INTERNET DRAFT Pat R. Calhoun Category: Standards Track Sun Microsystems, Inc. Title: draft-calhoun-diameter-12.txt Allan C. Rubens Date: December 1999 Tut Systems, Inc. Haseeb Akhtar Nortel Networks Erik Guttman Sun Microsystems, Inc. DIAMETER Base Protocol Status of this Memo This document is an individual contribution for consideration by the AAA Working Group of the Internet Engineering Task Force. Comments should be submitted to the diameter@ipass.com mailing list. Distribution of this memo is unlimited. This document is an Internet-Draft and is in full conformance with all provisions 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 a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current 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. Copyright (C) The Internet Society 1999. All Rights Reserved. Abstract The DIAMETER base protocol is intended to provide a AAA framework for Calhoun et al. expires May 2000 [Page 1]
INTERNET DRAFT December 1999 Mobile-IP, NASREQ and ROAMOPS. This draft specifies the message format, transport, error reporting and security services to be used by all DIAMETER extensions and MUST be supported by all DIAMETER implementations. Table of Contents 1.0 Introduction 1.1 Requirements language 1.2 Terminology 2.0 Protocol Overview 2.1 Header Format 2.1.1 ZLB Message Format 2.2 AVP Format 2.2.1 AVP Header 2.2.2 Optional Header Elements 2.2.3 AVP Value Formats 2.2.4 DIAMETER Base Protocol AVPs 2.3 Mandatory AVPs 2.3.1 Command-Code AVP 2.3.2 Host-IP-Address AVP 2.3.3 Host-Name AVP 2.4 The art of AVP Tagging 2.5 State Machine 2.6 Device-Reboot-Ind (DRI) Command 2.6.1 Vendor-Name AVP 2.6.2 Firmware-Revision AVP 2.6.3 Reboot-Type AVP 2.6.4 Reboot-Time AVP 2.6.5 Extension-Id AVP 2.7 Device-Watchdog-Ind (DWI) Command 3.0 "User" Sessions 3.1 Session-Id AVP 3.2 Session-Timeout AVP 3.3 User-Name AVP 4.0 Reliable Transport 4.1 Flow Control 4.1.1 Receive-Window AVP 4.2 Peer failure recovery 5.0 Error Reporting 5.1 Message-Reject-Ind (MRI) Command 5.1.1 Failed-AVP AVP 5.2 Result-Code AVP 6.0 DIAMETER Message Routing 6.1 Message Proxying 6.1.1 Proxy-State AVP 6.1.2 Destination-NAI AVP Calhoun et al. expires May 2000 [Page 2]
INTERNET DRAFT December 1999 6.2 Message Redirection 6.2.1 Redirected-Host AVP 7.0 DIAMETER Message Security 7.1 Hop-by-Hop Security 7.1.1 Integrity-Check-Value AVP 7.1.2 Encrypted-Payload AVP 7.1.2.1 MD5 Payload Hiding 7.2 Nonce AVP 7.3 Timestamp AVP 8.0 IANA Considerations 8.1 AVP Attributes 8.2 Command Code AVP Values 8.3 Extension Identifier Values 8.4 Result-Code AVP Values 8.5 Integrity-Check-Value AVP Transform Values 8.6 Reboot-Type AVP Values 8.7 AVP Header Bits 9.0 Open Issues 10.0 DIAMETER protocol related configurable parameters 11.0 Security Considerations 12.0 References 13.0 Acknowledgements 14.0 Author's Addresses 15.0 Full Copyright Statement Calhoun et al. expires May 2000 [Page 3]
INTERNET DRAFT December 1999 1.0 Introduction The DIAMETER protocol allows peers to exchange a variety of messages. The base protocol provides the following facilities: - Delivery of AVPs (attribute value pairs) - Capabilities negotiation, as required in [20] - Error notification - Sequenced in-order reliable delivery of UDP datagram messages - Support for congestion control (receiver window), as required in [21] - Timely detection of failed or unresponsive peers, as required in [21, 22, 23] - Extensibility, through addition of new commands and AVPs, as required in [21] All data delivered by the protocol is in the form of an AVP. Some of these AVP values are used by the DIAMETER protocol itself, while others deliver data associated with particular applications which employ DIAMETER. AVPs may be added arbitrarily to DIAMETER messages, so long as the required AVPs are included and AVPs which are explicitly excluded are not included. AVPs are used by base DIAMETER protocol to support the following required features: - If application-level security is required, all messages MUST include an Integrity Check Vector (ICV). If the ICV is present, the message MUST also carry a timestamp and a nonce to aid in providing replay protection. - To carry user authentication information, for the purposes of enabling the DIAMETER server to authenticate the user. - To allow authorization information to be exchanged for a particular user's session between a DIAMETER client and server. - To exchange resource usage information, which MAY be used for accounting purposes, capacity planning, etc. The DIAMETER base protocol provides the minimum requirements needed for an AAA transport protocol, as required by NASREQ [21], Mobile IP [22, 23], and ROAMOPS [20]. The base protocol is not intended to be used by itself, and must be used with an application-specific extension, such as Mobile IP. The DIAMETER protocol was heavily inspired and builds upon the tradition of the RADIUS [1] protocol. Any node can initiate a request. In that sense, DIAMETER is a peer to peer protocol. In this document, a DIAMETER client is the device that normally initiates a request for authentication and/or authorization of a user. A DIAMETER server is the device that performs the actual authentication and/or authorization of the user based on some profile. A server MAY issue an unsolicited message to a client, but Calhoun et al. expires May 2000 [Page 4]
INTERNET DRAFT December 1999 this is typically not a request for authentication and/or authorization, but rather for something else, such as an accounting update. 1.1 Requirements language In this document, the key words "MAY", "MUST, "MUST NOT", "optional", "recommended", "SHOULD", and "SHOULD NOT", are to be interpreted as described in [13]. 1.2 Terminology Refer to [9] for terminology used in this document. 2.0 Protocol Overview The base DIAMETER protocol is never used on its own. It is always extended for a particular application. Four extensions to DIAMETER are defined by companion documents: NASREQ [7], Mobile IP [10], Accounting Extension [15], Strong Security [11]. These options are introduced in this document but specified elsewhere. Additional extensions to DIAMETER may be defined in the future (see Section 8.3). The base DIAMETER protocol concerns itself with capabilities negotiation, and how messages are sent, resent and how peers may eventually be abandoned. The base protocol also defines certain rules which apply to all exchanges of messages between DIAMETER peers. It is important to note that the base protocol provides an optional application-level security AVPs (Integrity-Check-Value) which MAY be used in absence of an underlying security protocol (e.g. IP Security). Communication between DIAMETER peers begins with one peer sending a message to another DIAMETER peer. The set of AVPs included in the message is determined by a particular application of or extension to DIAMETER. (We will refer to this as the DIAMETER extension). One AVP which is included in the initial communication is the Session-Id. The communicating party may accept or reject the request which contains a new Session-Id, or return Result-Code if the request cannot be processed. The behavior of the communicating peer depends on the DIAMETER extension employed. Exchanges of messages are either request/reply oriented, or in some Calhoun et al. expires May 2000 [Page 5]
INTERNET DRAFT December 1999 special cases, do not require replies. All such messages which do not require replies (or acknowledgments) have names which end with '-Ind' (short for Indication). All messages require a transport level acknowledgement, either through a Zero Length Body (ZLB), or by piggybacking an acknowledgement in a non-ZLB message. Communicating DIAMETER peers retain state relating to transport (sequence numbers and the like). This state information may be discarded when the communicating peer is determined to be unreachable. This occurs when the peer does not acknowledge receipt of a DIAMETER message that has been retransmitted a maximum number of times. The Device-Watchdog-Ind is used to pro-actively probe peers to ensure that communication is still possible. Freeing the transport state associated with a communication with a DIAMETER peer is entirely independent of freeing session state (associated with a Session-Id). The latter MUST only be done according to rules established in a particular extension/application of DIAMETER. DIAMETER extensions SHOULD define an explicit exchange of messages which allow a peer to inform the other party that a session has been terminated. 2.1 Header Format The base DIAMETER protocol is run over UDP port 1812. Implementations MAY send packets from any source port, but MUST be prepared to receive packets on port 1812. When a request is received, in order to send a reply, the source and destination ports in the reply are reversed. A given DIAMETER process SHOULD use the same port number to send all messages to aid in identifying which process sent a given message. More than one DIAMETER process MAY exist within a single host, so the sender's port number is needed to discriminate them. A summary of the DIAMETER data format is shown below. The fields are transmitted in network byte order. Calhoun et al. expires May 2000 [Page 6]
INTERNET DRAFT December 1999 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |RADIUS PCC=254|Flags|A|W| Ver | Message Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Identifier | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Next Send (Ns) | Next Received (Nr) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | AVPs ... +-+-+-+-+-+-+-+-+-+-+-+-+- RADIUS PCC The RADIUS Packet Compatibility Code (PCC) field is a one octet field which is used for backward compatibility with RADIUS and MUST be set to 254. In order to easily distinguish DIAMETER messages from RADIUS, the value of 254 has been reserved and allows implementations to support both protocols by using the first octet in the header. Flags The Message Flags field is five bits, and is used in order to identify any options. This field MUST be initialized to zero. The 'W' bit (Window-Present) is set when the Next Send (Ns) and Next Received (Nr) fields are present in the header. The 'A' bit is set to indicate that the message is an acknowledgement only (ZLB) and does not contain a Command-Code AVP following the header. Note that the Security AVPs, if required, MUST still be present within a ZLB. In the event that the DIAMETER protocol is implemented over a reliable transport, the 'W' and 'A' bits MUST NOT be set. Version This Version field MUST be set to 1 to indicate DIAMETER Version 1. Message Length The Message Length field is two octets and indicates the length of the DIAMETER message including the header fields. DIAMETER implementations MUST be ready to receive UDP packets of at least 8192 octets in length. Identifier The Identifier field is four octets, and aids in matching requests and replies. The sender MUST ensure that the identifier in a message is locally unique (to the sender) at any given time, and MAY attempt to ensure that the number is unique across reboots. Calhoun et al. expires May 2000 [Page 7]
INTERNET DRAFT December 1999 The identifier is normally a monotonically increasing number, whose start value was randomly generated. DIAMETER servers should consider a message to be unique by examining the source address, source port and Identifier field of the message. Next Send This field is present when the Window-Present bit is set in the header flags. The Next Send (Ns) is copied from the send sequence number state variable, Ss, at the time the message is transmitted. The variable Ss is incremented after copying into the header if the message is not a ZLB. Next Received This field is present when the Window-Present bit is set in the header flags. Nr is copied from the receive sequence number state variable, Sr, and indicates the sequence number, Ns, +1 of the highest (modulo 2^16) in-sequence message received. See section 4.0 for more information. AVPs AVPs is a method of encapsulating information relevant to the DIAMETER message. See section 2.2 for more information on AVPs. 2.1.1 ZLB Message Format Zero Length Body (ZLB) messages are used to explicitly acknowledge one or more DIAMETER message, and contain no additional Authentication, Authorization or Accounting related AVPs. ZLB messages must contain authentication AVPs, otherwise attacks could be mounted against DIAMETER nodes. The format of a ZLB message is as follows: <ZLB Message> ::= <DIAMETER Header> [<Timestamp AVP> <Nonce AVP> <Integrity-Check-Value AVP>] 2.2 AVP Format DIAMETER AVPs carry specific authentication, accounting and authorization information, security information as well as configuration details for the request and reply. Some AVPs MAY be listed more than once. The effect of this is AVP specific, and is specified in each case by the AVP description. Calhoun et al. expires May 2000 [Page 8]
INTERNET DRAFT December 1999 Each AVP of type 'string' and 'data' MUST be padded to align on a 32 bit boundary, while other AVP types align naturally. Zero bytes are added to the end of the AVP value till a word boundary is reached. The length of the padding is not reflected in the AVP Length field. 2.2.1 AVP Header The AVP format is shown below and MUST be sent in network byte order. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | AVP Code | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | AVP Length | Reserved |P|T|V|R|M| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Vendor ID (opt) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (opt) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data ... +-+-+-+-+-+-+-+-+ AVP Code The AVP Code identifies the attribute uniquely. If the Vendor- Specific bit is set, the AVP Code is allocated from the vendor's private address space. The first 256 AVP numbers are reserved for backward compatibility with RADIUS and are to be interpreted as per RADIUS [1]. AVP numbers 256 and above are used for DIAMETER, which are allocated by IANA (see section 8.1). AVP Length The AVP Length field is two octets, and indicates the length of this Attribute including the AVP Code, AVP Length, AVP Flags, Reserved, the Tag and Vendor ID fields if present and the AVP data. If a message is received with an Invalid attribute length, the message SHOULD be rejected. AVP Flags The AVP Flags field informs the DIAMETER host how each attribute must be handled. Note that subsequent DIAMETER extensions MAY define bits to be used within the AVP Header, and an unrecognized bit should be considered an error. The 'R' and the reserved bits should be set to 0 and ignored on receipt, while the 'P' bit is defined in [11]. Calhoun et al. expires May 2000 [Page 9]
INTERNET DRAFT December 1999 The 'M' Bit, known as the Mandatory bit, indicates whether support of the AVP is required. If an AVP is received with the 'M' bit enabled and the receiver does not support the AVP, the message MUST be rejected. AVPs without the 'M' bit enabled are informational only and a receiver that receives a message with such an AVP that is not supported MAY simply ignore the AVP. The 'V' bit, known as the Vendor-Specific bit, indicates whether the optional Vendor ID field is present in the AVP header. When set the AVP Code belongs to the specific vendor code address space. The 'T' bit, known as the Tag bit, is used to group sets of AVPs together. Grouping of AVPs is necessary when more than one AVP is needed to express a condition. If this bit is set, the optional Tag field will be present. Unless otherwise noted, AVPs will have the following default AVP Flags field settings: The 'M' bit MUST be set. The 'V' bit MUST NOT be set. The 'T' bit MAY be set. 2.2.2 Optional Header Elements The AVP Header consists of several optional fields. These fields are only present if their respective bit-flags are enabled. Vendor ID The Vendor ID field is present in the 'V' bit is set in the AVP Flags field. The optional four octet Vendor ID field contains the IANA assigned "SMI Network Management Private Enterprise Codes" [2] value, encoded in network byte order. Any vendor wishing to implement DIAMETER extensions MUST use their own Vendor ID along with private Attribute values, guaranteeing that they will not collide with any other vendor's extensions, nor with future IETF extensions. A vendor ID value of zero (0) corresponds to the IETF adopted AVP values, as managed by the IANA. Since the absence of the vendor ID field implies that the AVP in question is not vendor specific, implementations SHOULD not use the zero (0) vendor ID. Tag The Tag field is four octet in length and is intended to provide a means of grouping attributes in the same message which refer to the same set. If the Tag field is unused, the 'T' bit MUST NOT be set. Calhoun et al. expires May 2000 [Page 10]
INTERNET DRAFT December 1999 2.2.3 AVP Value Formats The Data field is zero or more octets and contains information specific to the Attribute. The format and length of the Data field is determined by the AVP Code and AVP Length fields. Note that messages which are larger than the path MTU will cause IP fragmentation and messages SHOULD be kept to that size wherever possible. In any case UDP limits messages to 2^16 bytes. The format of the value field MAY be one of seven data types. Data The data contains a variable length of arbitrary data. Unless otherwise noted, the AVP Length field MUST be set to at least 9. String The data contains a non-NULL terminated variable length string using the UTF-8 [24] character set. Unless otherwise noted, the AVP Length field MUST be set to at least 9. Address 32 bit (IPv4) [17] or 128 bit (IPv6) [16] address, most significant octet first. The format of the address (IPv4 or IPv6) is determined by the length. If the attribute value is an IPv4 address, the AVP Length field MUST be 12, otherwise the AVP Length field MUST be set to 24 for IPv6 addresses. Integer32 32 bit value, in network byte order. The AVP Length field MUST be set to 12. Integer64 64 bit value, in network byte order. The AVP Length field MUST be set to 16. Time 32 bit unsigned value, In network byte order, and contains the seconds since 00:00:00 GMT, January 1, 1900. The AVP Length field MUST be set to 12. Complex The complex data type is reserved for AVPs that includes multiple information fields, and therefore do not fit within any of the AVP types defined above. Complex AVPs MUST provide the data format, and the expected length of the AVP. Calhoun et al. expires May 2000 [Page 11]
INTERNET DRAFT December 1999 2.2.4 DIAMETER Base Protocol AVPs The following table describes the DIAMETER AVPs defined in the base protocol, their AVP Code values, types, possible flag values and whether the AVP MAY be encrypted. +---------------------+ | AVP Flag rules | |----+-----+----+-----|----+ AVP Section Value | | |SHLD| MUST|Encr| Attribute Name Code Defined Type |MUST| MAY | NOT| NOT|Cand| -----------------------------------------|----+-----+----+-----|----| User-Name 1 3.3 String | | | | | Y | Host-IP-Address 4 2.3.2 Address | M | | | T,V | N | Session-Timeout 27 3.2 Integer32| | | | | Y | Host-Name 32 2.3.3 String | M | | | T,V | N | Proxy-State 33 6.1.1 Complex | M | | | T,V | N | Command-Code 256 2.3.1 Integer32| M | V | | T | N | Extension-Id 258 2.6.5 Integer32| | | | | Y | Integrity-Check 259 7.1.1 Complex | | | | | N | -Value | | | | | | Encrypted- 260 7.1.2 Complex | | | | | N | Payload | | | | | | Nonce 261 7.2 Data | | | | | N | Timestamp 262 7.3 Time | | | | | N | Session-Id 263 3.3 Data | | | | | Y | Vendor-Name 266 2.6.1 String | | | |T,V,M| Y | Firmware 267 2.6.2 Integer32| | | |T,V,M| Y | -Revision | | | | | | Result-Code 268 5.2 Complex | | | | | N | Destination-NAI 269 6.1.2 String | | | | | Y | Reboot-Type 271 2.6.3 Integer32| | | | | N | Reboot-Time 272 2.6.4 Integer32| | | | | N | Failed-AVP 279 5.1.1 Data | | | | | Y | Receive-Window 277 4.1.1 Integer32| | | | | Y | Redirect-Host 278 6.2.1 Address | | | | | Y | 2.2.5 Standard DIAMETER Extension AVPs The following AVPs are defined in standard DIAMETER extensions. AVP Name Code Ref AVP Name Code Ref AVP Name Code Ref ------------- ---- --- ------------ ---- --- ------------ ---- ---- User-Password 2 [7] Framed- 38 [7] MN-FA- 322 [10] CHAP-Password 3 [7] Appletalk- Challenge- NAS-Port 5 [7] Network Length Service-Type 6 [7] Framed- 39 [7] MN-FA-Response 323 [10] Calhoun et al. expires May 2000 [Page 12]
INTERNET DRAFT December 1999 Framed-Protocol 7 [7] Appletalk- Mobile-Node- 333 [10] Framed-IP- 8 [7] Zone Address Address CHAP-Challenge 60 [7] Home-Agent- 334 [10] Framed-IP- 9 [7] NAS-Port-Type 61 [7] Address Netmask Port-Limit 62 [7] Previous-FA- 335 [10] Framed-Routing 10 [7] Login-LAT-Port 63 [7] NAI Filter-Id 11 [7] Tunnel-Type 64 [7] MN-AAA-SPI 336 [10] Framed-MTU 12 [7] Tunnel-Medium- 65 [7] Foreign-Home- 337 [10] Framed- 13 [7] Type Agent- Compression Tunnel-Client- 66 [7] Available Login-IP-Host 14 [7] Endpoint Filter-Rule 400 [7] Login-Service 15 [7] Tunnel-Server- 67 [7] Request-Type 401 [7] Login-TCP-Port 16 [7] Endpoint EAP-Payload 402 [7] Reply-Message 18 [7] Tunnel-Password 69 [7] Accounting- 480 [15] Callback-Number 19 [7] Tunnel-Private- 81 [7] Record-Type Callback-Id 20 [7] Group-ID ADIF-Record 481 [15] Framed-IP-Route 22 [7] Tunnel- 82 [7] Accounting- 482 [15] Framed-IPX- 23 [7] Assignment-ID Interim- Route Tunnel- 83 [7] Interval Idle-Timeout 28 [7] Preference Accounting- 483 [15] Called-Station- 30 [7] Tunnel-Client- 90 [7] Delivery- Id Auth-ID Interval Calling- 31 [7] Tunnel-Server- 91 [7] Accounting- 484 [15] Station-Id Auth-ID Delivery- Login-LAT- 34 [7] CMS-Data 310 [11] Max-Delay Service MIP- 320 [10] Accounting- 485 [15] Login-LAT-Node 35 [7] Registration- Record- Login-LAT-Group 36 [7] Request Number Framed- 37 [7] MIP- 321 [10] Appletalk- Registration- Link Reply 2.3 Mandatory AVPs This section defines the DIAMETER AVPs that MUST be present in all DIAMETER messages, with the exception of the ZLB. 2.3.1 Command-Code AVP The Command-Code AVP (AVP Code 256) is of type Integer32 and MUST be the first AVP following the DIAMETER header (except for ZLB messages). A DIAMETER message MUST have at most one Command-Code AVP, and it is used in order to communicate the command associated with the message. The Command Code 32-bit address space is managed by IANA (see section 8.2). Calhoun et al. expires May 2000 [Page 13]
INTERNET DRAFT December 1999 The following Command Codes are currently defined in the DIAMETER protocol: Command-Name Abbrev. Code Reference -------------------------------------------------------- Device-Reboot-Ind DRI 257 2.6 Device-Watchdog-Ind DWI 258 2.7 Message-Reject-Ind MRI 259 5.1 AA-Mobile-Node-Request AMR 260 [10] AA-Mobile-Node-Answer AMA 261 [10] Home-Agent-MIP-Request HAR 262 [10] Home-Agent-MIP-Answer HAA 263 [10] Mobile-Node-Terminate-Ind MTI 264 [10] AA-Request AAR 265 [7] AA-Answer AAA 266 [7] AA-Challenge-Ind ACI 267 [7] DIAMETER-EAP-Request DER 268 [7] DIAMETER-EAP-Answer DEA 269 [7] DIAMETER-EAP-Ind DEI 270 [7] Accounting-Request ACR 271 [15] Accounting-Answer ACA 272 [15] Accounting-Poll-Ind ACP 273 [15] 2.3.2 Host-IP-Address AVP The Host-IP-Address AVP (AVP Code 4) [1] is of type Address and is used to inform a DIAMETER peer of the sender's IP address. All DIAMETER messages, except for ZLBs, MUST include either the Host-IP- Address or the Host-Name (section 2.3.3) AVPs, or both. 2.3.3 Host-Name AVP The Host-Name AVP (AVP Code 32) [1] is of type String, and is used to inform a DIAMETER peer of the sender's identity. All DIAMETER messages, except for ZLBs, MUST include either the Host-IP-Address or the Host-Name (section 2.3.2) AVPs, or both. This AVP contains the host name of the originator of the DIAMETER message that MUST follow the NAI [8] naming conventions. 2.4 The art of AVP Tagging The AVP Header provides the 'T' bit, which is used to group AVPs together. All AVPs with the same tag value are part of the same "group", and there are no guidelines or rules on which tag values are Calhoun et al. expires May 2000 [Page 14]
INTERNET DRAFT December 1999 used. The base protocol defines the Redirect-Host AVP (see section 6.2.1), and [11] defines how the associated certificate MAY be carried within the DIAMETER protocol. This allows a single request to include information about more than one host. In the case where multiple AVPs are needed to indicate a specific authorization "rule" tagging is appropriate. In some cases, more than one such rule MAY be present, and the tagging mechanism allows the sets of AVPs to be easily grouped. Some Command Codes require certain AVPs to be tagged and use the '(' and ')' characters in the BNF command definition, such as: <Device-Reboot-Ind> ::= <DIAMETER Header> <Command Code AVP> (<Tagged AVP #1> <Tagged AVP #2> <Tagged AVP n>) 2.5 State Machine A DIAMETER node initially considers all known peers to be in the closed state, and should not process any DIAMETER message with the exception of the Device-Reboot-Ind (DRI). Once the DIAMETER peer is set to the open state, any DIAMETER message may be accepted and processed. This section provides the DIAMETER base protocol state machine. If at any time no transport level acknowledgement is received and the message was retransmitted the maximum number of times, the session with the peer MUST be closed, and all associated state with the peer MUST be freed. State Event Action New State ----- ----- ------ --------- closed Local Open send DRI wait-ack1 Request closed receive DRI send ACK wait-ack2 send DRI closed receive invalid cleanup closed DRI wait-ack1 receive ACK accept Incoming wait-ack1 Messages wait-ack1 receive DRI send ACK open Calhoun et al. expires May 2000 [Page 15]
INTERNET DRAFT December 1999 Accept Incoming Messages wait-ack1 no ACK received cleanup closed wait-ack2 received ACK Accept Incoming open Messages wait-ack2 no ACK received cleanup closed open receive DRI send ACK wait-ack2 Rebooted send DRI open receive DRI cleanup closed Imminent-Reboot open receive DWI send ACK open open receive other send ACK open messages open inactivity period send DWI open hits watchdog timer open no ACK received cleanup closed 2.6 Device-Reboot-Ind (DRI) Command A DIAMETER device sends the Device-Reboot-Ind message, by including the Command-Code AVP with a value of 257, to inform a peer either of an upcoming reboot, or that it has just rebooted. The Reboot-Type AVP MUST be present and indicates the type of reboot associated with this command. Note that a DIAMETER device should only send this message when it is able to receive network traffic. The receiver of a DRI message with the Reboot-Type AVP set to REBOOT_IMMINENT SHOULD make an attempt to send packets to an alternate peer, if one is available. The optional Reboot-Time AVP will contain an estimate of how long before the peer will be ready to re-establish communication. In the case of a software implementation (server) running on a general purpose operating system, the Reboot- Time AVP will probably not be present since it is possible that the DIAMETER server has been stopped and it is not possible to know how long before (and if) it will be restarted. Calhoun et al. expires May 2000 [Page 16]
INTERNET DRAFT December 1999 The DRI message is also used for capabilities negotiation, such as the supported protocol version number, and the locally supported extensions. The receiver uses the extensions advertised in order to determine whether it SHOULD send certain application-specific DIAMETER commands. A DIAMETER node MUST retain the supported extensions in order to ensure that unrecognized commands and/or AVPs are not sent to a peer. Note that in a proxy environment, it is still possible for this problem to occur, and the DIAMETER base protocol provides this error reporting message. Upon reboot, the host MUST issue a DRI message with the Reboot-Type AVP set to REBOOTED to all configured peers. If a peer is no longer reachable, a DIAMETER device SHOULD periodically transmit a DRI until an acknowledgement is received. The retransmission timer SHOULD be different from the retransmission timer used when communication has been established, and SHOULD be configurable. Upon receipt of this message the peer's Ss and Sr variables MUST be reset. It is possible for this message to be received outside the window (Ns and Nr set to zero) when it follows a reboot. The DIAMETER Reboot-Ind message does not require a reply. The message is acknowledged using DIAMETER's reliable transport. See [25] for more information. Message Format <Device-Reboot-Ind> ::= <DIAMETER Header> <Command Code AVP = 257> {<Host-IP-Address AVP> || <Host-Name AVP>} <Vendor-Name AVP> <Extension-Id AVPs> <Reboot-Type AVP> [<Reboot-Time AVP>] [<Receive-Window AVP>] [<Firmware-Revision AVP>] [<Timestamp AVP> <Nonce AVP> <Integrity-Check-Value AVP>] 2.6.1 Vendor-Name AVP The Vendor-Name AVP (AVP Code 266) is of type String and is used to inform a DIAMETER peer of the Vendor Name of the DIAMETER device. This MAY be used in order to know which vendor specific attributes may be sent to the peer. It is also envisioned that the combination Calhoun et al. expires May 2000 [Page 17]
INTERNET DRAFT December 1999 of the Vendor-Name and the Firmware-Revision (section 2.6.2) AVPs MAY provide very useful debugging information. 2.6.2 Firmware-Revision AVP The Firmware-Revision AVP (AVP Code 267) is of type Integer32 and is used to inform a DIAMETER peer of the firmware revision of the issuing device. For devices that do not have a firmware revision (general purpose computers running DIAMETER software modules, for instance), the revision of the DIAMETER software module may be reported instead. 2.6.3 Reboot-Type AVP The Reboot-Type AVP (AVP Code 271) is of type Integer32 and MUST be present in the Device-Reboot-Indication message. This AVP contains an indication of the type of reboot that has or will occur. The following values are currently supported: REBOOT_IMMINENT 1 When the Reboot-Type AVP is set to this value it is an indication that the DIAMETER peer is about to reboot and should not be sent any additional DIAMETER messages after the acknowledgement for this Device-Reboot-Ind message. REBOOTED 2 When the Reboot-Type AVP is set to this value it is an indication that the DIAMETER peer has recently rebooted and is ready to accept new DIAMETER messages. 2.6.4 Reboot-Time AVP The Reboot-Time AVP (AVP Code 272) is of type Integer32 and MAY be present in the DRI. The value of this AVP indicates the number of seconds before the issuer expects to be ready to receive new DIAMETER messages. This AVP MUST only be present when the Reboot-Type AVP is set to REBOOT_IMMINENT. The value indicated by this AVP should be used as an estimate and is not a hard rule. 2.6.5 Extension-Id AVP The Extension-Id AVP (AVP Code 258) is of type Integer32 and is used in order to identify a specific DIAMETER extension. This AVP is used Calhoun et al. expires May 2000 [Page 18]
INTERNET DRAFT December 1999 in the Device-Reboot-Ind command in order to inform the peer what extensions are locally supported. Each DIAMETER extension draft MUST have an Extension-Id assigned to it by the IANA (see section 8.3). The base protocol does not require an Extension-Id since its support is mandatory. There MAY be more than one Extension-Id AVP within a DIAMETER Device-Reboot-Ind message. The following values are recognized: NASREQ 1 [7] Strong Security 2 [11] Mobile-IP 4 [10] Accounting 5 [15] 2.7 Device-Watchdog-Ind (DWI) Command The Device-Watchdog-Ind (DWI), indicated by the Command-Code AVP set to 258, is OPTIONAL and is used as a keepalive mechanism between two DIAMETER peers. If implemented, it SHOULD be sent during after a configurable period of inactivity. Communicating peers are not required to have the same DWI timer values set, as each entity MAY have different requirements. A DIAMETER node MAY use this mechanism to ensure that fail-over to an alternate server occurs in the absence of AAA traffic. This pro- active approach may minimize the possible latency involved in the fail-over that would otherwise occur. The lower the timer value is set to, the quicker a host will pro- actively detect that a peer is no longer reachable. However, the timer SHOULD NOT be set to a value that is considered too low (e.g. 2 seconds), since it will generate considerable traffic. The DIAMETER Device-Watchdog-Ind message does not require a reply. The message is acknowledged using DIAMETER's reliable transport. See [25 for more information. Message Format <Device-Watchdog-Ind> ::= <DIAMETER Header> <Command Code AVP = 258> {<Host-IP-Address AVP> || <Host-Name AVP> } [<Timestamp AVP> <Nonce AVP> <Integrity-Check-Value AVP>] Calhoun et al. expires May 2000 [Page 19]
INTERNET DRAFT December 1999 3.0 "User" Sessions When a user requests access to the network, a DIAMETER client issues an authentication and authorization request to its local server. The request contains a Session-Id AVP, which is used in subsequent messages (e.g. subsequent authorization, accounting, etc) relating to the user's session. The Session-Id AVP is a means for the client and servers to correlate a DIAMETER message with a user session. When a DIAMETER server authorizes a user to use network resources, it SHOULD add the Session-Timeout AVP to the response. The Session- Timeout AVP defines the maximum amount of time a user MAY make use of the resources before another authorization request is to be transmitted to the server. If the server does not receive another authorization request before the timeout occurs, it SHOULD release any state information related to the user's session. Note that the Session-Timeout AVP implies how long the DIAMETER server is willing to pay for the services rendered, therefore a DIAMETER client SHOULD NOT expect payment for services rendered past the session expiration time. The base protocol does not include any authorization request messages, since these are largely application-specific and are defined in a DIAMETER protocol extension document. Such extensions SHOULD provide a message that allows a client to inform a server that the user's session has been released. This would enable the server to free state information instead of having to wait for the timeout to occur. 3.1 Session-Id AVP The Session-Id AVP (AVP Code 263) is of type Data and is used to identify a specific session (see section 3.0). All messages pertaining to a specific session MUST include only one Session-Id AVP and the same value MUST be used throughout the life of a session. When present, the Session-Id SHOULD appear immediately following the Command-Code AVP. For messages that do not pertain to a specific session, multiple Session-Id AVPs MAY be present as long as the 'T' bit is set. The Session-Id MUST be globally unique at any given time since it is used by the server to identify the session (or flow). The format of the session identifier SHOULD be as follows: <Sender's IP Address><sender's port number> <monotonically increasing 32 bit value><optional value> Calhoun et al. expires May 2000 [Page 20]
INTERNET DRAFT December 1999 The monotonically increasing 32 bit value SHOULD NOT start at zero upon reboot, but rather start at a random value. This will minimize the possibility of overlapping Session-Ids after a reboot. Alternatively, an implementation MAY keep track of the increasing value in non-volatile memory. The optional value is implementation specific but may include a modem's device Id, a layer 2 address, timestamp, etc. The session Id is created by the DIAMETER device initiating the session, which in most cases is done by the client. Note that a Session-Id MAY be used by more than one extension (e.g. authentication for a specific service and accounting, both of which have separate extensions). 3.2 Session-Timeout AVP The Session-Timeout AVP (AVP Code 27) [1] is of type Integer32 and contains the maximum number of seconds of service to be provided to the user before termination of the session. A value of zero means that this session has an unlimited number of seconds before termination. This AVP MAY be provided by the client as a hint of the maximum duration that it is willing to accept. However, the server DOES NOT have to observe the hint and MAY return any value. A value of zero provided by a client DOES NOT imply that service is being terminated. 3.3 User-Name AVP The User-Name AVP (AVP Code 1) [1] is of type String and contains the User-Name in a format consistent with the NAI specification [8]. All DIAMETER systems SHOULD support usernames of at least 72 octets in length. 4.0 Reliable Transport This section provides a detailed overview of how DIAMETER is reliably transported over UDP. DIAMETER provides its own reliable transport due to its unique requirements, which include: - Rapid discovery of the failure of a communicating peer. - Transactions of few messages will be the norm, so the TCP slow start algorithm is not appropriate. - The retransmission scheme required is more aggressive than TCP provides. Calhoun et al. expires May 2000 [Page 21]
INTERNET DRAFT December 1999 4.1 Flow Control The DIAMETER header contains two fields used for reliable transport: Nr (Next Received) and Ns (Next Send). The sequence number state for each peer is represented (for clarity of discussion) as Sr (the next in-sequence message expected to be received) and Ss (the next in- sequence message to be sent). Sr and Ss are initialized to 0. The sequence number is a free ranging counter modulo 65536. For purposes of detecting duplication, a received sequence value is considered less than or equal to the last received value if its value lies in the range of the last value and its 32767 successor values. For example if the last received sequence number was 15, the packets received with Ns values in the range 32783..65535, or 0..15 would be considered duplicates. Duplicate messages are silently discarded. ZLB messages are used to acknowledge DIAMETER messages to the communicating peer. Each subsequent non-ZLB message is sent with a sequence number incremented by one (modulo 2^16). The following rules apply: - When a non-ZLB message is received with a Ns value which matches the peer's Sr value, Sr is incremented by one. Sr is not modified if a message is received with a Ns value greater than the current Sr value. - In messages which are sent to a peer, Nr is set to reflect one higher than the Ns value of the highest (module 2^16) in-order message received from the peer. - Every time a peer sends a non-ZLB message, it sends the message with Ns set to the current value of Ss. The value of Ss for that peer is then incremented by one (modulo 2^16). - Every time a peer receives an in-order non-ZLB message, the receiving peer must increment its Sr value. The peer MUST acknowledge the message, either by sending a ZLB message with the updated Nr value, or by piggybacking the acknowledgement in any outgoing message sent to the communicating peer. In this piggybacked message, the Nr field will be set to its updated value. The implementation guidelines [25] defines an OPTIONAL algorithm for delaying acknowledgments, to wait for outgoing messages to piggyback acknowledgements on. - Messages which are sent MUST be queued and retransmitted till the peer sends an acknowledgement. Messages SHOULD be retransmitted at least three times. The implmentation guidelines specification [25] recommends a retransmission timer Calhoun et al. expires May 2000 [Page 22]
INTERNET DRAFT December 1999 algorithm. Retransmitted messages SHOULD include the current value of Sr in the Nr field. An implementation MAY choose not to update Nr field (and Timestamp AVP) for retransmitted messages, in order to avoid having to perform another hash in the Integrity-Check- Value AVP. The message identifier in the retransmitted message MUST NOT be changed. A DIAMETER implementation MAY queue out of order DIAMETER messages for subsequent processing. The receive window is the maximum number of unacknowledged packets that are to be outstanding to a DIAMETER peer. When transmitting packets, a DIAMETER peer must obey the receive window size offered by its peer. The default window size is 7. Once the number of unacknowledged messages equals the window size, the window is 'closed.' Previously transmitted packets may be retransmitted when the peer's window is closed. A peer MAY explicitly specify its window size in the Device-Reboot-Ind message in the Receive-Window AVP. A peer MAY return a Nr value in a ZLB or piggybacked in a non-ZLB message which is less than the latest Sr value, due to congestion. Returning a value in Nr of the first value in the window will have the effect of preventing the communicating peer from sending any new messages. See [25] for some examples of how sequence numbers progress. 4.1.1 Receive-Window AVP The Receive-Window AVP (AVP Code 277) is of type Integer32 and contains the maximum number of outstanding unacknowledged messages that it is willing to accept for a given peer. Once the number of unacknowledged messages has reached this number, the receive window is considered closed. The default value for the receive window is 7, and SHOULD be configurable. A simple implementation that does not require a high number of transactions per second MAY send a Receive- Window AVP set to one (1). A node MUST stop sending messages when it detects that the number of unacknowledged messages is equal to the peer's receive window size. 4.2 Peer failure recovery A DIAMETER message with the Command-Code AVP set to Device-Reboot-Ind Calhoun et al. expires May 2000 [Page 23]
INTERNET DRAFT December 1999 and the Ns and Nr values set to zero (0) indicates that the peer has rebooted. This message MUST be recognized and supported by a DIAMETER implementation. When this event occurs, the Ss and Sr values must be reset and the retransmission queue MUST be cleared. Since the protocol requires that all new messages include a random identifier in the protocol header, a Device-Reboot-Ind that is received with the same identifier as the last processed Device-Reboot-Ind is considered a retransmission and SHOULD NOT change the peer's state to closed. Messages other than the Device-Reboot-Ind MUST NOT be sent to the peer until both the acknowledgement for the transmitted Device- Reboot-Ind AND the peer's Device-Reboot-Ind have been received. When both of these have been received, the peer is considered to be in the active state. 5.0 Error Reporting There are five different types of errors within DIAMETER. The first being where a DIAMETER message is poorly formatted and unrecognizable, indicated below by "Bad Message". This error condition applies if a received message creates a fatal error (e.g. fails transport level authentication, cannot be parsed, etc). The second case involves receiving a Command-Code AVP that is not supported, which is shown below by "Unknown Command". The third case is where an AVP is received, marked mandatory and is unknown by the receiver, which is labeled below as "Unknown AVP". This fourth case involves receiving a message with a known AVP, yet the value is either unknown or illegal, which is shown below as "Bad Value". The last case occurs when an error occurs while processing a specific extension command, which is not related to the message format and is labeled "Extension Error" below. Error Type Ignore Message Send Extension Message-Reject-Ind Response + Result-Code Bad Message X Unknown Command X Unknown AVP X Bad Value X Extension Error X "Ignore Message" indicates that the message is simply dropped. The "Message-Reject-Ind" indicates that a Message-Reject-Ind message MUST be sent to the peer as described in the appropriate section. The "Extension Response + Result-Code" indicates that the appropriate Calhoun et al. expires May 2000 [Page 24]
INTERNET DRAFT December 1999 Response to the message MUST be sent with the Result-Code AVP set to a value that enables the peer to understand the nature of the problem. 5.1 Message-Reject-Ind (MRI) Command The Message-Reject-Ind (MRI), indicated by the Command-Code AVP set to 256, provides a generic means of completing transactions by indicating errors in the messages that initiated them. The Message- Reject-Ind command is a possible response to any DIAMETER command. Some DIAMETER commands MAY expect more specialized error messages, depending on the error type. The Message-Reject-Ind message MUST contain the same identification in the header and include the Session-Id if it was present in the original message that it is responding to, even if the identification is erroneous. The receiver of a Message-Reject-Ind SHOULD examine the Result-Code AVP provided before processing the identification, in order to handle the latter appropriately. Message Format The structure of the Message-Reject-Ind message is defined as follows: <Message-Reject-Ind message> ::= <DIAMETER Header> <Command-Code AVP = 256> <Host-IP-Address AVP> [<Host-Name AVP>] [<Session-Id AVP>] <Result-Code AVP> <Failed-AVP AVP> [<Timestamp AVP> <Nonce AVP> <Integrity-Check-Value AVP>] where the Identifier value in the message header and optionally the Session-Id AVP are copied from the message being rejected. The Result-Code AVP indicate the nature of the error causing rejection, and the Failed-AVP AVP provides some minimal debugging data by indicating a specific AVP type which caused the problem. See the description of the Result-Code AVP for indication of when the Failed-AVP AVP MUST be present in the message. See [25] for more information. 5.1.1 Failed-AVP AVP Calhoun et al. expires May 2000 [Page 25]
INTERNET DRAFT December 1999 The Failed-AVP AVP (AVP Code 279) is of type Data and provides debugging information in cases where a request is rejected or not fully processed due to erroneous information in a specific AVP. The value of the Result-Code AVP will provide information on the reason for the Failed-AVP AVP. A DIAMETER message MAY contain one or more Failed-AVP, each containing a complete AVP that could not be processed successfully. The possible reasons for this AVP are the presence of an improperly constructed AVP, an unsupported or unrecognized AVP or an invalid AVP value (e.g. unknown Command-Code AVP). 5.2 Result-Code AVP The Result-Code AVP (AVP Code 268) is of type Complex and indicates whether a particular request was completed successfully or whether an error occurred. All DIAMETER messages of type *-Response or *-Answer MUST include one Result-Code AVP. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ AVP Header (AVP Code = 268) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Result Code | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | String ... +-+-+-+-+-+-+-+-+ The Result Code field contains an IANA-managed 32-bit address space representing errors. The String field contains an OPTIONAL string field containing a human readable error message. The base protocol defines the following error codes, and others MAY be defined in separate DIAMETER extensions: DIAMETER_SUCCESS 0 The Request was successfully completed. DIAMETER_FAILURE 1 The Request was not successfully completed for an unspecified reason. A DIAMETER Message-Reject message returning this result SHOULD whenever possible also contain one or more Failed-AVP AVPs indicating the attributes which caused the failure. DIAMETER_POOR_REQUEST 2 Calhoun et al. expires May 2000 [Page 26]
INTERNET DRAFT December 1999 The Request was poorly constructed. DIAMETER_INVALID_AUTH 3 The Request did not contain a valid Integrity-Check-Value or CMS-Data [11] AVP. DIAMETER_UNKNOWN_SESSION_ID 4 The Request contained an unknown Session-Id. This error is sent only due to conditions that arise due to command messages in DIAMETER extensions, the base protocol does not include command codes that require the Session-Id AVP. DIAMETER_USER_UNKNOWN 5 A request was received for a user that is unknown, therefore authentication failed. This error is sent only due to conditions that arise due to command messages in DIAMETER extensions, the base protocol does not include command codes that require the User-Name AVP. DIAMETER_COMMAND_UNSUPPORTED 6 The Request contained a Command-Code AVP that the receiver did not recognize or support. The Message-Reject-Ind message MUST also contain a Failed-AVP AVP containing the unrecognized Command-Code AVP. DIAMETER_TIMEOUT 7 This error MAY be returned if a request has been received that has a Timestamp AVP that is older than the maximum age that the communicating peer is willing to accept. DIAMETER_AVP_UNSUPPORTED 8 The peer received a message that contained an AVP that is not recognized or supported and was marked with the Mandatory bit. A Message-Reject-Ind message with this error MUST contain one or more Failed-AVP AVP containing the AVPs that caused the failure. DIAMETER_REDIRECT_INDICATION 9 A proxy or broker has determined that the request could not be satisfied locally and the initiator of the request should direct the request directly to the server, whose contact information has been added to the response. This error code MUST NOT be sent in a Message-Reject-Ind message. DIAMETER_DOMAIN_NOT_SERVED 10 A proxy or broker has determined that it is unable to forward the request or provide redirect information since the realm portion of the NAI requested is unknown. Calhoun et al. expires May 2000 [Page 27]
INTERNET DRAFT December 1999 DIAMETER_UNSUPPORTED_TRANSFORM 11 A message was received that included an Integrity-Check-Value or CMS-Data AVP [11] that made use of an unsupported transform. DIAMETER_AUTHENTICATION_REJECTED 12 The authentication process for the user failed, most likely due to an invalid password used by the user. DIAMETER_AUTHORIZATION_REJECTED 13 A request was received for which the user could not be authorized. This error could occur when the user has already expended allowed resources, or if the service requested is not permitted to the user. DIAMETER_INVALID_AVP_VALUE 14 The request contained an AVP with an invalid value in its data portion. A DIAMETER message with this result code MUST include the offending AVPs within a Failed-AVP AVP. DIAMETER_MISSING_AVP 15 The request did not contain an AVP which the Command Code requires be present. If this result code is sent, a Failed-AVP AVP should be included in the Message-Reject-Ind message. The AVP 'Data' in the Failed-AVP has its AVP Code set to the value of the missing and required AVP, but does not include any data of its own. 5.2.1 Additional Error Codes The following additional result codes are defined by standard extensions to the DIAMETER protocol. DIAMETER_ERROR_BAD_KEY 16 [10] DIAMETER_ERROR_BAD_HOME_ADDRESS 17 [10] DIAMETER_ERROR_TOO_BUSY 18 [10] DIAMETER_ERROR_MIP_REPLY_FAILURE 19 [10] DIAMETER_INVALID_CMS_DATA 20 [11] 6.0 DIAMETER Message Routing The DIAMETER base protocol supports two basic message routing methods; proxying and brokering. A DIAMETER proxy is a server that simply forwards the request based on the user's identity, or through some other means. A DIAMETER broker is a server that provides redirect services, allowing all servers in a roaming consortium to interact directly. Calhoun et al. expires May 2000 [Page 28]
INTERNET DRAFT December 1999 6.1 Message Proxying A DIAMETER proxy is a server that provides message forwarding functions to other DIAMETER Servers. Proxies are typically used when a hierarchical DIAMETER network is deployed, where some DIAMETER servers can authenticate and authorize a set of users. Such an example is a roaming consortium, where each ISP has a user base, which they can authenticate and authorize. It is important to note that proxy servers MUST NOT attempt to re-order AVPs in a DIAMETER message. The example provided in figure 1 shows a request issued by DIA1, requesting authentication and authorization for a user that belongs to DIA3's network. When DIA1 receives the request from the access device (e.g. NAS), it checks whether the Destination-NAI AVP is present, which MUST be in a format consistent with the NAI [8] specification. If the Destination-NAI is not present, the server MUST use the information found in the User-Name AVP. The NAI has a format of user@realm, and DIAMETER servers typically have a list of locally supported realms, and MAY have a list of externally supported realms with associated DIAMETER servers. DIAMETER servers that interface with brokers SHOULD allow for a "default" destination for all requests received that are not locally configured. In the example below, DIA1 looks up the user's realm, and determines that the request is to be forwarded to DIA2. When DIA2 receives the request, it MAY decide that some state information needs to be kept in order to process the response in a particular fashion. An example would be that DIA2 determines that certain authorization information is to be added to the response, when received. (Request) (Request) (User-Name=joe@abc.com) (User-Name=joe@abc.com) (Host-Name=DIA1@nmo.net) (Host-Name=DIA1@nmo.net) (Proxy-State=x) (Proxy-State=y) +------+ ------> +------+ ------> +------+ | | | | | | | DIA1 +-------------------+ DIA2 +-------------------+ DIA3 | | | | | | | +------+ <------ +------+ <------ +------+ (Response) (Response) (User-Name=joe@abc.com) (User-Name=joe@abc.com) (Dest-NAI=DIA1@mno.net) (Dest-NAI=DIA1@mno.net) (Proxy-State=x) (Proxy-State=y) mno.net xyz.com abc.com Figure 1: DIAMETER Proxying Calhoun et al. expires May 2000 [Page 29]
INTERNET DRAFT December 1999 There are two methods that MAY be implemented by DIAMETER servers in order to keep per-request state information. 1. DIA2 MAY maintain a state control block, and using the session-Id and possibly the Identifier in the header, can match the request with the response. The state control block MAY include AVPs that need to be added to the corresponding response, or any additional policy decisions that will need to be done when the response is received. 2. DIA2 MAY add a Proxy-State AVP (see section 6.1.1), which can contain ANY information that will be needed when the corresponding response is received. A DIAMETER message MUST only include one Proxy-State AVP, so if a new Proxy-State AVP is added, the old one MUST be removed. The new Proxy-State AVP MAY include AVPs that are to be added to the response, the existing Proxy-State AVP, etc. Once DIA2 has completed processing the request, it forwards the request to DIA3 following the same procedures defined for DIA1. When DIA3 receives the request, and it determines that the request is to be processed locally, it authenticates and authorizes the user. DIA3 MUST add the Destination-NAI AVP, with the same contents as the Host-Name AVP that was found in the corresponding request. If the request contained a Proxy- State AVP, the same AVP MUST be present in the response. When DIA2 receives the response from DIA3, it MUST first determine whether the Proxy-State AVP was created locally by looking at the address field of the AVP. Since it is the same AVP as the one that it added to the request, it will extract any embedded information within the Proxy-State AVP. If AVPs were encapsulated within the Proxy-State AVP, these SHOULD be extracted and added to the response. If the request from DIA1 included a Proxy-State AVP, the same AVP MUST be present in the response back to DIA1. 6.1.1 Proxy-State AVP The Proxy-State AVP (AVP Code 33) [1] is used by proxy servers when forwarding requests and contains opaque data that is used by the proxy to further process the response. Such data may include AVPs that are to be added to the response, information about the downstream peer, etc. A DIAMETER node that receives such an AVP in a request MUST return Calhoun et al. expires May 2000 [Page 30]
INTERNET DRAFT December 1999 the identical AVP in the response. Furthermore, no more than one Proxy-State AVP MUST be present in a message at any given time, so implementations MUST ensure that they remove any Proxy-State AVPs before adding their own. If the Proxy-State AVP was removed from a request, the same AVP MUST be inserted in the corresponding response before forwarding the message to the downstream peer. The Proxy-State AVP's Address field is 128-bits in length contains the IP address of the system created the AVP. If the host creating the AVP has an IPv4 address, the leading 96 bits MUST be set to zero (0). This field is intended to assist hosts in determining whether a Proxy-State AVP is intended for the local host. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ AVP Header (AVP Code = 33) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 128-bit Address... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data ... +-+-+-+-+-+-+-+-+ 6.1.2 Destination-NAI AVP The Destination-NAI AVP (AVP Code 269) is of type String and MAY be included in a request or response message, and MUST be in a format consistent with the NAI specification. When found in a response, the AVP SHOULD contain the value of the Host-Name AVP that was found in the request. This AVP SHOULD be used by intermediate proxies in the message routing process. 6.2 Message Redirection There are cases where a DIAMETER proxy, known as a broker, may wish to request that a server contact another directly instead of forwarding the message (figure 2). This is typically done when the broker provides simple NAI to Home DIAMETER Server address resolution services. In the example provided in figure 2, abc.net's DIAMETER server issues a request to its broker, which in turn returns a response that includes the Result-Code AVP set to a specific value (see section 5.2). When a response is received with such a value, the message MUST Calhoun et al. expires May 2000 [Page 31]
INTERNET DRAFT December 1999 also include one or more Redirect-Host AVPs. These AVPs contain address information that SHOULD be used to directly communicate with the Home DIAMETER Server. Note that the servers MAY cache the home server information in order to reduce the latency involved in any future messages destined for that home server. +------------------+ +---------+ | DIAMETER | | CRL DB/ | | Broker | | OCSP | +------------------+ +---------+ /|\ Request | Response + | Result Code = | Redirect \|/ +----------+ +----------+ | abc.net |/ \| xyz.net | | DIAMETER |--------------| DIAMETER | | Server |\ /| Server | +----------+ Direct +----------+ Communication Figure 2: DIAMETER Broker Returning Redirect Indication When returning the response with the Result-Code set to indicate a redirect indication, the broker MAY also include the certificates of both the requesting server, and the target server. These certificates are encapsulated in a CMS-Data AVP [11]. The requesting server SHOULD forward the certificate that belongs to it in the subsequent request to the home DIAMETER server. 6.2.1 Redirect-Host AVP The Redirect-Host AVP (AVP Code 278) is of type Address and is returned in a response that has the Result-Code AVP set to DIAMETER_REDIRECT_REQUEST. This AVP includes address information of the DIAMETER host to which the request must be redirected. Upon receipt of such a Result-Code, and this AVP, a DIAMETER host SHOULD send the request directly to the host. A proxy server or broker MAY return more than one Redirect-Host AVP if there is more than one DIAMETER server that can satisfy the request. The broker MAY wish to return the certificate associated with a given Redirect-Host AVP. This can be returned in a CMS-Data AVP, as defined in [11]. Calhoun et al. expires May 2000 [Page 32]
INTERNET DRAFT December 1999 7.0 DIAMETER Message Security The DIAMETER Base protocol MAY be secured in one of three ways. The first method does not involve any security mechanisms in the DIAMETER protocol, but relies on an underlying security mechanism, such as IP Security. The second method is hop-by-hop security, which SHOULD be supported by all DIAMETER implementations. The third method is optional and requires a Public Key Infrastructure [14], and is documented in [11]. 7.1 Hop-by-Hop Security DIAMETER Hop-by-Hop security provides message integrity and per AVP encryption, and requires that the communicating entities have a pre- configured shared secret, similar to the method employed by the RADIUS protocol. Hop-by-Hop security does not have the scaling properties associated with a public key infrastructure (PKI), which is used in end-to-end security, but MAY be desirable in environments where asymmetric technology is not required, or available. Hop-by-Hop security implies that each hop along a proxy chain is responsible for the following tasks: - Validating the message's integrity using the shared secret with the sender. - Decrypting any encrypted AVPs using the secret shared with the sender. - Re-encrypting AVPs using the secret shared with the next server. - Computing the message hash using the secret shared with the next server, and adding it to the ICV AVP in the DIAMETER message. (Shared-Secret-1) (Shared-Secret-2) +------+ -----> +------+ ------> +------+ | | | | | | | DIA1 +-------------------+ DIA2 +-------------------+ DIA3 | | | | | | | +------+ +------+ +------+ Figure 3: Hop-by-Hop Security in Proxy Environments The above steps that each proxy MUST perform in a proxy chain clearly describes the security issues associated with hop-by-hop security in a proxy environment. Since the message integrity is re-computed at each node in the chain, it is very difficult to detect if a proxy modified information in the message (e.g. session time). Furthermore, Calhoun et al. expires May 2000 [Page 33]
INTERNET DRAFT December 1999 any sensitive information would be known to all proxies in the chain, since each node must decrypt AVPs. Therefore, Any AVPs that require strong authentication and/or confidentiality in a proxy environment SHOULD be protected via the mechanism described in the strong security extension [11]. It is highly recommended that the size of the shared secrets used be sufficiently long (e.g. 128 bits), and that different shared secrets be used for both authentication and encryption. 7.1.1 Integrity-Check-Value AVP The Integrity-Check-Value AVP (AVP Code 259) is of type complex and is used for hop-by-hop authentication and integrity, and is not recommended for use with untrusted proxy servers. The DIAMETER header as well as all AVPs (including padding) up to this AVP is protected by the Integrity-Check-Value. Note that the Message Length field in the DIAMETER header MUST be set to zero (0) prior to the ICV calculation. The Timestamp and Nonce AVPs MUST be present in the message PRIOR to the Integrity-Check-Value AVP. The Timestamp AVP provides replay protection and the Nonce AVP provides randomness. Any AVPs in a message that is not succeeded by the Integrity-Check-Value AVP MUST be ignored. The following is an example of a message that include hop-by-hop security: <DIAMETER Message> ::= <DIAMETER Header> <Command-Code AVP> <Nonce AVP> [<Additional AVPs>] <Timestamp AVP> <Integrity-Check-Value AVP> All DIAMETER implementations SHOULD support this AVP. Calhoun et al. expires May 2000 [Page 34]
INTERNET DRAFT December 1999 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ AVP Header (AVP Code = 259) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Transform ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Key ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data ... +-+-+-+-+-+-+-+-+ AVP Length The length of this attribute MUST be at least 13. Transform ID The Transform ID field contains a value that identifies the transform that was used to compute the ICV. The following values are defined in this document: HMAC-MD5-96[6] 1 The ICV is computed using the HMAC-MD5 algorithm, and the first 12 bytes of the hash output is included in the data portion of the ICV AVP. All DIAMETER implementations supporting this AVP MUST support this transform. Using the example code provided in [6], the following call would be used to generate the Integrity-Check-Value: hmac_md5(DiameterMessage, MessageLength, Secret, Secretlength, Output) Key ID The Key ID field contains a key identifier, which is used to identify the keying information used to generate the AVP's data field. Data The data field contains the output from the hashing algorithm. 7.1.2 Encrypted-Payload AVP The Encrypted-Payload AVP (AVP Code 260) is of type complex and is used to encapsulate encrypted AVPs for privacy during transmission. Hop-by-Hop confidentiality is achieved by encapsulating all AVPs which are to be encrypted into an Encrypted-Payload AVP. This feature SHOULD be supported by DIAMETER implementations. Calhoun et al. expires May 2000 [Page 35]
INTERNET DRAFT December 1999 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ AVP Header (AVP Code = 260) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Transform ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Key ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data ... +-+-+-+-+-+-+-+-+ AVP Length The length of this attribute MUST be at least 13. Transform ID The Transform ID field contains a value that identifies the transform that was used to compute the ICV. The following values are defined in this document: MD5 1 See section 7.1.2.1 for more information. Key ID The Key ID field contains a key identifier, which is used to identify the keying information used to generate the AVP's data field. Data The data field contains the encrypted payload. 7.1.2.1 MD5 Payload Hiding MD5 Payload Hiding is supported by DIAMETER for backward compatibility with existing RADIUS infrastructure. The plain text (which is a buffer containing one or more AVPs) is first padded to a sixteen (16) byte boundary with 0 bytes. Since the encapsulated AVPs have length fields, it is possible to detect their boundaries, whether or not padding has been done. One or more Nonce AVPs MUST precede an Encrypted-Payload AVP. An MD5 hash is performed on the: - last Nonce AVP which precedes the Encrypted-Payload AVP - the shared authentication secret Calhoun et al. expires May 2000 [Page 36]
INTERNET DRAFT December 1999 This MD5 hash value is then XORed with the first 16 octet segment of the buffer to encrypt. The resulting 16 octet result is saved as the first 16 octets of the encrypted buffer. The result is also used to calculate a new value using MD5: - the shared authentication secret - the 16 byte result of the previous XOR This value is then XORed with the next 16 bytes. This is done for each 16 bytes successively in the buffer to encrypt, producing an equal sized encrypted buffer. The receiver of a DIAMETER message with an Encrypted-Payload AVP MUST first check the integrity of the message, either through the ICV, or the CMS-Data AVP [11] if it protects the Encrypted-Payload AVP. Then the Encrypted-Payload AVP is decrypted, by reversing the above procedure, which applied to the buffer will reproduce the plain text version. The decapsulated AVPs are then used to process the DIAMETER message in the normal manner. 7.2 Nonce AVP The Nonce AVP (AVP Code 261) is of type Data and MUST be present prior to the Integrity-Check-Value AVPs within a message and is used to ensure randomness within a message. The content of this AVP MUST be a random value of at least 128 bits. Some crypto algorithms are known to have weaknesses if a random value is not found early within the plaintext, therefore it is recommended that the Nonce AVP be added early in a message if possible. 7.3 Timestamp AVP The Timestamp AVP (AVP Code 262) is of type Time and is used to add replay protection to the DIAMETER protocol. This AVP MUST appear prior to the Integrity-Check-Value AVP or any other message integrity AVP defined in separate extensions. The value of time is the most significant four octets returned from an NTP server that indicates the number of seconds expired since Jan. 1, 1900. Messages that are older than a certain maximum age SHOULD be rejected and a response SHOULD be returned with the Result-Code AVP value set to DIAMETER_TIMEOUT. A DIAMETER node that receives a message with the Result-Code AVP set to DIAMETER-TIMEOUT MAY use the Timestamp AVP found in the message to synchronize its clock with its peer. Note that the larger the value, the more susceptible one is to a Calhoun et al. expires May 2000 [Page 37]
INTERNET DRAFT December 1999 replay attack. However, one does have to take into account the possibility for clock drift, and the latency involved in the transmission of the message over the network. The timestamp AVP SHOULD be updated prior to retransmission. Implementations must be prepared to wrap at the epochal 2038 where Time values are used, and 0,1,... MUST be considered greater than 2^32-1 at that time. 8.0 IANA Considerations This document defines a number of assigned numbers to be maintained by the IANA. This section explains the criteria to be used by the IANA to assign additional numbers in each of these lists. The following subsections describe the assignment policy for the namespaces defined elsewhere in this document. 8.1 AVP Attributes As defined in section 2.2, AVPs contain vendor ID, attribute and value fields. For vendor ID value of 0, IANA will maintain a registry of assigned AVP codes and in some case also values. Attribute 0-254 are assigned from the RADIUS protocol [1], whose attributes are also maintained through IANA. AVP Codes 256-280 are assigned within this document. The remaining values are available for assignment through Designated Expert [12]. 8.2 Command Code AVP Values As defined in section 2.3.1, the Command Code AVPs (AVP Code 256) have an associated value maintained by IANA. Values 0-255 are reserved for backward RADIUS compatibility, and values 256-258 are defined in this specification. The remaining values are available for assignment via Designated Expert [12]. 8.3 Extension Identifier Values As defined in section 2.6.5, the Extension Identifier is used to identify a specific DIAMETER Extension. All values, other than zero (0) are available for assignment via Standards Action [12]. Note that the DIAMETER protocol is not inteded to be extended for any purpose. Any extensions added to the protocol MUST ensure that they fit within the existing framework, and that no changes to the base Calhoun et al. expires May 2000 [Page 38]
INTERNET DRAFT December 1999 protocol are required. 8.4 Result-Code AVP Values As defined in Section 5.2, the Result Code AVP (AVP Code 268) defines the values 0-8. All remaining values are available for assignment via IETF Consensus [12]. 8.5 Integrity-Check-Value AVP Transform Values Section 7.1.1 defines the Integrity-Check-Value AVP (AVP Code 259) which contains a field called the Transform. This document reserves the value 1. All remaining values are available for assignment via Designated Expert [12]. 8.6 Reboot-Type AVP Values Section 2.6.3 defines the Reboot-Type AVP (AVP Code 271), which is used to inform the peer of the cause for the reboot. This document defines the values 1-3. All remaining values are available for assignment via Designated Expert [12]. 8.7 AVP Header Bits There are six remaining reserved bits in the AVP header. Additional bits should only be assigned via a Standards Action [12]. 9.0 Open Issues The following are the open issues that SHOULD be addressed in future versions of the DIAMETER protocol: - AVPs of type 'Time" are 32 bits in size and contain the a timestamp consistent with NTP [18]. This field is expected to expire sometime in 2038. Future investigation SHOULD be done to determine if a 64 bit time format could be used. - The fact that the Sender's IP Address is used in the construction of the Session-Id means that the introduction of Network Address Translation MAY cause two hosts to represent the same Session Identifier. This area needs to be investigated further to be able to support DIAMETER hosts on a private network. Calhoun et al. expires May 2000 [Page 39]
INTERNET DRAFT December 1999 - When additional hashing transforms are supporting by the DIAMETER base protocol, there SHOULD be a method to negotiate the transform to be used. This negotiation MUST NOT be prone to a bidding down attack to the lowest secure transform. 10.0 DIAMETER protocol related configurable parameters This section contains the configurable parameters that are found throughout this document: Device-Reboot-Ind Timer This timer is used to determine how long an implementation should issue another DRI message if no response is received. Default is 20 seconds. Device-Watchdog-Ind Timer This is the timer that determines the period of inactivity that must occur before a DWI is transmitted to the communicating peer. Default is 60 seconds, if DWI messages are sent. Receive Window The Receive window determines how many unacknowledged DIAMETER messages MAY be pending with a communicating peer. This is normally configured to a value that allows the node to effectively manage its receive buffers. Default is 7. Retransmission Timer The retransmission timer is the time period that a node will retransmit a message if no transport level acknowledgement was received. Default is 3 seconds. Maximum Retransmissions This is the maximum number of times a DIAMETER message will be retransmitted before it is determined that the communicating peer is no longer reachable. Default is 3. Delayed Acknowledgement Timer This timer is defined in [25]. Shared Secret The shared secret is a value that is known by two communicating peers, and is used to generate the Integrity-Check-Value AVP. There is no default. Maximum Age of an outstanding message Messages older than the maximum age SHOULD be rejected, as described in section 7.3. The recommended value is 4 seconds. Calhoun et al. expires May 2000 [Page 40]
INTERNET DRAFT December 1999 11.0 Security Considerations The DIAMETER base protocol requires that two communicating peers exchange messages in a secure fashion. This document documents two security methods that can be used. The first requires no security at the application layer, but rather relies on an underlying security mechanism, such as IP Security. When IP Security is not available, or desirable, the DIAMETER protocol MAY use hop-by-hop security, which requires communicating peers to share a long-lived secret. Hop-by-Hop security provides replay protection by requiring that the communicating peers share a time source, such as an NTP server. When the DIAMETER protocol is used in an inter-domain network, strong application level security MAY be required, such as non-repudiation. This the communicating peers do require this level of security either for legal or business purposes, the extension defined in [11] MAY be used. 12.0 References [1] Rigney, et alia, "RADIUS", RFC-2138, April 1997 [2] Reynolds, Postel, "Assigned Numbers", RFC 1700, October 1994. [3] Postel, "User Datagram Protocol", RFC 768, August 1980. [4] Rivest, "The MD5 Message-Digest Algorithm", RFC 1321, April 1992. [5] Kaufman, Perlman, Speciner, "Network Security: Private Communications in a Public World", Prentice Hall, March 1995, ISBN 0-13-061466-1. [6] Krawczyk, Bellare, Canetti, "HMAC: Keyed-Hashing for Message Authentication", RFC 2104, January 1997. [7] P. Calhoun, W. Bulley, "DIAMETER NASREQ Extension", draft- calhoun-diameter-nasreq-00.txt (work in progress), December 1999. [8] Aboba, Beadles "The Network Access Identifier." RFC 2486. January 1999. [9] Calhoun, Zorn, Pan, Akhtar, "DIAMETER Framework", draft- calhoun-diameter-framework-05.txt (work in progress), December 1999. [10] P. Calhoun, C. Perkins, "DIAMETER Mobile IP Extensions", draft-calhoun-diameter-mobileip-04.txt (work in progress), December 1999. [11] P. Calhoun, W. Bulley, S. Farrell, "DIAMETER Strong Security Extension", draft-calhoun-diameter-strong-security-00.txt (work in progress), December 1999. [12] Narten, Alvestrand,"Guidelines for Writing an IANA Calhoun et al. expires May 2000 [Page 41]
INTERNET DRAFT December 1999 Considerations Section in RFCs", BCP 26, RFC 2434, October 1998 [13] S. Bradner, "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [14] Myers, Ankney, Malpani, Galperin, Adams, "X.509 Internet Public Key Infrastructure Online Certificate Status Protocol (OCSP)", RFC 2560, June 1999. [15] Arkko, Calhoun, Patel, Zorn, "DIAMETER Accounting Extension", draft-calhoun-diameter-accounting-02.txt (work in progress), December 1999. [16] Hinden, Deering, "IP Version 6 Addressing Architecture", RFC 2373, July 1998. [17] ISI, "Internet Protocol", RFC 791, September 1981. [18] Mills, "Simple Network Time Protocol (SNTP) Version 4 for IPv4, IPv6 and OSI, RFC 2030, October 1996. [19] Housley, Ford, Polk, Solo, "Internet X.509 Public Key Infrastructure Certificate and CRL Profile", RFC 2459, January 1999. [20] B. Aboba, G. Zorn, "Criteria for Evaluating Roaming Protocols", RFC 2477, January 1999. [21] M. Beadles, "Criteria for Evaluating Network Access Server Protocols", draft-ietf-nasreq-criteria-03.txt (work in progress), October 1999. [22] T. Hiller et al., "Cdma2000 Wireless Data Requirements for AAA", draft-hiller-cdma2000-AAA-00.txt (work in progress), October 1999. [23] S. Glass, S. Jacobs, C. Perkin, "Mobile IP Authentication, Authorization, and Accounting Requirements", draft-ietf- mobileip-aaa-reqs-01.txt (work in progress), October 1999. [24] F. Yergeau, "UTF-8, a transformation format of ISO 10646", RFC 2279, January 1998. [25] P. Calhoun, A. Rubens, H. Akhtar, E. Guttman, W. Bulley, J. Haag, "DIAMETER Implementation Guidelines", draft-calhoun- diameter-impl-guide-00.txt (work in progress), December 1999. 13.0 Acknowledgements The authors would like to thank Nenad Trifunovic, Tony Johansson and Pankaj Patel for their participation in the Document Reading Party. The authors would also like to acknowledge the following people for their contribution in the development of the DIAMETER protocol: Bernard Aboba, Jari Arkko, William Bulley, Daniel C. Fox, Lol Grant, Ignacio Goyret, Nancy Greene, Peter Heitman, Paul Krumviede, Fergal Ladley, Ryan Moats, Victor Muslin, Kenneth Peirce, Stephen Farrell,Sumit Vakil, John R. Vollbrecht, Jeff Weisberg and Glen Zorn Calhoun et al. expires May 2000 [Page 42]
INTERNET DRAFT December 1999 14.0 Author's Addresses Questions about this memo can be directed to: Pat R. Calhoun Network and Security Research Center, Sun Laboratories Sun Microsystems, Inc. 15 Network Circle Menlo Park, California, 94025 USA Phone: 1-650-786-7733 Fax: 1-650-786-6445 E-mail: pcalhoun@eng.sun.com Allan C. Rubens Tut Systems, Inc. 220 E. Huron, Suite 260 Ann Arbor, MI 48104 USA Phone: 1-734-995-1697 E-Mail: arubens@tutsys.com Haseeb Akhtar Wireless Technology Labs Nortel Networks 2221 Lakeside Blvd. Richardson, TX 75082-4399 USA Phone: 1-972-684-8850 E-Mail: haseeb@nortelnetworks.com Erik Guttman Network and Security Research Center, Sun Laboratories Sun Microsystems, Inc. Eichhoelzelstr. 7 74915 Waibstadt Germany Phone: 49-7263-911-701 E-mail: erik.guttman@germany.sun.com Calhoun et al. expires May 2000 [Page 43]
INTERNET DRAFT December 1999 15.0 Full Copyright Statement Copyright (C) The Internet Society (1999). All Rights Reserved. This document and translations of it may be copied and furnished to others, 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 Inter- net organizations, except as needed for the purpose of developing 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 permis- sions 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 WAR- RANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE." Calhoun et al. expires May 2000 [Page 44]