Internet Small Computer System Interface (iSCSI) Corrections and Clarifications
RFC 5048

Network Working Group                                M. Chadalapaka, Ed.
Request for Comments: 5048                           Hewlett-Packard Co.
Updates: 3720                                               October 2007
Category: Standards Track

           Internet Small Computer System Interface (iSCSI)
                     Corrections and Clarifications

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Abstract

   The Internet Small Computer System Interface (iSCSI) is a SCSI
   transport protocol and maps the SCSI architecture and command sets
   onto TCP/IP.  RFC 3720 defines the iSCSI protocol.  This document
   compiles the clarifications to the original protocol definition in
   RFC 3720 to serve as a companion document for the iSCSI implementers.
   This document updates RFC 3720 and the text in this document
   supersedes the text in RFC 3720 when the two differ.

Table of Contents

   1. Introduction ....................................................3
   2. Definitions, Acronyms, and Document Summary .....................3
      2.1. Definitions ................................................3
      2.2. Acronyms ...................................................4
      2.3. Clarifications, Changes, and New Semantics .................5
   3. iSCSI Semantics for SCSI Tasks ..................................7
      3.1. Residual Handling ..........................................7
           3.1.1. Overview ............................................7
           3.1.2. SCSI REPORT LUNS and Residual Overflow ..............7
      3.2. R2T Ordering ...............................................9
      3.3. Model Assumptions for Response Ordering ....................9
           3.3.1. Model Description ..................................10
           3.3.2. iSCSI Semantics with the Interface Model ...........10
           3.3.3. Current List of Fenced Response Use Cases ..........11
   4. Task Management ................................................12
      4.1. Requests Affecting Multiple Tasks .........................12
           4.1.1. Scope of Affected Tasks ............................12
           4.1.2. Clarified Multi-Task Abort Semantics ...............13
           4.1.3. Updated Multi-Task Abort Semantics .................14

Chadalapaka                 Standards Track                     [Page 1]
RFC 5048          iSCSI Corrections and Clarifications      October 2007

           4.1.4. Affected Tasks Shared across RFC 3720 and
                  FastAbort Sessions .................................16
           4.1.5. Implementation Considerations ......................17
           4.1.6. Rationale behind the New Semantics .................17
   5. Discovery Semantics ............................................19
      5.1. Error Recovery for Discovery Sessions .....................19
      5.2. Reinstatement Semantics of Discovery Sessions .............19
           5.2.1. Unnamed Discovery Sessions .........................20
           5.2.2. Named Discovery Sessions ...........................20
      5.3. Target PDUs during Discovery ..............................20
   6. Negotiation and Others .........................................21
      6.1. TPGT Values ...............................................21
      6.2. SessionType Negotiation ...................................21
      6.3. Understanding NotUnderstood ...............................21
      6.4. Outstanding Negotiation Exchanges .........................22
   7. iSCSI Error Handling and Recovery ..............................22
      7.1. ITT .......................................................22
      7.2. Format Errors .............................................22
      7.3. Digest Errors .............................................22
      7.4. Message Error Checking ....................................23
   8. iSCSI PDUs .....................................................23
      8.1. Asynchronous Message ......................................23
      8.2. Reject ....................................................24
   9. Login/Text Operational Text Keys ...............................24
      9.1. TaskReporting .............................................24
   10. Security Considerations .......................................25
   11. IANA Considerations ...........................................26
      11.1. iSCSI-Related IANA Registries ............................26
      11.2. iSCSI Opcodes ............................................26