a Logical Unit Number (LUN). A SCSI task is a SCSI command or possibly a linked set of SCSI com- mands. Some LUs support multiple pending (queued) tasks, but the queue of tasks is managed by the logical unit. The target uses an initiator provided "task tag" to distinguish between tasks. Only one command in a task can be outstanding at any given time. Each SCSI command results in an optional data phase and a required response phase. In the data phase, information can travel from the initiator to target (e.g., WRITE), target to initiator (e.g., READ), or in both directions. In the response phase, the target returns the final status of the operation, including any errors. Command Descriptor Blocks (CDB) are the data structures used to con- tain the command parameters that an initiator sends to a target. The CDB content and structure is defined by [SAM2] and device-type spe- cific SCSI standards. Julian Satran Expires February 2003 25 iSCSI 5-August-02 2.2 iSCSI Concepts and Functional Overview The iSCSI protocol is a mapping of the SCSI remote procedure invoca- tion model (see [SAM2]) over the TCP protocol. SCSI commands are car- ried by iSCSI requests and SCSI responses and status are carried by iSCSI responses. iSCSI also uses the request response mechanism for iSCSI protocol mechanisms. For the remainder of this document, the terms "initiator" and "tar- get" refer to "iSCSI initiator node" and "iSCSI target node", respec- tively (see Section 2.4.1 iSCSI Architecture Model) unless otherwise qualified. In keeping with similar protocols, the initiator and target divide their communications into messages. This document uses the term "iSCSI protocol data unit" (iSCSI PDU) for these messages. For performance reasons, iSCSI allows a "phase-collapse". A command and its associated data may be shipped together from initiator to target, and data and responses may be shipped together from targets. The iSCSI transfer direction is defined with respect to the initia- tor. Outbound or outgoing transfers are transfers from an initiator to a target, while inbound or incoming transfers are from a target to an initiator. An iSCSI task is an iSCSI request for which a response is expected. In this document "iSCSI request", "iSCSI command", request, or (unqualified) command have the same meaning. Also, unless otherwise specified, status, response, or numbered response have the same mean- ing. 2.2.1 Layers and Sessions The following conceptual layering model is used to specify initiator and target actions and how they relate to transmitted and received Protocol Data Units: a) the SCSI layer builds/receives SCSI CDBs (Command Descriptor Blocks) and passes/receives them with the remaining command exe- cute parameters ([SAM2]) to/from Julian Satran Expires February 2003 26 iSCSI 5-August-02 b) the iSCSI layer that builds/receives iSCSI PDUs and relays/ receives them to/from one or more TCP connections; the group of connections form an initiator-target "session". Communication between the initiator and target occurs over one or more TCP connections. The TCP connections carry control messages, SCSI commands, parameters, and data within iSCSI Protocol Data Units (iSCSI PDUs). The group of TCP connections that link an initiator with a target, form a session (loosely equivalent to a SCSI I-T nexus - see Section 2.4.2 SCSI Architecture Model). A session is defined by a session ID that is composed of an initiator part and a target part. TCP connections can be added and removed from a session. Connections within a session are identified by a connection ID (CID). Across all connections within a session, an initiator sees one "tar- get image". All target identifying elements, such as LUN, are the same. A target also sees one "initiator image" across all connec- tions within a session. Initiator identifying elements, such as the Initiator Task Tag, are global across the session regardless of the connection on which they are sent or received. iSCSI targets and initiators MUST support at least one TCP connec- tion and MAY support several connections in a session. For error recovery purposes, targets and initiators that support a single active connection in a session SHOULD support two connections during recovery. 2.2.2 Ordering and iSCSI Numbering iSCSI uses Command and Status numbering schemes and a Data sequenc- ing scheme. Command numbering is session-wide and is used for ordered command delivery over multiple connections. It can also be used as a mecha- nism for command flow control over a session. Status numbering is per connection and is used to enable missing sta- tus detection and recovery in the presence of transient or permanent communication errors. Data sequencing is per command or part of a command (R2T triggered sequence) and is used to detect missing data and/or R2T PDUs due to header digest errors. Julian Satran Expires February 2003 27 iSCSI 5-August-02 Typically, fields in the iSCSI PDUs communicate the Sequence Numbers between the initiator and target. During periods when traffic on a connection is unidirectional, iSCSI NOP-Out/In PDUs may be utilized to synchronize the command and status ordering counters of the tar- get and initiator. 2.2.2.1 Command Numbering and Acknowledging iSCSI performs ordered command delivery within a session. All com- mands (initiator-to-target PDUs) in transit from the initiator to the target are numbered. iSCSI considers a task to be instantiated on the target in response to every request issued by the initiator. An set of task management operations including abort and reassign (see Section 9.5 Task Manage- ment Function Request) may be performed on any iSCSI task. Some iSCSI tasks are SCSI tasks, and many SCSI activities are related to a SCSI task ([SAM2]). In all cases, the task is identified by the Initiator Task Tag for the life of the task. The command number is carried by the iSCSI PDU as CmdSN (Command- Sequence-Number). The numbering is session-wide. Outgoing iSCSI PDUs carry this number. The iSCSI initiator allocates CmdSNs with a 32-bit unsigned counter (modulo 2**32). Comparisons and arithmetic on CmdSN use Serial Number Arithmetic as defined in [RFC1982] where SERIAL_BITS = 32. Commands meant for immediate delivery are marked with an immediate delivery flag; they MUST also carry the current CmdSN. CmdSN does not advance after the commands marked for immediate delivery are sent. Command numbering starts with the first login request on the first connection of a session (the leading login on the leading connec- tion) and command numbers are incremented by 1 for every non-immedi- ate command issued afterwards. If immediate delivery is used with task management commands, these commands may reach the target before the tasks on which they are sup- posed to act. However their CmdSN is as a marker of their position in the stream of commands. The initiator and target must ensure that the task management commands act as specified by [SAM2]. For example, both commands and responses appear as if delivered in order. When- Julian Satran Expires February 2003 28 iSCSI 5-August-02 ever CmdSN for an outgoing PDU is not specified by an explicit rule, CmdSN will carry the current value of the local CmdSN variable (see later in this section). The means by which an implementation decides to mark a PDU for imme- diate delivery or by which iSCSI decides by itself to mark a PDU for immediate delivery are beyond the scope of this document. The number of commands used for immediate delivery is not limited and their delivery to execution is not acknowledged through the number- ing scheme. Immediate commands MAY be rejected by the iSCSI target layer due to lack of resources. An iSCSI target MUST be able to han- dle at least one immediate task management command and one immediate non-task-management iSCSI command per connection at any time. In this document delivery for execution means delivery to the SCSI execution engine or an iSCSI protocol specific execution engine (e.g., for text requests with public or private extension keys involving an execution component). With the exception of the com- mands marked for immediate delivery, the iSCSI target layer MUST deliver the commands for execution in the order specified by CmdSN. Commands marked for immediate delivery may be delivered by the iSCSI target layer for execution as soon as detected. iSCSI may avoid delivering some commands to the SCSI target layer if required by a prior SCSI or iSCSI action (e.g., CLEAR TASK SET Task Management request received before all the commands on which it was supposed to act). On any connection, the iSCSI initiator MUST send the commands in increasing order of CmdSN, except for commands that are retransmit- ted due to digest error recovery and connection recovery. For the numbering mechanism the initiator and target maintain the following three variables for each session: - CmdSN - the current command Sequence Number, advanced by 1 on each command shipped except for commands marked for imme- diate delivery. CmdSN always contains the number to be assigned to the next Command PDU. - ExpCmdSN - the next expected command by the target. The tar- get acknowledges all commands up to, but not including, this number. The initiator treats all commands with CmdSN less than ExpCmdSN as acknowledged. The target iSCSI layer sets the ExpCmdSN to the largest non-immediate CmdSN that it can Julian Satran Expires February 2003 29 iSCSI 5-August-02 deliver for execution plus 1 (no holes in the CmdSN sequence). - MaxCmdSN - the maximum number to be shipped. The queuing capacity of the receiving iSCSI layer is MaxCmdSN - ExpCmdSN + 1. The initiator's ExpCmdSN and MaxCmdSN are derived from target-to-ini- tiator PDU fields. Comparisons and arithmetic on ExpCmdSN and MaxC- mdSN MUST use Serial Number Arithmetic as defined in [RFC1982] where SERIAL_BITS = 32. The target MUST NOT transmit a MaxCmdSN that is less than ExpCmdSN-1. For non-immediate commands, the CmdSN field can take any value from ExpCmdSN to MaxCmdSN inclusive. The target MUST silently ignore any non-immediate command outside of this range or non-immediate dupli- cates within the range. Note that the CmdSN carried by immediate com- mands may lie outside the ExpCmdSN to MaxCmdSN range (e.g., if the initiator has previously sent a non-immediate command carrying the CmdSN equal to MaxCmdSN - i.e., target window is closed). For group task management commands issued as immediate commands CmdSN indi- cates the scope of the group action (e.g., on ABORT TASK SET - what commands get aborted). MaxCmdSN and ExpCmdSN fields are processed by the initiator as fol- lows: -If the PDU MaxCmdSN is less than the PDU ExpCmdSN-1 (in Serial Arithmetic Sense), they are both ignored. -If the PDU MaxCmdSN is greater than the local MaxCmdSN (in Serial Arithmetic Sense) it updates the local MaxCmdSN; oth- erwise, it is ignored. -If the PDU ExpCmdSN is greater than the local ExpCmdSN (in Serial Arithmetic Sense) it updates the local ExpCmdSN; oth- erwise, it is ignored. This sequence is required because updates may arrive out of order (e.g., the updates are sent on different TCP connections). iSCSI initiators and targets MUST support the command numbering scheme. A numbered iSCSI request will not change its allocated CmdSN, regard- less of the number of times and circumstances in which it is reis- sued (see Section 5.2.1 Usage of Retry). At the target CmdSN is relevant only while the command has not created any state related to Julian Satran Expires February 2003 30 iSCSI 5-August-02 its execution (execution state); afterwards, CmdSN becomes irrele- vant. Testing for the execution state (represented by identifying the Initiator Task Tag) MUST precede any other action at the target, and is followed by ordering and delivery if no execution state is found, or delivery if an execution state is found. If an initiator issues a command retry for a command with CmdSN R on a connection when the session CmdSN value is Q, it MUST NOT advance the CmdSN past R + 2**31 -1 unless the connection is no longer opera- tional (has returned to the FREE state - see Section 6.1.3 Standard Connection State Diagram for an Initiator), or the connection has been reinstated (see Section 4.3.4 Connection reinstatement), or a non-immediate command with CmdSN equal or greater than Q was issued subsequent to the command retry on the same connection and the recep- tion of that command is acknowledged by the target (see Section 8.4 Command Retry and Cleaning Old Command Instances). A target MUST NOT issue a command response or DATA-In PDU with sta- tus before acknowledging the command. However, the acknowledgement can be included in the response or Data-in PDU itself. 2.2.2.2 Response/Status Numbering and Acknowledging Responses in transit from the target to the initiator are numbered. The StatSN (Status Sequence Number) is used for this purpose. StatSN is a counter maintained per connection. ExpStatSN is used by the ini- tiator to acknowledge status. The status sequence number space is 32- bit unsigned-integers and the arithmetic operations are the regular mod(2**32) arithmetic. Status numbering starts with the Login response to the first Login request of the connection. The Login response includes an initial value for status numbering (any initial value is valid). To enable command recovery, the target MAY maintain enough state information for data and status recovery after a connection failure. A target doing so can safely discard all the state information main- tained for recovery of a command after the delivery of the status for the command (numbered StatSN) is acknowledged through ExpStatSN. A large absolute difference between StatSN and ExpStatSN may indi- cate a failed connection. Initiators MUST undertake recovery actions Julian Satran Expires February 2003 31 iSCSI 5-August-02 if the difference is greater than an implementation defined constant that MUST NOT exceed 2**31-1. Initiators and Targets MUST support the response-numbering scheme. 2.2.2.3 Data Sequencing Data and R2T PDUs, transferred as part of some command execution, MUST be sequenced. The DataSN field is used for data sequencing. For input (read) data PDUs, DataSN starts with 0 for the first data PDU of an input command and advances by 1 for each subsequent data PDU. For output data PDUs, DataSN starts with 0 for the first data PDU of a sequence (the initial unsolicited sequence or any data PDU sequence issued to satisfy an R2T) and advances by 1 for each subsequent data PDU. R2Ts are also sequenced per command. For example, the first R2T has an R2TSN of 0 and advances by 1 for each subsequent R2T. For bidirectional commands, the target uses the DataSN/R2TSN to sequence Data-In and R2T PDUs in one continuous sequence (undifferentiated). Unlike command and status, data PDUs and R2Ts are not acknowledged by a field in regular outgoing PDUs. Data-In PDUs can be acknowledged on demand by a special form of the SNACK PDU. Data and R2T PDUs are implicitly acknowledged by status for the command. The DataSN/R2TSN field enables the initiator to detect missing data or R2T PDUs. For any read or bidirectional command, a target MUST issue less than 2**32 combined R2T and Data-In PDUs. Any output data sequence MUST contain less than 2**32 Data-Out PDUs. 2.2.3 iSCSI Login The purpose of the iSCSI login is to enable a TCP connection for iSCSI use, authenticate the parties, negotiate the session's parame- ters and mark the connection as belonging to an iSCSI session. A session is used to identify all the connections with a given initi- ator that belong to the same I_T nexus to a target. (See Section 2.4.2 SCSI Architecture Model for more details on how a session relates to an I_T nexus). The targets listen on a well-known TCP port or other TCP port for incoming connections. The initiator begins the login process by con- necting to one of these TCP ports. Julian Satran Expires February 2003 32 iSCSI 5-August-02 As part of the login process, the initiator and target MAY wish to authenticate each other and set a security association protocol for the session. This can occur in many different ways and is subject to negotiation. In order to protect the TCP connection, an IPsec security associa- tion MAY be established before the Login request. Using IPsec secu- rity for iSCSI is specified in Chapter 7 and in [SEC-IPS]. The iSCSI Login Phase is carried through Login requests and responses. Once suitable authentication has occurred and operational parameters have been set, the initiator may start to send SCSI com- mands. Security policy for whether and by what means a target chooses to authorize an initiator is beyond the scope of this document. A more detailed description of the Login Phase can be found in Chapter 4. The login PDU includes the ISID part of the session ID (SSID). The target portal group servicing the login is implied by the selection of the connection endpoint. For a new session, the TSIH is zero. As part of the response, the target generates a TSIH. During session establishment, the target identifies the SCSI initia- tor port (the "I" in the "I_T nexus") through the value pair (Initia- torName, ISID) (InitiatorName is described later in this section). Any persistent state (e.g., persistent reservations) on the target that is associated with a SCSI initiator port is identified based on this value pair. Any state associated with the SCSI target port (the "T" in the "I_T nexus") is identified externally by the TargetName and portal group tag (see Section 2.4.1 iSCSI Architecture Model). As ISID is used to identify a persistent state, it is subject to reuse restrictions (see Section 2.4.3 Consequences of the Model). Before the Full Feature Phase is established, only Login Request and Login Response PDUs are allowed. Login requests and responses MUST be used exclusively during Login. On any connection the login phase MUST immediately follow TCP connection establishment and a subsequent Login Phase MUST NOT occur before tearing down a connection. A target receiving any PDU except a Login request before the Login phase is started MUST immediately terminate the connection on which the PDU was received. Once the Login phase has started, if the tar- get receives any PDU except a Login request, it MUST send a Login Julian Satran Expires February 2003 33 iSCSI 5-August-02 reject (with Status "invalid during login") and then disconnect; if the initiator receives any PDU except a Login response, it MUST imme- diately terminate the connection. 2.2.4 iSCSI Full Feature Phase Once the initiator is authorized to do so, the iSCSI session is in the iSCSI Full Feature Phase. A session is in Full Feature Phase after successfully finishing the Login Phase on the first (leading) connection of a session. A connection is in Full Feature Phase if the session is in Full Feature Phase and the connection login has com- pleted successfully. An iSCSI connection is not in Full Feature Phase a) when it does not have an established transport connection, OR b) when it has a valid transport connection, but a successful login was not performed or the connection is currently logged out. In a normal Full Feature Phase, the initiator may send SCSI commands and data to the various LUs on the target by encapsulating them in iSCSI PDUs that go over the established iSCSI session. 2.2.4.1 Command Connection Allegiance For any iSCSI request issued over a TCP connection, the correspond- ing response and/or other related PDU(s) MUST be sent over the same connection. We call this "connection allegiance". If the original connection fails before the command is completed, the connection allegiance of the command may be explicitly reassigned to a differ- ent transport connection as described in detail in Section 5.2 Retry and Reassign in Recovery. Thus, if an initiator issues a READ command, the target MUST send the requested data, if any, followed by the status to the initiator over the same TCP connection that was used to deliver the SCSI command. If an initiator issues a WRITE command, the initiator MUST send the data, if any, for that command over the same TCP connection that was used to deliver the SCSI command. The target MUST return Ready To Transfer (R2T), if any, and the status over the same TCP connection that was used to deliver the SCSI command. Retransmission requests (SNACK PDUs) and the data and status that they generate MUST also use the same connection. Julian Satran Expires February 2003 34 iSCSI 5-August-02 However, consecutive commands that are part of a SCSI linked command- chain task (see [SAM2]) MAY use different connections. Connection allegiance is strictly per-command and not per-task. During the iSCSI Full Feature Phase, the initiator and target MAY interleave unre- lated SCSI commands, their SCSI Data, and responses over the session. 2.2.4.2 Data Transfer Overview Outgoing SCSI data (initiator to target user data or command parame- ters) is sent as either solicited data or unsolicited data. Solic- ited data are sent in response to R2T PDUs. Unsolicited data can be sent as part of an iSCSI command PDU ("immediate data") or in sepa- rate iSCSI data PDUs. Immediate data are assumed to originate at offset 0 in the initiator SCSI write-buffer (outgoing data buffer). All other Data PDUs have the buffer offset set explicitly in the PDU header. An initiator may send unsolicited data up to FirstBurstLength as immediate (up to the negotiated maximum PDU length), in a separate PDU sequence or both. All subsequent data MUST be solicited. The max- imum length of an individual data PDU or the immediate-part of the first unsolicited burst MAY be negotiated at login. Targets receive data in either solicited (R2T) data mode or unsolic- ited (non-R2T) data mode. The maximum amount of unsolicited data that can be sent with a command is negotiated at login through the First- BurstLength key. A target MAY separately enable immediate data (through the ImmediateData key) without enabling the more general (separate data PDUs) form of unsolicited data (through the InitialR2T key). Unsolicited data on write are meant to reduce the effect of latency on throughput (no R2T is needed to start sending data). In addition, immediate data is meant to reduce the protocol overhead (both band- width and execution time). An iSCSI initiator MAY choose to send no unsolicited data, only imme- diate data or FirstBurstLength bytes of unsolicited data with a com- mand. If any non-immediate unsolicited data is sent, the total unsolicited data MUST be either FirstBurstLength or all the data if the total amount is less than the FirstBurstLength. Julian Satran Expires February 2003 35 iSCSI 5-August-02 It is considered an error for an initiator to send unsolicited data PDUs to a target that operates in R2T mode (only solicited data are allowed). It is also an error for an initiator to send more data, whether immediate or as separate PDUs, than FirstBurstLength. An initiator MUST honor an R2T data request for a valid outstanding command (i.e., carrying a valid Initiator Task Tag) and deliver all the requested data provided the command is supposed to deliver outgo- ing data and the R2T specifies data within the command bounds. The initiator actions on receiving an R2T request that specifies data all or part outside the command bounds is unspecified. A target SHOULD NOT silently discard data and then request retrans- mission through R2T. Initiators SHOULD NOT keep track of the data transferred to or from the target (scoreboarding). SCSI targets per- form residual count calculation to tell how much data was actually transferred to or from the device by a command; this may differ from the amount the initiator sent and/or received for reasons such as retransmissions and errors. Read or bidirectional command implicitly solicit the transmission of the entire amount of data covered by the command. SCSI data packets are matched to their corresponding SCSI commands by using tags specified in the protocol. iSCSI initiators and targets MUST also enforce some ordering rules. When unsolicited data is used the order of the unsolicited data on each connection MUST match the order in which the commands on that connection are sent. Command and unsolicited data PDUs may be inter- leaved on a single connection as long as the ordering requirements of each are maintained (e.g., command N+1 MAY be sent before the unso- licited Data-Out PDUs for command N, but the unsolicited Data-Out PDUs for command N MUST precede the unsolicited Data-Out PDUs of com- mand N+1). A target that receives data out of order MAY terminate the session. 2.2.4.3 Tags and integrity checks Initiator tags for pending commands are unique initiator-wide for a session. Target tags are not strictly specified by the protocol. It is assumed that target tags are used by the target to tag (alone or in combination with the LUN) the solicited data. Target tags are gen- erated by the target and "echoed" by the initiator. These mechanisms are designed to accomplish efficient data delivery along a large degree of control over the data flow. Julian Satran Expires February 2003 36 iSCSI 5-August-02 As the Initiator Task Tag is used to identify a task during its exe- cution the iSCSI initiator and target MUST verify that all other fields used in task related PDUs have values are consistent with the values used at task instantiation based on Initiator Task Tag (e.g., the LUN used in an R2T PDU MUST be the same as the one used in the SCSI command PDU used to instantiate the task). Using inconsistent field values is considered a protocol error. 2.2.5 iSCSI Connection Termination An iSCSI connection may be terminated by use of a transport connec- tion shutdown, or a transport reset. Transport reset is assumed to be an exceptional event. Graceful TCP connection shutdowns are done by sending TCP FINs. A graceful transport connection shutdown SHOULD be initiated by either party only when the connection is not in iSCSI Full Feature Phase. A target MAY terminate a Full Feature Phase connection on internal exception events, but it SHOULD announce the fact through an Asyn- chronous Message PDU. Connection termination with outstanding com- mands may require recovery actions. If a connection is terminated while in Full Feature Phase, connec- tion cleanup (section 6) is required prior to recovery. By doing con- nection cleanup before starting recovery, the initiator and target will avoid receiving stale PDUs after recovery. 2.2.6 iSCSI Names Both targets and initiators require names for the purpose of identi- fication. In addition names enable iSCSI storage resources to be man- aged regardless of location (address). An iSCSI node name is also the SCSI device name of an iSCSI device. The iSCSI name of a SCSI device is the principal object used in authentication of targets to initia- tors and initiators to targets. This name is also used to identify and manage iSCSI storage resources. iSCSI names must be unique within the operation domain of the end user. However, because the operation domain of an IP network is potentially worldwide, the iSCSI name formats are architected to be worldwide unique. To assist naming authorities in the construction of worldwide unique names, iSCSI provides two name formats for differ- ent types of naming authorities. Julian Satran Expires February 2003 37 iSCSI 5-August-02 iSCSI names are associated with iSCSI nodes, not iSCSI network adapter cards, to ensure the replacement of network adapter cards does not require reconfiguration of all SCSI and iSCSI resource allo- cation information. Some SCSI commands require that protocol-specific identifiers be com- municated within SCSI CDBs. See Section 2.4.2 SCSI Architecture Model for the definition of the SCSI port name/identifier for iSCSI ports. An initiator may discover the iSCSI Target Names to which it has access, along with their addresses, using the SendTargets text request, or other techniques discussed in [NDT]. 2.2.6.1 iSCSI Name Requirements Each iSCSI node, whether an initiator or target, MUST have an iSCSI name. Initiators and targets MUST support the receipt of iSCSI names of up to the maximum length of 223 bytes. The initiator MUST present both its iSCSI Initiator Name and the iSCSI Target Name to which it wishes to connect in the first login request of a new session or connection. The only exception is if a discovery session (see Section 2.3 iSCSI Session Types) is to be established; the iSCSI Initiator Name is still required, but the iSCSI Target Name MAY be omitted. iSCSI names MUST adhere to the following requirements: a) iSCSI names must be globally unique. No two initiators or tar- gets should have the same name. b) iSCSI names must be permanent. An iSCSI initiator node or tar- get node has the same name for its lifetime. c) iSCSI names do not imply a location or address. An iSCSI ini- tiator or target can move, or have multiple addresses. A change of address does not imply a change of name. d) iSCSI names must not rely on a central name broker; the nam- ing authority must be distributed. e) iSCSI names must support integration with existing unique nam- ing schemes. Julian Satran Expires February 2003 38 iSCSI 5-August-02 f) iSCSI names must rely on existing naming authorities. iSCSI does not have to create its own naming authority. The encoding of an iSCSI name also has some requirements: a) iSCSI names MUST have a single encoding method when transmit- ted over various protocols. b) iSCSI names MUST be relatively simple to compare. The algo- rithm for comparing two iSCSI names for equivalence MUST not rely on any external server. c) iSCSI names MUST be composed of displayable characters only. iSCSI names should be kept as simple as possible. They MUST pro- vide for the use of international character sets, and MUST not be case sensitive. Whitespace characters MUST NOT be used. d) iSCSI names MUST be transport-friendly. They MUST be trans- ported using both binary and ASCII-based protocols. An iSCSI name really names a logical software entity, and is not tied to a port or other hardware that can be changed. For instance, an initiator name should name the iSCSI initiator node, not a particu- lar NIC or HBA. When multiple NICs are used, they should generally all present the same iSCSI initiator name to the targets, because they are just paths to the same SCSI layer. In most operating sys- tems, the named entity is the operating system image. A target name should similarly not be tied to hardware interfaces that can be changed. A target name should identify the logical tar- get, and must be the same for the target regardless of the physical portion being addressed. This assists iSCSI initiators in determin- ing that two targets it has discovered are really two paths to the same target. The iSCSI name is designed to fulfill the functional requirements for Uniform Resource Names (URN) [RFC1737]. For example, it is required that the name have a global scope, independent of address or loca- tion, and that it be persistent and globally unique. Names must be extensible, and scale with the use of naming authorities. The encod- ing of the name should be readable by a human, as well as be machine- readable. See [RFC1737] for further requirements. Julian Satran Expires February 2003 39 iSCSI 5-August-02 2.2.6.2 iSCSI Name Encoding An iSCSI name MUST be a UTF-8 encoding of a string of Unicode charac- ters, with the following properties: - it is in Normalization Form C (see "Unicode Normalization Forms" [UNICODE]) - it contains only the following characters: - dash ('-'=U+002d) - dot ('.'=U+002e) - colon (':'=U+003a) - Any character allowed by the output of the iSCSI stringprep template (described in [STPREP-iSCSI]) - when encoded in UTF-8, it is no larger than 223 bytes The stringprep process is described in [STPREP]; iSCSI's use of the stringprep process is described in [STPREP-iSCSI]. Stringprep is a method designed by the Internationalized Domain Name (IDN) working group to translate human-typed strings into a format that can be com- pared as opaque strings. Strings must not include punctuation, spac- ing, diacritical marks, or other characters that could get in the way of readability. The stringprep process also converts strings into equivalent strings of lower-case characters. Note that in most cases, the stringprep process does not need to be implemented if the names are generated using only lower-case (any character set) alpha-numeric characters. Once iSCSI names encoded in UTF-8 are "normalized" (there is one and only one representation for each possible name), they may be safely compared byte-for-byte. 2.2.6.3 iSCSI Name Structure An iSCSI name consists of two parts - a type designator followed by a unique name string. The iSCSI name does not define any new naming authorities. Instead, it supports two existing ways of designating naming authorities: an iSCSI-Qualified Name, using domain names to identify a naming author- ity, and the EUI format, where the IEEE Registration Authority assists in the formation of worldwide unique names (EUI-64 format). Julian Satran Expires February 2003 40 iSCSI 5-August-02 The type designator strings currently defined are: iqn. - iSCSI Qualified name eui. - Remainder of the string is an IEEE EUI-64 identifier, in ASCII-encoded hexadecimal. As these two naming authority designators will suffice in nearly every case for both software and hardware-based entities, the cre- ation of additional type designators is prohibited. One of these two type strings MUST be used when constructing an iSCSI name; any type string not listed here is not allowed, as they cannot be guaranteed to be unique. 2.2.6.3.1 Type "iqn." (iSCSI Qualified Name) This iSCSI name type can be used by any organization which owns a domain name. This naming format is useful when an end user or ser- vice provider wishes to assign iSCSI names for targets and/or initia- tors. To generate names of this type, the person or organization generat- ing the name must own a registered domain name. This domain name does not have to be active, and does not have to resolve to an address; it just needs to be reserved to prevent others from generating iSCSI names using the same domain name. Because a domain name can expire, be acquired by another entity, and might be used to generate iSCSI names by both owners, the domain name must be additionally qualified by a date during which the naming authority owned the domain name. A date code is provided as part of the "iqn." format for this reason. The iSCSI qualified name string consists of: - The string "iqn.", used to distinguish these names from "eui." formatted names. - A date code, in yyyy-mm format. This date MUST be a date dur- ing which the naming authority owned the domain name used in this format, and SHOULD be the first month in which the domain name was owned by this naming authority at 00:01 GMT of the first day of the month. This date code uses the Grego- rian calendar. All four digits in the year must be present. Both digits of the month must be present, with January == "01" and December == "12". The dash must be included. Julian Satran Expires February 2003 41 iSCSI 5-August-02 - A dot "." - The reversed domain name of the naming authority (person or organization) creating this iSCSI name. - An optional, colon (:) prefixed string, within the character set and length boundaries, that the owner of the domain name deems appropriate. This may contain product types, serial numbers, host identifiers, software keys (e.g, it may include colons to separate organization boundaries). Except for the colon prefix everything after the reversed domain name can be assigned as desired by the owner of the domain name. It is the responsibility of the entity that is the naming author- ity to ensure that the iSCSI names it assigns are worldwide unique. For example, "ACME Storage Arrays, Inc.", might own the domain name "acme.com". The following are examples of iSCSI qualified names that might be generated by "ACME Storage Arrays, Inc." Naming String defined by Type Date Auth "acme.com" naming authority +--++-----+ +------+ +--------------------------------+ | || | | | | | iqn.2001-04.com.acme:storage:diskarrays-sn-a8675309 iqn.2001-04.com.acme iqn.2001-04.com.acme:storage.tape.sys1.xyz iqn.2001-04.com.acme:storage.tape.sys1.xyz 2.2.6.3.2 Type "eui." (IEEE EUI-64 format) The IEEE Registration Authority provides a service for assigning glo- bally unique identifiers [EUI]. The EUI-64 format is used to build a global identifier in other network protocols - e.g, Fibre Channel defines a method of encoding it into a WorldWideName. See http:// standards.ieee.org/regauth/oui/index.shtml - for more information on registering for EUI identifiers. The format is "eui." followed by an EUI-64 identifier (16 ASCII- encoded hexadecimal digits). Example iSCSI name: Type EUI-64 identifier (ASCII-encoded hexadecimal) +--++--------------+ | || | Julian Satran Expires February 2003 42 iSCSI 5-August-02 eui.02004567A425678D The IEEE EUI-64 iSCSI name format might be used when a manufacturer is already registered with the IEEE Registration Authority and uses EUI-64 formatted worldwide unique names for its products. More examples of name construction are discussed in [NDT]. 2.2.7 Persistent State iSCSI does not require any persistent state maintenance across ses- sions. However, in some cases, SCSI requires persistent identifica- tion of the SCSI initiator port name (See Section 2.4.2 SCSI Architecture Model and Section 2.4.3 Consequences of the Model). iSCSI sessions do not persist through power cycles and boot opera- tions. All iSCSI session and connection parameters are re-initialized on session and connection creation. Commands persist beyond connection termination if the session per- sists and command recovery within the session is supported. However, when a connection is dropped, command execution, as perceived by iSCSI (i.e., involving iSCSI protocol exchanges for the affected task), is suspended until a new allegiance is established by the 'task reassign' task management function. (See Section 9.5 Task Man- agement Function Request.) 2.2.8 Message Synchronization and Steering iSCSI presents a mapping of the SCSI protocol onto TCP. This encapsu- lation is accomplished by sending iSCSI PDUs of varying lengths. Unfortunately, TCP does not have a built-in mechanism for signaling message boundaries at the TCP layer. iSCSI overcomes this obstacle by placing the message length in the iSCSI message header. This serves to delineate the end of the current message as well as the beginning of the next message. In situations where IP packets are delivered in order from the net- work, iSCSI message framing is not an issue and messages are pro- cessed one after the other. In the presence of IP packet reordering, (i.e., frames being dropped) legacy TCP implementations store the Julian Satran Expires February 2003 43 iSCSI 5-August-02 "out of order" TCP segments in temporary buffers until the missing TCP segments arrive, upon which the data must be copied to the appli- cation buffers. In iSCSI, it is desirable to steer the SCSI data within these out of order TCP segments into the pre-allocated SCSI buffers rather than store them in temporary buffers. This decreases the need for dedicated reassembly buffers as well as the latency and bandwidth related to extra copies. Relying solely on the "message length" information from the iSCSI message header may make it impossible to find iSCSI message bound- aries in subsequent TCP segments due to the loss of a TCP segment that contains the iSCSI message length. The missing TCP segment(s) must be received before any of the following segments can be steered to the correct SCSI buffers (due to the inability to determine the iSCSI message boundaries). Because these segments cannot be steered to the correct location, they must be saved in temporary buffers that must then be copied to the SCSI buffers. Different schemes can be used to recover synchronization. To make these schemes work, iSCSI implementations have to make sure that the appropriate protocol layers are provided with enough information to implement a synchronization and/or data steering mechanism. One of these schemes is detailed in Appendix A. - Sync and Steering with Fixed Interval Markers -. The Fixed Interval Markers (FIM) scheme works by inserting in the payload stream at fixed intervals markers that contain the offset to the start of the next iSCSI PDU. Under normal circumstances (no PDU loss or data reception out of order), iSCSI data steering can be accomplished by using the identi- fying tag and the data offset fields in the iSCSI header as well as the TCP sequence number from the TCP header. The identifying tag helps associate the PDU with a SCSI buffer address while the data offset and TCP sequence number are used to determine the offset within the buffer. When the part of the TCP data stream containing an iSCSI PDU header is delayed or lost markers may be used to minimize the damage as fol- lows: - markers indicate where the next iSCSI PDU starts and enable continued processing when iSCSI headers have to be dropped Julian Satran Expires February 2003 44 iSCSI 5-August-02 due to data errors discovered at iSCSI level (e.g., iSCSI header CRC errors) - markers help minimize the amount of data that has to be kept by the TCP/iSCSI layer while waiting for a late TCP packet arrival or recovery as they may help find later iSCSI PDU headers and use the information contained in those to steer data to SCSI buffers 2.2.8.1 Sync/Steering and iSCSI PDU Length When a large iSCSI message is sent, the TCP segment(s) that contain the iSCSI header may be lost. The remaining TCP segment(s) up to the next iSCSI message must be buffered (in temporary buffers) because the iSCSI header that indicates to which SCSI buffers the data are to be steered was lost. To minimize the amount of buffering, it is rec- ommended that the iSCSI PDU length be restricted to a small value (perhaps a few TCP segments in length). During login, each end of the iSCSI session specifies the maximum iSCSI PDU length it will accept. 2.3 iSCSI Session Types iSCSI defines two types of sessions: a) Normal operational session - an unrestricted session. b) Discovery-session - a session opened only for target discov- ery; the target MUST ONLY accept text requests with the SendTar- gets key and a logout request with reason "close the session". All other requests MUST be rejected. The session type is defined during login with key=value parameter in the login command. 2.4 SCSI to iSCSI Concepts Mapping Model The following diagram shows an example of how multiple iSCSI Nodes (targets in this case) can coexist within the same Network Entity and can share Network Portals (IP addresses and TCP ports). Other more complex configurations are also possible. See Section 2.4.1 iSCSI Architecture Model for detailed descriptions of the components of these diagrams. Julian Satran Expires February 2003 45 iSCSI 5-August-02 +-----------------------------------+ | Network Entity (iSCSI Client) | | | | +-------------+ | | | iSCSI Node | | | | (Initiator) | | | +-------------+ | | | | | | +--------------+ +--------------+ | | |Network Portal| |Network Portal| | | | 10.1.30.4 | | 10.1.40.6 | | +-+--------------+-+--------------+-+ | | | IP Networks | | | +-+--------------+-+--------------+-+ | |Network Portal| |Network Portal| | | | 10.1.30.21 | | 10.1.40.3 | | | | TCP Port 3260| | TCP Port 3260| | | +--------------+ +--------------+ | | | | | | ----------------- | | | | | | +-------------+ +--------------+ | | | iSCSI Node | | iSCSI Node | | | | (Target) | | (Target) | | | +-------------+ +--------------+ | | | | Network Entity (iSCSI Server) | +-----------------------------------+ 2.4.1 iSCSI Architecture Model This section describes the part of the iSCSI architecture model that has the most bearing on the relationship between iSCSI and the SCSI Architecture Model. a) Network Entity - represents a device or gateway that is acces- sible from the IP network. A Network Entity must have one or more Network Portals (see item d), each of which can be used by some iSCSI Nodes (see item (b)) contained in that Network Entity to gain access to the IP network. Julian Satran Expires February 2003 46 iSCSI 5-August-02 b) iSCSI Node - represents a single iSCSI initiator or iSCSI tar- get. There are one or more iSCSI Nodes within a Network Entity. The iSCSI Node is accessible via one or more Network Portals (see item d). An iSCSI Node is identified by its iSCSI Name (see Sec- tion 2.2.6 iSCSI Names and Chapter 11). The separation of the iSCSI Name from the addresses used by and for the iSCSI node allows multiple iSCSI nodes to use the same addresses, and the same iSCSI node to use multiple addresses. c) An alias string may also be associated with an iSCSI Node. The alias allows an organization to associate a user friendly string with the iSCSI Name. However, the alias string is not a substi- tute for the iSCSI Name. d) Network Portal - a component of a Network Entity that has a TCP/IP network address and that may be used by an iSCSI Node within that Network Entity for the connection(s) within one of its iSCSI sessions. In an initiator, it is identified by its IP address. In a target, it is identified by its IP address and its listening TCP port. e) Portal Groups - iSCSI supports multiple connections within the same session; some implementations will have the ability to com- bine connections in a session across multiple Network Portals. A Portal Group defines a set of Network Portals within an iSCSI Node that collectively supports the capability of coordinating a ses- sion with connections that span these portals. Not all Network Portals within a Portal Group need to participate in every ses- sion connected through that Portal Group. One or more Portal Groups may provide access to an iSCSI Node. Each Network Portal, as utilized by a given iSCSI Node, belongs to exactly one portal group within that node. Portal Groups are identified within an iSCSI Node by a portal group tag, a simple unsigned-integer between 1 and 65535 (see Section 11.3 SendTargets). All Network Portals with the same portal group tag in the context of a given iSCSI Node are in the same Portal Group. Both iSCSI Initiators and iSCSI Targets have portal groups, though only the iSCSI Target Portal Groups are used directly in the iSCSI protocol (e.g., in SendTargets). See Section Section 8.1.1 Conser- vative Reuse of ISIDs for references to the Initiator Portal Groups. Julian Satran Expires February 2003 47 iSCSI 5-August-02 f) Portals within a Portal Group should support similar session parameters - as they may participate in a common session The following diagram shows an example of one such configuration on a target and how a session that shares Network Portals within a Portal Group may be established. ----------------------------IP Network--------------------- | | | +----|---------------|-----+ +----|---------+ | +---------+ +---------+ | | +---------+ | | | Network | | Network | | | | Network | | | | Portal | | Portal | | | | Portal | | | +--|------+ +---------+ | | +---------+ | | | | | | | | | | Portal | | | | Portal | | | Group 1 | | | | Group 2 | +--------------------------+ +--------------+ | | | +--------|---------------|--------------------|---------------------+ | | | | | | +----------------------------+ +-----------------------------+ | | | iSCSI Session (Target side)| | iSCSI Session (Target side) | | | | | | | | | | (TSIH = 56) | | (TSIH = 48) | | | +----------------------------+ +-----------------------------+ | | | | iSCSI Target Node | | (within Network Entity, not shown) | +-------------------------------------------------------------------+ 2.4.2 SCSI Architecture Model This section describes the relationship between the SCSI Architec- ture Model [SAM2] and constructs of the SCSI device, SCSI port and I_T nexus, and the iSCSI constructs described in Section 2.4.1 iSCSI Architecture Model. This relationship implies implementation requirements in order to conform to the SAM2 model and other SCSI operational functions. These requirements are detailed in Section 2.4.3 Consequences of the Model. Julian Satran Expires February 2003 48 iSCSI 5-August-02 The following list outlines mappings of SCSI architectural elements to iSCSI. a) SCSI Device - the SAM2 term for an entity that contains one or more SCSI ports that are connected to a service delivery sub- system and supports a SCSI application protocol. For example, a SCSI Initiator Device contains one or more SCSI Initiator Ports and zero or more application clients. A SCSI Target Device con- tains one or more SCSI Target Ports and one or more logical units. For iSCSI, the SCSI Device is the component within an iSCSI Node that provides the SCSI functionality. As such, there can be one SCSI Device, at most, within a iSCSI Node. Access to the SCSI Device can only be achieved in an iSCSI normal operational ses- sion (see Section 2.3 iSCSI Session Types). The SCSI Device Name is defined to be the iSCSI Name of the node and its use is manda- tory in the iSCSI protocol. b) SCSI Port - the SAM2 term for an entity in a SCSI Device that provides the SCSI functionality to interface with a service deliv- ery subsystem or transport. For iSCSI, the definition of SCSI Ini- tiator Port and SCSI Target Port are different. SCSI Initiator Port: This maps to one endpoint of an iSCSI normal operational session (see Section 2.3 iSCSI Session Types). An iSCSI normal operational session is negotiated through the login process between an iSCSI initiator node and an iSCSI target node. At successful completion of this process, a SCSI Initiator Port is created within the SCSI Initiator Device. The SCSI Initiator Port Name and SCSI Initiator Port Identifier are both defined to be the iSCSI Initiator Name together with (a) a label that identifies it as an initiator port name/identifier and (b) the ISID portion of the session identifier. SCSI Target Port: This maps to an iSCSI Target Portal Group. The SCSI Target Port Name and the SCSI Target Port Identifier are both defined to be the iSCSI Target Name together with (a) a label that identifies it as a target port name/identifier and (b) the portal group tag. The SCSI Port Name is mandatory in iSCSI. When used in SCSI param- eter data, the SCSI port name MUST be encoded as: - The iSCSI Name in UTF-8 format, followed by - a comma separator (1 byte), followed by Julian Satran Expires February 2003 49 iSCSI 5-August-02 - the ASCII character 'i' (for SCSI Initiator Port) or the ASCII character 't' (for SCSI Target Port), followed by - a comma separator (1 byte), followed by - A hexadecimal representation (see Section 4.1 Text For- mat) of the ISID (for SCSI initiator port) or the portal group tag (for SCSI target port) including the initial 0X and the terminating null. SCSI port names have a maximum length of 255 bytes. The ASCII character 'i' or 't' is the label that identi- fies this port as either a SCSI Initiator Port or a SCSI Target Port. c) I_T nexus - a relationship between a SCSI Initiator Port and a SCSI Target Port, according to [SAM2]. For iSCSI, this relation- ship is a session, defined as a relationship between an iSCSI Ini- tiator's end of the session (SCSI Initiator Port) and the iSCSI Target's Portal Group. The I_T nexus can be identified by the con- junction of the SCSI port names or by the iSCSI session identi- fier SSID. iSCSI defines the I_T nexus identifier to be the tuple (iSCSI Initiator Name + 'i' + ISID, iSCSI Target Name + 't' + Por- tal Group Tag). NOTE: The I_T nexus identifier is not equal to the session identi- fier (SSID). 2.4.3 Consequences of the Model This section describes implementation and behavioral requirements that result from the mapping of SCSI constructs to the iSCSI con- structs defined above. Between a given SCSI initiator port and a given SCSI target port, only one I_T nexus (session) can exist. No more than one nexus relationship (parallel nexus) is allowed by [SAM2}. Therefore, between a given iSCSI initiator node and an iSCSI target node, at any given time, only one session can exist with the same session identifier (SSID). These assumptions lead to the following conclusions and requirements: ISID RULE: Between a given iSCSI Initiator and iSCSI Target Portal Group (SCSI target port), there can be only one session with a given Julian Satran Expires February 2003 50 iSCSI 5-August-02 value for ISID that identifies the SCSI initiator port. See Section 9.12.5 ISID. The structure of the ISID that contains a naming authority component (see Section 9.12.5 ISID and [NDT]) provides a mechanism to facili- tate compliance with the ISID rule (See also Section 8.1.1 Conserva- tive Reuse of ISIDs). The iSCSI Initiator Node should manage the assignment of ISIDs prior to session initiation. The "ISID RULE" does not preclude the use of the same ISID from the same iSCSI Initiator with different Target Portal Groups on the same iSCSI target or on other iSCSI targets (see Section 8.1.1 Conservative Reuse of ISIDs). Allowing this would be analogous to a single SCSI Initiator Port having relationships (nexus) with multiple SCSI target ports on the same SCSI target device or SCSI target ports on other SCSI target devices. It is also possible to have multiple sessions with different ISIDs to the same Target Portal Group. Each such session would be considered to be with a different initiator even when the sessions originate from the same initiator device. The same ISID may be used by a different iSCSI ini- tiator because it is the iSCSI Name together with the ISID that iden- tifies the SCSI Initiator Port. NOTE: A consequence of the ISID RULE and the specification for the I_T nexus identifier is that two nexus with the same identifier should never exist at the same time. TSIH RULE: The iSCSI Target selects a non-zero value for the TSIH at session creation (when an initiator presents a 0 value at Login). After being selected, the same TSIH value MUST be used whenever ini- tiator or target refer to the session and a TSIH is required. 2.4.3.1 I_T Nexus State Certain nexus relationships contain an explicit state (e.g., initia- tor-specific mode pages) that may need to be preserved by the device server [SAM2] in a logical unit through changes or failures in the iSCSI layer (e.g., session failures). In order for that state to be restored, the iSCSI initiator should re-establish its session (re- login) to the same Target Portal Group using the previous ISID. That is, it should perform session recovery as described in Chapter 5. This is because the SCSI initiator port identifier and the SCSI tar- Julian Satran Expires February 2003 51 iSCSI 5-August-02 get port identifier (or relative target port) form the datum that the SCSI logical unit device server uses to identify the I_T nexus. 2.5 Request/Response Summary This section lists and briefly describes all the iSCSI PDU types (request and responses). All iSCSI PDUs are built as a set of one or more header segments (basic and auxiliary) and zero or one data segments. The header group and the data segment may be followed by a CRC (digest). The basic header segment has a fixed length of 48 bytes. 2.5.1 Request/Response types carrying SCSI payload 2.5.1.1 SCSI-Command This request carries the SCSI CDB and all the other SCSI execute com- mand procedure call (see [SAM2]) IN arguments such as task attributes, Expected Data Transfer Length for one or both transfer directions (the latter for bidirectional commands), and Task Tag (as part of the I_T_L_x nexus). The I_T_L nexus is derived by the initia- tor and target from the LUN field in the request and the I_T nexus implicit in the session identification. In addition, the SCSI-command PDU carries information required for the proper operation of the iSCSI protocol - the command sequence number (CmdSN) and the expected status number (ExpStatSN) on the con- nection it is issued. All or part of the SCSI output (write) data associated with the SCSI command may be sent as part of the SCSI-Command PDU as a data seg- ment. 2.5.1.2 SCSI-Response The SCSI-Response carries all the SCSI execute-command procedure call (see [SAM2]) OUT arguments and the SCSI execute-command procedure call return value. The SCSI-Response contains the residual counts from the operation if any, and an indication of whether the counts represent an overflow or an underflow, and the SCSI status if the status is valid or a Julian Satran Expires February 2003 52 iSCSI 5-August-02 response code (a non-zero return value for the execute-command proce- dure call) if the status is not valid. For a valid status that indicates that the command has been pro- cessed but resulted in a exception (e.g., a SCSI CHECK CONDITION), the PDU data segment contains the associated sense data. The use of Autosense ([SAM2]) is REQUIRED by iSCSI. Some data segment content may also be associated (in the data seg- ment) with a non-zero response code. In addition, the SCSI-Response PDU carries information required for the proper operation of the iSCSI protocol: - the number of Data-In PDUs that a target has sent (to enable the initiator to check that all have arrived) - StatSN, the Status Sequence Number on this connection - ExpCmdSN the next Expected Command Sequence Number at the target - MaxCmdSN, the maximum CmdSN acceptable at the target from this initiator. 2.5.1.3 Task Management Function Request The Task Management function request provides an initiator a way to explicitly control the execution of one or more SCSI Tasks or iSCSI functions. The PDU carries a function identifier (which task manage- ment function to perform) and enough information to unequivocally identify the task or task-set on which to perform the action, even if the task(s) to act upon has not yet arrived or has been discarded due to an error. The referenced tag identifies an individual task if the function refers to an individual task. The I_T_L nexus identifies task sets. In iSCSI the I_T_L nexus is identified by the LUN and the session identification (the session identifies an I_T nexus). For task sets, the CmdSN of the Task Management function request helps identify the tasks upon which to act, namely all tasks associ- ated with a LUN and having a CmdSN preceding the Task Management function request CmdSN. Julian Satran Expires February 2003 53 iSCSI 5-August-02 The processing of a Task Management function request performed at the target, (i.e., any coordination between responses to the tasks affected and the Task Management function request response is done by the target). 2.5.1.4 Task Management Function Response The Task Management function response carries an indication of func- tion completion for a Task Management function request including how it completed (response and qualifier) and additional information for failure responses. After the Task Management response indicating Task Management func- tion completion, the initiator will not receive any additional responses from the affected tasks. 2.5.1.5 SCSI Data-out and SCSI Data-in SCSI Data-out and SCSI Data-in are the main vehicles by which SCSI data payload is carried between initiator and target. Data payload is associated with a specific SCSI command through the Initiator Task Tag. For target convenience, outgoing solicited data also carries a Target Transfer Tag (copied from R2T) and the LUN. Each PDU contains the payload length and the data offset relative to the buffer address contained in the SCSI execute command procedure call. In each direction, the data transfer is split into "sequences". An end-of-sequence is indicated by the F bit. An outgoing sequence is either unsolicited (only the first sequence can be unsolicited) or is a complete payload sent in response to an R2T "prompt". Input sequences are built to enable the direction switching for bidi- rectional commands. For input, the target may request positive acknowledgement of input data. This is limited to sessions that support error recovery and is implemented through the A bit in the SCSI Data-in PDU header. Data-in and Data-out PDUs also carry the DataSN to enable the initia- tor and target to detect missing PDUs (discarded due to an error). StatSN is also carried by the Data-In PDUs. Julian Satran Expires February 2003 54 iSCSI 5-August-02 To enable a SCSI command to be processed involving a minimum number of messages, the last SCSI Data-in PDU passed for a command may also contain the status if the status indicates termination with no excep- tions (no sense or response involved). 2.5.1.6 Ready To Transfer (R2T) R2T is the mechanism by which the SCSI target "requests" the initia- tor for output data. R2T specifies to the initiator the offset of the requested data relative to the buffer address from the execute com- mand procedure call and the length of the solicited data. To help the SCSI target to associate resulting Data-out with an R2T, the R2T carries the Target Transfer Tag copied by the initiator in the solicited SCSI Data-out PDUs. There are no protocol specific requirements with regard to the value of these tags, but it is assumed that together with the LUN, they will enable the target to associate data with an R2T. R2T also carries information required for proper operation of the iSCSI protocol, such as: - R2TSN (to enable an initiator to detect a missing R2T) - StatSN - ExpCmdSN - MaxCmdSN 2.5.2 Requests/Responses carrying SCSI and iSCSI Payload 2.5.2.1 Asynchronous Message Asynchronous Messages are used to carry SCSI asynchronous events (AEN) and iSCSI asynchronous messages. When carrying an AEN, the event details are reported as sense data in the data segment. 2.5.3 Requests/Responses carrying iSCSI Only Payload 2.5.3.1 Text Request and Text Response Text requests and responses are designed as a parameter negotiation vehicle and as a vehicle for future extension. Julian Satran Expires February 2003 55 iSCSI 5-August-02 In the data segment key=value, Text Requests/Responses carry text information with a simple syntax. Text Request/Responses may form extended sequences using the same Initiator Task Tag. The initiator uses the F (Final) flag bit in the text request header to indicate its readiness to terminate a sequence. The target uses the F (Final) flag bit in the text response header to indicate its consent to sequence termination. Text Request and Responses also use the Target Transfer Tag to indi- cate continuation of an operation or a new beginning. A target that wishes to continue an operation will set the Target Transfer Tag in a Text Response to a value different from the default 0xffffffff. An initiator willing to continue will copy this value into the Target Transfer Tag of the next Text Request. If the initiator wants to reset the target (start fresh) it will set the Target Transfer Tag to 0xffffffff. Although a complete exchange is always started by the initiator, spe- cific parameter negotiations may be initiated by the initiator or target. 2.5.3.2 Login Request and Login Response Login Requests and Responses are used exclusively during the Login Phase of each connection to set up the session and connection parame- ters (the Login Phase consists of a sequence of login requests and responses carrying the same Initiator Task Tag). A connection is identified by an arbitrarily selected connection-ID (CID) that is unique within a session. Similar to the Text Requests and Responses, Login Requests/Responses carry key=value text information with a simple syntax in the data segment. The Login Phase proceeds through several stages (security negotia- tion, operational parameter negotiation) that are selected with two binary coded fields in the header - the "current stage" (CSG) and the "next stage" (NSG) with the appearance of the latter being signaled by the "transit" flag (T). Julian Satran Expires February 2003 56 iSCSI 5-August-02 The first Login Phase of a session plays a special role (it is called the leading login) and some header fields are determined by the lead- ing login (e.g., the version number, the maximum number of connec- tions, the session identification). The CmdSN initial value is also set by the leading login. Status counting for each connection is initiated by the connection login. A login request may indicate an implied logout (cleanup) of the con- nection to be logged in (we call this a connection restart) by using the same Connection ID (CID) as an existing connection, in the login request header, as well as the same session identifying elements of the session to which the old connection was associated. 2.5.3.3 Logout Request and Response Logout Requests and Responses are used for the orderly closing of connections for recovery or maintenance. The logout request may be issued following a target prompt (through an asynchronous message) or at an initiators initiative. When issued on the connection to be logged out no other request may follow it. The Logout response indicates that the connection or session cleanup is completed and no other responses will arrive on the connection (if received on the logging-out connection). The Logout Response indi- cates also how long the target will keep on holding resources for recovery (e.g., command execution that continues on a new connec- tion) in the text key Time2Retain and how long the initiator must wait before proceeding with recovery in the text key Time2Wait. 2.5.3.4 SNACK Request With the SNACK Request, the initiator requests retransmission of num- bered-responses or data from the target. A single SNACK request cov- ers a contiguous set of missing items, called a run, of a given type of items (the type is indicated in a type field in the PDU header). The run is composed of an initial item (StatSN, DataSN, R2TSN) and the number of missed Status, Data, or R2T PDUs. For long data-in sequences, the target may request (at predefined minimum intervals) a positive acknowledgement for the data sent. A SNACK request with a type field that indicates ACK and the number of Data-In PDUs acknowl- edged conveys this positive acknowledgement. Julian Satran Expires February 2003 57 iSCSI 5-August-02 2.5.3.5 Reject Reject enables the target to report an iSCSI error condition (e.g., protocol, unsupported option) that uses a Reason field in the PDU header and includes the complete header of the bad PDU in the Reject PDU data segment. 2.5.3.6 NOP-Out Request and NOP-In Response This request/response pair may be used by an initiator and target as a "ping" mechanism to verify that a connection/session is still active and all its components are operational. Such a ping may be triggered by the initiator or target. The triggering party indicates that it wants a reply by setting a value different from the default 0xffffffff in the corresponding Initiator/Target Transfer Tag. NOP-In/NOP-Out may also be used "unidirectional" to convey to the initiator/target command, status or data counter values when there is no other "carrier" and there is a need to update the initiator/tar- get. Julian Satran Expires February 2003 58 iSCSI 5-August-02 3. SCSI Mode Parameters for iSCSI There are no iSCSI specific mode pages. Julian Satran Expires February 2003 59 iSCSI 5-August-02 4. Login and Full Feature Phase Negotiation iSCSI parameters are negotiated at session or connection establish- ment by using Login Requests and Responses (see Section 2.2.3 iSCSI Login) and during Full Feature Phase (Section 2.2.4 iSCSI Full Fea- ture Phase) by using Text Requests and Responses. In both cases the mechanism used is an exchange of key=value pairs by which the par- ties either declare the value of a parameter that they expect the other party to use (a declaration) or one of the parties (the propos- ing party) proposes a value or set of values based on which the other party (the accepting party) makes a selection. For most of the param- eters both the initiator and target can be proposing parties. During the Login process one proceeds in two stages - the security negotiation stage and the operational parameter negotiation stage. Both stages are optional but at least one of them has to be present to enable setting some mandatory parameters. If present the security negotiation stage precedes the operational parameter negotiation stage. Progression from stage to stage is controlled by the T (Transition) bit in the Login Request/Response PDU header. Through the T bit set to 1 the initiator indicates that it would like to transition and the target agrees to the transition (and selects the next stage) when ready. A field in the Login PDU header indicates the current stage (CSG) and during transition another field indicates the next stage (NSG) proposed (initiator) and selected (target). The Text negotiation process is used to negotiate or just declare operational parameters. The negotiation process is controlled by the F (final) bit in the PDU header. During text negotiations the F bit is used by the initiator to indicate that it is ready to finish the negotiation and by the Target to acquiesce the end of negotiation. Since some key=value pairs may not fit entirely in a single PDU the C (continuation) bit is used (both in Login and Text) to indicate that "more follows". The text negotiation uses an additional mechanism by which a target may deliver larger amounts of data to an enquiring initiator - the target sets a Target Task Tag to be used as a bookmark; when returned Julian Satran Expires February 2003 60 iSCSI 5-August-02 by the initiator it means "go on", if reset to a "neutral value" it means "forget about the rest". This chapter details types of keys and values used, the syntax rules for parameter formation and the negotiation schemes to be used with different types of parameters. 4.1 Text Format The initiator and target send a set of key=value pairs encoded in UTF-8 Unicode. All the text keys and text values specified in this document are to be presented and interpreted in the case they appear in this document. They are case sensitive. The following character symbols are used in this document for text items (the hexadecimal values represent Unicode code points): (a-z, A-Z) - letters (0-9) - digits " " (0x20) - space "." (0x2e) - dot "-" (0x2d) - minus "+" (0x2b) - plus "@" (0x40) - commercial at "_" (0x5f) - underscore "=" (0x3d) - equal ":" (0x3a) - colon "/" (0x2f) - solidus or slash "[" (0x5b) - left bracket "]" (0x5d) - right bracket null (0x00) - null separator "," (0x2c) - comma "~" (0x7e) - tilde Key=value pairs may span PDU boundaries. An initiator or target that sends partial key=value text within a PDU indicates that more text follows by setting the C bit in the Text or Login Request or Text or Login Response to 1. Data segments in a series of PDUs having the C bit set to 1 and ending with a PDU having the C bit set to 0 or including a single PDU having the C bit set to 0 have to be consid- ered as forming a single logical-text-data-segment (LTDS). Julian Satran Expires February 2003 61 iSCSI 5-August-02 Every key=value pair, including the last or only pair in a LTDS, MUST be followed by one null (0x00) delimiter. A key-name is whatever precedes the first = in the key=value pair. The term key is used frequently in this document with the meaning of key-name. A value is whatever follows the first = in the key=value pair up to the end of the key=value pair but not including the null delimiter. The following definitions will be used in the rest of this document: standard-label: a string of one or more characters consisting of letters, digits, dot, minus, plus, commercial at, and underscore. A standard-label MUST begin with a capital let- ter and must not exceed 63 characters. key-name: a standard-label. text-value: a string of 0 or more characters consisting of let- ters, digits, dot, minus, plus, commercial at, underscore, slash, left bracket, right bracket and colon. iSCSI-name-value: a string of one or more characters consist- ing of minus, dot, colon and any character allowed by the output of the iSCSI string-prep template as specified in [STPREP-iSCSI] (see also Section 2.2.6.2 iSCSI Name Encod- ing). iSCSI-local-name-value: a UTF-8 string; no null characters are allowed in the string. This encoding is to be used for local- ized (internationalized) aliases. boolean-value: the string "Yes" or "No". hex-constant: hexadecimal constant encoded as a string start- ing with "0x" or "0X" followed by 1 or more digits or the letters a, b, c, d, e, f, A, B, C, D, E and F. Hex-constants are used to encode numerical values or binary strings. When used to encode numerical values the excessive use of leading 0 digits is discouraged. The string following 0X (or 0x) rep- resents a base16 number starting with the most significant base16 digit, followed by all other digits in decreasing sig- nificance order and ending with the least-significant base16 digit. When used to encode binary strings hexadecimal con- stants have an implicit byte-length that includes 4 bits for every hexadecimal digit of the constant, including leading Julian Satran Expires February 2003 62 iSCSI 5-August-02 zeroes (i.e., a hex-constant of n hexadecimal digits has a byte-length of (the integer part of) (n+1)/2). decimal-constant: an unsigned decimal number - the digit 0 or a string of 1 or more digits starting with a non-zero digit. Decimal-constants are used to encode numerical values or binary strings. Decimal constants can be used to encode binary strings only if the stringlength is explicitly speci- fied. There is no implicit length for decimal strings. Deci- mal-constant MUST NOT used to for parameter values if those values are allowed to be equal or greater than 2**64 (numeri- cal) or for binary strings that allowed be longer than 64 bits. base64-constant: base64 constant encoded as a string starting with "0b" or "0B" followed by 1 or more digits or letters or plus or slash or equal. The encoding is done according to [RFC2045] and each character, except equal, represents a base64 digit or a 6-bit binary string. Base64-constants are used to encode numerical-values or binary strings. When used to encode numerical values the excessive use of leading 0 digits (encoded a A) is discouraged. The string following 0B (or 0b) represents a base64 number starting with the most significant base64 digit, followed by all other digits in decreasing significance order and ending with the least-sig- nificant base64 digit; the least significant base64 digit may be optionally followed by pad digits (encoded as equal) that are not considered as part of the number. When used to encode binary strings base64-constants have an implicit byte-length that includes 6 bits for every character of the constant excluding trailing equals (i.e., a base64-constant of n base64 characters excluding the trailing equals has a byte- length of ((the integer part of) (n*3/4)). Correctly encoded base64 strings cannot have n values of 1, 5 ... k*4+1. numerical-value: an unsigned integer always less than 2**64 encoded as a decimal-constant or a hex-constant. Unsigned integer arithmetic applies to numerical-values. large-numerical-value: an unsigned integer that can be larger than or equal to 2**64 encoded as a hex constant, or base64- constant. Unsigned integer arithmetic applies to large- numeric-values. numeric-range: two numerical-values separated by a tilde where the value to the right of tilde must not be lower that the value to the left. Julian Satran Expires February 2003 63 iSCSI 5-August-02 regular-binary-value: a binary string less than 64 bits encoded as a decimal constant, hex constant or base64-constant. The length of the string is either specified by the key defini- tion or is implicit byte-length of the encoded string. large-binary-value: a binary string longer than 64 bits encoded as a hex-constant or base64-constant. The length of the string is either specified by the key definition or is implicit byte-length of the encoded string. binary-value: a regular-binary-value or a large-binary-value. Operations on binary values are key specific. simple-value: text-value, iSCSI-name-value, boolean-value, numeric-value, a numeric-range or a binary-value. list-of-values: a sequence of text-values separated by comma. If not otherwise specified, the maximum length of a simple-value (not its encoded representation) is 255 bytes not including the delimiter (comma or zero byte). Any iSCSI target or initiator MUST support receiving at least 8192 bytes of key=value data in a negotiation sequence. When proposing or accepting authentication methods that explicitly require support for very long authentication items initiator and target MUST support receiving at least 64 kilobytes of key=value data (e.g, see Appendix 10.1.2 - Simple Public-Key Mechanism (SPKM) - that require support for public key certificates). 4.2 Text Mode Negotiation During login, and thereafter, some session or connection parameters are either declared or negotiated through an exchange of textual information. The initiator starts the negotiation and/or declaration through a Text or Login request and indicates when it is ready for completion (by setting to 1 and keeping to 1 the F bit in a Text Request or the T bit in the Login Request). As negotiation text may span PDU bound- aries a Text or Login Request or Text or Login Response PDU having the C bit set to 1 MUST NOT have the F/T bit set to 1. A target receiving a Text or Login Request or an initiator receiving a Text or Login Response with the C bit set to 1 MUST answer with a Julian Satran Expires February 2003 64 iSCSI 5-August-02 Text or Login Response respectively Text or Login Request with no data segment (DataSegmentLength 0). A target or initiator SHOULD NOT use a Text or Login Response or Text or Login Request with no data segment (DataSegmentLength 0) unless explicitly required by a general or a key-specific negotiation rule. The format of a declaration is: Declarer-> <key>=<valuex> The general format of text negotiation is: Proposer-> <key>=<valuex> Acceptor-> <key>=<valuey>|NotUnderstood|Irrelevant|Reject Thus a declaration is a one-way textual exchange while a negotiation is a two-way exchange. The proposer or declarer can either be the initiator or the target and the acceptor can either be the target or initiator, respec- tively. Targets are not limited to respond to key=value pairs as pro- posed by the initiator. The target may propose key=value pairs of its own. All negotiations are explicit (i.e., the result MUST be based only on newly exchanged or declared values). There are no implicit propos- als. If an proposal is not made then a reply cannot be expected. Con- servative design requires also that default values should not be relied upon when use of some other value has serious consequences. The value proposed or declared can be a numerical-value, a numerical- range defined by lower and upper value with both integers separated by tilde, a binary value, a text-value, a iSCSI-name-value, an iSCSI- local-name-value, a boolean-value (Yes or No), or a list of comma separated text-values. A range, a large-numerical-value, an iSCSI- name-value and an iSCSI-local-name-value MAY ONLY be used if it is explicitly allowed. An accepted value can be a numerical-value, a large-numerical-value, a text-value or a boolean-value. If a specific key is not relevant for the current negotiation, the acceptor may answer with the constant "Irrelevant" for all types of negotiation. However the negotiation is not considered as failed if Julian Satran Expires February 2003 65 iSCSI 5-August-02 the answer is "Irrelevant". The "Irrelevant" answer is meant for those cases in which several keys are presented by an proposing party but the selection made by the acceptor for one of the keys makes other keys irrelevant. The following examples illustrates the use "Irrelevant": I->T OFMarker=Yes,OFMarkInt=2048~8192 T->I OFMarker=No,OFMarkInt=Irrelevant I->T X#vkey1=(bla,alb,None),X#vkey2=(bla,alb) T->I X#vkey2=None,X#vkey2=Irrelevant Any key not understood by the acceptor may be ignored by the accep- tor without affecting the basic function. However, the answer for a key not understood MUST be key=NotUnderstood. The constants "None", "Reject", "Irrelevant", and "NotUnderstood" are reserved and must only be used as described here. Reject or Irrelevant are legitimate negotiation options where allowed but their excessive use is discouraged. A negotiation is considered complete when the acceptor has sent the key value pair even if the value is "Reject", "Irrelevant", or "NotUnderstood. Sending the key again would be a re-negotiation and is forbidden for many keys. If the acceptor sends "Reject" as an answer the negotiated key is left at its current value (or default if no value was set). If the current value is not acceptable to the proposer on the connection or session it is sent the proposer MAY choose to terminate the connec- tion or session. All keys in this document except for the X extension formats, MUST be supported by iSCSI initiators and targets when used as specified here. If used as specified those keys MUST NOT be answered with NotUnderstood. Implementers may introduce new keys by prefixing them with X- fol- lowed by their (reversed) domain name, or with new keys registered with IANA prefixing them with X#. For example the entity owning the domain acme.com can issue: Julian Satran Expires February 2003 66 iSCSI 5-August-02 X-com.acme.bar.foo.do_something=3 or a new registered key may be used as in: X#SuperCalyPhraGilistic=Yes Implementers MAY introduce also new values but ONLY for new keys or authentication methods (see Section 10 iSCSI Security Keys and Authentication Methods) or digests (see Section 11.1 HeaderDigest and DataDigest) Whenever parameter action or acceptance are dependent on other param- eters, the dependency rules and parameter sequence must be specified with the parameters. In the Login Phase (see Section 4.3 Login Phase) every stage is a separate negotiation. In FullFeaturePhase a Text Request Response sequence is a negotiation. Negotiations MUST be handled as atomic operations - i.e., all negotiated values go into effect after the negotiation concludes in agreement or are ignored if the negotiation fails. Some parameters may be subject to integrity rules (e.g., parameter-x must not exceed parameter-y or parameter-u not 1 implies parameter-v to be Yes). Whenever required, integrity rules are specified with the keys. Checking for compliance with the integrity rule MUST NOT be performed before all the negotiation parameters are available (the existent and newly negotiated). An iSCSI target MUST perform integ- rity checking before the new for parameters take effect. An initia- tor MAY perform integrity checking. 4.2.1 List negotiations In list negotiation, the originator sends a list of values (which may include "None") in its order of preference. The responding party MUST respond with the same key and the first value that it supports (and is allowed to use for the specific origi- nator) selected from the originator list. Julian Satran Expires February 2003 67 iSCSI 5-August-02 The constant "None" MUST always be used to indicate a missing func- tion. However, "None" is a valid selection only if it is explicitly proposed. If an acceptor does not understand any particular value in a list it MUST ignore it. If an acceptor does not support, does not understand or is not allowed to use any of the proposed options with a specific originator, it may use the constant "Reject" or terminate the negoti- ation. The selection of a value not proposed MUST be handled as a protocol error. 4.2.2 Simple-value negotiations For simple-value negotiations, the accepting party MUST answer with the same key. The value it selects becomes the negotiation result. Proposing a value not admissible (e.g., not within the specified bounds) MAY be answered with the constant "Reject" or the acceptor MAY select an admissible value. The selection, by the acceptor, of a value not admissible under the selection rules is considered a protocol error. The selection rules are key-specific. For a numerical range the value selected must be an integer within the proposed range or "Reject" (if the range is unacceptable). For boolean negotiations (i.e., keys taking the values Yes or No), the accepting party MUST answer with the same key and the result of the negotiation when the received value does not determine that result by itself. The last value transmitted becomes the negotiation result. The rules for selecting the value to answer with are expressed as Boolean functions of the value received, and the value that the accepting party would have selected if given a choice. Specifically, the two cases in which answers are OPTIONAL are: - The boolean function is "AND" and the value "No" is received. The outcome of the negotiation is "No". - The boolean function is "OR" and the value "Yes" is received. The outcome of the negotiation is "Yes". Responses are REQUIRED in all other cases, and the value chosen and sent by the acceptor becomes the outcome of the negotiation. Julian Satran Expires February 2003 68 iSCSI 5-August-02 4.3 Login Phase The Login Phase establishes an iSCSI session between an initiator and a target. It sets the iSCSI protocol parameters, security parame- ters, and authenticates the initiator and target to each other. The Login Phase is implemented via Login request and responses only. The whole Login Phase is considered as a single task and has a sin- gle Initiator Task Tag (similar to the linked SCSI commands). The default MaxRecvDataSegmentLength is used during Login. The Login Phase sequence of requests and responses proceeds as fol- lows: - Login initial request - Login partial response (optional) - More Login requests and responses (optional) - Login Final-Response (mandatory) The initial login request of any connection MUST include the Initia- torName key=value pair. The initial login request of the first con- nection of a session MAY also include the SessionType key=value pair. For any connection within a session whose type is not "Discovery", the first login request MUST also include the TargetName key=value pair. The Login Final-response accepts or rejects the Login request. The Login Phase MAY include a SecurityNegotiation stage and a Login- OperationalNegotiation stage and MUST include at least one of them, but the included stage MAY be empty except for the mandatory names. The login requests and responses contain a field that indicates the negotiation stage (SecurityNegotiation or LoginOperationalNegotia- tion). If both stages are used, the SecurityNegotiation MUST precede the LoginOperationalNegotiation. Some operational parameters can be negotiated outside the login through Text requests and responses. Security MUST be completely negotiated within the Login Phase. In addition the use of underlying IPsec security is specified in Chap- Julian Satran Expires February 2003 69 iSCSI 5-August-02 ter 7 and in [SEC-IPS]. iSCSI support for security within the proto- col consists only of authentication in the Login Phase. In some environments, a target or an initiator is not interested in authenticating its counterpart. It is possible to bypass authentica- tion through the Login request and response. The initiator and target MAY want to negotiate iSCSI authentication parameters. Once this negotiation is completed, the channel is con- sidered secure. Most of the negotiation keys are only allowed in a specific stage. The SecurityNegotiation keys appear in Chapter 10 and the LoginOpera- tionalNegotiation keys appear in Chapter 11. Only a limited set of keys (marked as Any-Stage in Chapter 11) may be used in any of the two stages. Any given Login request or response belongs to a specific stage; this determines the negotiation keys allowed with the request or response. Sending a key not allowed in the current stage is considered a proto- col error. Stage transition is performed through a command exchange (request/ response) that carries the T bit and the same current stage code. During this exchange, the next stage is selected by the target and MUST NOT exceed the value stated by the initiator. The initiator can request a transition whenever it is ready, but a target can respond with a transition only after one is proposed by the initiator. In a negotiation sequence, the T bit settings in one pair of login request-responses have no bearing on the T bit settings of the next pair. An initiator that has a T bit set to 1 in one pair and is answered with a T bit setting of 0 may issue the next request with T bit set to 0. When a transition is requested by the initiator and acknowledged by the target both initiator and target switch to the selected stage. Targets MUST NOT submit parameters that require an additional initia- tor login request in a login response with the T bit set to 1. Stage transitions during login (including entering and exit) are pos- sible only as outlined in the following table: Julian Satran Expires February 2003 70 iSCSI 5-August-02 +-----------------------------------------------------------+ |From To -> | Security | Operational | FullFeature | | | | | | | | V | | | | +-----------------------------------------------------------+ | (start) | yes | yes | no | +-----------------------------------------------------------+ | Security | no | yes | yes | +-----------------------------------------------------------+ | Operational | no | no | yes | +-----------------------------------------------------------+ The Login Final-Response that accepts a Login Request can come only as a response to a Login request with the T bit set to 1, and both the request and response MUST indicate FullFeaturePhase as the next phase via the NSG field. Neither the initiator nor the target should attempt to declare or negotiate a parameter more than once during login except for responses to specific keys that explicitly allow repeated key decla- rations (e.g. TargetAddress). If an attempt to re-negotiate/re- declare parameters not specifically allowed is detected by the tar- get the target MUST respond with Login reject (initiator error); if detected by the initiator the initiator MUST drop the connection. 4.3.1 Login Phase Start The Login Phase starts with a login request from the initiator to the target. The initial login request includes: -Protocol version supported by the initiator. -iSCSI Initiator Name and iSCSI Target Name -ISID, TSIH and connection Ids. -The negotiation stage that the initiator is ready to enter. A login may create a new session or it may add a connection to an existing session. Between a given iSCSI Initiator Node (selected only by an InitiatorName) and a given iSCSI target defined by an iSCSI TargetName and a Target Portal Group Tag, login results are defined by the following table: Julian Satran Expires February 2003 71 iSCSI 5-August-02 +-------------------------------------------------------------------+ |ISID | TSIH | CID | Target action | +-------------------------------------------------------------------+ |new | non-zero | any | fail the login | | | | | ("session does not exist") | +-------------------------------------------------------------------+ |new | zero | any | instantiate a new session | +-------------------------------------------------------------------+ |existing | zero | any | do session reinstatement | | | | | (see section 4.3.5) | +-------------------------------------------------------------------+ |existing | non-zero | new | add a new connection to | | | existing | | the session | +-------------------------------------------------------------------+ |existing | non-zero |existing| do connection reinstatement| | | existing | | (see section 4.3.4) | +-------------------------------------------------------------------+ |existing | non-zero | any | fail the login | | | new | | ("session does not exist") | +-------------------------------------------------------------------+ Determination of existing or new are made by the target. Optionally, the login request may include: -Security parameters OR -iSCSI operational parameters AND/OR -The next negotiation stage that the initiator is ready to enter. The target can answer the login in the following ways: -Login Response with Login reject. This is an immediate rejec- tion from the target that causes the connection to terminate and the session to terminate if this is the first (or only) connection of a new session. The T bit and the CSG and NSG fields are reserved. -Login Response with Login accept as a final response (T bit set to 1 and the NSG in both request and response are set to FullFeaturePhase). The response includes the protocol ver- sion supported by the target and the session ID, and may include iSCSI operational or security parameters (that depend on the current stage). Julian Satran Expires February 2003 72 iSCSI 5-August-02 -Login Response with Login Accept as a partial response (NSG not set to FullFeaturePhase in both request and response) that indicates the start of a negotiation sequence. The response includes the protocol version supported by the tar- get and either security or iSCSI parameters (when no secu- rity mechanism is chosen) supported by the target. If the initiator decides to forego the SecurityNegotiation stage, it issues the Login with the CSG set to LoginOperationalNegotiation and the target may reply with a Login Response that indicates that it is unwilling to accept the connection (see Section 9.13 Login Response) without SecurityNegotiation and will terminate the connection with a response of Authentication failure (see Section 9.13.5 Status-Class and Status-Detail). If the initiator is willing to negotiate iSCSI security, but is unwilling to make the initial parameter proposal and may accept a connection without iSCSI security, it issues the Login with the T bit set to 1, the CSG set to SecurityNegotiation, and NSG set to LoginOp- erationalNegotiation. If the target is also ready to skip security, the Login response containing only the TargetPrtalGroup key (see Sec- tion 11.9 TargetPortalGroupTag) and has T bit set to 1, the CSG set to SecurityNegotiation, and NSG set to LoginOperationalNegotiation. An initiator that chooses to operate without iSCSI security and with all the operational parameters taking the default values issues the Login with the T bit set to 1, the CSG set to LoginOperationalNegoti- ation, and NSG set to FullFeaturePhase. If the target is also ready to forego security and can finish its LoginOperationalNegotiation, the Login response has T bit set to 1, the CSG set to LoginOperation- alNegotiation, and NSG set to FullFeaturePhase in the next stage. During the Login Phase from the iSCSI target MUST return the Target- PortalGroupTag key with the first Login Response PDU it is allowed to do so (i.e., the firs Login Response issued after the first Login Request wit C bit set to 0). The TargetPortalGroupTag key value indi- cates the iSCSI portal group servicing the Login Request PDU. If the reconfiguration of iSCSI portal groups is a concern in a given envi- ronment, the iSCSI initiator MUST use this key to ascertain that it had indeed initiated the Login Phase with the intended target portal group. Julian Satran Expires February 2003 73 iSCSI 5-August-02 4.3.2 iSCSI Security Negotiation The security exchange sets the security mechanism and authenticates the initiator user and the target to each other. The exchange pro- ceeds according to the authentication method chosen in the negotia- tion phase and is conducted using the login requests' and responses' key=value parameters. An initiator directed negotiation proceeds as follows: -The initiator sends a login request with an ordered list of the options it supports (authentication algorithm). The options are listed in the initiator's order of preference. The initiator MAY also send private or public extension options. -The target MUST reply with the first option in the list it supports and is allowed to use for the specific initiator unless it does not support any in which case it MUST answer with "Reject" (see also Section 4.2 Text Mode Negotiation). The parameters are encoded in UTF8 as key=value. For secu- rity parameters, see Chapter 10. -When the initiator considers that it is ready to conclude the SecurityNegotiation stage it sets the T bit to 1 and the NSG to what it would like the next stage to be. The target will then set the T bit to 1 and set NSG to the next stage in the Login response when it finishes sending its security keys. The next stage selected will be the one the target selected. If the next stage is FullFeaturePhase, the target MUST respond with a Login Response with the TSIH value. If the security negotiation fails at the target, then the target MUST send the appropriate Login Response PDU. If the security negotiation fails at the initiator, the initiator SHOULD close the connection. It should be noted that the negotiation might also be directed by the target if the initiator does support security, but is not ready to direct the negotiation (propose options). 4.3.3 Operational Parameter Negotiation During the Login Phase Operational parameter negotiation during the login MAY be done: - Starting with the first Login request if the initiator does not propose any security/ integrity option. Julian Satran Expires February 2003 74 iSCSI 5-August-02 - Starting immediately after the security negotiation if the initiator and target perform such a negotiation. Operational parameter negotiation MAY involve several Login request- response exchanges started and terminated by the initiator. The ini- tiator MUST indicate its intent to terminate the negotiation by set- ting the T bit to 1; the target sets the T bit to 1 on the last response. If the target responds to a Login request having the T bit set to 1 with a Login response having the T bit set to 0, the initiator should keep sending the Login request (even empty) with the T bit set to 1, while it still wants to switch stage, until it receives the Login Response having the T bit set to 1 or it receives a key that requires it to set again the T bit to 0. Some session specific parameters can be specified only during the Login Phase of the first connection of a session (i.e., begun by a login request that contains a zero-valued TSIH) - the leading Login Phase (e.g., the maximum number of connections that can be used for this session). A session is operational once it has at least one connection in Full- FeaturePhase. New or replacement connections can be added to a ses- sion only after the session is operational. For operational parameters, see Chapter 11. 4.3.4 Connection reinstatement Connection reinstatement is the process of an initiator logging in with a ISID-TSIH-CID combination that is possibly active from the target's perspective - causing the implicit logging out of the con- nection corresponding to the CID and reinstating a new Full Feature Phase iSCSI connection in its place (with the same CID). Thus, the TSIH in the Login PDU MUST be non-zero and CID does not change dur- ing a connection reinstatement. The Login request performs the logout function of the old connection if an explicit logout was not per- formed earlier. In sessions with a single connection, this may imply the opening of a second connection with the sole purpose of cleaning up the first. Targets MUST support opening a second connection even when they do not support multiple connections in Full Feature Phase if ErrorRecoveryLevel is 2 and SHOULD support opening a second con- nection if ErrorRecoveryLevel is less than 2. Julian Satran Expires February 2003 75 iSCSI 5-August-02 If the operational ErrorRecoveryLevel is 2, connection reinstatement enables future task reassignment. If the operational ErrorRecovery- Level is less than 2, connection reinstatement is the replacement of the old CID without enabling task reassignment. In this case, all the tasks that were active on the old CID must be immediately terminated without further notice to the initiator. The initiator connection state MUST be CLEANUP_WAIT (section 6.1.3) when the initiator attempts a connection reinstatement. In practical terms, beside the implicit logout of the old connec- tion, reinstatement is equivalent to a new connection login. 4.3.5 Session reinstatement, closure and timeout Session reinstatement is the process of initiator logging in with an ISID that is possibly active from the target's perspective - thus implicitly logging out the session corresponding to the ISID and reinstating a new iSCSI session in its place (with the same ISID). Thus, the TSIH in the Login PDU MUST be zero to signal session rein- statement. Session reinstatement causes all the tasks that were active on the old session to be immediately terminated by the target without further notice to the initiator. The initiator session state MUST be FAILED (Section 6.3 Session State Diagrams) when the initiator attempts a session reinstatement. Session closure is an event defined to be either of the following: - a successful "session close" logout - a successful "connection close" logout for the last Full Fea- ture Phase connection when no other connection in the ses- sion is waiting for cleanup (Section 6.2 Connection Cleanup State Diagram for Initiators and Targets) and no tasks in the session are waiting for reassignment. Session timeout is an event defined to occur when the last connec- tion state timeout expires and no tasks are waiting for reassign- ment. This takes the session to the FREE state (N6 transition in the session state diagram). Julian Satran Expires February 2003 76 iSCSI 5-August-02 4.3.5.1 Loss of Nexus notification The iSCSI layer provides the SCSI layer with the "I_T nexus loss" notification when any one of the following events happens: a) A successful completion of session reinstatement b) A session closure event c) A session timeout event Certain SCSI object clearing actions may result upon this notifica- tion in the SCSI end nodes, as documented in Appendix F. - Clearing effects of various events on targets -. 4.3.6 Session continuation and failure Session continuation is the process by which the state of a pre- existing session continues to be used via either connection rein- statement (Section 4.3.4 Connection reinstatement), or by adding a connection with a new CID. Either of these actions associates the new transport connection with the pre-existing session state. Session failure is an event where the last Full Feature Phase connec- tion reaches the CLEANUP_WAIT state (Section 6.2 Connection Cleanup State Diagram for Initiators and Targets), or completes a successful recovery logout thus causing all active tasks (that are formerly allegiant to the connection) to start waiting for task reassignment. 4.4 Operational Parameter Negotiation Outside the Login Phase Some operational parameters MAY be negotiated outside (after) the Login Phase. Parameter negotiation in Full Feature Phase is done through Text requests and responses. Operational parameter negotiation MAY involve several text request-response exchanges, which the initiator always starts and terminates and uses the same Initiator Task Tag. The ini- tiator MUST indicate its intent to terminate the negotiation by set- ting the F bit to 1; the target sets the F bit to 1 on the last response. If the target responds with a text response with the F bit set to 0 to a text request with the F bit set to 1, the initiator should keep sending the text request (even empty) with the F bit set to 1, while Julian Satran Expires February 2003 77 iSCSI 5-August-02 it still wants to finish the negotiation, until it receives the text response with the F bit set to 1. Responding to a text request with the F bit set to 1 with an empty (no key=value pairs) response with the F bit set to 0 is discouraged. Targets MUST NOT submit parameters that require an additional initia- tor text request in a text response with the F bit set to 1. In a negotiation sequence, the F bit settings in one pair of text request-responses have no bearing on the F bit settings of the next pair. An initiator that has the F bit set to 1 in a request and is being answered with an F bit setting of 0 may issue the next request with the F bit set to 0. Whenever the target responds with the F bit set to 0, it MUST set the Target Transfer Tag to a value other than the default 0xffffffff. An initiator MAY reset an operational parameter negotiation by issu- ing a Text request with the Target Transfer Tag set to the value 0xffffffff after receiving a response with the Target Transfer Tag set to a value other than 0xffffffff. A target may reset an opera- tional parameter negotiation by answering a Text request with a Reject PDU. Neither the initiator nor the target should attempt to declare or negotiate a parameter more than once during any negotiation sequence without an intervening operational parameter negotiation reset except for responses to specific keys that explicitly allow repeated key declarations (e.g. TargetAdress). If detected by the target this MUST result in a Reject PDU with a reason of "protocol error". The initia- tor MUST reset the negotiation as outlined above. Parameters negotiated by a text exchange negotiation sequence become effective only after the negotiation sequence is completed. Julian Satran Expires February 2003 78 iSCSI 5-August-02 5. iSCSI Error Handling and Recovery 5.1 Overview 5.1.1 Background The following two considerations prompted the design of much of the error recovery functionality in iSCSI: i) An iSCSI PDU may fail the digest check and be dropped, despite being received by the TCP layer. iSCSI layer must optionally be allowed to recover such dropped PDUs. ii) A TCP connection may fail at any time during the data transfer. All the active tasks must be option- ally allowed to be continued on a different TCP connection within the same session. Many of the recovery details in an iSCSI implementation are a local matter and beyond the scope of protocol standardization. However, some external aspects of the processing must be standardized to ensure interoperability. This chapter describes a general model for recovery in support of interoperability. See Appendix E. - Algorith- mic Presentation of Error Recovery Classes - for further detail on how the described model may be implemented. Compliant implementa- tions do not have to match the implementation details of this model as presented, but the external behavior of such implementations must correspond to the externally observable characteristics of the pre- sented model. 5.1.2 Goals and the resulting features Following are the major design goals of the iSCSI error recovery scheme: a) Allow iSCSI product differentiation for different target mar- kets by defining multiple sets of error recovery capabilities. b) Ensure interoperability between any two implementations sup- porting different sets of error recovery capabilities. c) Define the error recovery mechanisms to ensure command order- ing even in the face of errors, for initiators that demand order- ing. Julian Satran Expires February 2003 79 iSCSI 5-August-02 d) Do not make additions in the fast path, but allow moderate complexity in the error recovery path. e) Prevent both initiator and target from attempting to recover same set of PDUs at the same time - i.e. there must be a clear "error recovery functionality distribution" between initiator and target. The initiator mechanisms defined in connection with error recovery are: a) NOP-OUT to probe sequence numbers of the target (section 9.18) b) Command retry (section 5.2.1) c) Recovery R2T support (section 5.7) d) Requesting retransmission of status/data/R2T using the SNACK facility (section 9.16) e) Acknowledging the receipt of the data (section 9.16) f) Reassigning the connection allegiance of a task to a differ- ent TCP connection (section 5.2.2) g) Terminating the entire iSCSI session to start afresh (section 5.14.4) The target mechanisms defined in connection with error recovery are: a) NOP-IN to probe sequence numbers of the initiator (section 9.19) b) Requesting retransmission of data using the recovery R2T fea- ture (section 5.7) c) SNACK support (section 9.16) d) Requesting that parts of read data be acknowledged (section 9.7.2) e) Allegiance reassignment support (section 5.2.2) f) Terminating the entire iSCSI session to force the initiator to start over (section 5.14.4) 5.1.3 State expectations For any outstanding SCSI command, it is assumed that iSCSI, in con- junction with SCSI at the initiator, is able to keep enough informa- tion to be able to rebuild the command PDU, and that outgoing data is available (in host memory) for retransmission while the command is outstanding. It is also assumed that at the target, incoming data (read data) MAY be kept for recovery or it can be re-read from a device server. Julian Satran Expires February 2003 80 iSCSI 5-August-02 It is further assumed that a target will keep the "status & sense" for a command it has executed if it supports status retransmission. A target that agrees to support data retransmission in addition is also expected to be prepared to retransmit the outgoing data (i.e. Data-In) on request until either the status for the completed com- mand is acknowledged, or the data in question had been separately acknowledged. 5.2 Retry and Reassign in Recovery This section summarizes two important and somewhat related iSCSI pro- tocol features used in error recovery. 5.2.1 Usage of Retry By resending the same iSCSI command PDU ("retry") in the absence of a command acknowledgement (by way of an ExpCmdSN update) or a response, an initiator attempts to "plug" (what it thinks are) the discontinui- ties in CmdSN ordering on the target end. Discarded command PDUs, due to digest errors, may have created these discontinuities. Retry MUST NOT be used for reasons other than plugging command sequence gaps, and in particular cannot be used for requesting PDU retransmissions from a target. Any such PDU retransmission requests for a currently allegiant command in progress may be made using the SNACK mechanism already described in section 9.16, although the usage of SNACK is OPTIONAL. If initiators, as part of plugging command sequence gaps as described above, inadvertently issue retries for allegiant commands already in progress (i.e., targets did not see the discontinuities in CmdSN ordering), the duplicate commands are silently ignored by targets as specified in section 2.2.2.1. When an iSCSI command is retried, the command PDU MUST carry the original Initiator Task Tag and the original operational attributes (e.g., flags, function names, LUN, CDB etc.) as well as the original CmdSN. The command being retried MUST be sent on the same connection as the original command unless the original connection was already successfully logged out. Julian Satran Expires February 2003 81 iSCSI 5-August-02 5.2.2 Allegiance Reassignment By issuing a "task reassign" task management request (Section 9.5.1 Function), the initiator signals its intent to continue an already active command (but with no current connection allegiance) as part of connection recovery. This means that a new connection allegiance is requested for the command, that seeks to associate it to the connec- tion on which the task management request is being issued. Before the allegiance reassignment is attempted for a task, an implicit or explicit Logout with the reason code "remove the connection for recovery" ( see section 9.14) MUST be successfully completed for the previous connection the task was allegiant to. In reassigning connection allegiance for a command, the targets SHOULD continue the command from its current state. For example, when reassigning read commands, the target SHOULD take advantage of Exp- DataSN field provided by the Task Management function request (which must be set to zero if there was no data transfer) and bring the read command to completion by sending the remaining data and sending (or resending) the status. ExpDataSN acknowledges all data sent up to - but not including the Data-In PDU and or R2T with DataSN (or R2TSN) equal to ExpDataSN. However, targets may choose to send/receive the entire data on a reassignment of connection allegiance if unable to recover or maintain accurate state. Initiators MUST not subse- quently request data retransmission trough Data SNACK for PDUs num- bered less than ExpDataSN (i.e., prior to the acknowledged sequence number). For all types of commands, a reassignment request implies that the task is still considered in progress by the initiator and the target must conclude the task appropriately if the target returns the "Function Complete" response to the reassignment request. This might possibly involve retransmission of data/R2T/status PDUs as nec- essary, but MUST involve the (re)transmission of the status PDU. It is OPTIONAL for targets to support the allegiance reassignment. This capability is negotiated via the ErrorRecoveryLevel text key during the login time. When a target does not support allegiance reassignment, it MUST respond with a Task Management response code of "Allegiance reassignment not supported". If allegiance reassignment is supported by the target, but the task is still allegiant to a dif- ferent connection or a successful recovery Logout of the previously allegiant connection was not performed, the target MUST respond with a Task Management response code of "Task still allegiant". Julian Satran Expires February 2003 82 iSCSI 5-August-02 If allegiance reassignment is supported by the target, the Task Man- agement response to the reassignment request MUST be issued before the reassignment becomes effective. If a SCSI Command involving data input is reassigned (see Section 5.2.2 Allegiance Reassignment) any SNACK Tag it holds for a final response from the original connection is deleted and the default value of 0 MUST be used instead. 5.3 Usage Of Reject PDU in Recovery Targets MUST NOT implicitly terminate an active task by sending a Reject PDU for any PDU exchanged during the life of the task. If the target decides to terminate the task, a Response PDU (SCSI, Text, Task etc.) must be returned by the target to conclude the task. If the task had never been active before the Reject (i.e., the Reject is on the command PDU), targets should not send any further responses because the command itself is being discarded. The above rule means that the initiators can eventually expect a response even on receiving Reject's, if the received Reject is for a PDU other than the command PDU itself. The non-command Reject's only have diagnostic value in logging the errors, and they can be used for retransmission decisions by the initiators. The CmdSN of the rejected command PDU (if it is a non-immediate com- mand) MUST NOT be considered received by the target (i.e., a command sequence gap must be assumed for the CmdSN), even though the CmdSN of the rejected command PDU may be reliably ascertained. Upon receiv- ing the Reject, the initiator MUST plug the CmdSN gap in order to continue to use the session - the gap may be plugged either by trans- mitting a command PDU with the same CmdSN, or by aborting the task (see section 5.9 on how an abort may plug a CmdSN gap). When a data PDU is rejected and its DataSN can be ascertained, a tar- get MUST advance ExpDataSN for the current data burst if a recovery R2T is being generated. The target MAY advance its ExpDataSN if it does not attempt to recover the lost data PDU. 5.4 Connection timeout management iSCSI defines two session-global timeout values (in seconds) - Time2Wait and Time2Retain - that are applicable when an iSCSI Full Feature Phase connection is taken out of service either intention- Julian Satran Expires February 2003 83 iSCSI 5-August-02 ally or on an exception. Time2Wait is the initial "respite time" before attempting an explicit/implicit Logout for the CID in ques- tion or task reassignment for the affected tasks (if any). Time2Retain is the maximum time after the initial respite interval that the task and/or connection state(s) is/are guaranteed to be maintained on the target to cater to a possible recovery attempt. Recovery attempts for the connection and/or task(s) SHOULD NOT be made before Time2Wait seconds, but MUST be completed within Time2Retain seconds after that initial Time2Wait waiting period. 5.4.1 Timeouts on transport exception events A transport connection shutdown or a transport reset without any preceding iSCSI protocol interactions informing of the fact causes a Full Feature Phase iSCSI connection to be abruptly terminated. The timeout values to be used in this case are the negotiated values of DefaultTime2Wait (Section 11.15 DefaultTime2Wait) and DefaultTime2Retain (Section 11.16 DefaultTime2Retain) text keys for the session. 5.4.2 Timeouts on planned decommissioning Any planned decommissioning of a Full Feature Phase iSCSI connection is preceded by either a Logout Response PDU, or an Async Message PDU. The Time2Wait and Time2Retain field values (section 9.15) in a Logout Response PDU, and the Parameter2 and Parameter3 fields of an Async Message (AsyncEvent types "drop the connection" or "drop all the con- nections"; section 9.9.1) specify the timeout values to be used in each of these cases. These timeout values are applicable only for the affected connec- tion, and the tasks active on that connection. These timeout values have no bearing on initiator timers (if any) that are already run- ning on connections or tasks associated with that session. 5.5 Implicit termination of tasks A target implicitly terminates the active tasks in three cases due to iSCSI protocol dynamics: a) When a connection is implicitly or explicitly logged out with the Reason code of "Closes the connection" and there are active tasks allegiant to that connection. Julian Satran Expires February 2003 84 iSCSI 5-August-02 b) When a connection fails and eventually the connection state times out (state transition M1 in Section 6.2.2 State Transition Descriptions for Initiators and Targets) and there are active tasks allegiant to that connection. c) When a successful Logout with the reason code of "remove the connection for recovery" is performed while there are active tasks allegiant to that connection, and those tasks eventually time out after the Time2Wait and Time2Retain periods without allegiance reassignment. If the tasks terminated in any of the above cases are SCSI tasks, they must be internally terminated with CHECK CONDITION status with a sense key of unit attention and ASC/ASCQ values of 0x6E/0x00 (COM- MAND TO LOGICAL UNIT FAILED). Note that this status is meaningful only for appropriately handling the internal SCSI state with respect to ordering aspects such as queued commands because this status is never communicated back as a terminating status to the initiator. 5.6 Format Errors The following two explicit violations of PDU layout rules are format errors: a) illegal contents of any PDU header field except the Opcode (legal values are specified in Section 9 iSCSI PDU Formats) b) inconsistent field contents (consistent field contents are specified in Section 9 iSCSI PDU Formats) Format errors indicate a major implementation flaw in one of the par- ties. When a target or an initiator receives an iSCSI PDU with a format error, it MUST immediately terminate all transport connections in the session either with a connection close or with a connection reset and escalate the format error to session recovery (see Section 5.14.4 Session Recovery). 5.7 Digest Errors The discussion of the legal choices in handling digest errors below excludes session recovery as an explicit option, but either party detecting a digest error may choose to escalate the error to session recovery. Julian Satran Expires February 2003 85 iSCSI 5-August-02 When a target or an initiator receives any iSCSI PDU, with a header digest error, it MUST either discard the header and all data up to the beginning of a later PDU or close the connection. Since the digest error indicates that the length field of the header may have been corrupted, the location of the beginning of a later PDU needs to be reliably ascertained by other means (such as the operation of a sync and steering layer). When a target receives any iSCSI PDU with a payload digest error, it MUST answer with a Reject PDU with a Reason-code of Data-Digest-Error and discard the PDU. - If the discarded PDU is a solicited or unsolicited iSCSI data PDU (for immediate data in a command PDU, non-data PDU rule below applies), the target MUST do one of the following: a) Request retransmission with a recovery R2T. b) Terminate the task with a response PDU with a CHECK CONDI- TION Status and an iSCSI Condition of "protocol service CRC error" (Section 9.4.7.2 Sense Data). If the target chooses to implement this option, it MUST wait to receive all the data (signaled by a Data PDU with the final bit set for all outstanding R2Ts) before sending the response PDU. A task management command (such as an abort task) from the initia- tor during this wait may also conclude the task. - No further action is necessary for targets if the discarded PDU is a non-data PDU. In case of immediate data being present on a discarded command, the immediate data is implic- itly recovered when the task is retried (see section 5.2.1) followed by the entire data transfer for the task. When an initiator receives any iSCSI PDU with a payload digest error, it MUST discard the PDU. - If the discarded PDU is an iSCSI data PDU, the initiator MUST do one of the following: a) Request the desired data PDU through SNACK. In response to the SNACK, the target MUST either resend the data PDU or, reject the SNACK with a Reject PDU with a reason-code of "SNACK reject" in which case: i)if the status had not already been sent for the com- mand, the target MUST terminate the command with an CHECK CONDITION Status and an iSCSI Condition of "SNACK rejected" (Section 9.4.7.2 Sense Data). Julian Satran Expires February 2003 86 iSCSI 5-August-02 ii)if the status was already sent, no further action is necessary for the target. The initiator in this case MUST must wait for the status to be received and then discard it, so as to internally signal the completion with CHECK CONDITION Status and an iSCSI Condition of "protocol service CRC error" (Section 9.4.7.2 Sense Data). b) Abort the task and terminate the command with an error. - If the discarded PDU is a response PDU, the initiator MUST do one of the following: a) Request PDU retransmission with a status SNACK. b) Logout the connection for recovery and continue the tasks on a different connection instance as described in Section 5.2 Retry and Reassign in Recovery. c) Logout to close the connection (abort all the commands associated with the connection). - No further action is necessary for initiators if the dis- carded PDU is an unsolicited PDU (e.g., Async, Reject). Task timeouts (as in, the initiator waiting for a command comple- tion), or process timeouts (as in, the target waiting for a Logout) will ensure that the correct operational behavior will result in these cases despite the discarded PDU. 5.8 Sequence Errors When an initiator receives an iSCSI R2T/data PDU with an out of order R2TSN/DataSN or a SCSI response PDU with an ExpDataSN that implies missing data PDU(s), it means that the initiator must have detected a header or payload digest error on one or more earlier R2T/data PDUs. The initiator MUST address these implied digest errors as described in Section 5.7 Digest Errors. When a target receives a data PDU with an out of order DataSN, it means that the target must had hit a header or payload digest error on at least one of the earlier data PDUs. The target MUST address these implied digest errors as described in Section 5.7 Digest Errors. When an initiator receives an iSCSI status PDU with an out of order StatSN that implies missing responses, it MUST address the one or more missing status PDUs as described in Section 5.7 Digest Errors. As a side effect of receiving the missing responses, the initiator may discover missing data PDUs. If the initiator wants to recover the missing data for a command, it MUST NOT acknowledge the received Julian Satran Expires February 2003 87 iSCSI 5-August-02 responses that start from the StatSN of the interested command, until it has completed receiving all the data PDUs of the command. When an initiator receives duplicate R2TSNs (due to proactive retransmission of R2Ts by the target) or duplicate DataSNs (due to proactive SNACKs by the initiator), it MUST discard the duplicates. 5.9 SCSI Timeouts An iSCSI initiator MAY attempt to plug a command sequence gap on the target end (in the absence of an acknowledgement of the command by way of ExpCmdSN) before the ULP timeout by retrying the unacknowl- edged command, as described in Section 5.2 Retry and Reassign in Recovery. On a ULP timeout for a command (that carried a CmdSN of n), if the iSCSI initiator intends to continue the session it MUST abort the command by either using an appropriate Task Management function request for the specific command, or a "close the connection" Logout. When using an ABORT TASK, if the ExpCmdSN is still less than (n+1), the target may see the abort request while missing the original com- mand itself due to one of the following reasons: - The original command was dropped due to digest error. - The connection on which the original command was sent was successfully logged out (on logout, the unacknowledged com- mands issued on the connection being logged out are dis- carded). If the abort request is received and the original command is miss- ing, targets MUST consider the original command with that RefCmdSN to be received and issue a Task Management response with the response code: "Function Complete". This response concludes the task on both ends. 5.10 Negotiation Failures Text request and response sequences, when used to set/negotiate oper- ational parameters, constitute the negotiation/parameter setting. A negotiation failure is considered one or more of the following: - None of the choices or the stated value is acceptable to one negotiating side. - The text request timed out, and possibly terminated. - The text request was answered with a Reject PDU. Julian Satran Expires February 2003 88 iSCSI 5-August-02 The following two rules are to be used to address negotiation fail- ures: - During Login, any failure in negotiation MUST be considered a login process failure and the Login Phase must be termi- nated, and with it, the connection. If the target detects the failure, it must terminate the login with the appropriate login response code. - A failure in negotiation, while in the Full Feature Phase, will terminate the entire negotiation sequence that may con- sist of a series of text requests that use the same Initia- tor Task Tag. The operational parameters of the session or the connection MUST continue to be the values agreed upon during an earlier successful negotiation (i.e., any partial results of this unsuccessful negotiation MUST NOT take effect and be discarded). 5.11 Protocol Errors Mapping framed messages over a "stream" connection, such as TCP, make the proposed mechanisms vulnerable to simple software framing errors. On the other hand, the introduction of framing mechanisms to limit the effects of these errors may be onerous on performance for simple implementations. Command Sequence Numbers and the above mechanisms for connection drop and re-establishment help handle this type of mapping errors. All violations of iSCSI PDU exchange sequences specified in this draft are also protocol errors. This category of errors can only be addressed by fixing the implementations; iSCSI defines Reject and response codes to enable this. 5.12 Connection Failures iSCSI can keep a session in operation if it is able to keep/estab- lish at least one TCP connection between the initiator and the tar- get in a timely fashion. Targets and/or initiators may recognize a failing connection by either transport level means (TCP), a gap in the command sequence number, a response stream that is not filled for a long time, or by a failing iSCSI NOP (acting as a ping). The lat- ter MAY be used periodically to increase the speed and likelihood of detecting connection failures. Initiators and targets MAY also use Julian Satran Expires February 2003 89 iSCSI 5-August-02 the keep-alive option on the TCP connection to enable early link failure detection on otherwise idle links. On connection failure, the initiator and target MUST do one of the following: - Attempt connection recovery within the session (Section 5.14.3 Connection Recovery). - Logout the connection with the reason code "closes the con- nection" (Section 9.14.5 Implicit termination of tasks), re- issue missing commands, and implicitly terminate all active commands. This option requires support for the within-connec- tion recovery class (Section 5.14.2 Recovery Within-connec- tion). - Perform session recovery (Section 5.14.4 Session Recovery). Either side may choose to escalate to session recovery (via the ini- tiator dropping all the connections, or via an Async Message that announces the similar intent from a target), and the other side MUST give it precedence. On a connection failure, a target MUST termi- nate and/or discard all the active immediate commands regardless of which of the above options is used (i.e., immediate commands are not recoverable across connection failures). 5.13 Session Errors If all the connections of a session fail and cannot be re-estab- lished in a short time, or if initiators detect protocol errors repeatedly, an initiator may choose to terminate a session and estab- lish a new session. The initiator takes the following actions in such a case: - It resets or closes all the transport connections. - It terminates all outstanding requests with an appropriate response before initiating a new session. If the same I_T nexus is intended to be re-established, the initiator MUST employ session reinstatement (see section 4.3.5). When the session timeout (the connection state timeout for the last failed connection) happens on the target, it takes the following actions: - Resets or closes the TCP connections (closes the session). - Terminates all active tasks that were allegiant to the con- nection(s) that constituted the session. Julian Satran Expires February 2003 90 iSCSI 5-August-02 A target MUST also be prepared to handle a session reinstatement request from the initiator, who may be addressing session errors. 5.14 Recovery Classes iSCSI enables the following classes of recovery (in the order of increasing scope of affected iSCSI tasks): - Within a command (i.e., without requiring command restart). - Within a connection (i.e., without requiring the connection to be rebuilt, but perhaps requiring command restart). - Connection recovery (i.e., perhaps requiring connections to be rebuilt and commands to be reissued). - Session recovery. The recovery scenarios detailed in the rest of this section are rep- resentative rather than exclusive. In every case, they detail the lowest class recovery that MAY be attempted. The implementer is left to decide under which circumstances to escalate to the next recovery class and/or what recovery classes to implement. Both the iSCSI tar- get and initiator MAY escalate the error handling to an error recov- ery class, which impacts a larger number of iSCSI tasks in any of the cases identified in the following discussion. In all classes, the implementer has the choice of deferring errors to the SCSI initiator (with an appropriate response code), in which case the task, if any, has to be removed from the target and all the side- effects, such as ACA, must be considered. Use of within-connection and within-command recovery classes MUST NOT be attempted before the connection is in Full Feature Phase. In the detailed description of the recover classes the mandating terms (MUST, SHOULD, MAY, etc.) indicate normative actions to be exe- cute if the recovery class is supported and used. 5.14.1 Recovery Within-command At the target, the following cases lend themselves to within-command recovery: - Lost data PDU - realized through one of the following: a) Data digest error - dealt with as specified in Section 5.7 Digest Errors, using the option of a recovery R2T. Julian Satran Expires February 2003 91 iSCSI 5-August-02 b) Sequence reception timeout (no data or partial-data-and-no-F- bit) - considered an implicit sequence error and dealt with as specified in Section 5.8 Sequence Errors, using the option of a recovery R2T. c) Header digest error, which manifests as a sequence reception timeout, or a sequence error - dealt with as specified in Section 5.8 Sequence Errors, using the option of a recovery R2T. At the initiator, the following cases lend themselves to within-com- mand recovery: Lost data PDU or lost R2T - realized through one of the follow- ing: a) Data digest error - dealt with as specified in Section 5.7 Digest Errors, using the option of a SNACK. b) Sequence reception timeout (no status) or response reception timeout - dealt with as specified in Section 5.8 Sequence Errors, using the option of a SNACK. c) Header digest error, which manifests as a sequence reception timeout, or a sequence error - dealt with as specified in Section 5.8 Sequence Errors, using the option of a SNACK. To avoid a race with the target, which may already have a recovery R2T or a termination response on its way, an initiator SHOULD NOT originate a SNACK for an R2T based on its internal timeouts (if any). Recovery in this case is better left to the target. The timeout values used by the initiator and target are outside the scope of this document. Sequence reception timeout is generally a large enough value to allow the data sequence transfer to be com- plete. 5.14.2 Recovery Within-connection At the initiator, the following cases lend themselves to within-con- nection recovery: - Requests not acknowledged for a long time. Requests are acknowledged explicitly through ExpCmdSN or implicitly by receiving data and/or status. The initiator MAY retry non- acknowledged commands as specified in Section 5.2 Retry and Reassign in Recovery. - Lost iSCSI numbered Response. It is recognized by either identifying a data digest error on a Response PDU or a Data- Julian Satran Expires February 2003 92 iSCSI 5-August-02 In PDU carrying the status, or by receiving a Response PDU with a higher StatSN than expected. In the first case, digest error handling is done as specified in Section 5.7 Digest Errors using the option of a SNACK. In the second case, sequence error handling is done as specified in Section 5.8 Sequence Errors, using the option of a SNACK. At the target, the following cases lend themselves to within-connec- tion recovery: - Status/Response not acknowledged for a long time. The target MAY issue a NOP-IN (with a valid Target Transfer Tag or oth- erwise) that carries the next status sequence number it is going to use in the StatSN field. This helps the initiator detects any missing StatSN(s) and issue a SNACK for the sta- tus. The timeout values used by the initiator and the target are outside the scope of this document. 5.14.3 Connection Recovery At an iSCSI initiator, the following cases lend themselves to connec- tion recovery: - TCP connection failure: The initiator MUST close the connec- tion. It then MUST either implicitly or explicitly Logout the failed connection with the reason code "remove the connec- tion for recovery" and reassign connection allegiance for all commands still in progress associated with the failed connec- tion on one or more connections (some or all of whom MAY be newly established connections) using the "Task reassign" task management function (see Section 9.5.1 Function). Note that for an initiator a command is in progress as long as it has not received a response or a Data-In PDU including status. Note. The logout function is mandatory, while a new connec- tion establishment is mandatory only if the failed connec- tion was the last or only connection in the session. - Receiving an Asynchronous Message that indicates one or all connections in a session has been dropped. The initiator MUST handle it as a TCP connection failure for the connec- tion(s) referred to in the Message. At an iSCSI target, the following cases lend themselves to connec- tion recovery: Julian Satran Expires February 2003 93 iSCSI 5-August-02 - TCP connection failure. The target MUST close the connection and if more than one connection is available, the target SHOULD send an Asynchronous Message that indicates it has dropped the connection. Then, the target will wait for the initiator to continue recovery. 5.14.4 Session Recovery Session recovery should be performed when all other recovery attempts have failed. Very simple initiators and targets MAY perform session recovery on all iSCSI errors and rely on recovery on the SCSI layer and above. Session recovery implies the closing of all TCP connections, inter- nally aborting all executing and queued tasks for the given initia- tor at the target, terminating all outstanding SCSI commands with an appropriate SCSI service response at the initiator, and restarting a session on a new set of connection(s) (TCP connection establishment and login on all new connections). For possible clearing effects of session recovery on SCSI and iSCSI objects, refer to Appendix F. - Clearing effects of various events on targets -. 5.15 Error Recovery Hierarchy The error recovery classes and features described thus far are orga- nized into a hierarchy for ease in understanding and to limit the myriad of implementation possibilities, with hopes that this signifi- cantly contributes to highly interoperable implementations. The attributes of this hierarchy are as follows: a) Each level is a superset of the capabilities of the previous level. For example, Level 1 support implies supporting all capa- bilities of Level 0 and more. b) As a corollary, supporting a higher error recovery level means increased sophistication and possibly an increase in resource requirements. c) Supporting error recovery level "n" is advertised and negoti- ated by each iSCSI entity by exchanging the text key "ErrorRecov- eryLevel=n". The lower of the two exchanged values is the operational ErrorRecoveryLevel for the session. The following diagram represents the error recovery hierarchy. Julian Satran Expires February 2003 94 iSCSI 5-August-02 + / \ / 2 \ <-- Connection recovery +-----+ / 1 \ <-- Digest failure recovery +---------+ / 0 \ <-- Session failure recovery +-------------+ The following table lists the error recovery capabilities expected from the implementations that support each error recovery level. +-------------------+--------------------------------------------+ |ErrorRecoveryLevel | Associated Error recovery capabilities | +-------------------+--------------------------------------------+ | 0 | Session recovery class | | | (Section 5.14.4 Session Recovery) | +-------------------+--------------------------------------------+ | 1 | Digest failure recovery (See Note below.) | +-------------------+--------------------------------------------+ | 2 | Connection recovery class | | | (Section 5.14.3 Connection Recovery) | +-------------------+--------------------------------------------+ Note: Digest failure recovery is comprised of two recovery classes: Within-Connection recovery class (Section 5.14.2 Recovery Within-con- nection) and Within-Command recovery class (Section 5.14.1 Recovery Within-command). When a defined value of ErrorRecoveryLevel is proposed by an origina- tor in a text negotiation, the originator MUST support the function- ality defined for the proposed value and additionally, functionality corresponding to any defined value numerically less than the pro- posed. When a defined value of ErrorRecoveryLevel is returned by a responder in a text negotiation, the responder MUST support the func- tionality corresponding to the ErrorRecoveryLevel it is accepting. When either party attempts to use error recovery functionality beyond what is negotiated, the recovery attempts MAY fail unless an apriori agreement outside the scope of this document exists between the two parties to provide such support. Julian Satran Expires February 2003 95 iSCSI 5-August-02 Supporting error recovery level "0" is mandatory, while the rest are optional to implement. In implementation terms, the above striation means that the following incremental sophistication with each level is required. +-------------------+---------------------------------------------+ |Level transition | Incremental requirement | +-------------------+---------------------------------------------+ | 0->1 | PDU retransmissions on the same connection | +-------------------+---------------------------------------------+ | 1->2 | Retransmission across connections and | | | allegiance reassignment | +-------------------+---------------------------------------------+ Julian Satran Expires February 2003 96 iSCSI 5-August-02 6. State Transitions iSCSI connections and iSCSI sessions go through several well-defined states from the time they are created to the time they are cleared. The connection state transitions are described in two separate but dependent state diagrams for ease in understanding. The first dia- gram, "standard connection state diagram", describes the connection state transitions when the iSCSI connection is not waiting for or undergoing a cleanup by way of an explicit or implicit Logout. The second diagram, "connection cleanup state diagram", describes the connection state transitions while performing the iSCSI connection cleanup. The "session state diagram" describes the state transitions an iSCSI session would go through during its lifetime, and it depends on the states of possibly multiple iSCSI connections that participate in the session. 6.1 Standard Connection State Diagrams 6.1.1 State Descriptions for Initiators and Targets State descriptions for the standard connection state diagram are as follows: -S1: FREE -initiator: State on instantiation, or after successful con- nection closure. -target: State on instantiation, or after successful connec- tion closure. -S2: XPT_WAIT -initiator: Waiting for a response to its transport connec- tion establishment request. -target: Illegal -S3: XPT_UP -initiator: Illegal -target: Waiting for the Login process to commence. -S4: IN_LOGIN -initiator: Waiting for the Login process to conclude, possi- bly involving several PDU exchanges. -target: Waiting for the Login process to conclude, possibly involving several PDU exchanges. -S5: LOGGED_IN Julian Satran Expires February 2003 97 iSCSI 5-August-02 -initiator: In Full Feature Phase, waiting for all internal, iSCSI, and transport events. -target: In Full Feature Phase, waiting for all internal, iSCSI, and transport events. -S6: IN_LOGOUT -initiator: Waiting for a Logout response. -target: Waiting for an internal event signaling completion of logout processing. -S7: LOGOUT_REQUESTED -initiator: Waiting for an internal event signaling readi- ness to proceed with Logout. -target: Waiting for the Logout process to start after hav- ing requested a Logout via an Async Message. -S8: CLEANUP_WAIT -initiator: Waiting for the context and/or resources to ini- tiate the cleanup processing for this CSM. -target: Waiting for the cleanup process to start for this CSM. 6.1.2 State Transition Descriptions for Initiators and Targets -T1: -initiator: Transport connect request was made (ex: TCP SYN sent). -target: Illegal -T2: -initiator: Transport connection request timed out, or a transport reset was received, or an internal event of receiving a Logout response (success) on another connection for a "close the session" Logout request was received. -target:Illegal -T3: -initiator: Illegal -target: Received a valid transport connection request that establishes the transport connection. -T4: -initiator: Transport connection established, thus prompting the initiator to start the iSCSI Login. -target: Initial iSCSI Login request was received. -T5: -initiator: The final iSCSI Login response with a Status- Class of zero was received. Julian Satran Expires February 2003 98 iSCSI 5-August-02 -target: The final iSCSI Login request to conclude the Login Phase was received, thus prompting the target to send the final iSCSI Login response with a Status-Class of zero. -T6: -initiator: Illegal -target: Timed out waiting for an iSCSI Login, or transport disconnect indication was received, or transport reset was received, or an internal event indicating a transport time- out was received. In all these cases, the connection is to be closed. -T7: -initiator - one of the following evens caused the transi- tion: - The final iSCSI Login response was received with a non- zero Status-Class - Login timed out - A transport disconnect indication was received - A transport reset was received - An internal event indicating a transport timeout was received - An internal event of receiving a Logout response (suc- cess) on another connection for a "close the session" Logout request was received. In all these cases, the transport connection is closed. -target - one of the following events caused the transition: - The final iSCSI Login request to conclude the Login Phase was received, prompting the target to send the final iSCSI Login response with a non-zero Status-Class - Login timed out - Transport disconnect indication was received - Transport reset was received - An internal event indicating a transport timeout was received - On another connection a "close the session" Logout request was received. In all these cases, the connection is to be closed. -T8: -initiator: An internal event of receiving a Logout response (success) on another connection for a "close the session" Julian Satran Expires February 2003 99 iSCSI 5-August-02 Logout request was received, thus closing this connection requiring no further cleanup. -target: An internal event of sending a Logout response (suc- cess) on another connection for a "close the session" Logout request was received, or an internal event of a successful connection/session reinstatement is received, thus prompt- ing the target to close this connection cleanly. -T9, T10: -initiator: An internal event that indicates the readiness to start the Logout process was received, thus prompting an iSCSI Logout to be sent by the initiator. -target: An iSCSI Logout request was received. -T11, T12: -initiator: Async PDU with AsyncEvent "Request Logout" was received. -target: An internal event that requires the decommissioning of the connection is received, thus causing an Async PDU with an AsyncEvent "Request Logout" to be sent. -T13: -initiator: An iSCSI Logout response (success) was received, or an internal event of receiving a Logout response (suc- cess) on another connection for a "close the session" Logout request was received. -target: An internal event was received that indicates suc- cessful processing of the Logout, which prompts an iSCSI Logout response (success) to be sent, or an internal event of sending a Logout response (success) on another connec- tion for a "close the session" Logout request was received, or an internal event of a successful connection/session reinstatement is received. In all these cases, the trans- port connection is closed. -T14: -initiator: Async PDU with AsyncEvent "Request Logout" was received again. -target: Illegal -T15, T16: -initiator: One or more of the following events caused this transition: -Internal event that indicates a transport connection tim- eout was received thus prompting transport RESET or trans- port connection closure. -A transport RESET. Julian Satran Expires February 2003 100 iSCSI 5-August-02 -A transport disconnect indication. -Async PDU with AsyncEvent "Drop connection" (for this CID). -Async PDU with AsyncEvent "Drop all connections". -target: One or more of the following events caused this transition: -Internal event that indicates a transport connection tim- eout was received, thus prompting transport RESET or trans- port connection closure. -An internal event of a failed connection/session rein- statement is received. -A transport RESET. -A transport disconnect indication. -Internal emergency cleanup event was received which prompts an Async PDU with AsyncEvent "Drop connection" (for this CID), or event "Drop all connections". -T17: -initiator: One or more of the following events caused this transition: -Logout response (failure, i.e. a non-zero status) was received, or Logout timed out. -Any of the events specified for T15 and T16. -target: One or more of the following events caused this transition: -Internal event that indicates a failure of the Logout processing was received, which prompts a Logout response (failure, i.e. a non-zero status) to be sent. -Any of the events specified for T15 and T16. -T18: -initiator: An internal event of receiving a Logout response (success) on another connection for a "close the session" Logout request was received. -target: An internal event of sending a Logout response (suc- cess) on another connection for a "close the session" Logout request was received, or an internal event of a suc- cessful connection/session reinstatement is received. In both these cases, the connection is closed. Julian Satran Expires February 2003 101 iSCSI 5-August-02 The CLEANUP_WAIT state (S8) implies that there are possible iSCSI tasks that have not reached conclusion and are still considered busy. 6.1.3 Standard Connection State Diagram for an Initiator Symbolic names for States: S1: FREE S2: XPT_WAIT S4: IN_LOGIN S5: LOGGED_IN S6: IN_LOGOUT S7: LOGOUT_REQUESTED S8: CLEANUP_WAIT States S5, S6 and S7 constitute the Full Feature Phase operation of the connection. The state diagram is as follows: Julian Satran Expires February 2003 102 iSCSI 5-August-02 -------<-------------+ +--------->/ S1 \<----+ | T13| +->\ /<-+ \ | | / ---+--- \ \ | | / | T2 \ | | | T8 | |T1 | | | | | | / |T7 | | | | / | | | | | / | | | | V / / | | | ------- / / | | | / S2 \ / | | | \ / / | | | ---+--- / | | | |T4 / | | | V / | T18 | | ------- / | | | / S4 \ | | | \ / | | | ---+--- | T15 | | |T5 +--------+---------+ | | | /T16+-----+------+ | | | | / -+-----+--+ | | | | | / / S7 \ |T12| | | | | / +->\ /<-+ V V | | | / / -+----- ------- | | | / /T11 |T10 / S8 \ | | V / / V +----+ \ / | | ---+-+- ----+-- | ------- | | / S5 \T9 / S6 \<+ ^ | +-----\ /--->\ / T14 | | ------- --+----+------+T17 +---------------------------+ The following state transition table represents the above diagram. Each row represents the starting state for a given transition, which after taking a transition marked in a table cell would end in the state represented by the column of the cell. For example, from state S1, the connection takes the T1 transition to arrive at state S2. The fields marked "-" correspond to undefined transitions. Julian Satran Expires February 2003 103 iSCSI 5-August-02 +-----+---+---+---+---+----+---+ |S1 |S2 |S4 |S5 |S6 |S7 |S8 | ---+-----+---+---+---+---+----+---+ S1| - |T1 | - | - | - | - | - | ---+-----+---+---+---+---+----+---+ S2|T2 |- |T4 | - | - | - | - | ---+-----+---+---+---+---+----+---+ S4|T7 |- |- |T5 | - | - | - | ---+-----+---+---+---+---+----+---+ S5|T8 |- |- | - |T9 |T11 |T15| ---+-----+---+---+---+---+----+---+ S6|T13 |- |- | - |T14|- |T17| ---+-----+---+---+---+---+----+---+ S7|T18 |- |- | - |T10|T12 |T16| ---+-----+---+---+---+---+----+---+ S8| - |- |- | - | - | - | - | ---+-----+---+---+---+---+----+---+ 6.1.4 Standard Connection State Diagram for a Target Symbolic names for States: S1: FREE S3: XPT_UP S4: IN_LOGIN S5: LOGGED_IN S6: IN_LOGOUT S7: LOGOUT_REQUESTED S8: CLEANUP_WAIT States S5, S6 and S7 constitute the Full Feature Phase operation of the connection. The state diagram is as follows: Julian Satran Expires February 2003 104 iSCSI 5-August-02 -------<-------------+ +--------->/ S1 \<----+ | T13| +->\ /<-+ \ | | / ---+--- \ \ | | / | T6 \ | | | T8 | |T3 | | | | | | / |T7 | | | | / | | | | | / | | | | V / / | | | ------- / / | | | / S3 \ / | | | \ / / | T18 | | ---+--- / | | | |T4 / | | | V / | | | ------- / | | | / S4 \ | | | \ / | | | ---+--- T15 | | | |T5 +--------+---------+ | | | /T16+-----+------+ | | | | / -+-----+---+ | | | | | / / S7 \ |T12| | | | | / +->\ /<-+ V V | | | / / -+----- ------- | | | / /T11 |T10 / S8 \ | | V / / V \ / | | ---+-+- ------- ------- | | / S5 \T9 / S6 \ ^ | +-----\ /--->\ / | | ------- --+----+--------+T17 +---------------------------+ The following state transition table represents the above diagram, and follows the conventions described for the initiator diagram. Julian Satran Expires February 2003 105 iSCSI 5-August-02 +-----+---+---+---+---+----+---+ |S1 |S3 |S4 |S5 |S6 |S7 |S8 | ---+-----+---+---+---+---+----+---+ S1| - |T3 | - | - | - | - | - | ---+-----+---+---+---+---+----+---+ S3|T6 |- |T4 | - | - | - | - | ---+-----+---+---+---+---+----+---+ S4|T7 |- |- |T5 | - | - | - | ---+-----+---+---+---+---+----+---+ S5|T8 |- |- | - |T9 |T11 |T15| ---+-----+---+---+---+---+----+---+ S6|T13 |- |- | - |- |- |T17| ---+-----+---+---+---+---+----+---+ S7|T18 |- |- | - |T10|T12 |T16| ---+-----+---+---+---+---+----+---+ S8| - |- |- | - | - | - | - | ---+-----+---+---+---+---+----+---+ 6.2 Connection Cleanup State Diagram for Initiators and Targets Symbolic names for states: R1: CLEANUP_WAIT (same as S8) R2: IN_CLEANUP R3: FREE (same as S1) Whenever a connection state machine (e.g., CSM-C) enters the CLEANUP_WAIT state (S8), it must go through the state transitions additionally described in the connection cleanup state diagram either a) using a separate full-feature phase connection (let's call it CSM- E) in the LOGGED_IN state in the same session, or b) using a new transport connection (let's call it CSM-I) in the FREE state that is to be added to the same session. In the CSM-E case, an explicit logout for the CID that corresponds to CSM-C (either as a connection or session logout) needs to be performed to complete the cleanup. In the CSM-I case, an implicit logout for the CID that corresponds to CSM-C needs to be performed by way of connection reinstatement (sec- tion 4.3.4) for that CID. In either case, the protocol exchanges on CSM-E or CSM-I determine the state transitions for CSM-C. Therefore, this cleanup state diagram is applicable only to the instance of the connection in cleanup (i.e., CSM-C). In the case of an implicit logout for example, CSM-C reaches FREE (R3) at the time CSM-I reaches LOGGED_IN. In the case of an explicit logout, CSM-C reaches FREE (R3) Julian Satran Expires February 2003 106 iSCSI 5-August-02 when CSM-E receives a successful logout response while continuing to be in the LOGGED_IN state. An initiator must initiate an explicit or implicit connection logout for a connection in the CLEANUP_WAIT state, if the initiator intends to continue using the associated iSCSI session. The following state diagram applies to both initiators and targets. ------- / R1 \ +--\ /<-+ / ---+--- \ / | \ M3 M1 | |M2 | | | / | | / | | / | V / | ------- / | / R2 \ | \ / | ------- | | | |M4 | | | | | | | V | ------- | / R3 \ +---->\ / ------- The following state transition table represents the above diagram, and follows the same conventions as in earlier sections. Julian Satran Expires February 2003 107 iSCSI 5-August-02 +----+----+----+ |R1 |R2 |R3 | -----+----+----+----+ R1 | - |M2 |M1 | -----+----+----+----+ R2 |M3 | - |M4 | -----+----+----+----+ R3 | - | - | - | -----+----+----+----+ 6.2.1 State Descriptions for Initiators and Targets -R1: CLEANUP_WAIT (Same as S8) -initiator: Waiting for the internal event to initiate the cleanup processing for CSM-C. -target: Waiting for the cleanup process to start for CSM-C. -R2: IN_CLEANUP -initiator: Waiting for the connection cleanup process to conclude for CSM-C. -target: Waiting for the connection cleanup process to con- clude for CSM-C. -R3: FREE (Same as S1) -initiator: End state for CSM-C. -target: End state for CSM-C. 6.2.2 State Transition Descriptions for Initiators and Targets -M1: One or more of the following events was received: -initiator: -An internal event that indicates connection state time- out. -An internal event of receiving a successful Logout response on a different connection for a "close the session" Logout. -target: -An internal event that indicates connection state time- out. -An internal event of sending a Logout response (success) on a different connection for a "close the session" Logout request. -M2: An implicit/explicit logout process was initiated by the initi- ator. -In CSM-I usage: Julian Satran Expires February 2003 108 iSCSI 5-August-02 -initiator: An internal event requesting the connection (or session) reinstatement was received, thus prompting a connection (or session) reinstatement Login to be sent tran- sitioning CSM-I to state IN_LOGIN. -target: A connection/session reinstatement Login was received while in state XPT_UP. -In CSM-E usage: -initiator: An internal event that indicates that an explicit logout was sent for this CID in state LOGGED_IN. -target: An explicit logout was received for this CID in state LOGGED_IN. -M3: Logout failure detected -In CSM-I usage: -initiator: CSM-I failed to reach LOGGED_IN and arrived into FREE instead. -target: CSM-I failed to reach LOGGED_IN and arrived into FREE instead. -In CSM-E usage: -initiator: CSM-E either moved out of LOGGED_IN, or Logout timed out and/or aborted, or Logout response (failure) was received. -target: CSM-E either moved out of LOGGED_IN, or Logout timed out and/or aborted, or an internal event that indicates a failed Logout processing was received. A Logout response (failure) was sent in the last case. -M4: Successful implicit/explicit logout was performed. - In CSM-I usage: -initiator: CSM-I reached state LOGGED_IN, or an internal event of receiving a Logout response (success) on another connection for a "close the session" Logout request was received. -target: CSM-I reached state LOGGED_IN, or an internal event of sending a Logout response (success) on a different connection for a "close the session" Logout request was received. - In CSM-E usage: -initiator: CSM-E stayed in LOGGED_IN and received a Logout response (success), or an internal event of receiving a Logout response (success) on another connection for a "close the session" Logout request was received. Julian Satran Expires February 2003 109 iSCSI 5-August-02 -target: CSM-E stayed in LOGGED_IN and an internal event indicating a successful Logout processing was received, or an internal event of sending a Logout response (success) on a different connection for a "close the session" Logout request was received. 6.3 Session State Diagrams Session State Diagram for an Initiator Symbolic Names for States: Q1: FREE Q3: LOGGED_IN Q4: FAILED State Q3 represents the Full Feature Phase operation of the session. The state diagram is as follows: ------- / Q1 \ +------>\ /<-+ / ---+--- | / | |N3 N6 | |N1 | | | | | N4 | | | +--------+ | / | | | | / | | | | / | | V V / -+--+-- -----+- / Q4 \ N5 / Q3 \ \ /<---\ / ------- ------- State transition table: Julian Satran Expires February 2003 110 iSCSI 5-August-02 +----+----+----+ |Q1 |Q3 |Q4 | -----+----+----+----+ Q1 | - |N1 | - | -----+----+----+----+ Q3 |N3 | - |N5 | -----+----+----+----+ Q4 |N6 |N4 | - | -----+----+----+----+ 6.3.1 Session State Diagram for a Target Symbolic Names for States: Q1: FREE Q2: ACTIVE Q3: LOGGED_IN Q4: FAILED Q5: IN_CONTINUE State Q3 represents the Full Feature Phase operation of the session. The state diagram is as follows: Julian Satran Expires February 2003 111 iSCSI 5-August-02 ------- +------------------>/ Q1 \ / +-------------->\ /<-+ | | ---+--- | | | ^ | |N3 N6 | |N11 N9| V N1 | | | +------ | | | / Q2 \ | | | \ / | | --+---- +--+--- | | / Q5 \ | | | \ / N10 | | | +-+---+------------+ |N2 / | ^ | | | / |N7| |N8 | | / | | | | V / -+--+-V V----+- / Q4 \ N5 / Q3 \ \ /<-------------\ / ------- ------- State transition table: +----+----+----+----+----+ |Q1 |Q2 |Q3 |Q4 |Q5 | -----+----+----+----+----+----+ Q1 | - |N1 | - | - | - | -----+----+----+----+----+----+ Q2 |N9 | - |N2 | - | - | -----+----+----+----+----+----+ Q3 |N3 | - | - |N5 | - | -----+----+----+----+----+----+ Q4 |N6 | - | - | - |N7 | -----+----+----+----+----+----+ Q5 |N11 | - |N10 |N8 | - | -----+----+----+----+----+----+ 6.3.2 State Descriptions for Initiators and Targets -Q1: FREE -initiator: State on instantiation or after cleanup. -target: State on instantiation or after cleanup. Julian Satran Expires February 2003 112 iSCSI 5-August-02 -Q2: ACTIVE -initiator: Illegal -target: The first iSCSI connection in the session transi- tioned to IN_LOGIN, waiting for it to complete the login process. -Q3: LOGGED_IN -initiator: Waiting for all session events. -target: Waiting for all session events. -Q4: FAILED -initiator: Waiting for session recovery or session continua- tion. -target: Waiting for session recovery or session continua- tion. -Q5: IN_CONTINUE -initiator: Illegal -target: Waiting for session continuation attempt to reach a conclusion. 6.3.3 State Transition Descriptions for Initiators and Targets -N1: -initiator: At least one transport connection reached the LOGGED_IN state. -target: The first iSCSI connection in the session had reached the IN_LOGIN state. -N2: -initiator: Illegal -target: At least one iSCSI connection reached the LOGGED_IN state. -N3: -initiator: Graceful closing of the session via session clo- sure (Section 4.3.6 Session continuation and failure). -target: Graceful closing of the session via session closure (Section 4.3.6 Session continuation and failure). Or a suc- cessful session reinstatement cleanly closed the session. -N4: -initiator: A session continuation attempt succeeded. -target: Illegal -N5: -initiator: Session failure (Section 4.3.6 Session continua- tion and failure) occurred. Julian Satran Expires February 2003 113 iSCSI 5-August-02 -target: Session failure (Section 4.3.6 Session continuation and failure) occurred. -N6: -initiator: Session state timeout occurred, or a session reinstatement cleared this session instance. This results in the freeing of all associated resources and the session state is discarded. -target: Session state timeout occurred, or a session rein- statement cleared this session instance. This results in the freeing of all associated resources and the session state is discarded. -N7: -initiator: Illegal -target: A session continuation attempt is initiated. -N8: -initiator: Illegal -target: The last session continuation attempt failed. -N9: -initiator: Illegal -target: Login attempt on the leading connection failed. -N10: -initiator: Illegal -target: A session continuation attempt succeeded. -N11: -initiator: Illegal -target: A successful session reinstatement cleanly closed the session. Julian Satran Expires February 2003 114 iSCSI 5-August-02 7. Security Considerations Historically, native storage systems have not had to consider secu- rity because their environments offered minimal security risks. That is, these environments consisted of storage devices either directly attached to hosts or connected via a Storage Area Network (SAN) dis- tinctly separate from the communications network. The use of storage protocols, such as SCSI, over IP-networks requires that security con- cerns be addressed. iSCSI implementations MUST provide means of pro- tection against active attacks (e.g., pretending to be another identity, message insertion, deletion, modification, and replaying) and passive attacks (e.g.,eavesdropping, gaining advantage by analyz- ing the data sent over the line). Although technically possible, iSCSI SHOULD NOT be configured with- out security. iSCSI configured without security should be confined, in extreme cases, to closed environments without any security risk. The following section describes the security mechanisms provided by an iSCSI implementation. 7.1 iSCSI Security Mechanisms The entities involved in iSCSI security are the initiator, target, and the IP communication end points. iSCSI scenarios where multiple initiators or targets share a single communication end point are expected. To accommodate such scenarios, iSCSI uses two separate security mechanisms: In-band authentication between the initiator and the target at the iSCSI connection level (carried out by exchange of iSCSI Login PDUs), and packet protection (integrity, authentication, and confidentiality) by IPsec at the IP level. The two security mech- anisms complement each other: The in-band authentication provides end-to-end trust (at login time) between the iSCSI initiator and the target, while IPsec provides a secure channel between the IP communi- cation end points. Further details on typical iSCSI scenarios and the relation between the initiators, targets, and the communication end points can be found in [SEC-IPS]. Julian Satran Expires February 2003 115 iSCSI 5-August-02 7.2 In-band Initiator-Target Authentication During login the target MUST authenticate the initiator and the ini- tiator MAY authenticate the target. The authentication is performed on every new iSCSI connection by an exchange of iSCSI Login PDUs using a negotiated authentication method. The authentication method cannot assume an underlying IPsec protec- tion, because IPsec is optional to use. An attacker should gain as little advantage as possible by inspecting the authentication phase PDUs. Therefore, a method using clear text (or equivalent) passwords is not acceptable; on the other hand, identity protection is not strictly required. The authentication mechanism protects against an unauthorized login to storage resources by using a false identity (spoofing). Once the authentication phase is completed, if the underlying IPsec is not used, all PDUs are sent and received in clear. The authentication mechanism alone (without underlying IPsec) should only be used when there is no risk of eavesdropping, message insertion, deletion, modi- fication, and replaying. Section 10 iSCSI Security Keys and Authentication Methods defines several authentication methods and the exact steps that must be fol- lowed in each of them, including the keys and their allowed values in each step. Whenever an iSCSI initiator gets a response whose keys, or their values, are not according to the step definition, it MUST abort the connection. Whenever an iSCSI target gets a response whose keys, or their values, are not according to the step definition, it MUST answer with a Login reject with the "Initiator Error" or "Missing Parameter" status (these statuses are not intended for cryptographi- cally incorrect value, e.g., the CHAP response, for which "Authenti- cation Failure" status MUST be specified). The importance of this rule can be illustrated in CHAP with target authentication (Section 10.1.4 Challenge Handshake Authentication Protocol (CHAP)) where the initiator would have been able to conduct a reflection attack by omitting his response key (CHAP_R), using the same CHAP challenge as the target and reflecting the target's response back to the target. In CHAP this is prevented since the target must answer the missing CHAP_R key with a Login reject with the "Missing Parameter" status. Julian Satran Expires February 2003 116 iSCSI 5-August-02 7.2.1 CHAP Considerations Compliant iSCSI initiators and targets MUST implement the CHAP authentication method [RFC1994] (according to Section 10.1.4 Chal- lenge Handshake Authentication Protocol (CHAP) including the target authentication option). When CHAP is performed over a non-encrypted channel, it is vulnera- ble to an off-line dictionary attack. Implementations MUST support use of up to 128 bits random CHAP secrets, including the means to generate such secrets and to accept them from an external generation source. Implementations MUST NOT provide secret generation (or expan- sion) means other than random generation. An administrative entity of an environment in which CHAP is used with a secret that has less than 96 random bits MUST enforce IPsec encryp- tion (according to the implementation requirements in Section 7.3.2 Confidentiality) to protect the connection. Moreover, in this case IKE authentication with group pre-shared keys SHOULD NOT be used unless it is not essential to protect group members against off-line dictionary attacks by other members. A compliant implementation SHOULD NOT continue with the login step in which it should send a CHAP response (CHAP_R - Section 10.1.4 Chal- lenge Handshake Authentication Protocol (CHAP)) unless it can verify that either the CHAP secret is at least 96 bits, or that IPsec encryption is being used to protect the connection. Originators MUST NOT reuse the CHAP challenge sent by the Responder for the other direction of a bidirectional authentication. Respond- ers MUST check for this condition and close the iSCSI TCP connection if it occurs. 7.2.2 SRP Considerations The strength of the SRP authentication method (specified in [RFC2945]) is dependent on the characteristics of the group being used (i.e., the prime modulus N and generator g). As described in [RFC2945], N is required to be a Sophie-German prime (of the form N = 2q + 1, where q is also prime) and the generator g is a primitive root of GF(n). In iSCSI authentication, the prime modulus N MUST be at least 768 bits. The list of allowed SRP groups is provided in [SEC-IPS]. Julian Satran Expires February 2003 117 iSCSI 5-August-02 7.3 IPsec The IPsec mechanism is used by iSCSI for packet protection (crypto- graphic integrity, authentication, and confidentiality) at the IP level between the iSCSI communicating end points. The following sec- tions describe the IPsec protocols that must be implemented for data integrity and authentication, confidentiality, and key management. An iSCSI initiator or target may provide the required IPsec support either fully integrated or in conjunction with an IPsec front-end device. In the latter case, the compliance requirements with regard to IPsec support apply to the "combined device" and only the "com- bined device" is to be considered an iSCSI device. Detailed considerations and recommendations for using IPsec for iSCSI are provided in [SEC-IPS]. 7.3.1 Data Integrity and Authentication Data authentication and integrity is provided by a keyed Message Authentication Code in every sent packet. This code protects against message insertion, deletion, and modification. Protection against message replay is realized by using a sequence counter. An iSCSI compliant initiator or target MUST provide data integrity and authentication by implementing IPsec [RFC2401] with ESP [RFC2406] in tunnel mode and MAY provide data integrity and authentication by implementing IPsec with ESP in transport mode. The IPsec implementa- tion MUST fulfill the following iSCSI specific requirements: - HMAC-SHA1 MUST be implemented [RFC2404]. - AES CBC MAC with XCBC extensions SHOULD be implemented [AESCBC]. The ESP anti-replay service MUST also be implemented. At the high speeds iSCSI is expected to operate, a single IPsec SA could rapidly cycle through the 32-bit IPsec sequence number space. In view of this, in the future it may be desirable for an iSCSI implementation that operates at speeds of 1 Gbps or faster to imple- ment the IPsec sequence number extension [SEQ-EXT]. Julian Satran Expires February 2003 118 iSCSI 5-August-02 7.3.2 Confidentiality Confidentiality is provided by encrypting the data in every packet. When confidentiality is used it MUST be accompanied by data integ- rity and authentication to provide comprehensive protection against eavesdropping, message insertion, deletion, modification, and replay- ing. An iSCSI compliant initiator or target MUST provide confidentiality by implementing IPsec [RFC2401] with ESP [RFC2406] in tunnel mode and MAY provide confidentiality by implementing IPsec with ESP in trans- port mode. with the following iSCSI specific requirements: - 3DES in CBC mode MUST be implemented [RFC2451]. - AES in Counter mode SHOULD be implemented [AESCTR]. DES in CBC mode SHOULD NOT be used due to its inherent weakness. The NULL encryption algorithm MUST also be implemented. 7.3.3 Policy, Security Associations and Key Management A compliant iSCSI implementation MUST meet the key management requirements of the IPsec protocol suite. Authentication, security association negotiation, and key management MUST be provided by implementing IKE [RFC2409] using the IPsec DOI [RFC2407] with the following iSCSI specific requirements: - Peer authentication using a pre-shared key MUST be sup- ported. Certificate-based peer authentication using digital signatures MAY be supported. Peer authentication using the public key encryption methods outlined in IKE sections 5.2 and 5.3[7] SHOULD NOT be used. - When digital signatures are used to achieve authentication, an IKE negotiator SHOULD use IKE Certificate Request Pay- load(s) to specify the certificate authority. IKE negotia- tors SHOULD check the pertinent Certificate Revocation List (CRL) before accepting a PKI certificate for use in IKE authentication procedures. - Conformant iSCSI implementations MUST support IKE Main Mode and SHOULD support Aggressive Mode. IKE main mode with pre- shared key authentication method SHOULD NOT be used when either the initiator or the target uses dynamically assigned IP addresses. While pre-shared keys in many cases offer good security, situations where dynamically assigned addresses are Julian Satran Expires February 2003 119 iSCSI 5-August-02 used force the use of a group pre-shared key, which creates vulnerability to a man-in-the-middle attack. - In the IKE Phase 2 Quick Mode exchanges for creating the Phase 2 SA, the Identity Payload fields MUST be present. ID_IPV4_ADDR, ID_IPV6_ADDR (if the protocol stack supports IPv6) and ID_FQDN Identity payloads MUST be supported; ID_USER_FQDN SHOULD be supported. The IP Subnet, IP Address Range, ID_DER_ASN1_DN, ID_DER_ASN1_GN formats SHOULD NOT be used. The ID_KEY_ID Identity Payload MUST NOT be used. Manual keying MUST NOT be used because it does not provide the neces- sary re-keying support. When IPsec is used the receipt of an IKE Phase 2 delete message SHOULD NOT be interpreted as a reason for tearing down the iSCSI TCP connection. If additional traffic is sent on it, a new IKE Phase 2 SA will be created to protect it. The method used by the initiator to determine whether the target should be connected using IPsec is regarded as an issue of IPsec pol- icy administration, and thus not defined in the iSCSI standard. If an iSCSI target is discovered via a SendTargets request in a dis- covery session not using IPsec, the initiator should assume that it does not need IPsec to establish a session to that target. If an iSCSI target is discovered using a discovery session that does use IPsec, the initiator SHOULD use IPsec when establishing a session to that target. Julian Satran Expires February 2003 120 iSCSI 5-August-02 8. Notes to Implementers This section notes some of the performance and reliability consider- ations of the iSCSI protocol. This protocol was designed to allow efficient silicon and software implementations. The iSCSI task tag mechanism was designed to enable Direct Data Placement (DDP - a DMA form) at the iSCSI level or lower. The guiding assumption made throughout the design of this protocol is that targets are resource constrained relative to initiators. Implementers are also advised to consider the implementation conse- quences of the iSCSI to SCSI mapping model as outlined in Section 2.4.3 Consequences of the Model. 8.1 Multiple Network Adapters The iSCSI protocol allows multiple connections, not all of which need to go over the same network adapter. If multiple network connections are to be utilized with hardware support, the iSCSI protocol command- data-status allegiance to one TCP connection ensures that there is no need to replicate information across network adapters or otherwise require them to cooperate. However, some task management commands may require some loose form of cooperation or replication at least on the target. 8.1.1 Conservative Reuse of ISIDs Historically, the SCSI model (and implementations and applications based on that model) has assumed that SCSI ports are static, physi- cal entities. Recent extensions to the SCSI model have taken advan- tage of persistent worldwide unique names for these ports. In iSCSI however, the SCSI initiator ports are the endpoints of dynamically created sessions, so the presumption of "static and physical" does not apply. In any case, the model clauses (particularly, Section 2.4.2 SCSI Architecture Model) provide for persistent, reusable names for the iSCSI-type SCSI initiator ports even though there does not need to be any physical entity bound to these names. To both minimize the disruption of legacy applications and to better facilitate the SCSI features that rely on persistent names for SCSI ports, iSCSI implementations SHOULD attempt to provide a stable pre- Julian Satran Expires February 2003 121 iSCSI 5-August-02 sentation of SCSI Initiator Ports (both to the upper OS-layers and to the targets to which they connect). This can be achieved in an initi- ator implementation by conservatively reusing ISIDs. In other words, the same ISID should be used in the Login process to multiple target portal groups (of the same iSCSI Target or different iSCSI Targets). The ISID RULE (Section 2.4.3 Consequences of the Model) only prohib- its reuse to the same target portal group. It does not "preclude" reuse to other target portal groups. The principle of conservative reuse "encourages" reuse to other tar- get portal groups. When a SCSI target device sees the same (Initia- torName, ISID) pair in different sessions to different target portal groups, it can identify the underlying SCSI Initiator Port on each session as the same SCSI port. In effect, it can recognize multiple paths from the same source. 8.1.2 iSCSI Name, ISID and TPGT Use The designers of the iSCSI protocol envisioned there being one iSCSI Initiator Node Name per operating system image on a machine. This enables SAN resource configuration and authentication schemes based on a system's identity. It supports the notion that it should be pos- sible to assign access to storage resources based on "initiator device" identity. When there are multiple hardware or software components coordinated as a single iSCSI Node, there must be some (logical) entity that rep- resents the iSCSI Node that makes the iSCSI Node Name available to all components involved in session creation and login. Similarly, this entity that represents the iSCSI Node must be able to coordi- nate session identifier resources (ISID for initiators) to enforce both the ISID and TSIH RULES (see Section Section 2.4.3 Consequences of the Model). For targets, because of the closed environment, implementation of this entity should be straightforward. However, vendors of iSCSI hardware (e.g., NICs or HBAs) intended for targets, SHOULD provide mechanisms for configuration of the iSCSI Node Name across the por- tal groups instantiated by multiple instances of these components within a target. However, complex targets making use of multiple Target Portal Group Tags may reconfigure them to achieve various quality goals. The ini- tiators have two mechanisms at their disposal to discover and/or Julian Satran Expires February 2003 122 iSCSI 5-August-02 check reconfiguring targets - the discovery session type and a key returned by the target during login to confirm the TPGT. An initia- tor should attempt to "rediscover" the target configuration anytime a session is terminated unexpectedly. For initiators, in the long term, it is expected that operating sys- tem vendors will take on the role of this entity and provide stan- dard APIs that can inform components of their iSCSI Node Name and can configure and/or coordinate ISID allocation, use and reuse. Recognizing that such initiator APIs are not available today, other implementations of the role of this entity are possible. For exam- ple, a human may instantiate the (common) Node name as part of the installation process of each iSCSI component involved in session cre- ation and login. This may be done either by pointing the component to a vendor-specific location for this datum or to a system-wide loca- tion. The structure of the ISID namespace (see Section 9.12.5 ISID and [NDT]) facilitates implementation of the ISID coordination by allowing each component vendor to independently (of other vendor's components) coordinate allocation and use and reuse its own parti- tion of the ISID namespace in a vendor-specific manner. Partitioning of the ISID namespace within initiator portal groups managed by that vendor allows each such initiator portal group to act independently of all other portal groups when selecting an ISID for a login; this facilitates enforcement of the ISID RULE (see Section 2.4.3 Conse- quences of the Model) at the initiator. A vendor of iSCSI hardware (e.g., NICs or HBAs) intended for use in the initiators MUST implement a mechanism for configuring the iSCSI Node Name. Vendors, and administrators must ensure that iSCSI Node Names are unique worldwide. It is therefore important that when one chooses to reuse the iSCSI Node Name of a disabled unit, not to re- assign that name to the original unit unless its worldwide unique- ness can be ascertained again. In addition a vendor of iSCSI hardware must implement a mechanism to configure and/or coordinate ISIDs for all sessions managed by multi- ple instances of that hardware within a given iSCSI Node. Such con- figuration might be either permanently pre-assigned at the factory (in a necessarily globally unique way), statically assigned (e.g., partitioned across all the NICs at initialization in a locally unique way), or dynamically assigned (e.g., on-line allocator, also in a locally unique way). In the latter two cases, the configuration may Julian Satran Expires February 2003 123 iSCSI 5-August-02 be via public APIs (perhaps driven by an independent vendor's soft- ware, such as the OS vendor) or via private APIs driven by the ven- dor's own software. 8.2 Autosense and Auto Contingent Allegiance (ACA) Autosense refers to the automatic return of sense data to the initia- tor in case a command did not complete successfully. iSCSI initia- tors and targets MUST support and use autosense. ACA helps preserve ordered command execution in the presence of errors. As iSCSI can have many commands in-flight between initiator and target, iSCSI initiators and targets SHOULD support ACA. 8.3 iSCSI timeouts iSCSI recovery actions are often dependent on iSCSI time-outs being recognized and acted upon before SCSI time-outs. Determining the right time-outs to use for various iSCSI actions (command acknowl- edgements expected, status acknowledgements, etc.) is very much dependent on infrastructure (hardware, links, TCP/IP stack, iSCSI driver). As a guidance the implementer may use an average Nop-Out/ Nop-In turnaround delay multiplied by a "safety factor" (e.g., 4) with a minimum of several milliseconds as a good estimate for the basic delay of the iSCSI stack for a given connection. The relation between iSCSI timeouts and SCSI timeouts should also be considered. SCSI timeouts should be longer than iSCSI timeouts plus the time required for iSCSI recovery whenever iSCSI recovery is planned. Alternatively an implementer may choose to interlock iSCSI timeouts and recovery with SCSI timeouts so that SCSI will recovery will become active only where iSCSI is not planned to or failed to recover. The implementer may want to consider also the interaction between various iSCSI exception events - like a digest failure - and subse- quent timeouts. When iSCSI error recovery is active a digest failure is likely to result in discovering a missing command or data PDU. In those cases an implementer may want to lower the timeout values to enable faster initiation for recovery procedures. Julian Satran Expires February 2003 124 iSCSI 5-August-02 8.4 Command Retry and Cleaning Old Command Instances To avoid having old, retried command instances appear in a valid com- mand window after a command sequence number wrap around, the proto- col requires (see Section 2.2.2.1 Command Numbering and Acknowledging) that on every connection on which a retry has been issued, a non-immediate command be issued and acknowledged within a 2**31-1 commands interval from the CmdSN of the retried command. This requirement can be fulfilled by an implementation in several ways. The simplest technique to use is to send a (non-retry) non-immediate SCSI command (or a NOP if no SCSI command is available for a while) after every command retry on the connection on which the retry was attempted. As errors are deemed rare events, this technique is proba- bly the most effective, as it does not involve additional checks at the initiator when issuing commands. 8.5 Synch and Steering Layer and Performance While a synch and steering layer is optional, an initiator/target that does not have it working against a target/initiator that demands synch and steering may experience performance degradation caused by packet reordering and loss. Providing a synch and steering mechanism is recommended for all high-speed implementations. 8.6 Considerations for State-dependent devices and long lasting SCSI operations. Sequential access devices operate on the principle that the position of the device is based on the last command processed. As such, com- mand processing order and knowledge of whether or not the previous command was processed is of the utmost importance to maintain data integrity. As an example, inadvertent retries of SCSI commands when it is not known if the previous SCSI command was processed is a potential data integrity risk. For a sequential access device, consider the scenario where a SCSI SPACE command to backspace one filemark is issued and then re-issued due to no status received for the command. If the first SPACE com- mand was actually processed, the re-issued SPACE command, if pro- cessed, will cause the position to change. Thus, a subsequent write operation will write data to the wrong position and any previous data at that position will be overwritten. Julian Satran Expires February 2003 125 iSCSI 5-August-02 For a medium changer device, consider the scenario where an EXCHANGE MEDIUM command (the SOURCE ADDRESS and DESTINATION ADDRESS are the same thus performing a swap) is issued and then re-issued due to no status received for the command. If the first EXCHANGE MEDIUM com- mand was actually processed, the re-issued EXCHANGE MEDIUM command, if processed, will perform the swap again. The net effect is no swap was performed thus leaving a data integrity exposure. All commands that change the state of the device (as in SPACE com- mands for sequential access devices, and EXCHANGE MEDIUM for medium changer device), MUST be issued as non-immediate commands for deter- ministic and in order delivery to iSCSI targets. For many of those state changing commands the execution model also assumes that the command is executed exactly once. Devices implement- ing READ POSITION and LOCATE provide a means for SCSI level command recovery and new tape-class devices should support those commands. In their absence a retry at SCSI level is difficult and error recov- ery at iSCSI level is advisable. Devices operating on long latency delivery subsystems and performing long lasting SCSI operations may need mechanism that enable connec- tion replacement while commands are running (e.g., during a an extended copy operation). 8.6.1 Determining the proper ErrorRecoveryLevel The implementation and usage of a specific ErrorRecoveryLevel should be determined based on the deployment scenarios of a given iSCSI implementation. Generally, the following factors must be considered before deciding on the proper level of recovery: a) Application resilience to I/O failures. b) Required level of availability in the face of transport con- nection failures. c) Probability of transport layer "checksum escape" frequency. This in turn decides the iSCSI digest failure frequency, and thus the criticality of iSCSI-level error recovery. The details of estimating this probability are outside the scope of this docu- ment. Julian Satran Expires February 2003 126 iSCSI 5-August-02 A consideration of the above factors for SCSI tape devices as an example suggests that implementations SHOULD use ErrorRecovery- Level=1 when transport connection failure is not a concern and SCSI level recovery is unavailable, and ErrorRecoveryLevel=2 when the con- nection failure is also of high likelihood during a backup/retrieval. For extended copy operations implementations SHOULD use ErrorRecov- eryLevel=2 whenever connection failure has a relatively high likeli- hood. Julian Satran Expires February 2003 127 iSCSI 5-August-02 9. iSCSI PDU Formats All multi-byte integers that are specified in formats defined in this document are to be represented in network byte order (i.e., big endian). Any field that appears in this document assumes that the most significant byte is the lowest numbered byte and the most sig- nificant bit (within byte or field) is the lowest numbered bit unless specified otherwise. Any compliant sender MUST set all bits not defined and all reserved fields to zero unless specified otherwise. Any compliant receiver MUST ignore any bit not defined and all reserved fields unless speci- fied otherwise. Receipt of reserved code values in defined fields MUST be reported as a protocol error. Reserved fields are marked by the word "reserved", some abbreviation of "reserved" or by "." for individual bits when no other form of marking is technically feasible. 9.1 iSCSI PDU Length and Padding iSCSI PDUs are padded to the closest integer number of four byte words. The padding bytes SHOULD be sent as 0. 9.2 PDU Template, Header, and Opcodes All iSCSI PDUs have one or more header segments and, optionally, a data segment. After the entire header segment group a header-digest MAY follow. The data segment MAY also be followed by a data-digest. The Basic Header Segment (BHS) is the first segment in all of the iSCSI PDUs. The BHS is a fixed-length 48-byte header segment. It MAY be followed by Additional Header Segments (AHS), a Header-Digest, a Data Segment, and/or a Data-Digest. The overall structure of an iSCSI PDU is as follows: Julian Satran Expires February 2003 128 iSCSI 5-August-02 Byte/ 0 | 1 | 2 | 3 | / | | | | |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7| +---------------+---------------+---------------+---------------+ 0/ Basic Header Segment (BHS) / +/ / +---------------+---------------+---------------+---------------+ 48/ Additional Header Segment 1 (AHS) (optional) / +/ / +---------------+---------------+---------------+---------------+ / Additional Header Segment 2 (AHS) (optional) / +/ / +---------------+---------------+---------------+---------------+ ---- +---------------+---------------+---------------+---------------+ / Additional Header Segment n (AHS) (optional) / +/ / +---------------+---------------+---------------+---------------+ ---- +---------------+---------------+---------------+---------------+ k/ Header-Digest (optional) / +/ / +---------------+---------------+---------------+---------------+ l/ Data Segment(optional) / +/ / +---------------+---------------+---------------+---------------+ m/ Data-Digest (optional) / +/ / +---------------+---------------+---------------+---------------+ All PDU segments and digests are padded to the closest integer num- ber of four byte words - i.e., all PDU segments and the digests start at a four byte word boundary and the padding ranges from 0 to 3 bytes. The padding bytes SHOULD be sent as 0. iSCSI response PDUs do not have AH Segments. 9.2.1 Basic Header Segment (BHS) The BHS is 48 bytes long. The Opcode and DataSegmentLength fields appear in all iSCSI PDUs. In addition, when used, the Initiator Task Tag and Logical Unit Number always appear in the same location in the header. Julian Satran Expires February 2003 129 iSCSI 5-August-02 The format of the BHS is: Byte/ 0 | 1 | 2 | 3 | / | | | | |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7| +---------------+---------------+---------------+---------------+ 0|.|I| Opcode |F| Opcode-specific fields | +---------------+---------------+---------------+---------------+ 4|TotalAHSLength | DataSegmentLength | +---------------+---------------+---------------+---------------+ 8| LUN or Opcode-specific fields | + + 12| | +---------------+---------------+---------------+---------------+ 16| Initiator Task Tag | +---------------+---------------+---------------+---------------+ 20/ Opcode-specific fields / +/ / +---------------+---------------+---------------+---------------+ 48 9.2.1.1 I For request PDUs, the I bit set to 1 is an immediate delivery marker. 9.2.1.2 Opcode The Opcode indicates the type of iSCSI PDU the header encapsulates. The Opcodes are divided into two categories: initiator opcodes and target opcodes. Initiator opcodes are in PDUs sent by the initiators (request PDUs). Target opcodes are in PDUs sent by the target (response PDUs). Initiators MUST NOT use target opcodes and targets MUST NOT use ini- tiator opcodes. Initiator opcodes defined in this specification are: 0x00 NOP-Out Julian Satran Expires February 2003 130 iSCSI 5-August-02 0x01 SCSI Command (encapsulates a SCSI Command Descriptor Block) 0x02 SCSI Task Management function request 0x03 Login Request 0x04 Text Request 0x05 SCSI Data-out (for WRITE operations) 0x06 Logout Request 0x10 SNACK Request 0x1c-0x1e Vendor specific codes Target opcodes are: 0x20 NOP-In 0x21 SCSI Response -contains SCSI status and possibly sense information or other response information. 0x22 SCSI Task Management function response 0x23 Login Response 0x24 Text Response 0x25 SCSI Data-in -for READ operations. 0x26 Logout Response 0x31 Ready To Transfer (R2T) - sent by target when it is ready to receive data. 0x32 Asynchronous Message -sent by target to indicate certain special conditions. 0x3c-0x3e Vendor specific codes 0x3f Reject All other opcodes are reserved. 9.2.1.3 Final (F) bit When set to 1 it usually indicates the final (or only) PDU of a sequence. 9.2.1.4 Opcode-specific Fields These fields have different meanings for different opcode types. 9.2.1.5 TotalAHSLength Total length of all AHS header segments in four byte words including padding, if any. The TotalAHSLength is used only in PDUs that have an AHS and MUST be 0 in all other PDUs. Julian Satran Expires February 2003 131 iSCSI 5-August-02 9.2.1.6 DataSegmentLength This is the data segment payload length in bytes (excluding pad- ding). The DataSegmentLength MUST be 0 whenever the PDU has no data segment. 9.2.1.7 LUN Some opcodes operate on a specific Logical Unit. The Logical Unit Number (LUN) field identifies which Logical Unit. If the opcode does not relate to a Logical Unit, this field is either ignored or may be used in an opcode specific way. The LUN field is 64-bits and should be formatted in accordance with [SAM2] i.e., LUN[0] from [SAM2] is BHS byte 8 and so on up to LUN[7] from [SAM2] that is BHS byte 15. 9.2.1.8 Initiator Task Tag The initiator assigns a Task Tag to each iSCSI task it issues. While a task exists, this tag MUST uniquely identify the task session-wide. SCSI may also use the initiator task tag as part of the SCSI task identifier when the timespan during which an iSCSI initiator task tag must be unique extends over the timespan during which a SCSI task tag must be unique. However, the iSCSI Initiator Task Tag has to exist and be unique even for untagged SCSI commands. 9.2.2 Additional Header Segment (AHS) The general format of an AHS is: Byte/ 0 | 1 | 2 | 3 | / | | | | |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7| +---------------+---------------+---------------+---------------+ 0| AHSLength | AHSType | AHS-Specific | +---------------+---------------+---------------+---------------+ 4/ AHS-Specific / +/ / +---------------+---------------+---------------+---------------+ x 9.2.2.1 AHSType The AHSType field is coded as follows: Julian Satran Expires February 2003 132 iSCSI 5-August-02 bit 0-1 - Reserved bit 2-7 - AHS code 0 - Reserved 1 - Extended CDB 2 - Expected Bidirectional Read Data Length 3 - 59 Reserved 60- 63 Non-iSCSI extensions 9.2.2.2 AHSLength This field contains the effective length in bytes of the AHS exclud- ing AHSType and AHSLength and padding, if any. The AHS is padded to the smallest integer number of 4 byte words (i.e., from 0 up to 3 padding bytes). 9.2.2.3 Extended CDB AHS The format of the Extended CDB AHS is: Byte/ 0 | 1 | 2 | 3 | / | | | | |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7| +---------------+---------------+---------------+---------------+ 0| AHSLength (CDBLength-15) | 0x01 | Reserved | +---------------+---------------+---------------+---------------+ 4/ ExtendedCDB...+padding / +/ / +---------------+---------------+---------------+---------------+ x This type of AHS MUST NOT be used if the CDBLength is less than 17. The length includes the reserved byte 3. 9.2.2.4 Bidirectional Expected Read-Data Length AHS The format of the Bidirectional Read Expected Data Transfer Length AHS is: Julian Satran Expires February 2003 133 iSCSI 5-August-02 Byte/ 0 | 1 | 2 | 3 | / | | | | |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7| +---------------+---------------+---------------+---------------+ 0| AHSLength (0x0005) | 0x02 | Reserved | +---------------+---------------+---------------+---------------+ 4| Expected Read-Data Length | +---------------+---------------+---------------+---------------+ 8 9.2.3 Header Digest and Data Digest Optional header and data digests protect the integrity of the header and data, respectively. The digests, if present, are located, respec- tively, after the header and PDU-specific data and cover both the proper data as well as the padding bytes. The existence and type of digests are negotiated during the Login Phase. The separation of the header and data digests is useful in iSCSI routing applications, where only the header changes when a message is forwarded. In this case, only the header digest should be re-calcu- lated. Digests are not included in data or header length fields. A zero-length Data Segment also implies a zero-length data-digest. 9.2.4 Data Segment The (optional) Data Segment contains PDU associated data. Its pay- load effective length is provided in the BHS field - DataSeg- mentLength. The Data Segment is also padded to an integer number of 4 byte words. Julian Satran Expires February 2003 134 iSCSI 5-August-02 9.3 SCSI Command The format of the SCSI Command PDU is: Byte/ 0 | 1 | 2 | 3 | / | | | | |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7| +---------------+---------------+---------------+---------------+ 0|.|I| 0x01 |F|R|W|0 0|ATTR | Reserved | +---------------+---------------+---------------+---------------+ 4|TotalAHSLength | DataSegmentLength | +---------------+---------------+---------------+---------------+ 8| Logical Unit Number (LUN) | + + 12| | +---------------+---------------+---------------+---------------+ 16| Initiator Task Tag | +---------------+---------------+---------------+---------------+ 20| Expected Data Transfer Length | +---------------+---------------+---------------+---------------+ 24| CmdSN | +---------------+---------------+---------------+---------------+ 28| ExpStatSN | +---------------+---------------+---------------+---------------+ 32/ SCSI Command Descriptor Block (CDB) / +/ / +---------------+---------------+---------------+---------------+ 48/ AHS (if any) / +---------------+---------------+---------------+---------------+ x/ Header Digest (if any) / +---------------+---------------+---------------+---------------+ y/ (DataSegment, Command Data) (if any) / +/ / +---------------+---------------+---------------+---------------+ z/ Data Digest (if any) / +---------------+---------------+---------------+---------------+ 9.3.1 Flags and Task Attributes (byte 1) The flags for a SCSI Command are: bit 0 (F) is set to 1 when no unsolicited SCSI Data-Out PDUs follow this PDU. When F=1 for a write and if Expected Data Julian Satran Expires February 2003 135 iSCSI 5-August-02 Transfer Length is larger than the DataSegmentLength the tar- get may solicit additional data through R2T. bit 1 (R) is set to 1 when the command is expected to input data. bit 2 (W) is set to 1 when the command is expected to output data. bit 3-4 Reserved bit 5-7 contains Task Attributes. Task Attributes (ATTR) have one of the following integer values (see [SAM2] for details): 0 - Untagged 1 - Simple 2 - Ordered 3 - Head of Queue 4 - ACA 5-7 - Reserved Setting both the W and the F bit to 0 is an error. Either or both of R and W MAY be 1 when either the corresponding Expected Data Transfer Lengths are 0, but they MUST NOT both be 0 when the corresponding Expected Data Transfer Length and/or Bidirec- tional Read Expected Data Transfer Length are not 0. 9.3.2 CmdSN - Command Sequence Number Enables ordered delivery across multiple connections in a single ses- sion. 9.3.3 ExpStatSN Command responses up to ExpStatSN-1 (mod 2**32) have been received (acknowledges status) on the connection. 9.3.4 Expected Data Transfer Length For unidirectional operations, the Expected Data Transfer Length field contains the number of bytes of data involved in this SCSI operation. For a unidirectional write operation (W flag set to 1 and R flag set to 0), the initiator uses this field to specify the num- Julian Satran Expires February 2003 136 iSCSI 5-August-02 ber of bytes of data it expects to transfer for this operation. For a unidirectional read operation (W flag set to 0 and R flag set to 1), the initiator uses this field to specify the number of bytes of data it expects the target to transfer to the initiator. It corre- sponds to the SAM2 byte count. For bidirectional operations (both R and W flags are set to 1), this field contains the number of data bytes involved in the write trans- fer. For bidirectional operations, an additional header segment MUST be present in the header sequence that indicates the Bidirectional Read Expected Data Transfer Length. The Expected Data Transfer Length field and the Bidirectional Read Expected Data Transfer Length field correspond to the SAM2 byte count If the Expected Data Transfer Length for a write and the length of the immediate data part that follows the command (if any) are the same, then no more data PDUs are expected to follow. In this case, the F bit MUST be set to 1. If the Expected Data Transfer Length is higher than the FirstBurst- Length (the negotiated maximum amount of unsolicited data the target will accept), the initiator MUST send the maximum length of unsolic- ited data OR ONLY the immediate data if any. Upon completion of a data transfer, the target informs the initiator (through residual counts) of how many bytes were actually processed (sent and/or received) by the target. 9.3.5 CDB - SCSI Command Descriptor Block There are 16 bytes in the CDB field to accommodate the commonly used CDBs. Whenever the CDB is larger than 16 bytes, an Extended CDB AHS MUST be used to contain the CDB spillover. 9.3.6 Data Segment - Command Data Some SCSI commands require additional parameter data to accompany the SCSI command. This data may be placed beyond the boundary of the iSCSI header in a data segment. Alternatively, user data (for exam- ple, from a WRITE operation) can be placed in the data segment (both cases are referred to as immediate data). These data are governed by the general rules for solicited vs. unsolicited data. Julian Satran Expires February 2003 137 iSCSI 5-August-02 9.4 SCSI Response The format of the SCSI Response PDU is: Byte/ 0 | 1 | 2 | 3 | / | | | | |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7| +---------------+---------------+---------------+---------------+ 0|.|.| 0x21 |1|. .|o|u|O|U|.| Response | Status | +---------------+---------------+---------------+---------------+ 4|TotalAHSLength | DataSegmentLength | +---------------+---------------+---------------+---------------+ 8| Reserved | + + 12| | +---------------+---------------+---------------+---------------+ 16| Initiator Task Tag | +---------------+---------------+---------------+---------------+ 20| SNACK Tag or Reserved | +---------------+---------------+---------------+---------------+ 24| StatSN | +---------------+---------------+---------------+---------------+ 28| ExpCmdSN | +---------------+---------------+---------------+---------------+ 32| MaxCmdSN | +---------------+---------------+---------------+---------------+ 36| ExpDataSN or Reserved | +---------------+---------------+---------------+---------------+ 40| Bidirectional Read Residual Count or Reserved | +---------------+---------------+---------------+---------------+ 44| Residual Count or Reserved | +---------------+---------------+---------------+---------------+ 48| Header-Digest (Optional) | +---------------+---------------+---------------+---------------+ / Data Segment (Optional) / +/ / +---------------+---------------+---------------+---------------+ | Data-Digest (Optional) | +---------------+---------------+---------------+---------------+ 9.4.1 Flags (byte 1) bit 1-2 Reserved Julian Satran Expires February 2003 138 iSCSI 5-August-02 bit 3 - (o) set for Bidirectional Read Residual Overflow. In this case, the Bidirectional Read Residual Count indicates the number of bytes that were not transferred to the initia- tor because the initiator's Expected Bidirectional Read Data Transfer Length was not sufficient. bit 4 - (u) set for Bidirectional Read Residual Underflow. In this case, the Bidirectional Read Residual Count indicates the number of bytes that were not transferred to the initia- tor out of the number of bytes expected to be transferred. bit 5 - (O) set for Residual Overflow. In this case, the Resid- ual Count indicates the number of bytes that were not trans- ferred because the initiator's Expected Data Transfer Length was not sufficient. For a bidirectional operation, the Resid- ual Count contains the residual for the write operation. bit 6 - (U) set for Residual Underflow. In this case, the Residual Count indicates the number of bytes that were not transferred out of the number of bytes that were expected to be transferred. For a bidirectional operation, the Residual Count contains the residual for the write operation. bit 7 - (0) Reserved Bits O and U and bits o and u are mutually exclusive (i.e. having both o and u or O and U set to 1 is a protocol error). For a response other than "Command Completed at Target" bits 3-6 MUST be 0. 9.4.2 Status The Status field is used to report the SCSI status of the command (as specified in [SAM2]) and is valid only if the Response Code is Com- mand Completed at target. Some of the status codes defined in [SAM2] are: 0x00 GOOD 0x02 CHECK CONDITION 0x08 BUSY 0x18 RESERVATION CONFLICT 0x28 TASK SET FULL 0x30 ACA ACTIVE 0x40 TASK ABORTED See [SAM2] for the complete list and definitions. Julian Satran Expires February 2003 139 iSCSI 5-August-02 If a SCSI device error is detected while data from the initiator is still expected (the command PDU did not contain all the data and the target has not received a Data PDU with the final bit Set), the tar- get MUST wait until it receives a Data PDU with the F bit set in the last expected sequence before sending the Response PDU. 9.4.3 Response This field contains the iSCSI service response. iSCSI service response codes defined in this specification are: 0x00 - Command Completed at Target 0x01 - Target Failure 0x80-0xff - Vendor specific All other response codes are reserved. The Response is used to report a Service Response. The mapping of the response code into a SCSI service response code value, if needed, is outside the scope of this document. However, in symbolic terms response value 0x00 maps to the SCSI service response (see [SAM2] and [SPC3]) of TASK COMPLETE or LINKED COMMAND COMPLETE. All other Response values map to the SCSI service response of SERVICE DELIVERY OR TARGET FAILURE. If a SCSI Response PDU does not arrive before the session is termi- nated, the SCSI service response is SERVICE DELIVERY OR TARGET FAIL- URE. A non-zero response field indicates a failure to execute the command in which case the Status and Sense fields are undefined. 9.4.4 SNACK Tag This field contains a copy of the SNACK Tag of the last SNACK Tag accepted by the target on the same connection and for the command for which the response is issued. Otherwise it is reserved and should be set to 0. After issuing a R-Data SNACK the initiator must discard any SCSI sta- tus unless contained in an SCSI Response PDU carrying the same SNACK Tag as the last issued R-Data SNACK for the SCSI command on the cur- rent connection. Julian Satran Expires February 2003 140 iSCSI 5-August-02 For a detailed discussion on R-Data SNACK see Section 9.16 SNACK Request. 9.4.5 Residual Count The Residual Count field MUST be valid in the case where either the U bit or the O bit is set. If neither bit is set, the Residual Count field is reserved. Targets may set the residual count and initiators may use it when the response code is "completed at target" (even if the status returned is not GOOD). If the O bit is set, the Residual Count indicates the number of bytes that were not transferred because the initiator's Expected Data Transfer Length was not sufficient. If the U bit is set, the Residual Count indicates the number of bytes that were not transferred out of the number of bytes expected to be transferred. 9.4.6 Bidirectional Read Residual Count The Bidirectional Read Residual Count field MUST be valid in the case where either the u bit or the o bit is set. If neither bit is set, the Bidirectional Read Residual Count field is reserved. Targets may set the Bidirectional Read Residual Count and initiators may use it when the response code is "completed at target". If the o bit is set, the Bidirectional Read Residual Count indicates the number of bytes that were not transferred to the initiator because the initiator's Expected Bidirectional Read Transfer Length was not sufficient. If the u bit is set, the Bidirectional Read Residual Count indicates the number of bytes that were not transferred to the initiator out of the number of bytes expected to be transferred. 9.4.7 Data Segment - Sense and Response Data Segment iSCSI targets MUST support and enable autosense. If Status is CHECK CONDITION (0x02), then the Data Segment MUST contain sense data for the failed command. For some iSCSI responses, the response data segment MAY contain some response related information, (e.g., for a target failure, it may contain a vendor specific detailed description of the failure). If the DataSegmentLength is not 0, the format of the Data Segment is as follows: Julian Satran Expires February 2003 141 iSCSI 5-August-02 Byte/ 0 | 1 | 2 | 3 | / | | | | |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7| +---------------+---------------+---------------+---------------+ 0|SenseLength | Sense Data | +---------------+---------------+---------------+---------------+ x/ Sense Data / +---------------+---------------+---------------+---------------+ y/ Response Data / / / +---------------+---------------+---------------+---------------+ z| 9.4.7.1 SenseLength Length of Sense Data. 9.4.7.2 Sense Data The Sense Data contains detailed information about a check condition and [SPC] specifies the format and content of the Sense Data. Certain iSCSI conditions result in the command being terminated at the target (response Command Completed at Target) with a SCSI Check Condition Status as outlined in the next table: +--------------------------+----------+---------------------------+ | iSCSI Condition |Sense | Additional Sense Code & | | |Key | Qualifier | +--------------------------+----------+---------------------------+ | Unexpected unsolicited |Aborted | ASC = 0x0c ASCQ = 0x0c | | data |Command-0B| Write Error | +--------------------------+----------+---------------------------+ | Incorrect amount of data |Aborted | ASC = 0x0c ASCQ = 0x0d | | |Command-0B| Write Error | +--------------------------+----------+---------------------------+ | Protocol Service CRC |Aborted | ASC = 0x47 ASCQ = 0x05 | | error |Command-0B| CRC Error Detected | +--------------------------+----------+---------------------------+ | SNACK rejected |Aborted | ASC = 0x11 ASCQ = 0x13 | | |Command-0B| Read Error | +--------------------------+----------+---------------------------+ Julian Satran Expires February 2003 142 iSCSI 5-August-02 The target reports the "Incorrect amount of data" condition if dur- ing data output the total data length to output is greater than FirstBurstLength and the initiator sent unsolicited non-immediate data but the total amount of unsolicited data is different than FirstBurstLength. The target reports the same error when the amount of data sent as a reply to an R2T does not match the amount requested. 9.4.8 ExpDataSN The number of Data-In (read) PDUs the target has sent for the com- mand. This field is reserved if the response code is not Command Completed at Target or the command is a write command. 9.4.9 StatSN - Status Sequence Number StatSN is a Sequence Number that the target iSCSI layer generates per connection and that in turn, enables the initiator to acknowledge status reception. StatSN is incremented by 1 for every response/sta- tus sent on a connection except for responses sent as a result of a retry or SNACK. In the case of responses sent due to a retransmis- sion request, the StatSN MUST be the same as the first time the PDU was sent unless the connection has since been restarted. 9.4.10 ExpCmdSN - Next Expected CmdSN from this Initiator ExpCmdSN is a Sequence Number that the target iSCSI returns to the initiator to acknowledge command reception. It is used to update a local variable with the same name. An ExpCmdSN equal to MaxCmdSN+1 indicates that the target cannot accept new commands. 9.4.11 MaxCmdSN - Maximum CmdSN from this Initiator MaxCmdSN is a Sequence Number that the target iSCSI returns to the initiator to indicate the maximum CmdSN the initiator can send. It is used to update a local variable with the same name. If MaxCmdSN is equal to ExpCmdSN-1, this indicates to the initiator that the target cannot receive any additional commands. When MaxCmdSN changes at the target while the target has no pending PDUs to convey this informa- tion to the initiator, it MUST generate a NOP-IN to carry the new MaxCmdSN. Julian Satran Expires February 2003 143 iSCSI 5-August-02 Julian Satran Expires February 2003 144 iSCSI 5-August-02 9.5 Task Management Function Request Byte/ 0 | 1 | 2 | 3 | / | | | | |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7| +---------------+---------------+---------------+---------------+ 0|.|I| 0x02 |1| Function | Reserved | +---------------+---------------+---------------+---------------+ 4|TotalAHSLength | DataSegmentLength | +---------------+---------------+---------------+---------------+ 8| Logical Unit Number (LUN) or Reserved | + + 12| | +---------------+---------------+---------------+---------------+ 16| Initiator Task Tag | +---------------+---------------+---------------+---------------+ 20| Referenced Task Tag or 0xffffffff | +---------------+---------------+---------------+---------------+ 24| CmdSN | +---------------+---------------+---------------+---------------+ 28| ExpStatSN | +---------------+---------------+---------------+---------------+ 32| RefCmdSN or Reserved | +---------------+---------------+---------------+---------------+ 36| ExpDataSN or Reserved | +---------------+---------------+---------------+---------------+ 40/ Reserved / +/ / +---------------+---------------+---------------+---------------+ 48| Header-Digest (Optional) | +---------------+---------------+---------------+---------------+ 9.5.1 Function The Task Management functions provide an initiator with a way to explicitly control the execution of one or more Tasks (SCSI and iSCSI tasks). The Task Management function codes are listed below. For a more detailed description of SCSI task management, see [SAM2]. 1 - ABORT TASK - aborts the task identified by the Refer- enced Task Tag field. 2 - ABORT TASK SET - aborts all Tasks issued via this ses- sion on the logical unit. Julian Satran Expires February 2003 145 iSCSI 5-August-02 3 - CLEAR ACA - clears the Auto Contingent Allegiance condi- tion. 4 - CLEAR TASK SET - aborts all Tasks in the appropriate task set as defined by the TST field in the Control mode page (see [SPC3]). 5 - LOGICAL UNIT RESET 6 - TARGET WARM RESET 7 - TARGET COLD RESET 8 - TASK REASSIGN - reassigns connection allegiance for the task identified by the Initiator Task Tag field to this con- nection, thus resuming the iSCSI exchanges for the task. For all these functions, the Task Management function response MUST be returned as detailed in Section 9.6 Task Management Function Response. All these functions apply to the referenced tasks regard- less of whether they are proper SCSI tasks or tagged iSCSI opera- tions. Task management requests must act on all the commands having a CmdSN lower than the task management CmdSN. If the task management request is marked for immediate delivery it must be considered imme- diately for execution but the operations involved (all or part of them) may be postponed to allow the target to receive all relevant tasks. According to [SAM2] for all the tasks covered by the Task Man- agement response (i.e., with CmdSN not higher than the task manage- ment command CmdSN), additional responses MUST NOT be delivered to the SCSI layer after the Task Management response. The iSCSI initia- tor MAY deliver to the SCSI layer all responses received before the Task Management response (i.e., it is a matter of implementation if the SCSI responses - received before the Task Management response but after the task management request was issued - are delivered to the SCSI layer by the iSCSI layer in the initiator). The iSCSI target MUST ensure that no responses for the tasks covered by a task manage- ment function are delivered to the iSCSI initiator after the Task Management response. For ABORT TASK SET and CLEAR TASK SET, the issuing initiator MUST continue to respond to all valid target transfer tags (received via R2T, Text Response, NOP-In, or SCSI Data-in PDUs) related to the affected task set, even after issuing the task management request. The issuing initiator SHOULD however terminate (i.e. by setting the Julian Satran Expires February 2003 146 iSCSI 5-August-02 F-bit to 1) these response sequences as quickly as possible. The target on its part MUST wait for responses on all affected target transfer tags before acting on either of these two task management requests. In case all or part of the response sequence is not received (due to digest errors) for a valid TTT, the target MAY treat it as a case of within-command error recovery class (section 5.14.1) if it is supporting ErrorRecoveryLevel >= 1, or alternatively may drop the connection to complete the requested task set function. If the connection is still active (it is not undergoing an implicit or explicit logout), ABORT TASK MUST be issued on the same connec- tion to which the task to be aborted is allegiant at the time the Task Management Request is issued. If the connection is implicitly or explicitly logged out (i.e., no other request will be issued on the failing connection and no other response will be received on the failing connection), then an ABORT TASK function request may be issued on another connection. This Task Management request will then establish a new allegiance for the command to be aborted as well as abort it (i.e., the task to be aborted will not have to be retried or reassigned, and its status, if issued but not acknowledged, will be reissued followed by the Task Management response). For the LOGICAL UNIT RESET function, the target MUST behave as dic- tated by the Logical Unit Reset function in [SAM2]. The implementation of the TARGET WARM RESET function and the TARGET COLD RESET function is OPTIONAL and when implemented, should act as described below. The TARGET WARM RESET is also subject to SCSI access controls on the requesting initiator as defined in [SPC3]. When authorization fails at the target, the appropriate response as described in Section 9.6 Task Management Function Response MUST be returned by the target. The TARGET COLD RESET function is not sub- ject to SCSI access controls, but its execution privileges may be managed by iSCSI mechanisms such as login authentication. When executing the TARGET WARM RESET and TARGET COLD RESET func- tions, the target cancels all pending operations on all Logical Units known the issuing initiator. Both functions are equivalent to the Target Reset function specified by [SAM2]. They can affect many other initiators logged in with the servicing SCSI target port. The target MUST treat the TARGET COLD RESET function additionally as a power on event, thus terminating all of its TCP connections to all Julian Satran Expires February 2003 147 iSCSI 5-August-02 initiators (all sessions are terminated). For this reason, the Ser- vice Response (defined by [SAM2]) for this SCSI task management func- tion may not be reliably delivered to the issuing initiator port. For the TASK REASSIGN function, the target should reassign the con- nection allegiance to this new connection (and thus resume iSCSI exchanges for the task). TASK REASSIGN MUST be received by the tar- get ONLY after the connection on which the command was previously executing has been successfully logged-out. The Task Management response MUST be issued before the reassignment becomes effective. For additional usage semantics see Section 5.2 Retry and Reassign in Recovery. TASK REASSIGN MUST be issued as an immediate command. 9.5.2 TotalAHSLength and DataSegmentLength For this PDU TotalAHSLength and DataSegmentLength MUST be 0. 9.5.3 LUN This field is required for functions that address a specific LU (ABORT TASK, CLEAR TASK SET, ABORT TASK SET, CLEAR ACA, LOGICAL UNIT RESET) and is reserved in all others. 9.5.4 Referenced Task Tag The Initiator Task Tag of the task to be aborted for the ABORT TASK function or reassigned for the TASK REASSIGN function. For all the other functions this field MUST be set to the reserved value 0xffffffff. 9.5.5 RefCmdSN For the ABORT TASK function, initiators MUST always set this to the CmdSN of the task identified by the Referenced Task Tag field. Tar- gets must use this field as described in section 9.6.1 when the task identified by the Referenced Task Tag field is not with the target. Otherwise this field is reserved. Julian Satran Expires February 2003 148 iSCSI 5-August-02 9.5.6 ExpDataSN If the function is TASK REASSIGN, which establishes a new connection allegiance for a previously issued Read or Bidirectional command, this field will contain the next consecutive input DataSN number expected by the initiator (no gaps) for the referenced command in a previous execution. The initiator MUST discard any discontiguous data PDUs from the previous execution and the target MUST retransmit all data previously transmitted in Data-in PDUs (if any) starting with ExpDataSN. The number of retransmitted PDUs, may or may not be the same as the original transmission depending on if there was a change in MaxRecvDataSegmentLength in the reassignment. The target MAY also send no more Data-In PDUs if it sent all its data in PDUs with DataSN less than ExpDataSN. ExpDataSN MUST be higher than the DataSN of the last acknowledged Data-In PDU but not larger than DataSN+1 of the last Data-IN PDU sent by the target. Otherwise, this field is reserved. Julian Satran Expires February 2003 149 iSCSI 5-August-02 9.6 Task Management Function Response Byte/ 0 | 1 | 2 | 3 | / | | | | |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7| +---------------+---------------+---------------+---------------+ 0|.|.| 0x22 |1| Reserved | Response | Reserved | +---------------+---------------+---------------+---------------+ 4|TotalAHSLength | DataSegmentLength | +---------------------------------------------------------------+ 8/ Reserved / / / +---------------+---------------+---------------+---------------+ 16| Initiator Task Tag | +---------------+---------------+---------------+---------------+ 20| Reserved | +---------------+---------------+---------------+---------------+ 24| StatSN | +---------------+---------------+---------------+---------------+ 28| ExpCmdSN | +---------------+---------------+---------------+---------------+ 32| MaxCmdSN | +---------------+---------------+---------------+---------------+ 36/ Reserved / +/ / +---------------+---------------+---------------+---------------+ 48| Header-Digest (Optional) | +---------------+---------------+---------------+---------------+ For the functions ABORT TASK, ABORT TASK SET, CLEAR ACA, CLEAR TASK SET, LOGICAL UNIT RESET, TARGET COLD RESET, TARGET WARM RESET and TASK REASSIGN, the target performs the requested Task Management function and sends a Task Management response back to the initiator. For TASK REASSIGN the new connection allegiance MUST become effec- tive ONLY at the target only after the target issues the Task Manage- ment Response. 9.6.1 Response The target provides a Response, which may take on the following val- ues: a) 0 - Function Complete Julian Satran Expires February 2003 150 iSCSI 5-August-02 b) 1 - Task does not exist c) 2 - LUN does not exist. d) 3 - Task still allegiant. e) 4 - Task allegiance reassignment not supported. f) 5 - Task management function not supported. g) 6 - Function authorization failed. h) 255 - Function rejected. All other values are reserved. For a discussion on usage of response codes 3 and 4, see Section 5.2.2 Allegiance Reassignment. For the TARGET COLD RESET and TARGET WARM RESET functions, the tar- get cancels all pending operations across all Logical Units known to the issuing initiator. For the TARGET COLD RESET function, the tar- get MUST then close all of its TCP connections to all initiators (terminates all sessions). The mapping of the response code into a SCSI service response code value, if needed, is outside the scope of this document. However, in symbolic terms Response value 0 maps to the SCSI service response of FUNCTION COMPLETE. All other Response values map to the SCSI ser- vice response of FUNCTION REJECTED. If a Task Management function response PDU does not arrive before the session is terminated, the SCSI service response is SERVICE DELIVERY OR TARGET FAILURE The response to ABORT TASK SET and CLEAR TASK SET MUST be issued by the target only after all the commands affected have been received by the target, the corresponding task management functions have been executed by the SCSI target and the delivery of all responses deliv- ered until the task management function completion have been con- firmed (acknowledged through ExpStatSN) by the initiator on all connections of this session. For the exact timeline of events, refer Section 9.6.2 Task Management actions on task sets. For the ABORT TASK function, a) if the Referenced Task Tag identifies a valid task leading to a successful termination, targets must return the "Function com- plete" response. b) if the Referenced Task Tag does not identify an existing task but if the CmdSN indicated by the RefCmdSN field in the Task Man- Julian Satran Expires February 2003 151 iSCSI 5-August-02 agement function request is within the valid CmdSN window (between MaxCmdSN and ExpCmdSN), targets must consider the CmdSN received and return the "Function complete" response. c) if the Referenced Task Tag does not identify an existing task and if the CmdSN indicated by the RefCmdSN field in the Task Man- agement function request is outside the valid CmdSN window, tar- gets must return the "Task does not exist" response. 9.6.2 Task Management actions on task sets The execution of ABORT TASK SET and CLEAR TASK SET Task Management function requests consists of the following sequence of events in the specified order on each of the entities. The initiator: a) issues ABORT TASK SET/CLEAR TASK SET request. b) continues to respond to each target transfer tag received for the affected task set. c) receives any responses for the tasks in the affected task set (may process them as usual because they are guaranteed to be valid). d) receives the task set management response, thus concluding all the tasks in the affected task set. The target: a) receives the ABORT TASK SET/CLEAR TASK SET request. b) waits for all target transfer tags to be responded and also for all affected tasks in the task set to be received. c) propagates the command up to and receives the response from the target SCSI layer. d) takes note of last-sent StatSN on each of the connections in the session, and waits for acknowledgement of each StatSN (may solicit for acknowledgement by way of a NOP-In). e) sends the task set management response. 9.6.3 TotalAHSLength and DataSegmentLength For this PDU TotalAHSLength and DataSegmentLength MUST be 0. Julian Satran Expires February 2003 152 iSCSI 5-August-02 9.7 SCSI Data-out & SCSI Data-in The SCSI Data-out PDU for WRITE operations has the following format: Byte/ 0 | 1 | 2 | 3 | / | | | | |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7| +---------------+---------------+---------------+---------------+ 0|.|.| 0x05 |F| Reserved | +---------------+---------------+---------------+---------------+ 4|TotalAHSLength | DataSegmentLength | +---------------+---------------+---------------+---------------+ 8| LUN or Reserved | + + 12| | +---------------+---------------+---------------+---------------+ 16| Initiator Task Tag | +---------------+---------------+---------------+---------------+ 20| Target Transfer Tag or 0xffffffff | +---------------+---------------+---------------+---------------+ 24| Reserved | +---------------+---------------+---------------+---------------+ 28| ExpStatSN | +---------------+---------------+---------------+---------------+ 32| Reserved | +---------------+---------------+---------------+---------------+ 36| DataSN | +---------------+---------------+---------------+---------------+ 40| Buffer Offset | +---------------+---------------+---------------+---------------+ 44| Reserved | +---------------+---------------+---------------+---------------+ 48| Header-Digest (Optional) | +---------------+---------------+---------------+---------------+ / DataSegment / +/ / +---------------+---------------+---------------+---------------+ | Data-Digest (Optional) | +---------------+---------------+---------------+---------------+ The SCSI Data-in PDU for READ operations has the following format: Julian Satran Expires February 2003 153 iSCSI 5-August-02 Byte/ 0 | 1 | 2 | 3 | / | | | | |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7| +---------------+---------------+---------------+---------------+ 0|.|.| 0x25 |F|A|0 0 0|O|U|S| Reserved |Status or Rsvd | +---------------+---------------+---------------+---------------+ 4|TotalAHSLength | DataSegmentLength | +---------------+---------------+---------------+---------------+ 8| LUN or Reserved | + + 12| | +---------------+---------------+---------------+---------------+ 16| Initiator Task Tag | +---------------+---------------+---------------+---------------+ 20| Target Transfer Tag or 0xffffffff | +---------------+---------------+---------------+---------------+ 24| StatSN or Reserved | +---------------+---------------+---------------+---------------+ 28| ExpCmdSN | +---------------+---------------+---------------+---------------+ 32| MaxCmdSN | +---------------+---------------+---------------+---------------+ 36| DataSN | +---------------+---------------+---------------+---------------+ 40| Buffer Offset | +---------------+---------------+---------------+---------------+ 44| Residual Count | +---------------+---------------+---------------+---------------+ 48| Header-Digest (Optional) | +---------------+---------------+---------------+---------------+ / DataSegment / +/ / +---------------+---------------+---------------+---------------+ | Data-Digest (Optional) | +---------------+---------------+---------------+---------------+ Status can accompany the last Data-in PDU if the command did not end with an exception (i.e., the status is "good status" - GOOD, CONDI- TION MET or INTERMEDIATE CONDITION MET). The presence of status (and of a residual count) is signaled though the S flag bit. Although targets MAY choose to send even non-exception status in separate Julian Satran Expires February 2003 154 iSCSI 5-August-02 responses, initiators MUST support non-exception status in Data-In PDUs. 9.7.1 F (Final) Bit For outgoing data, this bit is 1 for the last PDU of unsolicited data or the last PDU of a sequence that answers an R2T. For incoming data, this bit is 1 for the last input (read) data PDU of a sequence. Input can be split into several sequences, each hav- ing its own F bit. Splitting the data stream into sequences does not affect DataSN counting on Data-In PDUs. It MAY be used as a "change direction" indication for Bidirectional operations that need such a change. DataSegmentLength MUST not exceed MaxRecvDataSegmentLength for the direction it is sent and the total of all the DataSegmentLength of all PDUs in a sequence MUST not exceed MaxBurstLength (or FirstBurst- Length for unsolicited data). However the number of individual PDUs in a sequence (or in total) may be higher than the MaxBurstLength (or FirstBurstLength) to MaxRecvDataSegmentLength ratio (as PDUs may be limited in length by the sender capabilities). Using DataSeg- mentLength of 0 may increase beyond what is reasonable the number of PDUs and should therefore be avoided. For Bidirectional operations, the F bit is 1 for both the end of the input sequences as well as the end of the output sequences. 9.7.2 A (Acknowledge) bit For sessions with ErrorRecoveryLevel 1 or higher, the target sets this bit to 1 to indicate that it requests a positive acknowledge- ment from the initiator for the data received. The target should use the A bit moderately; it MAY set the A bit to 1 only once every Max- BurstLength bytes or on the last Data-In PDU that concludes the entire requested read data transfer for the task from the target's perspective, and MUST NOT do so more frequently than this. The tar- get MUST NOT set to 1 the A bit for sessions with ErrorRecovery- Level=0. The initiator MUST ignore the A bit set to 1 for sessions with ErrorRecoveryLevel=0 On receiving a Data-In PDU with the A bit set to 1on a session with ErrorRecoveryLevel greater than 0, if there are no holes in the read data until that Data-In PDU, the initiator MUST issue a SNACK of type Julian Satran Expires February 2003 155 iSCSI 5-August-02 DataACK except when it is able to acknowledge the status for the task immediately via ExpStatSN on other outbound PDUs if the status for the task is also received; in this latter case (acknowledgement through ExpStatSN) sending a SNACK of type DataACK in response to the A bit is not mandatory but if it is done it must not be sent after the status acknowledgement through ExpStatSN. If the initiator has detected holes in the read data prior to that Data-In PDU, it MUST postpone issuing the SNACK of type DataACK until the holes are filled. An initiator also MUST NOT acknowledge the status for the task before those holes are filled. A status acknowledgement for a task that generated the Data-In PDUs is considered by the target as an implicit acknowledgement of the Data-In PDUs if such an acknowl- edgement was requested by the target. 9.7.3 Flags (byte 1) The last SCSI Data packet sent from a target to an initiator for a SCSI command that completed successfully (with a status of GOOD, CON- DITION MET, INTERMEDIATE or INTERMEDIATE CONDITION MET) may also optionally contain the Status for the data transfer. In this case, Sense Data cannot be sent together with the Command Status. If the command is completed with an error, then the response and sense data MUST be sent in a SCSI Response PDU (i.e., MUST NOT be sent in a SCSI Data packet). For Bidirectional commands, the status MUST be sent in a SCSI Response PDU. bit 2-3 - Reserved bit 5-6 - used the same as in a SCSI Response. Those bits are valid only when S is set to 1.For details see Section 9.4.1 Flags (byte 1). bit 7 S (status)- set to indicate that the Command Status field contains status. If this bit is set to 1 the F bit MUST also be set to 1. The fields StatSN, Status and Residual Count have meaningful content only if the S bit is set to 1 and their values are defined in Sec- tion 9.4 SCSI Response. 9.7.4 Target Transfer Tag On outgoing data, the Target Transfer Tag is provided to the target if the transfer is honoring an R2T. In this case, the Target Trans- Julian Satran Expires February 2003 156 iSCSI 5-August-02 fer Tag field is a replica of the Target Transfer Tag provided with the R2T. On incoming data, the Target Transfer Tag and LUN MUST be provided by the target if the A bit is set to 1; otherwise they are reserved. The Target Transfer Tag and LUN are copied by the initiator into the SNACK of type DataACK that it issues as a result of receiving a SCSI Data-in PDU with the A bit set to 1. The Target Transfer Tag values are not specified by this protocol except that the value 0xffffffff is reserved and means that the Tar- get Transfer Tag is not supplied. If the Target Transfer Tag is pro- vided, then the LUN field MUST hold a valid value and be consistent with whatever was specified with the command; otherwise, the LUN field is reserved. 9.7.5 DataSN For input (read) or bidirectional Data-In PDUs, the DataSN is the input PDU number within the data transfer for the command identified by the Initiator Task Tag. R2T and Data-In PDUs, in the context of bidirectional commands, share the numbering sequence (see Section 2.2.2.3 Data Sequencing). For output (write) data PDUs, the DataSN is the Data-Out PDU number within the current output sequence. The current output sequence is either identified by the Initiator Task Tag (for unsolicited data) or is a data sequence generated for one R2T (for data solicited through R2T). 9.7.6 Buffer Offset The Buffer Offset field contains the offset of this PDU payload data within the complete data transfer. The sum of the buffer offset and length should not exceed the expected transfer length for the com- mand. The order of data PDUs within a sequence is determined by DataPDU- InOrder. When set to Yes, it means that PDUs have to be in increas- ing Buffer Offset order and overlays are forbidden. Julian Satran Expires February 2003 157 iSCSI 5-August-02 The ordering between sequences is determined by DataSequenceInOrder. When set to Yes, it means that sequences have to be in increasing Buffer Offset order and overlays are forbidden. 9.7.7 DataSegmentLength This is the data payload length of a SCSI Data-In or SCSI Data-Out PDU. The sending of 0 length data segments should be avoided, but initiators and targets MUST be able to properly receive 0 length data segments. The Data Segments of Data-in and Data-out PDUs SHOULD be filled to the integer number of 4 byte words (real payload) unless the F bit is set to 1. Julian Satran Expires February 2003 158 iSCSI 5-August-02 9.8 Ready To Transfer (R2T) Byte/ 0 | 1 | 2 | 3 | / | | | | |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7| +---------------+---------------+---------------+---------------+ 0|.|.| 0x31 |1| Reserved | +---------------+---------------+---------------+---------------+ 4|TotalAHSLength | DataSegmentLength | +---------------+---------------+---------------+---------------+ 8| LUN | + + 12| | +---------------+---------------+---------------+---------------+ 16| Initiator Task Tag | +---------------+---------------+---------------+---------------+ 20| Target Transfer Tag | +---------------+---------------+---------------+---------------+ 24| StatSN | +---------------+---------------+---------------+---------------+ 28| ExpCmdSN | +---------------+---------------+---------------+---------------+ 32| MaxCmdSN | +---------------+---------------+---------------+---------------+ 36| R2TSN | +---------------+---------------+---------------+---------------+ 40| Buffer Offset | +---------------+---------------+---------------+---------------+ 44| Desired Data Transfer Length | +---------------------------------------------------------------+ 48| Header-Digest (Optional) | +---------------+---------------+---------------+---------------+ When an initiator has submitted a SCSI Command with data that passes from the initiator to the target (WRITE), the target may specify which blocks of data it is ready to receive. The target may request that the data blocks be delivered in whichever order is convenient for the target at that particular instant. This information is passed from the target to the initiator in the Ready To Transfer (R2T) PDU. Julian Satran Expires February 2003 159 iSCSI 5-August-02 In order to allow write operations without an explicit initial R2T, the initiator and target MUST have negotiated the key InitialR2T to No during Login. An R2T MAY be answered with one or more SCSI Data-out PDUs with a matching Target Transfer Tag. If an R2T is answered with a single Data-out PDU, the Buffer Offset in the Data PDU MUST be the same as the one specified by the R2T and the data length of the Data PDU MUST be the same as the Desired Data Transfer Length specified in the R2T. If the R2T is answered with a sequence of Data PDUs, the Buffer Off- set and Length MUST be within the range of those specified by R2T, and the last PDU MUST have the F bit set to 1. If the last PDU (marked with the F bit) is received before the Desired Data Transfer Length is transferred, a target MAY choose to Reject that PDU with "Protocol error" reason code. DataPDUInOrder governs the Data-Out PDU ordering. If DataPDUInOrder is set to Yes, the Buffer Offsets and Lengths for consecutive PDUs MUST form a continuous non-overlapping range and the PDUs MUST be sent in increasing offset order. The target may send several R2T PDUs. It, therefore, can have a num- ber of pending data transfers. The number of outstanding R2T PDUs are limited by the value of the negotiated key MaxOutstandingR2T. Within a connection, outstanding R2Ts MUST be fulfilled by the initi- ator in the order in which they were received. R2T PDUs MAY also be used to recover Data Out PDUs. Such an R2T (Recovery-R2T) is generated by a target upon detecting the loss of one or more Data-Out PDUs through due to: - a digest error - a sequence error - a sequence timeout A Recovery-R2T carries the next unused R2TSN, but requests part of or the entire data burst that an earlier R2T (with a lower R2TSN) had already requested. DataSequenceInOrder governs the buffer offset ordering in consecu- tive R2Ts. If DataSequenceInOrder is Yes, then consecutive R2Ts MUST refer to continuous non-overlapping ranges except for Recovery-R2Ts. 9.8.1 TotalAHSLength and DataSegmentLength For this PDU TotalAHSLength and DataSegmentLength MUST be 0. Julian Satran Expires February 2003 160 iSCSI 5-August-02 9.8.2 R2TSN R2TSN is the R2T PDU input PDU number within the command identified by the Initiator Task Tag. For bidirectional commands R2T and Data-In PDUs share the input PDU numbering sequence (see Section 2.2.2.3 Data Sequencing). 9.8.3 StatSN The StatSN field will contain the next StatSN. The StatSN for this connection is not advanced after this PDU is sent. 9.8.4 Desired Data Transfer Length and Buffer Offset The target specifies how many bytes it wants the initiator to send because of this R2T PDU. The target may request the data from the initiator in several chunks, not necessarily in the original order of the data. The target, therefore, also specifies a Buffer Offset that indicates the point at which the data transfer should begin, rela- tive to the beginning of the total data transfer. The Desired Data Transfer Length MUST NOT be 0 and MUST not exceed MaxBurstLength. 9.8.5 Target Transfer Tag The target assigns its own tag to each R2T request that it sends to the initiator. This tag can be used by the target to easily identify the data it receives. The Target Transfer Tag and LUN are copied in the outgoing data PDUs and are used by the target only. There is no protocol rule about the Target Transfer Tag except that the value 0xffffffff is reserved and MUST NOT be sent by a target in an R2T. Julian Satran Expires February 2003 161 iSCSI 5-August-02 9.9 Asynchronous Message An Asynchronous Message may be sent from the target to the initiator without corresponding to a particular command. The target specifies the reason for the event and sense data. Byte/ 0 | 1 | 2 | 3 | / | | | | |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7| +---------------+---------------+---------------+---------------+ 0|.|.| 0x32 |1| Reserved | +---------------+---------------+---------------+---------------+ 4|TotalAHSLength | DataSegmentLength | +---------------+---------------+---------------+---------------+ 8| LUN or Reserved | + + 12| | +---------------+---------------+---------------+---------------+ 16| 0xffffffff | +---------------+---------------+---------------+---------------+ 20| Reserved | +---------------+---------------+---------------+---------------+ 24| StatSN | +---------------+---------------+---------------+---------------+ 28| ExpCmdSN | +---------------+---------------+---------------+---------------+ 32| MaxCmdSN | +---------------+---------------+---------------+---------------+ 36| AsyncEvent | AsyncVCode | Parameter1 or Reserved | +---------------+---------------+---------------+---------------+ 40| Parameter2 or Reserved | Parameter3 or Reserved | +---------------+---------------+---------------+---------------+ 44| Reserved | +---------------+---------------+---------------+---------------+ 48| Header-Digest (Optional) | +---------------+---------------+---------------+---------------+ / DataSegment - Sense Data and iSCSI Event Data / +/ / +---------------+---------------+---------------+---------------+ | Data-Digest (Optional) | +---------------+---------------+---------------+---------------+ Julian Satran Expires February 2003 162 iSCSI 5-August-02 Some Asynchronous Messages are strictly related to iSCSI while oth- ers are related to SCSI [SAM2]. StatSN counts this PDU as an acknowledgeable event (StatSN is advanced), which allows for initiator and target state synchroniza- tion. 9.9.1 AsyncEvent The codes used for iSCSI Asynchronous Messages (Events) are: 0 - a SCSI Asynchronous Event is reported in the sense data. Sense Data that accompanies the report, in the data segment, identifies the condition. The sending of a SCSI Event (Asyn- chronous Event Reporting in SCSI terminology) is dependent on the target support for SCSI asynchronous event reporting (see [SAM2]) as indicated in the standard INQUIRY data (see [SPC]). Its use may be enabled by parameters in the SCSI Con- trol mode page (see [SPC]). 1 - target requests Logout. This Async Message MUST be sent on the same connection as the one requesting to be logged out. The initiator MUST honor this request by issuing a Logout as early as possible, but no later than Parameter3 seconds. Initiator MUST send a Logout with a reason code of "Close the connection" OR "Close the session" to close all the connec- tions. Once this message is received, the initiator SHOULD NOT issue new iSCSI commands on the connection to be logged out. The target MAY reject any new I/O requests that it receives after this Message with the reason code "Waiting for Logout". If the initiator does not Logout in Parameter3 sec- onds, the target should send an Async PDU with iSCSI event code "Dropped the connection" if possible, or simply termi- nate the transport connection. Parameter1 and Parameter2 are reserved. 2 - target indicates it will drop the connection. The Parameter1 field indicates the CID of the connection going to be dropped. The Parameter2 field (Time2Wait) indicates, in seconds, the minimum time to wait before attempting to reconnect or reas- sign. The Parameter3 field (Time2Retain) indicates the maximum time allowed to reassign commands after the initial wait (in Parameter2). If the initiator does not attempt to reconnect and/or reas- sign the outstanding commands within the time specified by Parameter3, or if Parameter3 is 0, the target will terminate all outstanding commands on this connection; no other Julian Satran Expires February 2003 163 iSCSI 5-August-02 responses should be expected from the target for the out- standing commands on this connection in this case. A value of 0 for Parameter2 indicates that reconnect can be attempted immediately. 3 - target indicates it will drop all the connections of this session. Parameter1 field is reserved. The Parameter2 field (Time2Wait) indicates, in seconds, the minimum time to wait before attempting to reconnect. The Parameter3 field (Time2Retain) indicates the maximum time allowed to reassign commands after the initial wait (in Parameter2). If the initiator does not attempt to reconnect and/or reas- sign the outstanding commands within the time specified by Parameter3, or if Parameter3 is 0, the session is termi- nated. In this case, the target will terminate all outstand- ing commands in this session; no other responses should be expected from the target for the outstanding commands in this session. A value of 0 for Parameter2 indicates that recon- nect can be attempted immediately. 4 - target requests parameter negotiation on this connection. The initiator MUST honor this request by issuing a Text Request (that can be empty) on the same connection as early as possible, but no later than Parameter3 seconds, unless a Text Request is already pending on the connection, or by issuing a Logout Request. If the initiator does not issue a Text Request the target may reissue the Asynchronous Message requesting parameter negotiation. 255 - vendor specific iSCSI Event. The AsyncVCode details the vendor code, and data MAY accompany the report. All other event codes are reserved. 9.9.2 AsyncVCode AsyncVCode is a vendor specific detail code that is valid only if the AsyncEvent field indicates a vendor specific event. Otherwise, it is reserved. 9.9.3 LUN The LUN field MUST be valid if AsyncEvent is 0. Otherwise this field is reserved. Julian Satran Expires February 2003 164 iSCSI 5-August-02 9.9.4 Sense Data and iSCSI Event Data For a SCSI Event, this data accompanies the report in the data seg- ment and identifies the condition. For an iSCSI Event, additional vendor-unique data MAY accompany the Async event. Initiators MAY ignore the data when not understood while processing the rest of the PDU. If the DataSegmentLength is not 0, the format of the DataSegment is as follows: Byte/ 0 | 1 | 2 | 3 | / | | | | |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7| +---------------+---------------+---------------+---------------+ 0|SenseLength | Sense Data | +---------------+---------------+---------------+---------------+ x/ Sense Data / +---------------+---------------+---------------+---------------+ y/ iSCSI Event Data / / / +---------------+---------------+---------------+---------------+ z| 9.9.4.1 SenseLength Length of Sense Data. Julian Satran Expires February 2003 165 iSCSI 5-August-02 9.10 Text Request The Text Request is provided to allow for the exchange of informa- tion and for future extensions. It permits the initiator to inform a target of its capabilities or to request some special operations. Byte/ 0 | 1 | 2 | 3 | / | | | | |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7| +---------------+---------------+---------------+---------------+ 0|.|I| 0x04 |F|C| Reserved | +---------------+---------------+---------------+---------------+ 4|TotalAHSLength | DataSegmentLength | +---------------+---------------+---------------+---------------+ 8| LUN or Reserved | + + 12| | +---------------+---------------+---------------+---------------+ 16| Initiator Task Tag | +---------------+---------------+---------------+---------------+ 20| Target Transfer Tag or 0xffffffff | +---------------+---------------+---------------+---------------+ 24| CmdSN | +---------------+---------------+---------------+---------------+ 28| ExpStatSN | +---------------+---------------+---------------+---------------+ 32/ Reserved / +/ / +---------------+---------------+---------------+---------------+ 48| Header-Digest (Optional) | +---------------+---------------+---------------+---------------+ / DataSegment (Text) / +/ / +---------------+---------------+---------------+---------------+ | Data-Digest (Optional) | +---------------+---------------+---------------+---------------+ An initiator MUST have at most one outstanding Text Request on a con- nection at any given time. Julian Satran Expires February 2003 166 iSCSI 5-August-02 On a connection failure, an initiator must either explicitly abort any active allegiant text negotiation task or must cause such a task to be implicitly terminated by the target. 9.10.1 F (Final) Bit When set to 1, indicates that this is the last or only text request in a sequence of Text Requests; otherwise, it indicates that more Text Requests will follow. 9.10.2 C (Continue) Bit When set to 1, indicates that the text (set of key=value pairs) in this Text Request is not complete (it will be continued on subse- quent Text Requests); otherwise, it indicates that this Text Request ends a set of key=value pairs. A Text Request with the C bit set to 1 MUST have the F bit set to 0. 9.10.3 Initiator Task Tag The initiator assigned identifier for this Text Request. If the com- mand is sent as part of a sequence of text requests and responses, the Initiator Task Tag MUST be the same for all the requests within the sequence (similar to linked SCSI commands). The I bit for all requests in a sequence also MUST be the same. 9.10.4 Target Transfer Tag When the Target Transfer Tag is set to the reserved value 0xffffffff, it tells the target that this is a new request and the target resets any internal state associated with the Initiator Task Tag (resets the current negotiation state). The target sets the Target Transfer Tag in a text response to a value other than the reserved value 0xffffffff whenever it indicates that it has more data to send or more operations to perform that are asso- ciated with the specified Initiator Task Tag. It MUST do so whenever it sets the F bit to 0 in the response. By copying the Target Trans- fer Tag from the response to the next Text Request, the initiator tells the target to continue the operation for the specific Initia- tor Task Tag. The initiator MUST ignore the Target Transfer Tag in the Text Response when the F bit is set to 1. Julian Satran Expires February 2003 167 iSCSI 5-August-02 This mechanism allows the initiator and target to transfer a large amount of textual data over a sequence of text-command/text-response exchanges or to perform extended negotiation sequences. If the Target Transfer Tag is not 0xffffffff the LUN field MUST be the one sent by the target in the Text Response. A target MAY reset its internal negotiation state if an exchange is stalled by the initiator for a long time or if it is running out of resources. Long text responses are handled as in the following example: I->T Text SendTargets=All (F=1,TTT=0xffffffff) T->I Text <part 1> (F=0,TTT=0x12345678) I->T Text <empty> (F=1, TTT=0x12345678) T->I Text <part 2> (F=0, TTT=0x12345678) I->T Text <empty> (F=1, TTT=0x12345678) ... T->I Text <part n> (F=1, TTT=0xffffffff) 9.10.5 Text The data lengths of a text request MUST NOT exceed the iSCSI target MaxRecvDataSegmentLength (a per connection and per direction negoti- ated parameter). The text format is specified in Section 4.2 Text Mode Negotiation. Chapter 10 and Chapter 11 list some basic Text key=value pairs, some of which can be used in Login Request/Response and some in Text Request/Response. A key=value pair can span Text request or response boundaries (i.e., a key=value pair can start in one PDU and continue on the next - in other words the end of a PDU does not necessarily signal the end of a key value pair). The target responds by sending its response back to the initiator. The response text format is similar to the request text format. The text response MAY refer to key=value pairs presented in an ear- lier text request and the text in the request may refer to earlier responses. Chapter 4 details the rules for the Text Requests and Responses. Julian Satran Expires February 2003 168 iSCSI 5-August-02 Text operations are usually meant for parameter setting/negotia- tions, but can also be used to perform some long lasting operations. Text operations that take a long time should be placed in their own Text request. Julian Satran Expires February 2003 169 iSCSI 5-August-02 9.11 Text Response The Text Response PDU contains the target's responses to the initia- tor's Text request. The format of the Text field matches that of the Text request. Byte/ 0 | 1 | 2 | 3 | / | | | | |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7| +---------------+---------------+---------------+---------------+ 0|.|.| 0x24 |F|C| Reserved | +---------------+---------------+---------------+---------------+ 4|TotalAHSLength | DataSegmentLength | +---------------+---------------+---------------+---------------+ 8| LUN or Reserved | + + 12| | +---------------+---------------+---------------+---------------+ 16| Initiator Task Tag | +---------------+---------------+---------------+---------------+ 20| Target Transfer Tag or 0xffffffff | +---------------+---------------+---------------+---------------+ 24| StatSN | +---------------+---------------+---------------+---------------+ 28| ExpCmdSN | +---------------+---------------+---------------+---------------+ 32| MaxCmdSN | +---------------+---------------+---------------+---------------+ 36/ Reserved / +/ / +---------------+---------------+---------------+---------------+ 48| Header-Digest (Optional) | +---------------+---------------+---------------+---------------+ / DataSegment (Text) / +/ / +---------------+---------------+---------------+---------------+ | Data-Digest (Optional) | +---------------+---------------+---------------+---------------+ 9.11.1 F (Final) Bit When set to 1, in response to a Text Request with the Final bit set to 1, the F bit indicates that the target has finished the whole operation. Otherwise, if set to 0 in response to a Text Request with Julian Satran Expires February 2003 170 iSCSI 5-August-02 the Final Bit set to 1, it indicates that the target has more work to do (invites a follow-on text request). A Text Response with the F bit set to 1 in response to a Text Request with the F bit set to 0 is a protocol error. A Text Response with the F bit set to 1 MUST NOT contain key=value pairs that may require additional answers from the initiator. A Text Response with the F bit set to 1 MUST have a Target Transfer Tag field set to the reserved value of 0xffffffff. A Text Response with the F bit set to 0 MUST have a Target Transfer Tag field set to a value other than the reserved 0xffffffff. 9.11.2 C (Continue) Bit When set to 1, indicates that the text (set of key=value pairs) in this Text Response is not complete (it will be continued on subse- quent Text Responses); otherwise, it indicates that this Text Response ends a set of key=value pairs. A Text Response with the C bit set to 1 MUST have the F bit set to 0. 9.11.3 Initiator Task Tag The Initiator Task Tag matches the tag used in the initial Text Request. 9.11.4 Target Transfer Tag When a target has more work to do (e.g., cannot transfer all the remaining text data in a single Text Response or has to continue the negotiation) and has enough resources to proceed, it MUST set the Target Transfer Tag to a value other than the reserved value of 0xffffffff. Otherwise the Target Transfer Tag MUST be set to 0xffffffff. When the Target Transfer Tag is not 0xffffffff the LUN field may be significant. The initiator MUST copy the Target Transfer Tag and LUN in its next request to indicate that it wants the rest of the data. When the target receives a Text Request with the Target Transfer Tag set to the reserved value of 0xffffffff, it resets its internal Julian Satran Expires February 2003 171 iSCSI 5-August-02 information (resets state) associated with the given Initiator Task Tag. When a target cannot finish the operation in a single Text Response, and does not have enough resources to continue it rejects the Text Request with the appropriate Reject code. A target may reset its internal state associated with an Initiator Task Tag (the current negotiation state), state expressed through the Target Transfer Tag if the initiator fails to continue the exchange for some time. The target may reject subsequent Text Requests with the Target Transfer Tag set to the "stale" value. 9.11.5 StatSN The target StatSN variable is advanced by each Text Response sent. 9.11.6 Text Response Data The data lengths of a text response MUST NOT exceed the iSCSI initia- tor MaxRecvDataSegmentLength (a per connection and per direction negotiated parameter). The text in the Text Response Data is governed by the same rules as the text in the Text Request Data (see Section 9.10.5 Text). Although the initiator is the requesting party and controls the request-response initiation and termination, the target can offer key=value pairs of its own as part of a sequence and not only in response to the initiator. Julian Satran Expires February 2003 172 iSCSI 5-August-02 9.12 Login Request After establishing a TCP connection between an initiator and a tar- get, the initiator MUST start a Login Phase to gain further access to the target's resources. The Login Phase (see Chapter 4) consists of a sequence of Login requests and responses that carry the same Initiator Task Tag. Login requests are always considered as immediate. Byte/ 0 | 1 | 2 | 3 | / | | | | |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7| +---------------+---------------+---------------+---------------+ 0|.|1| 0x03 |T|C|.|.|CSG|NSG| Version-max | Version-min | +---------------+---------------+---------------+---------------+ 4|TotalAHSLength | DataSegmentLength | +---------------+---------------+---------------+---------------+ 8| ISID | + +---------------+---------------+ 12| | TSIH | +---------------+---------------+---------------+---------------+ 16| Initiator Task Tag | +---------------+---------------+---------------+---------------+ 20| CID | Reserved | +---------------+---------------+---------------+---------------+ 24| CmdSN | +---------------+---------------+---------------+---------------+ 28| ExpStatSN or Reserved | +---------------+---------------+---------------+---------------+ 32| Reserved | +---------------+---------------+---------------+---------------+ 36| Reserved | +---------------+---------------+---------------+---------------+ 40/ Reserved / +/ / +---------------+---------------+---------------+---------------+ 48/ DataSegment - Login Parameters in Text request Format / +/ / +---------------+---------------+---------------+---------------+ Julian Satran Expires February 2003 173 iSCSI 5-August-02 9.12.1 T (Transit) Bit If set to 1, indicates that the initiator is ready to transit to the next stage. If the T bit is set to 1 and NSG is FullFeaturePhase, then this also indicates that the initiator is ready for the Final Login Response (see Chapter 4). 9.12.2 C (Continue) Bit When set to 1, indicates that the text (set of key=value pairs) in this Login Request is not complete (it will be continued on subse- quent Login Requests); otherwise, it indicates that this Login Request ends a set of key=value pairs. A Login Request with the C bit set to 1 MUST have the T bit set to 0. 9.12.3 CSG and NSG Through these fields, Current Stage (CSG) and Next Stage (NSG), the Login negotiation requests and responses are associated with a spe- cific stage in the session (SecurityNegotiation, LoginOperationalNe- gotiation, FullFeaturePhase) and may indicate the next stage they want to move to (see Chapter 4). The next stage value is valid only when the T bit is 1; otherwise, it is reserved. The stage codes are: - 0 - SecurityNegotiation - 1 - LoginOperationalNegotiation - 3 - FullFeaturePhase 9.12.4 Version The version number of the current draft is 0x00. As such, all devices MUST carry version 0x00 for both Version-min and Version-max. 9.12.4.1 Version-max Maximum Version number supported. All Login requests within the Login Phase MUST carry the same Ver- sion-max. The target MUST use the value presented with the first login request. Julian Satran Expires February 2003 174 iSCSI 5-August-02 9.12.4.2 Version-min All Login requests within the Login Phase MUST carry the same Ver- sion-min. The target MUST use the value presented with the first login request. 9.12.5 ISID This is an initiator-defined component of the session identifier and is structured as follows (see [NDT] and Section 8.1.1 Conservative Reuse of ISIDs for details): Byte/ 0 | 1 | 2 | 3 | / | | | | |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7| +---------------+---------------+---------------+---------------+ 8| T | A | B | C | +---------------+---------------+---------------+---------------+ 12| D | +---------------+---------------+ The T field identifies the format and usage of A, B, C & D as indi- cated bellow: T 00b OUI-format A&B are a 22 bit OUI (the I/G & U/L bits are omitted) C&D 24 bit qualifier 01b EN - format (IANA Enterprise Number) A - reserved B&C EN (IANA Enterprise Number) D - Qualifier 10b "Random" A - reserved B&C Random D - Qualifier 11b A,B,C&D Reserved For the T field values 00b and 01b a combination of A and B (for 00b) or B and C (for 01b) identifies the vendor or organization whose com- ponent (software or hardware) generates this ISID. A vendor or orga- Julian Satran Expires February 2003 175 iSCSI 5-August-02 nization with one or more OUIs, or one or more Enterprise Numbers, MUST use at least one of these numbers and select the appropriate value for the T field when its components generate ISIDs. An OUI or EN MUST be set in the corresponding fields in network byte order (byte big-endian). If the T field is 10b, B and C are set to a random 24bit unsigned integer value in network byte order (byte big-endian). See [NDT] for how this affects the principle of "conservative reuse". The Qualifier field is a 16 or 24 bit unsigned integer value that provides a range of possible values for the ISID within the selected namespace. It may be set to any value, within the constraints speci- fied in the iSCSI protocol (see Section 2.4.3 Consequences of the Model and Section 8.1.1 Conservative Reuse of ISIDs). The T field value of 11b is reserved. If the ISID is derived from something assigned to a hardware adapter or interface by a vendor, as a preset default value, it MUST be con- figurable to a value assigned according to the SCSI port behavior desired by the system in which it is installed (see Section 8.1.1 Conservative Reuse of ISIDs and Section 8.1.2 iSCSI Name, ISID and TPGT Use) and the resultant ISID MUST also be persistent over power cycles, reboot, card swap etc.. 9.12.6 TSIH TSIH must be set in the first Login Request. The reserved value 0 MUST be used on the first connection for a new session. Otherwise the TSIH sent by the target at the conclusion of successful login of the first connection for this session MUST be used. The TSIH identi- fies to the target the associated existing session for this new con- nection. All Login requests within a Login Phase MUST carry the same TSIH. The target MUST check the value presented with the first login request and act as specified in Section 4.3.1 Login Phase Start. 9.12.7 Connection ID - CID A unique ID for this connection within the session. Julian Satran Expires February 2003 176 iSCSI 5-August-02 All Login requests within the Login Phase MUST carry the same CID. The target MUST use the value presented with the first login request. A Login request with a non-zero TSIH and a CID equal to that of an existing connection implies a logout of the connection followed by a Login (see Section 4.3.4 Connection reinstatement). For the details of the implicit Logout Request see also Section 9.14 Logout Request. 9.12.8 CmdSN CmdSN is either the initial command sequence number of a session (for the first Login request of a session - the "leading" login) or the command sequence number in the command stream if the login is for a new connection in an existing session. Examples: - Login on a leading connection - if the leading login carries the CmdSN 123 all other login requests in the same login phase carry the CmdSN 123 and the first non-immediate com- mand in FullFeaturePhase also carries the CmdSN 123. - Login on other than a leading connection - if the current CmdSN at the time the first login on the connection is issued is 500 then that PDU carries CmdSN=500. Subsequent login requests that are needed to complete this login phase may carry a CmdSN higher than 500 if non-immediate requests that were issued on other connections in the same session advance CmdSN. If the login request is a leading login request the target MUST use the value presented in CmdSN as the target value for ExpCmdSN. 9.12.9 ExpStatSN For the first Login Request on a connection this is ExpStatSN for the old connection and this field is valid only if the Login request restarts a connection (see Section 4.3.4 Connection reinstatement). For subsequent Login Requests it is used to acknowledge the Login Responses with their increasing StatSN values. Julian Satran Expires February 2003 177 iSCSI 5-August-02 9.12.10 Login Parameters The initiator MUST provide some basic parameters in order to enable the target to determine if the initiator may use the target's resources and the initial text parameters for the security exchange. All the rules specified in Section 9.10.5 Text for text requests also hold for login requests. Keys and their explanations are listed in Chapter 10 (security negotiation keys) and Chapter 11 (operational parameter negotiation keys). All keys in Chapter 11, except for the X extension formats, MUST be supported by iSCSI initiators and tar- gets. Keys in Chapter 10 only need to be supported when the function to which they refer is mandatory to implement. Julian Satran Expires February 2003 178 iSCSI 5-August-02 9.13 Login Response The Login Response indicates the progress and/or end of the Login Phase. Byte/ 0 | 1 | 2 | 3 | / | | | | |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7| +---------------+---------------+---------------+---------------+ 0|.|.| 0x23 |T|C|.|.|CSG|NSG| Version-max | Version-active| +---------------+---------------+---------------+---------------+ 4|TotalAHSLength | DataSegmentLength | +---------------+---------------+---------------+---------------+ 8| ISID | + +---------------+---------------+ 12| | TSIH | +---------------+---------------+---------------+---------------+ 16| Initiator Task Tag | +---------------+---------------+---------------+---------------+ 20| Reserved | +---------------+---------------+---------------+---------------+ 24| StatSN | +---------------+---------------+---------------+---------------+ 28| ExpCmdSN | +---------------+---------------+---------------+---------------+ 32| MaxCmdSN | +---------------+---------------+---------------+---------------+ 36| Status-Class | Status-Detail | Reserved | +---------------+---------------+---------------+---------------+ 40/ Reserved / +/ / +---------------+---------------+---------------+---------------+ 48/ DataSegment - Login Parameters in Text request Format / +/ / +---------------+---------------+---------------+---------------+ 9.13.1 Version-max This is the highest version number supported by the target. All Login responses within the Login Phase MUST carry the same Ver- sion-max. Julian Satran Expires February 2003 179 iSCSI 5-August-02 The initiator MUST use the value presented as a response to the first login request. 9.13.2 Version-active Indicates the highest version supported by the target and initiator. If the target does not support a version within the range specified by the initiator, the target rejects the login and this field indi- cates the lowest version supported by the target. All Login responses within the Login Phase MUST carry the same Ver- sion-active. The initiator MUST use the value presented as a response to the first login request. 9.13.3 TSIH The TSIH is the target assigned session identifying handle and its internal format and content are not defined by this protocol except for the value 0 that is reserved. Except for the Login Final-Response in a new session, this field should be set to the TSIH provided by the initiator in the Login Request. For a new session, the target MUST generate a non-zero TSIH and return it ONLY in the Login Final- Response (see Section 4.3 Login Phase). 9.13.4 StatSN For the first Login Response (the response to the first Login Request), this is the starting status Sequence Number for the connec- tion. The next response of any kind, including the next login response, if any, in the same Login Phase, will carry this number + 1. This field is valid only if the Status-Class is 0. 9.13.5 Status-Class and Status-Detail The Status returned in a Login Response indicates the execution sta- tus of the Login Phase. The status includes: Status-Class Status-Detail 0 Status-Class indicates success. Julian Satran Expires February 2003 180 iSCSI 5-August-02 A non-zero Status-Class indicates an exception. In this case, Status- Class is sufficient for a simple initiator to use when handling exceptions, without having to look at the Status-Detail. The Status- Detail allows finer-grained exception handling for more sophisti- cated initiators, as well as better information for logging. The status classes are as follows: 0 - Success - indicates that the iSCSI target successfully received, understood, and accepted the request. The number- ing fields (StatSN, ExpCmdSN, MaxCmdSN) are valid only if Status-Class is 0. 1 - Redirection - indicates that the initiator must take fur- ther action to complete the request. This is usually due to the target moving to a different address. All of the redirec- tion status class responses MUST return one or more text key parameters of the type "TargetAddress", which indicates the target's new address. 2 - Initiator Error (not a format error) - indicates that the initiator most likely caused the error. This MAY be due to a request for a resource for which the initiator does not have permission. The request should not be tried again. 3 - Target Error - indicates that the target sees no errors in the initiator's login request, but is currently incapable of fulfilling the request. The initiator may re-try the same login request later. The table below shows all of the currently allocated status codes. The codes are in hexadecimal; the first byte is the status class and the second byte is the status detail. Julian Satran Expires February 2003 181 iSCSI 5-August-02 ----------------------------------------------------------------- Status | Code | Description |(hex) | ----------------------------------------------------------------- Success | 0000 | Login is proceeding OK (*1). ----------------------------------------------------------------- Target Moved | 0101 | The requested iSCSI Target Name (ITN) Temporarily | | has temporarily moved | | to the address provided. ----------------------------------------------------------------- Target Moved | 0102 | The requested ITN has permanently moved Permanently | | to the address provided. ----------------------------------------------------------------- Initiator | 0200 | Miscellaneous iSCSI initiator Error | | errors. ---------------------------------------------------------------- Authentication| 0201 | The initiator could not be Failure | | successfully authenticated. ----------------------------------------------------------------- Authorization | 0202 | The initiator is not allowed access Failure | | to the given target. ----------------------------------------------------------------- Not Found | 0203 | The requested ITN does not | | exist at this address. ----------------------------------------------------------------- Target Removed| 0204 | The requested ITN has been removed and | |no forwarding address is provided. ----------------------------------------------------------------- Unsupported | 0205 | The requested iSCSI version range is Version | | not supported by the target. ----------------------------------------------------------------- Too many | 0206 | Too many connections on this SSID connections | | ----------------------------------------------------------------- Missing | 0207 | Missing parameters (e.g., iSCSI parameter | | Initiator and/or Target Name). ----------------------------------------------------------------- Can't include | 0208 | Target does not support session in session | | spanning to this connection (address) ----------------------------------------------------------------- Session type | 0209 | Target does not support this type of Not supported | | of session or not from this Initiator. ----------------------------------------------------------------- Julian Satran Expires February 2003 182 iSCSI 5-August-02 Session does | 020a | Attempt to add a connection not exist | | to an non-existent session ----------------------------------------------------------------- Invalid during| 020b | Invalid Request type during Login login | | ----------------------------------------------------------------- Target Error | 0300 | Target hardware or software error. ----------------------------------------------------------------- Service | 0301 | The iSCSI service or target is not Unavailable | | currently operational. ----------------------------------------------------------------- Out of | 0302 | The target has insufficient session, Resources | | connection, or other resources. ----------------------------------------------------------------- (*1)If the response T bit is 1 in both the request and the matching response and the NSG is FullFeaturePhase in both the request and the matching response the Login Phase is finished and the initiator may proceed to issue SCSI commands. If the Status Class is not 0, the initiator and target MUST close the TCP connection. If the target wishes to reject the login request for more than one reason, it should return the primary reason for the rejection. 9.13.6 T (Transit) bit The T bit is set to 1 as an indicator of the end of the stage. If the T bit is set to 1 and NSG is FullFeaturePhase, then this is also the Final Login Response (see Chapter 4). A T bit of 0 indicates a "par- tial" response, which means "more negotiation needed". A login response with a T bit set to 1 MUST NOT contain key=value pairs that may require additional answers from the initiator within the same stage. If the status class is 0, the T bit MUST NOT be set to 1 if the T bit in the request was set to 0. 9.13.7 C (Continue) Bit When set to 1, indicates that the text (set of key=value pairs) in this Login Response is not complete (it will be continued on subse- Julian Satran Expires February 2003 183 iSCSI 5-August-02 quent Login Responses); otherwise, it indicates that this Login Response ends a set of key=value pairs. A Login Response with the C bit set to 1 MUST have the T bit set to 0. 9.13.8 Login Parameters The target MUST provide some basic parameters in order to enable the initiator to determine if is connected to the correct port and the initial text parameters for the security exchange. All the rules specified in Section 9.11.6 Text Response Data for text responses also hold for login responses. Keys and their explana- tions are listed in Chapter 10 (security negotiation keys) and Chap- ter 11 (operational parameter negotiation keys). All keys in Chapter 11, except for the X extension formats, MUST be supported by iSCSI initiators and targets. Keys in Chapter 10, only need to be sup- ported when the function to which they refer is mandatory to imple- ment. Julian Satran Expires February 2003 184 iSCSI 5-August-02 9.14 Logout Request The Logout request is used to perform a controlled closing of a con- nection. An initiator MAY use a logout request to remove a connection from a session or to close an entire session. After sending the Logout request PDU, an initiator MUST NOT send any new iSCSI requests on the closing connection. If the Logout request is intended to close the session, new iSCSI requests MUST NOT be sent on any of the connections participating in the session. When receiving a Logout request with the reason code of "close the connection" or "close the session", the target MUST terminate all pending commands, whether acknowledged via ExpCmdSN or not, on that connection or session respectively. When receiving a Logout request with the reason code "remove connec- tion for recovery", the target MUST discard all requests not yet acknowledged via ExpCmdSN that were issued on the specified connec- tion and suspend all data/status/R2T transfers on behalf of pending commands on the specified connection. The target then issues the Logout response and half-closes the TCP connection (sends FIN). After receiving the Logout response and attempting to receive the FIN (if still possible), the initiator MUST completely close the logging-out connection. For the terminated com- mands, no additional responses should be expected. A Logout for a CID may be performed on a different transport connec- tion when the TCP connection for the CID has already been termi- nated. In such a case, only a logical "closing" of the iSCSI connection for the CID is implied with a Logout. All commands that were not terminated or not completed (with status) and acknowledged when the connection is closed completely can be reassigned to a new connection if the target supports connection recovery. If an initiator intends to start recovery for a failing connection, it MUST use either the Logout request to "clean-up" the target end of a failing connection and enable recovery to start, or use the Login Julian Satran Expires February 2003 185 iSCSI 5-August-02 request with a non-zero TSIH and the same CID on a new connection for the same effect (see Section 9.14.3 CID). In sessions with a single connection, the connection can be closed then a new connection reopened and a connection reinstatement login can be used for recov- ery (see Section 4.3.4 Connection reinstatement). A successful completion of a logout request with the reason code of "close the connection" or "remove the connection for recovery" results at the target in the discarding of unacknowledged commands (commands that have arrived on the connection being logged out but have not been delivered to SCSI because one or more commands with a smaller CmdSN have not been received by iSCSI - see Section 2.2.2.1 Command Numbering and Acknowledging) received on the connection being logged out. The resulting holes in command sequence numbers will have to be handled by appropriate recovery (see Chapter 5) unless the session is also closed. The entire logout discussion in this section is applicable also for an implicit Logout effected by way of a connection reinstatement or session reinstatement. When a Login Request performs an implicit Logout, the implicit Logout is performed as if having the reason codes specified below: Reason code Type of implicit Logout ------------------------------------------- 0 session reinstatement 1 connection reinstatement when the operational ErrorRecoveryLevel < 2 2 connection reinstatement when the operational ErrorRecoveryLevel = 2 Julian Satran Expires February 2003 186 iSCSI 5-August-02 Byte/ 0 | 1 | 2 | 3 | / | | | | |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7| +---------------+---------------+---------------+---------------+ 0|.|I| 0x06 |1| Reason Code | Reserved | +---------------+---------------+---------------+---------------+ 4|TotalAHSLength | DataSegmentLength | +---------------------------------------------------------------+ 8/ Reserved / +/ / +---------------+---------------+---------------+---------------+ 16| Initiator Task Tag | +---------------+---------------+---------------+---------------+ 20| CID or Reserved | Reserved | +---------------+---------------+---------------+---------------+ 24| CmdSN | +---------------+---------------+---------------+---------------+ 28| ExpStatSN | +---------------+---------------+---------------+---------------+ 32/ Reserved / +/ / +---------------+---------------+---------------+---------------+ 48| Header-Digest (Optional) | +---------------+---------------+---------------+---------------+ 9.14.1 Reason Code Reason Code indicates the reason for Logout as follows: 0 - closes the session. All commands associated with the ses- sion (if any) are terminated. 1 - closes the connection. All commands associated with connec- tion (if any) are terminated. 2 - removes the connection for recovery. Connection is closed and all commands associated with it, if any, are to be pre- pared for a new allegiance. All other values are reserved. 9.14.2 TotalAHSLength and DataSegmentLength For this PDU TotalAHSLength and DataSegmentLength MUST be 0. Julian Satran Expires February 2003 187 iSCSI 5-August-02 9.14.3 CID This is the connection ID of the connection to be closed (including closing the TCP stream). This field is valid only if the reason code is not "close the session". 9.14.4 ExpStatSN This is the last ExpStatSN value for the connection to be closed. 9.14.5 Implicit termination of tasks A target implicitly terminates the active tasks in three cases due to iSCSI protocol: a) When a connection is implicitly or explicitly logged out with the Reason code of "Closes the connection" and there are active tasks allegiant to that connection. b) When a connection fails and eventually the connection state times out (state transition M1 in Section 6.2.2 State Transition Descriptions for Initiators and Targets) and there are active tasks allegiant to that connection. c) When a successful recovery Logout is performed while there are active tasks allegiant to that connection, and those tasks eventu- ally time out after the Time2Wait and Time2Retain periods without allegiance reassignment. If the tasks terminated in any of the above cases are SCSI tasks, they must be internally terminated with CHECK CONDITION status with a sense key of unit attention and ASC/ASCQ values of 0x6E/0x00 (COM- MAND TO LOGICAL UNIT FAILED). Note that this status is meaningful only for appropriately handling the internal SCSI state with respect to ordering aspects such as queued commands because this status is never communicated back as a terminating status to the initiator. Julian Satran Expires February 2003 188 iSCSI 5-August-02 9.15 Logout Response The logout response is used by the target to indicate if the cleanup operation for the connection(s) has completed. After Logout, the TCP connection referred by the CID MUST be closed at both ends (or all connections must be closed if the logout reason was session close). Byte/ 0 | 1 | 2 | 3 | / | | | | |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7| +---------------+---------------+---------------+---------------+ 0|.|.| 0x26 |1| Reserved | Response | Reserved | +---------------+---------------+---------------+---------------+ 4|TotalAHSLength | DataSegmentLength | +---------------------------------------------------------------+ 8/ Reserved / +/ / +---------------+---------------+---------------+---------------+ 16| Initiator Task Tag | +---------------+---------------+---------------+---------------+ 20| Reserved | +---------------+---------------+---------------+---------------+ 24| StatSN | +---------------+---------------+---------------+---------------+ 28| ExpCmdSN | +---------------+---------------+---------------+---------------+ 32| MaxCmdSN | +---------------+---------------+---------------+---------------+ 36| Reserved | +---------------------------------------------------------------+ 40| Time2Wait | Time2Retain | +---------------+---------------+---------------+---------------+ 44| Reserved | +---------------+---------------+---------------+---------------+ 48| Header-Digest (Optional) | +---------------+---------------+---------------+---------------+ 9.15.1 Response Logout response: 0 - connection or session closed successfully. Julian Satran Expires February 2003 189 iSCSI 5-August-02 1 - CID not found. 2 - connection recovery is not supported (if Logout reason code was recovery and target does not support it - as indicated by the ErrorRecoveryLevel). 3 - cleanup failed for various reasons. 9.15.2 TotalAHSLength and DataSegmentLength For this PDU TotalAHSLength and DataSegmentLength MUST be 0. 9.15.3 Time2Wait If the Logout response code is 0 and if the operational ErrorRecov- eryLevel is 2, this is the minimum amount of time, in seconds, to wait before attempting task reassignment. If the Logout response code is 0 and if the operational ErrorRecoveryLevel is less than 2, this field is to be ignored. This field is invalid if the Logout response code is 1. If the Logout response code is 2 or 3, this field specifies the mini- mum time to wait before attempting a new implicit or explicit logout. If Time2Wait is 0, the reassignment or a new Logout may be attempted immediately. 9.15.4 Time2Retain If the Logout response code is 0 and if the operational ErrorRecov- eryLevel is 2, this is the maximum amount of time, in seconds, after the initial wait (Time2Wait), the target waits for the allegiance reassignment for any active task after which the task state is dis- carded. If the Logout response code is 0 and if the operational ErrorRecoveryLevel is less than 2, this field is to be ignored. This field is invalid if the Logout response code is 1. If the Logout response code is 2 or 3, this field specifies the maxi- mum amount of time, in seconds, after the initial wait (Time2Wait), the target waits for a new implicit or explicit logout. Julian Satran Expires February 2003 190 iSCSI 5-August-02 If it is the last connection of a session, the whole session state is discarded after Time2Retain. If Time2Retain is 0, the target had already discarded the connection (and possibly the session) state along with the task states. No reassignment or Logout is required in this case. Julian Satran Expires February 2003 191 iSCSI 5-August-02 9.16 SNACK Request Byte/ 0 | 1 | 2 | 3 | / | | | | |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7| +---------------+---------------+---------------+---------------+ 0|.|.| 0x10 |1|.|.|.| Type | Reserved | +---------------+---------------+---------------+---------------+ 4|TotalAHSLength | DataSegmentLength | +---------------+---------------+---------------+---------------+ 8| LUN or Reserved | + + 12| | +---------------+---------------+---------------+---------------+ 16| Initiator Task Tag or 0xffffffff | +---------------+---------------+---------------+---------------+ 20| Target Transfer Tag or SNACK Tag or 0xffffffff | +---------------+---------------+---------------+---------------+ 24| Reserved | +---------------+---------------+---------------+---------------+ 28| ExpStatSN | +---------------+---------------+---------------+---------------+ 32/ Reserved / +/ / +---------------+---------------+---------------+---------------+ 40| BegRun | +---------------------------------------------------------------+ 44| RunLength | +---------------------------------------------------------------+ 48| Header-Digest (Optional) | +---------------+---------------+---------------+---------------+ Support for all SNACK types is mandatory if the implementation sup- ports ErrorRecoveryLevel greater than zero. The SNACK request is used to request the retransmission of numbered- responses, data, or R2T PDUs from the target. The SNACK request indi- cates the numbered-responses or data "runs" whose retransmission is requested by the target, where the run starts with the first StatSN, DataSN, or R2TSN whose retransmission is requested and indicates also the number of Status, Data, or R2T PDUs requested including the first. 0 has special meaning when used as a starting number and length: Julian Satran Expires February 2003 192 iSCSI 5-August-02 - when used in RunLength it means all PDUs starting with the initial - when used in both BegRun and RunLength it means all unac- knowledged PDUs The numbered-response(s) or R2T(s), requested by a SNACK, MUST be delivered as exact replicas of the ones the transmitted originally except for the fields ExpCmdSN, MaxCmdSN and ExpDataSN which MUST carry the current values. R2T(s)requested by SNACK MUST carry also the current value of StatSN. The numbered Data-In PDUs, requested by a Data SNACK MUST be deliv- ered as exact replicas of the ones the transmitted originally except the fields ExpCmdSN and MaxCmdSN which MUST carry the current values and except for resegmentation (see Section 9.16.3 Resegmentation). Any SNACK that requests a numbered-response, Data, or R2T that was not sent by the target or was already acknowledged by the initiator MUST be rejected with a reason code of "Protocol error". 9.16.1 Type This field encodes the SNACK function as follows: 0-Data/R2T SNACK - requesting retransmission of one or more Data-In or R2T PDU. 1-Status SNACK - requesting retransmission of one or more num- bered response. 2-DataACK - positively acknowledges Data-In PDUs. 3-R-Data SNACK - requesting retransmission of Data-In PDUs with possible resegmentation and status tagging. All other values are reserved. Data/R2T SNACK, Status SNACK or R-Data SNACK for a command MUST pre- cede status acknowledgement for the given command. 9.16.2 Data Acknowledgement If an initiator operates at ErrorRecoveryLevel 1 or higher, it MUST issue a SNACK of type DataACK after receiving a Data-In PDU with the Julian Satran Expires February 2003 193 iSCSI 5-August-02 A bit set to 1. However, if the initiator has detected holes in the input sequence, it MUST postpone issuing the SNACK of type DataACK until the holes are filled. An initiator MAY ignore the A bit if it deems that the bit is being set aggressively by the target (i.e., before the MaxBurstLength limit is reached). The DataACK is used to free resources at the target and not to request or imply data retransmission. An initiator MUST NOT request retransmission for any data it had already acknowledged. 9.16.3 Resegmentation If the initiator MaxRecvDataSegmentLength changed between the origi- nal transmission and the time the initiator requests retransmission the initiator MUST issue a R-Data SNACK (see Section 9.16.1 Type). With R-Data SNACK the initiator indicates that it discards all the unacknowledged data and expects the target to resend it and it expects also resegmentation. In this case the retransmitted Data-In PDUs MAY be different from the ones originally sent, in order to reflect changes in MaxRecvDataSegmentLength. Their DataSN starts with the BegRun of the last DataACK received by the target if any was received or 0 otherwise and is increased by 1 for each resent Data-In PDU. A target that has received a R-Data SNACK MUST return a SCSI Response that contains a copy of the R-Data SNACK SNACK Tag in the SCSI Response SNACK Tag field as its last or only Response (i.e., if it has already sent a response containing another value in the SNACK Tag field or had the status included in the last Data-In PDU it must send a new SCSI Response PDU). If a target sends more than one SCSI Response PDU due to this rule all SCSI responses must carry the same StatSN (see also Section 9.4.4 SNACK Tag). If an initiator attempts to recover a lost SCSI Response (with a Status-SNACK - see Section 9.16.1 Type) when more than one response has been sent, the target will send the SCSI Response with the latest content known to the tar- get, including the last SNACK Tag for the command. For considerations in allegiance reassignment of a task to a connec- tion with a different MaxRecvDataSegmentLength, refer Section 5.2.2 Allegiance Reassignment. Julian Satran Expires February 2003 194 iSCSI 5-August-02 9.16.4 Initiator Task Tag For Status SNACK and DataACK, the Initiator Task Tag MUST be set to the reserved value 0xffffffff. In all other cases, the Initiator Task Tag field MUST be set to the Initiator Task Tag of the referenced command. 9.16.5 Target Transfer Tag or SNACK Tag For an R-Data SNACK this field MUST contain a value that is differ- ent from 0 or 0xffffffff and is unique for the task (identified by the Initiator Task Tag). This value MUST be copied by the iSCSI tar- get in the last or only SCSI Response PDU it issues for the command. For DataACK the Target Transfer Tag has to contain a copy of the Tar- get Transfer Tag and LUN provided with the SCSI Data-In PDU with the A bit set to 1. In all other cases, the Target Transfer Tag field MUST be set to the reserved value of 0xffffffff. 9.16.6 BegRun The DataSN, R2TSN, or StatSN of the first PDU whose retransmission is requested (Data/R2T and Status SNACK) or the next expected DataSN (DataACK SNACK). BegRun 0 when used in conjunction with RunLength 0 means resend all unacknowledged Data-In, R2T or Response PDUs. BegRun MUST be 0 for a R-Data SNACK. 9.16.7 RunLength The number of PDUs whose retransmission is requested. RunLength 0 signals that all Data-In, R2T or Response PDUs carrying the numbers equal to or greater than BegRun have to be resent. The RunLength MUST also be 0 for a DataACK SNACK as well as for R- Data SNACK. Julian Satran Expires February 2003 195 iSCSI 5-August-02 9.17 Reject Byte/ 0 | 1 | 2 | 3 | / | | | | |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7| +---------------+---------------+---------------+---------------+ 0|.|.| 0x3f |1| Reserved | Reason | Reserved | +---------------+---------------+---------------+---------------+ 4|TotalAHSLength | DataSegmentLength | +---------------+---------------+---------------+---------------+ 8/ Reserved / +/ / +---------------+---------------+---------------+---------------+ 16| 0xffffffff | +---------------+---------------+---------------+---------------+ 20| Reserved | +---------------+---------------+---------------+---------------+ 24| StatSN | +---------------+---------------+---------------+---------------+ 28| ExpCmdSN | +---------------+---------------+---------------+---------------+ 32| MaxCmdSN | +---------------+---------------+---------------+---------------+ 36| DataSN or Reserved | +---------------+---------------+---------------+---------------+ 40| Reserved | +---------------+---------------+---------------+---------------+ 44| Reserved | +---------------+---------------+---------------+---------------+ 48| Header-Digest (Optional) | +---------------+---------------+---------------+---------------+ xx/ Complete Header of Bad PDU / +/ / +---------------+---------------+---------------+---------------+ yy/Vendor specific data (if any) / / / +---------------+---------------+---------------+---------------+ zz| Data-Digest (Optional) | +---------------+---------------+---------------+---------------+ Reject is used to indicate an iSCSI error condition (protocol, unsup- ported option etc.). Julian Satran Expires February 2003 196 iSCSI 5-August-02 9.17.1 Reason The reject Reason is coded as follows: +------+-----------------------------------------+------------------+ | Code | Explanation | Can the original | | (hex)| | PDU be re-sent? | +------+-----------------------------------------+------------------+ | 0x01 | Reserved | no | | | | | | 0x02 | Data (payload) Digest Error | yes (Note 1) | | | | | | 0x03 | SNACK Reject | yes | | | | | | 0x04 | Protocol Error (e.g., SNACK request for | no | | | a status that was already acknowledged) | | | | | | | 0x05 | Command not supported | no | | | | | | 0x06 | Immediate Command Reject - too many | yes | | | immediate commands | | | | | | | 0x07 | Task in progress | no | | | | | | 0x08 | Invalid Data ACK | no | | | | | | 0x09 | Invalid PDU field | no (Note 2) | | | | | | 0x0a | Long Operation Reject - Can't generate | yes | | | Target Transfer Tag - out of resources | | | | | | | 0x0b | Negotiation Reset | no | | | | | | 0x0c | Waiting for Logout | no | +------+-----------------------------------------+------------------+ Note 1: For iSCSI Data-Out PDU retransmission is done only if the target requests retransmission with a recovery R2T. However, if this is the data digest error on immediate data, the initiator may choose to retransmit the whole PDU including the immediate data. Julian Satran Expires February 2003 197 iSCSI 5-August-02 Note 2: A target should use this reason code for all invalid values of PDU fields that are meant to describe a task, a response or a data transfer. Some examples are invalid TTT/ITT, buffer offset, LUN qualifying a TTT, an invalid sequence number in a SNACK. All other values for Reason are reserved. In all the cases in which a pre-instantiated SCSI task is terminated because of the reject, the target MUST issue a proper SCSI command response with CHECK CONDITION as described in Section 9.4.3 Response. In those cases in which a status for the SCSI task was already sent before the reject no additional status is required. If the error is detected while data from the initiator is still expected (the com- mand PDU did not contain all the data and the target has not received a Data-out PDU with the Final bit 1 for the unsolicited data - if any and all outstanding R2Ts - if any), the target MUST wait until it receives the last expected Data-out PDUs with the F bit set to 1 before sending the Response PDU. For additional usage semantics of Reject PDU, see Section 5.3 Usage Of Reject PDU in Recovery. 9.17.2 DataSN This field is valid only if the Reason code is "Protocol error" and the SNACK was a Data/R2T SNACK. The DataSN/R2TSN is the last valid sequence number that the target sent for the task. 9.17.3 StatSN, ExpCmdSN and MaxCmdSN Those fields carry their usual values and are not related to the rejected command 9.17.4 Complete Header of Bad PDU The target returns the header (not including digest) of the PDU in error as the data of the response. Julian Satran Expires February 2003 198 iSCSI 5-August-02 9.18 NOP-Out Byte/ 0 | 1 | 2 | 3 | / | | | | |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7| +---------------+---------------+---------------+---------------+ 0|.|I| 0x00 |1| Reserved | +---------------+---------------+---------------+---------------+ 4|TotalAHSLength | DataSegmentLength | +---------------+---------------+---------------+---------------+ 8| LUN or Reserved | + + 12| | +---------------+---------------+---------------+---------------+ 16| Initiator Task Tag or 0xffffffff | +---------------+---------------+---------------+---------------+ 20| Target Transfer Tag or 0xffffffff | +---------------+---------------+---------------+---------------+ 24| CmdSN | +---------------+---------------+---------------+---------------+ 28| ExpStatSN | +---------------+---------------+---------------+---------------+ 32/ Reserved / +/ / +---------------+---------------+---------------+---------------+ 48| Header-Digest (Optional) | +---------------+---------------+---------------+---------------+ / DataSegment - Ping Data (optional) / +/ / +---------------+---------------+---------------+---------------+ | Data-Digest (Optional) | +---------------+---------------+---------------+---------------+ A NOP-Out may be used by an initiator as a "ping request" to verify that a connection/session is still active and all its components are operational. The NOP-In response is the "ping echo". A NOP-Out is also sent by an initiator in response to a NOP-In. A NOP-Out may also be used to confirm a changed ExpStatSN if another PDU will not be available for a long time. Julian Satran Expires February 2003 199 iSCSI 5-August-02 When used as a ping request, the Initiator Task Tag MUST be set to a valid value (not the reserved 0xffffffff). Upon receipt of a NOP-In with the Target Transfer Tag set to a valid value (not the reserved 0xffffffff), the initiator MUST respond with a NOP-Out. In this case, the NOP-Out Target Transfer Tag MUST con- tain a copy of the NOP-In Target Transfer Tag. When a target receives the NOP-Out with a valid Initiator Task Tag, it MUST respond with a Nop-In Response (see NOP-In). 9.18.1 Initiator Task Tag An initiator assigned identifier for the operation. The NOP-Out MUST have the Initiator Task Tag set to a valid value only if a response in the form of NOP-In is requested. Otherwise the Initiator Task Tag MUST be set to 0xffffffff. If the Initiator Task Tag contains 0xffffffff the I bit MUST be set to 1 and the CmdSN is not advanced after this PDU is sent. 9.18.2 Target Transfer Tag A target assigned identifier for the operation. The NOP-Out MUST have the Target Transfer Tag set only if it is issued in response to a NOP-In with a valid Target Transfer Tag. In this case, it copies the Target Transfer Tag from the NOP-In PDU. Otherwise the Target Transfer Tag MUST be set to 0xffffffff. When the Target Transfer Tag is set to a value other than 0xffffffff, the LUN field MUST also be copied from the NOP-In. 9.18.3 Ping Data Ping data are reflected in the NOP-In Response. The length of the reflected data are limited to MaxRecvDataSegmentLength. The length of ping data are indicated by the DataSegmentLength. 0 is a valid value for the Data Segment Length and indicates the absence of ping data. Julian Satran Expires February 2003 200 iSCSI 5-August-02 9.19 NOP-In Byte/ 0 | 1 | 2 | 3 | / | | | | |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7| +---------------+---------------+---------------+---------------+ 0|.|.| 0x20 |1| Reserved | +---------------+---------------+---------------+---------------+ 4|TotalAHSLength | DataSegmentLength | +---------------+---------------+---------------+---------------+ 8| LUN or Reserved | + + 12| | +---------------+---------------+---------------+---------------+ 16| Initiator Task Tag or 0xffffffff | +---------------+---------------+---------------+---------------+ 20| Target Transfer Tag or 0xffffffff | +---------------+---------------+---------------+---------------+ 24| StatSN | +---------------+---------------+---------------+---------------+ 28| ExpCmdSN | +---------------+---------------+---------------+---------------+ 32| MaxCmdSN | +---------------+---------------+---------------+---------------+ 36/ Reserved / +/ / +---------------+---------------+---------------+---------------+ 48| Header-Digest (Optional) | +---------------+---------------+---------------+---------------+ / DataSegment - Return Ping Data / +/ / +---------------+---------------+---------------+---------------+ | Data-Digest (Optional) | +---------------+---------------+---------------+---------------+ NOP-In is either sent by a target as a response to a NOP-Out, as a "ping" to an initiator or as a means to carry a changed ExpCmdSN and/ or MaxCmdSN if another PDU will not be available for a long time (as determined by the target). When a target receives the NOP-Out with a valid Initiator Task Tag (not the reserved value 0xffffffff), it MUST respond with a NOP-In Julian Satran Expires February 2003 201 iSCSI 5-August-02 with the same Initiator Task Tag that was provided in the NOP-Out request. It MUST also duplicate up to the first MaxRecvDataSeg- mentLength bytes of the initiator provided Ping Data. For such a response, the Target Transfer Tag MUST be 0xffffffff. Otherwise, when a target sends a NOP-In that is not a response to a Nop-Out received from the initiator, the Initiator Task Tag MUST be set to 0xffffffff and the Data Segment MUST NOT contain any data (DataSegmentLength MUST be 0). 9.19.1 Target Transfer Tag A target assigned identifier for the operation. If the target is responding to a NOP-Out, this is set to the reserved value 0xffffffff. If the target is sending a NOP-In as a Ping (intending to receive a corresponding NOP-Out), this field is set to a valid value (not the reserved 0xffffffff). If the target is initiating a NOP-In without wanting to receive a corresponding NOP-Out, this field MUST hold the reserved value of 0xffffffff. 9.19.2 StatSN The StatSN field will contain always the next StatSN. However, when the Initiator Task Tag is set to 0xffffffff StatSN for the connec- tion is not advanced after this PDU is sent. 9.19.3 LUN A LUN MUST be set to a correct value when the Target Transfer Tag is valid (not the reserved value 0xffffffff). Julian Satran Expires February 2003 202 iSCSI 5-August-02 10. iSCSI Security Keys and Authentication Methods Only the following keys are used during the SecurityNegotiation stage of the Login Phase: SessionType InitiatorName TargetName TargetAddress InitiatorAlias TargetAlias TargetPortalGroupTag AuthMethod and the keys used by the authentication methods specified under Section 10.1 AuthMethod along with all of their associated keys as well as Vendor Specific Authentica- tion Methods. All other keys MUST NOT be used. SessionType, InitiatorName, TargetName, InitiatorAlias, TargetAlias and TargetPortalGroupTag are described in Chapter 11 as they can be used also in the OperationalNegotiation stage. All security keys have connection-wide applicability. 10.1 AuthMethod Use: During Login - Security Negotiation Senders: Initiator and Target Scope: connection AuthMethod = <list-of-values> The main item of security negotiation is the authentication method (AuthMethod). The authentication methods that can be used (appear in the list-of- values) are either those listed in the following table or are vendor- unique methods: Julian Satran Expires February 2003 203 iSCSI 5-August-02 +------------------------------------------------------------+ | Name | Description | +------------------------------------------------------------+ | KRB5 | Kerberos V5 - defined in [RFC1510] | +------------------------------------------------------------+ | SPKM1 | Simple Public-Key GSS-API Mechanism | | | defined in [RFC2025] | +------------------------------------------------------------+ | SPKM2 | Simple Public-Key GSS-API Mechanism | | | defined in [RFC2025] | +------------------------------------------------------------+ | SRP | Secure Remote Password | | | defined in [RFC2945] | +------------------------------------------------------------+ | CHAP | Challenge Handshake Authentication Protocol| | | defined in [RFC1944] | +------------------------------------------------------------+ | None | No authentication | +------------------------------------------------------------+ The AuthMethod selection is followed by an "authentication exchange" specific to the authentication method selected. The authentication method proposal may be made by either the initia- tor or the target. However the initiator MUST make the first step specific to the selected authentication method as soon as it is selected. It follows that if the target makes the authentication method proposal the initiator sends the first keys(s) of the exchange together with its authentication method selection. The authentication exchange authenticates the initiator to the tar- get, and optionally, the target to the initiator. Authentication is not mandatory to use but MUST be supported by the target and initia- tor. The initiator and target MUST implement CHAP. All other authentica- tion methods are OPTIONAL to implement. Private or public extension algorithms MAY also be negotiated for authentication methods. Whenever a private or public extension algo- rithm is offered, "None" or "CHAP" MUST be listed as an option in order to guarantee interoperability. Julian Satran Expires February 2003 204 iSCSI 5-August-02 Extension authentication methods MUST be named using of the follow- ing two formats: a) Z-reversed.vendor.dns_name.do_something= b) Z<#><IANA-registered-string>= Authentication methods named using the Z- format a are used as pri- vate extensions. Authentication methods named using the Z# format are used as public extensions must be registered with IANA and MUST be described by an informational RFC. For all the public or private extension authentication methods the method specific keys MUST conform to the format specified in Section 4.1 Text Format for standard-label. For private extension authentication methods, to identify the ven- dor, we suggest you use the reversed DNS-name as a prefix to the proper digest names. The part of digest-name following Z- and Z# MUST conform to the for- mat for standard-label specified in Section 4.1 Text Format. Support for public or private extension authentication methods is OPTIONAL. The following subsections define the specific exchanges for each of the standardized authentication methods. As mentioned earlier the first step is always done by the initiator. 10.1.1 Kerberos For KRB5 (Kerberos V5) [RFC1510], the initiator MUST use: KRB_AP_REQ=<KRB_AP_REQ> where KRB_AP_REQ is the client message as defined in [RFC1510]. If the initiator authentication fails, the target MUST respond with a Login reject with "Authentication Failure" status. Otherwise, if the initiator has selected the mutual authentication option (by setting MUTUAL-REQUIRED in the ap-options field of the KRB_AP_REQ), the tar- get MUST reply with: Julian Satran Expires February 2003 205 iSCSI 5-August-02 KRB_AP_REP=<KRB_AP_REP> where KRB_AP_REP is the server's response message as defined in [RFC1510]. If mutual authentication was selected and target authentication fails, the initiator MUST close the connection. KRB_AP_REQ and KRB_AP_REP are binary-values and their binary length (not the length of the character string that represents them in encoded form) MUST not exceed 65536 bytes. 10.1.2 Simple Public-Key Mechanism (SPKM) For SPKM1 and SPKM2 [RFC2025], the initiator MUST use: SPKM_REQ=<SPKM-REQ> where SPKM-REQ is the first initiator token as defined in [RFC2025]. [RFC2025] defines situations where each side may send an error token that may cause the peer to re-generate and resend its last token. This scheme is followed in iSCSI, and the error token syntax is: SPKM_ERROR=<SPKM-ERROR> However, SPKM-DEL tokens that are defined by [RFC2025] for fatal errors will not be used by iSCSI. If the target needs to send a SPKM- DEL token, it will, instead, send a Login "login reject" message with the "Authentication Failure" status and terminate the connection. If the initiator needs to send a SPKM-DEL token, it will close the con- nection. In the following sections, we assume that no SPKM-ERROR tokens are required. If the initiator authentication fails, the target MUST return an error. Otherwise, if the AuthMethod is SPKM1 or if the initiator has selected the mutual authentication option (by setting mutual-state bit in the options field of the REQ-TOKEN in the SPKM-REQ), the tar- get MUST reply with: Julian Satran Expires February 2003 206 iSCSI 5-August-02 SPKM_REP_TI=<SPKM-REP-TI> where SPKM-REP-TI is the target token as defined in [RFC2025]. If mutual authentication was selected and target authentication fails, the initiator MUST close the connection. Otherwise, if the AuthMethod is SPKM1, the initiator MUST continue with: SPKM_REP_IT=<SPKM-REP-IT> where SPKM-REP-IT is the second initiator token as defined in [RFC2025]. If the initiator authentication fails, the target MUST answer with a Login reject with "Authentication Failure" status. SPKM requires support for very long authentication items. All the SPKM-* tokens are binary-values and their binary length (not the length of the character string that represents them in encoded form) MUST not exceed 65536 bytes. 10.1.3 Secure Remote Password (SRP) For SRP [RFC2945], the initiator MUST use: SRP_U=<user> TargetAuth=Yes /* or TargetAuth=No */ The target MUST answer with a Login reject with the "Authorization Failure" status or reply with: SRP_GROUP=<G1,G2...> SRP_s=<s> Where G1,G2... are proposed groups, in order of preference. The initiator MUST either close the connection or continue with: SRP_A=<A> SRP_GROUP=<G> Where G is one of G1,G2... that were proposed by the target. The target MUST answer with a Login reject with the "Authentication Failure" status or reply with: Julian Satran Expires February 2003 207 iSCSI 5-August-02 SRP_B=<B> The initiator MUST close the connection or continue with: SRP_M=<M> If the initiator authentication fails, the target MUST answer with a Login reject with "Authentication Failure" status. Otherwise, if the initiator sent TargetAuth=Yes in the first message (requiring target authentication), the target MUST reply with: SRP_HM=<H(A | M | K)> If the target authentication fails, the initiator MUST close the con- nection. Where U, s, A, B, M, and H(A | M | K) are defined in [RFC2945] (using the SHA1 hash function, i.e., SRP-SHA1) and G,Gn (Gn stands for G1,G2...) are identifiers of SRP groups specified in [SEC-IPS]. G,Gn and U are text strings, s,A,B,M, and H(A | M | K) are binary-values. The length of s,A,B,M and H(A | M | K) in binary form (not the length of the character string that represents them in encoded form) MUST not exceed 1024 bytes. For the SRP_GROUP, all the groups specified in [SEC-IPS] up to 1536 bits (i.e., SRP-768, SRP-1024, SRP-1280, SRP-1536) must be supported by initiators and targets. To guarantee interoperability, targets MUST always offer "SRP-1536" as one of the proposed groups. 10.1.4 Challenge Handshake Authentication Protocol (CHAP) For CHAP [RFC1994], the initiator MUST use: CHAP_A=<A1,A2...> Where A1,A2... are proposed algorithms, in order of preference. The target MUST answer with a Login reject with the "Authentication Failure" status or reply with: CHAP_A=<A> CHAP_I=<I> CHAP_C=<C> Julian Satran Expires February 2003 208 iSCSI 5-August-02 Where A is one of A1,A2... that were proposed by the initiator. The initiator MUST continue with: CHAP_N=<N> CHAP_R=<R> or, if it requires target authentication, with: CHAP_N=<N> CHAP_R=<R> CHAP_I=<I> CHAP_C=<C> If the initiator authentication fails, the target MUST answer with a Login reject with "Authentication Failure" status. Otherwise, if the initiator required target authentication, the target MUST reply with CHAP_N=<N> CHAP_R=<R> If target authentication fails, the initiator MUST close the connec- tion. Where N, (A,A1,A2), I, C, and R are (correspondingly) the Name, Algo- rithm, Identifier, Challenge, and Response as defined in [RFC1994], N is a text string, A,A1,A2, and I are numbers, and C and R are binary- values and their binary length (not the length of the character string that represents them in encoded form) MUST not exceed 1024 bytes. For the Algorithm, as stated in [RFC1994], one value is required to be implemented: 5 (CHAP with MD5) To guarantee interoperability, initiators MUST always offer it as one of the proposed algorithms. Julian Satran Expires February 2003 209 iSCSI 5-August-02 11. Login/Text Operational Keys Some session specific parameters MUST only be carried on the leading connection and cannot be changed after the leading connection login (e.g., MaxConnections, the maximum number of connections). This holds for a single connection session with regard to connection restart. The keys that fall into this category have the use LO (Leading Only). Keys that can be used only during login have the use IO (initialize only) while those that can be used in both the Login Phase and Full Feature Phase have the use ALL. Keys that can only be used during Full Feature Phase use FFPO (Full Feature Phase only). Keys marked as Any-Stage may appear also in the SecurityNegotiation stage while all other keys described in this chapter are operational keys. Keys that do not require an answer are marked as Declarative Key scope is indicated as session-wide (SW) or connection-only (CO). Result function, wherever mentioned, states the function that can be applied to check the validity of the responder selection. Minimum means that the selected value cannot exceed the offered value. Maxi- mum means that the selected value cannot be lower than the offered value. AND means that the selected value must be a possible result of a Boolean "and" function with an arbitrary Boolean value (e.g., if the offered value is No the selected value must be No). OR means that the selected value must be a possible result of a Boolean "or" func- tion with an arbitrary Boolean value (e.g., if the offered value is Yes the selected value must be Yes). 11.1 HeaderDigest and DataDigest Use: IO Senders: Initiator and Target Scope: CO HeaderDigest = <list-of-values> DataDigest = <list-of-values> Julian Satran Expires February 2003 210 iSCSI 5-August-02 Default is None for both HeaderDigest and DataDigest. Digests enable the checking of end-to-end non-cryptographic data integrity beyond the integrity checks provided by the link layers and the covering of the whole communication path including all elements that may change the network level PDUs such as routers, switches, and proxies. The following table lists cyclic integrity checksums that can be negotiated for the digests and that MUST be implemented by every iSCSI initiator and target. These digest options only have error detection significance. +---------------------------------------------+ | Name | Description | Generator | +---------------------------------------------+ | CRC32C | 32 bit CRC |0x11edc6f41| +---------------------------------------------+ | None | no digest | +---------------------------------------------+ The generator polynomial for this digest is given in hex-nota- tion(e.g., 0x3b stands for 0011 1011 and the polynomial is x**5+X**4+x**3+x+1). When the Initiator and Target agree on a digest, this digest MUST be used for every PDU in Full Feature Phase. Padding bytes, when present, in a segment covered by a CRC, SHOULD be set to 0 and are included in the CRC. The CRC MUST be calculated by a method that produces the same results as the following process: - The PDU bits are considered as the coefficients of a polyno- mial M(x) of degree n-1; bit 7 of the lowest numbered byte is considered the most significant bit (x^n-1), followed by bit 6 of the lowest numbered byte and through bit 0 of the high- est numbered byte (x^0). - The most significant 32 bits are complemented. - The polynomial is multiplied by x^32 then divided by G(x). The generator polynomial produces a remainder R(x) of degree <= 31. Julian Satran Expires February 2003 211 iSCSI 5-August-02 - The coefficients of R(x) are considered a 32 bit sequence. - The bit sequence is complemented and the result is the CRC. - the CRC bits are mapped into the digest word - the x^31 coef- ficient in bit 7 of the lowest numbered byte of the digest continuing to through the byte up to the x^24 coefficient in bit 0 of the lowest numbered byte, continuing with the x^23 coefficient in bit 7 of next byte through x^0 in bit 0 of the highest numbered byte. - Computing the CRC over any segment (data or header) extended to include the CRC built using the generator 0x11edc6f41 will get always the value 0x1c2d19ed as its final remainder (R(x)). This value is given here in its polynomial form - i.e. not mapped as the digest word For a discussion about selection criteria for the CRC see [iSCSI- CRC]. For a detailed analysis of the iSCSI polynomial see [Castagnoli93]. Private or public extension algorithms MAY also be negotiated for digests. Whenever a private or public extension algorithm is offered, "None" or "CRC32C" MUST be listed as an option in order to guarantee interoperability. Extension digest algorithms MUST be named using of the following two formats: a) Y-reversed.vendor.dns_name.do_something= b) Y<#><IANA-registered-string>= Digests named using the Y- format are used for private purposes (unregistered). Digests named using the Y# format (public extension) must be registered with IANA and MUST be described by an informa- tional RFC. For private extension digests, to identify the vendor, we suggest you use the reversed DNS-name as a prefix to the proper digest names. The part of digest-name following Y- and Y# MUST conform to the for- mat for standard-label specified in Section 4.1 Text Format. Support for public or private extension digests is OPTIONAL. Julian Satran Expires February 2003 212 iSCSI 5-August-02 11.2 MaxConnections Use: LO Senders: Initiator and Target Scope: SW Irrelevant when: SessionType=Discovery MaxConnections=<numerical-value-from-1-to-65535> Default is 1. Result function is Minimum. Initiator and target negotiate the maximum number of connections requested/acceptable. 11.3 SendTargets Use: FFPO Senders: Initiator Scope: SW For a complete description, see Appendix D. - SendTargets Operation. 11.4 TargetName Use: IO by initiator, FFPO by target - only as response to a Sendtar- gets, Declarative, Any-Stage Senders: Initiator and Target Scope: SW TargetName=<iSCSI-name-value> Examples: TargetName=iqn.1993-11.com.disk-vendor.diskarrays.sn.45678 TargetName=eui.020000023B040506 The initiator of the TCP connection MUST provide this key to the remote endpoint in the first login request if the initiator is not establishing a discovery session. The iSCSI Target Name specifies the worldwide unique name of the target. The TargetName key may also be returned by the "SendTargets" text request (which is its only use when issued by a target). Julian Satran Expires February 2003 213 iSCSI 5-August-02 TargetName MUST not be redeclared within the login phase. 11.5 InitiatorName Use: IO, Declarative, Any-Stage Senders: Initiator Scope: SW InitiatorName=<iSCSI-name-value> Examples: InitiatorName=iqn.1992-04.com.os-vendor.plan9.cdrom.12345 InitiatorName=iqn.2001-02.com.ssp.users.customer235.host90 The initiator of the TCP connection MUST provide this key to the remote endpoint at the first Login of the Login Phase for every con- nection. The Initiator key enables the initiator to identify itself to the remote endpoint. InitiatorName MUST not be redeclared within the login phase. 11.6 TargetAlias Use: ALL, Declarative, Any-Stage Senders: Target Scope: SW TargetAlias=<iSCSI-local-name-value> Examples: TargetAlias=Bob-s Disk TargetAlias=Database Server 1 Log Disk TargetAlias=Web Server 3 Disk 20 If a target has been configured with a human-readable name or description, this name SHOULD be communicated to the initiator dur- ing a Login Response PDU if SessionType=Normal (see Section 11.21 SessionType). This string is not used as an identifier, nor is meant to be used for authentication or authorization decisions. It can be displayed by the initiator's user interface in a list of targets to which it is connected. Julian Satran Expires February 2003 214 iSCSI 5-August-02 11.7 InitiatorAlias Use: ALL, Declarative, Any-Stage Senders: Initiator Scope: SW InitiatorAlias=<iSCSI-local-name-value> Examples: InitiatorAlias=Web Server 4 InitiatorAlias=spyalley.nsa.gov InitiatorAlias=Exchange Server If an initiator has been configured with a human-readable name or description, it SHOULD be communicated to the target during a Login Request PDU. If not, the host name can be used instead. This string is not used as an identifier, nor is meant to be used for authentica- tion or authorization decisions. It can be displayed by the target's user interface in a list of initiators to which it is connected. 11.8 TargetAddress Use: ALL, Declarative, Any-Stage Senders: Target Scope: SW TargetAddress=domainname[:port][,portal-group-tag] The domainname can be specified as either a DNS host name, a dotted- decimal IPv4 address, or a bracketed IPv6 address as specified in [RFC2732]. If the TCP port is not specified, it is assumed to be the IANA- assigned default port for iSCSI (see Section 12 IANA Considerations). If the TargetAddress is returned as the result of a redirect status in a login response, the comma and portal group tag MUST be omitted. If the TargetAddress is returned within a SendTargets response, the portal group tag MUST be included. Examples: Julian Satran Expires February 2003 215 iSCSI 5-August-02 TargetAddress=10.0.0.1:5003,1 TargetAddress=[1080:0:0:0:8:800:200C:417A],65 TargetAddress=[1080::8:800:200C:417A]:5003,1 TargetAddress=computingcenter.acme.com,23 Use of the portal-group-tag is described in Appendix D. - SendTar- gets Operation. The formats for the port and portal-group-tag are the same as the one specified in Section 11.9 TargetPortalGroupTag. 11.9 TargetPortalGroupTag Use: IO by target, Declarative, Any-Stage Senders: Target Scope: SW TargetPortalGroupTag=<16-bit-binary-value> Examples: TargetPortalGroupTag=1 Target portal group tag is a 16-bit binary-value that uniquely iden- tifies a portal group within an iSCSI target node. This key carries the value of the tag of the portal group that is servicing the Login request. The iSCSI target returns this key to the initiator in the Login Response PDU to the first Login Request PDU that has the C bit set to 0. For the complete usage expectations of this key see Section 4.3 Login Phase. 11.10 InitialR2T Use: LO Senders: Initiator and Target Scope: SW Irrelevant when: SessionType=Discovery InitialR2T=<boolean-value> Examples: I->InitialR2T=No Julian Satran Expires February 2003 216 iSCSI 5-August-02 T->InitialR2T=No Default is Yes. Result function is OR. The InitialR2T key is used to turn off the default use of R2T for unidirectional and the output part of bidirectional commands, thus allowing an initiator to start sending data to a target as if it has received an initial R2T with Buffer Offset=Immediate Data Length and Desired Data Transfer Length=(min(FirstBurstLength, Expected DataTransfer Length) - Received Immediate Data Length). The default action is that R2T is required, unless both the initia- tor and the target send this key-pair attribute specifying InitialR2T=No. Only the first outgoing data burst (immediate data and/or separate PDUs) can be sent unsolicited (i.e., not requiring an explicit R2T). 11.11 ImmediateData Use: LO Senders: Initiator and Target Scope: SW Irrelevant when: SessionType=Discovery ImmediateData=<boolean-value> Default is Yes. Result function is AND. The initiator and target negotiate support for immediate data. To turn immediate data off, the initiator or target must state its desire to do so. ImmediateData can be turned on if both the initia- tor and target have ImmediateData=Yes. If ImmediateData is set to Yes and InitialR2T is set to Yes (default), then only immediate data are accepted in the first burst. If ImmediateData is set to No and InitialR2T is set to Yes, then the initiator MUST NOT send unsolicited data and the target MUST reject unsolicited data with the corresponding response code. Julian Satran Expires February 2003 217 iSCSI 5-August-02 If ImmediateData is set to No and InitialR2T is set to No, then the initiator MUST NOT send unsolicited immediate data, but MAY send one unsolicited burst of Data-OUT PDUs. If ImmediateData is set to Yes and InitialR2T is set to No, then the initiator MAY send unsolicited immediate data and/or one unsolicited burst of Data-OUT PDUs. The following table is a summary of unsolicited data options: +----------+-------------+------------------+--------------+ |InitialR2T|ImmediateData| Unsolicited |Immediate Data| | | | Data Out PDUs | | +----------+-------------+------------------+--------------+ | No | No | Yes | No | +----------+-------------+------------------+--------------+ | No | Yes | Yes | Yes | +----------+-------------+------------------+--------------+ | Yes | No | No | No | +----------+-------------+------------------+--------------+ | Yes | Yes | No | Yes | +----------+-------------+------------------+--------------+ 11.12 MaxRecvDataSegmentLength Use: ALL, Declarative Senders: Initiator and Target Scope: CO MaxRecvDataSegmentLength=<numerical-value-512-to-(2**24-1)> Default is 8192 bytes. The initiator or target declares the maximum data segment length in bytes it can receive in an iSCSI PDU. The transmitter (initiator or target) is required to send PDUs with a data segment not exceeding MaxRecvDataSegmentLength of the receiver. A target receiver is additionally limited by MaxBurstLength for solicited data and FirstBurstLength for unsolicited data and an ini- tiator MUST NOT send solicited PDUs exceeding MaxBurstLength nor Julian Satran Expires February 2003 218 iSCSI 5-August-02 unsolicited PDUs exceeding FirstBurstLength (or FirstBurstLength- Immediate Data Length if immediate data where sent). 11.13 MaxBurstLength Use: LO Senders: Initiator and Target Scope: SW Irrelevant when: SessionType=Discovery MaxBurstLength=<numerical-value-512-to-(2**24-1)> Default is 262144 (256 Kbytes). Result function is Minimum. The initiator and target negotiate maximum SCSI data payload in bytes in a Data-In or a solicited Data-Out iSCSI sequence. A sequence con- sists of one or more consecutive Data-In or Data-Out PDUs ending with a Data-In or Data-Out PDU with the F bit set to one. 11.14 FirstBurstLength Use: LO Senders: Initiator and Target Scope: SW Irrelevant when: SessionType=Discovery Irrelevant when: ( InitialR2T=Yes and ImmediateData=No ) FirstBurstLength=<numerical-value-512-to-(2**24-1)> Default is 65536 (64 Kbytes). Result function is Minimum. The initiator and target negotiate the maximum amount in bytes of unsolicited data an iSCSI initiator may send to the target during the execution of a single SCSI command. This covers the immediate data (if any) and the sequence of unsolicited Data-Out PDUs (if any) that follow the command. FirstBurstLength MUST NOT exceed MaxBurstLength. 11.15 DefaultTime2Wait Use: LO Julian Satran Expires February 2003 219 iSCSI 5-August-02 Senders: Initiator and Target Scope: SW DefaultTime2Wait=<numerical-value-0-to-3600> Default is 2. Result function is Maximum. The initiator and target negotiate the minimum time, in seconds, to wait before attempting an explicit/implicit logout or an active task reassignment after an unexpected connection termination or a connec- tion reset. A value of 0 indicates that logout or active task reassignment can be attempted immediately. 11.16 DefaultTime2Retain Use: LO Senders: Initiator and Target Scope: SW DefaultTime2Retain=<numerical-value-0-to-3600> Default is 20. Result function is Minimum. The initiator and target negotiate the maximum time, in seconds after an initial wait (Time2Wait), before which an active task reassign- ment is still possible after an unexpected connection termination or a connection reset. This value is also the session state timeout if the connection in question is the last LOGGED_IN connection in the session. A value of 0 indicates that connection/task state is immediately dis- carded by the target. 11.17 MaxOutstandingR2T Use: LO Senders: Initiator and Target Scope: SW Julian Satran Expires February 2003 220 iSCSI 5-August-02 MaxOutstandingR2T=<numerical-value-from-1-to-65535> Irrelevant when: SessionType=Discovery Default is 1. Result function is Minimum. Initiator and target negotiate the maximum number of outstanding R2Ts per task, excluding any implied initial R2T that might be part of that task. An R2T is considered outstanding until the last data PDU (with the F bit set to 1) is transferred, or a sequence reception timeout (section 5.14.1) is encountered for that data sequence. 11.18 DataPDUInOrder Use: LO Senders: Initiator and Target Scope: SW Irrelevant when: SessionType=Discovery DataPDUInOrder=<boolean-value> Default is Yes. Result function is OR. No is used by iSCSI to indicate that the data PDUs within sequences can be in any order. Yes is used to indicate that data PDUs within sequences have to be at continuously increasing addresses and over- lays are forbidden. 11.19 DataSequenceInOrder Use: LO Senders: Initiator and Target Scope: SW Irrelevant when: SessionType=Discovery DataSequenceInOrder=<boolean-value> Default is Yes. Result function is OR. A Data Sequence is a sequence of Data-In or Data-Out PDUs ending with a Data-In or Data-Out PDU with the F bit set to one. A Data-out Julian Satran Expires February 2003 221 iSCSI 5-August-02 sequence is sent either unsolicited or in response to an R2T. Sequences cover an offset-range. If DataSequenceInOrder is set to No, Data PDU sequences may be trans- ferred in any order. If DataSequenceInOrder is set to Yes, Data Sequences MUST be trans- ferred using continuously non-decreasing sequence offsets (R2T buffer offset for writes, or the smallest SCSI Data-In buffer offset within a read data sequence). If DataSequenceInOrder is set to Yes, a target may retry at most the last R2T, and an initiator may at most request retransmission for the last read data sequence. For this reason if ErrorRecoveryLevel is not 0 and DataSequenceInOrder is set to Yes then MaxOustandingR2T MUST be set to 1. 11.20 ErrorRecoveryLevel Use: LO Senders: Initiator and Target Scope: SW ErrorRecoveryLevel=<numerical-value-0-to-2> Default is 0. Result function is Minimum. The initiator and target negotiate the recovery level supported. Recovery levels represent a combination of recovery capabilities. Each recovery level includes all the capabilities of the lower recov- ery levels and adds some new ones to them. In the description of recovery mechanisms, certain recovery classes are specified. Section 5.15 Error Recovery Hierarchy describes the mapping between the classes and the levels. 11.21 SessionType Use: LO, Declarative, Any-Stage Senders: Initiator Scope: SW Julian Satran Expires February 2003 222 iSCSI 5-August-02 SessionType= <Discovery|Normal> Default is Normal. The Initiator indicates the type of session it wants to create. The target can either accept it or reject it. A discovery session indicates to the Target that the only purpose of this Session is discovery. The only requests a target accepts in this type of session are a text request with a SendTargets key and a logout request with reason "close the session". The discovery session implies MaxConnections = 1 and overrides both the default and an explicit setting. 11.22 The Private or Public Extension Key Format Use: ALL Senders: Initiator and Target Scope: specific key dependent X-reversed.vendor.dns_name.do_something= or X<#><IANA-registered-string>= Keys with this format are used for public or private extension pur- poses. These keys always start with X- if unregistered with IANA (private) or X# if registered with IANA (public). For unregistered keys, to identify the vendor, we suggest you use the reversed DNS-name as a prefix to the key-proper. The part of key-name following X- and X# MUST conform to the format for key-name specified in Section 4.1 Text Format. For IANA registered keys the string following X# must be registered with IANA and the use of the key MUST be described by an informa- tional RFC. Vendor specific keys MUST ONLY be used in normal sessions. Julian Satran Expires February 2003 223 iSCSI 5-August-02 Support for public or private extension keys is OPTIONAL. Julian Satran Expires February 2003 224 iSCSI 5-August-02 12. IANA Considerations The well-known TCP port number for iSCSI connections assigned by IANA is 3260. A system port must be assigned by IANA when this draft is approved to become a RFC. Additional keys, authentication methods or digest types for which a vendor or group of vendor intend to provide publicly available descriptions MUST be described by an RFC and MUST be registered with IANA. IANA must maintain 3 registries: a) an iSCSI extended key registry b) an iSCSI authentication methods registry c) an iSCSI digests registry [SEC-IPS] also instructs IANA to maintain a registry for the values of the SRP_GROUP key. The format of those values must conform to the one specified for standard-label in Section 4.1 Text Format. For the iSCSI authentication methods registry and the iSCSI digests registry IANA MUST also assign a 16 bit unsigned integer number (the method number for the authentication method and the digest number for the digest). The registry for authentication methods will also contain all authen- tication methods specified in this document as follows: Authentication Method | Number | +----------------------------------------+--------+ | CHAP | 1 | +----------------------------------------+--------+ | SRP | 2 | +----------------------------------------+--------+ | KRB5 | 3 | +----------------------------------------+--------+ | SPKM1 | 4 | +----------------------------------------+--------+ | SPKM2 | 5 | +----------------------------------------+--------+ Julian Satran Expires February 2003 225 iSCSI 5-August-02 All other record numbers from 0 to 255 are reserved (IANA will regis- ter numbers above 256. Authentication methods with numbers above 256 MUST be unique within the registry and MUST be used with the prefix Y#. The registry for digest will also contain the digest specified in this document as follows: Digest | Number | +----------------------------------------+--------+ | CRC32C | 1 | +----------------------------------------+--------+ All other record numbers from 0 to 255 are reserved (IANA will regis- ter numbers above 256. Digests with numbers above 256 MUST be unique within the registry and MUST be used with the prefix Z#. The RFC describing the item to be registered MUST indicate in the IANA consideration section the string and iSCSI registry it should be recorded to. New Keys, Authentication Methods and digests (KADs) must conform to a number of requirements as described below. 12.1 Naming Requirements Each KAD must have a unique name in its category. This name will be used as a standard-label for the key, access method or digest and must conform to the syntax specified in Section 4.1 Text Format for standard-labels. 12.2 Mechanism Specification Requirements For KADs all of the protocols and procedures used by a given KAD must be described, either in the specification of the KAD itself or in some other publicly available specification, in sufficient detail for the KAD to be implemented by any competent implementor. Use of secret and/or proprietary methods in KADs are expressly prohibited. The restrictions imposed by RFC 1602 on the standardization of pat- ented algorithms must be respected as well. Julian Satran Expires February 2003 226 iSCSI 5-August-02 12.3 Publication Requirements All KADs must be described by an RFC. The RFC may be informational rather than standards-track, although standard-track review and approval are encouraged for all KADs. 12.4 Security Requirements Any known security issues that arise from the use of the KAD must be completely and fully described. It is not required that the KAD be secure or that it be free from risks, but that the known risks be identified. Publication of a new KAD does not require an exhaustive security review, and the security considerations section is subject to continuing evaluation. Additional security considerations should be addressed by publishing revised versions of the KAD specification. For each of those registries IANA must record the registered string. - which MUST conform to the format rules described in Section 4.1 Text Format for standard-labels and the RFC number that describes it. The key prefix (X#, Y# or Z#) is not part of the recorded string. 12.5 Registration Procedure Registration of a new KAD starts with the construction of a draft of an RFC. 12.5.1 Present the KAD to the Community Send a proposed access type specification to the IPS WG mailing list or if the IPS WG is disbanded at the registration time to the TSWG mailing list for a review period of a month. The intent of the pub- lic posting is to solicit comments and feedback on the KAD specifica- tion and a review of any security considerations. 12.5.2 KAD review and IESG approval When the one month period has passed, the IPS WG chair or a person nominated by the IETF Transport Area Director (the KAD reviewer) either forwards the draft to the IESG for publication as an informa- tional RFC or rejects it. If the specification is a standards track draft the usual IETF procedures for such documents are followed. Julian Satran Expires February 2003 227 iSCSI 5-August-02 Decisions made by the KAD reviewer must be published within 2 weeks after the month-long review period. Decision made by the KAD reviewer can be appealed through the IESG appeal process. 12.5.3 IANA Registration Provided that the KAD has either passed review or has been success- fully appealed to the IESG, and the specification is published as an RFC then IANA will register the KAD make the registration available to the community. 12.5.4 Location of Registered KAD List KAD registrations will be posted in the anonymous FTP directory "ftp://ftp.isi.edu/in-notes/iana/assignments/ips/kads" and all regis- tered KADS will be listed in the periodically issued "Assigned Num- bers" RFC [currently RFC-1700]. 12.6 IANA Procedures for Registering KADs The identity of the KAD reviewer is communicated to the IANA by the IESG. The IANA then only acts in response to KAD definitions that either are approved by the KAD reviewer and forwarded by the reviewer to the IANA for registration, or in response to a communication from the IESG that a KAD definition appeal has overturned the KAD reviewer's ruling. Julian Satran Expires February 2003 228 iSCSI 5-August-02 References and Bibliography Normative References [AESCBC] Frankel, S., Kelly, S., Glenn, R., "The AES Cipher Algorithm and Its Use with IPsec", draft-ietf-ipsec-ciph-aes- cbc-03.txt, November 2001 (Work In Progress). [AESCTR] draft-ietf-ipsec-ciph-aes-ctr-00.txt R. Housley 23- Jul-02 (Work In Progress). [CAM] ANSI X3.232-199X, Common Access Method-3. [EUI] "Guidelines for 64-bit Global Identifier (EUI-64)", http://standards.ieee.org/regauth/oui/tutorials/EUI64.html [OUI] "IEEE OUI and Company_Id Assignments", http://stan- dards.ieee.org/regauth/oui/index.shtml [RFC790] J. Postel, ASSIGNED NUMBERS, September 1981. [RFC791] INTERNET PROTOCOL, DARPA INTERNET PROGRAM PROTOCOL SPECIFICATION, September 1981. [RFC793] TRANSMISSION CONTROL PROTOCOL, DARPA INTERNET PROGRAM PROTOCOL SPECIFICATION, September 1981. [RFC1035] P. Mockapetris, DOMAIN NAMES - IMPLEMENTATION AND SPECIFICATION, November 1987. [RFC1122] Requirements for Internet Hosts-Communication Layer RFC1122, R. Braden (editor). [RFC1510] J. Kohl, C. Neuman, "The Kerberos Network Authentica- tion Service (V5)", September 1993. [RFC1737] K. Sollins, L. Masinter "Functional Requirements for Uniform Resource Names". [RFC1766] H. Alvestrand, "Tags for the Identification of Lan- guages", March 1995. [RFC1964] J. Linn, "The Kerberos Version 5 GSS-API Mechanism", June 1996. [RFC1982] Elz, R., Bush, R., "Serial Number Arithmetic", RFC 1982, August 1996. [RFC1994] "W. Simpson, PPP Challenge Handshake Authentication Protocol (CHAP)", RFC 1994, August 1996. [RFC2025] C. Adams, "The Simple Public-Key GSS-API Mechanism (SPKM)", October 1996. [RFC2026] Bradner, S., "The Internet Standards Process -- Revi- sion 3", RFC 2026, October 1996. [RFC2044] Yergeau, F., "UTF-8, a Transformation Format of Uni- code and ISO 10646", October 1996. [RFC2045] N. Borenstein, N. Freed, "MIME (Multipurpose Inter- net Mail Extensions) Part One: Mechanisms for Specifying and Describing the Format of Internet Message Bodies", November 1996. [RFC2119] Bradner, S. "Key Words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2234] D. Crocker, P. Overell Augmented BNF for Syntax Spec- ifications: ABNF. Julian Satran Expires February 2003 229 iSCSI 5-August-02 [RFC2246] T. Dierks, C. Allen, " The TLS Protocol Version 1.0. [RFC2373] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 2373, July 1998. [RFC2396] T. Berners-Lee, R. Fielding, L. Masinter "Uniform Resource Identifiers". [RFC2401] S. Kent, R. Atkinson, "Security Architecture for the Internet Protocol", RFC 2401, November 1998. [RFC2404] C. Madson, R. Glenn, "The Use of HMAC-SHA-1-96 within ESP and AH", RFC 2404, November 1998. [RFC2406] S. Kent, R. Atkinson, "IP Encapsulating Security Payload (ESP)", RFC 2406, November 1998. [RFC2407] D. Piper, "The Internet IP Security Domain of Interpre- tation of ISAKMP", RFC 2407, November 1998. [RFC2409] D. Harkins, D. Carrel, "The Internet Key Exchange (IKE)", RFC 2409, November 1998. [RFC2434] T. Narten, and H. Avestrand, "Guidelines for Writing an IANA Considerations Section in RFCs.", RFC2434, October 1998. [RFC2451] R. Pereira, R. Adams " The ESP CBC-Mode Cipher Algo- rithms". [RFC2732] R. Hinden, B. Carpenter, L. Masinter, "Format for Literal IPv6 Addresses in URL's", RFC 2732, December 1999. [RFC2945] Wu, T., "The SRP Authentication and Key Exchange Sys- tem", September 2000. [SAM] ANSI X3.270-1998, SCSI-3 Architecture Model (SAM). [SAM2] T10/1157D, SCSI Architecture Model - 2 (SAM-2). [SBC] NCITS.306-1998, SCSI-3 Block Commands (SBC). [SEQ-EXT] Kent, S., "IP Encapsulating Security Payload (ESP)", Internet draft (work in progress), draft-ietf-ipsec-esp-v3- 01.txt, November 2002. [SEC-IPS] B. Aboba & team "Securing Block Storage Protocols over IP", Internet draft (work in progress), draft-ietf-ips- security-09.txt, February 2002. [SPC]T10/1416-D, SCSI-3 Primary Commands. [SPC3]T10/1416-D, SCSI Primary Commands-3. [STPREP] P. Hoffman, M. Blanchet, "Preparation of Internation- alized Strings", draft-hoffman-stringprep-00.txt, September, 2001 (Work In Progress). [STPREP-iSCSI] M. Bakke, "String Profile for iSCSI Names", draft-ietf-ips-iscsi-string-prep-00.txt, November 2001 (Work In Progress). [UNICODE] Unicode Standard Annex #15, "Unicode Normalization Forms", http://www.unicode.org/unicode/reports/15 Informative References: Julian Satran Expires February 2003 230 iSCSI 5-August-02 [BOOT] P. Sarkar & team draft-ietf-ips-iscsi-boot-03.txt (Work In Progress). [Castagnoli93] G. Castagnoli, S. Braeuer and M. Herrman "Opti- mization of Cyclic Redundancy-Check Codes with 24 and 32 Par- ity Bits", IEEE Transact. on Communications, Vol. 41, No. 6, June 1993. [CRC] ISO 3309, High-Level Data Link Control (CRC 32). [iSCSI-CRC] D. Sheinwald & team, draft-sheinwald-icsci-crc- 02.txt (Work In Progress). [iSCSI-REQ] M. Krueger & team, RFC3347 Small Computer Systems Interface protocol over the Internet (iSCSI) Requirements and Design Considerations [NDT] M. Bakke & team, draft-ietf-ips-iscsi-name-disc-05.txt (Work In Progress) [RFC1602] IAB and IESG, The Internet Standards Process -- Revi- sion 2 [Schneier] B. Schneier, "Applied Cryptography: Protocols, Algo- rithms, and Source Code in C", 2nd edition, John Wiley & Sons, New York, NY, 1996. Authors' Addresses Julian Satran IBM, Haifa Research Lab Haifa University Campus - Mount Carmel Haifa 31905, Israel Phone +972.4.829.6264 E-mail: Julian_Satran@il.ibm.com Kalman Meth Haifa University Campus - Mount Carmel MATAM - Advanced Technology Center Haifa 31905, Israel Phone +972.4.829.6341 E-mail: meth@il.ibm.com Costa Sapuntzakis Cisco Systems, Inc. 170 W. Tasman Drive San Jose, CA 95134, USA Phone: +1.408.525.5497 E-mail: csapuntz@cisco.com Efri Zeidner SANgate Systems, Inc. 41 Hameyasdim Street P.O.B. 1486 Even-Yehuda, Israel 40500 Phone: +972.9.891.9555 Julian Satran Expires February 2003 231 iSCSI 5-August-02 E-mail: efri@sangate.com Mallikarjun Chadalapaka Hewlett-Packard Company 8000 Foothills Blvd. Roseville, CA 95747-5668, USA Phone: +1.916.785.5621 E-mail: cbm@rose.hp.com Comments may be sent to Julian Satran Julian Satran Expires February 2003 232 iSCSI 5-August-02 Appendix A. Sync and Steering with Fixed Interval Markers This appendix presents a simple scheme for synchronization (PDU boundary retrieval). It uses markers that include synchronization information placed at fixed intervals in the TCP stream. A Marker consists of: Byte / 0 | 1 | 2 | 3 | / | | | | |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7| +---------------+---------------+---------------+---------------+ 0| Next-iSCSI-PDU-start pointer - copy #1 | +---------------+---------------+---------------+---------------+ 4| Next-iSCSI-PDU-start pointer - copy #2 | +---------------+---------------+---------------+---------------+ The Marker scheme uses payload byte stream counting that includes every byte placed by iSCSI in the TCP stream except for the markers themselves. It also excludes any bytes that TCP counts but are not originated by iSCSI. The Marker indicates the offset to the next iSCSI PDU header. The Marker is eight bytes in length and contains two 32-bit offset fields that indicate how many bytes to skip in the TCP stream in order to find the next iSCSI PDU header. The marker uses two copies of the pointer so that a marker that spans a TCP packet boundary should leave at least one valid copy in one of the packets. The inserted value is independent of the marker interval. The use of markers is negotiable. The initiator and target MAY indi- cate their readiness to receive and/or send markers during login sep- arately for each connection. The default is No. A.1 Markers At Fixed Intervals A marker is inserted at fixed intervals in the TCP byte stream. Dur- ing login, each end of the iSCSI session specifies the interval at which it is willing to receive the marker, or it disables the marker altogether. If a receiver indicates that it desires a marker, the sender MAY agree (during negotiation) and provide the marker at the desired interval. However, in certain environments, a sender not pro- Julian Satran Expires February 2003 233 iSCSI 5-August-02 viding markers to a receiver wanting markers may suffer an apprecia- ble performance degradation. The marker interval and the initial marker-less interval are counted in terms of the bytes placed in the TCP stream data by iSCSI. When reduced to iSCSI terms, markers MUST indicate the offset to a 4- byte word boundary in the stream. The least significant two bits of each marker word are reserved and are considered 0 for offset compu- tation. Padding iSCSI PDU payloads to 4-byte word boundaries simplifies marker manipulation. A.2 Initial Marker-less Interval To enable the connection setup including the Login Phase negotia- tion, marking (if any) is started only at the first marker interval after the end of the Login Phase. However, in order to enable the marker inclusion and exclusion mechanism to work without knowledge of the length of the Login Phase, the first marker will be placed in the TCP stream as if the Marker-less interval had included markers. Thus all markers appear in the stream at locations conforming to the formula: [(MI + 8) * n - 8] where MI = Marker Interval, n = integer number. As an example if the marker interval is 512 bytes and the login ended at byte 1003 (first iSCSI placed byte is 0) the first marker will be inserted after byte 1031 in the stream. A.3 Negotiation The following operational key=value pairs are used to negotiate the fixed interval markers. The direction (output or input) is relative to the initiator. A.3.1 OFMarker, IFMarker Use: IO Senders: Initiator and Target Scope: CO OFMarker=<boolean-value> Julian Satran Expires February 2003 234 iSCSI 5-August-02 IFMarker=<boolean-value> Default is No. Result function is AND. OFMarker is used to turn on or off the initiator to target markers on the connection. IFMarker is used to turn on or off the target to initiator markers on the connection. Examples: I->OFMarker=Yes,IFMarker=Yes T->OFMarker=Yes,IFMarker=Yes Results in the Marker being used in both directions while I->OFMarker=Yes,IFMarker=Yes T->OFMarker=Yes,IFMarker=No Results in Marker being used from the initiator to the target, but not from the target to initiator. A.3.2 OFMarkInt, IFMarkInt Use: IO Senders: Initiator and Target Scope: CO OFMarkInt is Irrelevant when: OFMarker=No IFMarkInt is Irrelevant when: IFMarker=No Offering: OFMarkInt=<numeric-range-from-1-to-65535> IFMarkInt=<numeric-range-from-1-to-65535> Responding: OFMarkInt=<numeric-value-from-1-to-65535>|Reject IFMarkInt=<numeric-value-from-1-to-65535>|Reject OFMarkInt is used to set the interval for the initiator to target markers on the connection. IFMarkInt is used to set the interval for the target to initiator markers on the connection. Julian Satran Expires February 2003 235 iSCSI 5-August-02 For the offering the initiator or target indicates the minimum to maximum interval (in 4-byte words) it wants the markers for one or both directions. In case it only wants a specific value, only a sin- gle value has to be specified. The responder selects a value within the minimum and maximum offered or the only value offered or indi- cates through the xFMarker key=value its inability to set and/or receive markers. When the interval is unacceptable the responder answers with "Reject". Reject is resetting the marker function in the specified direction (Output or Input) to No. The interval is measured from the end of a marker to the beginning of the next marker. For example, a value of 1024 means 1024 words (4096 bytes of iSCSI payload between markers). The default is 2048. Julian Satran Expires February 2003 236 iSCSI 5-August-02 Appendix B. Examples B.1 Read Operation Example +------------------+-----------------------+----------------------+ |Initiator Function| PDU Type | Target Function | +------------------+-----------------------+----------------------+ | Command request |SCSI Command (READ)>>> | | | (read) | | | +------------------+-----------------------+----------------------+ | | |Prepare Data Transfer | +------------------+-----------------------+----------------------+ | Receive Data | <<< SCSI Data-in | Send Data | +------------------+-----------------------+----------------------+ | Receive Data | <<< SCSI Data-in | Send Data | +------------------+-----------------------+----------------------+ | Receive Data | <<< SCSI Data-in | Send Data | +------------------+-----------------------+----------------------+ | | <<< SCSI Response |Send Status and Sense | +------------------+-----------------------+----------------------+ | Command Complete | | | +------------------+-----------------------+----------------------+ Julian Satran Expires February 2003 237 iSCSI 5-August-02 B.2 Write Operation Example +------------------+-----------------------+---------------------+ |Initiator Function| PDU Type | Target Function | +------------------+-----------------------+---------------------+ | Command request |SCSI Command (WRITE)>>>| Receive command | | (write) | | and queue it | +------------------+-----------------------+---------------------+ | | | Process old commands| +------------------+-----------------------+---------------------+ | | | Ready to process | | | <<< R2T | WRITE command | +------------------+-----------------------+---------------------+ | Send Data | SCSI Data-out >>> | Receive Data | +------------------+-----------------------+---------------------+ | | <<< R2T | Ready for data | +------------------+-----------------------+---------------------+ | | <<< R2T | Ready for data | +------------------+-----------------------+---------------------+ | Send Data | SCSI Data-out >>> | Receive Data | +------------------+-----------------------+---------------------+ | Send Data | SCSI Data-out >>> | Receive Data | +------------------+-----------------------+---------------------+ | | <<< SCSI Response |Send Status and Sense| +------------------+-----------------------+---------------------+ | Command Complete | | | +------------------+-----------------------+---------------------+ B.3 R2TSN/DataSN use Examples Output (write) data DataSN/R2TSN Example Julian Satran Expires February 2003 238 iSCSI 5-August-02 +------------------+-----------------------+----------------------+ |Initiator Function| PDU Type & Content | Target Function | +------------------+-----------------------+----------------------+ | Command request |SCSI Command (WRITE)>>>| Receive command | | (write) | | and queue it | +------------------+-----------------------+----------------------+ | | | Process old commands | +------------------+-----------------------+----------------------+ | | <<< R2T | Ready for data | | | R2TSN = 0 | | +------------------+-----------------------+----------------------+ | | <<< R2T | Ready for more data | | | R2TSN = 1 | | +------------------+-----------------------+----------------------+ | Send Data | SCSI Data-out >>> | Receive Data | | for R2TSN 0 | DataSN = 0, F=0 | | +------------------+-----------------------+----------------------+ | Send Data | SCSI Data-out >>> | Receive Data | | for R2TSN 0 | DataSN = 1, F=1 | | +------------------+-----------------------+----------------------+ | Send Data | SCSI Data >>> | Receive Data | | for R2TSN 1 | DataSN = 0, F=1 | | +------------------+-----------------------+----------------------+ | | <<< SCSI Response |Send Status and Sense | | | ExpDataSN = 0 | | +------------------+-----------------------+----------------------+ | Command Complete | | | +------------------+-----------------------+----------------------+ Input (read) data DataSN Example Julian Satran Expires February 2003 239 iSCSI 5-August-02 +------------------+-----------------------+----------------------+ |Initiator Function| PDU Type | Target Function | +------------------+-----------------------+----------------------+ | Command request |SCSI Command (READ)>>> | | | (read) | | | +------------------+-----------------------+----------------------+ | | | Prepare Data Transfer| +------------------+-----------------------+----------------------+ | Receive Data | <<< SCSI Data-in | Send Data | | | DataSN = 0, F=0 | | +------------------+-----------------------+----------------------+ | Receive Data | <<< SCSI Data-in | Send Data | | | DataSN = 1, F=0 | | +------------------+-----------------------+----------------------+ | Receive Data | <<< SCSI Data-in | Send Data | | | DataSN = 2, F=1 | | +------------------+-----------------------+----------------------+ | | <<< SCSI Response |Send Status and Sense | | | ExpDataSN = 3 | | +------------------+-----------------------+----------------------+ | Command Complete | | | +------------------+-----------------------+----------------------+ Bidirectional DataSN Example Julian Satran Expires February 2003 240 iSCSI 5-August-02 +------------------+-----------------------+----------------------+ |Initiator Function| PDU Type | Target Function | +------------------+-----------------------+----------------------+ | Command request |SCSI Command >>> | | | (Read-Write) | Read-Write | | +------------------+-----------------------+----------------------+ | | | Process old commands | +------------------+-----------------------+----------------------+ | | <<< R2T | Ready to process | | | R2TSN = 0 | WRITE command | +------------------+-----------------------+----------------------+ | * Receive Data | <<< SCSI Data-in | Send Data | | | DataSN = 0, F=0 | | +------------------+-----------------------+----------------------+ | * Receive Data | <<< SCSI Data-in | Send Data | | | DataSN = 1, F=1 | | +------------------+-----------------------+----------------------+ | * Send Data | SCSI Data-out >>> | Receive Data | | for R2TSN 0 | DataSN = 0, F=1 | | +------------------+-----------------------+----------------------+ | | <<< SCSI Response |Send Status and Sense | | | ExpDataSN = 2 | | +------------------+-----------------------+----------------------+ | Command Complete | | | +------------------+-----------------------+----------------------+ *) Send data and Receive Data may be transferred simultaneously as in an atomic Read-Old-Write-New or sequential as in an atomic Read- Update-Write (in the alter case the R2T may follow the received data). Unsolicited and immediate output (write) data with DataSN Example Julian Satran Expires February 2003 241 iSCSI 5-August-02 +------------------+-----------------------+----------------------+ |Initiator Function| PDU Type & Content | Target Function | +------------------+-----------------------+----------------------+ | Command request |SCSI Command (WRITE)>>>| Receive command | | (write) |F=0 | and data | |+ immediate data | | and queue it | +------------------+-----------------------+----------------------+ | Send Unsolicited | SCSI Write Data >>> | Receive more Data | | Data | DataSN = 0, F=1 | | +------------------+-----------------------+----------------------+ | | | Process old commands | +------------------+-----------------------+----------------------+ | | <<< R2T | Ready for more data | | | R2TSN = 0 | | +------------------+-----------------------+----------------------+ | Send Data | SCSI Write Data >>> | Receive Data | | for R2TSN 0 | DataSN = 0, F=1 | | +------------------+-----------------------+----------------------+ | | <<< SCSI Response |Send Status and Sense | | | | | +------------------+-----------------------+----------------------+ | Command Complete | | | +------------------+-----------------------+----------------------+ B.4 CRC Examples N.B. all Values are Hexadecimal 32 bytes of zeroes: Byte: 0 1 2 3 0: 00 00 00 00 ... 28: 00 00 00 00 CRC: aa 36 91 8a 32 bytes of ones: Byte: 0 1 2 3 0: ff ff ff ff Julian Satran Expires February 2003 242 iSCSI 5-August-02 ... 28: ff ff ff ff CRC: 43 ab a8 62 32 bytes of incrementing 00..1f: Byte: 0 1 2 3 0: 00 01 02 03 ... 28: 1c 1d 1e 1f CRC: 4e 79 dd 46 32 bytes of decrementing 1f..00: Byte: 0 1 2 3 0: 1f 1e 1d 1c ... 28: 03 02 01 00 CRC: 5c db 3f 11 Julian Satran Expires February 2003 243 iSCSI 5-August-02 Appendix C. Login Phase Examples In the first example, the initiator and target authenticate each other via Kerberos: I-> Login (CSG,NSG=0,1 T=1) InitiatorName=iqn.1999-07.com.os:hostid.77 TargetName=iqn.1999-07.com.acme:diskarray.sn.88 AuthMethod=KRB5,SRP,None T-> Login (CSG,NSG=0,0 T=0) AuthMethod=KRB5 I-> Login (CSG,NSG=0,1 T=1) KRB_AP_REQ=<krb_ap_req> (krb_ap_req contains the Kerberos V5 ticket and authenticator with MUTUAL-REQUIRED set in the ap-options field) If the authentication is successful, the target proceeds with: T-> Login (CSG,NSG=0,1 T=1) KRB_AP_REP=<krb_ap_rep> (krb_ap_rep is the Kerberos V5 mutual authentication reply) If the authentication is successful, the initiator may proceed with: I-> Login (CSG,NSG=1,0 T=0) FirstBurstLength=8192 T-> Login (CSG,NSG=1,0 T=0) FirstBurstLength=4096 MaxBurst- Length=8192 I-> Login (CSG,NSG=1,0 T=0) MaxBurstLength=8192 ... more iSCSI Operational Parameters T-> Login (CSG,NSG=1,0 T=0) ... more iSCSI Operational Parameters And at the end: I-> Login (CSG,NSG=1,3 T=1) optional iSCSI parameters T-> Login (CSG,NSG=1,3 T=1) "login accept" If the initiator's authentication by the target is not success- ful, the target responds with: Julian Satran Expires February 2003 244 iSCSI 5-August-02 T-> Login "login reject" instead of the Login KRB_AP_REP message, and terminates the connection. If the target's authentication by the initiator is not success- ful, the initiator terminates the connection (without responding to the Login KRB_AP_REP message). In the next example only the initiator is authenticated by the tar- get via Kerberos: I-> Login (CSG,NSG=0,1 T=1) InitiatorName=iqn.1999-07.com.os:hostid.77 TargetName=iqn.1999-07.com.acme:diskarray.sn.88 AuthMethod=SRP,KRB5,None T-> Login-PR (CSG,NSG=0,0 T=0) AuthMethod=KRB5 I-> Login (CSG,NSG=0,1 T=1) KRB_AP_REQ=krb_ap_req (MUTUAL-REQUIRED not set in the ap-options field of krb_ap_req) If the authentication is successful, the target proceeds with: T-> Login (CSG,NSG=0,1 T=1) I-> Login (CSG,NSG=1,0 T=0) ... iSCSI parameters T-> Login (CSG,NSG=1,0 T=0) ... iSCSI parameters . . . T-> Login (CSG,NSG=1,3 T=1)"login accept" In the next example, the initiator and target authenticate each other via SPKM1: I-> Login (CSG,NSG=0,1 T=1) InitiatorName=iqn.1999-07.com.os:hostid.77 TargetName=iqn.1999-07.com.acme:diskarray.sn.88 AuthMethod=SPKM1,KRB5,None T-> Login (CSG,NSG=0,0 T=0) Julian Satran Expires February 2003 245 iSCSI 5-August-02 AuthMethod=SPKM1 I-> Login (CSG,NSG=0,0 T=0) SPKM_REQ=<spkm-req> (spkm-req is the SPKM-REQ token with the mutual-state bit in the options field of the REQ-TOKEN set) T-> Login (CSG,NSG=0,0 T=0) SPKM_REP_TI=<spkm-rep-ti> If the authentication is successful, the initiator proceeds: I-> Login (CSG,NSG=0,1 T=1) SPKM_REP_IT=<spkm-rep-it> If the authentication is successful, the target proceeds with: T-> Login (CSG,NSG=0,1 T=1) The initiator may proceed: I-> Login (CSG,NSG=1,0 T=0) ... iSCSI parameters T-> Login (CSG,NSG=1,0 T=0) ... iSCSI parameters And at the end: I-> Login (CSG,NSG=1,3 T=1) optional iSCSI parameters T-> Login (CSG,NSG=1,3 T=1) "login accept" If the target's authentication by the initiator is not success- ful, the initiator terminates the connection (without responding to the Login SPKM_REP_TI message). If the initiator's authentication by the target is not success- ful, the target responds with: T-> Login "login reject" instead of the Login "proceed and change stage" message, and terminates the connection. In the next example, the initiator and target authenticate each other via SPKM2: Julian Satran Expires February 2003 246 iSCSI 5-August-02 I-> Login (CSG,NSG=0,0 T=0) InitiatorName=iqn.1999-07.com.os:hostid.77 TargetName=iqn.1999-07.com.acme:diskarray.sn.88 AuthMethod=SPKM1,SPKM2 T-> Login-PR (CSG,NSG=0,0 T=0) AuthMethod=SPKM2 I-> Login (CSG,NSG=0,1 T=1) SPKM_REQ=<spkm-req> (spkm-req is the SPKM-REQ token with the mutual-state bit in the options field of the REQ-TOKEN not set) If the authentication is successful, the target proceeds with: T-> Login (CSG,NSG=0,1 T=1) The initiator may proceed: I-> Login (CSG,NSG=1,0 T=0) ... iSCSI parameters T-> Login (CSG,NSG=1,0 T=0) ... iSCSI parameters And at the end: I-> Login (CSG,NSG=1,3 T=1) optional iSCSI parameters T-> Login (CSG,NSG=1,3 T=1) "login accept" In the next example, the initiator and target authenticate each other via SRP: I-> Login (CSG,NSG=0,1 T=1) InitiatorName=iqn.1999-07.com.os:hostid.77 TargetName=iqn.1999-07.com.acme:diskarray.sn.88 AuthMethod=KRB5,SRP,None T-> Login-PR (CSG,NSG=0,0 T=0) AuthMethod=SRP I-> Login (CSG,NSG=0,0 T=0) SRP_U=<user> TargetAuth=Yes Julian Satran Expires February 2003 247 iSCSI 5-August-02 T-> Login (CSG,NSG=0,0 T=0) SRP_N=<N> SRP_g=<g> SRP_s=<s> I-> Login (CSG,NSG=0,0 T=0) SRP_A=<A> T-> Login (CSG,NSG=0,0 T=0) SRP_B=<B> I-> Login (CSG,NSG=0,1 T=1) SRP_M=<M> If the initiator authentication is successful, the target pro- ceeds: T-> Login (CSG,NSG=0,1 T=1) SRP_HM=<H(A | M | K)> Where N, g, s, A, B, M, and H(A | M | K) are defined in [RFC2945]. If the target authentication is not successful, the initiator terminates the connection; otherwise, it proceeds. I-> Login (CSG,NSG=1,0 T=0) ... iSCSI parameters T-> Login (CSG,NSG=1,0 T=0) ... iSCSI parameters And at the end: I-> Login (CSG,NSG=1,3 T=1) optional iSCSI parameters T-> Login (CSG,NSG=1,3 T=1) "login accept" If the initiator authentication is not successful, the target responds with: T-> Login "login reject" Instead of the T-> Login SRP_HM=<H(A | M | K)> message and terminates the connection. In the next example, only the initiator is authenticated by the tar- get via SRP: Julian Satran Expires February 2003 248 iSCSI 5-August-02 I-> Login (CSG,NSG=0,1 T=1) InitiatorName=iqn.1999-07.com.os:hostid.77 TargetName=iqn.1999-07.com.acme:diskarray.sn.88 AuthMethod=KRB5,SRP,None T-> Login-PR (CSG,NSG=0,0 T=0) AuthMethod=SRP I-> Login (CSG,NSG=0,0 T=0) SRP_U=<user> TargetAuth=No T-> Login (CSG,NSG=0,0 T=0) SRP_N=<N> SRP_g=<g> SRP_s=<s> I-> Login (CSG,NSG=0,0 T=0) SRP_A=<A> T-> Login (CSG,NSG=0,0 T=0) SRP_B=<B> I-> Login (CSG,NSG=0,1 T=1) SRP_M=<M> If the initiator authentication is successful, the target pro- ceeds: T-> Login (CSG,NSG=0,1 T=1) I-> Login (CSG,NSG=1,0 T=0) ... iSCSI parameters T-> Login (CSG,NSG=1,0 T=0) ... iSCSI parameters And at the end: I-> Login (CSG,NSG=1,3 T=1) optional iSCSI parameters T-> Login (CSG,NSG=1,3 T=1) "login accept" In the next example the initiator and target authenticate each other via CHAP: I-> Login (CSG,NSG=0,0 T=0) Julian Satran Expires February 2003 249 iSCSI 5-August-02 InitiatorName=iqn.1999-07.com.os:hostid.77 TargetName=iqn.1999-07.com.acme:diskarray.sn.88 AuthMethod=KRB5,CHAP,None T-> Login-PR (CSG,NSG=0,0 T=0) AuthMethod=CHAP I-> Login (CSG,NSG=0,0 T=0) CHAP_A=<A1,A2> T-> Login (CSG,NSG=0,0 T=0) CHAP_A=<A1> CHAP_I=<I> CHAP_C=<C> I-> Login (CSG,NSG=0,1 T=1) CHAP_N=<N> CHAP_R=<R> CHAP_I=<I> CHAP_C=<C> If the initiator authentication is successful, the target pro- ceeds: T-> Login (CSG,NSG=0,1 T=1) CHAP_N=<N> CHAP_R=<R> If the target authentication is not successful, the initiator aborts the connection; otherwise, it proceeds. I-> Login (CSG,NSG=1,0 T=0) ... iSCSI parameters T-> Login (CSG,NSG=1,0 T=0) ... iSCSI parameters And at the end: I-> Login (CSG,NSG=1,3 T=1) optional iSCSI parameters T-> Login (CSG,NSG=1,3 T=1) "login accept" If the initiator authentication is not successful, the target responds with: T-> Login "login reject" Julian Satran Expires February 2003 250 iSCSI 5-August-02 Instead of the Login CHAP_R=<response> "proceed and change stage" message and terminates the connection. In the next example, only the initiator is authenticated by the tar- get via CHAP: I-> Login (CSG,NSG=0,1 T=0) InitiatorName=iqn.1999-07.com.os:hostid.77 TargetName=iqn.1999-07.com.acme:diskarray.sn.88 AuthMethod=KRB5,CHAP,None T-> Login-PR (CSG,NSG=0,0 T=0) AuthMethod=CHAP I-> Login (CSG,NSG=0,0 T=0) CHAP_A=<A1,A2> T-> Login (CSG,NSG=0,0 T=0) CHAP_A=<A1> CHAP_I=<I> CHAP_C=<C> I-> Login (CSG,NSG=0,1 T=1) CHAP_N=<N> CHAP_R=<R> If the initiator authentication is successful, the target pro- ceeds: T-> Login (CSG,NSG=0,1 T=1) I-> Login (CSG,NSG=1,0 T=0) ... iSCSI parameters T-> Login (CSG,NSG=1,0 T=0) ... iSCSI parameters And at the end: I-> Login (CSG,NSG=1,3 T=1) optional iSCSI parameters T-> Login (CSG,NSG=1,3 T=1) "login accept" Julian Satran Expires February 2003 251 iSCSI 5-August-02 In the next example, the initiator does not offer any security param- eters. It therefore may offer iSCSI parameters on the Login PDU with the T bit set to 1, and the target may respond with a final Login Response PDU immediately: I-> Login (CSG,NSG=1,3 T=1) InitiatorName=iqn.1999-07.com.os:hostid.77 TargetName=iqn.1999-07.com.acme:diskarray.sn.88 ... iSCSI parameters T-> Login (CSG,NSG=1,3 T=1) "login accept" ... ISCSI parameters In the next example, the initiator does offer security parame- ters on the Login PDU, but the target does not choose any (i.e., chooses the "None" values): I-> Login (CSG,NSG=0,1 T=1) InitiatorName=iqn.1999-07.com.os:hostid.77 TargetName=iqn.1999-07.com.acme:diskarray.sn.88 AuthMethod=KRB5,SRP,None T-> Login-PR (CSG,NSG=0,1 T=1) AuthMethod=None I-> Login (CSG,NSG=1,0 T=0) ... iSCSI parameters T-> Login (CSG,NSG=1,0 T=0) ... iSCSI parameters And at the end: I-> Login (CSG,NSG=1,3 T=1) optional iSCSI parameters T-> Login (CSG,NSG=1,3 T=1) "login accept" Julian Satran Expires February 2003 252 iSCSI 5-August-02 Appendix D. SendTargets Operation To reduce the amount of configuration required on an initiator, iSCSI provides the SendTargets text request. The initiator uses the Send- Targets request to get a list of targets to which it may have access, as well as the list of addresses (IP address and TCP port) on which these targets may be accessed. To make use of SendTargets, an initiator must first establish one of two types of sessions. If the initiator establishes the session using the key "SessionType=Discovery", the session is a discovery session, and a target name does not need to be specified. Other- wise, the session is a normal, operational session. The SendTargets command MUST only be sent during the Full Feature Phase of a normal or discovery session. A system that contains targets MUST support discovery sessions on each of its iSCSI IP address-port pairs, and MUST support the Send- Targets command on the discovery session. A target MUST return all path information (IP address-port pairs and portal group tags) for the targets for which the requesting initiator is authorized. A target MUST support the SendTargets command on operational ses- sions; these will only return path information about the target to which the session is connected, and need not return information about other target names that may be defined in the responding system. An initiator MAY make use of the SendTargets as it sees fit. A SendTargets command consists of a single Text request PDU. This PDU contains exactly one text key and value. The text key MUST be SendTargets. The expected response depends upon the value, as well as whether the session is a discovery or operational session. The value must be one of: All The initiator is requesting that information on all relevant targets known to the implementation be returned. This value MUST be supported on a discovery session, and MUST NOT be supported on an operational session. <iSCSI-target-name> Julian Satran Expires February 2003 253 iSCSI 5-August-02 If an iSCSI target name is specified, the session should respond with addresses for only the named target, if possi- ble. This value MUST be supported on discovery sessions. A discovery session MUST be capable of returning addresses for those targets that would have been returned had value=All been designated. <nothing> The session should respond only with addresses for the target to which the session is logged in. This MUST be supported on operational sessions, and MUST NOT return targets other than the one to which the session is logged in. The response to this command is a text response that contains a list of zero or more targets and, optionally, their addresses. Each tar- get is returned as a target record. A target record begins with the TargetName text key, followed by a list of TargetAddress text keys, and bounded by the end of the text response or the next TargetName key, which begins a new record. No text keys other than TargetName and TargetAddress are permitted within a SendTargets response. For the format of the TargetName, see Section 11.4 TargetName. A discovery session MAY respond to a SendTargets request with its complete list of targets, or with a list of targets that is based on the name of the initiator logged in to the session. A SendTargets response MUST NOT not contain target names if there are no targets for the requesting initiator to access. Each target record returned includes zero or more TargetAddress fields. Each target record starts with one text key of the form: TargetName=<target-name-goes-here> Followed by zero or more address keys of the form: TargetAddress=<hostname-or-ipaddress>[:<tcp-port>],<portal- group-tag> The hostname-or-ipaddress contains a domain name, IPv4 address, or IPv6 address, as specified for the TargetAddress key. Julian Satran Expires February 2003 254 iSCSI 5-August-02 Each TargetAddress belongs to a portal group, identified by its numeric portal group tag (as in Section 11.9 TargetPortalGroupTag). The iSCSI target name, together with this tag, constitutes the SCSI port identifier; the tag need be unique only within a given target name's list of addresses. Multiple-connection sessions can span iSCSI addresses that belong to the same portal group. Multiple-connection sessions cannot span iSCSI addresses that belong to different portal groups. If a SendTargets response reports an iSCSI address for a target, it SHOULD also report all other addresses in its portal group in the same response. A SendTargets text response can be longer than a single Text Response PDU, and makes use of the long text responses as specified. After obtaining a list of targets from the discovery target session, an iSCSI initiator may initiate new sessions to log in to the discov- ered targets for full operation. The initiator MAY keep the discov- ery session open, and MAY send subsequent SendTargets commands to discover new targets. Examples: This example is the SendTargets response from a single target that has no other interface ports. Initiator sends text request that contains: SendTargets=All Target sends a text response that contains: TargetName=iqn.1993-11.com.acme:diskarray.sn.8675309 All the target had to return in the simple case was the target name. It is assumed by the initiator that the IP address and TCP port for Julian Satran Expires February 2003 255 iSCSI 5-August-02 this target are the same as used on the current connection to the default iSCSI target. The next example has two internal iSCSI targets, each accessible via two different ports with different IP addresses. The following is the text response: TargetName=iqn.1993-11.com.acme:diskarray.sn.8675309 TargetAddress=10.1.0.45:3000,1 TargetAddress=10.1.1.45:3000,2 TargetName=iqn.1993-11.com.acme:diskarray.sn.1234567 TargetAddress=10.1.0.45:3000,1 TargetAddress=10.1.1.45:3000,2 Both targets share both addresses; the multiple addresses are likely used to provide multi-path support. The initiator may connect to either target name on either address. Each of the addresses has its own portal group tag; they do not support spanning multiple-connec- tion sessions with each other. Keep in mind also that the portal group tags for the two named targets are independent of one another; portal group "1" on the first target is not necessarily the same as portal group "1" on the second. In the above example, a DNS host name or an IPv6 address could have been returned instead of an IPv4 address. The next text response shows a target that supports spanning ses- sions across multiple addresses, and illustrates further the use of the portal group tags: TargetName=iqn.1993-11.com.acme:diskarray.sn.8675309 TargetAddress=10.1.0.45:3000,1 TargetAddress=10.1.1.46:3000,1 TargetAddress=10.1.0.47:3000,2 TargetAddress=10.1.1.48:3000,2 TargetAddress=10.1.1.49:3000,3 In this example, any of the target addresses can be used to reach the same target. A single-connection session can be established to any of these TCP addresses. A multiple-connection session could span addresses .45 and .46 or .47 and .48, but cannot span any other com- bination. A TargetAddress with its own tag (.49) cannot be combined with any other address within the same session. Julian Satran Expires February 2003 256 iSCSI 5-August-02 This SendTargets response does not indicate whether .49 supports mul- tiple connections per session; it communicated via the MaxConnec- tions text key upon login to the target. Julian Satran Expires February 2003 257 iSCSI 5-August-02 Appendix E. Algorithmic Presentation of Error Recovery Classes This appendix illustrates the error recovery classes using a pseudo- programming-language. The procedure names are chosen to be obvious to most implementers. Each of the recovery classes described has ini- tiator procedures as well as target procedures. These algorithms focus on outlining the mechanics of error recovery classes, and do not exhaustively describe all other aspects/cases. Examples of this approach are: - Handling for only certain Opcode types is shown. - Only certain reason codes (for example, Recovery in Logout command) are outlined. - Resultant cases, such as recovery of Synchronization on a header digest error are considered out-of-scope in these algorithms. In this particular example a header digest error may lead to connection recovery if some type of sync and steering layer is not implemented. These algorithms strive to convey the iSCSI error recovery concepts in the simplest terms, and are not designed to be optimal. E.1 General Data Structure and Procedure Description This section defines the procedures and data structures that are com- monly used by all the error recovery algorithms. The structures may not be the exhaustive representations of what is required for a typi- cal implementation. Data structure definitions - struct TransferContext { int TargetTransferTag; int ExpectedDataSN; }; struct TCB { /* task control block */ Boolean SoFarInOrder; int ExpectedDataSN; /* used for both R2Ts, and Data */ int MissingDataSNList[MaxMissingDPDU]; Boolean FbitReceived; Boolean StatusXferd; Boolean CurrentlyAllegiant; Julian Satran Expires February 2003 258 iSCSI 5-August-02 int ActiveR2Ts; int Response; char *Reason; struct TransferContext TransferContextList[MaxOutStandingR2T]; int InitiatorTaskTag; int CmdSN; int SNACK_Tag; }; struct Connection { struct Session SessionReference; Boolean SoFarInOrder; int CID; int State; int CurrentTimeout; int ExpectedStatSN; int MissingStatSNList[MaxMissingSPDU]; Boolean PerformConnectionCleanup; }; struct Session { int NumConnections; int CmdSN; int Maxconnections; int ErrorRecoveryLevel; struct iSCSIEndpoint OtherEndInfo; struct Connection ConnectionList[MaxSupportedConns]; }; Procedure descriptions - Receive-a-In-PDU(transport connection, inbound PDU); check-basic-validity(inbound PDU); Start-Timer(timeout handler, argument, timeout value); Build-And-Send-Reject(transport connection, bad PDU, reason code); E.2 Within-command Error Recovery Algorithms E.2.1 Procedure Descriptions Recover-Data-if-Possible(last required DataSN, task control block); Build-And-Send-DSnack(task control block); Build-And-Send-RDSnack(task control block); Build-And-Send-Abort(task control block); Julian Satran Expires February 2003 259 iSCSI 5-August-02 SCSI-Task-Completion(task control block); Build-And-Send-A-Data-Burst(transport connection, data-descriptor, task control block); Build-And-Send-R2T(transport connection, data-descriptor, task control block); Build-And-Send-Status(transport connection, task control block); Transfer-Context-Timeout-Handler(transfer context); Notes: - One procedure used in this section: Handle-Status-SNACK- request is defined in Within-connection recovery algorithms. - The Response processing pseudo-code, shown in the target algorithms, applies to all solicited PDUs that carry StatSN - SCSI Response, Text Response etc. E.2.2 Initiator Algorithms Recover-Data-if-Possible(LastRequiredDataSN, TCB) { if (operational ErrorRecoveryLevel > 0) { if (# of missing PDUs is trackable) { Note the missing DataSNs in TCB. if (the task spanned a change in MaxRecvDataSegmentLength) { if (TCB.StatusXferd is TRUE) drop the status PDU; Build-And-Send-RDSnack(TCB); } else { Build-And-Send-DSnack(TCB); } } else { TCB.Reason = "Protocol service CRC error"; } } else { TCB.Reason = "Protocol service CRC error"; } if (TCB.Reason == "Protocol service CRC error") { Clear the missing PDU list in the TCB. if (TCB.StatusXferd is not TRUE) Build-And-Send-Abort(TCB); } } Julian Satran Expires February 2003 260 iSCSI 5-August-02 Receive-a-In-PDU(Connection, CurrentPDU) { check-basic-validity(CurrentPDU); if (Header-Digest-Bad) discard, return; Retrieve TCB for CurrentPDU.InitiatorTaskTag. if ((CurrentPDU.type == Data) or (CurrentPDU.type = R2T)) { if (Data-Digest-Bad for Data) { send-data-SNACK = TRUE; LastRequiredDataSN = CurrentPDU.DataSN; } else { if (TCB.SoFarInOrder = TRUE) { if (current DataSN is expected) { Increment TCB.ExpectedDataSN. } else { TCB.SoFarInOrder = FALSE; send-data-SNACK = TRUE; } } else { if (current DataSN was considered missing) { remove current DataSN from missing PDU list. } else if (current DataSN is higher than expected) { send-data-SNACK = TRUE; } else { discard, return; } Adjust TCB.ExpectedDataSN if appropriate. } LastRequiredDataSN = CurrentPDU.DataSN - 1; } if (send-data-SNACK is TRUE and task is not already considered failed) { Recover-Data-if-Possible(LastRequiredDataSN, TCB); } if (missing data PDU list is empty) { TCB.SoFarInOrder = TRUE; } if (CurrentPDU.type == R2T) { Increment ActiveR2Ts for this task. Create a data-descriptor for the data burst. Build-And-Send-A-Data-Burst(Connection, data-descriptor, TCB); Julian Satran Expires February 2003 261 iSCSI 5-August-02 } } else if (CurrentPDU.type == Response) { if (Data-Digest-Bad) { send-status-SNACK = TRUE; } else { TCB.StatusXferd = TRUE; Store the status information in TCB. if (ExpDataSN does not match) { TCB.SoFarInOrder = FALSE; Recover-Data-if-Possible(current DataSN, TCB); } if (missing data PDU list is empty) { TCB.SoFarInOrder = TRUE; } } } else { /* REST UNRELATED TO WITHIN-COMMAND-RECOVERY, NOT SHOWN */ } if ((TCB.SoFarInOrder == TRUE) and (TCB.StatusXferd == TRUE)) { SCSI-Task-Completion(TCB); } } E.2.3 Target Algorithms Receive-a-In-PDU(Connection, CurrentPDU) { check-basic-validity(CurrentPDU); if (Header-Digest-Bad) discard, return; Retrieve TCB for CurrentPDU.InitiatorTaskTag. if (CurrentPDU.type == Data) { Retrieve TContext from CurrentPDU.TargetTransferTag; if (Data-Digest-Bad) { Build-And-Send-Reject(Connection, CurrentPDU, Payload-Digest-Error); Note the missing data PDUs in MissingDataRange[]. send-recovery-R2T = TRUE; } else { if (current DataSN is not expected) { Note the missing data PDUs in MissingDataRange[]. send-recovery-R2T = TRUE; } Julian Satran Expires February 2003 262 iSCSI 5-August-02 if (CurrentPDU.Fbit == TRUE) { if (current PDU is solicited) { Decrement TCB.ActiveR2Ts. } if ((current PDU is unsolicited and data received is less than I/O length and data received is less than FirstBurstLength) or (current PDU is solicited and the length of this burst is less than expected)) { send-recovery-R2T = TRUE; Note the missing data in MissingDataRange[]. } } } Increment TContext.ExpectedDataSN. if (send-recovery-R2T is TRUE and task is not already considered failed) { if (operational ErrorRecoveryLevel > 0) { Increment TCB.ActiveR2Ts. Create a data-descriptor for the data burst from MissingDataRange. Build-And-Send-R2T(Connection, data-descriptor, TCB); } else { if (current PDU is the last unsolicited) TCB.Reason = "Not enough unsolicited data"; else TCB.Reason = "Protocol service CRC error"; } } if (TCB.ActiveR2Ts == 0) { Build-And-Send-Status(Connection, TCB); } } else if (CurrentPDU.type == SNACK) { snack-failure = FALSE; if (operational ErrorRecoveryLevel > 0) { if (CurrentPDU.type == Data/R2T) { if (the request is satisfiable) { if (request for Data) { Create a data-descriptor for the data burst from BegRun and RunLength. Build-And-Send-A-Data-Burst(Connection, data-descriptor, TCB); } else { /* R2T */ Julian Satran Expires February 2003 263 iSCSI 5-August-02 Create a data-descriptor for the data burst from BegRun and RunLength. Build-And-Send-R2T(Connection, data-descriptor, TCB); } } else { snack-failure = TRUE; } } else if (CurrentPDU.type == status) { Handle-Status-SNACK-request(Connection, CurrentPDU); } else if (CurrentPDU.type == DataACK) { Consider all data upto CurrentPDU.BegRun as acknowledged. Free up the retransmission resources for that data. } else if (CurrentPDU.type == R-Data SNACK) { Create a data descriptor for a data burst covering all unacknowledged data. Build-And-Send-A-Data-Burst(Connection, data-descriptor, TCB); TCB.SNACK_Tag = CurrentPDU.SNACK_Tag; if (there's no more data to send) { Build-And-Send-Status(Connection, TCB); } } } else { /* operational ErrorRecoveryLevel = 0 */ snack-failure = TRUE; } if (snack-failure == TRUE) { Build-And-Send-Reject(Connection, CurrentPDU, SNACK-Reject); if (TCB.StatusXferd != TRUE) { TCB.Reason = "SNACK Rejected"; Build-And-Send-Status(Connection, TCB); } } } else { /* REST UNRELATED TO WITHIN-COMMAND-RECOVERY, NOT SHOWN */ } } Transfer-Context-Timeout-Handler(TContext) { Retrieve TCB and Connection from TContext. Julian Satran Expires February 2003 264 iSCSI 5-August-02 Decrement TCB.ActiveR2Ts. if (operational ErrorRecoveryLevel > 0 and task is not already considered failed) { Note the missing data PDUs in MissingDataRange[]. Create a data-descriptor for the data burst from MissingDataRange[]. Build-And-Send-R2T(Connection, data-descriptor, TCB); } else { TCB.Reason = "Protocol service CRC error"; if (TCB.ActiveR2Ts = 0) { Build-And-Send-Status(Connection, TCB); } } } E.3 Within-connection Recovery Algorithms E.3.1 Procedure Descriptions Procedure descriptions: Recover-Status-if-Possible(transport connection, currently received PDU); Evaluate-a-StatSN(transport connection, currently received PDU); Retransmit-Command-if-Possible(transport connection, CmdSN); Build-And-Send-SSnack(transport connection); Build-And-Send-Command(transport connection, task control block); Command-Acknowledge-Timeout-Handler(task control block); Status-Expect-Timeout-Handler(transport connection); Build-And-Send-Nop-Out(transport connection); Handle-Status-SNACK-request(transport connection, status SNACK PDU); Retransmit-Status-Burst(status SNACK, task control block); Is-Acknowledged(beginning StatSN, run length); Implementation-specific tunables: InitiatorProactiveSNACKEnabled Notes: - The initiator algorithms only deal with unsolicited Nop-In PDUs for generating status SNACKs. Solicited Nop-In PDU has an assigned StatSN, which, when out of order, could trigger the out of order StatSN handling in Within-command algo- rithms, again leading to Recover-Status-if-Possible. - The pseudo-code shown may result in the retransmission of unacknowledged commands in more cases than necessary. This Julian Satran Expires February 2003 265 iSCSI 5-August-02 will not, however, affect the correctness of the operation because the target is required to discard the duplicate Cmd- SNs. - The procedure Build-And-Send-Async is defined in the Connec- tion recovery algorithms. - The procedure Status-Expect-Timeout-Handler describes how initiators may proactively attempt to retrieve the Status if they so choose. This procedure is assumed to be triggered much before the standard ULP timeout. E.3.2 Initiator Algorithms Recover-Status-if-Possible(Connection, CurrentPDU) { if ((Connection.state == LOGGED_IN) and connection is not already considered failed) { if (operational ErrorRecoveryLevel > 0) { if (# of missing PDUs is trackable) { Note the missing StatSNs in Connection that were not already requested with SNACK; Build-And-Send-SSnack(Connection); } else { Connection.PerformConnectionCleanup = TRUE; } } else { Connection.PerformConnectionCleanup = TRUE; } if (Connection.PerformConnectionCleanup == TRUE) { Start-Timer(Connection-Cleanup-Handler, Connection, 0); } } } Retransmit-Command-if-Possible(Connection, CmdSN) { if (operational ErrorRecoveryLevel > 0) { Retrieve the InitiatorTaskTag, and thus TCB for the CmdSN. Build-And-Send-Command(Connection, TCB); } } Evaluate-a-StatSN(Connection, CurrentPDU) { Julian Satran Expires February 2003 266 iSCSI 5-August-02 send-status-SNACK = FALSE; if (Connection.SoFarInOrder == TRUE) { if (current StatSN is the expected) { Increment Connection.ExpectedStatSN. } else { Connection.SoFarInOrder = FALSE; send-status-SNACK = TRUE; } } else { if (current StatSN was considered missing) { remove current StatSN from the missing list. } else { if (current StatSN is higher than expected){ send-status-SNACK = TRUE; } else { send-status-SNACK = FALSE; discard the PDU; } } Adjust Connection.ExpectedStatSN if appropriate. if (missing StatSN list is empty) { Connection.SoFarInOrder = TRUE; } } return send-status-SNACK; } Receive-a-In-PDU(Connection, CurrentPDU) { check-basic-validity(CurrentPDU); if (Header-Digest-Bad) discard, return; Retrieve TCB for CurrentPDU.InitiatorTaskTag. if (CurrentPDU.type == Nop-In) { if (the PDU is unsolicited) { if (current StatSN is not expected) { Recover-Status-if-Possible(Connection, CurrentPDU); } if (current ExpCmdSN is not Session.CmdSN) { Retransmit-Command-if-Possible(Connection, CurrentPDU.ExpCmdSN); } } } else if (CurrentPDU.type == Reject) { Julian Satran Expires February 2003 267 iSCSI 5-August-02 if (it is a data digest error on immediate data) { Retransmit-Command-if-Possible(Connection, CurrentPDU.BadPDUHeader.CmdSN); } } else if (CurrentPDU.type == Response) { send-status-SNACK = Evaluate-a-StatSN(Connection, CurrentPDU); if (send-status-SNACK == TRUE) Recover-Status-if-Possible(Connection, CurrentPDU); } else { /* REST UNRELATED TO WITHIN-CONNECTION-RECOVERY, * NOT SHOWN */ } } Command-Acknowledge-Timeout-Handler(TCB) { Retrieve the Connection for TCB. Retransmit-Command-if-Possible(Connection, TCB.CmdSN); } Status-Expect-Timeout-Handler(Connection) { if (operational ErrorRecoveryLevel > 0) { Build-And-Send-Nop-Out(Connection); } else if (InitiatorProactiveSNACKEnabled){ if ((Connection.state == LOGGED_IN) and connection is not already considered failed) { Build-And-Send-SSnack(Connection); } } } E.3.3 Target Algorithms Handle-Status-SNACK-request(Connection, CurrentPDU) { if (operational ErrorRecoveryLevel > 0) { if (request for an acknowledged run) { Build-And-Send-Reject(Connection, CurrentPDU, Protocol-Error); } else if (request for an untransmitted run) { discard, return; } else { Julian Satran Expires February 2003 268 iSCSI 5-August-02 Retransmit-Status-Burst(CurrentPDU, TCB); } } else { Build-And-Send-Async(Connection, DroppedConnection, DefaultTime2Wait, DefaultTime2Retain); } } E.4 Connection Recovery Algorithms E.4.1 Procedure Descriptions Build-And-Send-Async(transport connection, reason code, minimum time, maximum time); Pick-A-Logged-In-Connection(session); Build-And-Send-Logout(transport connection, logout connection identifier, reason code); PerformImplicitLogout(transport connection, logout connection identifier, target information); PerformLogin(transport connection, target information); CreateNewTransportConnection(target information); Build-And-Send-Command(transport connection, task control block); Connection-Cleanup-Handler(transport connection); Connection-Resource-Timeout-Handler(transport connection); Quiesce-And-Prepare-for-New-Allegiance(session, task control block); Build-And-Send-Logout-Response(transport connection, CID of connection in recovery, reason code); Build-And-Send-TaskMgmt-Response(transport connection, task mgmt command PDU, response code); Establish-New-Allegiance(task control block, transport connection); Schedule-Command-To-Continue(task control block); Notes: - Transport exception conditions, such as unexpected connec- tion termination, connection reset, and hung connection while the connection is in the full-feature phase, are all assumed to be asynchronously signaled to the iSCSI layer using the Transport_Exception_Handler procedure. E.4.2 Initiator Algorithms Receive-a-In-PDU(Connection, CurrentPDU) { check-basic-validity(CurrentPDU); Julian Satran Expires February 2003 269 iSCSI 5-August-02 if (Header-Digest-Bad) discard, return; Retrieve TCB from CurrentPDU.InitiatorTaskTag. if (CurrentPDU.type == Async) { if (CurrentPDU.AsyncEvent == ConnectionDropped) { Retrieve the AffectedConnection for CurrentPDU.Parameter1. AffectedConnection.CurrentTimeout = CurrentPDU.Parameter3; AffectedConnection.State = CLEANUP_WAIT; Start-Timer(Connection-Cleanup-Handler, AffectedConnection, CurrentPDU.Parameter2); } else if (CurrentPDU.AsyncEvent == LogoutRequest)) { AffectedConnection = Connection; AffectedConnection.State = LOGOUT_REQUESTED; AffectedConnection.PerformConnectionCleanup = TRUE; AffectedConnection.CurrentTimeout = CurrentPDU.Parameter3; Start-Timer(Connection-Cleanup-Handler, AffectedConnection, 0); } else if (CurrentPDU.AsyncEvent == SessionDropped)) { for (each Connection) { Connection.State = CLEANUP_WAIT; Connection.CurrentTimeout = CurrentPDU.Parameter3; Start-Timer(Connection-Cleanup-Handler, Connection, CurrentPDU.Parameter2); } Session.state = FAILED; } } else if (CurrentPDU.type == LogoutResponse) { Retrieve the CleanupConnection for CurrentPDU.CID. if (CurrentPDU.Response = failure) { CleanupConnection.State = CLEANUP_WAIT; } else { CleanupConnection.State = FREE; } } else if (CurrentPDU.type == LoginResponse) { if (this is a response to an implicit Logout) { Retrieve the CleanupConnection. if (successful) { CleanupConnection.State = FREE; Connection.State = LOGGED_IN; } else { CleanupConnection.State = CLEANUP_WAIT; DestroyTransportConnection(Connection); } Julian Satran Expires February 2003 270 iSCSI 5-August-02 } } else { /* REST UNRELATED TO CONNECTION-RECOVERY, * NOT SHOWN */ } if (CleanupConnection.State == FREE) { for (each command that was active on CleanupConnection) { /* Establish new connection allegiance */ NewConnection = Pick-A-Logged-In-Connection(Session); Build-And-Send-Command(NewConnection, TCB); } } } Connection-Cleanup-Handler(Connection) { Retrieve Session from Connection. if (Connection can still exchange iSCSI PDUs) { NewConnection = Connection; } else { Start-Timer(Connection-Resource-Timeout-Handler, Connection, Connection.CurrentTimeout); if (there are other logged-in connections) { NewConnection = Pick-A-Logged-In-Connection(Session); } else { NewConnection = CreateTransportConnection(Session.OtherEndInfo); Initiate an implicit Logout on NewConnection for Connection.CID. return; } } Build-And-Send-Logout(NewConnection, Connection.CID, RecoveryRemove); } Transport_Exception_Handler(Connection) { Connection.PerformConnectionCleanup = TRUE; if (the event is an unexpected transport disconnect) { Connection.State = CLEANUP_WAIT; Connection.CurrentTimeout = DefaultTime2Retain; Start-Timer(Connection-Cleanup-Handler, Connection, DefaultTime2Wait); Julian Satran Expires February 2003 271 iSCSI 5-August-02 } else { Connection.State = FREE; } } E.4.3 Target Algorithms Receive-a-In-PDU(Connection, CurrentPDU) { check-basic-validity(CurrentPDU); if (Header-Digest-Bad) discard, return; else if (Data-Digest-Bad) { Build-And-Send-Reject(Connection, CurrentPDU, Payload-Digest-Error); discard, return; } Retrieve TCB and Session. if (CurrentPDU.type == Logout) { if (CurrentPDU.ReasonCode = RecoveryRemove) { Retrieve the CleanupConnection from CurrentPDU.CID). for (each command active on CleanupConnection) { Quiesce-And-Prepare-for-New-Allegiance(Session, TCB); TCB.CurrentlyAllegiant = FALSE; } Cleanup-Connection-State(CleanupConnection); if ((quiescing successful) and (cleanup successful)) { Build-And-Send-Logout-Response(Connection, CleanupConnection.CID, Success); } else { Build-And-Send-Logout-Response(Connection, CleanupConnection.CID, Failure); } } } else if ((CurrentPDU.type == Login) and operational ErrorRecoveryLevel == 2) { Retrieve the CleanupConnection from CurrentPDU.CID). for (each command active on CleanupConnection) { Quiesce-And-Prepare-for-New-Allegiance(Session, TCB); TCB.CurrentlyAllegiant = FALSE; } Cleanup-Connection-State(CleanupConnection); if ((quiescing successful) and (cleanup successful)) { Julian Satran Expires February 2003 272 iSCSI 5-August-02 Continue with the rest of the Login processing; } else { Build-And-Send-Login-Response(Connection, CleanupConnection.CID, Target Error); } } } else if (CurrentPDU.type == TaskManagement) { if (CurrentPDU.function == "TaskReassign") { if (Session.ErrorRecoveryLevel < 2) { Build-And-Send-TaskMgmt-Response(Connection, CurrentPDU, "Allegiance reassignment not supported"); } else if (task is not found) { Build-And-Send-TaskMgmt-Response(Connection, CurrentPDU, "Task not in task set"); } else if (task is currently allegiant) { Build-And-Send-TaskMgmt-Response(Connection, CurrentPDU, "Task still allegiant"); } else { Establish-New-Allegiance(TCB, Connection); TCB.CurrentlyAllegiant = TRUE; Schedule-Command-To-Continue(TCB); } } } else { /* REST UNRELATED TO CONNECTION-RECOVERY, * NOT SHOWN */ } } Transport_Exception_Handler(Connection) { Connection.PerformConnectionCleanup = TRUE; if (the event is an unexpected transport disconnect) { Connection.State = CLEANUP_WAIT; Start-Timer(Connection-Resource-Timeout-Handler, Connection, (DefaultTime2Wait+DefaultTime2Retain)); if (this Session has full-feature phase connections left) { DifferentConnection = Pick-A-Logged-In-Connection(Session); Build-And-Send-Async(DifferentConnection, DroppedConnection, DefaultTime2Wait, DefaultTime2Retain); } Julian Satran Expires February 2003 273 iSCSI 5-August-02 } else { Connection.State = FREE; } } Julian Satran Expires February 2003 274 iSCSI 5-August-02 Appendix F. Clearing effects of various events on targets F.1 Clearing effects on iSCSI objects The following tables describe the target behavior on receiving the events specified in the rows of the table. The second table is merely an extension of the first table and defines clearing actions for more objects on the same events. The legend is: Y = Yes (cleared/discarded/reset on the event specified in the row). Unless noted otherwise, the clearing action is applicable only for the issuing initiator port. N = No (not affected on the event specified in the row, i.e. stays at previous value). NA = Not Applicable, or Not Defined. Julian Satran Expires February 2003 275 iSCSI 5-August-02 +-----+-----+-----+-----+-----+ |IT(1)|IC(2)|CT(5)|ST(6)|PP(7)| +---------------------+-----+-----+-----+-----+-----+ |connection failure(8)|Y |Y |N |N |Y | +---------------------+-----+-----+-----+-----+-----+ |connection state |NA |NA |Y |N |NA | |timeout (9) | | | | | | +---------------------+-----+-----+-----+-----+-----+ |session timeout/ |Y |Y |Y |Y |Y(14)| |closure/reinstatement| | | | | | |(10) | | | | | | +---------------------+-----+-----+-----+-----+-----+ |session continuation |NA |NA |N(11)|N |NA | |(12) | | | | | | +---------------------+-----+-----+-----+-----+-----+ |successful connection|Y |Y |Y |N |Y(13)| |close logout | | | | | | +---------------------+-----+-----+-----+-----+-----+ |session failure (18) |Y |Y |N |N |Y | +---------------------+-----+-----+-----+-----+-----+ |successful recovery |Y |Y |N |N |Y(13)| |Logout | | | | | | +---------------------+-----+-----+-----+-----+-----+ |failed Logout |Y |Y |N |N |Y | +---------------------+-----+-----+-----+-----+-----+ |connection Login |NA |NA |NA |Y(15)|NA | |(leading) | | | | | | +---------------------+-----+-----+-----+-----+-----+ |connection Login |NA |NA |N(11)|N |Y | |(non-leading) | | | | | | +---------------------+-----+-----+-----+-----+-----+ |target cold reset(16)|Y |Y |Y |Y |Y | +---------------------+-----+-----+-----+-----+-----+ |target warm reset(16)|Y |Y |Y |Y |Y | +---------------------+-----+-----+-----+-----+-----+ |LU reset(19) |Y |Y |Y |Y |Y | +---------------------+-----+-----+-----+-----+-----+ |powercycle(16) |Y |Y |Y |Y |Y | +---------------------+-----+-----+-----+-----+-----+ 1.Incomplete TTTs - Target Transfer Tags on which the target is still expecting PDUs to be received. Examples include TTTs received via R2T, NOP-IN etc. Julian Satran Expires February 2003 276 iSCSI 5-August-02 2.Immediate Commands - immediate commands but waiting for execution on a target, for ex., Abort Task Set. 5.Connection Tasks - tasks that are active on the iSCSI connection in question. 6.Session Tasks - tasks that are active on the entire iSCSI session, so is a union of `connection tasks' on all participating connections. 7.Partial PDUs (if any) - PDUs that are partially sent and waiting for transport window credit to complete the transmission. 8.Connection failure is a connection exception condition -one of transport connection shutdown, transport connection reset, or trans- port connection timeout abruptly terminating the iSCSI full-feature phase connection. A connection failure always takes the connection state machine to the CLEANUP_WAIT state. 9.Connection state timeout happens if a connection spends more time than agreed upon during Login negotiation in the CLEANUP_WAIT state, and this takes the connection to the FREE state (M1 transition in connection cleanup state diagram). 10.These are defined in Section 4.3.5 Session reinstatement, closure and timeout. 11.This clearing effect is however "Y" only if it is a connection reinstatement and the operational ErrorRecoveryLevel is less than 2. 12.Session continuation is as defined in Section 4.3.6 Session con- tinuation and failure. 13.This clearing effect is valid only if the connection is being logged-out on a different connection and when the connection being logged out on the target may have some partial PDUs pending to be sent. In all other cases, the effect is "NA". 14.This clearing effect is valid only for a "close the session" logout in a multi-connection session. In all other cases, the effect is "NA". Julian Satran Expires February 2003 277 iSCSI 5-August-02 15.Applicable only if this leading connection login is a session reinstatement. If that is not the case, this is "NA". 16.This operation affects all logged-in initiators. 18.Session failure is as defined in Section 4.3.6 Session continua- tion and failure. 19.This operation affects all logged-in initiators and the clearing effects are only applicable to the LU being reset. Julian Satran Expires February 2003 278 iSCSI 5-August-02 +-----+-----+-----+-----+-----+ |DC(1)|DD(2)|SS(3)|CS(4)|DS(5)| +---------------------+-----+-----+-----+-----+-----+ |connection failure |N |Y |N |N |N | +---------------------+-----+-----+-----+-----+-----+ |connection state |Y |NA |Y |N |NA | |timeout | | | | | | +---------------------+-----+-----+-----+-----+-----+ |session timeout/ |Y |Y |Y(7) |Y |NA | |closure/reinstatement| | | | | | +---------------------+-----+-----+-----+-----+-----+ |session continuation |N(11)|NA*12|NA |N |NA*13| +---------------------+-----+-----+-----+-----+-----+ |successful connection|Y |Y |Y |N |NA | |close Logout | | | | | | +---------------------+-----+-----+-----+-----+-----+ |session failure |N |Y |N |N |N | +---------------------+-----+-----+-----+-----+-----+ |successful recovery |Y |Y |Y |N |N | |Logout | | | | | | +---------------------+-----+-----+-----+-----+-----+ |failed Logout |N |Y(9) |N |N |N | +---------------------+-----+-----+-----+-----+-----+ |connection Login |NA |NA |N(8) |N(8) |NA | |(leading | | | | | | +---------------------+-----+-----+-----+-----+-----+ |connection Login |N(11)|NA*12|N(8) |N |NA*13| |(non-leading) | | | | | | +---------------------+-----+-----+-----+-----+-----+ |target cold reset |Y |Y |Y |Y(10)|NA | +---------------------+-----+-----+-----+-----+-----+ |target warm reset |Y |Y |N |N |NA | +---------------------+-----+-----+-----+-----+-----+ |LU reset |N |Y |N |N |N | +---------------------+-----+-----+-----+-----+-----+ |powercycle |Y |Y |Y |Y(10)|NA | +---------------------+-----+-----+-----+-----+-----+ 1.Discontiguous Commands - commands allegiant to the connection in question and waiting to be reordered in the iSCSI layer. All "Y"s in this column assume that the task causing the event (if indeed the event is the result of a task) is issued as an immediate command, because the discontiguities can be ahead of the task. Julian Satran Expires February 2003 279 iSCSI 5-August-02 2.Discontiguous Data - data PDUs received for the task in question and waiting to be reordered due to prior discontiguities in DataSN. 3.StatSN 4.CmdSN 5.DataSN 7.It clears the StatSN on all the connections. 8.This sequence number is instantiated on this event. 9.A logout failure drives the connection state machine to the CLEANUP_WAIT state, similar to the connection failure event. Hence, it has a similar effect on this and several other protocol aspects. 10.This is cleared by virtue of the fact that all sessions with all initiators are terminated. 11.This clearing effect is "Y" if it is a connection reinstatement. 12.This clearing effect is "Y" only if it is a connection reinstate- ment and the operational ErrorRecoveryLevel is 2. 13.This clearing effect is "N" only if it is a connection reinstate- ment and the operational ErrorRecoveryLevel is 2. F.2 Clearing effects on SCSI objects The only iSCSI protocol action that can effect clearing actions on SCSI objects is the "I_T nexus loss" notification (Section 4.3.5.1 Loss of Nexus notification). [SPC3] describes the clearing effects of this notification on a variety of SCSI attributes. In addition, SCSI standards documents (such as [SAM2] and [SBC]) define additional clearing actions that may take place for several SCSI objects on SCSI events such as LU resets and power-on resets. Note that because iSCSI defines target cold reset as protocol-equiva- lent to a target power-cycle, the iSCSI target cold reset must also be considered as the power-on reset event in interpreting the actions defined in the SCSI standards. Julian Satran Expires February 2003 280 iSCSI 5-August-02 When the iSCSI session is reconstructed (thus between the same SCSI ports with the same nexus identifier) establishing the same I_T nexus again, all SCSI objects that are defined to not clear on the "I_T nexus loss" notification event, such as persistent reservations, are automatically associated to this new session. Julian Satran Expires February 2003 281 iSCSI 5-August-02 Full Copyright Statement "Copyright (C) The Internet Society (date). All Rights Reserved. This document and translations of it may be copied and furnished to oth- ers, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this docu- ment itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of develop- ing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE." The IETF has been notified of intellectual property rights claimed in regard to some or all of the specification contained in this docu- ment. For more information consult the online list of claimed rights. Julian Satran Expires February 2003 282
Datatracker
Report a datatracker bug
draft-ietf-ips-iscsi-15
Internet-Draft
| Document | Document type |
This is an older version of an Internet-Draft that was ultimately published as RFC 3720.
Expired & archived
|
|
|---|---|---|---|
| Select version | |||
| Compare versions | |||
| Author | |||
| RFC stream |
|
||
| Other formats | |||
| Additional resources | Mailing list discussion |