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diff --git a/doc/rfc/rfc3588.txt b/doc/rfc/rfc3588.txt new file mode 100644 index 0000000..fe4ff08 --- /dev/null +++ b/doc/rfc/rfc3588.txt @@ -0,0 +1,8235 @@ + + + + + + +Network Working Group P. Calhoun +Request for Comments: 3588 Airespace, Inc. +Category: Standards Track J. Loughney + Nokia + E. Guttman + Sun Microsystems, Inc. + G. Zorn + Cisco Systems, Inc. + J. Arkko + Ericsson + September 2003 + + + Diameter Base Protocol + +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. + +Copyright Notice + + Copyright (C) The Internet Society (2003). All Rights Reserved. + +Abstract + + The Diameter base protocol is intended to provide an Authentication, + Authorization and Accounting (AAA) framework for applications such as + network access or IP mobility. Diameter is also intended to work in + both local Authentication, Authorization & Accounting and roaming + situations. This document specifies the message format, transport, + error reporting, accounting and security services to be used by all + Diameter applications. The Diameter base application needs to be + supported by all Diameter implementations. + +Conventions Used In This Document + + 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 BCP 14, RFC 2119 + [KEYWORD]. + + + + + + + +Calhoun, et al. Standards Track [Page 1] + +RFC 3588 Diameter Based Protocol September 2003 + + +Table of Contents + + 1. Introduction................................................. 6 + 1.1. Diameter Protocol..................................... 9 + 1.1.1. Description of the Document Set.............. 10 + 1.2. Approach to Extensibility............................. 11 + 1.2.1. Defining New AVP Values...................... 11 + 1.2.2. Creating New AVPs............................ 11 + 1.2.3. Creating New Authentication Applications..... 11 + 1.2.4. Creating New Accounting Applications......... 12 + 1.2.5. Application Authentication Procedures........ 14 + 1.3. Terminology........................................... 14 + 2. Protocol Overview............................................ 18 + 2.1. Transport............................................. 20 + 2.1.1. SCTP Guidelines.............................. 21 + 2.2. Securing Diameter Messages............................ 21 + 2.3. Diameter Application Compliance....................... 21 + 2.4. Application Identifiers............................... 22 + 2.5. Connections vs. Sessions.............................. 22 + 2.6. Peer Table............................................ 23 + 2.7. Realm-Based Routing Table............................. 24 + 2.8. Role of Diameter Agents............................... 25 + 2.8.1. Relay Agents................................. 26 + 2.8.2. Proxy Agents................................. 27 + 2.8.3. Redirect Agents.............................. 28 + 2.8.4. Translation Agents........................... 29 + 2.9. End-to-End Security Framework......................... 30 + 2.10. Diameter Path Authorization........................... 30 + 3. Diameter Header.............................................. 32 + 3.1. Command Codes......................................... 35 + 3.2. Command Code ABNF specification....................... 36 + 3.3. Diameter Command Naming Conventions................... 38 + 4. Diameter AVPs................................................ 38 + 4.1. AVP Header............................................ 39 + 4.1.1. Optional Header Elements..................... 41 + 4.2. Basic AVP Data Formats................................ 41 + 4.3. Derived AVP Data Formats.............................. 42 + 4.4. Grouped AVP Values.................................... 49 + 4.4.1. Example AVP with a Grouped Data Type......... 50 + 4.5. Diameter Base Protocol AVPs........................... 53 + 5. Diameter Peers............................................... 56 + 5.1. Peer Connections...................................... 56 + 5.2. Diameter Peer Discovery............................... 56 + 5.3. Capabilities Exchange................................. 59 + 5.3.1. Capabilities-Exchange-Request................ 60 + 5.3.2. Capabilities-Exchange-Answer................. 60 + 5.3.3. Vendor-Id AVP................................ 61 + 5.3.4. Firmware-Revision AVP........................ 61 + + + +Calhoun, et al. Standards Track [Page 2] + +RFC 3588 Diameter Based Protocol September 2003 + + + 5.3.5. Host-IP-Address AVP.......................... 62 + 5.3.6. Supported-Vendor-Id AVP...................... 62 + 5.3.7. Product-Name AVP............................. 62 + 5.4. Disconnecting Peer Connections........................ 62 + 5.4.1. Disconnect-Peer-Request...................... 63 + 5.4.2. Disconnect-Peer-Answer....................... 63 + 5.4.3. Disconnect-Cause AVP......................... 63 + 5.5. Transport Failure Detection........................... 64 + 5.5.1. Device-Watchdog-Request...................... 64 + 5.5.2. Device-Watchdog-Answer....................... 64 + 5.5.3. Transport Failure Algorithm.................. 65 + 5.5.4. Failover and Failback Procedures............. 65 + 5.6. Peer State Machine.................................... 66 + 5.6.1. Incoming connections......................... 68 + 5.6.2. Events....................................... 69 + 5.6.3. Actions...................................... 70 + 5.6.4. The Election Process......................... 71 + 6. Diameter Message Processing.................................. 71 + 6.1. Diameter Request Routing Overview..................... 71 + 6.1.1. Originating a Request........................ 73 + 6.1.2. Sending a Request............................ 73 + 6.1.3. Receiving Requests........................... 73 + 6.1.4. Processing Local Requests.................... 73 + 6.1.5. Request Forwarding........................... 74 + 6.1.6. Request Routing.............................. 74 + 6.1.7. Redirecting Requests......................... 74 + 6.1.8. Relaying and Proxying Requests............... 75 + 6.2. Diameter Answer Processing............................ 76 + 6.2.1. Processing Received Answers.................. 77 + 6.2.2. Relaying and Proxying Answers................ 77 + 6.3. Origin-Host AVP....................................... 77 + 6.4. Origin-Realm AVP...................................... 78 + 6.5. Destination-Host AVP.................................. 78 + 6.6. Destination-Realm AVP................................. 78 + 6.7. Routing AVPs.......................................... 78 + 6.7.1. Route-Record AVP............................. 79 + 6.7.2. Proxy-Info AVP............................... 79 + 6.7.3. Proxy-Host AVP............................... 79 + 6.7.4. Proxy-State AVP.............................. 79 + 6.8. Auth-Application-Id AVP............................... 79 + 6.9. Acct-Application-Id AVP............................... 79 + 6.10. Inband-Security-Id AVP................................ 79 + 6.11. Vendor-Specific-Application-Id AVP.................... 80 + 6.12. Redirect-Host AVP..................................... 80 + 6.13. Redirect-Host-Usage AVP............................... 80 + 6.14. Redirect-Max-Cache-Time AVP........................... 81 + 6.15. E2E-Sequence AVP...................................... 82 + + + + +Calhoun, et al. Standards Track [Page 3] + +RFC 3588 Diameter Based Protocol September 2003 + + + 7. Error Handling............................................... 82 + 7.1. Result-Code AVP....................................... 84 + 7.1.1. Informational................................ 84 + 7.1.2. Success...................................... 84 + 7.1.3. Protocol Errors.............................. 85 + 7.1.4. Transient Failures........................... 86 + 7.1.5. Permanent Failures........................... 86 + 7.2. Error Bit............................................. 88 + 7.3. Error-Message AVP..................................... 89 + 7.4. Error-Reporting-Host AVP.............................. 89 + 7.5. Failed-AVP AVP........................................ 89 + 7.6. Experimental-Result AVP............................... 90 + 7.7. Experimental-Result-Code AVP.......................... 90 + 8. Diameter User Sessions....................................... 90 + 8.1. Authorization Session State Machine................... 92 + 8.2. Accounting Session State Machine...................... 96 + 8.3. Server-Initiated Re-Auth.............................. 101 + 8.3.1. Re-Auth-Request.............................. 102 + 8.3.2. Re-Auth-Answer............................... 102 + 8.4. Session Termination................................... 103 + 8.4.1. Session-Termination-Request.................. 104 + 8.4.2. Session-Termination-Answer................... 105 + 8.5. Aborting a Session.................................... 105 + 8.5.1. Abort-Session-Request........................ 106 + 8.5.2. Abort-Session-Answer......................... 106 + 8.6. Inferring Session Termination from Origin-State-Id.... 107 + 8.7. Auth-Request-Type AVP................................. 108 + 8.8. Session-Id AVP........................................ 108 + 8.9. Authorization-Lifetime AVP............................ 109 + 8.10. Auth-Grace-Period AVP................................. 110 + 8.11. Auth-Session-State AVP................................ 110 + 8.12. Re-Auth-Request-Type AVP.............................. 110 + 8.13. Session-Timeout AVP................................... 111 + 8.14. User-Name AVP......................................... 111 + 8.15. Termination-Cause AVP................................. 111 + 8.16. Origin-State-Id AVP................................... 112 + 8.17. Session-Binding AVP................................... 113 + 8.18. Session-Server-Failover AVP........................... 113 + 8.19. Multi-Round-Time-Out AVP.............................. 114 + 8.20. Class AVP............................................. 114 + 8.21. Event-Timestamp AVP................................... 115 + 9. Accounting................................................... 115 + 9.1. Server Directed Model................................. 115 + 9.2. Protocol Messages..................................... 116 + 9.3. Application Document Requirements..................... 116 + 9.4. Fault Resilience...................................... 116 + 9.5. Accounting Records.................................... 117 + 9.6. Correlation of Accounting Records..................... 118 + + + +Calhoun, et al. Standards Track [Page 4] + +RFC 3588 Diameter Based Protocol September 2003 + + + 9.7. Accounting Command-Codes.............................. 119 + 9.7.1. Accounting-Request........................... 119 + 9.7.2. Accounting-Answer............................ 120 + 9.8. Accounting AVPs....................................... 121 + 9.8.1. Accounting-Record-Type AVP................... 121 + 9.8.2. Acct-Interim-Interval AVP.................... 122 + 9.8.3. Accounting-Record-Number AVP................. 123 + 9.8.4. Acct-Session-Id AVP.......................... 123 + 9.8.5. Acct-Multi-Session-Id AVP.................... 123 + 9.8.6. Accounting-Sub-Session-Id AVP................ 123 + 9.8.7. Accounting-Realtime-Required AVP............. 123 + 10. AVP Occurrence Table......................................... 124 + 10.1. Base Protocol Command AVP Table....................... 124 + 10.2. Accounting AVP Table.................................. 126 + 11. IANA Considerations.......................................... 127 + 11.1. AVP Header............................................ 127 + 11.1.1. AVP Code..................................... 127 + 11.1.2. AVP Flags.................................... 128 + 11.2. Diameter Header....................................... 128 + 11.2.1. Command Codes................................ 128 + 11.2.2. Command Flags................................ 129 + 11.3. Application Identifiers............................... 129 + 11.4. AVP Values............................................ 129 + 11.4.1. Result-Code AVP Values....................... 129 + 11.4.2. Accounting-Record-Type AVP Values............ 130 + 11.4.3. Termination-Cause AVP Values................. 130 + 11.4.4. Redirect-Host-Usage AVP Values............... 130 + 11.4.5. Session-Server-Failover AVP Values........... 130 + 11.4.6. Session-Binding AVP Values................... 130 + 11.4.7. Disconnect-Cause AVP Values.................. 130 + 11.4.8. Auth-Request-Type AVP Values................. 130 + 11.4.9. Auth-Session-State AVP Values................ 130 + 11.4.10. Re-Auth-Request-Type AVP Values.............. 131 + 11.4.11. Accounting-Realtime-Required AVP Values...... 131 + 11.5. Diameter TCP/SCTP Port Numbers........................ 131 + 11.6. NAPTR Service Fields.................................. 131 + 12. Diameter Protocol Related Configurable Parameters............ 131 + 13. Security Considerations...................................... 132 + 13.1. IPsec Usage........................................... 133 + 13.2. TLS Usage............................................. 134 + 13.3. Peer-to-Peer Considerations........................... 134 + 14. References................................................... 136 + 14.1. Normative References.................................. 136 + 14.2. Informative References................................ 138 + 15. Acknowledgements............................................. 140 + Appendix A. Diameter Service Template........................... 141 + Appendix B. NAPTR Example....................................... 142 + Appendix C. Duplicate Detection................................. 143 + + + +Calhoun, et al. Standards Track [Page 5] + +RFC 3588 Diameter Based Protocol September 2003 + + + Appendix D. Intellectual Property Statement..................... 145 + Authors' Addresses............................................... 146 + Full Copyright Statement......................................... 147 + +1. Introduction + + Authentication, Authorization and Accounting (AAA) protocols such as + TACACS [TACACS] and RADIUS [RADIUS] were initially deployed to + provide dial-up PPP [PPP] and terminal server access. Over time, + with the growth of the Internet and the introduction of new access + technologies, including wireless, DSL, Mobile IP and Ethernet, + routers and network access servers (NAS) have increased in complexity + and density, putting new demands on AAA protocols. + + Network access requirements for AAA protocols are summarized in + [AAAREQ]. These include: + + Failover + [RADIUS] does not define failover mechanisms, and as a result, + failover behavior differs between implementations. In order to + provide well defined failover behavior, Diameter supports + application-layer acknowledgements, and defines failover + algorithms and the associated state machine. This is described in + Section 5.5 and [AAATRANS]. + + Transmission-level security + [RADIUS] defines an application-layer authentication and integrity + scheme that is required only for use with Response packets. While + [RADEXT] defines an additional authentication and integrity + mechanism, use is only required during Extensible Authentication + Protocol (EAP) sessions. While attribute-hiding is supported, + [RADIUS] does not provide support for per-packet confidentiality. + In accounting, [RADACCT] assumes that replay protection is + provided by the backend billing server, rather than within the + protocol itself. + + While [RFC3162] defines the use of IPsec with RADIUS, support for + IPsec is not required. Since within [IKE] authentication occurs + only within Phase 1 prior to the establishment of IPsec SAs in + Phase 2, it is typically not possible to define separate trust or + authorization schemes for each application. This limits the + usefulness of IPsec in inter-domain AAA applications (such as + roaming) where it may be desirable to define a distinct + certificate hierarchy for use in a AAA deployment. In order to + provide universal support for transmission-level security, and + enable both intra- and inter-domain AAA deployments, IPsec support + is mandatory in Diameter, and TLS support is optional. Security + is discussed in Section 13. + + + +Calhoun, et al. Standards Track [Page 6] + +RFC 3588 Diameter Based Protocol September 2003 + + + Reliable transport + RADIUS runs over UDP, and does not define retransmission behavior; + as a result, reliability varies between implementations. As + described in [ACCMGMT], this is a major issue in accounting, where + packet loss may translate directly into revenue loss. In order to + provide well defined transport behavior, Diameter runs over + reliable transport mechanisms (TCP, SCTP) as defined in + [AAATRANS]. + + Agent support + [RADIUS] does not provide for explicit support for agents, + including Proxies, Redirects and Relays. Since the expected + behavior is not defined, it varies between implementations. + Diameter defines agent behavior explicitly; this is described in + Section 2.8. + + Server-initiated messages + While RADIUS server-initiated messages are defined in [DYNAUTH], + support is optional. This makes it difficult to implement + features such as unsolicited disconnect or + reauthentication/reauthorization on demand across a heterogeneous + deployment. Support for server-initiated messages is mandatory in + Diameter, and is described in Section 8. + + Auditability + RADIUS does not define data-object security mechanisms, and as a + result, untrusted proxies may modify attributes or even packet + headers without being detected. Combined with lack of support for + capabilities negotiation, this makes it very difficult to + determine what occurred in the event of a dispute. While + implementation of data object security is not mandatory within + Diameter, these capabilities are supported, and are described in + [AAACMS]. + + Transition support + While Diameter does not share a common protocol data unit (PDU) + with RADIUS, considerable effort has been expended in enabling + backward compatibility with RADIUS, so that the two protocols may + be deployed in the same network. Initially, it is expected that + Diameter will be deployed within new network devices, as well as + within gateways enabling communication between legacy RADIUS + devices and Diameter agents. This capability, described in + [NASREQ], enables Diameter support to be added to legacy networks, + by addition of a gateway or server speaking both RADIUS and + Diameter. + + + + + + +Calhoun, et al. Standards Track [Page 7] + +RFC 3588 Diameter Based Protocol September 2003 + + + In addition to addressing the above requirements, Diameter also + provides support for the following: + + Capability negotiation + RADIUS does not support error messages, capability negotiation, or + a mandatory/non-mandatory flag for attributes. Since RADIUS + clients and servers are not aware of each other's capabilities, + they may not be able to successfully negotiate a mutually + acceptable service, or in some cases, even be aware of what + service has been implemented. Diameter includes support for error + handling (Section 7), capability negotiation (Section 5.3), and + mandatory/non-mandatory attribute-value pairs (AVPs) (Section + 4.1). + + Peer discovery and configuration + RADIUS implementations typically require that the name or address + of servers or clients be manually configured, along with the + corresponding shared secrets. This results in a large + administrative burden, and creates the temptation to reuse the + RADIUS shared secret, which can result in major security + vulnerabilities if the Request Authenticator is not globally and + temporally unique as required in [RADIUS]. Through DNS, Diameter + enables dynamic discovery of peers. Derivation of dynamic session + keys is enabled via transmission-level security. + + Roaming support + The ROAMOPS WG provided a survey of roaming implementations + [ROAMREV], detailed roaming requirements [ROAMCRIT], defined the + Network Access Identifier (NAI) [NAI], and documented existing + implementations (and imitations) of RADIUS-based roaming + [PROXYCHAIN]. In order to improve scalability, [PROXYCHAIN] + introduced the concept of proxy chaining via an intermediate + server, facilitating roaming between providers. However, since + RADIUS does not provide explicit support for proxies, and lacks + auditability and transmission-level security features, RADIUS- + based roaming is vulnerable to attack from external parties as + well as susceptible to fraud perpetrated by the roaming partners + themselves. As a result, it is not suitable for wide-scale + deployment on the Internet [PROXYCHAIN]. By providing explicit + support for inter-domain roaming and message routing (Sections 2.7 + and 6), auditability [AAACMS], and transmission-layer security + (Section 13) features, Diameter addresses these limitations and + provides for secure and scalable roaming. + + In the decade since AAA protocols were first introduced, the + capabilities of Network Access Server (NAS) devices have increased + substantially. As a result, while Diameter is a considerably more + sophisticated protocol than RADIUS, it remains feasible to implement + + + +Calhoun, et al. Standards Track [Page 8] + +RFC 3588 Diameter Based Protocol September 2003 + + + within embedded devices, given improvements in processor speeds and + the widespread availability of embedded IPsec and TLS + implementations. + +1.1. Diameter Protocol + + The Diameter base protocol provides the following facilities: + + - Delivery of AVPs (attribute value pairs) + - Capabilities negotiation + - Error notification + - Extensibility, through addition of new commands and AVPs (required + in [AAAREQ]). + - Basic services necessary for applications, such as handling of + user sessions or accounting + + 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 that + employ Diameter. AVPs may be added arbitrarily to Diameter messages, + so long as the required AVPs are included and AVPs that are + explicitly excluded are not included. AVPs are used by the base + Diameter protocol to support the following required features: + + - Transporting of user authentication information, for the purposes + of enabling the Diameter server to authenticate the user. + + - Transporting of service specific authorization information, + between client and servers, allowing the peers to decide whether a + user's access request should be granted. + + - Exchanging resource usage information, which MAY be used for + accounting purposes, capacity planning, etc. + + - Relaying, proxying and redirecting of Diameter messages through a + server hierarchy. + + The Diameter base protocol provides the minimum requirements needed + for a AAA protocol, as required by [AAAREQ]. The base protocol may + be used by itself for accounting purposes only, or it may be used + with a Diameter application, such as Mobile IPv4 [DIAMMIP], or + network access [NASREQ]. It is also possible for the base protocol + to be extended for use in new applications, via the addition of new + commands or AVPs. At this time the focus of Diameter is network + access and accounting applications. A truly generic AAA protocol + used by many applications might provide functionality not provided by + Diameter. Therefore, it is imperative that the designers of new + applications understand their requirements before using Diameter. + + + +Calhoun, et al. Standards Track [Page 9] + +RFC 3588 Diameter Based Protocol September 2003 + + + See Section 2.4 for more information on Diameter applications. + + Any node can initiate a request. In that sense, Diameter is a peer- + to-peer protocol. In this document, a Diameter Client is a device at + the edge of the network that performs access control, such as a + Network Access Server (NAS) or a Foreign Agent (FA). A Diameter + client generates Diameter messages to request authentication, + authorization, and accounting services for the user. A Diameter + agent is a node that does not authenticate and/or authorize messages + locally; agents include proxies, redirects and relay agents. A + Diameter server performs authentication and/or authorization of the + user. A Diameter node MAY act as an agent for certain requests while + acting as a server for others. + + The Diameter protocol also supports server-initiated messages, such + as a request to abort service to a particular user. + +1.1.1. Description of the Document Set + + Currently, the Diameter specification consists of a base + specification (this document), Transport Profile [AAATRANS] and + applications: Mobile IPv4 [DIAMMIP], and NASREQ [NASREQ]. + + The Transport Profile document [AAATRANS] discusses transport layer + issues that arise with AAA protocols and recommendations on how to + overcome these issues. This document also defines the Diameter + failover algorithm and state machine. + + The Mobile IPv4 [DIAMMIP] application defines a Diameter application + that allows a Diameter server to perform AAA functions for Mobile + IPv4 services to a mobile node. + + The NASREQ [NASREQ] application defines a Diameter Application that + allows a Diameter server to be used in a PPP/SLIP Dial-Up and + Terminal Server Access environment. Consideration was given for + servers that need to perform protocol conversion between Diameter and + RADIUS. + + In summary, this document defines the base protocol specification for + AAA, which includes support for accounting. The Mobile IPv4 and the + NASREQ documents describe applications that use this base + specification for Authentication, Authorization and Accounting. + + + + + + + + + +Calhoun, et al. Standards Track [Page 10] + +RFC 3588 Diameter Based Protocol September 2003 + + +1.2. Approach to Extensibility + + The Diameter protocol is designed to be extensible, using several + mechanisms, including: + + - Defining new AVP values + - Creating new AVPs + - Creating new authentication/authorization applications + - Creating new accounting applications + - Application authentication procedures + + Reuse of existing AVP values, AVPs and Diameter applications are + strongly recommended. Reuse simplifies standardization and + implementation and avoids potential interoperability issues. It is + expected that command codes are reused; new command codes can only be + created by IETF Consensus (see Section 11.2.1). + +1.2.1. Defining New AVP Values + + New applications should attempt to reuse AVPs defined in existing + applications when possible, as opposed to creating new AVPs. For + AVPs of type Enumerated, an application may require a new value to + communicate some service-specific information. + + In order to allocate a new AVP value, a request MUST be sent to IANA + [IANA], along with an explanation of the new AVP value. IANA + considerations for Diameter are discussed in Section 11. + +1.2.2. Creating New AVPs + + When no existing AVP can be used, a new AVP should be created. The + new AVP being defined MUST use one of the data types listed in + Section 4.2. + + In the event that a logical grouping of AVPs is necessary, and + multiple "groups" are possible in a given command, it is recommended + that a Grouped AVP be used (see Section 4.4). + + In order to create a new AVP, a request MUST be sent to IANA, with a + specification for the AVP. The request MUST include the commands + that would make use of the AVP. + +1.2.3. Creating New Authentication Applications + + Every Diameter application specification MUST have an IANA assigned + Application Identifier (see Section 2.4) or a vendor specific + Application Identifier. + + + + +Calhoun, et al. Standards Track [Page 11] + +RFC 3588 Diameter Based Protocol September 2003 + + + Should a new Diameter usage scenario find itself unable to fit within + an existing application without requiring major changes to the + specification, it may be desirable to create a new Diameter + application. Major changes to an application include: + + - Adding new AVPs to the command, which have the "M" bit set. + + - Requiring a command that has a different number of round trips to + satisfy a request (e.g., application foo has a command that + requires one round trip, but new application bar has a command + that requires two round trips to complete). + + - Adding support for an authentication method requiring definition + of new AVPs for use with the application. Since a new EAP + authentication method can be supported within Diameter without + requiring new AVPs, addition of EAP methods does not require the + creation of a new authentication application. + + Creation of a new application should be viewed as a last resort. An + implementation MAY add arbitrary non-mandatory AVPs to any command + defined in an application, including vendor-specific AVPs without + needing to define a new application. Please refer to Section 11.1.1 + for details. + + In order to justify allocation of a new application identifier, + Diameter applications MUST define one Command Code, or add new + mandatory AVPs to the ABNF. + + The expected AVPs MUST be defined in an ABNF [ABNF] grammar (see + Section 3.2). If the Diameter application has accounting + requirements, it MUST also specify the AVPs that are to be present in + the Diameter Accounting messages (see Section 9.3). However, just + because a new authentication application id is required, does not + imply that a new accounting application id is required. + + When possible, a new Diameter application SHOULD reuse existing + Diameter AVPs, in order to avoid defining multiple AVPs that carry + similar information. + +1.2.4. Creating New Accounting Applications + + There are services that only require Diameter accounting. Such + services need to define the AVPs carried in the Accounting-Request + (ACR)/ Accounting-Answer (ACA) messages, but do not need to define + new command codes. An implementation MAY add arbitrary non-mandatory + AVPs (AVPs with the "M" bit not set) to any command defined in an + + + + + +Calhoun, et al. Standards Track [Page 12] + +RFC 3588 Diameter Based Protocol September 2003 + + + application, including vendor-specific AVPs, without needing to + define a new accounting application. Please refer to Section 11.1.1 + for details. + + Application Identifiers are still required for Diameter capability + exchange. Every Diameter accounting application specification MUST + have an IANA assigned Application Identifier (see Section 2.4) or a + vendor specific Application Identifier. + + Every Diameter implementation MUST support accounting. Basic + accounting support is sufficient to handle any application that uses + the ACR/ACA commands defined in this document, as long as no new + mandatory AVPs are added. A mandatory AVP is defined as one which + has the "M" bit set when sent within an accounting command, + regardless of whether it is required or optional within the ABNF for + the accounting application. + + The creation of a new accounting application should be viewed as a + last resort and MUST NOT be used unless a new command or additional + mechanisms (e.g., application defined state machine) is defined + within the application, or new mandatory AVPs are added to the ABNF. + + Within an accounting command, setting the "M" bit implies that a + backend server (e.g., billing server) or the accounting server itself + MUST understand the AVP in order to compute a correct bill. If the + AVP is not relevant to the billing process, when the AVP is included + within an accounting command, it MUST NOT have the "M" bit set, even + if the "M" bit is set when the same AVP is used within other Diameter + commands (i.e., authentication/authorization commands). + + A DIAMETER base accounting implementation MUST be configurable to + advertise supported accounting applications in order to prevent the + accounting server from accepting accounting requests for unbillable + services. The combination of the home domain and the accounting + application Id can be used in order to route the request to the + appropriate accounting server. + + When possible, a new Diameter accounting application SHOULD attempt + to reuse existing AVPs, in order to avoid defining multiple AVPs that + carry similar information. + + If the base accounting is used without any mandatory AVPs, new + commands or additional mechanisms (e.g., application defined state + machine), then the base protocol defined standard accounting + application Id (Section 2.4) MUST be used in ACR/ACA commands. + + + + + + +Calhoun, et al. Standards Track [Page 13] + +RFC 3588 Diameter Based Protocol September 2003 + + +1.2.5. Application Authentication Procedures + + When possible, applications SHOULD be designed such that new + authentication methods MAY be added without requiring changes to the + application. This MAY require that new AVP values be assigned to + represent the new authentication transform, or any other scheme that + produces similar results. When possible, authentication frameworks, + such as Extensible Authentication Protocol [EAP], SHOULD be used. + +1.3. Terminology + + AAA + Authentication, Authorization and Accounting. + + Accounting + The act of collecting information on resource usage for the + purpose of capacity planning, auditing, billing or cost + allocation. + + Accounting Record + An accounting record represents a summary of the resource + consumption of a user over the entire session. Accounting servers + creating the accounting record may do so by processing interim + accounting events or accounting events from several devices + serving the same user. + + Authentication + The act of verifying the identity of an entity (subject). + + Authorization + The act of determining whether a requesting entity (subject) will + be allowed access to a resource (object). + + AVP + The Diameter protocol consists of a header followed by one or more + Attribute-Value-Pairs (AVPs). An AVP includes a header and is + used to encapsulate protocol-specific data (e.g., routing + information) as well as authentication, authorization or + accounting information. + + Broker + A broker is a business term commonly used in AAA infrastructures. + A broker is either a relay, proxy or redirect agent, and MAY be + operated by roaming consortiums. Depending on the business model, + a broker may either choose to deploy relay agents or proxy + agents. + + + + + +Calhoun, et al. Standards Track [Page 14] + +RFC 3588 Diameter Based Protocol September 2003 + + + Diameter Agent + A Diameter Agent is a Diameter node that provides either relay, + proxy, redirect or translation services. + + Diameter Client + A Diameter Client is a device at the edge of the network that + performs access control. An example of a Diameter client is a + Network Access Server (NAS) or a Foreign Agent (FA). + + Diameter Node + A Diameter node is a host process that implements the Diameter + protocol, and acts either as a Client, Agent or Server. + + Diameter Peer + A Diameter Peer is a Diameter Node to which a given Diameter Node + has a direct transport connection. + + Diameter Security Exchange + A Diameter Security Exchange is a process through which two + Diameter nodes establish end-to-end security. + + Diameter Server + A Diameter Server is one that handles authentication, + authorization and accounting requests for a particular realm. By + its very nature, a Diameter Server MUST support Diameter + applications in addition to the base protocol. + + Downstream + Downstream is used to identify the direction of a particular + Diameter message from the home server towards the access device. + + End-to-End Security + TLS and IPsec provide hop-by-hop security, or security across a + transport connection. When relays or proxy are involved, this + hop-by-hop security does not protect the entire Diameter user + session. End-to-end security is security between two Diameter + nodes, possibly communicating through Diameter Agents. This + security protects the entire Diameter communications path from the + originating Diameter node to the terminating Diameter node. + + Home Realm + A Home Realm is the administrative domain with which the user + maintains an account relationship. + + Home Server + See Diameter Server. + + + + + +Calhoun, et al. Standards Track [Page 15] + +RFC 3588 Diameter Based Protocol September 2003 + + + Interim accounting + An interim accounting message provides a snapshot of usage during + a user's session. It is typically implemented in order to provide + for partial accounting of a user's session in the case of a device + reboot or other network problem prevents the reception of a + session summary message or session record. + + Local Realm + A local realm is the administrative domain providing services to a + user. An administrative domain MAY act as a local realm for + certain users, while being a home realm for others. + + Multi-session + A multi-session represents a logical linking of several sessions. + Multi-sessions are tracked by using the Acct-Multi-Session-Id. An + example of a multi-session would be a Multi-link PPP bundle. Each + leg of the bundle would be a session while the entire bundle would + be a multi-session. + + Network Access Identifier + The Network Access Identifier, or NAI [NAI], is used in the + Diameter protocol to extract a user's identity and realm. The + identity is used to identify the user during authentication and/or + authorization, while the realm is used for message routing + purposes. + + Proxy Agent or Proxy + In addition to forwarding requests and responses, proxies make + policy decisions relating to resource usage and provisioning. + This is typically accomplished by tracking the state of NAS + devices. While proxies typically do not respond to client + Requests prior to receiving a Response from the server, they may + originate Reject messages in cases where policies are violated. + As a result, proxies need to understand the semantics of the + messages passing through them, and may not support all Diameter + applications. + + Realm + The string in the NAI that immediately follows the '@' character. + NAI realm names are required to be unique, and are piggybacked on + the administration of the DNS namespace. Diameter makes use of + the realm, also loosely referred to as domain, to determine + whether messages can be satisfied locally, or whether they must be + routed or redirected. In RADIUS, realm names are not necessarily + piggybacked on the DNS namespace but may be independent of it. + + + + + + +Calhoun, et al. Standards Track [Page 16] + +RFC 3588 Diameter Based Protocol September 2003 + + + Real-time Accounting + Real-time accounting involves the processing of information on + resource usage within a defined time window. Time constraints are + typically imposed in order to limit financial risk. + + Relay Agent or Relay + Relays forward requests and responses based on routing-related + AVPs and realm routing table entries. Since relays do not make + policy decisions, they do not examine or alter non-routing AVPs. + As a result, relays never originate messages, do not need to + understand the semantics of messages or non-routing AVPs, and are + capable of handling any Diameter application or message type. + Since relays make decisions based on information in routing AVPs + and realm forwarding tables they do not keep state on NAS resource + usage or sessions in progress. + + Redirect Agent + Rather than forwarding requests and responses between clients and + servers, redirect agents refer clients to servers and allow them + to communicate directly. Since redirect agents do not sit in the + forwarding path, they do not alter any AVPs transiting between + client and server. Redirect agents do not originate messages and + are capable of handling any message type, although they may be + configured only to redirect messages of certain types, while + acting as relay or proxy agents for other types. As with proxy + agents, redirect agents do not keep state with respect to sessions + or NAS resources. + + Roaming Relationships + Roaming relationships include relationships between companies and + ISPs, relationships among peer ISPs within a roaming consortium, + and relationships between an ISP and a roaming consortium. + + Security Association + A security association is an association between two endpoints in + a Diameter session which allows the endpoints to communicate with + integrity and confidentially, even in the presence of relays + and/or proxies. + + Session + A session is a related progression of events devoted to a + particular activity. Each application SHOULD provide guidelines + as to when a session begins and ends. All Diameter packets with + the same Session-Identifier are considered to be part of the same + session. + + + + + + +Calhoun, et al. Standards Track [Page 17] + +RFC 3588 Diameter Based Protocol September 2003 + + + Session state + A stateful agent is one that maintains session state information, + by keeping track of all authorized active sessions. Each + authorized session is bound to a particular service, and its state + is considered active either until it is notified otherwise, or by + expiration. + + Sub-session + A sub-session represents a distinct service (e.g., QoS or data + characteristics) provided to a given session. These services may + happen concurrently (e.g., simultaneous voice and data transfer + during the same session) or serially. These changes in sessions + are tracked with the Accounting-Sub-Session-Id. + + Transaction state + The Diameter protocol requires that agents maintain transaction + state, which is used for failover purposes. Transaction state + implies that upon forwarding a request, the Hop-by-Hop identifier + is saved; the field is replaced with a locally unique identifier, + which is restored to its original value when the corresponding + answer is received. The request's state is released upon receipt + of the answer. A stateless agent is one that only maintains + transaction state. + + Translation Agent + A translation agent is a stateful Diameter node that performs + protocol translation between Diameter and another AAA protocol, + such as RADIUS. + + Transport Connection + A transport connection is a TCP or SCTP connection existing + directly between two Diameter peers, otherwise known as a Peer- + to-Peer Connection. + + Upstream + Upstream is used to identify the direction of a particular + Diameter message from the access device towards the home server. + + User + The entity requesting or using some resource, in support of which + a Diameter client has generated a request. + +2. Protocol Overview + + The base Diameter protocol may be used by itself for accounting + applications, but for use in authentication and authorization it is + always extended for a particular application. Two Diameter + applications are defined by companion documents: NASREQ [NASREQ], + + + +Calhoun, et al. Standards Track [Page 18] + +RFC 3588 Diameter Based Protocol September 2003 + + + Mobile IPv4 [DIAMMIP]. These applications are introduced in this + document but specified elsewhere. Additional Diameter applications + MAY be defined in the future (see Section 11.3). + + Diameter Clients MUST support the base protocol, which includes + accounting. In addition, they MUST fully support each Diameter + application that is needed to implement the client's service, e.g., + NASREQ and/or Mobile IPv4. A Diameter Client that does not support + both NASREQ and Mobile IPv4, MUST be referred to as "Diameter X + Client" where X is the application which it supports, and not a + "Diameter Client". + + Diameter Servers MUST support the base protocol, which includes + accounting. In addition, they MUST fully support each Diameter + application that is needed to implement the intended service, e.g., + NASREQ and/or Mobile IPv4. A Diameter Server that does not support + both NASREQ and Mobile IPv4, MUST be referred to as "Diameter X + Server" where X is the application which it supports, and not a + "Diameter Server". + + Diameter Relays and redirect agents are, by definition, protocol + transparent, and MUST transparently support the Diameter base + protocol, which includes accounting, and all Diameter applications. + + Diameter proxies MUST support the base protocol, which includes + accounting. In addition, they MUST fully support each Diameter + application that is needed to implement proxied services, e.g., + NASREQ and/or Mobile IPv4. A Diameter proxy which does not support + also both NASREQ and Mobile IPv4, MUST be referred to as "Diameter X + Proxy" where X is the application which it supports, and not a + "Diameter Proxy". + + The base Diameter protocol concerns itself with capabilities + negotiation, how messages are sent and how peers may eventually be + abandoned. The base protocol also defines certain rules that apply + to all exchanges of messages between Diameter nodes. + + 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 Diameter application. One AVP + that is included to reference a user's session is the Session-Id. + + The initial request for authentication and/or authorization of a user + would include the Session-Id. The Session-Id is then used in all + subsequent messages to identify the user's session (see Section 8 for + more information). The communicating party may accept the request, + or reject it by returning an answer message with the Result-Code AVP + + + + +Calhoun, et al. Standards Track [Page 19] + +RFC 3588 Diameter Based Protocol September 2003 + + + set to indicate an error occurred. The specific behavior of the + Diameter server or client receiving a request depends on the Diameter + application employed. + + Session state (associated with a Session-Id) MUST be freed upon + receipt of the Session-Termination-Request, Session-Termination- + Answer, expiration of authorized service time in the Session-Timeout + AVP, and according to rules established in a particular Diameter + application. + +2.1. Transport + + Transport profile is defined in [AAATRANS]. + + The base Diameter protocol is run on port 3868 of both TCP [TCP] and + SCTP [SCTP] transport protocols. + + Diameter clients MUST support either TCP or SCTP, while agents and + servers MUST support both. Future versions of this specification MAY + mandate that clients support SCTP. + + A Diameter node MAY initiate connections from a source port other + than the one that it declares it accepts incoming connections on, and + MUST be prepared to receive connections on port 3868. A given + Diameter instance of the peer state machine MUST NOT use more than + one transport connection to communicate with a given peer, unless + multiple instances exist on the peer in which case a separate + connection per process is allowed. + + When no transport connection exists with a peer, an attempt to + connect SHOULD be periodically made. This behavior is handled via + the Tc timer, whose recommended value is 30 seconds. There are + certain exceptions to this rule, such as when a peer has terminated + the transport connection stating that it does not wish to + communicate. + + When connecting to a peer and either zero or more transports are + specified, SCTP SHOULD be tried first, followed by TCP. See Section + 5.2 for more information on peer discovery. + + Diameter implementations SHOULD be able to interpret ICMP protocol + port unreachable messages as explicit indications that the server is + not reachable, subject to security policy on trusting such messages. + Diameter implementations SHOULD also be able to interpret a reset + from the transport and timed-out connection attempts. + + + + + + +Calhoun, et al. Standards Track [Page 20] + +RFC 3588 Diameter Based Protocol September 2003 + + + If Diameter receives data up from TCP that cannot be parsed or + identified as a Diameter error made by the peer, the stream is + compromised and cannot be recovered. The transport connection MUST + be closed using a RESET call (send a TCP RST bit) or an SCTP ABORT + message (graceful closure is compromised). + +2.1.1. SCTP Guidelines + + The following are guidelines for Diameter implementations that + support SCTP: + + 1. For interoperability: All Diameter nodes MUST be prepared to + receive Diameter messages on any SCTP stream in the association. + + 2. To prevent blocking: All Diameter nodes SHOULD utilize all SCTP + streams available to the association to prevent head-of-the-line + blocking. + +2.2. Securing Diameter Messages + + Diameter clients, such as Network Access Servers (NASes) and Mobility + Agents MUST support IP Security [SECARCH], and MAY support TLS [TLS]. + Diameter servers MUST support TLS and IPsec. The Diameter protocol + MUST NOT be used without any security mechanism (TLS or IPsec). + + It is suggested that IPsec can be used primarily at the edges and in + intra-domain traffic, such as using pre-shared keys between a NAS a + local AAA proxy. This also eases the requirements on the NAS to + support certificates. It is also suggested that inter-domain traffic + would primarily use TLS. See Sections 13.1 and 13.2 for more details + on IPsec and TLS usage. + +2.3. Diameter Application Compliance + + Application Identifiers are advertised during the capabilities + exchange phase (see Section 5.3). For a given application, + advertising support of an application implies that the sender + supports all command codes, and the AVPs specified in the associated + ABNFs, described in the specification. + + An implementation MAY add arbitrary non-mandatory AVPs to any command + defined in an application, including vendor-specific AVPs. Please + refer to Section 11.1.1 for details. + + + + + + + + +Calhoun, et al. Standards Track [Page 21] + +RFC 3588 Diameter Based Protocol September 2003 + + +2.4. Application Identifiers + + Each Diameter application MUST have an IANA assigned Application + Identifier (see Section 11.3). The base protocol does not require an + Application Identifier since its support is mandatory. During the + capabilities exchange, Diameter nodes inform their peers of locally + supported applications. Furthermore, all Diameter messages contain + an Application Identifier, which is used in the message forwarding + process. + + The following Application Identifier values are defined: + + Diameter Common Messages 0 + NASREQ 1 [NASREQ] + Mobile-IP 2 [DIAMMIP] + Diameter Base Accounting 3 + Relay 0xffffffff + + Relay and redirect agents MUST advertise the Relay Application + Identifier, while all other Diameter nodes MUST advertise locally + supported applications. The receiver of a Capabilities Exchange + message advertising Relay service MUST assume that the sender + supports all current and future applications. + + Diameter relay and proxy agents are responsible for finding an + upstream server that supports the application of a particular + message. If none can be found, an error message is returned with the + Result-Code AVP set to DIAMETER_UNABLE_TO_DELIVER. + +2.5. Connections vs. Sessions + + This section attempts to provide the reader with an understanding of + the difference between connection and session, which are terms used + extensively throughout this document. + + A connection is a transport level connection between two peers, used + to send and receive Diameter messages. A session is a logical + concept at the application layer, and is shared between an access + device and a server, and is identified via the Session-Id AVP + + + + + + + + + + + + +Calhoun, et al. Standards Track [Page 22] + +RFC 3588 Diameter Based Protocol September 2003 + + + +--------+ +-------+ +--------+ + | Client | | Relay | | Server | + +--------+ +-------+ +--------+ + <----------> <----------> + peer connection A peer connection B + + <-----------------------------> + User session x + + Figure 1: Diameter connections and sessions + + In the example provided in Figure 1, peer connection A is established + between the Client and its local Relay. Peer connection B is + established between the Relay and the Server. User session X spans + from the Client via the Relay to the Server. Each "user" of a + service causes an auth request to be sent, with a unique session + identifier. Once accepted by the server, both the client and the + server are aware of the session. It is important to note that there + is no relationship between a connection and a session, and that + Diameter messages for multiple sessions are all multiplexed through a + single connection. + +2.6. Peer Table + + The Diameter Peer Table is used in message forwarding, and referenced + by the Realm Routing Table. A Peer Table entry contains the + following fields: + + Host identity + Following the conventions described for the DiameterIdentity + derived AVP data format in Section 4.4. This field contains the + contents of the Origin-Host (Section 6.3) AVP found in the CER or + CEA message. + + StatusT + This is the state of the peer entry, and MUST match one of the + values listed in Section 5.6. + + Static or Dynamic + Specifies whether a peer entry was statically configured, or + dynamically discovered. + + Expiration time + Specifies the time at which dynamically discovered peer table + entries are to be either refreshed, or expired. + + + + + + +Calhoun, et al. Standards Track [Page 23] + +RFC 3588 Diameter Based Protocol September 2003 + + + TLS Enabled + Specifies whether TLS is to be used when communicating with the + peer. + + Additional security information, when needed (e.g., keys, + certificates) + +2.7. Realm-Based Routing Table + + All Realm-Based routing lookups are performed against what is + commonly known as the Realm Routing Table (see Section 12). A Realm + Routing Table Entry contains the following fields: + + Realm Name + This is the field that is typically used as a primary key in the + routing table lookups. Note that some implementations perform + their lookups based on longest-match-from-the-right on the realm + rather than requiring an exact match. + + Application Identifier + An application is identified by a vendor id and an application id. + For all IETF standards track Diameter applications, the vendor id + is zero. A route entry can have a different destination based on + the application identification AVP of the message. This field + MUST be used as a secondary key field in routing table lookups. + + Local Action + The Local Action field is used to identify how a message should be + treated. The following actions are supported: + + 1. LOCAL - Diameter messages that resolve to a route entry with + the Local Action set to Local can be satisfied locally, and do + not need to be routed to another server. + + 2. RELAY - All Diameter messages that fall within this category + MUST be routed to a next hop server, without modifying any + non-routing AVPs. See Section 6.1.8 for relaying guidelines + + 3. PROXY - All Diameter messages that fall within this category + MUST be routed to a next hop server. The local server MAY + apply its local policies to the message by including new AVPs + to the message prior to routing. See Section 6.1.8 for + proxying guidelines. + + 4. REDIRECT - Diameter messages that fall within this category + MUST have the identity of the home Diameter server(s) appended, + and returned to the sender of the message. See Section 6.1.7 + for redirect guidelines. + + + +Calhoun, et al. Standards Track [Page 24] + +RFC 3588 Diameter Based Protocol September 2003 + + + Server Identifier + One or more servers the message is to be routed to. These servers + MUST also be present in the Peer table. When the Local Action is + set to RELAY or PROXY, this field contains the identity of the + server(s) the message must be routed to. When the Local Action + field is set to REDIRECT, this field contains the identity of one + or more servers the message should be redirected to. + + Static or Dynamic + Specifies whether a route entry was statically configured, or + dynamically discovered. + + Expiration time + Specifies the time which a dynamically discovered route table + entry expires. + + It is important to note that Diameter agents MUST support at least + one of the LOCAL, RELAY, PROXY or REDIRECT modes of operation. + Agents do not need to support all modes of operation in order to + conform with the protocol specification, but MUST follow the protocol + compliance guidelines in Section 2. Relay agents MUST NOT reorder + AVPs, and proxies MUST NOT reorder AVPs. + + The routing table MAY include a default entry that MUST be used for + any requests not matching any of the other entries. The routing + table MAY consist of only such an entry. + + When a request is routed, the target server MUST have advertised the + Application Identifier (see Section 2.4) for the given message, or + have advertised itself as a relay or proxy agent. Otherwise, an + error is returned with the Result-Code AVP set to + DIAMETER_UNABLE_TO_DELIVER. + +2.8. Role of Diameter Agents + + In addition to client and servers, the Diameter protocol introduces + relay, proxy, redirect, and translation agents, each of which is + defined in Section 1.3. These Diameter agents are useful for several + reasons: + + - They can distribute administration of systems to a configurable + grouping, including the maintenance of security associations. + + - They can be used for concentration of requests from an number of + co-located or distributed NAS equipment sets to a set of like user + groups. + + - They can do value-added processing to the requests or responses. + + + +Calhoun, et al. Standards Track [Page 25] + +RFC 3588 Diameter Based Protocol September 2003 + + + - They can be used for load balancing. + + - A complex network will have multiple authentication sources, they + can sort requests and forward towards the correct target. + + The Diameter protocol requires that agents maintain transaction + state, which is used for failover purposes. Transaction state + implies that upon forwarding a request, its Hop-by-Hop identifier is + saved; the field is replaced with a locally unique identifier, which + is restored to its original value when the corresponding answer is + received. The request's state is released upon receipt of the + answer. A stateless agent is one that only maintains transaction + state. + + The Proxy-Info AVP allows stateless agents to add local state to a + Diameter request, with the guarantee that the same state will be + present in the answer. However, the protocol's failover procedures + require that agents maintain a copy of pending requests. + + A stateful agent is one that maintains session state information; by + keeping track of all authorized active sessions. Each authorized + session is bound to a particular service, and its state is considered + active either until it is notified otherwise, or by expiration. Each + authorized session has an expiration, which is communicated by + Diameter servers via the Session-Timeout AVP. + + Maintaining session state MAY be useful in certain applications, such + as: + + - Protocol translation (e.g., RADIUS <-> Diameter) + + - Limiting resources authorized to a particular user + + - Per user or transaction auditing + + A Diameter agent MAY act in a stateful manner for some requests and + be stateless for others. A Diameter implementation MAY act as one + type of agent for some requests, and as another type of agent for + others. + +2.8.1. Relay Agents + + Relay Agents are Diameter agents that accept requests and route + messages to other Diameter nodes based on information found in the + messages (e.g., Destination-Realm). This routing decision is + performed using a list of supported realms, and known peers. This is + known as the Realm Routing Table, as is defined further in Section + 2.7. + + + +Calhoun, et al. Standards Track [Page 26] + +RFC 3588 Diameter Based Protocol September 2003 + + + Relays MAY be used to aggregate requests from multiple Network Access + Servers (NASes) within a common geographical area (POP). The use of + Relays is advantageous since it eliminates the need for NASes to be + configured with the necessary security information they would + otherwise require to communicate with Diameter servers in other + realms. Likewise, this reduces the configuration load on Diameter + servers that would otherwise be necessary when NASes are added, + changed or deleted. + + Relays modify Diameter messages by inserting and removing routing + information, but do not modify any other portion of a message. + Relays SHOULD NOT maintain session state but MUST maintain + transaction state. + + +------+ ---------> +------+ ---------> +------+ + | | 1. Request | | 2. Request | | + | NAS | | DRL | | HMS | + | | 4. Answer | | 3. Answer | | + +------+ <--------- +------+ <--------- +------+ + example.net example.net example.com + + Figure 2: Relaying of Diameter messages + + The example provided in Figure 2 depicts a request issued from NAS, + which is an access device, for the user bob@example.com. Prior to + issuing the request, NAS performs a Diameter route lookup, using + "example.com" as the key, and determines that the message is to be + relayed to DRL, which is a Diameter Relay. DRL performs the same + route lookup as NAS, and relays the message to HMS, which is + example.com's Home Diameter Server. HMS identifies that the request + can be locally supported (via the realm), processes the + authentication and/or authorization request, and replies with an + answer, which is routed back to NAS using saved transaction state. + + Since Relays do not perform any application level processing, they + provide relaying services for all Diameter applications, and + therefore MUST advertise the Relay Application Identifier. + +2.8.2. Proxy Agents + + Similarly to relays, proxy agents route Diameter messages using the + Diameter Routing Table. However, they differ since they modify + messages to implement policy enforcement. This requires that proxies + maintain the state of their downstream peers (e.g., access devices) + to enforce resource usage, provide admission control, and + provisioning. + + + + + +Calhoun, et al. Standards Track [Page 27] + +RFC 3588 Diameter Based Protocol September 2003 + + + It is important to note that although proxies MAY provide a value-add + function for NASes, they do not allow access devices to use end-to- + end security, since modifying messages breaks authentication. + + Proxies MAY be used in call control centers or access ISPs that + provide outsourced connections, they can monitor the number and types + of ports in use, and make allocation and admission decisions + according to their configuration. + + Proxies that wish to limit resources MUST maintain session state. + All proxies MUST maintain transaction state. + + Since enforcing policies requires an understanding of the service + being provided, Proxies MUST only advertise the Diameter applications + they support. + +2.8.3. Redirect Agents + + Redirect agents are useful in scenarios where the Diameter routing + configuration needs to be centralized. An example is a redirect + agent that provides services to all members of a consortium, but does + not wish to be burdened with relaying all messages between realms. + This scenario is advantageous since it does not require that the + consortium provide routing updates to its members when changes are + made to a member's infrastructure. + + Since redirect agents do not relay messages, and only return an + answer with the information necessary for Diameter agents to + communicate directly, they do not modify messages. Since redirect + agents do not receive answer messages, they cannot maintain session + state. Further, since redirect agents never relay requests, they are + not required to maintain transaction state. + + The example provided in Figure 3 depicts a request issued from the + access device, NAS, for the user bob@example.com. The message is + forwarded by the NAS to its relay, DRL, which does not have a routing + entry in its Diameter Routing Table for example.com. DRL has a + default route configured to DRD, which is a redirect agent that + returns a redirect notification to DRL, as well as HMS' contact + information. Upon receipt of the redirect notification, DRL + establishes a transport connection with HMS, if one doesn't already + exist, and forwards the request to it. + + + + + + + + + +Calhoun, et al. Standards Track [Page 28] + +RFC 3588 Diameter Based Protocol September 2003 + + + +------+ + | | + | DRD | + | | + +------+ + ^ | + 2. Request | | 3. Redirection + | | Notification + | v + +------+ ---------> +------+ ---------> +------+ + | | 1. Request | | 4. Request | | + | NAS | | DRL | | HMS | + | | 6. Answer | | 5. Answer | | + +------+ <--------- +------+ <--------- +------+ + example.net example.net example.com + + Figure 3: Redirecting a Diameter Message + + Since redirect agents do not perform any application level + processing, they provide relaying services for all Diameter + applications, and therefore MUST advertise the Relay Application + Identifier. + +2.8.4. Translation Agents + + A translation agent is a device that provides translation between two + protocols (e.g., RADIUS<->Diameter, TACACS+<->Diameter). Translation + agents are likely to be used as aggregation servers to communicate + with a Diameter infrastructure, while allowing for the embedded + systems to be migrated at a slower pace. + + Given that the Diameter protocol introduces the concept of long-lived + authorized sessions, translation agents MUST be session stateful and + MUST maintain transaction state. + + Translation of messages can only occur if the agent recognizes the + application of a particular request, and therefore translation agents + MUST only advertise their locally supported applications. + + +------+ ---------> +------+ ---------> +------+ + | | RADIUS Request | | Diameter Request | | + | NAS | | TLA | | HMS | + | | RADIUS Answer | | Diameter Answer | | + +------+ <--------- +------+ <--------- +------+ + example.net example.net example.com + + Figure 4: Translation of RADIUS to Diameter + + + + +Calhoun, et al. Standards Track [Page 29] + +RFC 3588 Diameter Based Protocol September 2003 + + +2.9. End-to-End Security Framework + + End-to-end security services include confidentiality and message + origin authentication. These services are provided by supporting AVP + integrity and confidentiality between two peers, communicating + through agents. + + End-to-end security is provided via the End-to-End security + extension, described in [AAACMS]. The circumstances requiring the + use of end-to-end security are determined by policy on each of the + peers. Security policies, which are not the subject of + standardization, may be applied by next hop Diameter peer or by + destination realm. For example, where TLS or IPsec transmission- + level security is sufficient, there may be no need for end-to-end + security. + + End-to-end security policies include: + + - Never use end-to-end security. + + - Use end-to-end security on messages containing sensitive AVPs. + Which AVPs are sensitive is determined by service provider policy. + AVPs containing keys and passwords should be considered sensitive. + Accounting AVPs may be considered sensitive. Any AVP for which + the P bit may be set or which may be encrypted may be considered + sensitive. + + - Always use end-to-end security. + + It is strongly RECOMMENDED that all Diameter implementations support + end-to-end security. + +2.10. Diameter Path Authorization + + As noted in Section 2.2, Diameter requires transmission level + security to be used on each connection (TLS or IPsec). Therefore, + each connection is authenticated, replay and integrity protected and + confidential on a per-packet basis. + + In addition to authenticating each connection, each connection as + well as the entire session MUST also be authorized. Before + initiating a connection, a Diameter Peer MUST check that its peers + are authorized to act in their roles. For example, a Diameter peer + may be authentic, but that does not mean that it is authorized to act + as a Diameter Server advertising a set of Diameter applications. + + + + + + +Calhoun, et al. Standards Track [Page 30] + +RFC 3588 Diameter Based Protocol September 2003 + + + Prior to bringing up a connection, authorization checks are performed + at each connection along the path. Diameter capabilities negotiation + (CER/CEA) also MUST be carried out, in order to determine what + Diameter applications are supported by each peer. Diameter sessions + MUST be routed only through authorized nodes that have advertised + support for the Diameter application required by the session. + + As noted in Section 6.1.8, a relay or proxy agent MUST append a + Route-Record AVP to all requests forwarded. The AVP contains the + identity of the peer the request was received from. + + The home Diameter server, prior to authorizing a session, MUST check + the Route-Record AVPs to make sure that the route traversed by the + request is acceptable. For example, administrators within the home + realm may not wish to honor requests that have been routed through an + untrusted realm. By authorizing a request, the home Diameter server + is implicitly indicating its willingness to engage in the business + transaction as specified by the contractual relationship between the + server and the previous hop. A DIAMETER_AUTHORIZATION_REJECTED error + message (see Section 7.1.5) is sent if the route traversed by the + request is unacceptable. + + A home realm may also wish to check that each accounting request + message corresponds to a Diameter response authorizing the session. + Accounting requests without corresponding authorization responses + SHOULD be subjected to further scrutiny, as should accounting + requests indicating a difference between the requested and provided + service. + + Similarly, the local Diameter agent, on receiving a Diameter response + authorizing a session, MUST check the Route-Record AVPs to make sure + that the route traversed by the response is acceptable. At each + step, forwarding of an authorization response is considered evidence + of a willingness to take on financial risk relative to the session. + A local realm may wish to limit this exposure, for example, by + establishing credit limits for intermediate realms and refusing to + accept responses which would violate those limits. By issuing an + accounting request corresponding to the authorization response, the + local realm implicitly indicates its agreement to provide the service + indicated in the authorization response. If the service cannot be + provided by the local realm, then a DIAMETER_UNABLE_TO_COMPLY error + message MUST be sent within the accounting request; a Diameter client + receiving an authorization response for a service that it cannot + perform MUST NOT substitute an alternate service, and then send + accounting requests for the alternate service instead. + + + + + + +Calhoun, et al. Standards Track [Page 31] + +RFC 3588 Diameter Based Protocol September 2003 + + +3. Diameter Header + + A summary of the Diameter header format is shown below. The fields + are transmitted 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 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Version | Message Length | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | command flags | Command-Code | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Application-ID | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Hop-by-Hop Identifier | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | End-to-End Identifier | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | AVPs ... + +-+-+-+-+-+-+-+-+-+-+-+-+- + + Version + This Version field MUST be set to 1 to indicate Diameter Version + 1. + + Message Length + The Message Length field is three octets and indicates the length + of the Diameter message including the header fields. + + Command Flags + The Command Flags field is eight bits. The following bits are + assigned: + + 0 1 2 3 4 5 6 7 + +-+-+-+-+-+-+-+-+ + |R P E T r r r r| + +-+-+-+-+-+-+-+-+ + + R(equest) - If set, the message is a request. If cleared, the + message is an answer. + P(roxiable) - If set, the message MAY be proxied, relayed or + redirected. If cleared, the message MUST be + locally processed. + E(rror) - If set, the message contains a protocol error, + and the message will not conform to the ABNF + described for this command. Messages with the 'E' + + + + + +Calhoun, et al. Standards Track [Page 32] + +RFC 3588 Diameter Based Protocol September 2003 + + + bit set are commonly referred to as error + messages. This bit MUST NOT be set in request + messages. See Section 7.2. + T(Potentially re-transmitted message) + - This flag is set after a link failover procedure, + to aid the removal of duplicate requests. It is + set when resending requests not yet acknowledged, + as an indication of a possible duplicate due to a + link failure. This bit MUST be cleared when + sending a request for the first time, otherwise + the sender MUST set this flag. Diameter agents + only need to be concerned about the number of + requests they send based on a single received + request; retransmissions by other entities need + not be tracked. Diameter agents that receive a + request with the T flag set, MUST keep the T flag + set in the forwarded request. This flag MUST NOT + be set if an error answer message (e.g., a + protocol error) has been received for the earlier + message. It can be set only in cases where no + answer has been received from the server for a + request and the request is sent again. This flag + MUST NOT be set in answer messages. + + r(eserved) - these flag bits are reserved for future use, and + MUST be set to zero, and ignored by the receiver. + + Command-Code + The Command-Code field is three octets, and is used in order to + communicate the command associated with the message. The 24-bit + address space is managed by IANA (see Section 11.2.1). + + Command-Code values 16,777,214 and 16,777,215 (hexadecimal values + FFFFFE -FFFFFF) are reserved for experimental use (See Section + 11.3). + + Application-ID + Application-ID is four octets and is used to identify to which + application the message is applicable for. The application can be + an authentication application, an accounting application or a + vendor specific application. See Section 11.3 for the possible + values that the application-id may use. + + The application-id in the header MUST be the same as what is + contained in any relevant AVPs contained in the message. + + + + + + +Calhoun, et al. Standards Track [Page 33] + +RFC 3588 Diameter Based Protocol September 2003 + + + Hop-by-Hop Identifier + The Hop-by-Hop Identifier is an unsigned 32-bit integer field (in + network byte order) and aids in matching requests and replies. + The sender MUST ensure that the Hop-by-Hop identifier in a request + is unique on a given connection at any given time, and MAY attempt + to ensure that the number is unique across reboots. The sender of + an Answer message MUST ensure that the Hop-by-Hop Identifier field + contains the same value that was found in the corresponding + request. The Hop-by-Hop identifier is normally a monotonically + increasing number, whose start value was randomly generated. An + answer message that is received with an unknown Hop-by-Hop + Identifier MUST be discarded. + + End-to-End Identifier + The End-to-End Identifier is an unsigned 32-bit integer field (in + network byte order) and is used to detect duplicate messages. + Upon reboot implementations MAY set the high order 12 bits to + contain the low order 12 bits of current time, and the low order + 20 bits to a random value. Senders of request messages MUST + insert a unique identifier on each message. The identifier MUST + remain locally unique for a period of at least 4 minutes, even + across reboots. The originator of an Answer message MUST ensure + that the End-to-End Identifier field contains the same value that + was found in the corresponding request. The End-to-End Identifier + MUST NOT be modified by Diameter agents of any kind. The + combination of the Origin-Host (see Section 6.3) and this field is + used to detect duplicates. Duplicate requests SHOULD cause the + same answer to be transmitted (modulo the hop-by-hop Identifier + field and any routing AVPs that may be present), and MUST NOT + affect any state that was set when the original request was + processed. Duplicate answer messages that are to be locally + consumed (see Section 6.2) SHOULD be silently discarded. + + AVPs + AVPs are a method of encapsulating information relevant to the + Diameter message. See Section 4 for more information on AVPs. + + + + + + + + + + + + + + + +Calhoun, et al. Standards Track [Page 34] + +RFC 3588 Diameter Based Protocol September 2003 + + +3.1. Command Codes + + Each command Request/Answer pair is assigned a command code, and the + sub-type (i.e., request or answer) is identified via the 'R' bit in + the Command Flags field of the Diameter header. + + Every Diameter message MUST contain a command code in its header's + Command-Code field, which is used to determine the action that is to + be taken for a particular message. The following Command Codes are + defined in the Diameter base protocol: + + Command-Name Abbrev. Code Reference + -------------------------------------------------------- + Abort-Session-Request ASR 274 8.5.1 + Abort-Session-Answer ASA 274 8.5.2 + Accounting-Request ACR 271 9.7.1 + Accounting-Answer ACA 271 9.7.2 + Capabilities-Exchange- CER 257 5.3.1 + Request + Capabilities-Exchange- CEA 257 5.3.2 + Answer + Device-Watchdog-Request DWR 280 5.5.1 + Device-Watchdog-Answer DWA 280 5.5.2 + Disconnect-Peer-Request DPR 282 5.4.1 + Disconnect-Peer-Answer DPA 282 5.4.2 + Re-Auth-Request RAR 258 8.3.1 + Re-Auth-Answer RAA 258 8.3.2 + Session-Termination- STR 275 8.4.1 + Request + Session-Termination- STA 275 8.4.2 + Answer + + + + + + + + + + + + + + + + + + + + +Calhoun, et al. Standards Track [Page 35] + +RFC 3588 Diameter Based Protocol September 2003 + + +3.2. Command Code ABNF specification + + Every Command Code defined MUST include a corresponding ABNF + specification, which is used to define the AVPs that MUST or MAY be + present. The following format is used in the definition: + + command-def = command-name "::=" diameter-message + + command-name = diameter-name + + diameter-name = ALPHA *(ALPHA / DIGIT / "-") + + diameter-message = header [ *fixed] [ *required] [ *optional] + [ *fixed] + + header = "<" Diameter-Header:" command-id + [r-bit] [p-bit] [e-bit] [application-id]">" + + application-id = 1*DIGIT + + command-id = 1*DIGIT + ; The Command Code assigned to the command + + r-bit = ", REQ" + ; If present, the 'R' bit in the Command + ; Flags is set, indicating that the message + ; is a request, as opposed to an answer. + + p-bit = ", PXY" + ; If present, the 'P' bit in the Command + ; Flags is set, indicating that the message + ; is proxiable. + + e-bit = ", ERR" + ; If present, the 'E' bit in the Command + ; Flags is set, indicating that the answer + ; message contains a Result-Code AVP in + ; the "protocol error" class. + + fixed = [qual] "<" avp-spec ">" + ; Defines the fixed position of an AVP + + required = [qual] "{" avp-spec "}" + ; The AVP MUST be present and can appear + ; anywhere in the message. + + + + + + +Calhoun, et al. Standards Track [Page 36] + +RFC 3588 Diameter Based Protocol September 2003 + + + optional = [qual] "[" avp-name "]" + ; The avp-name in the 'optional' rule cannot + ; evaluate to any AVP Name which is included + ; in a fixed or required rule. The AVP can + ; appear anywhere in the message. + + qual = [min] "*" [max] + ; See ABNF conventions, RFC 2234 Section 6.6. + ; The absence of any qualifiers depends on whether + ; it precedes a fixed, required, or optional + ; rule. If a fixed or required rule has no + ; qualifier, then exactly one such AVP MUST + ; be present. If an optional rule has no + ; qualifier, then 0 or 1 such AVP may be + ; present. + ; + ; NOTE: "[" and "]" have a different meaning + ; than in ABNF (see the optional rule, above). + ; These braces cannot be used to express + ; optional fixed rules (such as an optional + ; ICV at the end). To do this, the convention + ; is '0*1fixed'. + + min = 1*DIGIT + ; The minimum number of times the element may + ; be present. The default value is zero. + + max = 1*DIGIT + ; The maximum number of times the element may + ; be present. The default value is infinity. A + ; value of zero implies the AVP MUST NOT be + ; present. + + avp-spec = diameter-name + ; The avp-spec has to be an AVP Name, defined + ; in the base or extended Diameter + ; specifications. + + avp-name = avp-spec / "AVP" + ; The string "AVP" stands for *any* arbitrary + ; AVP Name, which does not conflict with the + ; required or fixed position AVPs defined in + ; the command code definition. + + + + + + + + +Calhoun, et al. Standards Track [Page 37] + +RFC 3588 Diameter Based Protocol September 2003 + + + The following is a definition of a fictitious command code: + + Example-Request ::= < "Diameter-Header: 9999999, REQ, PXY > + { User-Name } + * { Origin-Host } + * [ AVP + +3.3. Diameter Command Naming Conventions + + Diameter command names typically includes one or more English words + followed by the verb Request or Answer. Each English word is + delimited by a hyphen. A three-letter acronym for both the request + and answer is also normally provided. + + An example is a message set used to terminate a session. The command + name is Session-Terminate-Request and Session-Terminate-Answer, while + the acronyms are STR and STA, respectively. + + Both the request and the answer for a given command share the same + command code. The request is identified by the R(equest) bit in the + Diameter header set to one (1), to ask that a particular action be + performed, such as authorizing a user or terminating a session. Once + the receiver has completed the request it issues the corresponding + answer, which includes a result code that communicates one of the + following: + + - The request was successful + + - The request failed + + - An additional request must be sent to provide information the peer + requires prior to returning a successful or failed answer. + + - The receiver could not process the request, but provides + information about a Diameter peer that is able to satisfy the + request, known as redirect. + + Additional information, encoded within AVPs, MAY also be included in + answer messages. + +4. Diameter AVPs + + Diameter AVPs carry specific authentication, accounting, + authorization, routing and security information as well as + configuration details for the request and reply. + + Some AVPs MAY be listed more than once. The effect of such an AVP is + specific, and is specified in each case by the AVP description. + + + +Calhoun, et al. Standards Track [Page 38] + +RFC 3588 Diameter Based Protocol September 2003 + + + Each AVP of type OctetString MUST be padded to align on a 32-bit + boundary, while other AVP types align naturally. A number of zero- + valued bytes are added to the end of the AVP Data field till a word + boundary is reached. The length of the padding is not reflected in + the AVP Length field. + +4.1. AVP Header + + The fields in the AVP header MUST be sent in network byte order. The + format of the header is: + + 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 | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + |V M P r r r r r| AVP Length | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Vendor-ID (opt) | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Data ... + +-+-+-+-+-+-+-+-+ + + AVP Code + The AVP Code, combined with the Vendor-Id field, identifies the + attribute uniquely. AVP numbers 1 through 255 are reserved for + backward compatibility with RADIUS, without setting the Vendor-Id + field. AVP numbers 256 and above are used for Diameter, which are + allocated by IANA (see Section 11.1). + + AVP Flags + The AVP Flags field informs the receiver how each attribute must + be handled. The 'r' (reserved) bits are unused and SHOULD be set + to 0. Note that subsequent Diameter applications MAY define + additional bits within the AVP Header, and an unrecognized bit + SHOULD be considered an error. The 'P' bit indicates the need for + encryption for end-to-end security. + + The 'M' Bit, known as the Mandatory bit, indicates whether support + of the AVP is required. If an AVP with the 'M' bit set is + received by a Diameter client, server, proxy, or translation agent + and either the AVP or its value is unrecognized, the message MUST + be rejected. Diameter Relay and redirect agents MUST NOT reject + messages with unrecognized AVPs. + + + + + + + +Calhoun, et al. Standards Track [Page 39] + +RFC 3588 Diameter Based Protocol September 2003 + + + The 'M' bit MUST be set according to the rules defined for the AVP + containing it. In order to preserve interoperability, a Diameter + implementation MUST be able to exclude from a Diameter message any + Mandatory AVP which is neither defined in the base Diameter + protocol nor in any of the Diameter Application specifications + governing the message in which it appears. It MAY do this in one + of the following ways: + + 1) If a message is rejected because it contains a Mandatory AVP + which is neither defined in the base Diameter standard nor in + any of the Diameter Application specifications governing the + message in which it appears, the implementation may resend the + message without the AVP, possibly inserting additional standard + AVPs instead. + + 2) A configuration option may be provided on a system wide, per + peer, or per realm basis that would allow/prevent particular + Mandatory AVPs to be sent. Thus an administrator could change + the configuration to avoid interoperability problems. + + Diameter implementations are required to support all Mandatory + AVPs which are allowed by the message's formal syntax and defined + either in the base Diameter standard or in one of the Diameter + Application specifications governing the message. + + AVPs with the 'M' bit cleared are informational only and a + receiver that receives a message with such an AVP that is not + supported, or whose value 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. + + 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. + + AVP Length + The AVP Length field is three octets, and indicates the number of + octets in this AVP including the AVP Code, AVP Length, AVP Flags, + Vendor-ID field (if present) and the AVP data. If a message is + received with an invalid attribute length, the message SHOULD be + rejected. + + + + + +Calhoun, et al. Standards Track [Page 40] + +RFC 3588 Diameter Based Protocol September 2003 + + +4.1.1. Optional Header Elements + + The AVP Header contains one optional field. This field is only + present if the respective bit-flag is enabled. + + Vendor-ID + The Vendor-ID field is present if 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" + [ASSIGNNO] value, encoded in network byte order. Any vendor + wishing to implement a vendor-specific Diameter AVP MUST use their + own Vendor-ID along with their privately managed AVP address + space, guaranteeing that they will not collide with any other + vendor's vendor-specific AVP(s), nor with future IETF + applications. + + 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 MUST NOT use the zero (0) vendor ID. + +4.2. Basic AVP Data 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. The format of + the Data field MUST be one of the following base data types or a data + type derived from the base data types. In the event that a new Basic + AVP Data Format is needed, a new version of this RFC must be created. + + OctetString + The data contains arbitrary data of variable length. Unless + otherwise noted, the AVP Length field MUST be set to at least 8 + (12 if the 'V' bit is enabled). AVP Values of this type that are + not a multiple of four-octets in length is followed by the + necessary padding so that the next AVP (if any) will start on a + 32-bit boundary. + + Integer32 + 32 bit signed value, in network byte order. The AVP Length field + MUST be set to 12 (16 if the 'V' bit is enabled). + + Integer64 + 64 bit signed value, in network byte order. The AVP Length field + MUST be set to 16 (20 if the 'V' bit is enabled). + + + + + + +Calhoun, et al. Standards Track [Page 41] + +RFC 3588 Diameter Based Protocol September 2003 + + + Unsigned32 + 32 bit unsigned value, in network byte order. The AVP Length + field MUST be set to 12 (16 if the 'V' bit is enabled). + + Unsigned64 + 64 bit unsigned value, in network byte order. The AVP Length + field MUST be set to 16 (20 if the 'V' bit is enabled). + + Float32 + This represents floating point values of single precision as + described by [FLOATPOINT]. The 32-bit value is transmitted in + network byte order. The AVP Length field MUST be set to 12 (16 if + the 'V' bit is enabled). + + Float64 + This represents floating point values of double precision as + described by [FLOATPOINT]. The 64-bit value is transmitted in + network byte order. The AVP Length field MUST be set to 16 (20 if + the 'V' bit is enabled). + + Grouped + The Data field is specified as a sequence of AVPs. Each of these + AVPs follows - in the order in which they are specified - + including their headers and padding. The AVP Length field is set + to 8 (12 if the 'V' bit is enabled) plus the total length of all + included AVPs, including their headers and padding. Thus the AVP + length field of an AVP of type Grouped is always a multiple of 4. + +4.3. Derived AVP Data Formats + + In addition to using the Basic AVP Data Formats, applications may + define data formats derived from the Basic AVP Data Formats. An + application that defines new AVP Derived Data Formats MUST include + them in a section entitled "AVP Derived Data Formats", using the same + format as the definitions below. Each new definition must be either + defined or listed with a reference to the RFC that defines the + format. + + The below AVP Derived Data Formats are commonly used by applications. + + Address + The Address format is derived from the OctetString AVP Base + Format. It is a discriminated union, representing, for example a + 32-bit (IPv4) [IPV4] or 128-bit (IPv6) [IPV6] address, most + significant octet first. The first two octets of the Address + + + + + + +Calhoun, et al. Standards Track [Page 42] + +RFC 3588 Diameter Based Protocol September 2003 + + + AVP represents the AddressType, which contains an Address Family + defined in [IANAADFAM]. The AddressType is used to discriminate + the content and format of the remaining octets. + + Time + The Time format is derived from the OctetString AVP Base Format. + The string MUST contain four octets, in the same format as the + first four bytes are in the NTP timestamp format. The NTP + Timestamp format is defined in chapter 3 of [SNTP]. + + This represents the number of seconds since 0h on 1 January 1900 + with respect to the Coordinated Universal Time (UTC). + + On 6h 28m 16s UTC, 7 February 2036 the time value will overflow. + SNTP [SNTP] describes a procedure to extend the time to 2104. + This procedure MUST be supported by all DIAMETER nodes. + + UTF8String + The UTF8String format is derived from the OctetString AVP Base + Format. This is a human readable string represented using the + ISO/IEC IS 10646-1 character set, encoded as an OctetString using + the UTF-8 [UFT8] transformation format described in RFC 2279. + + Since additional code points are added by amendments to the 10646 + standard from time to time, implementations MUST be prepared to + encounter any code point from 0x00000001 to 0x7fffffff. Byte + sequences that do not correspond to the valid encoding of a code + point into UTF-8 charset or are outside this range are prohibited. + + The use of control codes SHOULD be avoided. When it is necessary + to represent a new line, the control code sequence CR LF SHOULD be + used. + + The use of leading or trailing white space SHOULD be avoided. + + For code points not directly supported by user interface hardware + or software, an alternative means of entry and display, such as + hexadecimal, MAY be provided. + + For information encoded in 7-bit US-ASCII, the UTF-8 charset is + identical to the US-ASCII charset. + + UTF-8 may require multiple bytes to represent a single character / + code point; thus the length of an UTF8String in octets may be + different from the number of characters encoded. + + Note that the AVP Length field of an UTF8String is measured in + octets, not characters. + + + +Calhoun, et al. Standards Track [Page 43] + +RFC 3588 Diameter Based Protocol September 2003 + + + DiameterIdentity + The DiameterIdentity format is derived from the OctetString AVP + Base Format. + + DiameterIdentity = FQDN + + DiameterIdentity value is used to uniquely identify a Diameter + node for purposes of duplicate connection and routing loop + detection. + + The contents of the string MUST be the FQDN of the Diameter node. + If multiple Diameter nodes run on the same host, each Diameter + node MUST be assigned a unique DiameterIdentity. If a Diameter + node can be identified by several FQDNs, a single FQDN should be + picked at startup, and used as the only DiameterIdentity for that + node, whatever the connection it is sent on. + + DiameterURI + + The DiameterURI MUST follow the Uniform Resource Identifiers (URI) + syntax [URI] rules specified below: + + "aaa://" FQDN [ port ] [ transport ] [ protocol ] + + ; No transport security + + "aaas://" FQDN [ port ] [ transport ] [ protocol ] + + ; Transport security used + + FQDN = Fully Qualified Host Name + + port = ":" 1*DIGIT + + ; One of the ports used to listen for + ; incoming connections. + ; If absent, + ; the default Diameter port (3868) is + ; assumed. + + transport = ";transport=" transport-protocol + + ; One of the transports used to listen + ; for incoming connections. If absent, + ; the default SCTP [SCTP] protocol is + ; assumed. UDP MUST NOT be used when + ; the aaa-protocol field is set to + ; diameter. + + + +Calhoun, et al. Standards Track [Page 44] + +RFC 3588 Diameter Based Protocol September 2003 + + + transport-protocol = ( "tcp" / "sctp" / "udp" ) + + protocol = ";protocol=" aaa-protocol + + ; If absent, the default AAA protocol + ; is diameter. + + aaa-protocol = ( "diameter" / "radius" / "tacacs+" ) + + The following are examples of valid Diameter host identities: + + aaa://host.example.com;transport=tcp + aaa://host.example.com:6666;transport=tcp + aaa://host.example.com;protocol=diameter + aaa://host.example.com:6666;protocol=diameter + aaa://host.example.com:6666;transport=tcp;protocol=diameter + aaa://host.example.com:1813;transport=udp;protocol=radius + + Enumerated + Enumerated is derived from the Integer32 AVP Base Format. The + definition contains a list of valid values and their + interpretation and is described in the Diameter application + introducing the AVP. + + IPFilterRule + The IPFilterRule format is derived from the OctetString AVP Base + Format. It uses the ASCII charset. Packets may be filtered based + on the following information that is associated with it: + + Direction (in or out) + Source and destination IP address (possibly masked) + Protocol + Source and destination port (lists or ranges) + TCP flags + IP fragment flag + IP options + ICMP types + + Rules for the appropriate direction are evaluated in order, with + the first matched rule terminating the evaluation. Each packet is + evaluated once. If no rule matches, the packet is dropped if the + last rule evaluated was a permit, and passed if the last rule was + a deny. + + + + + + + + +Calhoun, et al. Standards Track [Page 45] + +RFC 3588 Diameter Based Protocol September 2003 + + + IPFilterRule filters MUST follow the format: + + action dir proto from src to dst [options] + + action permit - Allow packets that match the rule. + deny - Drop packets that match the rule. + + dir "in" is from the terminal, "out" is to the + terminal. + + proto An IP protocol specified by number. The "ip" + keyword means any protocol will match. + + src and dst <address/mask> [ports] + + The <address/mask> may be specified as: + ipno An IPv4 or IPv6 number in dotted- + quad or canonical IPv6 form. Only + this exact IP number will match the + rule. + ipno/bits An IP number as above with a mask + width of the form 1.2.3.4/24. In + this case, all IP numbers from + 1.2.3.0 to 1.2.3.255 will match. + The bit width MUST be valid for the + IP version and the IP number MUST + NOT have bits set beyond the mask. + For a match to occur, the same IP + version must be present in the + packet that was used in describing + the IP address. To test for a + particular IP version, the bits part + can be set to zero. The keyword + "any" is 0.0.0.0/0 or the IPv6 + equivalent. The keyword "assigned" + is the address or set of addresses + assigned to the terminal. For IPv4, + a typical first rule is often "deny + in ip! assigned" + + The sense of the match can be inverted by + preceding an address with the not modifier (!), + causing all other addresses to be matched + instead. This does not affect the selection of + port numbers. + + + + + + +Calhoun, et al. Standards Track [Page 46] + +RFC 3588 Diameter Based Protocol September 2003 + + + With the TCP, UDP and SCTP protocols, optional + ports may be specified as: + + {port/port-port}[,ports[,...]] + + The '-' notation specifies a range of ports + (including boundaries). + + Fragmented packets that have a non-zero offset + (i.e., not the first fragment) will never match + a rule that has one or more port + specifications. See the frag option for + details on matching fragmented packets. + + options: + frag Match if the packet is a fragment and this is not + the first fragment of the datagram. frag may not + be used in conjunction with either tcpflags or + TCP/UDP port specifications. + + ipoptions spec + Match if the IP header contains the comma + separated list of options specified in spec. The + supported IP options are: + + ssrr (strict source route), lsrr (loose source + route), rr (record packet route) and ts + (timestamp). The absence of a particular option + may be denoted with a '!'. + + tcpoptions spec + Match if the TCP header contains the comma + separated list of options specified in spec. The + supported TCP options are: + + mss (maximum segment size), window (tcp window + advertisement), sack (selective ack), ts (rfc1323 + timestamp) and cc (rfc1644 t/tcp connection + count). The absence of a particular option may + be denoted with a '!'. + + established + TCP packets only. Match packets that have the RST + or ACK bits set. + + setup TCP packets only. Match packets that have the SYN + bit set but no ACK bit. + + + + +Calhoun, et al. Standards Track [Page 47] + +RFC 3588 Diameter Based Protocol September 2003 + + + tcpflags spec + TCP packets only. Match if the TCP header + contains the comma separated list of flags + specified in spec. The supported TCP flags are: + + fin, syn, rst, psh, ack and urg. The absence of a + particular flag may be denoted with a '!'. A rule + that contains a tcpflags specification can never + match a fragmented packet that has a non-zero + offset. See the frag option for details on + matching fragmented packets. + + icmptypes types + ICMP packets only. Match if the ICMP type is in + the list types. The list may be specified as any + combination of ranges or individual types + separated by commas. Both the numeric values and + the symbolic values listed below can be used. The + supported ICMP types are: + + echo reply (0), destination unreachable (3), + source quench (4), redirect (5), echo request + (8), router advertisement (9), router + solicitation (10), time-to-live exceeded (11), IP + header bad (12), timestamp request (13), + timestamp reply (14), information request (15), + information reply (16), address mask request (17) + and address mask reply (18). + + There is one kind of packet that the access device MUST always + discard, that is an IP fragment with a fragment offset of one. This + is a valid packet, but it only has one use, to try to circumvent + firewalls. + + An access device that is unable to interpret or apply a deny rule + MUST terminate the session. An access device that is unable to + interpret or apply a permit rule MAY apply a more restrictive + rule. An access device MAY apply deny rules of its own before the + supplied rules, for example to protect the access device owner's + infrastructure. + + The rule syntax is a modified subset of ipfw(8) from FreeBSD, and the + ipfw.c code may provide a useful base for implementations. + + + + + + + + +Calhoun, et al. Standards Track [Page 48] + +RFC 3588 Diameter Based Protocol September 2003 + + + QoSFilterRule + The QosFilterRule format is derived from the OctetString AVP Base + Format. It uses the ASCII charset. Packets may be marked or + metered based on the following information that is associated with + it: + + Direction (in or out) + Source and destination IP address (possibly masked) + Protocol + Source and destination port (lists or ranges) + DSCP values (no mask or range) + + Rules for the appropriate direction are evaluated in order, with + the first matched rule terminating the evaluation. Each packet is + evaluated once. If no rule matches, the packet is treated as best + effort. An access device that is unable to interpret or apply a + QoS rule SHOULD NOT terminate the session. + + QoSFilterRule filters MUST follow the format: + + action dir proto from src to dst [options] + + tag - Mark packet with a specific DSCP + [DIFFSERV]. The DSCP option MUST be + included. + meter - Meter traffic. The metering options + MUST be included. + + dir The format is as described under IPFilterRule. + + proto The format is as described under + IPFilterRule. + + src and dst The format is as described under + IPFilterRule. + +4.4. Grouped AVP Values + + The Diameter protocol allows AVP values of type 'Grouped.' This + implies that the Data field is actually a sequence of AVPs. It is + possible to include an AVP with a Grouped type within a Grouped type, + that is, to nest them. AVPs within an AVP of type Grouped have the + same padding requirements as non-Grouped AVPs, as defined in Section + 4. + + + + + + + +Calhoun, et al. Standards Track [Page 49] + +RFC 3588 Diameter Based Protocol September 2003 + + + The AVP Code numbering space of all AVPs included in a Grouped AVP is + the same as for non-grouped AVPs. Further, if any of the AVPs + encapsulated within a Grouped AVP has the 'M' (mandatory) bit set, + the Grouped AVP itself MUST also include the 'M' bit set. + + Every Grouped AVP defined MUST include a corresponding grammar, using + ABNF [ABNF] (with modifications), as defined below. + + grouped-avp-def = name "::=" avp + + name-fmt = ALPHA *(ALPHA / DIGIT / "-") + + name = name-fmt + ; The name has to be the name of an AVP, + ; defined in the base or extended Diameter + ; specifications. + + avp = header [ *fixed] [ *required] [ *optional] + [ *fixed] + + header = "<" "AVP-Header:" avpcode [vendor] ">" + + avpcode = 1*DIGIT + ; The AVP Code assigned to the Grouped AVP + + vendor = 1*DIGIT + ; The Vendor-ID assigned to the Grouped AVP. + ; If absent, the default value of zero is + ; used. + +4.4.1. Example AVP with a Grouped Data type + + The Example-AVP (AVP Code 999999) is of type Grouped and is used to + clarify how Grouped AVP values work. The Grouped Data field has the + following ABNF grammar: + + Example-AVP ::= < AVP Header: 999999 > + { Origin-Host } + 1*{ Session-Id } + *[ AVP ] + + An Example-AVP with Grouped Data follows. + + The Origin-Host AVP is required (Section 6.3). In this case: + + Origin-Host = "example.com". + + + + + +Calhoun, et al. Standards Track [Page 50] + +RFC 3588 Diameter Based Protocol September 2003 + + + One or more Session-Ids must follow. Here there are two: + + Session-Id = + "grump.example.com:33041;23432;893;0AF3B81" + + Session-Id = + "grump.example.com:33054;23561;2358;0AF3B82" + + optional AVPs included are + + Recovery-Policy = <binary> + 2163bc1d0ad82371f6bc09484133c3f09ad74a0dd5346d54195a7cf0b35 + 2cabc881839a4fdcfbc1769e2677a4c1fb499284c5f70b48f58503a45c5 + c2d6943f82d5930f2b7c1da640f476f0e9c9572a50db8ea6e51e1c2c7bd + f8bb43dc995144b8dbe297ac739493946803e1cee3e15d9b765008a1b2a + cf4ac777c80041d72c01e691cf751dbf86e85f509f3988e5875dc905119 + 26841f00f0e29a6d1ddc1a842289d440268681e052b30fb638045f7779c + 1d873c784f054f688f5001559ecff64865ef975f3e60d2fd7966b8c7f92 + + Futuristic-Acct-Record = <binary> + fe19da5802acd98b07a5b86cb4d5d03f0314ab9ef1ad0b67111ff3b90a0 + 57fe29620bf3585fd2dd9fcc38ce62f6cc208c6163c008f4258d1bc88b8 + 17694a74ccad3ec69269461b14b2e7a4c111fb239e33714da207983f58c + 41d018d56fe938f3cbf089aac12a912a2f0d1923a9390e5f789cb2e5067 + d3427475e49968f841 + + The data for the optional AVPs is represented in hex since the format + of these AVPs is neither known at the time of definition of the + Example-AVP group, nor (likely) at the time when the example instance + of this AVP is interpreted - except by Diameter implementations which + support the same set of AVPs. The encoding example illustrates how + padding is used and how length fields are calculated. Also note that + AVPs may be present in the Grouped AVP value which the receiver + cannot interpret (here, the Recover-Policy and Futuristic-Acct-Record + AVPs). + + + + + + + + + + + + + + + + +Calhoun, et al. Standards Track [Page 51] + +RFC 3588 Diameter Based Protocol September 2003 + + + This AVP would be encoded as follows: + + 0 1 2 3 4 5 6 7 + +-------+-------+-------+-------+-------+-------+-------+-------+ + 0 | Example AVP Header (AVP Code = 999999), Length = 468 | + +-------+-------+-------+-------+-------+-------+-------+-------+ + 8 | Origin-Host AVP Header (AVP Code = 264), Length = 19 | + +-------+-------+-------+-------+-------+-------+-------+-------+ + 16 | 'e' | 'x' | 'a' | 'm' | 'p' | 'l' | 'e' | '.' | + +-------+-------+-------+-------+-------+-------+-------+-------+ + 24 | 'c' | 'o' | 'm' |Padding| Session-Id AVP Header | + +-------+-------+-------+-------+-------+-------+-------+-------+ + 32 | (AVP Code = 263), Length = 50 | 'g' | 'r' | 'u' | 'm' | + +-------+-------+-------+-------+-------+-------+-------+-------+ + . . . + +-------+-------+-------+-------+-------+-------+-------+-------+ + 64 | 'A' | 'F' | '3' | 'B' | '8' | '1' |Padding|Padding| + +-------+-------+-------+-------+-------+-------+-------+-------+ + 72 | Session-Id AVP Header (AVP Code = 263), Length = 51 | + +-------+-------+-------+-------+-------+-------+-------+-------+ + 80 | 'g' | 'r' | 'u' | 'm' | 'p' | '.' | 'e' | 'x' | + +-------+-------+-------+-------+-------+-------+-------+-------+ + . . . + +-------+-------+-------+-------+-------+-------+-------+-------+ + 104 | '0' | 'A' | 'F' | '3' | 'B' | '8' | '2' |Padding| + +-------+-------+-------+-------+-------+-------+-------+-------+ + 112 | Recovery-Policy Header (AVP Code = 8341), Length = 223 | + +-------+-------+-------+-------+-------+-------+-------+-------+ + 120 | 0x21 | 0x63 | 0xbc | 0x1d | 0x0a | 0xd8 | 0x23 | 0x71 | + +-------+-------+-------+-------+-------+-------+-------+-------+ + . . . + +-------+-------+-------+-------+-------+-------+-------+-------+ + 320 | 0x2f | 0xd7 | 0x96 | 0x6b | 0x8c | 0x7f | 0x92 |Padding| + +-------+-------+-------+-------+-------+-------+-------+-------+ + 328 | Futuristic-Acct-Record Header (AVP Code = 15930), Length = 137| + +-------+-------+-------+-------+-------+-------+-------+-------+ + 336 | 0xfe | 0x19 | 0xda | 0x58 | 0x02 | 0xac | 0xd9 | 0x8b | + +-------+-------+-------+-------+-------+-------+-------+-------+ + . . . + +-------+-------+-------+-------+-------+-------+-------+-------+ + 464 | 0x41 |Padding|Padding|Padding| + +-------+-------+-------+-------+ + + + + + + + + + +Calhoun, et al. Standards Track [Page 52] + +RFC 3588 Diameter Based Protocol September 2003 + + +4.5. 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. For the originator of a Diameter + message, "Encr" (Encryption) means that if a message containing that + AVP is to be sent via a Diameter agent (proxy, redirect or relay) + then the message MUST NOT be sent unless there is end-to-end security + between the originator and the recipient and integrity / + confidentiality protection is offered for this AVP OR the originator + has locally trusted configuration that indicates that end-to-end + security is not needed. Similarly, for the originator of a Diameter + message, a "P" in the "MAY" column means that if a message containing + that AVP is to be sent via a Diameter agent (proxy, redirect or + relay) then the message MUST NOT be sent unless there is end-to-end + security between the originator and the recipient or the originator + has locally trusted configuration that indicates that end-to-end + security is not needed. + + Due to space constraints, the short form DiamIdent is used to + represent DiameterIdentity. + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +Calhoun, et al. Standards Track [Page 53] + +RFC 3588 Diameter Based Protocol September 2003 + + + +---------------------+ + | AVP Flag rules | + |----+-----+----+-----|----+ + AVP Section | | |SHLD| MUST| | + Attribute Name Code Defined Data Type |MUST| MAY | NOT| NOT|Encr| + -----------------------------------------|----+-----+----+-----|----| + Acct- 85 9.8.2 Unsigned32 | M | P | | V | Y | + Interim-Interval | | | | | | + Accounting- 483 9.8.7 Enumerated | M | P | | V | Y | + Realtime-Required | | | | | | + Acct- 50 9.8.5 UTF8String | M | P | | V | Y | + Multi-Session-Id | | | | | | + Accounting- 485 9.8.3 Unsigned32 | M | P | | V | Y | + Record-Number | | | | | | + Accounting- 480 9.8.1 Enumerated | M | P | | V | Y | + Record-Type | | | | | | + Accounting- 44 9.8.4 OctetString| M | P | | V | Y | + Session-Id | | | | | | + Accounting- 287 9.8.6 Unsigned64 | M | P | | V | Y | + Sub-Session-Id | | | | | | + Acct- 259 6.9 Unsigned32 | M | P | | V | N | + Application-Id | | | | | | + Auth- 258 6.8 Unsigned32 | M | P | | V | N | + Application-Id | | | | | | + Auth-Request- 274 8.7 Enumerated | M | P | | V | N | + Type | | | | | | + Authorization- 291 8.9 Unsigned32 | M | P | | V | N | + Lifetime | | | | | | + Auth-Grace- 276 8.10 Unsigned32 | M | P | | V | N | + Period | | | | | | + Auth-Session- 277 8.11 Enumerated | M | P | | V | N | + State | | | | | | + Re-Auth-Request- 285 8.12 Enumerated | M | P | | V | N | + Type | | | | | | + Class 25 8.20 OctetString| M | P | | V | Y | + Destination-Host 293 6.5 DiamIdent | M | P | | V | N | + Destination- 283 6.6 DiamIdent | M | P | | V | N | + Realm | | | | | | + Disconnect-Cause 273 5.4.3 Enumerated | M | P | | V | N | + E2E-Sequence AVP 300 6.15 Grouped | M | P | | V | Y | + Error-Message 281 7.3 UTF8String | | P | | V,M | N | + Error-Reporting- 294 7.4 DiamIdent | | P | | V,M | N | + Host | | | | | | + Event-Timestamp 55 8.21 Time | M | P | | V | N | + Experimental- 297 7.6 Grouped | M | P | | V | N | + Result | | | | | | + -----------------------------------------|----+-----+----+-----|----| + + + + +Calhoun, et al. Standards Track [Page 54] + +RFC 3588 Diameter Based Protocol September 2003 + + + +---------------------+ + | AVP Flag rules | + |----+-----+----+-----|----+ + AVP Section | | |SHLD| MUST|MAY | + Attribute Name Code Defined Data Type |MUST| MAY | NOT| NOT|Encr| + -----------------------------------------|----+-----+----+-----|----| + Experimental- 298 7.7 Unsigned32 | M | P | | V | N | + Result-Code | | | | | | + Failed-AVP 279 7.5 Grouped | M | P | | V | N | + Firmware- 267 5.3.4 Unsigned32 | | | |P,V,M| N | + Revision | | | | | | + Host-IP-Address 257 5.3.5 Address | M | P | | V | N | + Inband-Security | M | P | | V | N | + -Id 299 6.10 Unsigned32 | | | | | | + Multi-Round- 272 8.19 Unsigned32 | M | P | | V | Y | + Time-Out | | | | | | + Origin-Host 264 6.3 DiamIdent | M | P | | V | N | + Origin-Realm 296 6.4 DiamIdent | M | P | | V | N | + Origin-State-Id 278 8.16 Unsigned32 | M | P | | V | N | + Product-Name 269 5.3.7 UTF8String | | | |P,V,M| N | + Proxy-Host 280 6.7.3 DiamIdent | M | | | P,V | N | + Proxy-Info 284 6.7.2 Grouped | M | | | P,V | N | + Proxy-State 33 6.7.4 OctetString| M | | | P,V | N | + Redirect-Host 292 6.12 DiamURI | M | P | | V | N | + Redirect-Host- 261 6.13 Enumerated | M | P | | V | N | + Usage | | | | | | + Redirect-Max- 262 6.14 Unsigned32 | M | P | | V | N | + Cache-Time | | | | | | + Result-Code 268 7.1 Unsigned32 | M | P | | V | N | + Route-Record 282 6.7.1 DiamIdent | M | | | P,V | N | + Session-Id 263 8.8 UTF8String | M | P | | V | Y | + Session-Timeout 27 8.13 Unsigned32 | M | P | | V | N | + Session-Binding 270 8.17 Unsigned32 | M | P | | V | Y | + Session-Server- 271 8.18 Enumerated | M | P | | V | Y | + Failover | | | | | | + Supported- 265 5.3.6 Unsigned32 | M | P | | V | N | + Vendor-Id | | | | | | + Termination- 295 8.15 Enumerated | M | P | | V | N | + Cause | | | | | | + User-Name 1 8.14 UTF8String | M | P | | V | Y | + Vendor-Id 266 5.3.3 Unsigned32 | M | P | | V | N | + Vendor-Specific- 260 6.11 Grouped | M | P | | V | N | + Application-Id | | | | | | + -----------------------------------------|----+-----+----+-----|----| + + + + + + + +Calhoun, et al. Standards Track [Page 55] + +RFC 3588 Diameter Based Protocol September 2003 + + +5. Diameter Peers + + This section describes how Diameter nodes establish connections and + communicate with peers. + +5.1. Peer Connections + + Although a Diameter node may have many possible peers that it is able + to communicate with, it may not be economical to have an established + connection to all of them. At a minimum, a Diameter node SHOULD have + an established connection with two peers per realm, known as the + primary and secondary peers. Of course, a node MAY have additional + connections, if it is deemed necessary. Typically, all messages for + a realm are sent to the primary peer, but in the event that failover + procedures are invoked, any pending requests are sent to the + secondary peer. However, implementations are free to load balance + requests between a set of peers. + + Note that a given peer MAY act as a primary for a given realm, while + acting as a secondary for another realm. + + When a peer is deemed suspect, which could occur for various reasons, + including not receiving a DWA within an allotted timeframe, no new + requests should be forwarded to the peer, but failover procedures are + invoked. When an active peer is moved to this mode, additional + connections SHOULD be established to ensure that the necessary number + of active connections exists. + + There are two ways that a peer is removed from the suspect peer list: + + 1. The peer is no longer reachable, causing the transport connection + to be shutdown. The peer is moved to the closed state. + + 2. Three watchdog messages are exchanged with accepted round trip + times, and the connection to the peer is considered stabilized. + + In the event the peer being removed is either the primary or + secondary, an alternate peer SHOULD replace the deleted peer, and + assume the role of either primary or secondary. + +5.2. Diameter Peer Discovery + + Allowing for dynamic Diameter agent discovery will make it possible + for simpler and more robust deployment of Diameter services. In + order to promote interoperable implementations of Diameter peer + discovery, the following mechanisms are described. These are based + + + + + +Calhoun, et al. Standards Track [Page 56] + +RFC 3588 Diameter Based Protocol September 2003 + + + on existing IETF standards. The first option (manual configuration) + MUST be supported by all DIAMETER nodes, while the latter two options + (SRVLOC and DNS) MAY be supported. + + There are two cases where Diameter peer discovery may be performed. + The first is when a Diameter client needs to discover a first-hop + Diameter agent. The second case is when a Diameter agent needs to + discover another agent - for further handling of a Diameter + operation. In both cases, the following 'search order' is + recommended: + + 1. The Diameter implementation consults its list of static (manually) + configured Diameter agent locations. These will be used if they + exist and respond. + + 2. The Diameter implementation uses SLPv2 [SLP] to discover Diameter + services. The Diameter service template [TEMPLATE] is included in + Appendix A. + + It is recommended that SLPv2 security be deployed (this requires + distributing keys to SLPv2 agents). This is discussed further in + Appendix A. SLPv2 security SHOULD be used (requiring distribution + of keys to SLPv2 agents) in order to ensure that discovered peers + are authorized for their roles. SLPv2 is discussed further in + Appendix A. + + 3. The Diameter implementation performs a NAPTR query for a server in + a particular realm. The Diameter implementation has to know in + advance which realm to look for a Diameter agent in. This could + be deduced, for example, from the 'realm' in a NAI that a Diameter + implementation needed to perform a Diameter operation on. + + 3.1 The services relevant for the task of transport protocol + selection are those with NAPTR service fields with values + "AAA+D2x", where x is a letter that corresponds to a transport + protocol supported by the domain. This specification defines + D2T for TCP and D2S for SCTP. We also establish an IANA + registry for NAPTR service name to transport protocol + mappings. + + These NAPTR records provide a mapping from a domain, to the + SRV record for contacting a server with the specific transport + protocol in the NAPTR services field. The resource record + will contain an empty regular expression and a replacement + value, which is the SRV record for that particular transport + protocol. If the server supports multiple transport + protocols, there will be multiple NAPTR records, each with a + different service value. As per RFC 2915 [NAPTR], the client + + + +Calhoun, et al. Standards Track [Page 57] + +RFC 3588 Diameter Based Protocol September 2003 + + + discards any records whose services fields are not applicable. + For the purposes of this specification, several rules are + defined. + + 3.2 A client MUST discard any service fields that identify a + resolution service whose value is not "D2X", for values of X + that indicate transport protocols supported by the client. + The NAPTR processing as described in RFC 2915 will result in + discovery of the most preferred transport protocol of the + server that is supported by the client, as well as an SRV + record for the server. + + The domain suffixes in the NAPTR replacement field SHOULD + match the domain of the original query. + + 4. If no NAPTR records are found, the requester queries for those + address records for the destination address, + '_diameter._sctp'.realm or '_diameter._tcp'.realm. Address + records include A RR's, AAAA RR's or other similar records, chosen + according to the requestor's network protocol capabilities. If + the DNS server returns no address records, the requestor gives up. + + If the server is using a site certificate, the domain name in the + query and the domain name in the replacement field MUST both be + valid based on the site certificate handed out by the server in + the TLS or IKE exchange. Similarly, the domain name in the SRV + query and the domain name in the target in the SRV record MUST + both be valid based on the same site certificate. Otherwise, an + attacker could modify the DNS records to contain replacement + values in a different domain, and the client could not validate + that this was the desired behavior, or the result of an attack + + Also, the Diameter Peer MUST check to make sure that the + discovered peers are authorized to act in its role. + Authentication via IKE or TLS, or validation of DNS RRs via DNSSEC + is not sufficient to conclude this. For example, a web server may + have obtained a valid TLS certificate, and secured RRs may be + included in the DNS, but this does not imply that it is authorized + to act as a Diameter Server. + + Authorization can be achieved for example, by configuration of a + Diameter Server CA. Alternatively this can be achieved by + definition of OIDs within TLS or IKE certificates so as to signify + Diameter Server authorization. + + A dynamically discovered peer causes an entry in the Peer Table (see + Section 2.6) to be created. Note that entries created via DNS MUST + expire (or be refreshed) within the DNS TTL. If a peer is discovered + + + +Calhoun, et al. Standards Track [Page 58] + +RFC 3588 Diameter Based Protocol September 2003 + + + outside of the local realm, a routing table entry (see Section 2.7) + for the peer's realm is created. The routing table entry's + expiration MUST match the peer's expiration value. + +5.3. Capabilities Exchange + + When two Diameter peers establish a transport connection, they MUST + exchange the Capabilities Exchange messages, as specified in the peer + state machine (see Section 5.6). This message allows the discovery + of a peer's identity and its capabilities (protocol version number, + supported Diameter applications, security mechanisms, etc.) + + The receiver only issues commands to its peers that have advertised + support for the Diameter application that defines the command. A + Diameter node MUST cache the supported applications in order to + ensure that unrecognized commands and/or AVPs are not unnecessarily + sent to a peer. + + A receiver of a Capabilities-Exchange-Req (CER) message that does not + have any applications in common with the sender MUST return a + Capabilities-Exchange-Answer (CEA) with the Result-Code AVP set to + DIAMETER_NO_COMMON_APPLICATION, and SHOULD disconnect the transport + layer connection. Note that receiving a CER or CEA from a peer + advertising itself as a Relay (see Section 2.4) MUST be interpreted + as having common applications with the peer. + + Similarly, a receiver of a Capabilities-Exchange-Req (CER) message + that does not have any security mechanisms in common with the sender + MUST return a Capabilities-Exchange-Answer (CEA) with the Result-Code + AVP set to DIAMETER_NO_COMMON_SECURITY, and SHOULD disconnect the + transport layer connection. + + CERs received from unknown peers MAY be silently discarded, or a CEA + MAY be issued with the Result-Code AVP set to DIAMETER_UNKNOWN_PEER. + In both cases, the transport connection is closed. If the local + policy permits receiving CERs from unknown hosts, a successful CEA + MAY be returned. If a CER from an unknown peer is answered with a + successful CEA, the lifetime of the peer entry is equal to the + lifetime of the transport connection. In case of a transport + failure, all the pending transactions destined to the unknown peer + can be discarded. + + The CER and CEA messages MUST NOT be proxied, redirected or relayed. + + Since the CER/CEA messages cannot be proxied, it is still possible + that an upstream agent receives a message for which it has no + available peers to handle the application that corresponds to the + Command-Code. In such instances, the 'E' bit is set in the answer + + + +Calhoun, et al. Standards Track [Page 59] + +RFC 3588 Diameter Based Protocol September 2003 + + + message (see Section 7.) with the Result-Code AVP set to + DIAMETER_UNABLE_TO_DELIVER to inform the downstream to take action + (e.g., re-routing request to an alternate peer). + + With the exception of the Capabilities-Exchange-Request message, a + message of type Request that includes the Auth-Application-Id or + Acct-Application-Id AVPs, or a message with an application-specific + command code, MAY only be forwarded to a host that has explicitly + advertised support for the application (or has advertised the Relay + Application Identifier). + +5.3.1. Capabilities-Exchange-Request + + The Capabilities-Exchange-Request (CER), indicated by the Command- + Code set to 257 and the Command Flags' 'R' bit set, is sent to + exchange local capabilities. Upon detection of a transport failure, + this message MUST NOT be sent to an alternate peer. + + When Diameter is run over SCTP [SCTP], which allows for connections + to span multiple interfaces and multiple IP addresses, the + Capabilities-Exchange-Request message MUST contain one Host-IP- + Address AVP for each potential IP address that MAY be locally used + when transmitting Diameter messages. + + Message Format + + <CER> ::= < Diameter Header: 257, REQ > + { Origin-Host } + { Origin-Realm } + 1* { Host-IP-Address } + { Vendor-Id } + { Product-Name } + [ Origin-State-Id ] + * [ Supported-Vendor-Id ] + * [ Auth-Application-Id ] + * [ Inband-Security-Id ] + * [ Acct-Application-Id ] + * [ Vendor-Specific-Application-Id ] + [ Firmware-Revision ] + * [ AVP ] + +5.3.2. Capabilities-Exchange-Answer + + The Capabilities-Exchange-Answer (CEA), indicated by the Command-Code + set to 257 and the Command Flags' 'R' bit cleared, is sent in + response to a CER message. + + + + + +Calhoun, et al. Standards Track [Page 60] + +RFC 3588 Diameter Based Protocol September 2003 + + + When Diameter is run over SCTP [SCTP], which allows connections to + span multiple interfaces, hence, multiple IP addresses, the + Capabilities-Exchange-Answer message MUST contain one Host-IP-Address + AVP for each potential IP address that MAY be locally used when + transmitting Diameter messages. + + Message Format + + <CEA> ::= < Diameter Header: 257 > + { Result-Code } + { Origin-Host } + { Origin-Realm } + 1* { Host-IP-Address } + { Vendor-Id } + { Product-Name } + [ Origin-State-Id ] + [ Error-Message ] + * [ Failed-AVP ] + * [ Supported-Vendor-Id ] + * [ Auth-Application-Id ] + * [ Inband-Security-Id ] + * [ Acct-Application-Id ] + * [ Vendor-Specific-Application-Id ] + [ Firmware-Revision ] + * [ AVP ] + +5.3.3. Vendor-Id AVP + + The Vendor-Id AVP (AVP Code 266) is of type Unsigned32 and contains + the IANA "SMI Network Management Private Enterprise Codes" [ASSIGNNO] + value assigned to the vendor of the Diameter application. In + combination with the Supported-Vendor-Id AVP (Section 5.3.6), 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 of the + Vendor-Id, Product-Name (Section 5.3.7) and the Firmware-Revision + (Section 5.3.4) AVPs MAY provide very useful debugging information. + + A Vendor-Id value of zero in the CER or CEA messages is reserved and + indicates that this field is ignored. + +5.3.4. Firmware-Revision AVP + + The Firmware-Revision AVP (AVP Code 267) is of type Unsigned32 and is + used to inform a Diameter peer of the firmware revision of the + issuing device. + + + + + + +Calhoun, et al. Standards Track [Page 61] + +RFC 3588 Diameter Based Protocol September 2003 + + + 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. + +5.3.5. Host-IP-Address AVP + + The Host-IP-Address AVP (AVP Code 257) is of type Address and is used + to inform a Diameter peer of the sender's IP address. All source + addresses that a Diameter node expects to use with SCTP [SCTP] MUST + be advertised in the CER and CEA messages by including a Host-IP- + Address AVP for each address. This AVP MUST ONLY be used in the CER + and CEA messages. + +5.3.6. Supported-Vendor-Id AVP + + The Supported-Vendor-Id AVP (AVP Code 265) is of type Unsigned32 and + contains the IANA "SMI Network Management Private Enterprise Codes" + [ASSIGNNO] value assigned to a vendor other than the device vendor. + This is used in the CER and CEA messages in order to inform the peer + that the sender supports (a subset of) the vendor-specific AVPs + defined by the vendor identified in this AVP. + +5.3.7. Product-Name AVP + + The Product-Name AVP (AVP Code 269) is of type UTF8String, and + contains the vendor assigned name for the product. The Product-Name + AVP SHOULD remain constant across firmware revisions for the same + product. + +5.4. Disconnecting Peer connections + + When a Diameter node disconnects one of its transport connections, + its peer cannot know the reason for the disconnect, and will most + likely assume that a connectivity problem occurred, or that the peer + has rebooted. In these cases, the peer may periodically attempt to + reconnect, as stated in Section 2.1. In the event that the + disconnect was a result of either a shortage of internal resources, + or simply that the node in question has no intentions of forwarding + any Diameter messages to the peer in the foreseeable future, a + periodic connection request would not be welcomed. The + Disconnection-Reason AVP contains the reason the Diameter node issued + the Disconnect-Peer-Request message. + + The Disconnect-Peer-Request message is used by a Diameter node to + inform its peer of its intent to disconnect the transport layer, and + that the peer shouldn't reconnect unless it has a valid reason to do + so (e.g., message to be forwarded). Upon receipt of the message, the + + + + +Calhoun, et al. Standards Track [Page 62] + +RFC 3588 Diameter Based Protocol September 2003 + + + Disconnect-Peer-Answer is returned, which SHOULD contain an error if + messages have recently been forwarded, and are likely in flight, + which would otherwise cause a race condition. + + The receiver of the Disconnect-Peer-Answer initiates the transport + disconnect. + +5.4.1. Disconnect-Peer-Request + + The Disconnect-Peer-Request (DPR), indicated by the Command-Code set + to 282 and the Command Flags' 'R' bit set, is sent to a peer to + inform its intentions to shutdown the transport connection. Upon + detection of a transport failure, this message MUST NOT be sent to an + alternate peer. + + Message Format + + <DPR> ::= < Diameter Header: 282, REQ > + { Origin-Host } + { Origin-Realm } + { Disconnect-Cause } + +5.4.2. Disconnect-Peer-Answer + + The Disconnect-Peer-Answer (DPA), indicated by the Command-Code set + to 282 and the Command Flags' 'R' bit cleared, is sent as a response + to the Disconnect-Peer-Request message. Upon receipt of this + message, the transport connection is shutdown. + + Message Format + + <DPA> ::= < Diameter Header: 282 > + { Result-Code } + { Origin-Host } + { Origin-Realm } + [ Error-Message ] + * [ Failed-AVP ] + +5.4.3. Disconnect-Cause AVP + + The Disconnect-Cause AVP (AVP Code 273) is of type Enumerated. A + Diameter node MUST include this AVP in the Disconnect-Peer-Request + message to inform the peer of the reason for its intention to + shutdown the transport connection. The following values are + supported: + + + + + + +Calhoun, et al. Standards Track [Page 63] + +RFC 3588 Diameter Based Protocol September 2003 + + + REBOOTING 0 + A scheduled reboot is imminent. + + BUSY 1 + The peer's internal resources are constrained, and it has + determined that the transport connection needs to be closed. + + DO_NOT_WANT_TO_TALK_TO_YOU 2 + The peer has determined that it does not see a need for the + transport connection to exist, since it does not expect any + messages to be exchanged in the near future. + +5.5. Transport Failure Detection + + Given the nature of the Diameter protocol, it is recommended that + transport failures be detected as soon as possible. Detecting such + failures will minimize the occurrence of messages sent to unavailable + agents, resulting in unnecessary delays, and will provide better + failover performance. The Device-Watchdog-Request and Device- + Watchdog-Answer messages, defined in this section, are used to pro- + actively detect transport failures. + +5.5.1. Device-Watchdog-Request + + The Device-Watchdog-Request (DWR), indicated by the Command-Code set + to 280 and the Command Flags' 'R' bit set, is sent to a peer when no + traffic has been exchanged between two peers (see Section 5.5.3). + Upon detection of a transport failure, this message MUST NOT be sent + to an alternate peer. + + Message Format + + <DWR> ::= < Diameter Header: 280, REQ > + { Origin-Host } + { Origin-Realm } + [ Origin-State-Id ] + +5.5.2. Device-Watchdog-Answer + + The Device-Watchdog-Answer (DWA), indicated by the Command-Code set + to 280 and the Command Flags' 'R' bit cleared, is sent as a response + to the Device-Watchdog-Request message. + + + + + + + + + +Calhoun, et al. Standards Track [Page 64] + +RFC 3588 Diameter Based Protocol September 2003 + + + Message Format + + <DWA> ::= < Diameter Header: 280 > + { Result-Code } + { Origin-Host } + { Origin-Realm } + [ Error-Message ] + * [ Failed-AVP ] + [ Original-State-Id ] + +5.5.3. Transport Failure Algorithm + + The transport failure algorithm is defined in [AAATRANS]. All + Diameter implementations MUST support the algorithm defined in the + specification in order to be compliant to the Diameter base protocol. + +5.5.4. Failover and Failback Procedures + + In the event that a transport failure is detected with a peer, it is + necessary for all pending request messages to be forwarded to an + alternate agent, if possible. This is commonly referred to as + failover. + + In order for a Diameter node to perform failover procedures, it is + necessary for the node to maintain a pending message queue for a + given peer. When an answer message is received, the corresponding + request is removed from the queue. The Hop-by-Hop Identifier field + is used to match the answer with the queued request. + + When a transport failure is detected, if possible all messages in the + queue are sent to an alternate agent with the T flag set. On booting + a Diameter client or agent, the T flag is also set on any records + still remaining to be transmitted in non-volatile storage. An + example of a case where it is not possible to forward the message to + an alternate server is when the message has a fixed destination, and + the unavailable peer is the message's final destination (see + Destination-Host AVP). Such an error requires that the agent return + an answer message with the 'E' bit set and the Result-Code AVP set to + DIAMETER_UNABLE_TO_DELIVER. + + It is important to note that multiple identical requests or answers + MAY be received as a result of a failover. The End-to-End Identifier + field in the Diameter header along with the Origin-Host AVP MUST be + used to identify duplicate messages. + + + + + + + +Calhoun, et al. Standards Track [Page 65] + +RFC 3588 Diameter Based Protocol September 2003 + + + As described in Section 2.1, a connection request should be + periodically attempted with the failed peer in order to re-establish + the transport connection. Once a connection has been successfully + established, messages can once again be forwarded to the peer. This + is commonly referred to as failback. + +5.6. Peer State Machine + + This section contains a finite state machine that MUST be observed by + all Diameter implementations. Each Diameter node MUST follow the + state machine described below when communicating with each peer. + Multiple actions are separated by commas, and may continue on + succeeding lines, as space requires. Similarly, state and next state + may also span multiple lines, as space requires. + + This state machine is closely coupled with the state machine + described in [AAATRANS], which is used to open, close, failover, + probe, and reopen transport connections. Note in particular that + [AAATRANS] requires the use of watchdog messages to probe + connections. For Diameter, DWR and DWA messages are to be used. + + I- is used to represent the initiator (connecting) connection, while + the R- is used to represent the responder (listening) connection. + The lack of a prefix indicates that the event or action is the same + regardless of the connection on which the event occurred. + + The stable states that a state machine may be in are Closed, I-Open + and R-Open; all other states are intermediate. Note that I-Open and + R-Open are equivalent except for whether the initiator or responder + transport connection is used for communication. + + A CER message is always sent on the initiating connection immediately + after the connection request is successfully completed. In the case + of an election, one of the two connections will shut down. The + responder connection will survive if the Origin-Host of the local + Diameter entity is higher than that of the peer; the initiator + connection will survive if the peer's Origin-Host is higher. All + subsequent messages are sent on the surviving connection. Note that + the results of an election on one peer are guaranteed to be the + inverse of the results on the other. + + For TLS usage, a TLS handshake will begin when both ends are in the + open state. If the TLS handshake is successful, all further messages + will be sent via TLS. If the handshake fails, both ends move to the + closed state. + + The state machine constrains only the behavior of a Diameter + implementation as seen by Diameter peers through events on the wire. + + + +Calhoun, et al. Standards Track [Page 66] + +RFC 3588 Diameter Based Protocol September 2003 + + + Any implementation that produces equivalent results is considered + compliant. + + state event action next state + ----------------------------------------------------------------- + Closed Start I-Snd-Conn-Req Wait-Conn-Ack + R-Conn-CER R-Accept, R-Open + Process-CER, + R-Snd-CEA + + Wait-Conn-Ack I-Rcv-Conn-Ack I-Snd-CER Wait-I-CEA + I-Rcv-Conn-Nack Cleanup Closed + R-Conn-CER R-Accept, Wait-Conn-Ack/ + Process-CER Elect + Timeout Error Closed + + Wait-I-CEA I-Rcv-CEA Process-CEA I-Open + R-Conn-CER R-Accept, Wait-Returns + Process-CER, + Elect + I-Peer-Disc I-Disc Closed + I-Rcv-Non-CEA Error Closed + Timeout Error Closed + + Wait-Conn-Ack/ I-Rcv-Conn-Ack I-Snd-CER,Elect Wait-Returns + Elect I-Rcv-Conn-Nack R-Snd-CEA R-Open + R-Peer-Disc R-Disc Wait-Conn-Ack + R-Conn-CER R-Reject Wait-Conn-Ack/ + Elect + Timeout Error Closed + + Wait-Returns Win-Election I-Disc,R-Snd-CEA R-Open + I-Peer-Disc I-Disc, R-Open + R-Snd-CEA + I-Rcv-CEA R-Disc I-Open + R-Peer-Disc R-Disc Wait-I-CEA + R-Conn-CER R-Reject Wait-Returns + Timeout Error Closed + + R-Open Send-Message R-Snd-Message R-Open + R-Rcv-Message Process R-Open + R-Rcv-DWR Process-DWR, R-Open + R-Snd-DWA + R-Rcv-DWA Process-DWA R-Open + R-Conn-CER R-Reject R-Open + Stop R-Snd-DPR Closing + R-Rcv-DPR R-Snd-DPA, Closed + R-Disc + + + +Calhoun, et al. Standards Track [Page 67] + +RFC 3588 Diameter Based Protocol September 2003 + + + R-Peer-Disc R-Disc Closed + R-Rcv-CER R-Snd-CEA R-Open + R-Rcv-CEA Process-CEA R-Open + + I-Open Send-Message I-Snd-Message I-Open + I-Rcv-Message Process I-Open + I-Rcv-DWR Process-DWR, I-Open + I-Snd-DWA + I-Rcv-DWA Process-DWA I-Open + R-Conn-CER R-Reject I-Open + Stop I-Snd-DPR Closing + I-Rcv-DPR I-Snd-DPA, Closed + I-Disc + I-Peer-Disc I-Disc Closed + I-Rcv-CER I-Snd-CEA I-Open + I-Rcv-CEA Process-CEA I-Open + + Closing I-Rcv-DPA I-Disc Closed + R-Rcv-DPA R-Disc Closed + Timeout Error Closed + I-Peer-Disc I-Disc Closed + R-Peer-Disc R-Disc Closed + +5.6.1. Incoming connections + + When a connection request is received from a Diameter peer, it is + not, in the general case, possible to know the identity of that peer + until a CER is received from it. This is because host and port + determine the identity of a Diameter peer; and the source port of an + incoming connection is arbitrary. Upon receipt of CER, the identity + of the connecting peer can be uniquely determined from Origin-Host. + + For this reason, a Diameter peer must employ logic separate from the + state machine to receive connection requests, accept them, and await + CER. Once CER arrives on a new connection, the Origin-Host that + identifies the peer is used to locate the state machine associated + with that peer, and the new connection and CER are passed to the + state machine as an R-Conn-CER event. + + The logic that handles incoming connections SHOULD close and discard + the connection if any message other than CER arrives, or if an + implementation-defined timeout occurs prior to receipt of CER. + + Because handling of incoming connections up to and including receipt + of CER requires logic, separate from that of any individual state + machine associated with a particular peer, it is described separately + in this section rather than in the state machine above. + + + + +Calhoun, et al. Standards Track [Page 68] + +RFC 3588 Diameter Based Protocol September 2003 + + +5.6.2. Events + + Transitions and actions in the automaton are caused by events. In + this section, we will ignore the -I and -R prefix, since the actual + event would be identical, but would occur on one of two possible + connections. + + Start The Diameter application has signaled that a + connection should be initiated with the peer. + + R-Conn-CER An acknowledgement is received stating that the + transport connection has been established, and the + associated CER has arrived. + + Rcv-Conn-Ack A positive acknowledgement is received confirming that + the transport connection is established. + + Rcv-Conn-Nack A negative acknowledgement was received stating that + the transport connection was not established. + + Timeout An application-defined timer has expired while waiting + for some event. + + Rcv-CER A CER message from the peer was received. + + Rcv-CEA A CEA message from the peer was received. + + Rcv-Non-CEA A message other than CEA from the peer was received. + + Peer-Disc A disconnection indication from the peer was received. + + Rcv-DPR A DPR message from the peer was received. + + Rcv-DPA A DPA message from the peer was received. + + Win-Election An election was held, and the local node was the + winner. + + Send-Message A message is to be sent. + + Rcv-Message A message other than CER, CEA, DPR, DPA, DWR or DWA + was received. + + Stop The Diameter application has signaled that a + connection should be terminated (e.g., on system + shutdown). + + + + + +Calhoun, et al. Standards Track [Page 69] + +RFC 3588 Diameter Based Protocol September 2003 + + +5.6.3. Actions + + Actions in the automaton are caused by events and typically indicate + the transmission of packets and/or an action to be taken on the + connection. In this section we will ignore the I- and R-prefix, + since the actual action would be identical, but would occur on one of + two possible connections. + + Snd-Conn-Req A transport connection is initiated with the peer. + + Accept The incoming connection associated with the R-Conn-CER + is accepted as the responder connection. + + Reject The incoming connection associated with the R-Conn-CER + is disconnected. + + Process-CER The CER associated with the R-Conn-CER is processed. + + Snd-CER A CER message is sent to the peer. + + Snd-CEA A CEA message is sent to the peer. + + Cleanup If necessary, the connection is shutdown, and any + local resources are freed. + + Error The transport layer connection is disconnected, either + politely or abortively, in response to an error + condition. Local resources are freed. + + Process-CEA A received CEA is processed. + + Snd-DPR A DPR message is sent to the peer. + + Snd-DPA A DPA message is sent to the peer. + + Disc The transport layer connection is disconnected, and + local resources are freed. + + Elect An election occurs (see Section 5.6.4 for more + information). + + Snd-Message A message is sent. + + Snd-DWR A DWR message is sent. + + Snd-DWA A DWA message is sent. + + Process-DWR The DWR message is serviced. + + + +Calhoun, et al. Standards Track [Page 70] + +RFC 3588 Diameter Based Protocol September 2003 + + + Process-DWA The DWA message is serviced. + + Process A message is serviced. + +5.6.4. The Election Process + + The election is performed on the responder. The responder compares + the Origin-Host received in the CER sent by its peer with its own + Origin-Host. If the local Diameter entity's Origin-Host is higher + than the peer's, a Win-Election event is issued locally. + + The comparison proceeds by considering the shorter OctetString to be + padded with zeros so that it length is the same as the length of the + longer, then performing an octet-by-octet unsigned comparison with + the first octet being most significant. Any remaining octets are + assumed to have value 0x80. + +6. Diameter message processing + + This section describes how Diameter requests and answers are created + and processed. + +6.1. Diameter Request Routing Overview + + A request is sent towards its final destination using a combination + of the Destination-Realm and Destination-Host AVPs, in one of these + three combinations: + + - a request that is not able to be proxied (such as CER) MUST NOT + contain either Destination-Realm or Destination-Host AVPs. + + - a request that needs to be sent to a home server serving a + specific realm, but not to a specific server (such as the first + request of a series of round-trips), MUST contain a Destination- + Realm AVP, but MUST NOT contain a Destination-Host AVP. + + - otherwise, a request that needs to be sent to a specific home + server among those serving a given realm, MUST contain both the + Destination-Realm and Destination-Host AVPs. + + The Destination-Host AVP is used as described above when the + destination of the request is fixed, which includes: + + - Authentication requests that span multiple round trips + + - A Diameter message that uses a security mechanism that makes use + of a pre-established session key shared between the source and the + final destination of the message. + + + +Calhoun, et al. Standards Track [Page 71] + +RFC 3588 Diameter Based Protocol September 2003 + + + - Server initiated messages that MUST be received by a specific + Diameter client (e.g., access device), such as the Abort-Session- + Request message, which is used to request that a particular user's + session be terminated. + + Note that an agent can forward a request to a host described in the + Destination-Host AVP only if the host in question is included in its + peer table (see Section 2.7). Otherwise, the request is routed based + on the Destination-Realm only (see Sections 6.1.6). + + The Destination-Realm AVP MUST be present if the message is + proxiable. Request messages that may be forwarded by Diameter agents + (proxies, redirects or relays) MUST also contain an Acct- + Application-Id AVP, an Auth-Application-Id AVP or a Vendor-Specific- + Application-Id AVP. A message that MUST NOT be forwarded by Diameter + agents (proxies, redirects or relays) MUST not include the + Destination-Realm in its ABNF. The value of the Destination-Realm + AVP MAY be extracted from the User-Name AVP, or other application- + specific methods. + + When a message is received, the message is processed in the following + order: + + 1. If the message is destined for the local host, the procedures + listed in Section 6.1.4 are followed. + + 2. If the message is intended for a Diameter peer with whom the local + host is able to directly communicate, the procedures listed in + Section 6.1.5 are followed. This is known as Request Forwarding. + + 3. The procedures listed in Section 6.1.6 are followed, which is + known as Request Routing. + + 4. If none of the above is successful, an answer is returned with the + Result-Code set to DIAMETER_UNABLE_TO_DELIVER, with the E-bit set. + + For routing of Diameter messages to work within an administrative + domain, all Diameter nodes within the realm MUST be peers. + + Note the processing rules contained in this section are intended to + be used as general guidelines to Diameter developers. Certain + implementations MAY use different methods than the ones described + here, and still comply with the protocol specification. See Section + 7 for more detail on error handling. + + + + + + + +Calhoun, et al. Standards Track [Page 72] + +RFC 3588 Diameter Based Protocol September 2003 + + +6.1.1. Originating a Request + + When creating a request, in addition to any other procedures + described in the application definition for that specific request, + the following procedures MUST be followed: + + - the Command-Code is set to the appropriate value + + - the 'R' bit is set + + - the End-to-End Identifier is set to a locally unique value + + - the Origin-Host and Origin-Realm AVPs MUST be set to the + appropriate values, used to identify the source of the message + + - the Destination-Host and Destination-Realm AVPs MUST be set to the + appropriate values as described in Section 6.1. + + - an Acct-Application-Id AVP, an Auth-Application-Id or a Vendor- + Specific-Application-Id AVP must be included if the request is + proxiable. + +6.1.2. Sending a Request + + When sending a request, originated either locally, or as the result + of a forwarding or routing operation, the following procedures MUST + be followed: + + - the Hop-by-Hop Identifier should be set to a locally unique value + + - The message should be saved in the list of pending requests. + + Other actions to perform on the message based on the particular role + the agent is playing are described in the following sections. + +6.1.3. Receiving Requests + + A relay or proxy agent MUST check for forwarding loops when receiving + requests. A loop is detected if the server finds its own identity in + a Route-Record AVP. When such an event occurs, the agent MUST answer + with the Result-Code AVP set to DIAMETER_LOOP_DETECTED. + +6.1.4. Processing Local Requests + + A request is known to be for local consumption when one of the + following conditions occur: + + - The Destination-Host AVP contains the local host's identity, + + + +Calhoun, et al. Standards Track [Page 73] + +RFC 3588 Diameter Based Protocol September 2003 + + + - The Destination-Host AVP is not present, the Destination-Realm AVP + contains a realm the server is configured to process locally, and + the Diameter application is locally supported, or + + - Both the Destination-Host and the Destination-Realm are not + present. + + When a request is locally processed, the rules in Section 6.2 should + be used to generate the corresponding answer. + +6.1.5. Request Forwarding + + Request forwarding is done using the Diameter Peer Table. The + Diameter peer table contains all of the peers that the local node is + able to directly communicate with. + + When a request is received, and the host encoded in the Destination- + Host AVP is one that is present in the peer table, the message SHOULD + be forwarded to the peer. + +6.1.6. Request Routing + + Diameter request message routing is done via realms and applications. + A Diameter message that may be forwarded by Diameter agents (proxies, + redirects or relays) MUST include the target realm in the + Destination-Realm AVP and one of the application identification AVPs + Auth-Application-Id, Acct-Application-Id or Vendor-Specific- + Application-Id. The realm MAY be retrieved from the User-Name AVP, + which is in the form of a Network Access Identifier (NAI). The realm + portion of the NAI is inserted in the Destination-Realm AVP. + + Diameter agents MAY have a list of locally supported realms and + applications, and MAY have a list of externally supported realms and + applications. When a request is received that includes a realm + and/or application that is not locally supported, the message is + routed to the peer configured in the Realm Routing Table (see Section + 2.7). + +6.1.7. Redirecting requests + + When a redirect agent receives a request whose routing entry is set + to REDIRECT, it MUST reply with an answer message with the 'E' bit + set, while maintaining the Hop-by-Hop Identifier in the header, and + include the Result-Code AVP to DIAMETER_REDIRECT_INDICATION. Each of + the servers associated with the routing entry are added in separate + Redirect-Host AVP. + + + + + +Calhoun, et al. Standards Track [Page 74] + +RFC 3588 Diameter Based Protocol September 2003 + + + +------------------+ + | Diameter | + | Redirect Agent | + +------------------+ + ^ | 2. command + 'E' bit + 1. Request | | Result-Code = + joe@example.com | | DIAMETER_REDIRECT_INDICATION + + | | Redirect-Host AVP(s) + | v + +-------------+ 3. Request +-------------+ + | example.com |------------->| example.net | + | Relay | | Diameter | + | Agent |<-------------| Server | + +-------------+ 4. Answer +-------------+ + + Figure 5: Diameter Redirect Agent + + The receiver of the answer message with the 'E' bit set, and the + Result-Code AVP set to DIAMETER_REDIRECT_INDICATION uses the hop-by- + hop field in the Diameter header to identify the request in the + pending message queue (see Section 5.3) that is to be redirected. If + no transport connection exists with the new agent, one is created, + and the request is sent directly to it. + + Multiple Redirect-Host AVPs are allowed. The receiver of the answer + message with the 'E' bit set selects exactly one of these hosts as + the destination of the redirected message. + +6.1.8. Relaying and Proxying Requests + + A relay or proxy agent MUST append a Route-Record AVP to all requests + forwarded. The AVP contains the identity of the peer the request was + received from. + + The Hop-by-Hop identifier in the request is saved, and replaced with + a locally unique value. The source of the request is also saved, + which includes the IP address, port and protocol. + + A relay or proxy agent MAY include the Proxy-Info AVP in requests if + it requires access to any local state information when the + corresponding response is received. Proxy-Info AVP has certain + security implications and SHOULD contain an embedded HMAC with a + node-local key. Alternatively, it MAY simply use local storage to + store state information. + + The message is then forwarded to the next hop, as identified in the + Realm Routing Table. + + + + +Calhoun, et al. Standards Track [Page 75] + +RFC 3588 Diameter Based Protocol September 2003 + + + Figure 6 provides an example of message routing using the procedures + listed in these sections. + + (Origin-Host=nas.mno.net) (Origin-Host=nas.mno.net) + (Origin-Realm=mno.net) (Origin-Realm=mno.net) + (Destination-Realm=example.com) (Destination- + Realm=example.com) + (Route-Record=nas.example.net) + +------+ ------> +------+ ------> +------+ + | | (Request) | | (Request) | | + | NAS +-------------------+ DRL +-------------------+ HMS | + | | | | | | + +------+ <------ +------+ <------ +------+ + example.net (Answer) example.net (Answer) example.com + (Origin-Host=hms.example.com) (Origin-Host=hms.example.com) + (Origin-Realm=example.com) (Origin-Realm=example.com) + + Figure 6: Routing of Diameter messages + +6.2. Diameter Answer Processing + + When a request is locally processed, the following procedures MUST be + applied to create the associated answer, in addition to any + additional procedures that MAY be discussed in the Diameter + application defining the command: + + - The same Hop-by-Hop identifier in the request is used in the + answer. + + - The local host's identity is encoded in the Origin-Host AVP. + + - The Destination-Host and Destination-Realm AVPs MUST NOT be + present in the answer message. + + - The Result-Code AVP is added with its value indicating success or + failure. + + - If the Session-Id is present in the request, it MUST be included + in the answer. + + - Any Proxy-Info AVPs in the request MUST be added to the answer + message, in the same order they were present in the request. + + - The 'P' bit is set to the same value as the one in the request. + + - The same End-to-End identifier in the request is used in the + answer. + + + + +Calhoun, et al. Standards Track [Page 76] + +RFC 3588 Diameter Based Protocol September 2003 + + + Note that the error messages (see Section 7.3) are also subjected to + the above processing rules. + +6.2.1. Processing received Answers + + A Diameter client or proxy MUST match the Hop-by-Hop Identifier in an + answer received against the list of pending requests. The + corresponding message should be removed from the list of pending + requests. It SHOULD ignore answers received that do not match a + known Hop-by-Hop Identifier. + +6.2.2. Relaying and Proxying Answers + + If the answer is for a request which was proxied or relayed, the + agent MUST restore the original value of the Diameter header's Hop- + by-Hop Identifier field. + + If the last Proxy-Info AVP in the message is targeted to the local + Diameter server, the AVP MUST be removed before the answer is + forwarded. + + If a relay or proxy agent receives an answer with a Result-Code AVP + indicating a failure, it MUST NOT modify the contents of the AVP. + Any additional local errors detected SHOULD be logged, but not + reflected in the Result-Code AVP. If the agent receives an answer + message with a Result-Code AVP indicating success, and it wishes to + modify the AVP to indicate an error, it MUST modify the Result-Code + AVP to contain the appropriate error in the message destined towards + the access device as well as include the Error-Reporting-Host AVP and + it MUST issue an STR on behalf of the access device. + + The agent MUST then send the answer to the host that it received the + original request from. + +6.3. Origin-Host AVP + + The Origin-Host AVP (AVP Code 264) is of type DiameterIdentity, and + MUST be present in all Diameter messages. This AVP identifies the + endpoint that originated the Diameter message. Relay agents MUST NOT + modify this AVP. + + The value of the Origin-Host AVP is guaranteed to be unique within a + single host. + + Note that the Origin-Host AVP may resolve to more than one address as + the Diameter peer may support more than one address. + + + + + +Calhoun, et al. Standards Track [Page 77] + +RFC 3588 Diameter Based Protocol September 2003 + + + This AVP SHOULD be placed as close to the Diameter header as + possible. 6.10 + +6.4. Origin-Realm AVP + + The Origin-Realm AVP (AVP Code 296) is of type DiameterIdentity. + This AVP contains the Realm of the originator of any Diameter message + and MUST be present in all messages. + + This AVP SHOULD be placed as close to the Diameter header as + possible. + +6.5. Destination-Host AVP + + The Destination-Host AVP (AVP Code 293) is of type DiameterIdentity. + This AVP MUST be present in all unsolicited agent initiated messages, + MAY be present in request messages, and MUST NOT be present in Answer + messages. + + The absence of the Destination-Host AVP will cause a message to be + sent to any Diameter server supporting the application within the + realm specified in Destination-Realm AVP. + + This AVP SHOULD be placed as close to the Diameter header as + possible. + +6.6. Destination-Realm AVP + + The Destination-Realm AVP (AVP Code 283) is of type DiameterIdentity, + and contains the realm the message is to be routed to. The + Destination-Realm AVP MUST NOT be present in Answer messages. + Diameter Clients insert the realm portion of the User-Name AVP. + Diameter servers initiating a request message use the value of the + Origin-Realm AVP from a previous message received from the intended + target host (unless it is known a priori). When present, the + Destination-Realm AVP is used to perform message routing decisions. + + Request messages whose ABNF does not list the Destination-Realm AVP + as a mandatory AVP are inherently non-routable messages. + + This AVP SHOULD be placed as close to the Diameter header as + possible. + +6.7. Routing AVPs + + The AVPs defined in this section are Diameter AVPs used for routing + purposes. These AVPs change as Diameter messages are processed by + agents, and therefore MUST NOT be protected by end-to-end security. + + + +Calhoun, et al. Standards Track [Page 78] + +RFC 3588 Diameter Based Protocol September 2003 + + +6.7.1. Route-Record AVP + + The Route-Record AVP (AVP Code 282) is of type DiameterIdentity. The + identity added in this AVP MUST be the same as the one received in + the Origin-Host of the Capabilities Exchange message. + +6.7.2. Proxy-Info AVP + + The Proxy-Info AVP (AVP Code 284) is of type Grouped. The Grouped + Data field has the following ABNF grammar: + + Proxy-Info ::= < AVP Header: 284 > + { Proxy-Host } + { Proxy-State } + * [ AVP ] + +6.7.3. Proxy-Host AVP + + The Proxy-Host AVP (AVP Code 280) is of type DiameterIdentity. This + AVP contains the identity of the host that added the Proxy-Info AVP. + +6.7.4. Proxy-State AVP + + The Proxy-State AVP (AVP Code 33) is of type OctetString, and + contains state local information, and MUST be treated as opaque data. + +6.8. Auth-Application-Id AVP + + The Auth-Application-Id AVP (AVP Code 258) is of type Unsigned32 and + is used in order to advertise support of the Authentication and + Authorization portion of an application (see Section 2.4). The + Auth-Application-Id MUST also be present in all Authentication and/or + Authorization messages that are defined in a separate Diameter + specification and have an Application ID assigned. + +6.9. Acct-Application-Id AVP + + The Acct-Application-Id AVP (AVP Code 259) is of type Unsigned32 and + is used in order to advertise support of the Accounting portion of an + application (see Section 2.4). The Acct-Application-Id MUST also be + present in all Accounting messages. Exactly one of the Auth- + Application-Id and Acct-Application-Id AVPs MAY be present. + +6.10. Inband-Security-Id AVP + + The Inband-Security-Id AVP (AVP Code 299) is of type Unsigned32 and + is used in order to advertise support of the Security portion of the + application. + + + +Calhoun, et al. Standards Track [Page 79] + +RFC 3588 Diameter Based Protocol September 2003 + + + Currently, the following values are supported, but there is ample + room to add new security Ids. + + NO_INBAND_SECURITY 0 + This peer does not support TLS. This is the default value, if the + AVP is omitted. + + TLS 1 + This node supports TLS security, as defined by [TLS]. + +6.11. Vendor-Specific-Application-Id AVP + + The Vendor-Specific-Application-Id AVP (AVP Code 260) is of type + Grouped and is used to advertise support of a vendor-specific + Diameter Application. Exactly one of the Auth-Application-Id and + Acct-Application-Id AVPs MAY be present. + + This AVP MUST also be present as the first AVP in all experimental + commands defined in the vendor-specific application. + + This AVP SHOULD be placed as close to the Diameter header as + possible. + + AVP Format + + <Vendor-Specific-Application-Id> ::= < AVP Header: 260 > + 1* [ Vendor-Id ] + 0*1{ Auth-Application-Id } + 0*1{ Acct-Application-Id } + +6.12. Redirect-Host AVP + + One or more of instances of this AVP MUST be present if the answer + message's 'E' bit is set and the Result-Code AVP is set to + DIAMETER_REDIRECT_INDICATION. + + Upon receiving the above, the receiving Diameter node SHOULD forward + the request directly to one of the hosts identified in these AVPs. + The server contained in the selected Redirect-Host AVP SHOULD be used + for all messages pertaining to this session. + +6.13. Redirect-Host-Usage AVP + + The Redirect-Host-Usage AVP (AVP Code 261) is of type Enumerated. + This AVP MAY be present in answer messages whose 'E' bit is set and + the Result-Code AVP is set to DIAMETER_REDIRECT_INDICATION. + + + + + +Calhoun, et al. Standards Track [Page 80] + +RFC 3588 Diameter Based Protocol September 2003 + + + When present, this AVP dictates how the routing entry resulting from + the Redirect-Host is to be used. The following values are supported: + + DONT_CACHE 0 + The host specified in the Redirect-Host AVP should not be cached. + This is the default value. + + ALL_SESSION 1 + All messages within the same session, as defined by the same value + of the Session-ID AVP MAY be sent to the host specified in the + Redirect-Host AVP. + + ALL_REALM 2 + All messages destined for the realm requested MAY be sent to the + host specified in the Redirect-Host AVP. + + REALM_AND_APPLICATION 3 + All messages for the application requested to the realm specified + MAY be sent to the host specified in the Redirect-Host AVP. + + ALL_APPLICATION 4 + All messages for the application requested MAY be sent to the host + specified in the Redirect-Host AVP. + + ALL_HOST 5 + All messages that would be sent to the host that generated the + Redirect-Host MAY be sent to the host specified in the Redirect- + Host AVP. + + ALL_USER 6 + All messages for the user requested MAY be sent to the host + specified in the Redirect-Host AVP. + +6.14. Redirect-Max-Cache-Time AVP + + The Redirect-Max-Cache-Time AVP (AVP Code 262) is of type Unsigned32. + This AVP MUST be present in answer messages whose 'E' bit is set, the + Result-Code AVP is set to DIAMETER_REDIRECT_INDICATION and the + Redirect-Host-Usage AVP set to a non-zero value. + + This AVP contains the maximum number of seconds the peer and route + table entries, created as a result of the Redirect-Host, will be + cached. Note that once a host created due to a redirect indication + is no longer reachable, any associated peer and routing table entries + MUST be deleted. + + + + + + +Calhoun, et al. Standards Track [Page 81] + +RFC 3588 Diameter Based Protocol September 2003 + + +6.15. E2E-Sequence AVP + + The E2E-Sequence AVP (AVP Code 300) provides anti-replay protection + for end to end messages and is of type grouped. It contains a random + value (an OctetString with a nonce) and counter (an Integer). For + each end-to-end peer with which a node communicates (or remembers + communicating) a different nonce value MUST be used and the counter + is initiated at zero and increases by one each time this AVP is + emitted to that peer. This AVP MUST be included in all messages + which use end-to-end protection (e.g., CMS signing or encryption). + +7. Error Handling + + There are two different types of errors in Diameter; protocol and + application errors. A protocol error is one that occurs at the base + protocol level, and MAY require per hop attention (e.g., message + routing error). Application errors, on the other hand, generally + occur due to a problem with a function specified in a Diameter + application (e.g., user authentication, Missing AVP). + + Result-Code AVP values that are used to report protocol errors MUST + only be present in answer messages whose 'E' bit is set. When a + request message is received that causes a protocol error, an answer + message is returned with the 'E' bit set, and the Result-Code AVP is + set to the appropriate protocol error value. As the answer is sent + back towards the originator of the request, each proxy or relay agent + MAY take action on the message. + + 1. Request +---------+ Link Broken + +-------------------------->|Diameter |----///----+ + | +---------------------| | v + +------+--+ | 2. answer + 'E' set | Relay 2 | +--------+ + |Diameter |<-+ (Unable to Forward) +---------+ |Diameter| + | | | Home | + | Relay 1 |--+ +---------+ | Server | + +---------+ | 3. Request |Diameter | +--------+ + +-------------------->| | ^ + | Relay 3 |-----------+ + +---------+ + + Figure 7: Example of Protocol Error causing answer message + + Figure 7 provides an example of a message forwarded upstream by a + Diameter relay. When the message is received by Relay 2, and it + detects that it cannot forward the request to the home server, an + answer message is returned with the 'E' bit set and the Result-Code + AVP set to DIAMETER_UNABLE_TO_DELIVER. Given that this error falls + + + + +Calhoun, et al. Standards Track [Page 82] + +RFC 3588 Diameter Based Protocol September 2003 + + + within the protocol error category, Relay 1 would take special + action, and given the error, attempt to route the message through its + alternate Relay 3. + + +---------+ 1. Request +---------+ 2. Request +---------+ + | Access |------------>|Diameter |------------>|Diameter | + | | | | | Home | + | Device |<------------| Relay |<------------| Server | + +---------+ 4. Answer +---------+ 3. Answer +---------+ + (Missing AVP) (Missing AVP) + + Figure 8: Example of Application Error Answer message + + Figure 8 provides an example of a Diameter message that caused an + application error. When application errors occur, the Diameter + entity reporting the error clears the 'R' bit in the Command Flags, + and adds the Result-Code AVP with the proper value. Application + errors do not require any proxy or relay agent involvement, and + therefore the message would be forwarded back to the originator of + the request. + + There are certain Result-Code AVP application errors that require + additional AVPs to be present in the answer. In these cases, the + Diameter node that sets the Result-Code AVP to indicate the error + MUST add the AVPs. Examples are: + + - An unrecognized AVP is received with the 'M' bit (Mandatory bit) + set, causes an answer to be sent with the Result-Code AVP set to + DIAMETER_AVP_UNSUPPORTED, and the Failed-AVP AVP containing the + offending AVP. + + - An AVP that is received with an unrecognized value causes an + answer to be returned with the Result-Code AVP set to + DIAMETER_INVALID_AVP_VALUE, with the Failed-AVP AVP containing the + AVP causing the error. + + - A command is received with an AVP that is omitted, yet is + mandatory according to the command's ABNF. The receiver issues an + answer with the Result-Code set to DIAMETER_MISSING_AVP, and + creates an AVP with the AVP Code and other fields set as expected + in the missing AVP. The created AVP is then added to the Failed- + AVP AVP. + + The Result-Code AVP describes the error that the Diameter node + encountered in its processing. In case there are multiple errors, + the Diameter node MUST report only the first error it encountered + + + + + +Calhoun, et al. Standards Track [Page 83] + +RFC 3588 Diameter Based Protocol September 2003 + + + (detected possibly in some implementation dependent order). The + specific errors that can be described by this AVP are described in + the following section. + +7.1. Result-Code AVP + + The Result-Code AVP (AVP Code 268) is of type Unsigned32 and + indicates whether a particular request was completed successfully or + whether an error occurred. All Diameter answer messages defined in + IETF applications MUST include one Result-Code AVP. A non-successful + Result-Code AVP (one containing a non 2xxx value other than + DIAMETER_REDIRECT_INDICATION) MUST include the Error-Reporting-Host + AVP if the host setting the Result-Code AVP is different from the + identity encoded in the Origin-Host AVP. + + The Result-Code data field contains an IANA-managed 32-bit address + space representing errors (see Section 11.4). Diameter provides the + following classes of errors, all identified by the thousands digit in + the decimal notation: + + - 1xxx (Informational) + - 2xxx (Success) + - 3xxx (Protocol Errors) + - 4xxx (Transient Failures) + - 5xxx (Permanent Failure) + + A non-recognized class (one whose first digit is not defined in this + section) MUST be handled as a permanent failure. + +7.1.1. Informational + + Errors that fall within this category are used to inform the + requester that a request could not be satisfied, and additional + action is required on its part before access is granted. + + DIAMETER_MULTI_ROUND_AUTH 1001 + This informational error is returned by a Diameter server to + inform the access device that the authentication mechanism being + used requires multiple round trips, and a subsequent request needs + to be issued in order for access to be granted. + +7.1.2. Success + + Errors that fall within the Success category are used to inform a + peer that a request has been successfully completed. + + DIAMETER_SUCCESS 2001 + The Request was successfully completed. + + + +Calhoun, et al. Standards Track [Page 84] + +RFC 3588 Diameter Based Protocol September 2003 + + + DIAMETER_LIMITED_SUCCESS 2002 + When returned, the request was successfully completed, but + additional processing is required by the application in order to + provide service to the user. + +7.1.3. Protocol Errors + + Errors that fall within the Protocol Error category SHOULD be treated + on a per-hop basis, and Diameter proxies MAY attempt to correct the + error, if it is possible. Note that these and only these errors MUST + only be used in answer messages whose 'E' bit is set. + + DIAMETER_COMMAND_UNSUPPORTED 3001 + The Request contained a Command-Code that the receiver did not + recognize or support. This MUST be used when a Diameter node + receives an experimental command that it does not understand. + + DIAMETER_UNABLE_TO_DELIVER 3002 + This error is given when Diameter can not deliver the message to + the destination, either because no host within the realm + supporting the required application was available to process the + request, or because Destination-Host AVP was given without the + associated Destination-Realm AVP. + + DIAMETER_REALM_NOT_SERVED 3003 + The intended realm of the request is not recognized. + + DIAMETER_TOO_BUSY 3004 + When returned, a Diameter node SHOULD attempt to send the message + to an alternate peer. This error MUST only be used when a + specific server is requested, and it cannot provide the requested + service. + + DIAMETER_LOOP_DETECTED 3005 + An agent detected a loop while trying to get the message to the + intended recipient. The message MAY be sent to an alternate peer, + if one is available, but the peer reporting the error has + identified a configuration problem. + + DIAMETER_REDIRECT_INDICATION 3006 + A redirect agent 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. When set, the Redirect-Host AVP MUST + be present. + + DIAMETER_APPLICATION_UNSUPPORTED 3007 + A request was sent for an application that is not supported. + + + +Calhoun, et al. Standards Track [Page 85] + +RFC 3588 Diameter Based Protocol September 2003 + + + DIAMETER_INVALID_HDR_BITS 3008 + A request was received whose bits in the Diameter header were + either set to an invalid combination, or to a value that is + inconsistent with the command code's definition. + + DIAMETER_INVALID_AVP_BITS 3009 + A request was received that included an AVP whose flag bits are + set to an unrecognized value, or that is inconsistent with the + AVP's definition. + + DIAMETER_UNKNOWN_PEER 3010 + A CER was received from an unknown peer. + +7.1.4. Transient Failures + + Errors that fall within the transient failures category are used + to inform a peer that the request could not be satisfied at the + time it was received, but MAY be able to satisfy the request in + the future. + + DIAMETER_AUTHENTICATION_REJECTED 4001 + The authentication process for the user failed, most likely due to + an invalid password used by the user. Further attempts MUST only + be tried after prompting the user for a new password. + + DIAMETER_OUT_OF_SPACE 4002 + A Diameter node received the accounting request but was unable to + commit it to stable storage due to a temporary lack of space. + + ELECTION_LOST 4003 + The peer has determined that it has lost the election process and + has therefore disconnected the transport connection. + +7.1.5. Permanent Failures + + Errors that fall within the permanent failures category are used + to inform the peer that the request failed, and should not be + attempted again. + + DIAMETER_AVP_UNSUPPORTED 5001 + The peer received a message that contained an AVP that is not + recognized or supported and was marked with the Mandatory bit. A + Diameter message with this error MUST contain one or more Failed- + AVP AVP containing the AVPs that caused the failure. + + DIAMETER_UNKNOWN_SESSION_ID 5002 + The request contained an unknown Session-Id. + + + + +Calhoun, et al. Standards Track [Page 86] + +RFC 3588 Diameter Based Protocol September 2003 + + + DIAMETER_AUTHORIZATION_REJECTED 5003 + A request was received for which the user could not be authorized. + This error could occur if the service requested is not permitted + to the user. + + DIAMETER_INVALID_AVP_VALUE 5004 + The request contained an AVP with an invalid value in its data + portion. A Diameter message indicating this error MUST include + the offending AVPs within a Failed-AVP AVP. + + DIAMETER_MISSING_AVP 5005 + The request did not contain an AVP that is required by the Command + Code definition. If this value is sent in the Result-Code AVP, a + Failed-AVP AVP SHOULD be included in the message. The Failed-AVP + AVP MUST contain an example of the missing AVP complete with the + Vendor-Id if applicable. The value field of the missing AVP + should be of correct minimum length and contain zeroes. + + DIAMETER_RESOURCES_EXCEEDED 5006 + A request was received that cannot be authorized because the user + has already expended allowed resources. An example of this error + condition is a user that is restricted to one dial-up PPP port, + attempts to establish a second PPP connection. + + DIAMETER_CONTRADICTING_AVPS 5007 + The Home Diameter server has detected AVPs in the request that + contradicted each other, and is not willing to provide service to + the user. One or more Failed-AVP AVPs MUST be present, containing + the AVPs that contradicted each other. + + DIAMETER_AVP_NOT_ALLOWED 5008 + A message was received with an AVP that MUST NOT be present. The + Failed-AVP AVP MUST be included and contain a copy of the + offending AVP. + + DIAMETER_AVP_OCCURS_TOO_MANY_TIMES 5009 + A message was received that included an AVP that appeared more + often than permitted in the message definition. The Failed-AVP + AVP MUST be included and contain a copy of the first instance of + the offending AVP that exceeded the maximum number of occurrences + + DIAMETER_NO_COMMON_APPLICATION 5010 + This error is returned when a CER message is received, and there + are no common applications supported between the peers. + + DIAMETER_UNSUPPORTED_VERSION 5011 + This error is returned when a request was received, whose version + number is unsupported. + + + +Calhoun, et al. Standards Track [Page 87] + +RFC 3588 Diameter Based Protocol September 2003 + + + DIAMETER_UNABLE_TO_COMPLY 5012 + This error is returned when a request is rejected for unspecified + reasons. + + DIAMETER_INVALID_BIT_IN_HEADER 5013 + This error is returned when an unrecognized bit in the Diameter + header is set to one (1). + + DIAMETER_INVALID_AVP_LENGTH 5014 + The request contained an AVP with an invalid length. A Diameter + message indicating this error MUST include the offending AVPs + within a Failed-AVP AVP. + + DIAMETER_INVALID_MESSAGE_LENGTH 5015 + This error is returned when a request is received with an invalid + message length. + + DIAMETER_INVALID_AVP_BIT_COMBO 5016 + The request contained an AVP with which is not allowed to have the + given value in the AVP Flags field. A Diameter message indicating + this error MUST include the offending AVPs within a Failed-AVP + AVP. + + DIAMETER_NO_COMMON_SECURITY 5017 + This error is returned when a CER message is received, and there + are no common security mechanisms supported between the peers. A + Capabilities-Exchange-Answer (CEA) MUST be returned with the + Result-Code AVP set to DIAMETER_NO_COMMON_SECURITY. + +7.2. Error Bit + + The 'E' (Error Bit) in the Diameter header is set when the request + caused a protocol-related error (see Section 7.1.3). A message with + the 'E' bit MUST NOT be sent as a response to an answer message. + Note that a message with the 'E' bit set is still subjected to the + processing rules defined in Section 6.2. When set, the answer + message will not conform to the ABNF specification for the command, + and will instead conform to the following ABNF: + + + + + + + + + + + + + +Calhoun, et al. Standards Track [Page 88] + +RFC 3588 Diameter Based Protocol September 2003 + + + Message Format + + <answer-message> ::= < Diameter Header: code, ERR [PXY] > + 0*1< Session-Id > + { Origin-Host } + { Origin-Realm } + { Result-Code } + [ Origin-State-Id ] + [ Error-Reporting-Host ] + [ Proxy-Info ] + * [ AVP ] + + Note that the code used in the header is the same than the one found + in the request message, but with the 'R' bit cleared and the 'E' bit + set. The 'P' bit in the header is set to the same value as the one + found in the request message. + +7.3. Error-Message AVP + + The Error-Message AVP (AVP Code 281) is of type UTF8String. It MAY + accompany a Result-Code AVP as a human readable error message. The + Error-Message AVP is not intended to be useful in real-time, and + SHOULD NOT be expected to be parsed by network entities. + +7.4. Error-Reporting-Host AVP + + The Error-Reporting-Host AVP (AVP Code 294) is of type + DiameterIdentity. This AVP contains the identity of the Diameter + host that sent the Result-Code AVP to a value other than 2001 + (Success), only if the host setting the Result-Code is different from + the one encoded in the Origin-Host AVP. This AVP is intended to be + used for troubleshooting purposes, and MUST be set when the Result- + Code AVP indicates a failure. + +7.5. Failed-AVP AVP + + The Failed-AVP AVP (AVP Code 279) is of type Grouped 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. + + The possible reasons for this AVP are the presence of an improperly + constructed AVP, an unsupported or unrecognized AVP, an invalid AVP + value, the omission of a required AVP, the presence of an explicitly + excluded AVP (see tables in Section 10), or the presence of two or + more occurrences of an AVP which is restricted to 0, 1, or 0-1 + occurrences. + + + +Calhoun, et al. Standards Track [Page 89] + +RFC 3588 Diameter Based Protocol September 2003 + + + A Diameter message MAY contain one Failed-AVP AVP, containing the + entire AVP that could not be processed successfully. If the failure + reason is omission of a required AVP, an AVP with the missing AVP + code, the missing vendor id, and a zero filled payload of the minimum + required length for the omitted AVP will be added. + + AVP Format + + <Failed-AVP> ::= < AVP Header: 279 > + 1* {AVP} + +7.6. Experimental-Result AVP + + The Experimental-Result AVP (AVP Code 297) is of type Grouped, and + indicates whether a particular vendor-specific request was completed + successfully or whether an error occurred. Its Data field has the + following ABNF grammar: + + AVP Format + + Experimental-Result ::= < AVP Header: 297 > + { Vendor-Id } + { Experimental-Result-Code } + + The Vendor-Id AVP (see Section 5.3.3) in this grouped AVP identifies + the vendor responsible for the assignment of the result code which + follows. All Diameter answer messages defined in vendor-specific + applications MUST include either one Result-Code AVP or one + Experimental-Result AVP. + +7.7. Experimental-Result-Code AVP + + The Experimental-Result-Code AVP (AVP Code 298) is of type Unsigned32 + and contains a vendor-assigned value representing the result of + processing the request. + + It is recommended that vendor-specific result codes follow the same + conventions given for the Result-Code AVP regarding the different + types of result codes and the handling of errors (for non 2xxx + values). + +8. Diameter User Sessions + + Diameter can provide two different types of services to applications. + The first involves authentication and authorization, and can + optionally make use of accounting. The second only makes use of + accounting. + + + + +Calhoun, et al. Standards Track [Page 90] + +RFC 3588 Diameter Based Protocol September 2003 + + + When a service makes use of the authentication and/or authorization + portion of an application, and a user requests access to the network, + the Diameter client issues an auth request to its local server. The + auth request is defined in a service specific Diameter application + (e.g., NASREQ). 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 for + a finite amount of time, and it is willing to extend the + authorization via a future request, it MUST add the Authorization- + Lifetime AVP to the answer message. The Authorization-Lifetime AVP + defines the maximum number of seconds a user MAY make use of the + resources before another authorization request is expected by the + server. The Auth-Grace-Period AVP contains the number of seconds + following the expiration of the Authorization-Lifetime, after which + the server will release all state information related to the user's + session. Note that if payment for services is expected by the + serving realm from the user's home realm, the Authorization-Lifetime + AVP, combined with the Auth-Grace-Period AVP, implies the maximum + length of the session the home realm is willing to be fiscally + responsible for. Services provided past the expiration of the + Authorization-Lifetime and Auth-Grace-Period AVPs are the + responsibility of the access device. Of course, the actual cost of + services rendered is clearly outside the scope of the protocol. + + An access device that does not expect to send a re-authorization or a + session termination request to the server MAY include the Auth- + Session-State AVP with the value set to NO_STATE_MAINTAINED as a hint + to the server. If the server accepts the hint, it agrees that since + no session termination message will be received once service to the + user is terminated, it cannot maintain state for the session. If the + answer message from the server contains a different value in the + Auth-Session-State AVP (or the default value if the AVP is absent), + the access device MUST follow the server's directives. Note that the + value NO_STATE_MAINTAINED MUST NOT be set in subsequent re- + authorization requests and answers. + + The base protocol does not include any authorization request + messages, since these are largely application-specific and are + defined in a Diameter application document. However, the base + protocol does define a set of messages that is used to terminate user + sessions. These are used to allow servers that maintain state + information to free resources. + + + + + +Calhoun, et al. Standards Track [Page 91] + +RFC 3588 Diameter Based Protocol September 2003 + + + When a service only makes use of the Accounting portion of the + Diameter protocol, even in combination with an application, the + Session-Id is still used to identify user sessions. However, the + session termination messages are not used, since a session is + signaled as being terminated by issuing an accounting stop message. + +8.1. Authorization Session State Machine + + This section contains a set of finite state machines, representing + the life cycle of Diameter sessions, and which MUST be observed by + all Diameter implementations that make use of the authentication + and/or authorization portion of a Diameter application. The term + Service-Specific below refers to a message defined in a Diameter + application (e.g., Mobile IPv4, NASREQ). + + There are four different authorization session state machines + supported in the Diameter base protocol. The first two describe a + session in which the server is maintaining session state, indicated + by the value of the Auth-Session-State AVP (or its absence). One + describes the session from a client perspective, the other from a + server perspective. The second two state machines are used when the + server does not maintain session state. Here again, one describes + the session from a client perspective, the other from a server + perspective. + + When a session is moved to the Idle state, any resources that were + allocated for the particular session must be released. Any event not + listed in the state machines MUST be considered as an error + condition, and an answer, if applicable, MUST be returned to the + originator of the message. + + In the state table, the event 'Failure to send X' means that the + Diameter agent is unable to send command X to the desired + destination. This could be due to the peer being down, or due to the + peer sending back a transient failure or temporary protocol error + notification DIAMETER_TOO_BUSY or DIAMETER_LOOP_DETECTED in the + Result-Code AVP of the corresponding Answer command. The event 'X + successfully sent' is the complement of 'Failure to send X'. + + + + + + + + + + + + + +Calhoun, et al. Standards Track [Page 92] + +RFC 3588 Diameter Based Protocol September 2003 + + + The following state machine is observed by a client when state is + maintained on the server: + + CLIENT, STATEFUL + State Event Action New State + ------------------------------------------------------------- + Idle Client or Device Requests Send Pending + access service + specific + auth req + + Idle ASR Received Send ASA Idle + for unknown session with + Result-Code + = UNKNOWN_ + SESSION_ID + + Pending Successful Service-specific Grant Open + authorization answer Access + received with default + Auth-Session-State value + + Pending Successful Service-specific Sent STR Discon + authorization answer received + but service not provided + + Pending Error processing successful Sent STR Discon + Service-specific authorization + answer + + Pending Failed Service-specific Cleanup Idle + authorization answer received + + Open User or client device Send Open + requests access to service service + specific + auth req + + Open Successful Service-specific Provide Open + authorization answer received Service + + Open Failed Service-specific Discon. Idle + authorization answer user/device + received. + + Open Session-Timeout Expires on Send STR Discon + Access Device + + + + +Calhoun, et al. Standards Track [Page 93] + +RFC 3588 Diameter Based Protocol September 2003 + + + Open ASR Received, Send ASA Discon + client will comply with with + request to end the session Result-Code + = SUCCESS, + Send STR. + + Open ASR Received, Send ASA Open + client will not comply with with + request to end the session Result-Code + != SUCCESS + + Open Authorization-Lifetime + Send STR Discon + Auth-Grace-Period expires on + access device + + Discon ASR Received Send ASA Discon + + Discon STA Received Discon. Idle + user/device + + The following state machine is observed by a server when it is + maintaining state for the session: + + SERVER, STATEFUL + State Event Action New State + ------------------------------------------------------------- + Idle Service-specific authorization Send Open + request received, and successful + user is authorized serv. + specific answer + + Idle Service-specific authorization Send Idle + request received, and failed serv. + user is not authorized specific answer + + Open Service-specific authorization Send Open + request received, and user successful + is authorized serv. specific + answer + + Open Service-specific authorization Send Idle + request received, and user failed serv. + is not authorized specific + answer, + Cleanup + + Open Home server wants to Send ASR Discon + terminate the service + + + +Calhoun, et al. Standards Track [Page 94] + +RFC 3588 Diameter Based Protocol September 2003 + + + Open Authorization-Lifetime (and Cleanup Idle + Auth-Grace-Period) expires + on home server. + + Open Session-Timeout expires on Cleanup Idle + home server + + Discon Failure to send ASR Wait, Discon + resend ASR + + Discon ASR successfully sent and Cleanup Idle + ASA Received with Result-Code + + Not ASA Received None No Change. + Discon + + Any STR Received Send STA, Idle + Cleanup. + + The following state machine is observed by a client when state is not + maintained on the server: + + CLIENT, STATELESS + State Event Action New State + ------------------------------------------------------------- + Idle Client or Device Requests Send Pending + access service + specific + auth req + + Pending Successful Service-specific Grant Open + authorization answer Access + received with Auth-Session- + State set to + NO_STATE_MAINTAINED + + Pending Failed Service-specific Cleanup Idle + authorization answer + received + + Open Session-Timeout Expires on Discon. Idle + Access Device user/device + + Open Service to user is terminated Discon. Idle + user/device + + + + + + +Calhoun, et al. Standards Track [Page 95] + +RFC 3588 Diameter Based Protocol September 2003 + + + The following state machine is observed by a server when it is not + maintaining state for the session: + + SERVER, STATELESS + State Event Action New State + ------------------------------------------------------------- + Idle Service-specific authorization Send serv. Idle + request received, and specific + successfully processed answer + +8.2. Accounting Session State Machine + + The following state machines MUST be supported for applications that + have an accounting portion or that require only accounting services. + The first state machine is to be observed by clients. + + See Section 9.7 for Accounting Command Codes and Section 9.8 for + Accounting AVPs. + + The server side in the accounting state machine depends in some cases + on the particular application. The Diameter base protocol defines a + default state machine that MUST be followed by all applications that + have not specified other state machines. This is the second state + machine in this section described below. + + The default server side state machine requires the reception of + accounting records in any order and at any time, and does not place + any standards requirement on the processing of these records. + Implementations of Diameter MAY perform checking, ordering, + correlation, fraud detection, and other tasks based on these records. + Both base Diameter AVPs as well as application specific AVPs MAY be + inspected as a part of these tasks. The tasks can happen either + immediately after record reception or in a post-processing phase. + However, as these tasks are typically application or even policy + dependent, they are not standardized by the Diameter specifications. + Applications MAY define requirements on when to accept accounting + records based on the used value of Accounting-Realtime-Required AVP, + credit limits checks, and so on. + + However, the Diameter base protocol defines one optional server side + state machine that MAY be followed by applications that require + keeping track of the session state at the accounting server. Note + that such tracking is incompatible with the ability to sustain long + duration connectivity problems. Therefore, the use of this state + machine is recommended only in applications where the value of the + Accounting-Realtime-Required AVP is DELIVER_AND_GRANT, and hence + accounting connectivity problems are required to cause the serviced + user to be disconnected. Otherwise, records produced by the client + + + +Calhoun, et al. Standards Track [Page 96] + +RFC 3588 Diameter Based Protocol September 2003 + + + may be lost by the server which no longer accepts them after the + connectivity is re-established. This state machine is the third + state machine in this section. The state machine is supervised by a + supervision session timer Ts, which the value should be reasonably + higher than the Acct_Interim_Interval value. Ts MAY be set to two + times the value of the Acct_Interim_Interval so as to avoid the + accounting session in the Diameter server to change to Idle state in + case of short transient network failure. + + Any event not listed in the state machines MUST be considered as an + error condition, and a corresponding answer, if applicable, MUST be + returned to the originator of the message. + + In the state table, the event 'Failure to send' means that the + Diameter client is unable to communicate with the desired + destination. This could be due to the peer being down, or due to the + peer sending back a transient failure or temporary protocol error + notification DIAMETER_OUT_OF_SPACE, DIAMETER_TOO_BUSY, or + DIAMETER_LOOP_DETECTED in the Result-Code AVP of the Accounting + Answer command. + + The event 'Failed answer' means that the Diameter client received a + non-transient failure notification in the Accounting Answer command. + + Note that the action 'Disconnect user/dev' MUST have an effect also + to the authorization session state table, e.g., cause the STR message + to be sent, if the given application has both + authentication/authorization and accounting portions. + + The states PendingS, PendingI, PendingL, PendingE and PendingB stand + for pending states to wait for an answer to an accounting request + related to a Start, Interim, Stop, Event or buffered record, + respectively. + + CLIENT, ACCOUNTING + State Event Action New State + ------------------------------------------------------------- + Idle Client or device requests Send PendingS + access accounting + start req. + + Idle Client or device requests Send PendingE + a one-time service accounting + event req + + Idle Records in storage Send PendingB + record + + + + +Calhoun, et al. Standards Track [Page 97] + +RFC 3588 Diameter Based Protocol September 2003 + + + PendingS Successful accounting Open + start answer received + + PendingS Failure to send and buffer Store Open + space available and realtime Start + not equal to DELIVER_AND_GRANT Record + + PendingS Failure to send and no buffer Open + space available and realtime + equal to GRANT_AND_LOSE + + PendingS Failure to send and no buffer Disconnect Idle + space available and realtime user/dev + not equal to + GRANT_AND_LOSE + + PendingS Failed accounting start answer Open + received and realtime equal + to GRANT_AND_LOSE + + PendingS Failed accounting start answer Disconnect Idle + received and realtime not user/dev + equal to GRANT_AND_LOSE + + PendingS User service terminated Store PendingS + stop + record + + Open Interim interval elapses Send PendingI + accounting + interim + record + Open User service terminated Send PendingL + accounting + stop req. + + PendingI Successful accounting interim Open + answer received + + PendingI Failure to send and (buffer Store Open + space available or old record interim + can be overwritten) and record + realtime not equal to + DELIVER_AND_GRANT + + PendingI Failure to send and no buffer Open + space available and realtime + equal to GRANT_AND_LOSE + + + +Calhoun, et al. Standards Track [Page 98] + +RFC 3588 Diameter Based Protocol September 2003 + + + PendingI Failure to send and no buffer Disconnect Idle + space available and realtime user/dev + not equal to GRANT_AND_LOSE + + PendingI Failed accounting interim Open + answer received and realtime + equal to GRANT_AND_LOSE + + PendingI Failed accounting interim Disconnect Idle + answer received and realtime user/dev + not equal to GRANT_AND_LOSE + + PendingI User service terminated Store PendingI + stop + record + PendingE Successful accounting Idle + event answer received + + PendingE Failure to send and buffer Store Idle + space available event + record + + PendingE Failure to send and no buffer Idle + space available + + PendingE Failed accounting event answer Idle + received + + PendingB Successful accounting answer Delete Idle + received record + + PendingB Failure to send Idle + + PendingB Failed accounting answer Delete Idle + received record + + PendingL Successful accounting Idle + stop answer received + + PendingL Failure to send and buffer Store Idle + space available stop + record + + PendingL Failure to send and no buffer Idle + space available + + PendingL Failed accounting stop answer Idle + received + + + +Calhoun, et al. Standards Track [Page 99] + +RFC 3588 Diameter Based Protocol September 2003 + + + SERVER, STATELESS ACCOUNTING + State Event Action New State + ------------------------------------------------------------- + + Idle Accounting start request Send Idle + received, and successfully accounting + processed. start + answer + + Idle Accounting event request Send Idle + received, and successfully accounting + processed. event + answer + + Idle Interim record received, Send Idle + and successfully processed. accounting + interim + answer + + Idle Accounting stop request Send Idle + received, and successfully accounting + processed stop answer + + Idle Accounting request received, Send Idle + no space left to store accounting + records answer, + Result-Code + = OUT_OF_ + SPACE + + SERVER, STATEFUL ACCOUNTING + State Event Action New State + ------------------------------------------------------------- + + Idle Accounting start request Send Open + received, and successfully accounting + processed. start + answer, + Start Ts + + Idle Accounting event request Send Idle + received, and successfully accounting + processed. event + answer + + + + + + + +Calhoun, et al. Standards Track [Page 100] + +RFC 3588 Diameter Based Protocol September 2003 + + + Idle Accounting request received, Send Idle + no space left to store accounting + records answer, + Result-Code + = OUT_OF_ + SPACE + + Open Interim record received, Send Open + and successfully processed. accounting + interim + answer, + Restart Ts + + Open Accounting stop request Send Idle + received, and successfully accounting + processed stop answer, + Stop Ts + + Open Accounting request received, Send Idle + no space left to store accounting + records answer, + Result-Code + = OUT_OF_ + SPACE, + Stop Ts + + Open Session supervision timer Ts Stop Ts Idle + expired + +8.3. Server-Initiated Re-Auth + + A Diameter server may initiate a re-authentication and/or re- + authorization service for a particular session by issuing a Re-Auth- + Request (RAR). + + For example, for pre-paid services, the Diameter server that + originally authorized a session may need some confirmation that the + user is still using the services. + + An access device that receives a RAR message with Session-Id equal to + a currently active session MUST initiate a re-auth towards the user, + if the service supports this particular feature. Each Diameter + application MUST state whether service-initiated re-auth is + supported, since some applications do not allow access devices to + prompt the user for re-auth. + + + + + + +Calhoun, et al. Standards Track [Page 101] + +RFC 3588 Diameter Based Protocol September 2003 + + +8.3.1. Re-Auth-Request + + The Re-Auth-Request (RAR), indicated by the Command-Code set to 258 + and the message flags' 'R' bit set, may be sent by any server to the + access device that is providing session service, to request that the + user be re-authenticated and/or re-authorized. + + Message Format + + <RAR> ::= < Diameter Header: 258, REQ, PXY > + < Session-Id > + { Origin-Host } + { Origin-Realm } + { Destination-Realm } + { Destination-Host } + { Auth-Application-Id } + { Re-Auth-Request-Type } + [ User-Name ] + [ Origin-State-Id ] + * [ Proxy-Info ] + * [ Route-Record ] + * [ AVP ] + +8.3.2. Re-Auth-Answer + + The Re-Auth-Answer (RAA), indicated by the Command-Code set to 258 + and the message flags' 'R' bit clear, is sent in response to the RAR. + The Result-Code AVP MUST be present, and indicates the disposition of + the request. + + A successful RAA message MUST be followed by an application-specific + authentication and/or authorization message. + + + + + + + + + + + + + + + + + + + +Calhoun, et al. Standards Track [Page 102] + +RFC 3588 Diameter Based Protocol September 2003 + + + Message Format + + <RAA> ::= < Diameter Header: 258, PXY > + < Session-Id > + { Result-Code } + { Origin-Host } + { Origin-Realm } + [ User-Name ] + [ Origin-State-Id ] + [ Error-Message ] + [ Error-Reporting-Host ] + * [ Failed-AVP ] + * [ Redirect-Host ] + [ Redirect-Host-Usage ] + [ Redirect-Host-Cache-Time ] + * [ Proxy-Info ] + * [ AVP ] + +8.4. Session Termination + + It is necessary for a Diameter server that authorized a session, for + which it is maintaining state, to be notified when that session is no + longer active, both for tracking purposes as well as to allow + stateful agents to release any resources that they may have provided + for the user's session. For sessions whose state is not being + maintained, this section is not used. + + When a user session that required Diameter authorization terminates, + the access device that provided the service MUST issue a Session- + Termination-Request (STR) message to the Diameter server that + authorized the service, to notify it that the session is no longer + active. An STR MUST be issued when a user session terminates for any + reason, including user logoff, expiration of Session-Timeout, + administrative action, termination upon receipt of an Abort-Session- + Request (see below), orderly shutdown of the access device, etc. + + The access device also MUST issue an STR for a session that was + authorized but never actually started. This could occur, for + example, due to a sudden resource shortage in the access device, or + because the access device is unwilling to provide the type of service + requested in the authorization, or because the access device does not + support a mandatory AVP returned in the authorization, etc. + + It is also possible that a session that was authorized is never + actually started due to action of a proxy. For example, a proxy may + modify an authorization answer, converting the result from success to + failure, prior to forwarding the message to the access device. If + the answer did not contain an Auth-Session-State AVP with the value + + + +Calhoun, et al. Standards Track [Page 103] + +RFC 3588 Diameter Based Protocol September 2003 + + + NO_STATE_MAINTAINED, a proxy that causes an authorized session not to + be started MUST issue an STR to the Diameter server that authorized + the session, since the access device has no way of knowing that the + session had been authorized. + + A Diameter server that receives an STR message MUST clean up + resources (e.g., session state) associated with the Session-Id + specified in the STR, and return a Session-Termination-Answer. + + A Diameter server also MUST clean up resources when the Session- + Timeout expires, or when the Authorization-Lifetime and the Auth- + Grace-Period AVPs expires without receipt of a re-authorization + request, regardless of whether an STR for that session is received. + The access device is not expected to provide service beyond the + expiration of these timers; thus, expiration of either of these + timers implies that the access device may have unexpectedly shut + down. + +8.4.1. Session-Termination-Request + + The Session-Termination-Request (STR), indicated by the Command-Code + set to 275 and the Command Flags' 'R' bit set, is sent by the access + device to inform the Diameter Server that an authenticated and/or + authorized session is being terminated. + + Message Format + + <STR> ::= < Diameter Header: 275, REQ, PXY > + < Session-Id > + { Origin-Host } + { Origin-Realm } + { Destination-Realm } + { Auth-Application-Id } + { Termination-Cause } + [ User-Name ] + [ Destination-Host ] + * [ Class ] + [ Origin-State-Id ] + * [ Proxy-Info ] + * [ Route-Record ] + * [ AVP ] + + + + + + + + + + +Calhoun, et al. Standards Track [Page 104] + +RFC 3588 Diameter Based Protocol September 2003 + + +8.4.2. Session-Termination-Answer + + The Session-Termination-Answer (STA), indicated by the Command-Code + set to 275 and the message flags' 'R' bit clear, is sent by the + Diameter Server to acknowledge the notification that the session has + been terminated. The Result-Code AVP MUST be present, and MAY + contain an indication that an error occurred while servicing the STR. + + Upon sending or receipt of the STA, the Diameter Server MUST release + all resources for the session indicated by the Session-Id AVP. Any + intermediate server in the Proxy-Chain MAY also release any + resources, if necessary. + + Message Format + + <STA> ::= < Diameter Header: 275, PXY > + < Session-Id > + { Result-Code } + { Origin-Host } + { Origin-Realm } + [ User-Name ] + * [ Class ] + [ Error-Message ] + [ Error-Reporting-Host ] + * [ Failed-AVP ] + [ Origin-State-Id ] + * [ Redirect-Host ] + [ Redirect-Host-Usage ] + ^ + [ Redirect-Max-Cache-Time ] + * [ Proxy-Info ] + * [ AVP ] + +8.5. Aborting a Session + + A Diameter server may request that the access device stop providing + service for a particular session by issuing an Abort-Session-Request + (ASR). + + For example, the Diameter server that originally authorized the + session may be required to cause that session to be stopped for + credit or other reasons that were not anticipated when the session + was first authorized. On the other hand, an operator may maintain a + management server for the purpose of issuing ASRs to administratively + remove users from the network. + + An access device that receives an ASR with Session-ID equal to a + currently active session MAY stop the session. Whether the access + + + +Calhoun, et al. Standards Track [Page 105] + +RFC 3588 Diameter Based Protocol September 2003 + + + device stops the session or not is implementation- and/or + configuration-dependent. For example, an access device may honor + ASRs from certain agents only. In any case, the access device MUST + respond with an Abort-Session-Answer, including a Result-Code AVP to + indicate what action it took. + + Note that if the access device does stop the session upon receipt of + an ASR, it issues an STR to the authorizing server (which may or may + not be the agent issuing the ASR) just as it would if the session + were terminated for any other reason. + +8.5.1. Abort-Session-Request + + The Abort-Session-Request (ASR), indicated by the Command-Code set to + 274 and the message flags' 'R' bit set, may be sent by any server to + the access device that is providing session service, to request that + the session identified by the Session-Id be stopped. + + Message Format + + <ASR> ::= < Diameter Header: 274, REQ, PXY > + < Session-Id > + { Origin-Host } + { Origin-Realm } + { Destination-Realm } + { Destination-Host } + { Auth-Application-Id } + [ User-Name ] + [ Origin-State-Id ] + * [ Proxy-Info ] + * [ Route-Record ] + * [ AVP ] + +8.5.2. Abort-Session-Answer + + The Abort-Session-Answer (ASA), indicated by the Command-Code set to + 274 and the message flags' 'R' bit clear, is sent in response to the + ASR. The Result-Code AVP MUST be present, and indicates the + disposition of the request. + + If the session identified by Session-Id in the ASR was successfully + terminated, Result-Code is set to DIAMETER_SUCCESS. If the session + is not currently active, Result-Code is set to + DIAMETER_UNKNOWN_SESSION_ID. If the access device does not stop the + session for any other reason, Result-Code is set to + DIAMETER_UNABLE_TO_COMPLY. + + + + + +Calhoun, et al. Standards Track [Page 106] + +RFC 3588 Diameter Based Protocol September 2003 + + + Message Format + + <ASA> ::= < Diameter Header: 274, PXY > + < Session-Id > + { Result-Code } + { Origin-Host } + { Origin-Realm } + [ User-Name ] + [ Origin-State-Id ] + [ Error-Message ] + [ Error-Reporting-Host ] + * [ Failed-AVP ] + * [ Redirect-Host ] + [ Redirect-Host-Usage ] + [ Redirect-Max-Cache-Time ] + * [ Proxy-Info ] + * [ AVP ] + +8.6. Inferring Session Termination from Origin-State-Id + + Origin-State-Id is used to allow rapid detection of terminated + sessions for which no STR would have been issued, due to + unanticipated shutdown of an access device. + + By including Origin-State-Id in CER/CEA messages, an access device + allows a next-hop server to determine immediately upon connection + whether the device has lost its sessions since the last connection. + + By including Origin-State-Id in request messages, an access device + also allows a server with which it communicates via proxy to make + such a determination. However, a server that is not directly + connected with the access device will not discover that the access + device has been restarted unless and until it receives a new request + from the access device. Thus, use of this mechanism across proxies + is opportunistic rather than reliable, but useful nonetheless. + + When a Diameter server receives an Origin-State-Id that is greater + than the Origin-State-Id previously received from the same issuer, it + may assume that the issuer has lost state since the previous message + and that all sessions that were active under the lower Origin-State- + Id have been terminated. The Diameter server MAY clean up all + session state associated with such lost sessions, and MAY also issues + STRs for all such lost sessions that were authorized on upstream + servers, to allow session state to be cleaned up globally. + + + + + + + +Calhoun, et al. Standards Track [Page 107] + +RFC 3588 Diameter Based Protocol September 2003 + + +8.7. Auth-Request-Type AVP + + The Auth-Request-Type AVP (AVP Code 274) is of type Enumerated and is + included in application-specific auth requests to inform the peers + whether a user is to be authenticated only, authorized only or both. + Note any value other than both MAY cause RADIUS interoperability + issues. The following values are defined: + + AUTHENTICATE_ONLY 1 + The request being sent is for authentication only, and MUST + contain the relevant application specific authentication AVPs that + are needed by the Diameter server to authenticate the user. + + AUTHORIZE_ONLY 2 + The request being sent is for authorization only, and MUST contain + the application specific authorization AVPs that are necessary to + identify the service being requested/offered. + + AUTHORIZE_AUTHENTICATE 3 + The request contains a request for both authentication and + authorization. The request MUST include both the relevant + application specific authentication information, and authorization + information necessary to identify the service being + requested/offered. + +8.8. Session-Id AVP + + The Session-Id AVP (AVP Code 263) is of type UTF8String and is used + to identify a specific session (see Section 8). 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 + Diameter Header (see Section 3). + + The Session-Id MUST be globally and eternally unique, as it is meant + to uniquely identify a user session without reference to any other + information, and may be needed to correlate historical authentication + information with accounting information. The Session-Id includes a + mandatory portion and an implementation-defined portion; a + recommended format for the implementation-defined portion is outlined + below. + + The Session-Id MUST begin with the sender's identity encoded in the + DiameterIdentity type (see Section 4.4). The remainder of the + Session-Id is delimited by a ";" character, and MAY be any sequence + that the client can guarantee to be eternally unique; however, the + following format is recommended, (square brackets [] indicate an + optional element): + + + +Calhoun, et al. Standards Track [Page 108] + +RFC 3588 Diameter Based Protocol September 2003 + + + <DiameterIdentity>;<high 32 bits>;<low 32 bits>[;<optional value>] + + <high 32 bits> and <low 32 bits> are decimal representations of the + high and low 32 bits of a monotonically increasing 64-bit value. The + 64-bit value is rendered in two part to simplify formatting by 32-bit + processors. At startup, the high 32 bits of the 64-bit value MAY be + initialized to the time, and the low 32 bits MAY be initialized to + zero. This will for practical purposes eliminate the possibility of + overlapping Session-Ids after a reboot, assuming the reboot process + takes longer than a second. Alternatively, an implementation MAY + keep track of the increasing value in non-volatile memory. + + <optional value> is implementation specific but may include a modem's + device Id, a layer 2 address, timestamp, etc. + + Example, in which there is no optional value: + accesspoint7.acme.com;1876543210;523 + + Example, in which there is an optional value: + accesspoint7.acme.com;1876543210;523;mobile@200.1.1.88 + + The Session-Id is created by the Diameter application initiating the + session, which in most cases is done by the client. Note that a + Session-Id MAY be used for both the authorization and accounting + commands of a given application. + +8.9. Authorization-Lifetime AVP + + The Authorization-Lifetime AVP (AVP Code 291) is of type Unsigned32 + and contains the maximum number of seconds of service to be provided + to the user before the user is to be re-authenticated and/or re- + authorized. Great care should be taken when the Authorization- + Lifetime value is determined, since a low, non-zero, value could + create significant Diameter traffic, which could congest both the + network and the agents. + + A value of zero (0) means that immediate re-auth is necessary by the + access device. This is typically used in cases where multiple + authentication methods are used, and a successful auth response with + this AVP set to zero is used to signal that the next authentication + method is to be immediately initiated. The absence of this AVP, or a + value of all ones (meaning all bits in the 32 bit field are set to + one) means no re-auth is expected. + + If both this AVP and the Session-Timeout AVP are present in a + message, the value of the latter MUST NOT be smaller than the + Authorization-Lifetime AVP. + + + + +Calhoun, et al. Standards Track [Page 109] + +RFC 3588 Diameter Based Protocol September 2003 + + + An Authorization-Lifetime AVP MAY be present in re-authorization + messages, and contains the number of seconds the user is authorized + to receive service from the time the re-auth answer message is + received by the access device. + + This AVP MAY be provided by the client as a hint of the maximum + lifetime that it is willing to accept. However, the server MAY + return a value that is equal to, or smaller, than the one provided by + the client. + +8.10. Auth-Grace-Period AVP + + The Auth-Grace-Period AVP (AVP Code 276) is of type Unsigned32 and + contains the number of seconds the Diameter server will wait + following the expiration of the Authorization-Lifetime AVP before + cleaning up resources for the session. + +8.11. Auth-Session-State AVP + + The Auth-Session-State AVP (AVP Code 277) is of type Enumerated and + specifies whether state is maintained for a particular session. The + client MAY include this AVP in requests as a hint to the server, but + the value in the server's answer message is binding. The following + values are supported: + + STATE_MAINTAINED 0 + This value is used to specify that session state is being + maintained, and the access device MUST issue a session termination + message when service to the user is terminated. This is the + default value. + + NO_STATE_MAINTAINED 1 + This value is used to specify that no session termination messages + will be sent by the access device upon expiration of the + Authorization-Lifetime. + +8.12. Re-Auth-Request-Type AVP + + The Re-Auth-Request-Type AVP (AVP Code 285) is of type Enumerated and + is included in application-specific auth answers to inform the client + of the action expected upon expiration of the Authorization-Lifetime. + If the answer message contains an Authorization-Lifetime AVP with a + positive value, the Re-Auth-Request-Type AVP MUST be present in an + answer message. The following values are defined: + + + + + + + +Calhoun, et al. Standards Track [Page 110] + +RFC 3588 Diameter Based Protocol September 2003 + + + AUTHORIZE_ONLY 0 + An authorization only re-auth is expected upon expiration of the + Authorization-Lifetime. This is the default value if the AVP is + not present in answer messages that include the Authorization- + Lifetime. + + AUTHORIZE_AUTHENTICATE 1 + An authentication and authorization re-auth is expected upon + expiration of the Authorization-Lifetime. + +8.13. Session-Timeout AVP + + The Session-Timeout AVP (AVP Code 27) [RADIUS] is of type Unsigned32 + and contains the maximum number of seconds of service to be provided + to the user before termination of the session. When both the + Session-Timeout and the Authorization-Lifetime AVPs are present in an + answer message, the former MUST be equal to or greater than the value + of the latter. + + A session that terminates on an access device due to the expiration + of the Session-Timeout MUST cause an STR to be issued, unless both + the access device and the home server had previously agreed that no + session termination messages would be sent (see Section 8.9). + + A Session-Timeout AVP MAY be present in a re-authorization answer + message, and contains the remaining number of seconds from the + beginning of the re-auth. + + A value of zero, or the absence of this AVP, 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 + timeout that it is willing to accept. However, the server MAY return + a value that is equal to, or smaller, than the one provided by the + client. + +8.14. User-Name AVP + + The User-Name AVP (AVP Code 1) [RADIUS] is of type UTF8String, which + contains the User-Name, in a format consistent with the NAI + specification [NAI]. + +8.15. Termination-Cause AVP + + The Termination-Cause AVP (AVP Code 295) is of type Enumerated, and + is used to indicate the reason why a session was terminated on the + access device. The following values are defined: + + + + +Calhoun, et al. Standards Track [Page 111] + +RFC 3588 Diameter Based Protocol September 2003 + + + DIAMETER_LOGOUT 1 + The user initiated a disconnect + + DIAMETER_SERVICE_NOT_PROVIDED 2 + This value is used when the user disconnected prior to the receipt + of the authorization answer message. + + DIAMETER_BAD_ANSWER 3 + This value indicates that the authorization answer received by the + access device was not processed successfully. + + DIAMETER_ADMINISTRATIVE 4 + The user was not granted access, or was disconnected, due to + administrative reasons, such as the receipt of a Abort-Session- + Request message. + + DIAMETER_LINK_BROKEN 5 + The communication to the user was abruptly disconnected. + + DIAMETER_AUTH_EXPIRED 6 + The user's access was terminated since its authorized session time + has expired. + + DIAMETER_USER_MOVED 7 + The user is receiving services from another access device. + + DIAMETER_SESSION_TIMEOUT 8 + The user's session has timed out, and service has been terminated. + +8.16. Origin-State-Id AVP + + The Origin-State-Id AVP (AVP Code 278), of type Unsigned32, is a + monotonically increasing value that is advanced whenever a Diameter + entity restarts with loss of previous state, for example upon reboot. + Origin-State-Id MAY be included in any Diameter message, including + CER. + + A Diameter entity issuing this AVP MUST create a higher value for + this AVP each time its state is reset. A Diameter entity MAY set + Origin-State-Id to the time of startup, or it MAY use an incrementing + counter retained in non-volatile memory across restarts. + + The Origin-State-Id, if present, MUST reflect the state of the entity + indicated by Origin-Host. If a proxy modifies Origin-Host, it MUST + either remove Origin-State-Id or modify it appropriately as well. + + + + + + +Calhoun, et al. Standards Track [Page 112] + +RFC 3588 Diameter Based Protocol September 2003 + + + Typically, Origin-State-Id is used by an access device that always + starts up with no active sessions; that is, any session active prior + to restart will have been lost. By including Origin-State-Id in a + message, it allows other Diameter entities to infer that sessions + associated with a lower Origin-State-Id are no longer active. If an + access device does not intend for such inferences to be made, it MUST + either not include Origin-State-Id in any message, or set its value + to 0. + +8.17. Session-Binding AVP + + The Session-Binding AVP (AVP Code 270) is of type Unsigned32, and MAY + be present in application-specific authorization answer messages. If + present, this AVP MAY inform the Diameter client that all future + application-specific re-auth messages for this session MUST be sent + to the same authorization server. This AVP MAY also specify that a + Session-Termination-Request message for this session MUST be sent to + the same authorizing server. + + This field is a bit mask, and the following bits have been defined: + + RE_AUTH 1 + When set, future re-auth messages for this session MUST NOT + include the Destination-Host AVP. When cleared, the default + value, the Destination-Host AVP MUST be present in all re-auth + messages for this session. + + STR 2 + When set, the STR message for this session MUST NOT include the + Destination-Host AVP. When cleared, the default value, the + Destination-Host AVP MUST be present in the STR message for this + session. + + ACCOUNTING 4 + When set, all accounting messages for this session MUST NOT + include the Destination-Host AVP. When cleared, the default + value, the Destination-Host AVP, if known, MUST be present in all + accounting messages for this session. + +8.18. Session-Server-Failover AVP + + The Session-Server-Failover AVP (AVP Code 271) is of type Enumerated, + and MAY be present in application-specific authorization answer + messages that either do not include the Session-Binding AVP or + include the Session-Binding AVP with any of the bits set to a zero + value. If present, this AVP MAY inform the Diameter client that if a + + + + + +Calhoun, et al. Standards Track [Page 113] + +RFC 3588 Diameter Based Protocol September 2003 + + + re-auth or STR message fails due to a delivery problem, the Diameter + client SHOULD issue a subsequent message without the Destination-Host + AVP. When absent, the default value is REFUSE_SERVICE. + + The following values are supported: + + REFUSE_SERVICE 0 + If either the re-auth or the STR message delivery fails, terminate + service with the user, and do not attempt any subsequent attempts. + + TRY_AGAIN 1 + If either the re-auth or the STR message delivery fails, resend + the failed message without the Destination-Host AVP present. + + ALLOW_SERVICE 2 + If re-auth message delivery fails, assume that re-authorization + succeeded. If STR message delivery fails, terminate the session. + + TRY_AGAIN_ALLOW_SERVICE 3 + If either the re-auth or the STR message delivery fails, resend + the failed message without the Destination-Host AVP present. If + the second delivery fails for re-auth, assume re-authorization + succeeded. If the second delivery fails for STR, terminate the + session. + +8.19. Multi-Round-Time-Out AVP + + The Multi-Round-Time-Out AVP (AVP Code 272) is of type Unsigned32, + and SHOULD be present in application-specific authorization answer + messages whose Result-Code AVP is set to DIAMETER_MULTI_ROUND_AUTH. + This AVP contains the maximum number of seconds that the access + device MUST provide the user in responding to an authentication + request. + +8.20. Class AVP + + The Class AVP (AVP Code 25) is of type OctetString and is used to by + Diameter servers to return state information to the access device. + When one or more Class AVPs are present in application-specific + authorization answer messages, they MUST be present in subsequent + re-authorization, session termination and accounting messages. Class + AVPs found in a re-authorization answer message override the ones + found in any previous authorization answer message. Diameter server + implementations SHOULD NOT return Class AVPs that require more than + 4096 bytes of storage on the Diameter client. A Diameter client that + receives Class AVPs whose size exceeds local available storage MUST + terminate the session. + + + + +Calhoun, et al. Standards Track [Page 114] + +RFC 3588 Diameter Based Protocol September 2003 + + +8.21. Event-Timestamp AVP + + The Event-Timestamp (AVP Code 55) is of type Time, and MAY be + included in an Accounting-Request and Accounting-Answer messages to + record the time that the reported event occurred, in seconds since + January 1, 1900 00:00 UTC. + +9. Accounting + + This accounting protocol is based on a server directed model with + capabilities for real-time delivery of accounting information. + Several fault resilience methods [ACCMGMT] have been built in to the + protocol in order minimize loss of accounting data in various fault + situations and under different assumptions about the capabilities of + the used devices. + +9.1. Server Directed Model + + The server directed model means that the device generating the + accounting data gets information from either the authorization server + (if contacted) or the accounting server regarding the way accounting + data shall be forwarded. This information includes accounting record + timeliness requirements. + + As discussed in [ACCMGMT], real-time transfer of accounting records + is a requirement, such as the need to perform credit limit checks and + fraud detection. Note that batch accounting is not a requirement, + and is therefore not supported by Diameter. Should batched + accounting be required in the future, a new Diameter application will + need to be created, or it could be handled using another protocol. + Note, however, that even if at the Diameter layer accounting requests + are processed one by one, transport protocols used under Diameter + typically batch several requests in the same packet under heavy + traffic conditions. This may be sufficient for many applications. + + The authorization server (chain) directs the selection of proper + transfer strategy, based on its knowledge of the user and + relationships of roaming partnerships. The server (or agents) uses + the Acct-Interim-Interval and Accounting-Realtime-Required AVPs to + control the operation of the Diameter peer operating as a client. + The Acct-Interim-Interval AVP, when present, instructs the Diameter + node acting as a client to produce accounting records continuously + even during a session. Accounting-Realtime-Required AVP is used to + control the behavior of the client when the transfer of accounting + records from the Diameter client is delayed or unsuccessful. + + + + + + +Calhoun, et al. Standards Track [Page 115] + +RFC 3588 Diameter Based Protocol September 2003 + + + The Diameter accounting server MAY override the interim interval or + the realtime requirements by including the Acct-Interim-Interval or + Accounting-Realtime-Required AVP in the Accounting-Answer message. + When one of these AVPs is present, the latest value received SHOULD + be used in further accounting activities for the same session. + +9.2. Protocol Messages + + A Diameter node that receives a successful authentication and/or + authorization messages from the Home AAA server MUST collect + accounting information for the session. The Accounting-Request + message is used to transmit the accounting information to the Home + AAA server, which MUST reply with the Accounting-Answer message to + confirm reception. The Accounting-Answer message includes the + Result-Code AVP, which MAY indicate that an error was present in the + accounting message. A rejected Accounting-Request message MAY cause + the user's session to be terminated, depending on the value of the + Accounting-Realtime-Required AVP received earlier for the session in + question. + + Each Diameter Accounting protocol message MAY be compressed, in order + to reduce network bandwidth usage. If IPsec and IKE are used to + secure the Diameter session, then IP compression [IPComp] MAY be used + and IKE [IKE] MAY be used to negotiate the compression parameters. + If TLS is used to secure the Diameter session, then TLS compression + [TLS] MAY be used. + +9.3. Application document requirements + + Each Diameter application (e.g., NASREQ, MobileIP), MUST define their + Service-Specific AVPs that MUST be present in the Accounting-Request + message in a section entitled "Accounting AVPs". The application + MUST assume that the AVPs described in this document will be present + in all Accounting messages, so only their respective service-specific + AVPs need to be defined in this section. + +9.4. Fault Resilience + + Diameter Base protocol mechanisms are used to overcome small message + loss and network faults of temporary nature. + + Diameter peers acting as clients MUST implement the use of failover + to guard against server failures and certain network failures. + Diameter peers acting as agents or related off-line processing + systems MUST detect duplicate accounting records caused by the + sending of same record to several servers and duplication of messages + + + + + +Calhoun, et al. Standards Track [Page 116] + +RFC 3588 Diameter Based Protocol September 2003 + + + in transit. This detection MUST be based on the inspection of the + Session-Id and Accounting-Record-Number AVP pairs. Appendix C + discusses duplicate detection needs and implementation issues. + + Diameter clients MAY have non-volatile memory for the safe storage of + accounting records over reboots or extended network failures, network + partitions, and server failures. If such memory is available, the + client SHOULD store new accounting records there as soon as the + records are created and until a positive acknowledgement of their + reception from the Diameter Server has been received. Upon a reboot, + the client MUST starting sending the records in the non-volatile + memory to the accounting server with appropriate modifications in + termination cause, session length, and other relevant information in + the records. + + A further application of this protocol may include AVPs to control + how many accounting records may at most be stored in the Diameter + client without committing them to the non-volatile memory or + transferring them to the Diameter server. + + The client SHOULD NOT remove the accounting data from any of its + memory areas before the correct Accounting-Answer has been received. + The client MAY remove oldest, undelivered or yet unacknowledged + accounting data if it runs out of resources such as memory. It is an + implementation dependent matter for the client to accept new sessions + under this condition. + +9.5. Accounting Records + + In all accounting records, the Session-Id AVP MUST be present; the + User-Name AVP MUST be present if it is available to the Diameter + client. If strong authentication across agents is required, end-to- + end security may be used for authentication purposes. + + Different types of accounting records are sent depending on the + actual type of accounted service and the authorization server's + directions for interim accounting. If the accounted service is a + one-time event, meaning that the start and stop of the event are + simultaneous, then the Accounting-Record-Type AVP MUST be present and + set to the value EVENT_RECORD. + + If the accounted service is of a measurable length, then the AVP MUST + use the values START_RECORD, STOP_RECORD, and possibly, + INTERIM_RECORD. If the authorization server has not directed interim + accounting to be enabled for the session, two accounting records MUST + be generated for each service of type session. When the initial + + + + + +Calhoun, et al. Standards Track [Page 117] + +RFC 3588 Diameter Based Protocol September 2003 + + + Accounting-Request for a given session is sent, the Accounting- + Record-Type AVP MUST be set to the value START_RECORD. When the last + Accounting-Request is sent, the value MUST be STOP_RECORD. + + If the authorization server has directed interim accounting to be + enabled, the Diameter client MUST produce additional records between + the START_RECORD and STOP_RECORD, marked INTERIM_RECORD. The + production of these records is directed by Acct-Interim-Interval as + well as any re-authentication or re-authorization of the session. The + Diameter client MUST overwrite any previous interim accounting + records that are locally stored for delivery, if a new record is + being generated for the same session. This ensures that only one + pending interim record can exist on an access device for any given + session. + + A particular value of Accounting-Sub-Session-Id MUST appear only in + one sequence of accounting records from a DIAMETER client, except for + the purposes of retransmission. The one sequence that is sent MUST + be either one record with Accounting-Record-Type AVP set to the value + EVENT_RECORD, or several records starting with one having the value + START_RECORD, followed by zero or more INTERIM_RECORD and a single + STOP_RECORD. A particular Diameter application specification MUST + define the type of sequences that MUST be used. + +9.6. Correlation of Accounting Records + + The Diameter protocol's Session-Id AVP, which is globally unique (see + Section 8.8), is used during the authorization phase to identify a + particular session. Services that do not require any authorization + still use the Session-Id AVP to identify sessions. Accounting + messages MAY use a different Session-Id from that sent in + authorization messages. Specific applications MAY require different + a Session-ID for accounting messages. + + However, there are certain applications that require multiple + accounting sub-sessions. Such applications would send messages with + a constant Session-Id AVP, but a different Accounting-Sub-Session-Id + AVP. In these cases, correlation is performed using the Session-Id. + It is important to note that receiving a STOP_RECORD with no + Accounting-Sub-Session-Id AVP when sub-sessions were originally used + in the START_RECORD messages implies that all sub-sessions are + terminated. + + Furthermore, there are certain applications where a user receives + service from different access devices (e.g., Mobile IPv4), each with + their own unique Session-Id. In such cases, the Acct-Multi-Session- + Id AVP is used for correlation. During authorization, a server that + + + + +Calhoun, et al. Standards Track [Page 118] + +RFC 3588 Diameter Based Protocol September 2003 + + + determines that a request is for an existing session SHOULD include + the Acct-Multi-Session-Id AVP, which the access device MUST include + in all subsequent accounting messages. + + The Acct-Multi-Session-Id AVP MAY include the value of the original + Session-Id. It's contents are implementation specific, but MUST be + globally unique across other Acct-Multi-Session-Id, and MUST NOT + change during the life of a session. + + A Diameter application document MUST define the exact concept of a + session that is being accounted, and MAY define the concept of a + multi-session. For instance, the NASREQ DIAMETER application treats + a single PPP connection to a Network Access Server as one session, + and a set of Multilink PPP sessions as one multi-session. + +9.7. Accounting Command-Codes + + This section defines Command-Code values that MUST be supported by + all Diameter implementations that provide Accounting services. + +9.7.1. Accounting-Request + + The Accounting-Request (ACR) command, indicated by the Command-Code + field set to 271 and the Command Flags' 'R' bit set, is sent by a + Diameter node, acting as a client, in order to exchange accounting + information with a peer. + + One of Acct-Application-Id and Vendor-Specific-Application-Id AVPs + MUST be present. If the Vendor-Specific-Application-Id grouped AVP + is present, it must have an Acct-Application-Id inside. + + The AVP listed below SHOULD include service specific accounting AVPs, + as described in Section 9.3. + + + + + + + + + + + + + + + + + + +Calhoun, et al. Standards Track [Page 119] + +RFC 3588 Diameter Based Protocol September 2003 + + + Message Format + + <ACR> ::= < Diameter Header: 271, REQ, PXY > + < Session-Id > + { Origin-Host } + { Origin-Realm } + { Destination-Realm } + { Accounting-Record-Type } + { Accounting-Record-Number } + [ Acct-Application-Id ] + [ Vendor-Specific-Application-Id ] + [ User-Name ] + [ Accounting-Sub-Session-Id ] + [ Acct-Session-Id ] + [ Acct-Multi-Session-Id ] + [ Acct-Interim-Interval ] + [ Accounting-Realtime-Required ] + [ Origin-State-Id ] + [ Event-Timestamp ] + * [ Proxy-Info ] + * [ Route-Record ] + * [ AVP ] + +9.7.2. Accounting-Answer + + The Accounting-Answer (ACA) command, indicated by the Command-Code + field set to 271 and the Command Flags' 'R' bit cleared, is used to + acknowledge an Accounting-Request command. The Accounting-Answer + command contains the same Session-Id and includes the usage AVPs only + if CMS is in use when sending this command. Note that the inclusion + of the usage AVPs when CMS is not being used leads to unnecessarily + large answer messages, and can not be used as a server's proof of the + receipt of these AVPs in an end-to-end fashion. If the Accounting- + Request was protected by end-to-end security, then the corresponding + ACA message MUST be protected by end-to-end security. + + Only the target Diameter Server, known as the home Diameter Server, + SHOULD respond with the Accounting-Answer command. + + One of Acct-Application-Id and Vendor-Specific-Application-Id AVPs + MUST be present. If the Vendor-Specific-Application-Id grouped AVP + is present, it must have an Acct-Application-Id inside. + + The AVP listed below SHOULD include service specific accounting AVPs, + as described in Section 9.3. + + + + + + +Calhoun, et al. Standards Track [Page 120] + +RFC 3588 Diameter Based Protocol September 2003 + + + Message Format + + <ACA> ::= < Diameter Header: 271, PXY > + < Session-Id > + { Result-Code } + { Origin-Host } + { Origin-Realm } + { Accounting-Record-Type } + { Accounting-Record-Number } + [ Acct-Application-Id ] + [ Vendor-Specific-Application-Id ] + [ User-Name ] + [ Accounting-Sub-Session-Id ] + [ Acct-Session-Id ] + [ Acct-Multi-Session-Id ] + [ Error-Reporting-Host ] + [ Acct-Interim-Interval ] + [ Accounting-Realtime-Required ] + [ Origin-State-Id ] + [ Event-Timestamp ] + * [ Proxy-Info ] + * [ AVP ] + +9.8. Accounting AVPs + + This section contains AVPs that describe accounting usage information + related to a specific session. + +9.8.1. Accounting-Record-Type AVP + + The Accounting-Record-Type AVP (AVP Code 480) is of type Enumerated + and contains the type of accounting record being sent. The following + values are currently defined for the Accounting-Record-Type AVP: + + EVENT_RECORD 1 + An Accounting Event Record is used to indicate that a one-time + event has occurred (meaning that the start and end of the event + are simultaneous). This record contains all information relevant + to the service, and is the only record of the service. + + START_RECORD 2 + An Accounting Start, Interim, and Stop Records are used to + indicate that a service of a measurable length has been given. An + Accounting Start Record is used to initiate an accounting session, + and contains accounting information that is relevant to the + initiation of the session. + + + + + +Calhoun, et al. Standards Track [Page 121] + +RFC 3588 Diameter Based Protocol September 2003 + + + INTERIM_RECORD 3 + An Interim Accounting Record contains cumulative accounting + information for an existing accounting session. Interim + Accounting Records SHOULD be sent every time a re-authentication + or re-authorization occurs. Further, additional interim record + triggers MAY be defined by application-specific Diameter + applications. The selection of whether to use INTERIM_RECORD + records is done by the Acct-Interim-Interval AVP. + + STOP_RECORD 4 + An Accounting Stop Record is sent to terminate an accounting + session and contains cumulative accounting information relevant to + the existing session. + +9.8.2. Acct-Interim-Interval + + The Acct-Interim-Interval AVP (AVP Code 85) is of type Unsigned32 and + is sent from the Diameter home authorization server to the Diameter + client. The client uses information in this AVP to decide how and + when to produce accounting records. With different values in this + AVP, service sessions can result in one, two, or two+N accounting + records, based on the needs of the home-organization. The following + accounting record production behavior is directed by the inclusion of + this AVP: + + 1. The omission of the Acct-Interim-Interval AVP or its inclusion + with Value field set to 0 means that EVENT_RECORD, START_RECORD, + and STOP_RECORD are produced, as appropriate for the service. + + 2. The inclusion of the AVP with Value field set to a non-zero value + means that INTERIM_RECORD records MUST be produced between the + START_RECORD and STOP_RECORD records. The Value field of this AVP + is the nominal interval between these records in seconds. The + Diameter node that originates the accounting information, known as + the client, MUST produce the first INTERIM_RECORD record roughly + at the time when this nominal interval has elapsed from the + START_RECORD, the next one again as the interval has elapsed once + more, and so on until the session ends and a STOP_RECORD record is + produced. + + The client MUST ensure that the interim record production times + are randomized so that large accounting message storms are not + created either among records or around a common service start + time. + + + + + + + +Calhoun, et al. Standards Track [Page 122] + +RFC 3588 Diameter Based Protocol September 2003 + + +9.8.3. Accounting-Record-Number AVP + + The Accounting-Record-Number AVP (AVP Code 485) is of type Unsigned32 + and identifies this record within one session. As Session-Id AVPs + are globally unique, the combination of Session-Id and Accounting- + Record-Number AVPs is also globally unique, and can be used in + matching accounting records with confirmations. An easy way to + produce unique numbers is to set the value to 0 for records of type + EVENT_RECORD and START_RECORD, and set the value to 1 for the first + INTERIM_RECORD, 2 for the second, and so on until the value for + STOP_RECORD is one more than for the last INTERIM_RECORD. + +9.8.4. Acct-Session-Id AVP + + The Acct-Session-Id AVP (AVP Code 44) is of type OctetString is only + used when RADIUS/Diameter translation occurs. This AVP contains the + contents of the RADIUS Acct-Session-Id attribute. + +9.8.5. Acct-Multi-Session-Id AVP + + The Acct-Multi-Session-Id AVP (AVP Code 50) is of type UTF8String, + following the format specified in Section 8.8. The Acct-Multi- + Session-Id AVP is used to link together multiple related accounting + sessions, where each session would have a unique Session-Id, but the + same Acct-Multi-Session-Id AVP. This AVP MAY be returned by the + Diameter server in an authorization answer, and MUST be used in all + accounting messages for the given session. + +9.8.6. Accounting-Sub-Session-Id AVP + + The Accounting-Sub-Session-Id AVP (AVP Code 287) is of type + Unsigned64 and contains the accounting sub-session identifier. The + combination of the Session-Id and this AVP MUST be unique per sub- + session, and the value of this AVP MUST be monotonically increased by + one for all new sub-sessions. The absence of this AVP implies no + sub-sessions are in use, with the exception of an Accounting-Request + whose Accounting-Record-Type is set to STOP_RECORD. A STOP_RECORD + message with no Accounting-Sub-Session-Id AVP present will signal the + termination of all sub-sessions for a given Session-Id. + +9.8.7. Accounting-Realtime-Required AVP + + The Accounting-Realtime-Required AVP (AVP Code 483) is of type + Enumerated and is sent from the Diameter home authorization server to + the Diameter client or in the Accounting-Answer from the accounting + server. The client uses information in this AVP to decide what to do + if the sending of accounting records to the accounting server has + been temporarily prevented due to, for instance, a network problem. + + + +Calhoun, et al. Standards Track [Page 123] + +RFC 3588 Diameter Based Protocol September 2003 + + + DELIVER_AND_GRANT 1 + The AVP with Value field set to DELIVER_AND_GRANT means that the + service MUST only be granted as long as there is a connection to + an accounting server. Note that the set of alternative accounting + servers are treated as one server in this sense. Having to move + the accounting record stream to a backup server is not a reason to + discontinue the service to the user. + + GRANT_AND_STORE 2 + The AVP with Value field set to GRANT_AND_STORE means that service + SHOULD be granted if there is a connection, or as long as records + can still be stored as described in Section 9.4. + + This is the default behavior if the AVP isn't included in the + reply from the authorization server. + + GRANT_AND_LOSE 3 + The AVP with Value field set to GRANT_AND_LOSE means that service + SHOULD be granted even if the records can not be delivered or + stored. + +10. AVP Occurrence Table + + The following tables presents the AVPs defined in this document, and + specifies in which Diameter messages they MAY, or MAY NOT be present. + Note that AVPs that can only be present within a Grouped AVP are not + represented in this table. + + The table uses the following symbols: + + 0 The AVP MUST NOT be present in the message. + 0+ Zero or more instances of the AVP MAY be present in the + message. + 0-1 Zero or one instance of the AVP MAY be present in the + message. It is considered an error if there are more than + one instance of the AVP. + 1 One instance of the AVP MUST be present in the message. + 1+ At least one instance of the AVP MUST be present in the + message. + +10.1. Base Protocol Command AVP Table + + The table in this section is limited to the non-accounting Command + Codes defined in this specification. + + + + + + + +Calhoun, et al. Standards Track [Page 124] + +RFC 3588 Diameter Based Protocol September 2003 + + + +-----------------------------------------------+ + | Command-Code | + +---+---+---+---+---+---+---+---+---+---+---+---+ + Attribute Name |CER|CEA|DPR|DPA|DWR|DWA|RAR|RAA|ASR|ASA|STR|STA| + --------------------+---+---+---+---+---+---+---+---+---+---+---+---+ + Acct-Interim- |0 |0 |0 |0 |0 |0 |0-1|0 |0 |0 |0 |0 | + Interval | | | | | | | | | | | | | + Accounting-Realtime-|0 |0 |0 |0 |0 |0 |0-1|0 |0 |0 |0 |0 | + Required | | | | | | | | | | | | | + Acct-Application-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | + Auth-Application-Id |0+ |0+ |0 |0 |0 |0 |1 |0 |1 |0 |1 |0 | + Auth-Grace-Period |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | + Auth-Request-Type |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | + Auth-Session-State |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | + Authorization- |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | + Lifetime | | | | | | | | | | | | | + Class |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0+ |0+ | + Destination-Host |0 |0 |0 |0 |0 |0 |1 |0 |1 |0 |0-1|0 | + Destination-Realm |0 |0 |0 |0 |0 |0 |1 |0 |1 |0 |1 |0 | + Disconnect-Cause |0 |0 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 | + Error-Message |0 |0-1|0 |0-1|0 |0-1|0 |0-1|0 |0-1|0 |0-1| + Error-Reporting-Host|0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1| + Failed-AVP |0 |0+ |0 |0+ |0 |0+ |0 |0+ |0 |0+ |0 |0+ | + Firmware-Revision |0-1|0-1|0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | + Host-IP-Address |1+ |1+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | + Inband-Security-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | + Multi-Round-Time-Out|0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | + Origin-Host |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 | + Origin-Realm |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 | + Origin-State-Id |0-1|0-1|0 |0 |0-1|0-1|0-1|0-1|0-1|0-1|0-1|0-1| + Product-Name |1 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | + Proxy-Info |0 |0 |0 |0 |0 |0 |0+ |0+ |0+ |0+ |0+ |0+ | + Redirect-Host |0 |0 |0 |0 |0 |0 |0 |0+ |0 |0+ |0 |0+ | + Redirect-Host-Usage |0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1| + Redirect-Max-Cache- |0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1| + Time | | | | | | | | | | | | | + Result-Code |0 |1 |0 |1 |0 |1 |0 |1 |0 |0 |0 |1 | + Re-Auth-Request-Type|0 |0 |0 |0 |0 |0 |1 |0 |0 |0 |0 |0 | + Route-Record |0 |0 |0 |0 |0 |0 |0+ |0 |0+ |0 |0+ |0 | + Session-Binding |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | + Session-Id |0 |0 |0 |0 |0 |0 |1 |1 |1 |1 |1 |1 | + Session-Server- |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | + Failover | | | | | | | | | | | | | + Session-Timeout |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | + Supported-Vendor-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | + Termination-Cause |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |1 |0 | + User-Name |0 |0 |0 |0 |0 |0 |0-1|0-1|0-1|0-1|0-1|0-1| + Vendor-Id |1 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | + + + +Calhoun, et al. Standards Track [Page 125] + +RFC 3588 Diameter Based Protocol September 2003 + + + Vendor-Specific- |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | + Application-Id | | | | | | | | | | | | | + --------------------+---+---+---+---+---+---+---+---+---+---+---+---+ + +10.2. Accounting AVP Table + + The table in this section is used to represent which AVPs defined in + this document are to be present in the Accounting messages. These + AVP occurrence requirements are guidelines, which may be expanded, + and/or overridden by application-specific requirements in the + Diameter applications documents. + + +-----------+ + | Command | + | Code | + +-----+-----+ + Attribute Name | ACR | ACA | + ------------------------------+-----+-----+ + Acct-Interim-Interval | 0-1 | 0-1 | + Acct-Multi-Session-Id | 0-1 | 0-1 | + Accounting-Record-Number | 1 | 1 | + Accounting-Record-Type | 1 | 1 | + Acct-Session-Id | 0-1 | 0-1 | + Accounting-Sub-Session-Id | 0-1 | 0-1 | + Accounting-Realtime-Required | 0-1 | 0-1 | + Acct-Application-Id | 0-1 | 0-1 | + Auth-Application-Id | 0 | 0 | + Class | 0+ | 0+ | + Destination-Host | 0-1 | 0 | + Destination-Realm | 1 | 0 | + Error-Reporting-Host | 0 | 0+ | + Event-Timestamp | 0-1 | 0-1 | + Origin-Host | 1 | 1 | + Origin-Realm | 1 | 1 | + Proxy-Info | 0+ | 0+ | + Route-Record | 0+ | 0+ | + Result-Code | 0 | 1 | + Session-Id | 1 | 1 | + Termination-Cause | 0-1 | 0-1 | + User-Name | 0-1 | 0-1 | + Vendor-Specific-Application-Id| 0-1 | 0-1 | + ------------------------------+-----+-----+ + + + + + + + + + +Calhoun, et al. Standards Track [Page 126] + +RFC 3588 Diameter Based Protocol September 2003 + + +11. IANA Considerations + + This section provides guidance to the Internet Assigned Numbers + Authority (IANA) regarding registration of values related to the + Diameter protocol, in accordance with BCP 26 [IANA]. The following + policies are used here with the meanings defined in BCP 26: "Private + Use", "First Come First Served", "Expert Review", "Specification + Required", "IETF Consensus", "Standards Action". + + This section explains the criteria to be used by the IANA for + assignment of numbers within namespaces defined within this document. + + Diameter is not intended as a general purpose protocol, and + allocations SHOULD NOT be made for purposes unrelated to + authentication, authorization or accounting. + + For registration requests where a Designated Expert should be + consulted, the responsible IESG area director should appoint the + Designated Expert. For Designated Expert with Specification + Required, the request is posted to the AAA WG mailing list (or, if it + has been disbanded, a successor designated by the Area Director) for + comment and review, and MUST include a pointer to a public + specification. Before a period of 30 days has passed, the Designated + Expert will either approve or deny the registration request and + publish a notice of the decision to the AAA WG mailing list or its + successor. A denial notice must be justified by an explanation and, + in the cases where it is possible, concrete suggestions on how the + request can be modified so as to become acceptable. + +11.1. AVP Header + + As defined in Section 4, the AVP header contains three fields that + requires IANA namespace management; the AVP Code, Vendor-ID and Flags + field. + +11.1.1. AVP Codes + + The AVP Code namespace is used to identify attributes. There are + multiple namespaces. Vendors can have their own AVP Codes namespace + which will be identified by their Vendor-ID (also known as + Enterprise-Number) and they control the assignments of their vendor- + specific AVP codes within their own namespace. The absence of a + Vendor-ID or a Vendor-ID value of zero (0) identifies the IETF IANA + controlled AVP Codes namespace. The AVP Codes and sometimes also + possible values in an AVP are controlled and maintained by IANA. + + + + + + +Calhoun, et al. Standards Track [Page 127] + +RFC 3588 Diameter Based Protocol September 2003 + + + AVP Code 0 is not used. AVP Codes 1-255 are managed separately as + RADIUS Attribute Types [RADTYPE]. This document defines the AVP + Codes 257-274, 276-285, 287, 291-300, 480, 483 and 485-486. See + Section 4.5 for the assignment of the namespace in this + specification. + + AVPs may be allocated following Designated Expert with Specification + Required [IANA]. Release of blocks of AVPs (more than 3 at a time + for a given purpose) should require IETF Consensus. + + Note that Diameter defines a mechanism for Vendor-Specific AVPs, + where the Vendor-Id field in the AVP header is set to a non-zero + value. Vendor-Specific AVPs codes are for Private Use and should be + encouraged instead of allocation of global attribute types, for + functions specific only to one vendor's implementation of Diameter, + where no interoperability is deemed useful. Where a Vendor-Specific + AVP is implemented by more than one vendor, allocation of global AVPs + should be encouraged instead. + +11.1.2. AVP Flags + + There are 8 bits in the AVP Flags field of the AVP header, defined in + Section 4. This document assigns bit 0 ('V'endor Specific), bit 1 + ('M'andatory) and bit 2 ('P'rotected). The remaining bits should + only be assigned via a Standards Action [IANA]. + +11.2. Diameter Header + + As defined in Section 3, the Diameter header contains two fields that + require IANA namespace management; Command Code and Command Flags. + +11.2.1. Command Codes + + The Command Code namespace is used to identify Diameter commands. + The values 0-255 are reserved for RADIUS backward compatibility, and + are defined as "RADIUS Packet Type Codes" in [RADTYPE]. Values 256- + 16,777,213 are for permanent, standard commands, allocated by IETF + Consensus [IANA]. This document defines the Command Codes 257, 258, + 271, 274-275, 280 and 282. See Section 3.1 for the assignment of the + namespace in this specification. + + The values 16,777,214 and 16,777,215 (hexadecimal values 0xfffffe - + 0xffffff) are reserved for experimental commands. As these codes are + only for experimental and testing purposes, no guarantee is made for + interoperability between Diameter peers using experimental commands, + as outlined in [IANA-EXP]. + + + + + +Calhoun, et al. Standards Track [Page 128] + +RFC 3588 Diameter Based Protocol September 2003 + + +11.2.2. Command Flags + + There are eight bits in the Command Flags field of the Diameter + header. This document assigns bit 0 ('R'equest), bit 1 ('P'roxy), + bit 2 ('E'rror) and bit 3 ('T'). Bits 4 through 7 MUST only be + assigned via a Standards Action [IANA]. + +11.3. Application Identifiers + + As defined in Section 2.4, the Application Identifier is used to + identify a specific Diameter Application. There are standards-track + application ids and vendor specific application ids. + + IANA [IANA] has assigned the range 0x00000001 to 0x00ffffff for + standards-track applications; and 0x01000000 - 0xfffffffe for vendor + specific applications, on a first-come, first-served basis. The + following values are allocated. + + Diameter Common Messages 0 + NASREQ 1 [NASREQ] + Mobile-IP 2 [DIAMMIP] + Diameter Base Accounting 3 + Relay 0xffffffff + + Assignment of standards-track application IDs are by Designated + Expert with Specification Required [IANA]. + + Both Application-Id and Acct-Application-Id AVPs use the same + Application Identifier space. + + Vendor-Specific Application Identifiers, are for Private Use. + Vendor-Specific Application Identifiers are assigned on a First Come, + First Served basis by IANA. + +11.4. AVP Values + + Certain AVPs in Diameter define a list of values with various + meanings. For attributes other than those specified in this section, + adding additional values to the list can be done on a First Come, + First Served basis by IANA. + +11.4.1. Result-Code AVP Values + + As defined in Section 7.1, the Result-Code AVP (AVP Code 268) defines + the values 1001, 2001-2002, 3001-3010, 4001-4002 and 5001-5017. + + All remaining values are available for assignment via IETF Consensus + [IANA]. + + + +Calhoun, et al. Standards Track [Page 129] + +RFC 3588 Diameter Based Protocol September 2003 + + +11.4.2. Accounting-Record-Type AVP Values + + As defined in Section 9.8.1, the Accounting-Record-Type AVP (AVP Code + 480) defines the values 1-4. All remaining values are available for + assignment via IETF Consensus [IANA]. + +11.4.3. Termination-Cause AVP Values + + As defined in Section 8.15, the Termination-Cause AVP (AVP Code 295) + defines the values 1-8. All remaining values are available for + assignment via IETF Consensus [IANA]. + +11.4.4. Redirect-Host-Usage AVP Values + + As defined in Section 6.13, the Redirect-Host-Usage AVP (AVP Code + 261) defines the values 0-5. All remaining values are available for + assignment via IETF Consensus [IANA]. + +11.4.5. Session-Server-Failover AVP Values + + As defined in Section 8.18, the Session-Server-Failover AVP (AVP Code + 271) defines the values 0-3. All remaining values are available for + assignment via IETF Consensus [IANA]. + +11.4.6. Session-Binding AVP Values + + As defined in Section 8.17, the Session-Binding AVP (AVP Code 270) + defines the bits 1-4. All remaining bits are available for + assignment via IETF Consensus [IANA]. + +11.4.7. Disconnect-Cause AVP Values + + As defined in Section 5.4.3, the Disconnect-Cause AVP (AVP Code 273) + defines the values 0-2. All remaining values are available for + assignment via IETF Consensus [IANA]. + +11.4.8. Auth-Request-Type AVP Values + + As defined in Section 8.7, the Auth-Request-Type AVP (AVP Code 274) + defines the values 1-3. All remaining values are available for + assignment via IETF Consensus [IANA]. + +11.4.9. Auth-Session-State AVP Values + + As defined in Section 8.11, the Auth-Session-State AVP (AVP Code 277) + defines the values 0-1. All remaining values are available for + assignment via IETF Consensus [IANA]. + + + + +Calhoun, et al. Standards Track [Page 130] + +RFC 3588 Diameter Based Protocol September 2003 + + +11.4.10. Re-Auth-Request-Type AVP Values + + As defined in Section 8.12, the Re-Auth-Request-Type AVP (AVP Code + 285) defines the values 0-1. All remaining values are available for + assignment via IETF Consensus [IANA]. + +11.4.11. Accounting-Realtime-Required AVP Values + + As defined in Section 9.8.7, the Accounting-Realtime-Required AVP + (AVP Code 483) defines the values 1-3. All remaining values are + available for assignment via IETF Consensus [IANA]. + +11.4.12. Inband-Security-Id AVP (code 299) + + As defined in Section 6.10, the Inband-Security-Id AVP (AVP Code 299) + defines the values 0-1. All remaining values are available for + assignment via IETF Consensus [IANA]. + +11.5. Diameter TCP/SCTP Port Numbers + + The IANA has assigned TCP and SCTP port number 3868 to Diameter. + +11.6. NAPTR Service Fields + + The registration in the RFC MUST include the following information: + + Service Field: The service field being registered. An example for a + new fictitious transport protocol called NCTP might be "AAA+D2N". + + Protocol: The specific transport protocol associated with that + service field. This MUST include the name and acronym for the + protocol, along with reference to a document that describes the + transport protocol. For example - "New Connectionless Transport + Protocol (NCTP), RFC 5766". + + Name and Contact Information: The name, address, email address and + telephone number for the person performing the registration. + + The following values have been placed into the registry: + + Services Field Protocol + AAA+D2T TCP + AAA+D2S SCTP + +12. Diameter protocol related configurable parameters + + This section contains the configurable parameters that are found + throughout this document: + + + +Calhoun, et al. Standards Track [Page 131] + +RFC 3588 Diameter Based Protocol September 2003 + + + Diameter Peer + A Diameter entity MAY communicate with peers that are statically + configured. A statically configured Diameter peer would require + that either the IP address or the fully qualified domain name + (FQDN) be supplied, which would then be used to resolve through + DNS. + + Realm Routing Table + A Diameter proxy server routes messages based on the realm portion + of a Network Access Identifier (NAI). The server MUST have a + table of Realm Names, and the address of the peer to which the + message must be forwarded to. The routing table MAY also include + a "default route", which is typically used for all messages that + cannot be locally processed. + + Tc timer + The Tc timer controls the frequency that transport connection + attempts are done to a peer with whom no active transport + connection exists. The recommended value is 30 seconds. + +13. Security Considerations + + The Diameter base protocol assumes that messages are secured by using + either IPSec or TLS. This security mechanism is acceptable in + environments where there is no untrusted third party agent. In other + situations, end-to-end security is needed. + + Diameter clients, such as Network Access Servers (NASes) and Mobility + Agents MUST support IP Security [SECARCH] and MAY support TLS [TLS]. + Diameter servers MUST support TLS and IPsec. Diameter + implementations MUST use transmission-level security of some kind + (IPsec or TLS) on each connection. + + If a Diameter connection is not protected by IPsec, then the CER/CEA + exchange MUST include an Inband-Security-ID AVP with a value of TLS. + For TLS usage, a TLS handshake will begin when both ends are in the + open state, after completion of the CER/CEA exchange. If the TLS + handshake is successful, all further messages will be sent via TLS. + If the handshake fails, both ends move to the closed state. + + It is suggested that IPsec be used primarily at the edges for intra- + domain exchanges. For NAS devices without certificate support, pre- + shared keys can be used between the NAS and a local AAA proxy. + + For protection of inter-domain exchanges, TLS is recommended. See + Sections 13.1 and 13.2 for more details on IPsec and TLS usage. + + + + + +Calhoun, et al. Standards Track [Page 132] + +RFC 3588 Diameter Based Protocol September 2003 + + +13.1. IPsec Usage + + All Diameter implementations MUST support IPsec ESP [IPsec] in + transport mode with non-null encryption and authentication algorithms + to provide per-packet authentication, integrity protection and + confidentiality, and MUST support the replay protection mechanisms of + IPsec. + + Diameter implementations MUST support IKE for peer authentication, + negotiation of security associations, and key management, using the + IPsec DOI [IPSECDOI]. Diameter implementations MUST support peer + authentication using a pre-shared key, and MAY support certificate- + based peer authentication using digital signatures. Peer + authentication using the public key encryption methods outlined in + IKE's Sections 5.2 and 5.3 [IKE] SHOULD NOT be used. + + Conformant implementations MUST support both IKE Main Mode and + Aggressive Mode. When pre-shared keys are used for authentication, + IKE Aggressive Mode SHOULD be used, and IKE Main Mode SHOULD NOT be + used. When digital signatures are used for authentication, either + IKE Main Mode or IKE Aggressive Mode MAY be used. + + When digital signatures are used to achieve authentication, an IKE + negotiator SHOULD use IKE Certificate Request Payload(s) to specify + the certificate authority (or authorities) that are trusted in + accordance with its local policy. IKE negotiators SHOULD use + pertinent certificate revocation checks before accepting a PKI + certificate for use in IKE's authentication procedures. + + The Phase 2 Quick Mode exchanges used to negotiate protection for + Diameter connections MUST explicitly carry the Identity Payload + fields (IDci and IDcr). The DOI provides for several types of + identification data. However, when used in conformant + implementations, each ID Payload MUST carry a single IP address and a + single non-zero port number, and MUST NOT use the IP Subnet or IP + Address Range formats. This allows the Phase 2 security association + to correspond to specific TCP and SCTP connections. + + Since IPsec acceleration hardware may only be able to handle a + limited number of active IKE Phase 2 SAs, Phase 2 delete messages may + be sent for idle SAs, as a means of keeping the number of active + Phase 2 SAs to a minimum. The receipt of an IKE Phase 2 delete + message SHOULD NOT be interpreted as a reason for tearing down a + Diameter connection. Rather, it is preferable to leave the + connection up, and if additional traffic is sent on it, to bring up + another IKE Phase 2 SA to protect it. This avoids the potential for + continually bringing connections up and down. + + + + +Calhoun, et al. Standards Track [Page 133] + +RFC 3588 Diameter Based Protocol September 2003 + + +13.2. TLS Usage + + A Diameter node that initiates a connection to another Diameter node + acts as a TLS client according to [TLS], and a Diameter node that + accepts a connection acts as a TLS server. Diameter nodes + implementing TLS for security MUST mutually authenticate as part of + TLS session establishment. In order to ensure mutual authentication, + the Diameter node acting as TLS server must request a certificate + from the Diameter node acting as TLS client, and the Diameter node + acting as TLS client MUST be prepared to supply a certificate on + request. + + Diameter nodes MUST be able to negotiate the following TLS cipher + suites: + + TLS_RSA_WITH_RC4_128_MD5 + TLS_RSA_WITH_RC4_128_SHA + TLS_RSA_WITH_3DES_EDE_CBC_SHA + + Diameter nodes SHOULD be able to negotiate the following TLS cipher + suite: + + TLS_RSA_WITH_AES_128_CBC_SHA + + Diameter nodes MAY negotiate other TLS cipher suites. + +13.3. Peer-to-Peer Considerations + + As with any peer-to-peer protocol, proper configuration of the trust + model within a Diameter peer is essential to security. When + certificates are used, it is necessary to configure the root + certificate authorities trusted by the Diameter peer. These root CAs + are likely to be unique to Diameter usage and distinct from the root + CAs that might be trusted for other purposes such as Web browsing. + In general, it is expected that those root CAs will be configured so + as to reflect the business relationships between the organization + hosting the Diameter peer and other organizations. As a result, a + Diameter peer will typically not be configured to allow connectivity + with any arbitrary peer. When certificate authentication Diameter + peers may not be known beforehand, and therefore peer discovery may + be required. + + Note that IPsec is considerably less flexible than TLS when it comes + to configuring root CAs. Since use of Port identifiers is prohibited + within IKE Phase 1, within IPsec it is not possible to uniquely + configure trusted root CAs for each application individually; the + same policy must be used for all applications. This implies, for + example, that a root CA trusted for use with Diameter must also be + + + +Calhoun, et al. Standards Track [Page 134] + +RFC 3588 Diameter Based Protocol September 2003 + + + trusted to protect SNMP. These restrictions can be awkward at best. + Since TLS supports application-level granularity in certificate + policy, TLS SHOULD be used to protect Diameter connections between + administrative domains. IPsec is most appropriate for intra-domain + usage when pre-shared keys are used as a security mechanism. + + When pre-shared key authentication is used with IPsec to protect + Diameter, unique pre-shared keys are configured with Diameter peers, + who are identified by their IP address (Main Mode), or possibly their + FQDN (Aggressive Mode). As a result, it is necessary for the set of + Diameter peers to be known beforehand. Therefore, peer discovery is + typically not necessary. + + The following is intended to provide some guidance on the issue. + + It is recommended that a Diameter peer implement the same security + mechanism (IPsec or TLS) across all its peer-to-peer connections. + Inconsistent use of security mechanisms can result in redundant + security mechanisms being used (e.g., TLS over IPsec) or worse, + potential security vulnerabilities. When IPsec is used with + Diameter, a typical security policy for outbound traffic is "Initiate + IPsec, from me to any, destination port Diameter"; for inbound + traffic, the policy would be "Require IPsec, from any to me, + destination port Diameter". + + This policy causes IPsec to be used whenever a Diameter peer + initiates a connection to another Diameter peer, and to be required + whenever an inbound Diameter connection occurs. This policy is + attractive, since it does not require policy to be set for each peer + or dynamically modified each time a new Diameter connection is + created; an IPsec SA is automatically created based on a simple + static policy. Since IPsec extensions are typically not available to + the sockets API on most platforms, and IPsec policy functionality is + implementation dependent, use of a simple static policy is the often + the simplest route to IPsec-enabling a Diameter implementation. + + One implication of the recommended policy is that if a node is using + both TLS and IPsec, there is not a convenient way in which to use + either TLS or IPsec, but not both, without reserving an additional + port for TLS usage. Since Diameter uses the same port for TLS and + non-TLS usage, where the recommended IPsec policy is put in place, a + TLS-protected connection will match the IPsec policy, and both IPsec + and TLS will be used to protect the Diameter connection. To avoid + this, it would be necessary to plumb peer-specific policies either + statically or dynamically. + + + + + + +Calhoun, et al. Standards Track [Page 135] + +RFC 3588 Diameter Based Protocol September 2003 + + + If IPsec is used to secure Diameter peer-to-peer connections, IPsec + policy SHOULD be set so as to require IPsec protection for inbound + connections, and to initiate IPsec protection for outbound + connections. This can be accomplished via use of inbound and + outbound filter policy. + +14. References + +14.1. Normative References + + [AAATRANS] Aboba, B. and J. Wood, "Authentication, Authorization + and Accounting (AAA) Transport Profile", RFC 3539, + June 2003. + + [ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax + Specifications: ABNF", RFC 2234, November 1997. + + [ASSIGNNO] Reynolds, J., "Assigned Numbers: RFC 1700 is Replaced + by an On-line Database", RFC 3232, January 2002. + + [DIFFSERV] Nichols, K., Blake, S., Baker, F. and D. Black, + "Definition of the Differentiated Services Field (DS + Field) in the IPv4 and IPv6 Headers", RFC 2474, + December 1998. + + [DIFFSERVAF] Heinanen, J., Baker, F., Weiss, W. and J. Wroclawski, + "Assured Forwarding PHB Group", RFC 2597, June 1999. + + [DIFFSERVEF] Davie, B., Charny, A., Bennet, J., Benson, K., Le + Boudec, J., Courtney, W., Davari, S., Firoiu, V. and + D. Stiliadis, "An Expedited Forwarding PHB", RFC 3246, + March 2002. + + [DNSSRV] Gulbrandsen, A., Vixie, P. and L. Esibov, "A DNS RR + for specifying the location of services (DNS SRV)", + RFC 2782, February 2000. + + [EAP] Blunk, L. and J. Vollbrecht, "PPP Extensible + Authentication Protocol (EAP)", RFC 2284, March 1998. + + [FLOATPOINT] Institute of Electrical and Electronics Engineers, + "IEEE Standard for Binary Floating-Point Arithmetic", + ANSI/IEEE Standard 754-1985, August 1985. + + [IANA] Narten, T. and H. Alvestrand, "Guidelines for Writing + an IANA Considerations Section in RFCs", BCP 26, RFC + 2434, October 1998. + + + + +Calhoun, et al. Standards Track [Page 136] + +RFC 3588 Diameter Based Protocol September 2003 + + + [IANAADFAM] IANA; "Address Family Numbers", + http://www.iana.org/assignments/address-family-numbers + + [IANAWEB] IANA, "Number assignment", http://www.iana.org + + [IKE] Harkins, D. and D. Carrel, "The Internet Key Exchange + (IKE)", RFC 2409, November 1998. + + [IPComp] Shacham, A., Monsour, R., Pereira, R. and M. Thomas, + "IP Payload Compression Protocol (IPComp)", RFC 3173, + September 2001. + + [IPSECDOI] Piper, D., "The Internet IP Security Domain of + Interpretation for ISAKMP", RFC 2407, November 1998. + + [IPV4] Postel, J., "Internet Protocol", STD 5, RFC 791, + September 1981. + + [IPV6] Hinden, R. and S. Deering, "IP Version 6 Addressing + Architecture", RFC 2373, July 1998. + + [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate + Requirement Levels", BCP 14, RFC 2119, March 1997. + + [NAI] Aboba, B. and M. Beadles, "The Network Access + Identifier", RFC 2486, January 1999. + + [NAPTR] Mealling, M. and R. Daniel, "The naming authority + pointer (NAPTR) DNS resource record," RFC 2915, + September 2000. + + [RADTYPE] IANA, "RADIUS Types", + http://www.iana.org/assignments/radius-types + + [SCTP] Stewart, R., Xie, Q., Morneault, K., Sharp, C., + Schwarzbauer, H., Taylor, T., Rytina, I., Kalla, M., + Zhang, L. and V. Paxson, "Stream Control Transmission + Protocol", RFC 2960, October 2000. + + [SLP] Veizades, J., Guttman, E., Perkins, C. and M. Day, + "Service Location Protocol, Version 2", RFC 2165, June + 1999. + + [SNTP] Mills, D., "Simple Network Time Protocol (SNTP) + Version 4 for IPv4, IPv6 and OSI", RFC 2030, October + 1996. + + + + + +Calhoun, et al. Standards Track [Page 137] + +RFC 3588 Diameter Based Protocol September 2003 + + + [TCP] Postel, J. "Transmission Control Protocol", STD 7, RFC + 793, January 1981. + + [TEMPLATE] Guttman, E., Perkins, C. and J. Kempf, "Service + Templates and Service: Schemes", RFC 2609, June 1999. + + [TLS] Dierks, T. and C. Allen, "The TLS Protocol Version + 1.0", RFC 2246, January 1999. + + [TLSSCTP] Jungmaier, A., Rescorla, E. and M. Tuexen, "Transport + Layer Security over Stream Control Transmission + Protocol", RFC 3436, December 2002. + + [URI] Berners-Lee, T., Fielding, R. and L. Masinter, + "Uniform Resource Identifiers (URI): Generic Syntax", + RFC 2396, August 1998. + + [UTF8] Yergeau, F., "UTF-8, a transformation format of ISO + 10646", RFC 2279, January 1998. + +14.2. Informative References + + [AAACMS] P. Calhoun, W. Bulley, S. Farrell, "Diameter CMS + Security Application", Work in Progress. + + [AAAREQ] Aboba, B., Calhoun, P., Glass, S., Hiller, T., McCann, + P., Shiino, H., Zorn, G., Dommety, G., Perkins, C., + Patil, B., Mitton, D., Manning, S., Beadles, M., + Walsh, P., Chen, X., Sivalingham, S., Hameed, A., + Munson, M., Jacobs, S., Lim, B., Hirschman, B., Hsu, + R., Xu, Y., Campbell, E., Baba, S. and E. Jaques, + "Criteria for Evaluating AAA Protocols for Network + Access", RFC 2989, November 2000. + + [ACCMGMT] Aboba, B., Arkko, J. and D. Harrington. "Introduction + to Accounting Management", RFC 2975, October 2000. + + [CDMA2000] Hiller, T., Walsh, P., Chen, X., Munson, M., Dommety, + G., Sivalingham, S., Lim, B., McCann, P., Shiino, H., + Hirschman, B., Manning, S., Hsu, R., Koo, H., Lipford, + M., Calhoun, P., Lo, C., Jaques, E., Campbell, E., Xu, + Y., Baba, S., Ayaki, T., Seki, T. and A. Hameed, + "CDMA2000 Wireless Data Requirements for AAA", RFC + 3141, June 2001. + + [DIAMMIP] P. Calhoun, C. Perkins, "Diameter Mobile IP + Application", Work in Progress. + + + + +Calhoun, et al. Standards Track [Page 138] + +RFC 3588 Diameter Based Protocol September 2003 + + + [DYNAUTH] Chiba, M., Dommety, G., Eklund, M., Mitton, D. and B. + Aboba, "Dynamic Authorization Extensions to Remote + Authentication Dial In User Service (RADIUS)", RFC + 3576, July 2003. + + [IANA-EXP] T. Narten, "Assigning Experimental and Testing Numbers + Considered Useful", Work in Progress. + + [MIPV4] Perkins, C., "IP Mobility Support for IPv4", RFC 3344, + August 2002. + + [MIPREQ] Glass, S., Hiller, T., Jacobs, S. and C. Perkins, + "Mobile IP Authentication, Authorization, and + Accounting Requirements", RFC 2977, October 2000. + + [NASNG] Mitton, D. and M. Beadles, "Network Access Server + Requirements Next Generation (NASREQNG) NAS Model", + RFC 2881, July 2000. + + [NASREQ] P. Calhoun, W. Bulley, A. Rubens, J. Haag, "Diameter + NASREQ Application", Work in Progress. + + [NASCRIT] Beadles, M. and D. Mitton, "Criteria for Evaluating + Network Access Server Protocols", RFC 3169, September + 2001. + + [PPP] Simpson, W., "The Point-to-Point Protocol (PPP)", STD + 51, RFC 1661, July 1994. + + [PROXYCHAIN] Aboba, B. and J. Vollbrecht, "Proxy Chaining and + Policy Implementation in Roaming", RFC 2607, June + 1999. + + [RADACCT] Rigney, C., "RADIUS Accounting", RFC 2866, June 2000. + + [RADEXT] Rigney, C., Willats, W. and P. Calhoun, "RADIUS + Extensions", RFC 2869, June 2000. + + [RADIUS] Rigney, C., Willens, S., Rubens, A. and W. Simpson, + "Remote Authentication Dial In User Service (RADIUS)", + RFC 2865, June 2000. + + [ROAMREV] Aboba, B., Lu, J., Alsop, J., Ding, J. and W. Wang, + "Review of Roaming Implementations", RFC 2194, + September 1997. + + [ROAMCRIT] Aboba, B. and G. Zorn, "Criteria for Evaluating + Roaming Protocols", RFC 2477, January 1999. + + + +Calhoun, et al. Standards Track [Page 139] + +RFC 3588 Diameter Based Protocol September 2003 + + + [SECARCH] Kent, S. and R. Atkinson, "Security Architecture for + the Internet Protocol", RFC 2401, November 1998. + + [TACACS] Finseth, C., "An Access Control Protocol, Sometimes + Called TACACS", RFC 1492, July 1993. + +15. Acknowledgements + + The authors would like to thank Nenad Trifunovic, Tony Johansson and + Pankaj Patel for their participation in the pre-IETF Document Reading + Party. Allison Mankin, Jonathan Wood and Bernard Aboba provided + invaluable assistance in working out transport issues, and similarly + with Steven Bellovin in the security area. + + Paul Funk and David Mitton were instrumental in getting the Peer + State Machine correct, and our deep thanks go to them for their time. + + Text in this document was also provided by Paul Funk, Mark Eklund, + Mark Jones and Dave Spence. Jacques Caron provided many great + comments as a result of a thorough review of the spec. + + The authors would also like to acknowledge the following people for + their contribution in the development of the Diameter protocol: + + Allan C. Rubens, Haseeb Akhtar, William Bulley, Stephen Farrell, + David Frascone, Daniel C. Fox, Lol Grant, Ignacio Goyret, Nancy + Greene, Peter Heitman, Fredrik Johansson, Mark Jones, Martin Julien, + Bob Kopacz, Paul Krumviede, Fergal Ladley, Ryan Moats, Victor Muslin, + Kenneth Peirce, John Schnizlein, Sumit Vakil, John R. Vollbrecht and + Jeff Weisberg. + + Finally, Pat Calhoun would like to thank Sun Microsystems since most + of the effort put into this document was done while he was in their + employ. + + + + + + + + + + + + + + + + + +Calhoun, et al. Standards Track [Page 140] + +RFC 3588 Diameter Based Protocol September 2003 + + +Appendix A. Diameter Service Template + + The following service template describes the attributes used by + Diameter servers to advertise themselves. This simplifies the + process of selecting an appropriate server to communicate with. A + Diameter client can request specific Diameter servers based on + characteristics of the Diameter service desired (for example, an AAA + server to use for accounting.) + + Name of submitter: "Erik Guttman" <Erik.Guttman@sun.com> Language of + service template: en + + Security Considerations: + Diameter clients and servers use various cryptographic mechanisms + to protect communication integrity, confidentiality as well as + perform end-point authentication. It would thus be difficult if + not impossible for an attacker to advertise itself using SLPv2 and + pose as a legitimate Diameter peer without proper preconfigured + secrets or cryptographic keys. Still, as Diameter services are + vital for network operation it is important to use SLPv2 + authentication to prevent an attacker from modifying or + eliminating service advertisements for legitimate Diameter + servers. + + Template text: + -------------------------template begins here----------------------- + template-type=service:diameter + + template-version=0.0 + + template-description= + The Diameter protocol is defined by RFC 3588. + + template-url-syntax= + url-path= ; The Diameter URL format is described in Section 2.9. + ; Example: 'aaa://aaa.example.com:1812;transport=tcp + supported-auth-applications= string L M + # This attribute lists the Diameter applications supported by the + # AAA implementation. The applications currently defined are: + # Application Name Defined by + # ---------------- ----------------------------------- + # NASREQ Diameter Network Access Server Application + # MobileIP Diameter Mobile IP Application + # + # Notes: + # . Diameter implementations support one or more applications. + # . Additional applications may be defined in the future. + # An updated service template will be created at that time. + + + +Calhoun, et al. Standards Track [Page 141] + +RFC 3588 Diameter Based Protocol September 2003 + + + # + NASREQ,MobileIP + + supported-acct-applications= string L M + # This attribute lists the Diameter applications supported by the + # AAA implementation. The applications currently defined are: + # Application Name Defined by + # ---------------- ----------------------------------- + # NASREQ Diameter Network Access Server Application + # MobileIP Diameter Mobile IP Application + # + # Notes: + # . Diameter implementations support one or more applications. + # . Additional applications may be defined in the future. + # An updated service template will be created at that time. + # + NASREQ,MobileIP + + supported-transports= string L M + SCTP + # This attribute lists the supported transports that the Diameter + # implementation accepts. Note that a compliant Diameter + # implementation MUST support SCTP, though it MAY support other + # transports, too. + SCTP,TCP + + -------------------------template ends here----------------------- + +Appendix B. NAPTR Example + + As an example, consider a client that wishes to resolve aaa:ex.com. + The client performs a NAPTR query for that domain, and the following + NAPTR records are returned: + + ;; order pref flags service regexp replacement + IN NAPTR 50 50 "s" "AAA+D2S" "" + _diameter._sctp.example.com IN NAPTR 100 50 "s" "AAA+D2T" + "" _aaa._tcp.example.com + + This indicates that the server supports SCTP, and TCP, in that order. + If the client supports over SCTP, SCTP will be used, targeted to a + host determined by an SRV lookup of _diameter._sctp.ex.com. That + lookup would return: + + ;; Priority Weight Port Target + IN SRV 0 1 5060 server1.example.com IN SRV 0 + 2 5060 server2.example.com + + + + +Calhoun, et al. Standards Track [Page 142] + +RFC 3588 Diameter Based Protocol September 2003 + + +Appendix C. Duplicate Detection + + As described in Section 9.4, accounting record duplicate detection is + based on session identifiers. Duplicates can appear for various + reasons: + + - Failover to an alternate server. Where close to real-time + performance is required, failover thresholds need to be kept low + and this may lead to an increased likelihood of duplicates. + Failover can occur at the client or within Diameter agents. + + - Failure of a client or agent after sending of a record from non- + volatile memory, but prior to receipt of an application layer ACK + and deletion of the record. record to be sent. This will result + in retransmission of the record soon after the client or agent has + rebooted. + + - Duplicates received from RADIUS gateways. Since the + retransmission behavior of RADIUS is not defined within [RFC2865], + the likelihood of duplication will vary according to the + implementation. + + - Implementation problems and misconfiguration. + + The T flag is used as an indication of an application layer + retransmission event, e.g., due to failover to an alternate server. + It is defined only for request messages sent by Diameter clients or + agents. For instance, after a reboot, a client may not know whether + it has already tried to send the accounting records in its non- + volatile memory before the reboot occurred. Diameter servers MAY use + the T flag as an aid when processing requests and detecting duplicate + messages. However, servers that do this MUST ensure that duplicates + are found even when the first transmitted request arrives at the + server after the retransmitted request. It can be used only in cases + where no answer has been received from the Server for a request and + the request is sent again, (e.g., due to a failover to an alternate + peer, due to a recovered primary peer or due to a client re-sending a + stored record from non-volatile memory such as after reboot of a + client or agent). + + In some cases the Diameter accounting server can delay the duplicate + detection and accounting record processing until a post-processing + phase takes place. At that time records are likely to be sorted + according to the included User-Name and duplicate elimination is easy + in this case. In other situations it may be necessary to perform + real-time duplicate detection, such as when credit limits are imposed + or real-time fraud detection is desired. + + + + +Calhoun, et al. Standards Track [Page 143] + +RFC 3588 Diameter Based Protocol September 2003 + + + In general, only generation of duplicates due to failover or re- + sending of records in non-volatile storage can be reliably detected + by Diameter clients or agents. In such cases the Diameter client or + agents can mark the message as possible duplicate by setting the T + flag. Since the Diameter server is responsible for duplicate + detection, it can choose to make use of the T flag or not, in order + to optimize duplicate detection. Since the T flag does not affect + interoperability, and may not be needed by some servers, generation + of the T flag is REQUIRED for Diameter clients and agents, but MAY be + implemented by Diameter servers. + + As an example, it can be usually be assumed that duplicates appear + within a time window of longest recorded network partition or device + fault, perhaps a day. So only records within this time window need + to be looked at in the backward direction. Secondly, hashing + techniques or other schemes, such as the use of the T flag in the + received messages, may be used to eliminate the need to do a full + search even in this set except for rare cases. + + The following is an example of how the T flag may be used by the + server to detect duplicate requests. + + A Diameter server MAY check the T flag of the received message to + determine if the record is a possible duplicate. If the T flag is + set in the request message, the server searches for a duplicate + within a configurable duplication time window backward and + forward. This limits database searching to those records where + the T flag is set. In a well run network, network partitions and + device faults will presumably be rare events, so this approach + represents a substantial optimization of the duplicate detection + process. During failover, it is possible for the original record + to be received after the T flag marked record, due to differences + in network delays experienced along the path by the original and + duplicate transmissions. The likelihood of this occurring + increases as the failover interval is decreased. In order to be + able to detect out of order duplicates, the Diameter server should + use backward and forward time windows when performing duplicate + checking for the T flag marked request. For example, in order to + allow time for the original record to exit the network and be + recorded by the accounting server, the Diameter server can delay + processing records with the T flag set until a time period + TIME_WAIT + RECORD_PROCESSING_TIME has elapsed after the closing + of the original transport connection. After this time period has + expired, then it may check the T flag marked records against the + database with relative assurance that the original records, if + sent, have been received and recorded. + + + + + +Calhoun, et al. Standards Track [Page 144] + +RFC 3588 Diameter Based Protocol September 2003 + + +Appendix D. Intellectual Property Statement + + The IETF takes no position regarding the validity or scope of any + intellectual property or other rights that might be claimed to + pertain to the implementation or use of the technology described in + this document or the extent to which any license under such rights + might or might not be available; neither does it represent that it + has made any effort to identify any such rights. Information on the + IETF's procedures with respect to rights in standards-track and + standards-related documentation can be found in BCP-11. Copies of + claims of rights made available for publication and any assurances of + licenses to be made available, or the result of an attempt made to + obtain a general license or permission for the use of such + proprietary rights by implementers or users of this specification can + be obtained from the IETF Secretariat. + + The IETF invites any interested party to bring to its attention any + copyrights, patents or patent applications, or other proprietary + rights which may cover technology that may be required to practice + this standard. Please address the information to the IETF Executive + Director. + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +Calhoun, et al. Standards Track [Page 145] + +RFC 3588 Diameter Based Protocol September 2003 + + +Authors' Addresses + + Pat R. Calhoun + Airespace, Inc. + 110 Nortech Parkway + San Jose, California, 95134 + USA + + Phone: +1 408-635-2023 + Fax: +1 408-635-2020 + EMail: pcalhoun@airespace.com + + John Loughney + Nokia Research Center + Itamerenkatu 11-13 + 00180 Helsinki + Finland + + Phone: +358 50 483 6242 + EMail: john.Loughney@nokia.com + + Jari Arkko + Ericsson + 02420 Jorvas + Finland + + Phone: +358 40 5079256 + EMail: Jari.Arkko@ericsson.com + + Erik Guttman + Sun Microsystems, Inc. + Eichhoelzelstr. 7 + 74915 Waibstadt + Germany + + Phone: +49 7263 911 701 + EMail: erik.guttman@sun.com + + Glen Zorn + Cisco Systems, Inc. + 500 108th Avenue N.E., Suite 500 + Bellevue, WA 98004 + USA + + Phone: +1 425 438 8218 + + + + + + +Calhoun, et al. Standards Track [Page 146] + +RFC 3588 Diameter Based Protocol September 2003 + + +Full Copyright Statement + + Copyright (C) The Internet Society (2003). 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 + document 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 + 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 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. + +Acknowledgement + + Funding for the RFC Editor function is currently provided by the + Internet Society. + + + + + + + + + + + + + + + + + + + +Calhoun, et al. Standards Track [Page 147] + |