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P. Calhoun Airespace, Inc. 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). 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]. All Rights Reserved.
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Table of Contents 1. Introduction................................................. 1.1. Diameter Protocol..................................... 1.1.1. Description of the Document Set.............. 1.2. Approach to Extensibility............................. 1.2.1. Defining New AVP Values...................... 1.2.2. Creating New AVPs............................ 1.2.3. Creating New Authentication Applications..... 1.2.4. Creating New Accounting Applications......... 1.2.5. Application Authentication Procedures........ 1.3. Terminology........................................... Protocol Overview............................................ 2.1. Transport............................................. 2.1.1. SCTP Guidelines.............................. 2.2. Securing Diameter Messages............................ 2.3. Diameter Application Compliance....................... 2.4. Application Identifiers............................... 2.5. Connections vs. Sessions.............................. 2.6. Peer Table............................................ 2.7. Realm-Based Routing Table............................. 2.8. Role of Diameter Agents............................... 2.8.1. Relay Agents................................. 2.8.2. Proxy Agents................................. 2.8.3. Redirect Agents.............................. 2.8.4. Translation Agents........................... 2.9. End-to-End Security Framework......................... 2.10. Diameter Path Authorization........................... Diameter Header.............................................. 3.1. Command Codes......................................... 3.2. Command Code ABNF specification....................... 3.3. Diameter Command Naming Conventions................... Diameter AVPs................................................ 4.1. AVP Header............................................ 4.1.1. Optional Header Elements..................... 4.2. Basic AVP Data Formats................................ 4.3. Derived AVP Data Formats.............................. 4.4. Grouped AVP Values.................................... 4.4.1. Example AVP with a Grouped Data Type......... 4.5. Diameter Base Protocol AVPs........................... Diameter Peers............................................... 5.1. Peer Connections...................................... 5.2. Diameter Peer Discovery............................... 5.3. Capabilities Exchange................................. 5.3.1. Capabilities-Exchange-Request................ 5.3.2. Capabilities-Exchange-Answer................. 5.3.3. Vendor-Id AVP................................ 5.3.4. Firmware-Revision AVP........................ 6 9 10 11 11 11 11 12 14 14 18 20 21 21 21 22 22 23 24 25 26 27 28 29 30 30 32 35 36 38 38 39 41 41 42 49 50 53 56 56 56 59 60 60 61 61
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5.3.5. Host-IP-Address AVP.......................... 5.3.6. Supported-Vendor-Id AVP...................... 5.3.7. Product-Name AVP............................. 5.4. Disconnecting Peer Connections........................ 5.4.1. Disconnect-Peer-Request...................... 5.4.2. Disconnect-Peer-Answer....................... 5.4.3. Disconnect-Cause AVP......................... 5.5. Transport Failure Detection........................... 5.5.1. Device-Watchdog-Request...................... 5.5.2. Device-Watchdog-Answer....................... 5.5.3. Transport Failure Algorithm.................. 5.5.4. Failover and Failback Procedures............. 5.6. Peer State Machine.................................... 5.6.1. Incoming connections......................... 5.6.2. Events....................................... 5.6.3. Actions...................................... 5.6.4. The Election Process......................... Diameter Message Processing.................................. 6.1. Diameter Request Routing Overview..................... 6.1.1. Originating a Request........................ 6.1.2. Sending a Request............................ 6.1.3. Receiving Requests........................... 6.1.4. Processing Local Requests.................... 6.1.5. Request Forwarding........................... 6.1.6. Request Routing.............................. 6.1.7. Redirecting Requests......................... 6.1.8. Relaying and Proxying Requests............... 6.2. Diameter Answer Processing............................ 6.2.1. Processing Received Answers.................. 6.2.2. Relaying and Proxying Answers................ 6.3. Origin-Host AVP....................................... 6.4. Origin-Realm AVP...................................... 6.5. Destination-Host AVP.................................. 6.6. Destination-Realm AVP................................. 6.7. Routing AVPs.......................................... 6.7.1. Route-Record AVP............................. 6.7.2. Proxy-Info AVP............................... 6.7.3. Proxy-Host AVP............................... 6.7.4. Proxy-State AVP.............................. 6.8. Auth-Application-Id AVP............................... 6.9. Acct-Application-Id AVP............................... 6.10. Inband-Security-Id AVP................................ 6.11. Vendor-Specific-Application-Id AVP.................... 6.12. Redirect-Host AVP..................................... 6.13. Redirect-Host-Usage AVP............................... 6.14. Redirect-Max-Cache-Time AVP........................... 6.15. E2E-Sequence AVP......................................
62 62 62 62 63 63 63 64 64 64 65 65 66 68 69 70 71 71 71 73 73 73 73 74 74 74 75 76 77 77 77 78 78 78 78 79 79 79 79 79 79 79 80 80 80 81 82
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. 7. 8............................................1........ Abort-Session-Request.3............................1...7.. 82 84 84 84 85 86 86 88 89 89 89 90 90 90 92 96 101 102 102 103 104 105 105 106 106 107 108 108 109 110 110 110 111 111 111 112 113 113 114 114 115 115 115 116 116 116 117 118 Calhoun......................................... 9..... Permanent Failures.. 9... 7.......1........................2... Diameter User Sessions. Origin-State-Id AVP... User-Name AVP.....6...................................... Multi-Round-Time-Out AVP. 7......... 8...............14.......... Re-Auth-Request-Type AVP......... Result-Code AVP........... Accounting Records............ 8.... 8.....................1...............................19......... 7..........................2.........3..... 8.......... Application Document Requirements...... Protocol Errors........... 8.................................... Session-Server-Failover AVP. 9.5...... Class AVP................ 8. 8.........16... 8. Authorization-Lifetime AVP............1..9........ Accounting..................... 8......1........ Session-Termination-Answer.21..... 8....4. Authorization Session State Machine....3. Inferring Session Termination from Origin-State-Id........ Session Termination..................4.......4. 7............... 8.................................................3......1.......................................... Protocol Messages........ Correlation of Accounting Records.................... 8.. Abort-Session-Answer... Event-Timestamp AVP..... 8. 8....11........... Re-Auth-Request... 8........... Aborting a Session. Error Handling.................. 9.... 7. 9................. 7........................ Auth-Session-State AVP....2........1......... 8...........18....... Experimental-Result AVP... Error-Reporting-Host AVP............. Transient Failures....................... Termination-Cause AVP........................................... 7............... 8....... Re-Auth-Answer.............. Server Directed Model..5...12...3.13........1...5....... 9.....15............ 7...................4.2......1...........1. Accounting Session State Machine......... Session-Id AVP....................................... 9.1.................... 8.... Error Bit.2...... 8...4... Session-Binding AVP................. Error-Message AVP......... 8................................ 8.............................. Auth-Request-Type AVP..4. Failed-AVP AVP....... Fault Resilience............................. Success............. 8.. 8.......20..................8...... Server-Initiated Re-Auth.................. Auth-Grace-Period AVP....... Experimental-Result-Code AVP..........5.5....................... 8. 7. et al........................ 7.6.... Informational....10.6.............17.................... 8...............................2..................... Standards Track [Page 4] ..................................3... 7...2. 8..............7..... Session-Termination-Request....................RFC 3588 Diameter Based Protocol September 2003 7.........5......... Session-Timeout AVP......... 8.......
.....RFC 3588 Diameter Based Protocol September 2003 Accounting Command-Codes............... Acct-Interim-Interval AVP. Redirect-Host-Usage AVP Values.. 11.... Accounting-Realtime-Required AVP..........4........ Acct-Session-Id AVP........ Result-Code AVP Values..1... 9..... Session-Server-Failover AVP Values..4.....4.. IPsec Usage.4.......... 11.......... 11.11...............2... Peer-to-Peer Considerations....3...........................................7..... 14...4....... References....... 11......... 13.. Accounting-Record-Type AVP Values............. et al......... Accounting-Answer. 9............ Termination-Cause AVP Values................ 9... Accounting AVPs... Accounting-Realtime-Required AVP Values........ Re-Auth-Request-Type AVP Values................ NAPTR Example. 9........2...2......2..... Base Protocol Command AVP Table....4........... 11.......................4... Appendix C.... Auth-Session-State AVP Values................7.......... Auth-Request-Type AVP Values...........7......................4............ 12...4.............1.8...... Duplicate Detection.......3..4....... 11. AVP Occurrence Table......4..... IANA Considerations.. 11.......... Diameter Service Template.... Accounting-Sub-Session-Id AVP.. Diameter Protocol Related Configurable Parameters............. Informative References..........................4...5.... Application Identifiers..............7.......... Acct-Multi-Session-Id AVP....... 11.... 11..........10....7.........5..........1. Command Flags.......2.........8.. 9........4....1...............................6....... Accounting-Record-Type AVP..... 9.......... Command Codes. 11...................9.......................... 10.........8.............. 13.. 14.................. Normative References.............1.......... Appendix B.................... 119 119 120 121 121 122 123 123 123 123 123 124 124 126 127 127 127 128 128 128 129 129 129 129 130 130 130 130 130 130 130 130 131 131 131 131 131 132 133 134 134 136 136 138 140 141 142 143 Calhoun.... 11...... 11............6. TLS Usage.. 11....8..................2..........2.......................... 14...........8......... Diameter Header..................... 11...... 11.................. Standards Track [Page 5] ............... 11. Security Considerations...........1................................. AVP Header..1... 9. Session-Binding AVP Values............ 11......1....8.............1....... Acknowledgements..........................2...5.....3.. Appendix A........... 10...... 9..............4............... 11......... 15..1. Accounting AVP Table....................... 11................8..............3..........1....... NAPTR Service Fields..................2....2. AVP Values......... AVP Flags.. 10............................2. 9.8..................... Disconnect-Cause AVP Values............ 9................................ Accounting-Request...... 13.... 11.... Accounting-Record-Number AVP............ 9..... AVP Code.8... Diameter TCP/SCTP Port Numbers..............6........... 13. 11............................... 11....
........ [RADIUS] does not provide support for per-packet confidentiality.. with the growth of the Internet and the introduction of new access technologies... Over time.......... and TLS support is optional.. it is typically not possible to define separate trust or authorization schemes for each application.. including wireless...... While [RFC3162] defines the use of IPsec with RADIUS.and inter-domain AAA deployments. 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.RFC 3588 Diameter Based Protocol September 2003 Appendix D.. While attribute-hiding is supported. 145 Authors' Addresses... Calhoun. use is only required during Extensible Authentication Protocol (EAP) sessions. 146 Full Copyright Statement... Diameter supports application-layer acknowledgements.5 and [AAATRANS].. [RADACCT] assumes that replay protection is provided by the backend billing server.. Introduction Authentication. failover behavior differs between implementations..... Mobile IP and Ethernet..... In order to provide universal support for transmission-level security... DSL.. et al. 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. Standards Track [Page 6] ..... putting new demands on AAA protocols. Intellectual Property Statement.... In order to provide well defined failover behavior. While [RADEXT] defines an additional authentication and integrity mechanism........... This is described in Section 5......... and as a result. and enable both intra.... routers and network access servers (NAS) have increased in complexity and density.. IPsec support is mandatory in Diameter.. and defines failover algorithms and the associated state machine..... These include: Failover [RADIUS] does not define failover mechanisms... Security is discussed in Section 13.... 147 1.... Transmission-level security [RADIUS] defines an application-layer authentication and integrity scheme that is required only for use with Response packets...... 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.. Network access requirements for AAA protocols are summarized in [AAAREQ]............ In accounting. rather than within the protocol itself.
as well as within gateways enabling communication between legacy RADIUS devices and Diameter agents. In order to provide well defined transport behavior. as a result. Server-initiated messages While RADIUS server-initiated messages are defined in [DYNAUTH].8. Auditability RADIUS does not define data-object security mechanisms. This makes it difficult to implement features such as unsolicited disconnect or reauthentication/reauthorization on demand across a heterogeneous deployment. While implementation of data object security is not mandatory within Diameter. and does not define retransmission behavior. Initially. et al. Support for server-initiated messages is mandatory in Diameter. including Proxies. Diameter runs over reliable transport mechanisms (TCP. Diameter defines agent behavior explicitly. this is a major issue in accounting. Agent support [RADIUS] does not provide for explicit support for agents. and as a result. SCTP) as defined in [AAATRANS]. where packet loss may translate directly into revenue loss. reliability varies between implementations. As described in [ACCMGMT]. Standards Track [Page 7] . by addition of a gateway or server speaking both RADIUS and Diameter. Combined with lack of support for capabilities negotiation. support is optional. described in [NASREQ]. considerable effort has been expended in enabling backward compatibility with RADIUS. Transition support While Diameter does not share a common protocol data unit (PDU) with RADIUS. this makes it very difficult to determine what occurred in the event of a dispute. it varies between implementations. it is expected that Diameter will be deployed within new network devices. Redirects and Relays. untrusted proxies may modify attributes or even packet headers without being detected. Calhoun. these capabilities are supported. so that the two protocols may be deployed in the same network. Since the expected behavior is not defined.RFC 3588 Diameter Based Protocol September 2003 Reliable transport RADIUS runs over UDP. This capability. this is described in Section 2. and are described in [AAACMS]. enables Diameter support to be added to legacy networks. and is described in Section 8.
Through DNS. Diameter enables dynamic discovery of peers. it remains feasible to implement Calhoun. However. and lacks auditability and transmission-level security features. and documented existing implementations (and imitations) of RADIUS-based roaming [PROXYCHAIN]. As a result. As a result. they may not be able to successfully negotiate a mutually acceptable service. Diameter includes support for error handling (Section 7). capability negotiation. Since RADIUS clients and servers are not aware of each other's capabilities. or in some cases. while Diameter is a considerably more sophisticated protocol than RADIUS. detailed roaming requirements [ROAMCRIT]. Roaming support The ROAMOPS WG provided a survey of roaming implementations [ROAMREV]. and mandatory/non-mandatory attribute-value pairs (AVPs) (Section 4. Standards Track [Page 8] . since RADIUS does not provide explicit support for proxies. defined the Network Access Identifier (NAI) [NAI].3). Diameter also provides support for the following: Capability negotiation RADIUS does not support error messages. or a mandatory/non-mandatory flag for attributes. RADIUSbased roaming is vulnerable to attack from external parties as well as susceptible to fraud perpetrated by the roaming partners themselves. the capabilities of Network Access Server (NAS) devices have increased substantially.7 and 6). Peer discovery and configuration RADIUS implementations typically require that the name or address of servers or clients be manually configured. Diameter addresses these limitations and provides for secure and scalable roaming. even be aware of what service has been implemented. facilitating roaming between providers. Derivation of dynamic session keys is enabled via transmission-level security. [PROXYCHAIN] introduced the concept of proxy chaining via an intermediate server. By providing explicit support for inter-domain roaming and message routing (Sections 2. auditability [AAACMS]. which can result in major security vulnerabilities if the Request Authenticator is not globally and temporally unique as required in [RADIUS]. and transmission-layer security (Section 13) features. et al.RFC 3588 Diameter Based Protocol September 2003 In addition to addressing the above requirements. it is not suitable for wide-scale deployment on the Internet [PROXYCHAIN]. In the decade since AAA protocols were first introduced. and creates the temptation to reuse the RADIUS shared secret. along with the corresponding shared secrets. capability negotiation (Section 5. In order to improve scalability.1). This results in a large administrative burden.
while others deliver data associated with particular applications that employ Diameter. It is also possible for the base protocol to be extended for use in new applications. or network access [NASREQ]. et al. proxying and redirecting of Diameter messages through a server hierarchy. Some of these AVP values are used by the Diameter protocol itself. Calhoun. At this time the focus of Diameter is network access and accounting applications. given improvements in processor speeds and the widespread availability of embedded IPsec and TLS implementations. or it may be used with a Diameter application. 1. Standards Track [Page 9] . AVPs are used by the base Diameter protocol to support the following required features: Transporting of user authentication information. it is imperative that the designers of new applications understand their requirements before using Diameter. between client and servers. for the purposes of enabling the Diameter server to authenticate the user.RFC 3588 Diameter Based Protocol September 2003 within embedded devices. as required by [AAAREQ]. so long as the required AVPs are included and AVPs that are explicitly excluded are not included. via the addition of new commands or AVPs.1. AVPs may be added arbitrarily to Diameter messages. Transporting of service specific authorization information. etc. The base protocol may be used by itself for accounting purposes only. capacity planning. Therefore. through addition of new commands and AVPs (required in [AAAREQ]). Exchanging resource usage information. Basic services necessary for applications. Relaying. such as handling of user sessions or accounting All data delivered by the protocol is in the form of an AVP. A truly generic AAA protocol used by many applications might provide functionality not provided by Diameter. - - - The Diameter base protocol provides the minimum requirements needed for a AAA protocol. such as Mobile IPv4 [DIAMMIP]. which MAY be used for accounting purposes. Diameter Protocol The Diameter base protocol provides the following facilities: Delivery of AVPs (attribute value pairs) Capabilities negotiation Error notification Extensibility. allowing the peers to decide whether a user's access request should be granted.
The Mobile IPv4 and the NASREQ documents describe applications that use this base specification for Authentication. The Diameter protocol also supports server-initiated messages. this document defines the base protocol specification for AAA. Description of the Document Set Currently. Diameter is a peerto-peer protocol. A Diameter node MAY act as an agent for certain requests while acting as a server for others. Standards Track [Page 10] . The Transport Profile document [AAATRANS] discusses transport layer issues that arise with AAA protocols and recommendations on how to overcome these issues.1. authorization. redirects and relay agents. A Diameter server performs authentication and/or authorization of the user. A Diameter client generates Diameter messages to request authentication. Any node can initiate a request. and accounting services for the user. such as a request to abort service to a particular user. which includes support for accounting.1. Consideration was given for servers that need to perform protocol conversion between Diameter and RADIUS.4 for more information on Diameter applications. In this document. agents include proxies. Transport Profile [AAATRANS] and applications: Mobile IPv4 [DIAMMIP]. the Diameter specification consists of a base specification (this document). In that sense. 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. A Diameter agent is a node that does not authenticate and/or authorize messages locally. such as a Network Access Server (NAS) or a Foreign Agent (FA). a Diameter Client is a device at the edge of the network that performs access control. In summary. Calhoun.RFC 3588 Diameter Based Protocol September 2003 See Section 2. This document also defines the Diameter failover algorithm and state machine. et al. and NASREQ [NASREQ]. 1. 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. Authorization and Accounting.
it is recommended that a Grouped AVP be used (see Section 4.1). In order to allocate a new AVP value. Approach to Extensibility The Diameter protocol is designed to be extensible. It is expected that command codes are reused.2.1.4) or a vendor specific Application Identifier. 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. new command codes can only be created by IETF Consensus (see Section 11.2.2.RFC 3588 Diameter Based Protocol September 2003 1. The request MUST include the commands that would make use of the AVP. a request MUST be sent to IANA. et al. In the event that a logical grouping of AVPs is necessary. Creating New Authentication Applications Every Diameter application specification MUST have an IANA assigned Application Identifier (see Section 2.3. AVPs and Diameter applications are strongly recommended.2. 1. 1. using several mechanisms. a request MUST be sent to IANA [IANA]. Standards Track [Page 11] .2.2. as opposed to creating new AVPs. In order to create a new AVP. Defining New AVP Values New applications should attempt to reuse AVPs defined in existing applications when possible. with a specification for the AVP. a new AVP should be created. an application may require a new value to communicate some service-specific information. Calhoun. Creating New AVPs The When no existing AVP can be used.4). Reuse simplifies standardization and implementation and avoids potential interoperability issues. new AVP being defined MUST use one of the data types listed in Section 4. and multiple "groups" are possible in a given command.2. IANA considerations for Diameter are discussed in Section 11. 1. along with an explanation of the new AVP value. For AVPs of type Enumerated.
However. it MUST also specify the AVPs that are to be present in the Diameter Accounting messages (see Section 9. does not imply that a new accounting application id is required. - Creation of a new application should be viewed as a last resort. just because a new authentication application id is required.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. An implementation MAY add arbitrary non-mandatory AVPs to any command defined in an application. which have the "M" bit set. Such services need to define the AVPs carried in the Accounting-Request (ACR)/ Accounting-Answer (ACA) messages. 1. et al. The expected AVPs MUST be defined in an ABNF [ABNF] grammar (see Section 3.4. Adding support for an authentication method requiring definition of new AVPs for use with the application. Diameter applications MUST define one Command Code. Please refer to Section 11. it may be desirable to create a new Diameter application. but new application bar has a command that requires two round trips to complete).2. in order to avoid defining multiple AVPs that carry similar information.3). or add new mandatory AVPs to the ABNF. Creating New Accounting Applications There are services that only require Diameter accounting. If the Diameter application has accounting requirements. Major changes to an application include: Adding new AVPs to the command. Standards Track [Page 12] ..1 for details. application foo has a command that requires one round trip. In order to justify allocation of a new application identifier. but do not need to define new command codes. including vendor-specific AVPs without needing to define a new application. When possible. a new Diameter application SHOULD reuse existing Diameter AVPs. An implementation MAY add arbitrary non-mandatory AVPs (AVPs with the "M" bit not set) to any command defined in an Calhoun.2). 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. Requiring a command that has a different number of round trips to satisfy a request (e.g.1.
when the AVP is included within an accounting command..g.RFC 3588 Diameter Based Protocol September 2003 application... Every Diameter accounting application specification MUST have an IANA assigned Application Identifier (see Section 2. as long as no new mandatory AVPs are added. Within an accounting command. it MUST NOT have the "M" bit set. application defined state machine). billing server) or the accounting server itself MUST understand the AVP in order to compute a correct bill.4) or a vendor specific Application Identifier. regardless of whether it is required or optional within the ABNF for the accounting application. 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. 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. Standards Track [Page 13] . in order to avoid defining multiple AVPs that carry similar information.1. then the base protocol defined standard accounting application Id (Section 2. Application Identifiers are still required for Diameter capability exchange. without needing to define a new accounting application. A mandatory AVP is defined as one which has the "M" bit set when sent within an accounting command. 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. even if the "M" bit is set when the same AVP is used within other Diameter commands (i. new commands or additional mechanisms (e. Calhoun.e.4) MUST be used in ACR/ACA commands.g. or new mandatory AVPs are added to the ABNF.g. a new Diameter accounting application SHOULD attempt to reuse existing AVPs..1 for details. If the base accounting is used without any mandatory AVPs. 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. application defined state machine) is defined within the application. setting the "M" bit implies that a backend server (e. Please refer to Section 11. including vendor-specific AVPs. When possible. et al. authentication/authorization commands). If the AVP is not relevant to the billing process.
Application Authentication Procedures When possible. et al. Authorization The act of determining whether a requesting entity (subject) will be allowed access to a resource (object). An AVP includes a header and is used to encapsulate protocol-specific data (e. proxy or redirect agent. 1. Accounting servers creating the accounting record may do so by processing interim accounting events or accounting events from several devices serving the same user. Broker A broker A broker operated a broker agents. SHOULD be used. applications SHOULD be designed such that new authentication methods MAY be added without requiring changes to the application. such as Extensible Authentication Protocol [EAP]. authentication frameworks. AAA Authentication. auditing. This MAY require that new AVP values be assigned to represent the new authentication transform. Accounting Record An accounting record represents a summary of the resource consumption of a user over the entire session. and MAY be by roaming consortiums. Accounting The act of collecting information on resource usage for the purpose of capacity planning. When possible. Authorization and Accounting. AVP The Diameter protocol consists of a header followed by one or more Attribute-Value-Pairs (AVPs). or any other scheme that produces similar results. Depending on the business model. authorization or accounting information. Terminology is a business term commonly used in AAA infrastructures.5.g.2.RFC 3588 Diameter Based Protocol September 2003 1. may either choose to deploy relay agents or proxy Calhoun.3. billing or cost allocation. is either a relay.. Authentication The act of verifying the identity of an entity (subject). routing information) as well as authentication. Standards Track [Page 14] .
et al. Agent or Server. End-to-end security is security between two Diameter nodes. proxy. Home Realm A Home Realm is the administrative domain with which the user maintains an account relationship.RFC 3588 Diameter Based Protocol September 2003 Diameter Agent A Diameter Agent is a Diameter node that provides either relay. redirect or translation services. this hop-by-hop security does not protect the entire Diameter user session. Calhoun. This security protects the entire Diameter communications path from the originating Diameter node to the terminating Diameter node. its very nature. Diameter Peer A Diameter Peer is a Diameter Node to which a given Diameter Node has a direct transport connection. a Diameter Server MUST support Diameter applications in addition to the base protocol. Diameter Node A Diameter node is a host process that implements the Diameter protocol. An example of a Diameter client is a Network Access Server (NAS) or a Foreign Agent (FA). Diameter Server A Diameter Server is one that handles authentication. or security across a transport connection. When relays or proxy are involved. authorization and accounting requests for a particular realm. Diameter Client A Diameter Client is a device at the edge of the network that performs access control. Standards Track [Page 15] . and acts either as a Client. Home Server See Diameter Server. By 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. Diameter Security Exchange A Diameter Security Exchange is a process through which two Diameter nodes establish end-to-end security. possibly communicating through Diameter Agents.
Diameter makes use of the realm. An administrative domain MAY act as a local realm for certain users. is used in the Diameter protocol to extract a user's identity and realm. and are piggybacked on the administration of the DNS namespace. they may originate Reject messages in cases where policies are violated. 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. or NAI [NAI]. to determine whether messages can be satisfied locally. Realm The string in the NAI that immediately follows the '@' character. Multi-session A multi-session represents Multi-sessions are tracked example of a multi-session leg of the bundle would be be a multi-session. As a result. An would be a Multi-link PPP bundle. while being a home realm for others. In RADIUS. or whether they must be routed or redirected.RFC 3588 Diameter Based Protocol September 2003 Interim accounting An interim accounting message provides a snapshot of usage during a user's session. Standards Track [Page 16] . proxies need to understand the semantics of the messages passing through them. and may not support all Diameter applications. This is typically accomplished by tracking the state of NAS devices. The identity is used to identify the user during authentication and/or authorization. by using the Acct-Multi-Session-Id. while the realm is used for message routing purposes. NAI realm names are required to be unique. et al. Proxy Agent or Proxy In addition to forwarding requests and responses. also loosely referred to as domain. proxies make policy decisions relating to resource usage and provisioning. realm names are not necessarily piggybacked on the DNS namespace but may be independent of it. Local Realm A local realm is the administrative domain providing services to a user. a logical linking of several sessions. Each a session while the entire bundle would Network Access Identifier The Network Access Identifier. While proxies typically do not respond to client Requests prior to receiving a Response from the server. Calhoun.
Roaming Relationships Roaming relationships include relationships between companies and ISPs. As a result. et al. while acting as relay or proxy agents for other types. and are capable of handling any Diameter application or message type. they do not alter any AVPs transiting between client and server. All Diameter packets with the same Session-Identifier are considered to be part of the same session. Calhoun. they do not examine or alter non-routing AVPs. redirect agents do not keep state with respect to sessions or NAS resources. Since redirect agents do not sit in the forwarding path. although they may be configured only to redirect messages of certain types. Time constraints are typically imposed in order to limit financial risk.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. 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. relays never originate messages. Session A session is a related progression of events devoted to a particular activity. 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. Standards Track [Page 17] . even in the presence of relays and/or proxies. As with proxy agents. Each application SHOULD provide guidelines as to when a session begins and ends. do not need to understand the semantics of messages or non-routing AVPs. Since relays do not make policy decisions. and relationships between an ISP and a roaming consortium. Redirect agents do not originate messages and are capable of handling any message type. Relay Agent or Relay Relays forward requests and responses based on routing-related AVPs and realm routing table entries. relationships among peer ISPs within a roaming consortium. Redirect Agent Rather than forwarding requests and responses between clients and servers. redirect agents refer clients to servers and allow them to communicate directly.
Transaction state implies that upon forwarding a request. simultaneous voice and data transfer during the same session) or serially. but for use in authentication and authorization it is always extended for a particular application. otherwise known as a Peerto-Peer Connection. which is used for failover purposes. which is restored to its original value when the corresponding answer is received. the Hop-by-Hop identifier is saved. These services may happen concurrently (e. such as RADIUS. 2. or by expiration. and its state is considered active either until it is notified otherwise. Standards Track [Page 18] . by keeping track of all authorized active sessions. The request's state is released upon receipt of the answer. These changes in sessions are tracked with the Accounting-Sub-Session-Id. Upstream Upstream is used to identify the direction of a particular Diameter message from the access device towards the home server. Calhoun. QoS or data characteristics) provided to a given session. Sub-session A sub-session represents a distinct service (e.g. User The entity requesting or using some resource. in support of which a Diameter client has generated a request.. A stateless agent is one that only maintains transaction state. Transport Connection A transport connection is a TCP or SCTP connection existing directly between two Diameter peers. Two Diameter applications are defined by companion documents: NASREQ [NASREQ]. Each authorized session is bound to a particular service. et al. Transaction state The Diameter protocol requires that agents maintain transaction state.RFC 3588 Diameter Based Protocol September 2003 Session state A stateful agent is one that maintains session state information. Protocol Overview The base Diameter protocol may be used by itself for accounting applications.g. Translation Agent A translation agent is a stateful Diameter node that performs protocol translation between Diameter and another AAA protocol. the field is replaced with a locally unique identifier..
In addition. and not a "Diameter Client". which includes accounting. e. The base protocol also defines certain rules that apply to all exchanges of messages between Diameter nodes. they MUST fully support each Diameter application that is needed to implement the client's service. e. et al. The base Diameter protocol concerns itself with capabilities negotiation. A Diameter Client that does not support both NASREQ and Mobile IPv4. protocol transparent. In addition. NASREQ and/or Mobile IPv4. and MUST transparently support the Diameter base protocol. NASREQ and/or Mobile IPv4. The Session-Id is then used in all subsequent messages to identify the user's session (see Section 8 for more information). Additional Diameter applications MAY be defined in the future (see Section 11.RFC 3588 Diameter Based Protocol September 2003 Mobile IPv4 [DIAMMIP]. MUST be referred to as "Diameter X Proxy" where X is the application which it supports. which includes accounting.g. The set of AVPs included in the message is determined by a particular Diameter application. In addition.. Standards Track [Page 19] . Diameter proxies MUST support the base protocol.g. Diameter Relays and redirect agents are. which includes accounting. or reject it by returning an answer message with the Result-Code AVP Calhoun. A Diameter Server that does not support both NASREQ and Mobile IPv4. and not a "Diameter Proxy". A Diameter proxy which does not support also both NASREQ and Mobile IPv4. they MUST fully support each Diameter application that is needed to implement the intended service. The initial request for authentication and/or authorization of a user would include the Session-Id. and not a "Diameter Server". e.3). Diameter Servers MUST support the base protocol. by definition... which includes accounting.g. MUST be referred to as "Diameter X Client" where X is the application which it supports. how messages are sent and how peers may eventually be abandoned. MUST be referred to as "Diameter X Server" where X is the application which it supports. they MUST fully support each Diameter application that is needed to implement proxied services. One AVP that is included to reference a user's session is the Session-Id. These applications are introduced in this document but specified elsewhere. The communicating party may accept the request. Diameter Clients MUST support the base protocol. and all Diameter applications. Communication between Diameter peers begins with one peer sending a message to another Diameter peer. NASREQ and/or Mobile IPv4.
2 for more information on peer discovery. The specific behavior of the Diameter server or client receiving a request depends on the Diameter application employed. subject to security policy on trusting such messages. unless multiple instances exist on the peer in which case a separate connection per process is allowed. et al.1. The base Diameter protocol is run on port 3868 of both TCP [TCP] and SCTP [SCTP] transport protocols. Session state (associated with a Session-Id) MUST be freed upon receipt of the Session-Termination-Request. Diameter clients MUST support either TCP or SCTP. When no transport connection exists with a peer. expiration of authorized service time in the Session-Timeout AVP. 2. See Section 5. and according to rules established in a particular Diameter application. Future versions of this specification MAY mandate that clients support SCTP. while agents and servers MUST support both. and MUST be prepared to receive connections on port 3868. an attempt to connect SHOULD be periodically made. SCTP SHOULD be tried first. This behavior is handled via the Tc timer. whose recommended value is 30 seconds. When connecting to a peer and either zero or more transports are specified. Diameter implementations SHOULD also be able to interpret a reset from the transport and timed-out connection attempts. such as when a peer has terminated the transport connection stating that it does not wish to communicate. Transport Transport profile is defined in [AAATRANS].RFC 3588 Diameter Based Protocol September 2003 set to indicate an error occurred. Diameter implementations SHOULD be able to interpret ICMP protocol port unreachable messages as explicit indications that the server is not reachable. Standards Track [Page 20] . Calhoun. A given Diameter instance of the peer state machine MUST NOT use more than one transport connection to communicate with a given peer. Session-TerminationAnswer. A Diameter node MAY initiate connections from a source port other than the one that it declares it accepts incoming connections on. followed by TCP. There are certain exceptions to this rule.
1. 2. including vendor-specific AVPs. See Sections 13. This also eases the requirements on the NAS support certificates. et al.1. SCTP Guidelines The following are guidelines for Diameter implementations that support SCTP: 1. described in the specification.1 and 13. Securing Diameter Messages Diameter clients. For a given application. It is suggested that IPsec can be used primarily at the edges intra-domain traffic. It is also suggested that inter-domain would primarily use TLS. such as Network Access Servers (NASes) and Mobility Agents MUST support IP Security [SECARCH]. The transport connection MUST be closed using a RESET call (send a TCP RST bit) or an SCTP ABORT message (graceful closure is compromised). the stream is compromised and cannot be recovered.2. 2. The Diameter protocol MUST NOT be used without any security mechanism (TLS or IPsec). such as using pre-shared keys between a local AAA proxy.2 for more on IPsec and TLS usage. Calhoun.3. and MAY support TLS [TLS]. For interoperability: All Diameter nodes MUST be prepared to receive Diameter messages on any SCTP stream in the association. and the AVPs specified in the associated ABNFs. 2.3). An implementation MAY add arbitrary non-mandatory AVPs to any command defined in an application. Diameter Application Compliance and in NAS a to traffic details Application Identifiers are advertised during the capabilities exchange phase (see Section 5. Standards Track [Page 21] . To prevent blocking: All Diameter nodes SHOULD utilize all SCTP streams available to the association to prevent head-of-the-line blocking.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. Diameter servers MUST support TLS and IPsec. Please refer to Section 11. 2.1.1 for details. advertising support of an application implies that the sender supports all command codes.
If none can be found.5. 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. and is shared between an access device and a server. while all other Diameter nodes MUST advertise locally supported applications. A session is a logical concept at the application layer. Sessions This section attempts to provide the reader with an understanding of the difference between connection and session. Application Identifiers Each Diameter application MUST have an IANA assigned Application Identifier (see Section 11. Connections vs. 2.3). Diameter nodes inform their peers of locally supported applications. an error message is returned with the Result-Code AVP set to DIAMETER_UNABLE_TO_DELIVER. used to send and receive Diameter messages. Standards Track [Page 22] . all Diameter messages contain an Application Identifier.RFC 3588 Diameter Based Protocol September 2003 2. The base protocol does not require an Application Identifier since its support is mandatory. which are terms used extensively throughout this document. and is identified via the Session-Id AVP Calhoun. which is used in the message forwarding process. A connection is a transport level connection between two peers. Furthermore.4. et al. The following Application Identifier values are defined: Diameter Common Messages NASREQ Mobile-IP Diameter Base Accounting Relay 0 1 [NASREQ] 2 [DIAMMIP] 3 0xffffffff Relay and redirect agents MUST advertise the Relay Application Identifier. During the capabilities exchange.
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+--------+ +-------+ +--------+ | 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.
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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.
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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.
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This is known as the Realm Routing Table. Each authorized session is bound to a particular service.7. Calhoun. et al. Standards Track [Page 26] . This routing decision is performed using a list of supported realms. which is communicated by Diameter servers via the Session-Timeout AVP. Destination-Realm).8. which is restored to its original value when the corresponding answer is received. 2. Transaction state implies that upon forwarding a request.g. which is used for failover purposes. A complex network will have multiple authentication sources. by keeping track of all authorized active sessions.1. The Proxy-Info AVP allows stateless agents to add local state to a Diameter request. its Hop-by-Hop identifier is saved. Each authorized session has an expiration. The request's state is released upon receipt of the answer. Maintaining session state MAY be useful in certain applications. the field is replaced with a locally unique identifier. such as: Protocol translation (e. 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.RFC 3588 Diameter Based Protocol September 2003 - They can be used for load balancing. and as another type of agent for others.. and its state is considered active either until it is notified otherwise.. A stateful agent is one that maintains session state information. as is defined further in Section 2. they can sort requests and forward towards the correct target. the protocol's failover procedures require that agents maintain a copy of pending requests. A stateless agent is one that only maintains transaction state. However. with the guarantee that the same state will be present in the answer. The Diameter protocol requires that agents maintain transaction state. A Diameter implementation MAY act as one type of agent for some requests. 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. or by expiration. and known peers.g.
com. NAS performs a Diameter route lookup. and determines that the message is to be relayed to DRL. Calhoun. et al. access devices) to enforce resource usage. but do not modify any other portion of a message.2. Relays modify Diameter messages by inserting and removing routing information. 2. and provisioning. and relays the message to HMS. processes the authentication and/or authorization request. changed or deleted.net ---------> 1. which is routed back to NAS using saved transaction state. they differ since they modify messages to implement policy enforcement. +------+ | | | NAS | | | +------+ example.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). This requires that proxies maintain the state of their downstream peers (e. However. which is example. HMS identifies that the request can be locally supported (via the realm). Since Relays do not perform any application level processing. Relays SHOULD NOT maintain session state but MUST maintain transaction state. and therefore MUST advertise the Relay Application Identifier. Request 3. Request 4.net ---------> 2. DRL performs the same route lookup as NAS. which is a Diameter Relay.g. using "example. and replies with an answer.com Figure 2: Relaying of Diameter messages The example provided in Figure 2 depicts a request issued from NAS. for the user bob@example. provide admission control. Proxy Agents Similarly to relays.8. proxy agents route Diameter messages using the Diameter Routing Table.com" as the key. 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. Standards Track [Page 27] . Answer <--------+------+ | | | HMS | | | +------+ example.com's Home Diameter Server. Prior to issuing the request. they provide relaying services for all Diameter applications. which is an access device.. this reduces the configuration load on Diameter servers that would otherwise be necessary when NASes are added. Answer <--------+------+ | | | DRL | | | +------+ example. Likewise.
they can monitor the number and types of ports in use. which is a redirect agent that returns a redirect notification to DRL. The message is forwarded by the NAS to its relay. DRL. they are not required to maintain transaction state. An example is a redirect agent that provides services to all members of a consortium. Proxies MUST only advertise the Diameter applications they support.RFC 3588 Diameter Based Protocol September 2003 It is important to note that although proxies MAY provide a value-add function for NASes. Standards Track [Page 28] . they cannot maintain session state. and forwards the request to it. Proxies that wish to limit resources MUST maintain session state. which does not have a routing entry in its Diameter Routing Table for example. Upon receipt of the redirect notification.com. and only return an answer with the information necessary for Diameter agents to communicate directly. DRL establishes a transport connection with HMS. Proxies MAY be used in call control centers or access ISPs that provide outsourced connections. The example provided in Figure 3 depicts a request issued from the access device. as well as HMS' contact information. Since redirect agents do not receive answer messages. they do not allow access devices to use end-toend security. 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.3. DRL has a default route configured to DRD. for the user bob@example. et al.com. All proxies MUST maintain transaction state. and make allocation and admission decisions according to their configuration. 2. since modifying messages breaks authentication. Since redirect agents do not relay messages. Calhoun. Further. Since enforcing policies requires an understanding of the service being provided. Redirect Agents Redirect agents are useful in scenarios where the Diameter routing configuration needs to be centralized.8. if one doesn't already exist. since redirect agents never relay requests. NAS. but does not wish to be burdened with relaying all messages between realms. they do not modify messages.
Request | | 3. Standards Track [Page 29] . Redirection | | Notification | v ---------> +------+ ---------> 1.8. et al. +------+ ---------> | | RADIUS Request | NAS | | | RADIUS Answer +------+ <--------example.net +------+ ---------> +------+ | | Diameter Request | | | TLA | | HMS | | | Diameter Answer | | +------+ <--------+------+ example. 2. TACACS+<->Diameter). and therefore MUST advertise the Relay Application Identifier. they provide relaying services for all Diameter applications. RADIUS<->Diameter..com Figure 4: Translation of RADIUS to Diameter Calhoun. Request | | 4. Translation Agents A translation agent is a device that provides translation between two protocols (e.net +------+ | | | DRD | | | +------+ ^ | 2.net +------+ | | | HMS | | | +------+ example. translation agents MUST be session stateful and MUST maintain transaction state.com Figure 3: Redirecting a Diameter Message Since redirect agents do not perform any application level processing. Given that the Diameter protocol introduces the concept of long-lived authorized sessions.g. Translation agents are likely to be used as aggregation servers to communicate with a Diameter infrastructure. and therefore translation agents MUST only advertise their locally supported applications.net example. Answer | | 5.RFC 3588 Diameter Based Protocol September 2003 +------+ | | | NAS | | | +------+ example. Translation of messages can only occur if the agent recognizes the application of a particular request. Request | DRL | 6. while allowing for the embedded systems to be migrated at a slower pace. Answer <--------+------+ <--------example.4.
Before initiating a connection. where TLS or IPsec transmissionlevel security is sufficient. For example. communicating through agents. Use end-to-end security on messages containing sensitive AVPs. In addition to authenticating each connection.9. which are not the subject of standardization. Diameter Path Authorization As noted in Section 2. These services are provided by supporting AVP integrity and confidentiality between two peers.2. Always use end-to-end security. Which AVPs are sensitive is determined by service provider policy. there may be no need for end-to-end security. End-to-End Security Framework End-to-end security services include confidentiality and message origin authentication.10. - It is strongly RECOMMENDED that all Diameter implementations support end-to-end security. Any AVP for which the P bit may be set or which may be encrypted may be considered sensitive. described in [AAACMS]. Therefore. Calhoun. each connection as well as the entire session MUST also be authorized. Diameter requires transmission level security to be used on each connection (TLS or IPsec). a Diameter Peer MUST check that its peers are authorized to act in their roles. End-to-end security is provided via the End-to-End security extension. The circumstances requiring the use of end-to-end security are determined by policy on each of the peers. et al. a Diameter peer may be authentic. Accounting AVPs may be considered sensitive. Standards Track [Page 30] . 2. For example. may be applied by next hop Diameter peer or by destination realm. End-to-end security policies include: Never use end-to-end security. replay and integrity protected and confidential on a per-packet basis.RFC 3588 Diameter Based Protocol September 2003 2. each connection is authenticated. but that does not mean that it is authorized to act as a Diameter Server advertising a set of Diameter applications. Security policies. AVPs containing keys and passwords should be considered sensitive.
For example. the local Diameter agent. As noted in Section 6. Standards Track [Page 31] . By authorizing a request. administrators within the home realm may not wish to honor requests that have been routed through an untrusted realm. then a DIAMETER_UNABLE_TO_COMPLY error message MUST be sent within the accounting request. for example. Diameter capabilities negotiation (CER/CEA) also MUST be carried out. in order to determine what Diameter applications are supported by each peer. Accounting requests without corresponding authorization responses SHOULD be subjected to further scrutiny. The AVP contains the identity of the peer the request was received from. If the service cannot be provided by the local realm. on receiving a Diameter response authorizing a session. a relay or proxy agent MUST append a Route-Record AVP to all requests forwarded. By issuing an accounting request corresponding to the authorization response. a Diameter client receiving an authorization response for a service that it cannot perform MUST NOT substitute an alternate service. At each step. forwarding of an authorization response is considered evidence of a willingness to take on financial risk relative to the session. MUST check the Route-Record AVPs to make sure that the route traversed by the response is acceptable. and then send accounting requests for the alternate service instead.8. by establishing credit limits for intermediate realms and refusing to accept responses which would violate those limits. A DIAMETER_AUTHORIZATION_REJECTED error message (see Section 7. as should accounting requests indicating a difference between the requested and provided service. The home Diameter server. et al. authorization checks are performed at each connection along the path. prior to authorizing a session. A home realm may also wish to check that each accounting request message corresponds to a Diameter response authorizing the session. 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.RFC 3588 Diameter Based Protocol September 2003 Prior to bringing up a connection. Calhoun. the local realm implicitly indicates its agreement to provide the service indicated in the authorization response.1.1. A local realm may wish to limit this exposure. Similarly.5) is sent if the route traversed by the request is unacceptable. Diameter sessions MUST be routed only through authorized nodes that have advertised support for the Diameter application required by the session. MUST check the Route-Record AVPs to make sure that the route traversed by the request is acceptable.
If set. +-+-+-+-+-+-+-+-+-+-+-+-+Version This Version field MUST be set to 1 to indicate Diameter Version 1. the message is a request. The fields 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 . If cleared.RFC 3588 Diameter Based Protocol September 2003 3. the message MUST be locally processed. E(rror) . are transmitted in network byte order. assigned: 0 1 2 3 4 5 6 7 +-+-+-+-+-+-+-+-+ |R P E T r r r r| +-+-+-+-+-+-+-+-+ R(equest) . and the message will not conform to the ABNF described for this command. Diameter Header A summary of the Diameter header format is shown below. If cleared. Command Flags The Command Flags field is eight bits.If set. the message MAY be proxied. the message contains a protocol error.If set. the message is an answer.. Message Length The Message Length field is three octets and indicates the length of the Diameter message including the header fields. relayed or redirected. Standards Track [Page 32] . P(roxiable) . Messages with the 'E' The following bits are Calhoun.. et al.
g. and is used in order to communicate the command associated with the 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..2. a protocol error) has been received for the earlier message. This bit MUST NOT be set in request messages. Command-Code values 16. otherwise the sender MUST set this flag. Diameter agents that receive a request with the T flag set. Diameter agents only need to be concerned about the number of requests they send based on a single received request. as an indication of a possible duplicate due to a link failure. r(eserved) .This flag is set after a link failover procedure. Application-ID Application-ID is four octets and is used to identify to which application the message is applicable for. Calhoun.2.214 and 16. and ignored by the receiver. Standards Track [Page 33] . See Section 7. This flag MUST NOT be set in answer messages.3 for the possible values that the application-id may use. It is set when resending requests not yet acknowledged. The application-id in the header MUST be the same as what is contained in any relevant AVPs contained in the message. retransmissions by other entities need not be tracked.1). This flag MUST NOT be set if an error answer message (e. et al. Command-Code The Command-Code field is three octets.215 (hexadecimal values FFFFFE -FFFFFF) are reserved for experimental use (See Section 11.3). The 24-bit address space is managed by IANA (see Section 11. MUST keep the T flag set in the forwarded request. See Section 11. to aid the removal of duplicate requests. The application can be an authentication application. an accounting application or a vendor specific application.RFC 3588 Diameter Based Protocol September 2003 bit set are commonly referred to as error messages.777. T(Potentially re-transmitted message) .these flag bits are reserved for future use. and MUST be set to zero.777. This bit MUST be cleared when sending a request for the first time.
even 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. Duplicate answer messages that are to be locally consumed (see Section 6. and MAY attempt to ensure that the number is unique across reboots. The sender MUST ensure that the Hop-by-Hop identifier in a request is unique on a given connection at any given time. An answer message that is received with an unknown Hop-by-Hop Identifier MUST be discarded. Senders of request messages MUST insert a unique identifier on each message. and MUST NOT affect any state that was set when the original request was processed. The identifier MUST remain locally unique for a period of at least 4 minutes. 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).2) SHOULD be silently discarded. Upon reboot implementations MAY set the high order 12 bits to contain the low order 12 bits of current time.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 End-to-End Identifier MUST NOT be modified by Diameter agents of any kind. Calhoun. AVPs AVPs are a method of encapsulating information relevant to the Diameter message. and the low order 20 bits to a random value. 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 combination of the Origin-Host (see Section 6. et al. The Hop-by-Hop identifier is normally a monotonically increasing number. Standards Track [Page 34] . whose start value was randomly generated.3) and this field is used to detect duplicates. See Section 4 for more information on AVPs. 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.
7.1 Request Capabilities-ExchangeCEA 257 5.1 Re-Auth-Answer RAA 258 8.2 Capabilities-ExchangeCER 257 5. which is used to determine the action that is to be taken for a particular message.126.96.36.199.2 Answer Calhoun.1.2 Re-Auth-Request RAR 258 8.3.1 Request Session-TerminationSTA 275 8. and the sub-type (i.7.. Standards Track [Page 35] .2 Session-TerminationSTR 275 8.1 Disconnect-Peer-Answer DPA 282 5.2 Disconnect-Peer-Request DPR 282 5.RFC 3588 Diameter Based Protocol September 2003 3. request or answer) is identified via the 'R' bit in the Command Flags field of the Diameter header.4.4. The following Command Codes are defined in the Diameter base protocol: Command-Name Abbrev.2 Accounting-Request ACR 271 9. Code Reference -------------------------------------------------------Abort-Session-Request ASR 274 8.4.e.1 Accounting-Answer ACA 271 9.1 Abort-Session-Answer ASA 274 8.4.2 Answer Device-Watchdog-Request DWR 280 5.3. et al. Command Codes Each command Request/Answer pair is assigned a command code.3. Every Diameter message MUST contain a command code in its header's Command-Code field.5.1 Device-Watchdog-Answer DWA 280 5.
indicating that the message . Flags is set. anywhere in the message. PXY" . the 'P' bit in the Command . ERR" . is a request. indicating that the message . the 'R' bit in the Command . message contains a Result-Code AVP in . Flags is set. as opposed to an answer. is proxiable. = ". If present. Defines the fixed position of an AVP = [qual] "{" avp-spec "}" . the "protocol error" class. Standards Track [Page 36] . et al. Flags is set. Command Code ABNF specification Every Command Code defined MUST include a corresponding ABNF specification. application-id command-id r-bit p-bit e-bit fixed required Calhoun. which is used to define the AVPs that MUST or MAY be present. = [qual] "<" avp-spec ">" . The Command Code assigned to the command = ". the 'E' bit in the Command . If present. If present.2. = ". REQ" . The following format is used in the definition: command-def command-name diameter-name = command-name "::=" diameter-message = 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]">" = 1*DIGIT = 1*DIGIT .RFC 3588 Diameter Based Protocol September 2003 3. indicating that the answer . The AVP MUST be present and can appear .
or optional . AVP Name. RFC 2234 Section 6. .RFC 3588 Diameter Based Protocol September 2003 optional = [qual] "[" avp-name "]" . = 1*DIGIT . rule. The absence of any qualifiers depends on whether . above). = diameter-name . = avp-spec / "AVP" . be present. The minimum number of times the element may . which does not conflict with the . . The avp-name in the 'optional' rule cannot . be present. defined . optional fixed rules (such as an optional . than in ABNF (see the optional rule. To do this. in the base or extended Diameter . present. If an optional rule has no . appear anywhere in the message. The avp-spec has to be an AVP Name. The default value is infinity.6. ICV at the end). then exactly one such AVP MUST . evaluate to any AVP Name which is included . The default value is zero. qualifier. qual min max A avp-spec avp-name Calhoun. the convention . . et al. The string "AVP" stands for *any* arbitrary . is '0*1fixed'. present. The AVP can . Standards Track [Page 37] . . specifications. . in a fixed or required rule. = 1*DIGIT . If a fixed or required rule has no . NOTE: "[" and "]" have a different meaning . These braces cannot be used to express . value of zero implies the AVP MUST NOT be . The maximum number of times the element may . be present. required or fixed position AVPs defined in . = [min] "*" [max] . See ABNF conventions. the command code definition. it precedes a fixed. then 0 or 1 such AVP may be . required. qualifier.
routing and security information as well as configuration details for the request and reply. while the acronyms are STR and STA. Each English word is delimited by a hyphen. MAY also be included in answer messages. but provides information about a Diameter peer that is able to satisfy the request. REQ. The command name is Session-Terminate-Request and Session-Terminate-Answer. and is specified in each case by the AVP description. - Additional information. Some AVPs MAY be listed more than once. The request is identified by the R(equest) bit in the Diameter header set to one (1). The effect of such an AVP is specific. et al. to ask that a particular action be performed. Diameter AVPs Diameter AVPs carry specific authentication. Standards Track [Page 38] . 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. Once the receiver has completed the request it issues the corresponding answer. "Diameter-Header: 9999999. Both the request and the answer for a given command share the same command code. A three-letter acronym for both the request and answer is also normally provided. respectively. encoded within AVPs. 4. The receiver could not process the request. An example is a message set used to terminate a session.RFC 3588 Diameter Based Protocol September 2003 The following is a definition of a fictitious command code: Example-Request ::= < { * { * [ 3. authorization. Calhoun. known as redirect. PXY > User-Name } Origin-Host } AVP Diameter Command Naming Conventions Diameter command names typically includes one or more English words followed by the verb Request or Answer. such as authorizing a user or terminating a session.3. accounting.
server. indicates whether support of the AVP is required. The 'M' Bit. AVP Header The The fields in the AVP header MUST be sent in network byte order.RFC 3588 Diameter Based Protocol September 2003 Each AVP of type OctetString MUST be padded to align on a 32-bit boundary. The length of the padding is not reflected in the AVP Length field. and an unrecognized bit SHOULD be considered an error. The 'r' (reserved) bits are unused and SHOULD be set to 0. AVP numbers 1 through 255 are reserved for backward compatibility with RADIUS. Standards Track [Page 39] . +-+-+-+-+-+-+-+-+ AVP Code The AVP Code. Calhoun. known as the Mandatory bit. or translation agent and either the AVP or its value is unrecognized. the message MUST be rejected. AVP Flags The AVP Flags field informs the receiver how each attribute must be handled. combined with the Vendor-Id field. 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 . identifies the attribute uniquely. A number of zerovalued bytes are added to the end of the AVP Data field till a word boundary is reached. which are allocated by IANA (see Section 11. Diameter Relay and redirect agents MUST NOT reject messages with unrecognized AVPs. The 'P' bit indicates the need for encryption for end-to-end security. while other AVP types align naturally.. If an AVP with the 'M' bit set is received by a Diameter client. without setting the Vendor-Id field. Note that subsequent Diameter applications MAY define additional bits within the AVP Header. AVP numbers 256 and above are used for Diameter.1.1).. proxy. 4. et al.
the implementation may resend the message without the AVP. 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. or per realm basis that would allow/prevent particular Mandatory AVPs to be sent. In order to preserve interoperability. Standards Track [Page 40] . Unless otherwise noted. AVPs with the 'M' bit cleared are informational only and a receiver that receives a message with such an AVP that is not supported. AVP Length. The 'V' bit. et al. MAY simply ignore the AVP. the message SHOULD be rejected. and indicates the number of octets in this AVP including the AVP Code. 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. When set the AVP Code belongs to the specific vendor code address space. AVPs will have the following default AVP Flags field settings: The 'M' bit MUST be set. AVP Flags. Calhoun. indicates whether the optional Vendor-ID field is present in the AVP header. Vendor-ID field (if present) and the AVP data. 2) A configuration option may be provided on a system wide. Thus an administrator could change the configuration to avoid interoperability problems. If a message is received with an invalid attribute length. known as the Vendor-Specific bit. AVP Length The AVP Length field is three octets. 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. or whose value is not supported. per peer. The 'V' bit MUST NOT be set.RFC 3588 Diameter Based Protocol September 2003 The 'M' bit MUST be set according to the rules defined for the AVP containing it. possibly inserting additional standard AVPs instead.
The AVP Length field MUST be set to 16 (20 if the 'V' bit is enabled).1. 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. The optional four-octet Vendor-ID field contains the IANA assigned "SMI Network Management Private Enterprise Codes" [ASSIGNNO] value. in network byte order. et al.2. Integer64 64 bit signed value. nor with future IETF applications. as managed by the IANA. The format and length of the Data field is determined by the AVP Code and AVP Length fields. OctetString The data contains arbitrary data of variable length. Calhoun. a new version of this RFC must be created.1. Since the absence of the vendor ID field implies that the AVP in question is not vendor specific. Integer32 32 bit signed value. guaranteeing that they will not collide with any other vendor's vendor-specific AVP(s). 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. Any vendor wishing to implement a vendor-specific Diameter AVP MUST use their own Vendor-ID along with their privately managed AVP address space. This field is only present if the respective bit-flag is enabled. Unless otherwise noted. implementations MUST NOT use the zero (0) vendor ID. in network byte order. Vendor-ID The Vendor-ID field is present if the 'V' bit is set in the AVP Flags field. Standards Track [Page 41] . encoded in network byte order. Basic AVP Data Formats The Data field is zero or more octets and contains information specific to the Attribute. The AVP Length field MUST be set to 12 (16 if the 'V' bit is enabled). 4.RFC 3588 Diameter Based Protocol September 2003 4. the AVP Length field MUST be set to at least 8 (12 if the 'V' bit is enabled). A vendor ID value of zero (0) corresponds to the IETF adopted AVP values. Optional Header Elements The AVP Header contains one optional field. In the event that a new Basic AVP Data Format is needed.
The below AVP Derived Data Formats are commonly used by applications. The first two octets of the Address Calhoun. The 32-bit value is transmitted in network byte order. Address The Address format is derived from the OctetString AVP Base Format. Float32 This represents floating point values of single precision as described by [FLOATPOINT]. The AVP Length field MUST be set to 12 (16 if the 'V' bit is enabled). et al. Float64 This represents floating point values of double precision as described by [FLOATPOINT]. The AVP Length field MUST be set to 16 (20 if the 'V' bit is enabled). An application that defines new AVP Derived Data Formats MUST include them in a section entitled "AVP Derived Data Formats".in the order in which they are specified including their headers and padding. Each new definition must be either defined or listed with a reference to the RFC that defines the format. Grouped The Data field is specified as a sequence of AVPs.3. in network byte order. Each of these AVPs follows . The AVP Length field MUST be set to 12 (16 if the 'V' bit is enabled). applications may define data formats derived from the Basic AVP Data Formats. for example a 32-bit (IPv4) [IPV4] or 128-bit (IPv6) [IPV6] address. including their headers and padding. The 64-bit value is transmitted in network byte order. in network byte order. The AVP Length field MUST be set to 16 (20 if the 'V' bit is enabled). most significant octet first. Standards Track [Page 42] . It is a discriminated union. Derived AVP Data Formats In addition to using the Basic AVP Data Formats. Unsigned64 64 bit unsigned value. representing. using the same format as the definitions below.RFC 3588 Diameter Based Protocol September 2003 Unsigned32 32 bit unsigned value. The AVP Length field is set to 8 (12 if the 'V' bit is enabled) plus the total length of all included AVPs. 4. Thus the AVP length field of an AVP of type Grouped is always a multiple of 4.
This represents the number of seconds since 0h on 1 January 1900 with respect to the Coordinated Universal Time (UTC). thus the length of an UTF8String in octets may be different from the number of characters encoded. For information encoded in 7-bit US-ASCII. MAY be provided. Calhoun. Time The Time format is derived from the OctetString AVP Base Format. encoded as an OctetString using the UTF-8 [UFT8] transformation format described in RFC 2279. the UTF-8 charset is identical to the US-ASCII charset. Standards Track [Page 43] .RFC 3588 Diameter Based Protocol September 2003 AVP represents the AddressType. 7 February 2036 the time value will overflow. The NTP Timestamp format is defined in chapter 3 of [SNTP]. an alternative means of entry and display. such as hexadecimal. The use of control codes SHOULD be avoided. The AddressType is used to discriminate the content and format of the remaining octets. implementations MUST be prepared to encounter any code point from 0x00000001 to 0x7fffffff. On 6h 28m 16s UTC. This is a human readable string represented using the ISO/IEC IS 10646-1 character set. Since additional code points are added by amendments to the 10646 standard from time to time. For code points not directly supported by user interface hardware or software. UTF-8 may require multiple bytes to represent a single character / code point. in the same format as the first four bytes are in the NTP timestamp format. UTF8String The UTF8String format is derived from the OctetString AVP Base Format. The string MUST contain four octets. et al. The use of leading or trailing white space SHOULD be avoided. 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 control code sequence CR LF SHOULD be used. SNTP [SNTP] describes a procedure to extend the time to 2104. Note that the AVP Length field of an UTF8String is measured in octets. not characters. When it is necessary to represent a new line. This procedure MUST be supported by all DIAMETER nodes. which contains an Address Family defined in [IANAADFAM].
transport . . DiameterURI The DiameterURI MUST follow the Uniform Resource Identifiers (URI) syntax [URI] rules specified below: "aaa://" FQDN [ port ] [ transport ] [ protocol ] . . = ". = Fully Qualified Host Name = ":" 1*DIGIT One of the ports used to listen for incoming connections. the default SCTP [SCTP] protocol is assumed. If multiple Diameter nodes run on the same host. and used as the only DiameterIdentity for that node. The contents of the string MUST be the FQDN of the Diameter node. the default Diameter port (3868) is assumed. . . Standards Track [Page 44] . If absent. whatever the connection it is sent on. . Transport security used FQDN port . If absent. each Diameter node MUST be assigned a unique DiameterIdentity. et al. Calhoun. UDP MUST NOT be used when the aaa-protocol field is set to diameter. . DiameterIdentity = FQDN DiameterIdentity value is used to uniquely identify a Diameter node for purposes of duplicate connection and routing loop detection. . If a Diameter node can be identified by several FQDNs. No transport security "aaas://" FQDN [ port ] [ transport ] [ protocol ] .RFC 3588 Diameter Based Protocol September 2003 DiameterIdentity The DiameterIdentity format is derived from the OctetString AVP Base Format. a single FQDN should be picked at startup.transport=" transport-protocol One of the transports used to listen for incoming connections. . .
It uses the ASCII charset. the packet is dropped if the evaluated was a permit.RFC 3588 Diameter Based Protocol September 2003 transport-protocol = ( "tcp" / "sctp" / "udp" ) protocol = ".example.example.com:6666.com.transport=tcp aaa://host.protocol=diameter aaa://host.example.protocol=" aaa-protocol . et al.protocol=diameter aaa://host. (in or out) (possibly masked) (lists or ranges) the appropriate direction are evaluated in order.com:6666. the default AAA protocol . IPFilterRule The IPFilterRule format is derived from the OctetString AVP Base Format. Packets may be filtered based on the following information that is associated with it: Direction Source and destination IP address Protocol Source and destination port TCP flags IP fragment flag IP options ICMP types Rules for the first evaluated last rule a deny. If no rule matches.protocol=radius Enumerated Enumerated is derived from the Integer32 AVP Base Format.transport=udp. If absent. aaa-protocol = ( "diameter" / "radius" / "tacacs+" ) The following are examples of valid Diameter host identities: aaa://host. with matched rule terminating the evaluation. Each packet is once.example.transport=tcp aaa://host. The definition contains a list of valid values and their interpretation and is described in the Diameter application introducing the AVP.com:6666. is diameter.protocol=diameter aaa://host. Standards Track [Page 45] .com.com:1813.example. and passed if the last rule was Calhoun.transport=tcp.example.
dir proto src and dst Calhoun. ipno/bits An IP number as above with a mask width of the form 1. The "ip" keyword means any protocol will match. the bits part can be set to zero. The bit width MUST be valid for the IP version and the IP number MUST NOT have bits set beyond the mask.2.Drop packets that match the rule.0 to 1.0.255 will match. et al. Only this exact IP number will match the rule.3. the same IP version must be present in the packet that was used in describing the IP address.0/0 or the IPv6 equivalent.RFC 3588 Diameter Based Protocol September 2003 IPFilterRule filters MUST follow the format: action dir proto from src to dst [options] action permit . "out" is to the terminal.2. causing all other addresses to be matched instead. This does not affect the selection of port numbers. In this case. deny .Allow packets that match the rule. The keyword "assigned" is the address or set of addresses assigned to the terminal.3. <address/mask> [ports] The <address/mask> may be specified as: ipno An IPv4 or IPv6 number in dottedquad or canonical IPv6 form. An IP protocol specified by number. 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 (!). To test for a particular IP version.0. Standards Track [Page 46] . The keyword "any" is 0.3. "in" is from the terminal.2. For IPv4. all IP numbers from 1.4/24. For a match to occur.
ports[. The absence of a particular option may be denoted with a '!'. frag may not be used in conjunction with either tcpflags or TCP/UDP port specifications. sack (selective ack). window (tcp window advertisement). 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. ts (rfc1323 timestamp) and cc (rfc1644 t/tcp connection count). supported IP options are: The ssrr (strict source route). Fragmented packets that have a non-zero offset (i. optional ports may be specified as: {port/port-port}[..RFC 3588 Diameter Based Protocol September 2003 With the TCP. supported TCP options are: The mss (maximum segment size).]] The '-' notation specifies a range of ports (including boundaries). The absence of a particular option may be denoted with a '!'. Calhoun.e.. ipoptions spec Match if the IP header contains the comma separated list of options specified in spec. established TCP packets only. or ACK bits set. not the first fragment) will never match a rule that has one or more port specifications. lsrr (loose source route). UDP and SCTP protocols. et al.. rr (record packet route) and ts (timestamp).. Standards Track [Page 47] . setup Match packets that have the RST TCP packets only. Match packets that have the SYN bit set but no ACK bit. tcpoptions spec Match if the TCP header contains the comma separated list of options specified in spec.
RFC 3588 Diameter Based Protocol September 2003 tcpflags spec TCP packets only. The supported TCP flags are: fin. timestamp request (13). time-to-live exceeded (11). An access device that is unable to interpret or apply a permit rule MAY apply a more restrictive rule. and the ipfw. router solicitation (10). information request (15). redirect (5). An access device that is unable to interpret or apply a deny rule MUST terminate the session. destination unreachable (3). There is one kind of packet that the access device MUST always discard. ack and urg. A rule that contains a tcpflags specification can never match a fragmented packet that has a non-zero offset. rst. An access device MAY apply deny rules of its own before the supplied rules. to try to circumvent firewalls. See the frag option for details on matching fragmented packets.c code may provide a useful base for implementations. address mask request (17) and address mask reply (18). psh. et al. syn. IP header bad (12). router advertisement (9). Standards Track [Page 48] . Calhoun. The rule syntax is a modified subset of ipfw(8) from FreeBSD. Match if the TCP header contains the comma separated list of flags specified in spec. The supported ICMP types are: echo reply (0). source quench (4). but it only has one use. Match if the ICMP type is in the list types. information reply (16). This is a valid packet. The list may be specified as any combination of ranges or individual types separated by commas. The absence of a particular flag may be denoted with a '!'. for example to protect the access device owner's infrastructure. timestamp reply (14). echo request (8). icmptypes types ICMP packets only. that is an IP fragment with a fragment offset of one. Both the numeric values and the symbolic values listed below can be used.
Meter traffic. proto The format is as described under IPFilterRule. QoSFilterRule filters MUST follow the format: action dir proto from src to dst [options] tag . the packet is treated as best effort. as defined in Section 4.4. to nest them. The metering options MUST be included. If no rule matches. AVPs within an AVP of type Grouped have the same padding requirements as non-Grouped AVPs.' This implies that the Data field is actually a sequence of AVPs. Each packet is evaluated once. Standards Track [Page 49] . It uses the ASCII charset. The DSCP option MUST be included.RFC 3588 Diameter Based Protocol September 2003 QoSFilterRule The QosFilterRule format is derived from the OctetString AVP Base Format. with the first matched rule terminating the evaluation. et al. 4. that is. Packets may be marked or metered based on the following information that is associated with it: Direction Source and destination IP address Protocol Source and destination port DSCP values (in or out) (possibly masked) (lists or ranges) (no mask or range) Rules for the appropriate direction are evaluated in order. Calhoun. meter dir The format is as described under IPFilterRule. Grouped AVP Values The Diameter protocol allows AVP values of type 'Grouped. An access device that is unable to interpret or apply a QoS rule SHOULD NOT terminate the session. . src and dst The format is as described under IPFilterRule.Mark packet with a specific DSCP [DIFFSERV]. It is possible to include an AVP with a Grouped type within a Grouped type.
Standards Track [Page 50] . If absent. Further.com". Origin-Host = "example. defined in the base or extended Diameter . Every Grouped AVP defined MUST include a corresponding grammar. The name has to be the name of an AVP.1. the Grouped AVP itself MUST also include the 'M' bit set. grouped-avp-def name-fmt name = name "::=" avp = ALPHA *(ALPHA / DIGIT / "-") = name-fmt . using ABNF [ABNF] (with modifications).3). 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.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. avp header avpcode vendor 4. The Grouped Data field has the following ABNF grammar: Example-AVP ::= < { 1*{ *[ AVP Header: 999999 > Origin-Host } Session-Id } AVP ] An Example-AVP with Grouped Data follows. used.4. if any of the AVPs encapsulated within a Grouped AVP has the 'M' (mandatory) bit set. specifications. et al. the default value of zero is . . as defined below. In this case: Calhoun. The Origin-Host AVP is required (Section 6. The AVP Code assigned to the Grouped AVP = 1*DIGIT . . The Vendor-ID assigned to the Grouped AVP. = header [ *fixed] [ *required] [ *optional] [ *fixed] = "<" "AVP-Header:" avpcode [vendor] ">" = 1*DIGIT .
893. et al.com:33054. Here there are two: Session-Id = "grump. Also note that AVPs may be present in the Grouped AVP value which the receiver cannot interpret (here. The encoding example illustrates how padding is used and how length fields are calculated.23561.example.RFC 3588 Diameter Based Protocol September 2003 One or more Session-Ids must follow. Calhoun. the Recover-Policy and Futuristic-Acct-Record AVPs).except by Diameter implementations which support the same set of AVPs.com:33041.23432.2358.example.0AF3B81" Session-Id = "grump. nor (likely) at the time when the example instance of this AVP is interpreted .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. Standards Track [Page 51] .
+-------+-------+-------+-------+-------+-------+-------+-------+ | 'A' | 'F' | '3' | 'B' | '8' | '1' |Padding|Padding| +-------+-------+-------+-------+-------+-------+-------+-------+ | Session-Id AVP Header (AVP Code = 263). Length = 223 | +-------+-------+-------+-------+-------+-------+-------+-------+ | 0x21 | 0x63 | 0xbc | 0x1d | 0x0a | 0xd8 | 0x23 | 0x71 | +-------+-------+-------+-------+-------+-------+-------+-------+ . Length = 137| +-------+-------+-------+-------+-------+-------+-------+-------+ | 0xfe | 0x19 | 0xda | 0x58 | 0x02 | 0xac | 0xd9 | 0x8b | +-------+-------+-------+-------+-------+-------+-------+-------+ . . et al. Length = 19 | +-------+-------+-------+-------+-------+-------+-------+-------+ | 'e' | 'x' | 'a' | 'm' | 'p' | 'l' | 'e' | '. . . Length = 50 | 'g' | 'r' | 'u' | 'm' | +-------+-------+-------+-------+-------+-------+-------+-------+ . Length = 51 | +-------+-------+-------+-------+-------+-------+-------+-------+ | 'g' | 'r' | 'u' | 'm' | 'p' | '. +-------+-------+-------+-------+-------+-------+-------+-------+ | '0' | 'A' | 'F' | '3' | 'B' | '8' | '2' |Padding| +-------+-------+-------+-------+-------+-------+-------+-------+ | Recovery-Policy Header (AVP Code = 8341). .' | +-------+-------+-------+-------+-------+-------+-------+-------+ | 'c' | 'o' | 'm' |Padding| Session-Id AVP Header | +-------+-------+-------+-------+-------+-------+-------+-------+ | (AVP Code = 263). .RFC 3588 Diameter Based Protocol September 2003 This AVP would be encoded as follows: 0 1 2 3 4 5 6 7 +-------+-------+-------+-------+-------+-------+-------+-------+ | Example AVP Header (AVP Code = 999999). Length = 468 | +-------+-------+-------+-------+-------+-------+-------+-------+ | Origin-Host AVP Header (AVP Code = 264). +-------+-------+-------+-------+-------+-------+-------+-------+ | 0x2f | 0xd7 | 0x96 | 0x6b | 0x8c | 0x7f | 0x92 |Padding| +-------+-------+-------+-------+-------+-------+-------+-------+ | Futuristic-Acct-Record Header (AVP Code = 15930). . . Standards Track [Page 52] . . +-------+-------+-------+-------+-------+-------+-------+-------+ | 0x41 |Padding|Padding|Padding| +-------+-------+-------+-------+ 0 8 16 24 32 64 72 80 104 112 120 320 328 336 464 Calhoun.' | 'e' | 'x' | +-------+-------+-------+-------+-------+-------+-------+-------+ .
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. Standards Track [Page 53] .RFC 3588 Diameter Based Protocol September 2003 4. a "P" in the "MAY" column means that if a message containing that AVP is to be sent via a Diameter agent (proxy. types. Similarly. Diameter Base Protocol AVPs The following table describes the Diameter AVPs defined in the base protocol. Due to space constraints. "Encr" (Encryption) means that if a message containing that AVP is to be sent via a Diameter agent (proxy. et al. Calhoun. possible flag values and whether the AVP MAY be encrypted.5. for the originator of a Diameter message. 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. For the originator of a Diameter message. their AVP Code values. the short form DiamIdent is used to represent DiameterIdentity.
21 Time | M | P | | V | N | Experimental297 7.6 Grouped | M | P | | V | N | Result | | | | | | -----------------------------------------|----+-----+----+-----|----| Calhoun.3 Unsigned32 | M | P | | V | Y | Record-Number | | | | | | Accounting480 9.1 Enumerated | M | P | | V | Y | Record-Type | | | | | | Accounting44 9.8 Unsigned32 | M | P | | V | N | Application-Id | | | | | | Auth-Request274 8.8. Standards Track [Page 54] .294 7.9 Unsigned32 | M | P | | V | N | Application-Id | | | | | | Auth258 6.2 Unsigned32 | M | P | | V | Y | Interim-Interval | | | | | | Accounting483 22.214.171.124 Unsigned32 | M | P | | V | N | Period | | | | | | Auth-Session277 8.M | N | Host | | | | | | Event-Timestamp 55 8.3 Enumerated | M | P | | V | N | E2E-Sequence AVP 300 6.8.20 OctetString| M | P | | V | Y | Destination-Host 293 6.6 DiamIdent | M | P | | V | N | Realm | | | | | | Disconnect-Cause 273 5.15 Grouped | M | P | | V | Y | Error-Message 281 7. et al.9 Unsigned32 | M | P | | V | N | Lifetime | | | | | | Auth-Grace276 8.5 DiamIdent | M | P | | V | N | Destination283 6.4 DiamIdent | | P | | V.8.11 Enumerated | M | P | | V | N | State | | | | | | Re-Auth-Request.285 8.3 UTF8String | | P | | V.7 Enumerated | M | P | | V | N | Type | | | | | | Authorization291 188.8.131.52 UTF8String | M | P | | V | Y | Multi-Session-Id | | | | | | Accounting485 9.8.12 Enumerated | M | P | | V | N | Type | | | | | | Class 25 8.M | N | Error-Reporting.7 Enumerated | M | P | | V | Y | Realtime-Required | | | | | | Acct50 9.4 OctetString| M | P | | V | Y | Session-Id | | | | | | Accounting287 9.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| -----------------------------------------|----+-----+----+-----|----| Acct85 9.6 Unsigned64 | M | P | | V | Y | Sub-Session-Id | | | | | | Acct259 6.
7.1 DiamIdent | M | | | P.3 DiamIdent | M | | | P.17 Unsigned32 | M | P | | V | Y | Session-Server.4 OctetString| M | | | P.7 UTF8String | | | |P.260 6.5 Grouped | M | P | | V | N | Firmware267 5.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| -----------------------------------------|----+-----+----+-----|----| Experimental298 7.16 Unsigned32 | M | P | | V | N | Product-Name 269 5.7.8 UTF8String | M | P | | V | Y | Session-Timeout 27 8.12 DiamURI | M | P | | V | N | Redirect-Host261 6.M| N | Revision | | | | | | Host-IP-Address 257 5.1 Unsigned32 | M | P | | V | N | Route-Record 282 6.13 Enumerated | M | P | | V | N | Usage | | | | | | Redirect-Max262 6.6 Unsigned32 | M | P | | V | N | Vendor-Id | | | | | | Termination295 8.V.2 Grouped | M | | | P.V | N | Proxy-State 33 6.V | N | Proxy-Info 284 6.4 Unsigned32 | | | |P.13 Unsigned32 | M | P | | V | N | Session-Binding 270 8.3.V.14 Unsigned32 | M | P | | V | N | Cache-Time | | | | | | Result-Code 268 7.18 Enumerated | M | P | | V | Y | Failover | | | | | | Supported265 5.4 DiamIdent | M | P | | V | N | Origin-State-Id 278 8.14 UTF8String | M | P | | V | Y | Vendor-Id 266 5. et al.7 Unsigned32 | M | P | | V | N | Result-Code | | | | | | Failed-AVP 279 7.271 8.11 Grouped | M | P | | V | N | Application-Id | | | | | | -----------------------------------------|----+-----+----+-----|----| Calhoun.M| N | Proxy-Host 280 6.3.5 Address | M | P | | V | N | Inband-Security | M | P | | V | N | -Id 299 6.V | N | Redirect-Host 292 18.104.22.168 Unsigned32 | M | P | | V | Y | Time-Out | | | | | | Origin-Host 264 6.V | N | Session-Id 263 8.3. Standards Track [Page 55] .15 Enumerated | M | P | | V | N | Cause | | | | | | User-Name 1 8.3.3 DiamIdent | M | P | | V | N | Origin-Realm 296 6.3 Unsigned32 | M | P | | V | N | Vendor-Specific.10 Unsigned32 | | | | | | Multi-Round272 8.7.
all messages for a realm are sent to the primary peer. Peer Connections Although a Diameter node may have many possible peers that it is able to communicate with.RFC 3588 Diameter Based Protocol September 2003 5. but failover procedures are invoked. which could occur for various reasons. known as the primary and secondary peers. When an active peer is moved to this mode. a node MAY have additional connections. and assume the role of either primary or secondary. When a peer is deemed suspect.1. if it is deemed necessary. Note that a given peer MAY act as a primary for a given realm. 2. At a minimum. There are two ways that a peer is removed from the suspect peer list: 1. any pending requests are sent to the secondary peer.2. The peer is moved to the closed state. Standards Track [Page 56] . Diameter Peer Discovery Allowing for dynamic Diameter agent discovery will make it possible for simpler and more robust deployment of Diameter services. including not receiving a DWA within an allotted timeframe. causing the transport connection to be shutdown. These are based Calhoun. et al. it may not be economical to have an established connection to all of them. The peer is no longer reachable. Three watchdog messages are exchanged with accepted round trip times. However. an alternate peer SHOULD replace the deleted peer. 5. Typically. but in the event that failover procedures are invoked. 5. a Diameter node SHOULD have an established connection with two peers per realm. Of course. while acting as a secondary for another realm. Diameter Peers This section describes how Diameter nodes establish connections and communicate with peers. In the event the peer being removed is either the primary or secondary. the following mechanisms are described. additional connections SHOULD be established to ensure that the necessary number of active connections exists. and the connection to the peer is considered stabilized. In order to promote interoperable implementations of Diameter peer discovery. no new requests should be forwarded to the peer. implementations are free to load balance requests between a set of peers.
The first is when a Diameter client needs to discover a first-hop Diameter agent. This specification defines D2T for TCP and D2S for SCTP. The Diameter implementation has to know in advance which realm to look for a Diameter agent in. The Diameter service template [TEMPLATE] is included in Appendix A. there will be multiple NAPTR records. It is recommended that SLPv2 security be deployed (this requires distributing keys to SLPv2 agents).RFC 3588 Diameter Based Protocol September 2003 on existing IETF standards. while the latter two options (SRVLOC and DNS) MAY be supported. 3. Standards Track [Page 57] . The second case is when a Diameter agent needs to discover another agent . If the server supports multiple transport protocols. for example. the client Calhoun. The Diameter implementation performs a NAPTR query for a server in a particular realm. each with a different service value. 2. where x is a letter that corresponds to a transport protocol supported by the domain. We also establish an IANA registry for NAPTR service name to transport protocol mappings.1 The services relevant for the task of transport protocol selection are those with NAPTR service fields with values "AAA+D2x". There are two cases where Diameter peer discovery may be performed. The first option (manual configuration) MUST be supported by all DIAMETER nodes. SLPv2 is discussed further in Appendix A. This could be deduced. to the SRV record for contacting a server with the specific transport protocol in the NAPTR services field. As per RFC 2915 [NAPTR]. This is discussed further in Appendix A. The Diameter implementation consults its list of static (manually) configured Diameter agent locations. These NAPTR records provide a mapping from a domain. The Diameter implementation uses SLPv2 [SLP] to discover Diameter services. et al. the following 'search order' is recommended: 1. These will be used if they exist and respond. from the 'realm' in a NAI that a Diameter implementation needed to perform a Diameter operation on. which is the SRV record for that particular transport protocol. SLPv2 security SHOULD be used (requiring distribution of keys to SLPv2 agents) in order to ensure that discovered peers are authorized for their roles. In both cases. 3. The resource record will contain an empty regular expression and a replacement value.for further handling of a Diameter operation.
realm. A dynamically discovered peer causes an entry in the Peer Table (see Section 2. 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. a web server may have obtained a valid TLS certificate.6) to be created. Note that entries created via DNS MUST expire (or be refreshed) within the DNS TTL. for values of X that indicate transport protocols supported by the client. the requester queries for those address records for the destination address. 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. Alternatively this can be achieved by definition of OIDs within TLS or IKE certificates so as to signify Diameter Server authorization. or validation of DNS RRs via DNSSEC is not sufficient to conclude this.2 A client MUST discard any service fields that identify a resolution service whose value is not "D2X"._tcp'._sctp'. Standards Track [Page 58] .realm or '_diameter. several rules are defined. If the DNS server returns no address records. If no NAPTR records are found. AAAA RR's or other similar records. Authentication via IKE or TLS. and secured RRs may be included in the DNS. '_diameter. 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. as well as an SRV record for the server. the requestor gives up. by configuration of a Diameter Server CA. an attacker could modify the DNS records to contain replacement values in a different domain. Authorization can be achieved for example. or the result of an attack Also. For example. 3. 4. For the purposes of this specification. Otherwise. The domain suffixes in the NAPTR replacement field SHOULD match the domain of the original query. Address records include A RR's. but this does not imply that it is authorized to act as a Diameter Server. If a peer is discovered Calhoun.RFC 3588 Diameter Based Protocol September 2003 discards any records whose services fields are not applicable. If the server is using a site certificate. and the client could not validate that this was the desired behavior. the Diameter Peer MUST check to make sure that the discovered peers are authorized to act in its role. et al. chosen according to the requestor's network protocol capabilities.
Similarly.4) MUST be interpreted as having common applications with the peer. they MUST exchange the Capabilities Exchange messages. commands to its peers that have advertised application that defines the command. CERs received from unknown peers MAY be silently discarded. Note that receiving a CER or CEA from a peer advertising itself as a Relay (see Section 2. and SHOULD disconnect the transport layer connection.3. Standards Track [Page 59] . the lifetime of the peer entry is equal to the lifetime of the transport connection. A the supported applications in order to commands and/or AVPs are not unnecessarily 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. a routing table entry (see Section 2. the transport connection is closed. The CER and CEA messages MUST NOT be proxied. Since the CER/CEA messages cannot be proxied. a successful CEA MAY be returned. supported Diameter applications. In such instances. as specified in the peer state machine (see Section 5. and SHOULD disconnect the transport layer connection.7) for the peer's realm is created. security mechanisms. If the local policy permits receiving CERs from unknown hosts. Capabilities Exchange When two Diameter peers establish a transport connection. the 'E' bit is set in the answer Calhoun. or a CEA MAY be issued with the Result-Code AVP set to DIAMETER_UNKNOWN_PEER.) The receiver only issues support for the Diameter Diameter node MUST cache ensure that unrecognized sent to a peer. This message allows the discovery of a peer's identity and its capabilities (protocol version number.6). The routing table entry's expiration MUST match the peer's expiration value. all the pending transactions destined to the unknown peer can be discarded.RFC 3588 Diameter Based Protocol September 2003 outside of the local realm. 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. If a CER from an unknown peer is answered with a successful CEA. redirected or relayed. et al. In both cases. 5. etc. In case of a transport failure. 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.
REQ > Origin-Host } Origin-Realm } 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 ] Capabilities-Exchange-Answer The Capabilities-Exchange-Answer (CEA). et al.. Calhoun. 5.3. MAY only be forwarded to a host that has explicitly advertised support for the application (or has advertised the Relay Application Identifier). is sent in response to a CER message.RFC 3588 Diameter Based Protocol September 2003 message (see Section 7. the Capabilities-Exchange-Request message MUST contain one Host-IPAddress AVP for each potential IP address that MAY be locally used when transmitting Diameter messages. or a message with an application-specific command code. Standards Track [Page 60] . With the exception of the Capabilities-Exchange-Request message. is sent to exchange local capabilities. Diameter Header: 257.) with the Result-Code AVP set to DIAMETER_UNABLE_TO_DELIVER to inform the downstream to take action (e. a message of type Request that includes the Auth-Application-Id or Acct-Application-Id AVPs.1.3. When Diameter is run over SCTP [SCTP]. which allows for connections to span multiple interfaces and multiple IP addresses. re-routing request to an alternate peer). Message Format <CER> ::= < { { 1* { { { [ * [ * [ * [ * [ * [ [ * [ 5. indicated by the Command-Code set to 257 and the Command Flags' 'R' bit cleared.2.g. indicated by the CommandCode set to 257 and the Command Flags' 'R' bit set. Upon detection of a transport failure. Capabilities-Exchange-Request The Capabilities-Exchange-Request (CER). this message MUST NOT be sent to an alternate peer.
Product-Name (Section 5.4) AVPs MAY provide very useful debugging information.3. Message Format <CEA> ::= < { { { 1* { { { [ [ * [ * [ * [ * [ * [ * [ [ * [ 5. 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. this MAY be used in order to know which vendor specific attributes may be sent to the peer. Calhoun. It is also envisioned that the combination of the Vendor-Id.RFC 3588 Diameter Based Protocol September 2003 When Diameter is run over SCTP [SCTP]. A Vendor-Id value of zero in the CER or CEA messages is reserved and indicates that this field is ignored.3.4.6).3. which allows connections to span multiple interfaces. Diameter Header: 257 > Result-Code } Origin-Host } Origin-Realm } 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 ] 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. 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. Standards Track [Page 61] .7) and the Firmware-Revision (Section 5. et al.3.3.3. hence. multiple IP addresses. 5. In combination with the Supported-Vendor-Id AVP (Section 5.
the revision of the Diameter software module may be reported instead. as stated in Section 2. 5. 5. This AVP MUST ONLY be used in the CER and CEA messages. 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. and contains the vendor assigned name for the product. and will most likely assume that a connectivity problem occurred.6. The Product-Name AVP SHOULD remain constant across firmware revisions for the same product. a periodic connection request would not be welcomed. In these cases.3. In the event that the disconnect was a result of either a shortage of internal resources. and that the peer shouldn't reconnect unless it has a valid reason to do so (e.1. 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-IPAddress AVP for each address. the peer may periodically attempt to reconnect. its peer cannot know the reason for the disconnect.5. message to be forwarded). The Disconnect-Peer-Request message is used by a Diameter node to inform its peer of its intent to disconnect the transport layer.7. Product-Name AVP The Product-Name AVP (AVP Code 269) is of type UTF8String.. or that the peer has rebooted.g.4. or simply that the node in question has no intentions of forwarding any Diameter messages to the peer in the foreseeable future. 5. The Disconnection-Reason AVP contains the reason the Diameter node issued the Disconnect-Peer-Request message.3. Standards Track [Page 62] . 5. Disconnecting Peer connections When a Diameter node disconnects one of its transport connections. Upon receipt of the message. et al.RFC 3588 Diameter Based Protocol September 2003 For devices that do not have a firmware revision (general purpose computers running Diameter software modules.3. 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. 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. the Calhoun. for instance).
indicated by the Command-Code set to 282 and the Command Flags' 'R' bit cleared.4.4. 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. et al. Message Format <DPA> ::= < { { { [ * [ Diameter Header: 282 > Result-Code } Origin-Host } Origin-Realm } Error-Message ] Failed-AVP ] 5. which SHOULD contain an error if messages have recently been forwarded. The receiver of the Disconnect-Peer-Answer initiates the transport disconnect. Upon receipt of this message.1. which would otherwise cause a race condition.4. is sent as a response to the Disconnect-Peer-Request message.2. Upon detection of a transport failure. Disconnect-Cause AVP The Disconnect-Cause AVP (AVP Code 273) is of type Enumerated.RFC 3588 Diameter Based Protocol September 2003 Disconnect-Peer-Answer is returned. The following values are supported: Calhoun. 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. this message MUST NOT be sent to an alternate peer. 5. Disconnect-Peer-Request The Disconnect-Peer-Request (DPR). Disconnect-Peer-Answer The Disconnect-Peer-Answer (DPA). and are likely in flight. Message Format <DPR> ::= < { { { Diameter Header: 282. REQ > Origin-Host } Origin-Realm } Disconnect-Cause } 5. Standards Track [Page 63] . the transport connection is shutdown.3.
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.1. Transport Failure Detection Given the nature of the Diameter protocol. is sent as a response to the Device-Watchdog-Request message. and will provide better failover performance. Upon detection of a transport failure. since it does not expect any messages to be exchanged in the near future. this message MUST NOT be sent to an alternate peer. et al. resulting in unnecessary delays. 5. 5. is sent to a peer when no traffic has been exchanged between two peers (see Section 5.2. REQ > Origin-Host } Origin-Realm } Origin-State-Id ] 5. are used to proactively detect transport failures. The Device-Watchdog-Request and DeviceWatchdog-Answer messages. Message Format <DWR> ::= < { { [ Diameter Header: 280.5.5. Calhoun.5.RFC 3588 Diameter Based Protocol September 2003 REBOOTING 0 A scheduled reboot is imminent. 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. Device-Watchdog-Request The Device-Watchdog-Request (DWR). BUSY 1 The peer's internal resources are constrained. indicated by the Command-Code set to 280 and the Command Flags' 'R' bit cleared.5. and it has determined that the transport connection needs to be closed. Standards Track [Page 64] . indicated by the Command-Code set to 280 and the Command Flags' 'R' bit set. defined in this section.3). Device-Watchdog-Answer The Device-Watchdog-Answer (DWA).
The Hop-by-Hop Identifier field is used to match the answer with the queued request. it is necessary for all pending request messages to be forwarded to an alternate agent. Transport Failure Algorithm The transport failure algorithm is defined in [AAATRANS]. Calhoun. All Diameter implementations MUST support the algorithm defined in the specification in order to be compliant to the Diameter base protocol. Failover and Failback Procedures In the event that a transport failure is detected with a peer. This is commonly referred to as failover. When a transport failure is detected. The End-to-End Identifier field in the Diameter header along with the Origin-Host AVP MUST be used to identify duplicate messages. if possible all messages in the queue are sent to an alternate agent with the T flag set. et al. 5. and the unavailable peer is the message's final destination (see Destination-Host AVP). On booting a Diameter client or agent. It is important to note that multiple identical requests or answers MAY be received as a result of a failover.5. if possible.3. the corresponding request is removed from the queue.5. it is necessary for the node to maintain a pending message queue for a given peer. When an answer message is received. In order for a Diameter node to perform failover procedures. the T flag is also set on any records still remaining to be transmitted in non-volatile storage. Standards Track [Page 65] . 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.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 ] 5.4. 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.
All subsequent messages are sent on the surviving connection. Note in particular that [AAATRANS] requires the use of watchdog messages to probe connections. I-Open and R-Open. and reopen transport connections. I. a TLS handshake will begin when both ends are in the open state. DWR and DWA messages are to be used. failover. The stable states that a state machine may be in are Closed. messages can once again be forwarded to the peer. while the R. which is used to open. Standards Track [Page 66] . A CER message is always sent on the initiating connection immediately after the connection request is successfully completed. Calhoun. all further messages will be sent via TLS.RFC 3588 Diameter Based Protocol September 2003 As described in Section 2. Note that I-Open and R-Open are equivalent except for whether the initiator or responder transport connection is used for communication.is used to represent the responder (listening) connection. one of the two connections will shut down. 5. In the case of an election. as space requires.is used to represent the initiator (connecting) connection. For Diameter. Peer State Machine This section contains a finite state machine that MUST be observed by all Diameter implementations. Similarly. a connection request should be periodically attempted with the failed peer in order to re-establish the transport connection. the initiator connection will survive if the peer's Origin-Host is higher. probe. Multiple actions are separated by commas. all other states are intermediate. Once a connection has been successfully established. The state machine constrains only the behavior of a Diameter implementation as seen by Diameter peers through events on the wire. Each Diameter node MUST follow the state machine described below when communicating with each peer. and may continue on succeeding lines. state and next state may also span multiple lines. Note that the results of an election on one peer are guaranteed to be the inverse of the results on the other. The lack of a prefix indicates that the event or action is the same regardless of the connection on which the event occurred. This is commonly referred to as failback. If the handshake fails. The responder connection will survive if the Origin-Host of the local Diameter entity is higher than that of the peer. If the TLS handshake is successful. close. This state machine is closely coupled with the state machine described in [AAATRANS]. et al. as space requires.6. both ends move to the closed state. For TLS usage.1.
R-Open Process-CER. R-Snd-CEA Wait-Conn-Ack I-Rcv-Conn-Ack I-Rcv-Conn-Nack R-Conn-CER Timeout Wait-I-CEA I-Rcv-CEA R-Conn-CER I-Snd-CER Cleanup R-Accept. Process-CER Error Process-CEA R-Accept.Elect R-Snd-CEA R-Disc R-Reject Error I-Disc. et al. R-Disc Wait-I-CEA Closed Wait-Conn-Ack/ Elect Closed I-Open Wait-Returns I-Peer-Disc I-Rcv-Non-CEA Timeout Wait-Conn-Ack/ Elect I-Rcv-Conn-Ack I-Rcv-Conn-Nack R-Peer-Disc R-Conn-CER Timeout Wait-Returns Win-Election I-Peer-Disc I-Rcv-CEA R-Peer-Disc R-Conn-CER Timeout R-Open Send-Message R-Rcv-Message R-Rcv-DWR R-Rcv-DWA R-Conn-CER Stop R-Rcv-DPR Closed Closed Closed Wait-Returns R-Open Wait-Conn-Ack Wait-Conn-Ack/ Elect Closed R-Open R-Open I-Open Wait-I-CEA Wait-Returns Closed R-Open R-Open R-Open R-Open R-Open Closing Closed Calhoun. Standards Track [Page 67] . R-Snd-CEA R-Disc R-Disc R-Reject Error R-Snd-Message Process Process-DWR. R-Snd-DWA Process-DWA R-Reject R-Snd-DPR R-Snd-DPA. Process-CER. state event action next state ----------------------------------------------------------------Closed Start I-Snd-Conn-Req Wait-Conn-Ack R-Conn-CER R-Accept.RFC 3588 Diameter Based Protocol September 2003 Any implementation that produces equivalent results is considered compliant.R-Snd-CEA I-Disc. Elect I-Disc Error Error I-Snd-CER.
Standards Track [Page 68] . and the source port of an incoming connection is arbitrary. possible to know the identity of that peer until a CER is received from it. it is not. The logic that handles incoming connections SHOULD close and discard the connection if any message other than CER arrives. the identity of the connecting peer can be uniquely determined from Origin-Host. and the new connection and CER are passed to the state machine as an R-Conn-CER event. the Origin-Host that identifies the peer is used to locate the state machine associated with that peer. in the general case. or if an implementation-defined timeout occurs prior to receipt of CER. Incoming connections When a connection request is received from a Diameter peer. a Diameter peer must employ logic separate from the state machine to receive connection requests. For this reason. I-Snd-DWA Process-DWA R-Reject I-Snd-DPR I-Snd-DPA. it is described separately in this section rather than in the state machine above. Upon receipt of CER. separate from that of any individual state machine associated with a particular peer. This is because host and port determine the identity of a Diameter peer. Calhoun.1. accept them. and await CER. Because handling of incoming connections up to and including receipt of CER requires logic. et al. Once CER arrives on a new connection. I-Disc I-Disc I-Snd-CEA Process-CEA I-Disc R-Disc Error I-Disc R-Disc Closed R-Open R-Open I-Open I-Open I-Open I-Open I-Open Closing Closed Closed I-Open I-Open Closed Closed Closed Closed Closed 5.RFC 3588 Diameter Based Protocol September 2003 R-Peer-Disc R-Rcv-CER R-Rcv-CEA I-Open Send-Message I-Rcv-Message I-Rcv-DWR I-Rcv-DWA R-Conn-CER Stop I-Rcv-DPR I-Peer-Disc I-Rcv-CER I-Rcv-CEA Closing I-Rcv-DPA R-Rcv-DPA Timeout I-Peer-Disc R-Peer-Disc R-Disc R-Snd-CEA Process-CEA I-Snd-Message Process Process-DWR.6.
et al. and the local node was the winner. A message is to be sent. but would occur on one of two possible connections.g.2. A positive acknowledgement is received confirming that the transport connection is established. DPA. DWR or DWA was received. and the associated CER has arrived. since the actual event would be identical. CEA. R-Conn-CER Rcv-Conn-Ack Rcv-Conn-Nack Timeout Rcv-CER Rcv-CEA Rcv-Non-CEA Peer-Disc Rcv-DPR Rcv-DPA Win-Election Send-Message Rcv-Message Stop Calhoun. An acknowledgement is received stating that the transport connection has been established.. A negative acknowledgement was received stating that the transport connection was not established. An election was held. Standards Track [Page 69] . DPR. A CER message from the peer was received. Start The Diameter application has signaled that a connection should be initiated with the peer.6. we will ignore the -I and -R prefix. A message other than CEA from the peer was received. A DPR message from the peer was received. Events Transitions and actions in the automaton are caused by events. A disconnection indication from the peer was received. The Diameter application has signaled that a connection should be terminated (e. A CEA message from the peer was received. An application-defined timer has expired while waiting for some event. A DPA message from the peer was received.RFC 3588 Diameter Based Protocol September 2003 5. on system shutdown). A message other than CER. In this section.
6. et al. 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. The CER associated with the R-Conn-CER is processed.6. Local resources are freed. In this section we will ignore the I. A DPR message is sent to the peer. A DWA message is sent. The DWR message is serviced. The incoming connection associated with the R-Conn-CER is accepted as the responder connection. An election occurs (see Section 5.4 for more information). either politely or abortively. The transport layer connection is disconnected. Snd-Conn-Req Accept A transport connection is initiated with the peer.RFC 3588 Diameter Based Protocol September 2003 5. The incoming connection associated with the R-Conn-CER is disconnected. Standards Track [Page 70] . If necessary.3. A DWR message is sent. but would occur on one of two possible connections. in response to an error condition. A received CEA is processed. and any local resources are freed. A CER message is sent to the peer. A DPA message is sent to the peer. The transport layer connection is disconnected. and local resources are freed. since the actual action would be identical. the connection is shutdown. Reject Process-CER Snd-CER Snd-CEA Cleanup Error Process-CEA Snd-DPR Snd-DPA Disc Elect Snd-Message Snd-DWR Snd-DWA Process-DWR Calhoun. A CEA message is sent to the peer. A message is sent.and R-prefix.
but MUST NOT contain a Destination-Host AVP. 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. otherwise. Standards Track [Page 71] . 6. Any remaining octets are assumed to have value 0x80. If the local Diameter entity's Origin-Host is higher than the peer's. The DWA message is serviced.RFC 3588 Diameter Based Protocol September 2003 Process-DWA Process 5. but not to a specific server (such as the first request of a series of round-trips). Diameter Request Routing Overview A request is sent towards its final destination using a combination of the Destination-Realm and Destination-Host AVPs. a request that needs to be sent to a specific home server among those serving a given realm. - - The Destination-Host AVP is used as described above when the destination of the request is fixed. Calhoun. The responder compares the Origin-Host received in the CER sent by its peer with its own Origin-Host. 6.1. The Election Process The election is performed on the responder.4. et al. Diameter message processing This section describes how Diameter requests and answers are created and processed. a Win-Election event is issued locally. MUST contain a DestinationRealm AVP. a request that needs to be sent to a home server serving a specific realm.6. A message is serviced. then performing an octet-by-octet unsigned comparison with the first octet being most significant. MUST contain both the Destination-Realm and Destination-Host AVPs. 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. 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.
When a message is received. If none of the above is successful.. Otherwise.1. Note the processing rules contained in this section are intended to be used as general guidelines to Diameter developers. or other applicationspecific methods. Request messages that may be forwarded by Diameter agents (proxies. The Destination-Realm AVP MUST be present if the message is proxiable. This is known as Request Forwarding. If the message is intended for a Diameter peer with whom the local host is able to directly communicate. A message that MUST NOT be forwarded by Diameter agents (proxies.g. The value of the Destination-Realm AVP MAY be extracted from the User-Name AVP. Calhoun.RFC 3588 Diameter Based Protocol September 2003 - Server initiated messages that MUST be received by a specific Diameter client (e.6 are followed. If the message is destined for the local host. redirects or relays) MUST also contain an AcctApplication-Id AVP.7). which is known as Request Routing. the procedures listed in Section 6. 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. 4. the procedures listed in Section 6. an Auth-Application-Id AVP or a Vendor-SpecificApplication-Id AVP. an answer is returned with the Result-Code set to DIAMETER_UNABLE_TO_DELIVER. all Diameter nodes within the realm MUST be peers.1. 3.1.4 are followed. For routing of Diameter messages to work within an administrative domain. Standards Track [Page 72] . such as the Abort-SessionRequest message. et al.5 are followed. The procedures listed in Section 6.1. and still comply with the protocol specification. 2. the request is routed based on the Destination-Realm only (see Sections 6. redirects or relays) MUST not include the Destination-Realm in its ABNF. the message is processed in the following order: 1. with the E-bit set. Certain implementations MAY use different methods than the ones described here.6). access device). See Section 7 for more detail on error handling.
1. 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. A loop is detected if the server finds its own identity in a Route-Record AVP. 6. Originating a Request When creating a request. in addition to any other procedures described in the application definition for that specific request.220.127.116.11. an Auth-Application-Id or a VendorSpecific-Application-Id AVP must be included if the request is proxiable. Sending a Request - - 6.RFC 3588 Diameter Based Protocol September 2003 6.1. 6. the agent MUST answer with the Result-Code AVP set to DIAMETER_LOOP_DETECTED. 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.3. et al.2. When such an event occurs. When sending a request. originated either locally. Receiving Requests A relay or proxy agent MUST check for forwarding loops when receiving requests. Calhoun. Other actions to perform on the message based on the particular role the agent is playing are described in the following sections. an Acct-Application-Id AVP.1. 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. Standards Track [Page 73] .
Redirecting requests When a redirect agent receives a request whose routing entry is set to REDIRECT. or Both the Destination-Host and the Destination-Realm are not present. Calhoun.6.2 should be used to generate the corresponding answer. A Diameter message that may be forwarded by Diameter agents (proxies.RFC 3588 Diameter Based Protocol September 2003 - The Destination-Host AVP is not present.7). and MAY have a list of externally supported realms and applications. which is in the form of a Network Access Identifier (NAI). Diameter agents MAY have a list of locally supported realms and applications. The Diameter peer table contains all of the peers that the local node is able to directly communicate with. and include the Result-Code AVP to DIAMETER_REDIRECT_INDICATION. 6. et al.1.7. the message SHOULD be forwarded to the peer. 6.5. and the Diameter application is locally supported. Standards Track [Page 74] . the message is routed to the peer configured in the Realm Routing Table (see Section 2. it MUST reply with an answer message with the 'E' bit set. Request Routing Diameter request message routing is done via realms and applications.1.1. Request Forwarding Request forwarding is done using the Diameter Peer Table. redirects or relays) MUST include the target realm in the Destination-Realm AVP and one of the application identification AVPs Auth-Application-Id. When a request is received. The realm MAY be retrieved from the User-Name AVP. Acct-Application-Id or Vendor-SpecificApplication-Id. the Destination-Realm AVP contains a realm the server is configured to process locally. the rules in Section 6. 6. The realm portion of the NAI is inserted in the Destination-Realm AVP. Each of the servers associated with the routing entry are added in separate Redirect-Host AVP. - When a request is locally processed. When a request is received that includes a realm and/or application that is not locally supported. and the host encoded in the DestinationHost AVP is one that is present in the peer table. while maintaining the Hop-by-Hop Identifier in the header.
6. Relaying and Proxying Requests A relay or proxy agent MUST append a Route-Record AVP to all requests forwarded. Standards Track [Page 75] . Proxy-Info AVP has certain security implications and SHOULD contain an embedded HMAC with a node-local key. The source of the request is also saved.8. Alternatively. The message is then forwarded to the next hop. and the request is sent directly to it. which includes the IP address.com |------------->| example. Answer +-------------+ Figure 5: Diameter Redirect Agent The receiver of the answer message with the 'E' bit set. The Hop-by-Hop identifier in the request is saved. and the Result-Code AVP set to DIAMETER_REDIRECT_INDICATION uses the hop-byhop field in the Diameter header to identify the request in the pending message queue (see Section 5. et al. The AVP contains the identity of the peer the request was received from. one is created. command + 'E' bit 1. it MAY simply use local storage to store state information. 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.1.net | | Relay | | Diameter | | Agent |<-------------| Server | +-------------+ 4. port and protocol. and replaced with a locally unique value. The receiver of the answer message with the 'E' bit set selects exactly one of these hosts as the destination of the redirected message. Request | | Result-Code = joe@example. Calhoun. Request +-------------+ | example.com | | DIAMETER_REDIRECT_INDICATION + | | Redirect-Host AVP(s) | v +-------------+ 3. If no transport connection exists with the new agent.RFC 3588 Diameter Based Protocol September 2003 +------------------+ | Diameter | | Redirect Agent | +------------------+ ^ | 2. as identified in the Realm Routing Table. Multiple Redirect-Host AVPs are allowed.3) that is to be redirected.
2.net (Answer) example.net) (Origin-Realm=mno. et al. The 'P' bit is set to the same value as the one in the request. Any Proxy-Info AVPs in the request MUST be added to the answer message. - - - - - Calhoun. The same End-to-End identifier in the request is used in the answer. it MUST be included in the answer.com (Origin-Host=hms.net) (Origin-Host=nas. If the Session-Id is present in the request.example.example. The local host's identity is encoded in the Origin-Host AVP.mno.example.com) (Route-Record=nas.net) +------+ ------> +------+ ------> +------+ | | (Request) | | (Request) | | | NAS +-------------------+ DRL +-------------------+ HMS | | | | | | | +------+ <-----+------+ <-----+------+ example. The Destination-Host and Destination-Realm AVPs MUST NOT be present in the answer message.net (Answer) example. (Origin-Host=nas.mno. Standards Track [Page 76] .com) (Origin-Realm=example. The Result-Code AVP is added with its value indicating success or failure. 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.net) (Origin-Realm=mno. in the same order they were present in the request.com) (Origin-Host=hms.com) Figure 6: Routing of Diameter messages 6.com) (Origin-Realm=example. Diameter Answer Processing When a request is locally processed.net) (Destination-Realm=example. the following procedures MUST be applied to create the associated answer.RFC 3588 Diameter Based Protocol September 2003 Figure 6 provides an example of message routing using the procedures listed in these sections.com) (DestinationRealm=example.
and MUST be present in all Diameter messages. The agent MUST then send the answer to the host that it received the original request from. Note that the Origin-Host AVP may resolve to more than one address as the Diameter peer may support more than one address. the agent MUST restore the original value of the Diameter header's Hopby-Hop Identifier field. Standards Track [Page 77] .2.3. It SHOULD ignore answers received that do not match a known Hop-by-Hop Identifier. 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.3) are also subjected to the above processing rules. 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. it MUST NOT modify the contents of the AVP. Relaying and Proxying Answers If the answer is for a request which was proxied or relayed. 6. Origin-Host AVP The Origin-Host AVP (AVP Code 264) is of type DiameterIdentity. Any additional local errors detected SHOULD be logged. Calhoun.2.RFC 3588 Diameter Based Protocol September 2003 Note that the error messages (see Section 7. The corresponding message should be removed from the list of pending requests.1. This AVP identifies the endpoint that originated the Diameter message. 6. but not reflected in the Result-Code AVP. the AVP MUST be removed before the answer is forwarded.2. If the last Proxy-Info AVP in the message is targeted to the local Diameter server. If the agent receives an answer message with a Result-Code AVP indicating success. 6. If a relay or proxy agent receives an answer with a Result-Code AVP indicating a failure. The value of the Origin-Host AVP is guaranteed to be unique within a single host. Relay agents MUST NOT modify this AVP. and it wishes to modify the AVP to indicate an error. et al.
This AVP SHOULD be placed as close to the Diameter header as possible.10 6. and MUST NOT be present in Answer messages.7. 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 contains the Realm of the originator of any Diameter message and MUST be present in all messages. and therefore MUST NOT be protected by end-to-end security. 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). Routing AVPs The AVPs defined in this section are Diameter AVPs used for routing purposes. Calhoun. Destination-Realm AVP The Destination-Realm AVP (AVP Code 283) is of type DiameterIdentity.5. MAY be present in request messages. 6. 6. Diameter Clients insert the realm portion of the User-Name AVP. This AVP MUST be present in all unsolicited agent initiated messages. This AVP SHOULD be placed as close to the Diameter header as possible. This AVP SHOULD be placed as close to the Diameter header as possible. Origin-Realm AVP The Origin-Realm AVP (AVP Code 296) is of type DiameterIdentity. 6.4. 6.6. When present. Standards Track [Page 78] .RFC 3588 Diameter Based Protocol September 2003 This AVP SHOULD be placed as close to the Diameter header as possible. and contains the realm the message is to be routed to. Request messages whose ABNF does not list the Destination-Realm AVP as a mandatory AVP are inherently non-routable messages. These AVPs change as Diameter messages are processed by agents. Destination-Host AVP The Destination-Host AVP (AVP Code 293) is of type DiameterIdentity. The Destination-Realm AVP MUST NOT be present in Answer messages. the Destination-Realm AVP is used to perform message routing decisions. et al.
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. 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. et al. Calhoun.8. and MUST be treated as opaque data. Proxy-State AVP The Proxy-State AVP (AVP Code 33) is of type OctetString. This AVP contains the identity of the host that added the Proxy-Info AVP. Proxy-Info AVP The Grouped The Proxy-Info AVP (AVP Code 284) is of type Grouped. 6. Data field has the following ABNF grammar: Proxy-Info ::= < { { * [ 6.7.RFC 3588 Diameter Based Protocol September 2003 6. 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. and contains state local information. 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. Proxy-Host AVP AVP Header: 284 > Proxy-Host } Proxy-State } AVP ] The Proxy-Host AVP (AVP Code 280) is of type DiameterIdentity.7. 188.8.131.52).10.4). 6.7.1. 6.2. Route-Record AVP The Route-Record AVP (AVP Code 282) is of type DiameterIdentity. The Acct-Application-Id MUST also be present in all Accounting messages. 6. The identity added in this AVP MUST be the same as the one received in the Origin-Host of the Capabilities Exchange message.7. Exactly one of the AuthApplication-Id and Acct-Application-Id AVPs MAY be present. Standards Track [Page 79] .3.
Redirect-Host-Usage AVP The Redirect-Host-Usage AVP (AVP Code 261) is of type Enumerated. TLS 1 This node supports TLS security. the receiving Diameter node SHOULD forward the request directly to one of the hosts identified in these AVPs. Upon receiving the above. but there is ample room to add new security Ids. This is the default value. as defined by [TLS]. The server contained in the selected Redirect-Host AVP SHOULD be used for all messages pertaining to this session.RFC 3588 Diameter Based Protocol September 2003 Currently. Vendor-Specific-Application-Id AVP 6. Calhoun. This AVP MAY be present in answer messages whose 'E' bit is set and the Result-Code AVP is set to DIAMETER_REDIRECT_INDICATION. NO_INBAND_SECURITY 0 This peer does not support TLS. et al.12. if the AVP is omitted. the following values are supported. This AVP SHOULD be placed as close to the Diameter header as possible. This AVP MUST also be present as the first AVP in all experimental commands defined in the vendor-specific application.13. 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. 6. Exactly one of the Auth-Application-Id and Acct-Application-Id AVPs MAY be present. Standards Track [Page 80] . Redirect-Host AVP AVP Header: 260 > Vendor-Id ] Auth-Application-Id } Acct-Application-Id } 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. AVP Format <Vendor-Specific-Application-Id> ::= < 1* [ 0*1{ 0*1{ 6.11.
14. the Result-Code AVP is set to DIAMETER_REDIRECT_INDICATION and the Redirect-Host-Usage AVP set to a non-zero value. ALL_APPLICATION 4 All messages for the application requested MAY be sent to the host specified in the Redirect-Host AVP. Note that once a host created due to a redirect indication is no longer reachable. ALL_SESSION 1 All messages within the same session. This is the default value. as defined by the same value of the Session-ID AVP MAY be sent to the host specified in the Redirect-Host AVP. et al. Calhoun. This AVP MUST be present in answer messages whose 'E' bit is set. created as a result of the Redirect-Host. ALL_REALM 2 All messages destined for the realm requested MAY be sent to the host specified in the Redirect-Host AVP. Redirect-Max-Cache-Time AVP The Redirect-Max-Cache-Time AVP (AVP Code 262) is of type Unsigned32. Standards Track [Page 81] . 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 RedirectHost AVP. any associated peer and routing table entries MUST be deleted. This AVP contains the maximum number of seconds the peer and route table entries.RFC 3588 Diameter Based Protocol September 2003 When present. The following values are supported: DONT_CACHE 0 The host specified in the Redirect-Host AVP should not be cached. 6. 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_USER 6 All messages for the user requested MAY be sent to the host specified in the Redirect-Host AVP. will be cached. this AVP dictates how the routing entry resulting from the Redirect-Host is to be used.
each proxy or relay agent MAY take action on the message. When the message is received by Relay 2.. E2E-Sequence AVP The E2E-Sequence AVP (AVP Code 300) provides anti-replay protection for end to end messages and is of type grouped.g. et al. message routing error). Application errors.15. Error Handling There are two different types of errors in Diameter.g. Standards Track [Page 82] . Given that this error falls Calhoun. an answer message is returned with the 'E' bit set. protocol and application errors. and it detects that it cannot forward the request to the home server.RFC 3588 Diameter Based Protocol September 2003 6. Request +---------+ Link Broken +-------------------------->|Diameter |----///----+ | +---------------------| | v +------+--+ | 2. This AVP MUST be included in all messages which use end-to-end protection (e. generally occur due to a problem with a function specified in a Diameter application (e. 7. on the other hand. As the answer is sent back towards the originator of the request. Missing AVP). and MAY require per hop attention (e. It contains a random value (an OctetString with a nonce) and counter (an Integer). CMS signing or encryption).. 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.g. Result-Code AVP values that are used to report protocol errors MUST only be present in answer messages whose 'E' bit is set. 1. 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.. and the Result-Code AVP is set to the appropriate protocol error value. an answer message is returned with the 'E' bit set and the Result-Code AVP set to DIAMETER_UNABLE_TO_DELIVER. A protocol error is one that occurs at the base protocol level. When a request message is received that causes a protocol error. answer + 'E' set | Relay 2 | +--------+ |Diameter |<-+ (Unable to Forward) +---------+ |Diameter| | | | Home | | Relay 1 |--+ +---------+ | Server | +---------+ | 3. user authentication.
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. Answer +---------+ 3. causes an answer to be sent with the Result-Code AVP set to DIAMETER_AVP_UNSUPPORTED. In these cases. the Diameter node that sets the Result-Code AVP to indicate the error MUST add the AVPs. Request +---------+ 2. and adds the Result-Code AVP with the proper value. and given the error. 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. In case there are multiple errors. the Diameter node MUST report only the first error it encountered Calhoun. and therefore the message would be forwarded back to the originator of the request. Examples are: An unrecognized AVP is received with the 'M' bit (Mandatory bit) set. - - The Result-Code AVP describes the error that the Diameter node encountered in its processing. Standards Track [Page 83] . Request +---------+ | Access |------------>|Diameter |------------>|Diameter | | | | | | Home | | Device |<------------| Relay |<------------| Server | +---------+ 4. and creates an AVP with the AVP Code and other fields set as expected in the missing AVP. A command is received with an AVP that is omitted. Application errors do not require any proxy or relay agent involvement. the Diameter entity reporting the error clears the 'R' bit in the Command Flags. The created AVP is then added to the FailedAVP AVP.RFC 3588 Diameter Based Protocol September 2003 within the protocol error category. Relay 1 would take special action. with the Failed-AVP AVP containing the AVP causing the error. yet is mandatory according to the command's ABNF. et al. attempt to route the message through its alternate Relay 3. When application errors occur. There are certain Result-Code AVP application errors that require additional AVPs to be present in the answer. The receiver issues an answer with the Result-Code set to DIAMETER_MISSING_AVP. +---------+ 1.
all identified by the thousands digit in the decimal notation: 1xxx 2xxx 3xxx 4xxx 5xxx (Informational) (Success) (Protocol Errors) (Transient Failures) (Permanent Failure) A non-recognized class (one whose first digit is not defined in this section) MUST be handled as a permanent failure.RFC 3588 Diameter Based Protocol September 2003 (detected possibly in some implementation dependent order). DIAMETER_SUCCESS 2001 The Request was successfully completed.1.1. and a subsequent request needs to be issued in order for access to be granted.1. 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. Informational Errors that fall within this category are used to inform the requester that a request could not be satisfied.2. Standards Track [Page 84] .1.4). 7. The specific errors that can be described by this AVP are described in the following section. Success Errors that fall within the Success category are used to inform a peer that a request has been successfully completed. 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. 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. et al. and additional action is required on its part before access is granted. Calhoun. 7. 7. Diameter provides the following classes of errors. The Result-Code data field contains an IANA-managed 32-bit address space representing errors (see Section 11.
RFC 3588 Diameter Based Protocol September 2003 DIAMETER_LIMITED_SUCCESS 2002 When returned. This MUST be used when a Diameter node receives an experimental command that it does not understand. either because no host within the realm supporting the required application was available to process the request. The message MAY be sent to an alternate peer. but additional processing is required by the application in order to provide service to the user. Protocol Errors Errors that fall within the Protocol Error category SHOULD be treated on a per-hop basis. Calhoun.3. DIAMETER_REALM_NOT_SERVED 3003 The intended realm of the request is not recognized. DIAMETER_UNABLE_TO_DELIVER 3002 This error is given when Diameter can not deliver the message to the destination. a Diameter node SHOULD attempt to send the message to an alternate peer. DIAMETER_APPLICATION_UNSUPPORTED 3007 A request was sent for an application that is not supported. but the peer reporting the error has identified a configuration problem. Standards Track [Page 85] . DIAMETER_LOOP_DETECTED 3005 An agent detected a loop while trying to get the message to the intended recipient. the request was successfully completed. whose contact information has been added to the response. if it is possible. DIAMETER_TOO_BUSY 3004 When returned. When set. DIAMETER_COMMAND_UNSUPPORTED 3001 The Request contained a Command-Code that the receiver did not recognize or support. et al. the Redirect-Host AVP MUST be present. or because Destination-Host AVP was given without the associated Destination-Realm AVP. and Diameter proxies MAY attempt to correct the error. Note that these and only these errors MUST only be used in answer messages whose 'E' bit is set. if one is available. This error MUST only be used when a specific server is requested.1. and it cannot provide the requested service. 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. 7.
5. ELECTION_LOST 4003 The peer has determined that it has lost the election process and has therefore disconnected the transport connection.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. Standards Track [Page 86] . DIAMETER_AUTHENTICATION_REJECTED 4001 The authentication process for the user failed. 7. 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. DIAMETER_UNKNOWN_PEER 3010 A CER was received from an unknown peer. Further attempts MUST only be tried after prompting the user for a new password.1. et al. or that is inconsistent with the AVP's definition. Calhoun.4. 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. 7. 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. most likely due to an invalid password used by the user. DIAMETER_INVALID_AVP_BITS 3009 A request was received that included an AVP whose flag bits are set to an unrecognized value. or to a value that is inconsistent with the command code's definition.1. DIAMETER_UNKNOWN_SESSION_ID 5002 The request contained an unknown Session-Id. Permanent Failures Errors that fall within the permanent failures category are used to inform the peer that the request failed. but MAY be able to satisfy the request in the future. and should not be attempted again. A Diameter message with this error MUST contain one or more FailedAVP AVP containing the AVPs that caused the failure.
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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. 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.
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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:
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Message Format <answer-message> ::= < 0*1< { { { [ [ [ * [ Diameter Header: code, ERR [PXY] > 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 ResultCode 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.
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an AVP with the missing AVP code. 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. 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).3. Calhoun. and indicates whether a particular vendor-specific request was completed successfully or whether an error occurred.3) in this grouped AVP identifies the vendor responsible for the assignment of the result code which follows. The second only makes use of accounting. Experimental-Result AVP The Experimental-Result AVP (AVP Code 297) is of type Grouped. containing the entire AVP that could not be processed successfully.RFC 3588 Diameter Based Protocol September 2003 A Diameter message MAY contain one Failed-AVP AVP. and a zero filled payload of the minimum required length for the omitted AVP will be added. the missing vendor id. et al. AVP Format <Failed-AVP> ::= < AVP Header: 279 > 1* {AVP} 7. Diameter User Sessions Diameter can provide two different types of services to applications. 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. and can optionally make use of accounting.7. Standards Track [Page 90] . 7.6. The first involves authentication and authorization. 8. If the failure reason is omission of a required AVP. All Diameter answer messages defined in vendor-specific applications MUST include either one Result-Code AVP or one Experimental-Result AVP.
and it is willing to extend the authorization via a future request..RFC 3588 Diameter Based Protocol September 2003 When a service makes use of the authentication and/or authorization portion of an application. combined with the Auth-Grace-Period AVP. it MUST add the AuthorizationLifetime AVP to the answer message. which is used in subsequent messages (e. However. Note that if payment for services is expected by the serving realm from the user's home realm.. the Diameter client issues an auth request to its local server. Calhoun. Services provided past the expiration of the Authorization-Lifetime and Auth-Grace-Period AVPs are the responsibility of the access device. These are used to allow servers that maintain state information to free resources. When a Diameter server authorizes a user to use network resources for a finite amount of time. subsequent authorization. and a user requests access to the network. Note that the value NO_STATE_MAINTAINED MUST NOT be set in subsequent reauthorization requests and answers. et al. after which the server will release all state information related to the user's session. 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 access device MUST follow the server's directives. 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 Session-Id AVP is a means for the client and servers to correlate a Diameter message with a user session. Standards Track [Page 91] . the actual cost of services rendered is clearly outside the scope of the protocol. Of course. If the server accepts the hint. the base protocol does define a set of messages that is used to terminate user sessions. implies the maximum length of the session the home realm is willing to be fiscally responsible for. The Auth-Grace-Period AVP contains the number of seconds following the expiration of the Authorization-Lifetime.g. The auth request is defined in a service specific Diameter application (e.g. the Authorization-Lifetime AVP. The base protocol does not include any authorization request messages. since these are largely application-specific and are defined in a Diameter application document. NASREQ). An access device that does not expect to send a re-authorization or a session termination request to the server MAY include the AuthSession-State AVP with the value set to NO_STATE_MAINTAINED as a hint to the server. The request contains a Session-Id AVP. it cannot maintain state for the session. it agrees that since no session termination message will be received once service to the user is terminated. etc) relating to the user's session. accounting.
1.. representing the life cycle of Diameter sessions. Standards Track [Page 92] . MUST be returned to the originator of the message. The term Service-Specific below refers to a message defined in a Diameter application (e. Calhoun. Here again. Authorization Session State Machine This section contains a set of finite state machines. the other from a server perspective. the session termination messages are not used. Any event not listed in the state machines MUST be considered as an error condition. The second two state machines are used when the server does not maintain session state.RFC 3588 Diameter Based Protocol September 2003 When a service only makes use of the Accounting portion of the Diameter protocol. However. NASREQ). the event 'Failure to send X' means that the Diameter agent is unable to send command X to the desired destination. indicated by the value of the Auth-Session-State AVP (or its absence). any resources that were allocated for the particular session must be released.g. When a session is moved to the Idle state. one describes the session from a client perspective. There are four different authorization session state machines supported in the Diameter base protocol. et al. The event 'X successfully sent' is the complement of 'Failure to send X'. if applicable. The first two describe a session in which the server is maintaining session state. since a session is signaled as being terminated by issuing an accounting stop message. Mobile IPv4. This could be due to the peer being down. and which MUST be observed by all Diameter implementations that make use of the authentication and/or authorization portion of a Diameter application. even in combination with an application. 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. In the state table. the other from a server perspective. the Session-Id is still used to identify user sessions. 8. One describes the session from a client perspective. and an answer.
RFC 3588 Diameter Based Protocol September 2003 The following state machine is observed by a client when state is maintained on the server: CLIENT. Session-Timeout Expires on Access Device Open Open Discon. STATEFUL State Event Action New State ------------------------------------------------------------Idle Client or Device Requests Send Pending access service specific auth req Idle ASR Received for unknown session Send ASA Idle with Result-Code = UNKNOWN_ SESSION_ID Grant Access Open Pending Successful Service-specific authorization answer received with default Auth-Session-State value Successful Service-specific authorization answer received but service not provided Pending Sent STR Discon Pending Error processing successful Sent STR Service-specific authorization answer Failed Service-specific authorization answer received User or client device requests access to service Cleanup Discon Pending Idle Open Send service specific auth req Provide Service Open Open Successful Service-specific authorization answer received Failed Service-specific authorization answer received. Idle user/device Open Send STR Discon Calhoun. et al. Standards Track [Page 93] .
Send ASA Open with Result-Code != SUCCESS Send STR Discon Open ASR Received. and user successful is authorized serv. and successful user is authorized serv. is not authorized specific answer. specific answer Service-specific authorization Send Idle request received. et al. and user failed serv. and failed serv.RFC 3588 Diameter Based Protocol September 2003 Open ASR Received. STATEFUL State Event Action New State ------------------------------------------------------------Idle Service-specific authorization Send Open request received. client will not comply with request to end the session Open Authorization-Lifetime + Auth-Grace-Period expires on access device ASR Received STA Received Discon Discon Send ASA Discon Discon. Cleanup Home server wants to terminate the service Send ASR Discon Open Open Open Calhoun. Send STR. Standards Track [Page 94] . client will comply with request to end the session Send ASA Discon with Result-Code = SUCCESS. specific answer Idle Service-specific authorization Send Idle request received. Idle user/device The following state machine is observed by a server when it is maintaining state for the session: SERVER. user is not authorized specific answer Service-specific authorization Send Open request received.
STATELESS State Event Action New State ------------------------------------------------------------Idle Client or Device Requests Send Pending access service specific auth req Pending Successful Service-specific authorization answer received with Auth-SessionState set to NO_STATE_MAINTAINED Failed Service-specific authorization answer received Session-Timeout Expires on Access Device Service to user is terminated Grant Access Open Pending Cleanup Idle Open Discon. STR Received Send STA. Discon resend ASR Cleanup Idle Discon ASR successfully sent and ASA Received with Result-Code ASA Received Not Discon Any None No Change. Session-Timeout expires on home server Failure to send ASR Cleanup Idle Open Cleanup Idle Discon Wait. Cleanup. Idle The following state machine is observed by a client when state is not maintained on the server: CLIENT.RFC 3588 Diameter Based Protocol September 2003 Open Authorization-Lifetime (and Auth-Grace-Period) expires on home server. Standards Track [Page 95] . Idle user/device Discon. et al. Idle user/device Open Calhoun.
Otherwise. et al. STATELESS State Event Action New State ------------------------------------------------------------Idle Service-specific authorization Send serv. Both base Diameter AVPs as well as application specific AVPs MAY be inspected as a part of these tasks. and so on. fraud detection. The Diameter base protocol defines a default state machine that MUST be followed by all applications that have not specified other state machines.2. the use of this state machine is recommended only in applications where the value of the Accounting-Realtime-Required AVP is DELIVER_AND_GRANT. ordering. they are not standardized by the Diameter specifications. credit limits checks. See Section 9. and specific successfully processed answer 8. as these tasks are typically application or even policy dependent. However.7 for Accounting Command Codes and Section 9. The first state machine is to be observed by clients. Therefore. However. This is the second state machine in this section described below. Implementations of Diameter MAY perform checking.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. and hence accounting connectivity problems are required to cause the serviced user to be disconnected. 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 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. Idle request received. Note that such tracking is incompatible with the ability to sustain long duration connectivity problems. and other tasks based on these records. Applications MAY define requirements on when to accept accounting records based on the used value of Accounting-Realtime-Required AVP. Standards Track [Page 96] . records produced by the client Calhoun. correlation. The server side in the accounting state machine depends in some cases on the particular application. and does not place any standards requirement on the processing of these records. The tasks can happen either immediately after record reception or in a post-processing phase.8 for Accounting AVPs. The default server side state machine requires the reception of accounting records in any order and at any time.
or due to the peer sending back a transient failure or temporary protocol error notification DIAMETER_OUT_OF_SPACE.g. the event 'Failure to send' means that the Diameter client is unable to communicate with the desired destination. In the state table. 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. PendingE and PendingB stand for pending states to wait for an answer to an accounting request related to a Start. or DIAMETER_LOOP_DETECTED in the Result-Code AVP of the Accounting Answer command. respectively. ACCOUNTING State Event Action New State ------------------------------------------------------------Idle Client or device requests Send PendingS access accounting start req. Stop. which the value should be reasonably higher than the Acct_Interim_Interval value. This state machine is the third state machine in this section. The state machine is supervised by a supervision session timer Ts. DIAMETER_TOO_BUSY. Any event not listed in the state machines MUST be considered as an error condition.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 could be due to the peer being down. CLIENT. Note that the action 'Disconnect user/dev' MUST have an effect also to the authorization session state table. The states PendingS. if applicable. Interim. e. MUST be returned to the originator of the message. PendingI. et al. if the given application has both authentication/authorization and accounting portions. PendingL. cause the STR message to be sent. Idle Client or device requests a one-time service Send PendingE accounting event req Send record PendingB Idle Records in storage Calhoun. Standards Track [Page 97] .. The event 'Failed answer' means that the Diameter client received a non-transient failure notification in the Accounting Answer command. and a corresponding answer. Event or buffered record.
Open PendingI Successful accounting interim answer received Failure to send and (buffer space available or old record can be overwritten) and realtime not equal to DELIVER_AND_GRANT Failure to send and no buffer space available and realtime equal to GRANT_AND_LOSE Store interim record PendingI Open PendingI Open Calhoun. et al.RFC 3588 Diameter Based Protocol September 2003 PendingS Successful accounting start answer received Failure to send and buffer Store space available and realtime Start not equal to DELIVER_AND_GRANT Record Failure to send and no buffer space available and realtime equal to GRANT_AND_LOSE Failure to send and no buffer space available and realtime not equal to GRANT_AND_LOSE Failed accounting start answer received and realtime equal to GRANT_AND_LOSE Open PendingS Open PendingS Open PendingS Disconnect Idle user/dev PendingS Open PendingS Failed accounting start answer Disconnect Idle received and realtime not user/dev equal to GRANT_AND_LOSE User service terminated Store stop record PendingS PendingS Open Interim interval elapses Open User service terminated Send PendingI accounting interim record Send PendingL accounting stop req. Standards Track [Page 98] .
Standards Track [Page 99] .RFC 3588 Diameter Based Protocol September 2003 PendingI Failure to send and no buffer space available and realtime not equal to GRANT_AND_LOSE Failed accounting interim answer received and realtime equal to GRANT_AND_LOSE Failed accounting interim answer received and realtime not equal to GRANT_AND_LOSE User service terminated Disconnect Idle user/dev PendingI Open PendingI Disconnect Idle user/dev PendingI Store stop record PendingI PendingE Successful accounting event answer received Failure to send and buffer space available Store event record Idle PendingE Idle PendingE Failure to send and no buffer space available Failed accounting event answer received Successful accounting answer received Failure to send Failed accounting answer received Successful accounting stop answer received Failure to send and buffer space available Store stop record Delete record Delete record Idle PendingE Idle PendingB Idle PendingB PendingB Idle Idle PendingL Idle PendingL Idle PendingL Failure to send and no buffer space available Failed accounting stop answer received Idle PendingL Idle Calhoun. et al.
Send Idle accounting start answer Send Idle accounting event answer Send Idle accounting interim answer Send Idle accounting stop answer Send Idle accounting answer. STATELESS ACCOUNTING State Event Action New State ------------------------------------------------------------Idle Accounting start request received. Idle Interim record received. et al. STATEFUL ACCOUNTING State Event Action New State ------------------------------------------------------------Idle Accounting start request received. Calhoun. and successfully processed Accounting request received. Send Open accounting start answer. no space left to store records Idle SERVER. and successfully processed. Result-Code = OUT_OF_ SPACE Idle Accounting event request received. Idle Accounting stop request received. and successfully processed. and successfully processed. Standards Track [Page 100] .RFC 3588 Diameter Based Protocol September 2003 SERVER. Start Ts Send Idle accounting event answer Idle Accounting event request received. and successfully processed. and successfully processed.
Server-Initiated Re-Auth A Diameter server may initiate a re-authentication and/or reauthorization service for a particular session by issuing a Re-AuthRequest (RAR). the Diameter server that originally authorized a session may need some confirmation that the user is still using the services. Open Accounting stop request received. and successfully processed Open Accounting request received. 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. Calhoun. since some applications do not allow access devices to prompt the user for re-auth. Stop Ts Send Idle accounting answer. Stop Ts Stop Ts Idle Open Interim record received. Standards Track [Page 101] . Result-Code = OUT_OF_ SPACE Send Open accounting interim answer. et al. if the service supports this particular feature. Result-Code = OUT_OF_ SPACE. For example. no space left to store records Send Idle accounting answer. for pre-paid services.3. Each Diameter application MUST state whether service-initiated re-auth is supported. Restart Ts Send Idle accounting stop answer. no space left to store records Open Session supervision timer Ts expired 8. and successfully processed.RFC 3588 Diameter Based Protocol September 2003 Idle Accounting request received.
may be sent by any server to the access device that is providing session service.2. Calhoun. Standards Track [Page 102] . to request that the user be re-authenticated and/or re-authorized. indicated by the Command-Code set to 258 the message flags' 'R' bit clear. Result-Code AVP MUST be present. Re-Auth-Request The Re-Auth-Request (RAR).1. indicated by the Command-Code set to 258 and the message flags' 'R' bit set.3. et al. Message Format <RAR> ::= < < { { { { { { [ [ * [ * [ * [ Diameter Header: 258. REQ. The and The the Re-Auth-Answer Re-Auth-Answer (RAA). A successful RAA message MUST be followed by an application-specific authentication and/or authorization message.RFC 3588 Diameter Based Protocol September 2003 8. is sent in response to the RAR. 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. and indicates the disposition of request.3.
For sessions whose state is not being maintained. orderly shutdown of the access device. or because the access device does not support a mandatory AVP returned in the authorization.RFC 3588 Diameter Based Protocol September 2003 Message Format <RAA> ::= < < { { { [ [ [ [ * [ * [ [ [ * [ * [ Diameter Header: 258. expiration of Session-Timeout. et al. An STR MUST be issued when a user session terminates for any reason. etc. this section is not used. the access device that provided the service MUST issue a SessionTermination-Request (STR) message to the Diameter server that authorized the service. for example. Session Termination It is necessary for a Diameter server that authorized a session. It is also possible that a session that was authorized is never actually started due to action of a proxy.4. This could occur. for which it is maintaining state. If the answer did not contain an Auth-Session-State AVP with the value Calhoun. 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. administrative action. or because the access device is unwilling to provide the type of service requested in the authorization. to notify it that the session is no longer active. to be notified when that session is no longer active. due to a sudden resource shortage in the access device. converting the result from success to failure. For example. prior to forwarding the message to the access device. The access device also MUST issue an STR for a session that was authorized but never actually started. termination upon receipt of an Abort-SessionRequest (see below). including user logoff. When a user session that required Diameter authorization terminates. Standards Track [Page 103] . etc. a proxy may modify an authorization answer. 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.
session state) associated with the Session-Id specified in the STR. 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. Message Format <STR> ::= < < { { { { { [ [ * [ [ * [ * [ * [ Diameter Header: 275. REQ.. Standards Track [Page 104] . or when the Authorization-Lifetime and the AuthGrace-Period AVPs expires without receipt of a re-authorization request. and return a Session-Termination-Answer. expiration of either of these timers implies that the access device may have unexpectedly shut down. 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. A Diameter server also MUST clean up resources when the SessionTimeout expires.g. indicated by the Command-Code set to 275 and the Command Flags' 'R' bit set. A Diameter server that receives an STR message MUST clean up resources (e. et al. 8.RFC 3588 Diameter Based Protocol September 2003 NO_STATE_MAINTAINED.1. a proxy that causes an authorized session not to be started MUST issue an STR to the Diameter server that authorized the session. is sent by the access device to inform the Diameter Server that an authenticated and/or authorized session is being terminated.4. Session-Termination-Request The Session-Termination-Request (STR). thus. since the access device has no way of knowing that the session had been authorized.
the Diameter Server MUST release all resources for the session indicated by the Session-Id AVP. Whether the access Calhoun.4. indicated by the Command-Code set to 275 and the message flags' 'R' bit clear. et al. The Result-Code AVP MUST be present. 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). 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. Session-Termination-Answer The Session-Termination-Answer (STA). Upon sending or receipt of the STA. and MAY contain an indication that an error occurred while servicing the STR. 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. Any intermediate server in the Proxy-Chain MAY also release any resources. if necessary.RFC 3588 Diameter Based Protocol September 2003 8. On the other hand.2. For example. Standards Track [Page 105] . 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. Message Format <STA> ::= < < { { { [ * [ [ [ * [ [ * [ [ Diameter Header: 275. is sent by the Diameter Server to acknowledge the notification that the session has been terminated.
indicated by the Command-Code set to 274 and the message flags' 'R' bit clear.1. an access device may honor ASRs from certain agents only. Result-Code is set to DIAMETER_UNKNOWN_SESSION_ID. If the access device does not stop the session for any other reason. Note that if the access device does stop the session upon receipt of an ASR. Result-Code is set to DIAMETER_SUCCESS. et al.5.2. REQ. the access device MUST respond with an Abort-Session-Answer. Message Format <ASR> ::= < < { { { { { [ [ * [ * [ * [ Diameter Header: 274. Abort-Session-Answer The Abort-Session-Answer (ASA). 8.RFC 3588 Diameter Based Protocol September 2003 device stops the session or not is implementation. The 274 the the Abort-Session-Request Abort-Session-Request (ASR). indicated by the Command-Code set to and the message flags' 'R' bit set. If the session is not currently active. For example. 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. Calhoun.and/or configuration-dependent. may be sent by any server to access device that is providing session service. Result-Code is set to DIAMETER_UNABLE_TO_COMPLY. including a Result-Code AVP to indicate what action it took. If the session identified by Session-Id in the ASR was successfully terminated. and indicates the disposition of the request.5. In any case. is sent in response to the 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. The Result-Code AVP MUST be present. Standards Track [Page 106] . to request that session identified by the Session-Id be stopped.
to allow session state to be cleaned up globally. due to unanticipated shutdown of an access device. Standards Track [Page 107] . However. use of this mechanism across proxies is opportunistic rather than reliable. By including Origin-State-Id in CER/CEA messages.6. Calhoun. it may assume that the issuer has lost state since the previous message and that all sessions that were active under the lower Origin-StateId have been terminated. an access device also allows a server with which it communicates via proxy to make such a determination. 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. an access device allows a next-hop server to determine immediately upon connection whether the device has lost its sessions since the last connection. Thus. When a Diameter server receives an Origin-State-Id that is greater than the Origin-State-Id previously received from the same issuer. 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. but useful nonetheless. 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. 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. By including Origin-State-Id in request messages.RFC 3588 Diameter Based Protocol September 2003 Message Format <ASA> ::= < < { { { [ [ [ [ * [ * [ [ [ * [ * [ Diameter Header: 274. et al.
" character. and MUST contain the relevant application specific authentication AVPs that are needed by the Diameter server to authenticate the user. The request MUST include both the relevant application specific authentication information. authorized only or both. and authorization information necessary to identify the service being requested/offered.7. The Session-Id MUST begin with the sender's identity encoded in the DiameterIdentity type (see Section 4. and MUST contain the application specific authorization AVPs that are necessary to identify the service being requested/offered. The remainder of the Session-Id is delimited by a ". Note any value other than both MAY cause RADIUS interoperability issues. a recommended format for the implementation-defined portion is outlined below.8. AUTHORIZE_AUTHENTICATE 3 The request contains a request for both authentication and authorization. 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. Standards Track [Page 108] . and may be needed to correlate historical authentication information with accounting information. AUTHORIZE_ONLY 2 The request being sent is for authorization only. the Session-Id SHOULD appear immediately following the Diameter Header (see Section 3). as it is meant to uniquely identify a user session without reference to any other information. 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).RFC 3588 Diameter Based Protocol September 2003 8. however. 8. the following format is recommended. and MAY be any sequence that the client can guarantee to be eternally unique. 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. The following values are defined: AUTHENTICATE_ONLY 1 The request being sent is for authentication only. (square brackets [] indicate an optional element): Calhoun. When present. The Session-Id includes a mandatory portion and an implementation-defined portion. et al. The Session-Id MUST be globally and eternally unique.4).
1. or a value of all ones (meaning all bits in the 32 bit field are set to one) means no re-auth is expected.com. etc. The absence of this AVP. the high 32 bits of the 64-bit value MAY be initialized to the time. Great care should be taken when the AuthorizationLifetime value is determined. If both this AVP and the Session-Timeout AVP are present in a message. This is typically used in cases where multiple authentication methods are used.<low 32 bits>[. 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 reauthorized. 8. Note that a Session-Id MAY be used for both the authorization and accounting commands of a given application. in which there is an optional value: accesspoint7. <optional value> is implementation specific but may include a modem's device Id. since a low. Standards Track [Page 109] .acme. the value of the latter MUST NOT be smaller than the Authorization-Lifetime AVP.1876543210. Calhoun.1876543210. an implementation MAY keep track of the increasing value in non-volatile memory. A value of zero (0) means that immediate re-auth is necessary by the access device. et al.88 The Session-Id is created by the Diameter application initiating the session. Alternatively.mobile@200. value could create significant Diameter traffic. non-zero. 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. and the low 32 bits MAY be initialized to zero.<high 32 bits>. in which there is no optional value: accesspoint7. which could congest both the network and the agents. a layer 2 address.523 Example.RFC 3588 Diameter Based Protocol September 2003 <DiameterIdentity>. assuming the reboot process takes longer than a second.com. timestamp. which in most cases is done by the client.1.acme. This will for practical purposes eliminate the possibility of overlapping Session-Ids after a reboot. The 64-bit value is rendered in two part to simplify formatting by 32-bit processors.523.<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. Example. At startup.9.
et al.12. 8.RFC 3588 Diameter Based Protocol September 2003 An Authorization-Lifetime AVP MAY be present in re-authorization messages. the Re-Auth-Request-Type AVP MUST be present in an answer message. 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. The following values are supported: STATE_MAINTAINED 0 This value is used to specify that session state is being maintained. 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.10. or smaller. than the one provided by the client. the server MAY return a value that is equal to. but the value in the server's answer message is binding. and the access device MUST issue a session termination message when service to the user is terminated. However. 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. If the answer message contains an Authorization-Lifetime AVP with a positive value.11. 8. The following values are defined: Calhoun. The client MAY include this AVP in requests as a hint to the server. 8. 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. Standards Track [Page 110] . This AVP MAY be provided by the client as a hint of the maximum lifetime that it is willing to accept. 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.
A Session-Timeout AVP MAY be present in a re-authorization answer message. in a format consistent with the NAI specification [NAI]. et al. means that this session has an unlimited number of seconds before termination. unless both the access device and the home server had previously agreed that no session termination messages would be sent (see Section 8. the server MAY return a value that is equal to. Standards Track [Page 111] . A session that terminates on an access device due to the expiration of the Session-Timeout MUST cause an STR to be issued. than the one provided by the client. or the absence of this AVP. This AVP MAY be provided by the client as a hint of the maximum timeout that it is willing to accept. When both the Session-Timeout and the Authorization-Lifetime AVPs are present in an answer message. and contains the remaining number of seconds from the beginning of the re-auth. This is the default value if the AVP is not present in answer messages that include the AuthorizationLifetime. User-Name AVP The User-Name AVP (AVP Code 1) [RADIUS] is of type UTF8String. 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. AUTHORIZE_AUTHENTICATE 1 An authentication and authorization re-auth is expected upon expiration of the Authorization-Lifetime.9). or smaller.13. A value of zero.RFC 3588 Diameter Based Protocol September 2003 AUTHORIZE_ONLY 0 An authorization only re-auth is expected upon expiration of the Authorization-Lifetime.15. However. which contains the User-Name. the former MUST be equal to or greater than the value of the latter. 8. 8. 8. and is used to indicate the reason why a session was terminated on the access device. The following values are defined: Calhoun.14. Termination-Cause AVP The Termination-Cause AVP (AVP Code 295) is of type Enumerated.
due to administrative reasons. DIAMETER_ADMINISTRATIVE 4 The user was not granted access. MUST reflect the state of the entity indicated by Origin-Host. of type Unsigned32.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_AUTH_EXPIRED 6 The user's access was terminated since its authorized session time has expired. counter retained in non-volatile memory create a higher value for A Diameter entity MAY set or it MAY use an incrementing across restarts. DIAMETER_USER_MOVED 7 The user is receiving services from another access device. it MUST either remove Origin-State-Id or modify it appropriately as well. if present. DIAMETER_LINK_BROKEN 5 The communication to the user was abruptly disconnected. Origin-State-Id to the time of startup. such as the receipt of a Abort-SessionRequest message. Standards Track [Page 112] . Origin-State-Id MAY be included in any Diameter message. et al. or was disconnected. DIAMETER_SESSION_TIMEOUT 8 The user's session has timed out. Calhoun. Origin-State-Id AVP The Origin-State-Id AVP (AVP Code 278). and service has been terminated. is a monotonically increasing value that is advanced whenever a Diameter entity restarts with loss of previous state.16. If a proxy modifies Origin-Host. for example upon reboot. The Origin-State-Id. DIAMETER_BAD_ANSWER 3 This value indicates that the authorization answer received by the access device was not processed successfully. 8. including CER. A Diameter entity issuing this AVP MUST this AVP each time its state is reset.
8. that is. it MUST either not include Origin-State-Id in any message. When cleared. STR 2 When set. 8. the Destination-Host AVP MUST be present in all re-auth messages for this session. Origin-State-Id is used by an access device that always starts up with no active sessions. 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. 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.17. Session-Binding AVP The Session-Binding AVP (AVP Code 270) is of type Unsigned32. any session active prior to restart will have been lost. the default value. the Destination-Host AVP MUST be present in the STR message for this session. and the following bits have been defined: RE_AUTH 1 When set. or set its value to 0. When cleared. ACCOUNTING 4 When set. and MAY be present in application-specific authorization answer messages. the default value. Standards Track [Page 113] . If present. If an access device does not intend for such inferences to be made. the default value. the Destination-Host AVP. By including Origin-State-Id in a message. future re-auth messages for this session MUST NOT include the Destination-Host AVP. all accounting messages for this session MUST NOT include the Destination-Host AVP. When cleared. This field is a bit mask. it allows other Diameter entities to infer that sessions associated with a lower Origin-State-Id are no longer active. MUST be present in all accounting messages for this session. this AVP MAY inform the Diameter client that if a Calhoun.18. et al. Session-Server-Failover AVP The Session-Server-Failover AVP (AVP Code 271) is of type Enumerated. If present.RFC 3588 Diameter Based Protocol September 2003 Typically. the STR message for this session MUST NOT include the Destination-Host AVP. This AVP MAY also specify that a Session-Termination-Request message for this session MUST be sent to the same authorizing server. if known.
the Diameter client SHOULD issue a subsequent message without the Destination-Host AVP. assume that re-authorization succeeded. assume re-authorization succeeded. Class AVPs found in a re-authorization answer message override the ones found in any previous authorization answer message.RFC 3588 Diameter Based Protocol September 2003 re-auth or STR message fails due to a delivery problem. and SHOULD be present in application-specific authorization answer messages whose Result-Code AVP is set to DIAMETER_MULTI_ROUND_AUTH. et al. When absent. resend the failed message without the Destination-Host AVP present. If STR message delivery fails. terminate the session. This AVP contains the maximum number of seconds that the access device MUST provide the user in responding to an authentication request. If the second delivery fails for re-auth. If the second delivery fails for STR. 8. TRY_AGAIN_ALLOW_SERVICE 3 If either the re-auth or the STR message delivery fails. Calhoun. The following values are supported: REFUSE_SERVICE 0 If either the re-auth or the STR message delivery fails. ALLOW_SERVICE 2 If re-auth message delivery fails. they MUST be present in subsequent re-authorization. Multi-Round-Time-Out AVP The Multi-Round-Time-Out AVP (AVP Code 272) is of type Unsigned32. 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. the default value is REFUSE_SERVICE. Standards Track [Page 114] . terminate service with the user. When one or more Class AVPs are present in application-specific authorization answer messages. Diameter server implementations SHOULD NOT return Class AVPs that require more than 4096 bytes of storage on the Diameter client. session termination and accounting messages. A Diameter client that receives Class AVPs whose size exceeds local available storage MUST terminate the session. and do not attempt any subsequent attempts.19. 8.20. TRY_AGAIN 1 If either the re-auth or the STR message delivery fails. terminate the session. resend the failed message without the Destination-Host AVP present.
Standards Track [Page 115] . however. Note that batch accounting is not a requirement. 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. Event-Timestamp AVP The Event-Timestamp (AVP Code 55) is of type Time. 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. 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. instructs the Diameter node acting as a client to produce accounting records continuously even during a session.1. 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. or it could be handled using another protocol. Calhoun. transport protocols used under Diameter typically batch several requests in the same packet under heavy traffic conditions. Should batched accounting be required in the future.21. The Acct-Interim-Interval AVP. such as the need to perform credit limit checks and fraud detection. a new Diameter application will need to be created. that even if at the Diameter layer accounting requests are processed one by one. This may be sufficient for many applications. This information includes accounting record timeliness requirements. and MAY be included in an Accounting-Request and Accounting-Answer messages to record the time that the reported event occurred. and is therefore not supported by Diameter. when present. 9. Note. The authorization server (chain) directs the selection of proper transfer strategy. As discussed in [ACCMGMT].RFC 3588 Diameter Based Protocol September 2003 8. real-time transfer of accounting records is a requirement. in seconds since January 1. 1900 00:00 UTC. et al.
3. If IPsec and IKE are used to secure the Diameter session. A rejected Accounting-Request message MAY cause the user's session to be terminated. the latest value received SHOULD be used in further accounting activities for the same session.2. 9. so only their respective service-specific AVPs need to be defined in this section. If TLS is used to secure the Diameter session.. 9.g. which MUST reply with the Accounting-Answer message to confirm reception. 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. which MAY indicate that an error was present in the accounting message. then IP compression [IPComp] MAY be used and IKE [IKE] MAY be used to negotiate the compression parameters. Fault Resilience Diameter Base protocol mechanisms are used to overcome small message loss and network faults of temporary nature. The application MUST assume that the AVPs described in this document will be present in all Accounting messages. When one of these AVPs is present. Standards Track [Page 116] . 9. Each Diameter Accounting protocol message MAY be compressed. MUST define their Service-Specific AVPs that MUST be present in the Accounting-Request message in a section entitled "Accounting AVPs". NASREQ. 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. MobileIP). in order to reduce network bandwidth usage. The Accounting-Answer message includes the Result-Code AVP. Diameter peers acting as clients MUST implement the use of failover to guard against server failures and certain network failures. depending on the value of the Accounting-Realtime-Required AVP received earlier for the session in question. et al. The Accounting-Request message is used to transmit the accounting information to the Home AAA server. Application document requirements Each Diameter application (e.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.4. then TLS compression [TLS] MAY be used.
5. When the initial Calhoun. It is an implementation dependent matter for the client to accept new sessions under this condition. then the AVP MUST use the values START_RECORD. If the accounted service is of a measurable length. 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. INTERIM_RECORD. Different types of accounting records are sent depending on the actual type of accounted service and the authorization server's directions for interim accounting. then the Accounting-Record-Type AVP MUST be present and set to the value EVENT_RECORD. the client MUST starting sending the records in the non-volatile memory to the accounting server with appropriate modifications in termination cause. STOP_RECORD. and possibly. two accounting records MUST be generated for each service of type session. end-toend security may be used for authentication purposes. Diameter clients MAY have non-volatile memory for the safe storage of accounting records over reboots or extended network failures. The client MAY remove oldest. If the accounted service is a one-time event. This detection MUST be based on the inspection of the Session-Id and Accounting-Record-Number AVP pairs. Upon a reboot. If the authorization server has not directed interim accounting to be enabled for the session.RFC 3588 Diameter Based Protocol September 2003 in transit. et al. meaning that the start and stop of the event are simultaneous. The client SHOULD NOT remove the accounting data from any of its memory areas before the correct Accounting-Answer has been received. the Session-Id AVP MUST be present. undelivered or yet unacknowledged accounting data if it runs out of resources such as memory. session length. and server failures. the User-Name AVP MUST be present if it is available to the Diameter client. network partitions. Standards Track [Page 117] . If strong authentication across agents is required. 9. 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. Accounting Records In all accounting records. If such memory is available. Appendix C discusses duplicate detection needs and implementation issues. and other relevant information in the records.
or several records starting with one having the value START_RECORD. but a different Accounting-Sub-Session-Id AVP. Such applications would send messages with a constant Session-Id AVP. In such cases. except for the purposes of retransmission. A particular value of Accounting-Sub-Session-Id MUST appear only in one sequence of accounting records from a DIAMETER client.6. However.g. Correlation of Accounting Records The Diameter protocol's Session-Id AVP. In these cases. if a new record is being generated for the same session. each with their own unique Session-Id. the Acct-Multi-SessionId AVP is used for correlation. the AccountingRecord-Type AVP MUST be set to the value START_RECORD. et al. 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. Furthermore. When the last Accounting-Request is sent. followed by zero or more INTERIM_RECORD and a single STOP_RECORD. there are certain applications where a user receives service from different access devices (e.RFC 3588 Diameter Based Protocol September 2003 Accounting-Request for a given session is sent. If the authorization server has directed interim accounting to be enabled. which is globally unique (see Section 8. the Diameter client MUST produce additional records between the START_RECORD and STOP_RECORD. marked INTERIM_RECORD. A particular Diameter application specification MUST define the type of sequences that MUST be used. The production of these records is directed by Acct-Interim-Interval as well as any re-authentication or re-authorization of the session. 9. the value MUST be STOP_RECORD. The Diameter client MUST overwrite any previous interim accounting records that are locally stored for delivery. correlation is performed using the Session-Id. a server that Calhoun.8). Standards Track [Page 118] . The one sequence that is sent MUST be either one record with Accounting-Record-Type AVP set to the value EVENT_RECORD. Mobile IPv4). is used during the authorization phase to identify a particular session. 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. During authorization. This ensures that only one pending interim record can exist on an access device for any given session. Specific applications MAY require different a Session-ID for accounting messages.. there are certain applications that require multiple accounting sub-sessions.
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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.
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Message Format <ACR> ::= < < { { { { { [ [ [ [ [ [ [ [ [ [ * [ * [ * [ 9.7.2. 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 ]
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 AccountingRequest 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.
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Message Format <ACA> ::= < < { { { { { [ [ [ [ [ [ [ [ [ [ [ * [ * [ 9.8. 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 ]
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.
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and so on until the session ends and a STOP_RECORD record is produced. et al. Calhoun. The selection of whether to use INTERIM_RECORD records is done by the Acct-Interim-Interval AVP. The client uses information in this AVP to decide how and when to produce accounting records. 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. known as the client. STOP_RECORD 4 An Accounting Stop Record is sent to terminate an accounting session and contains cumulative accounting information relevant to the existing session. Further. 2. The Value field of this AVP is the nominal interval between these records in seconds. and STOP_RECORD are produced. 9. START_RECORD. based on the needs of the home-organization. With different values in this AVP. service sessions can result in one. The Diameter node that originates the accounting information. as appropriate for the service. two. MUST produce the first INTERIM_RECORD record roughly at the time when this nominal interval has elapsed from the START_RECORD. The omission of the Acct-Interim-Interval AVP or its inclusion with Value field set to 0 means that EVENT_RECORD. or two+N accounting records. additional interim record triggers MAY be defined by application-specific Diameter applications. Interim Accounting Records SHOULD be sent every time a re-authentication or re-authorization occurs. 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.2.RFC 3588 Diameter Based Protocol September 2003 INTERIM_RECORD 3 An Interim Accounting Record contains cumulative accounting information for an existing accounting session. The following accounting record production behavior is directed by the inclusion of this AVP: 1. the next one again as the interval has elapsed once more. Standards Track [Page 122] .8. 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.
8. Acct-Multi-Session-Id AVP The Acct-Multi-Session-Id AVP (AVP Code 50) is of type UTF8String. 9. a network problem. 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. 9.7. The absence of this AVP implies no sub-sessions are in use. As Session-Id AVPs are globally unique. where each session would have a unique Session-Id. and so on until the value for STOP_RECORD is one more than for the last INTERIM_RECORD. following the format specified in Section 8.8. 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.8. 2 for the second. and the value of this AVP MUST be monotonically increased by one for all new sub-sessions. Standards Track [Page 123] .3. and MUST be used in all accounting messages for the given session. et al.4. This AVP MAY be returned by the Diameter server in an authorization answer. The combination of the Session-Id and this AVP MUST be unique per subsession. the combination of Session-Id and AccountingRecord-Number AVPs is also globally unique. Acct-Session-Id AVP The Acct-Session-Id AVP (AVP Code 44) is of type OctetString is only used when RADIUS/Diameter translation occurs.RFC 3588 Diameter Based Protocol September 2003 9. Calhoun. for instance. 9. Accounting-Record-Number AVP The Accounting-Record-Number AVP (AVP Code 485) is of type Unsigned32 and identifies this record within one session. An easy way to produce unique numbers is to set the value to 0 for records of type EVENT_RECORD and START_RECORD. This AVP contains the contents of the RADIUS Acct-Session-Id attribute.5.8. 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.8. The Acct-MultiSession-Id AVP is used to link together multiple related accounting sessions. and can be used in matching accounting records with confirmations. 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.6. but the same Acct-Multi-Session-Id AVP. and set the value to 1 for the first INTERIM_RECORD.8. 9.
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.4. It is considered an error if there are more than one instance of the AVP. At least one instance of the AVP MUST be present in the message. 10. Calhoun. 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. One instance of the AVP MUST be present in the message. Base Protocol Command AVP Table 1 1+ 10. or MAY NOT be present. Note that the set of alternative accounting servers are treated as one server in this sense.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. or as long as records can still be stored as described in Section 9. Having to move the accounting record stream to a backup server is not a reason to discontinue the service to the user. AVP Occurrence Table The following tables presents the AVPs defined in this document. This is the default behavior if the AVP isn't included in the reply from the authorization server. The table uses the following symbols: 0 0+ 0-1 The AVP MUST NOT be present in the message.1. Zero or one instance of the AVP MAY be present in the message. and specifies in which Diameter messages they MAY. Zero or more instances of the AVP MAY be present in the message. et al. Note that AVPs that can only be present within a Grouped AVP are not represented in this table. Standards Track [Page 124] . The table in this section is limited to the non-accounting Command Codes defined in this specification.
|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. Standards Track [Page 125] .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. et al.
which may be expanded.2. +-----------+ | 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. These AVP occurrence requirements are guidelines. 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. Standards Track [Page 126] . et al.RFC 3588 Diameter Based Protocol September 2003 Vendor-Specific|0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | Application-Id | | | | | | | | | | | | | --------------------+---+---+---+---+---+---+---+---+---+---+---+---+ 10. and/or overridden by application-specific requirements in the Diameter applications documents.
a successor designated by the Area Director) for comment and review. The AVP Codes and sometimes also possible values in an AVP are controlled and maintained by IANA. Before a period of 30 days has passed. A denial notice must be justified by an explanation and. Standards Track [Page 127] . AVP Codes The AVP Code namespace is used to identify attributes. 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.1.RFC 3588 Diameter Based Protocol September 2003 11. in the cases where it is possible. and MUST include a pointer to a public specification. Diameter is not intended as a general purpose protocol. Calhoun. 11. The following policies are used here with the meanings defined in BCP 26: "Private Use". "IETF Consensus". "Expert Review".1. 11. AVP Header As defined in Section 4. the responsible IESG area director should appoint the Designated Expert. Vendor-ID and Flags field. concrete suggestions on how the request can be modified so as to become acceptable. "First Come First Served". "Specification Required".1. There are multiple namespaces. the request is posted to the AAA WG mailing list (or. in accordance with BCP 26 [IANA]. the AVP header contains three fields that requires IANA namespace management. if it has been disbanded. the AVP Code. For registration requests where a Designated Expert should be consulted. and allocations SHOULD NOT be made for purposes unrelated to authentication. This section explains the criteria to be used by the IANA for assignment of numbers within namespaces defined within this document. For Designated Expert with Specification Required. et al. The absence of a Vendor-ID or a Vendor-ID value of zero (0) identifies the IETF IANA controlled AVP Codes namespace. authorization or accounting. 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 vendorspecific AVP codes within their own namespace. IANA Considerations This section provides guidance to the Internet Assigned Numbers Authority (IANA) regarding registration of values related to the Diameter protocol. "Standards Action".
11.2. There are 8 bits in the AVP Flags field Section 4. defined in ('V'endor Specific). Command Code and Command Flags. Command Codes The Command Code namespace is used to identify Diameter commands. no guarantee is made for interoperability between Diameter peers using experimental commands.777. This document assigns bit 0 ('M'andatory) and bit 2 ('P'rotected). 287.1. AVPs may be allocated following Designated Expert with Specification Required [IANA].5 for the assignment of the namespace in this specification. 274-275.214 and 16. bit 1 The remaining bits should [IANA]. 280 and 282.1 for the assignment of the namespace in this specification. allocation of global AVPs should be encouraged instead. AVP Flags of the AVP header.215 (hexadecimal values 0xfffffe 0xffffff) are reserved for experimental commands. 480.777.2. The values 16. 258. See Section 3. AVP Codes 1-255 are managed separately as RADIUS Attribute Types [RADTYPE]. for functions specific only to one vendor's implementation of Diameter. 291-300. This document defines the Command Codes 257. and are defined as "RADIUS Packet Type Codes" in [RADTYPE]. Note that Diameter defines a mechanism for Vendor-Specific AVPs. 271. Release of blocks of AVPs (more than 3 at a time for a given purpose) should require IETF Consensus. 483 and 485-486. Where a Vendor-Specific AVP is implemented by more than one vendor. See Section 4. only be assigned via a Standards Action 11. where no interoperability is deemed useful.2. et al. standard commands. Diameter Header As defined in Section 3. the Diameter header contains two fields that require IANA namespace management. Calhoun. 276-285.RFC 3588 Diameter Based Protocol September 2003 AVP Code 0 is not used. Values 25616. as outlined in [IANA-EXP]. Vendor-Specific AVPs codes are for Private Use and should be encouraged instead of allocation of global attribute types.1. Standards Track [Page 128] . As these codes are only for experimental and testing purposes. This document defines the AVP Codes 257-274. 11.213 are for permanent.777. where the Vendor-Id field in the AVP header is set to a non-zero value. allocated by IETF Consensus [IANA]. The values 0-255 are reserved for RADIUS backward compatibility.
are for Private Use.2.RFC 3588 Diameter Based Protocol September 2003 11. Command Flags There are eight bits in the Command Flags field of the Diameter header. Vendor-Specific Application Identifiers. Standards Track [Page 129] . The following values are allocated.4. first-served basis. 3001-3010. Result-Code AVP Values As defined in Section 7. Calhoun. bit 2 ('E'rror) and bit 3 ('T').4. All remaining values are available for assignment via IETF Consensus [IANA]. Application Identifiers As defined in Section 2. 11. This document assigns bit 0 ('R'equest).1. First Served basis by IANA.0xfffffffe for vendor specific applications. bit 1 ('P'roxy). First Served basis by IANA. adding additional values to the list can be done on a First Come. 11. Both Application-Id and Acct-Application-Id AVPs use the same Application Identifier space.4. AVP Values Certain AVPs in Diameter define a list of values with various meanings. Bits 4 through 7 MUST only be assigned via a Standards Action [IANA].2.1. There are standards-track application ids and vendor specific application ids. For attributes other than those specified in this section. IANA [IANA] has assigned the range 0x00000001 to 0x00ffffff for standards-track applications.3. Vendor-Specific Application Identifiers are assigned on a First Come. et al. 2001-2002. the Result-Code AVP (AVP Code 268) defines the values 1001. on a first-come. Diameter Common Messages NASREQ Mobile-IP Diameter Base Accounting Relay 0 1 [NASREQ] 2 [DIAMMIP] 3 0xffffffff Assignment of standards-track application IDs are by Designated Expert with Specification Required [IANA]. 4001-4002 and 5001-5017. the Application Identifier is used to identify a specific Diameter Application. 11. and 0x01000000 .
4. Session-Server-Failover AVP Values As defined in Section 8.4. Session-Binding AVP Values As defined in Section 220.127.116.11. 11.7. Accounting-Record-Type AVP Values As defined in Section 9.8. Auth-Request-Type AVP Values As defined in Section 8.17. All remaining values are available for assignment via IETF Consensus [IANA].4. All remaining values are available for assignment via IETF Consensus [IANA]. 11. the Session-Server-Failover AVP (AVP Code 271) defines the values 0-3. et al.5. the Session-Binding AVP (AVP Code 270) defines the bits 1-4. All remaining values are available for assignment via IETF Consensus [IANA].4.RFC 3588 Diameter Based Protocol September 2003 11. 11.13.4. Calhoun.15.1. All remaining values are available for assignment via IETF Consensus [IANA]. All remaining values are available for assignment via IETF Consensus [IANA]. Disconnect-Cause AVP Values As defined in Section 5. 11.8. Termination-Cause AVP Values As defined in Section 126.96.36.199. the Redirect-Host-Usage AVP (AVP Code 261) defines the values 0-5.4. All remaining values are available for assignment via IETF Consensus [IANA].3.2.4. All remaining bits are available for assignment via IETF Consensus [IANA]. the Auth-Session-State AVP (AVP Code 277) defines the values 0-1. the Auth-Request-Type AVP (AVP Code 274) defines the values 1-3. Standards Track [Page 130] . the Disconnect-Cause AVP (AVP Code 273) defines the values 0-2.7. 11. the Termination-Cause AVP (AVP Code 295) defines the values 1-8. All remaining values are available for assignment via IETF Consensus [IANA]. Redirect-Host-Usage AVP Values As defined in Section 6. the Accounting-Record-Type AVP (AVP Code 480) defines the values 1-4.6. 11. 11.18. Auth-Session-State AVP Values As defined in Section 8.
6.10. All remaining values are available for assignment via IETF Consensus [IANA].4. Accounting-Realtime-Required AVP Values As defined in Section 9."New Connectionless Transport Protocol (NCTP). The following values have been placed into the registry: Services Field AAA+D2T AAA+D2S 220.127.116.11. RFC 5766".12. along with reference to a document that describes the transport protocol.4. For example . Diameter TCP/SCTP Port Numbers The IANA has assigned TCP and SCTP port number 3868 to Diameter.5. This MUST include the name and acronym for the protocol. the Re-Auth-Request-Type AVP (AVP Code 285) defines the values 0-1. Name and Contact Information: The name. 11. address. 11. Re-Auth-Request-Type AVP Values As defined in Section 8. 11. All remaining values are available for assignment via IETF Consensus [IANA].7. Protocol TCP SCTP Diameter protocol related configurable parameters This section contains the configurable parameters that are found throughout this document: Calhoun. 11. email address and telephone number for the person performing the registration.11.RFC 3588 Diameter Based Protocol September 2003 11. the Inband-Security-Id AVP (AVP Code 299) defines the values 0-1. Protocol: The specific transport protocol associated with that service field.4. the Accounting-Realtime-Required AVP (AVP Code 483) defines the values 1-3. et al. An example for a new fictitious transport protocol called NCTP might be "AAA+D2N". All remaining values are available for assignment via IETF Consensus [IANA]. Inband-Security-Id AVP (code 299) As defined in Section 6. Standards Track [Page 131] . NAPTR Service Fields The registration in the RFC MUST include the following information: Service Field: The service field being registered.
If a Diameter connection is not protected by IPsec. et al. after completion of the CER/CEA exchange. preshared keys can be used between the NAS and a local AAA proxy. It is suggested that IPsec be used primarily at the edges for intradomain exchanges. For protection of inter-domain exchanges. Calhoun. then the CER/CEA exchange MUST include an Inband-Security-ID AVP with a value of TLS. a TLS handshake will begin when both ends are in the open state. Realm Routing Table A Diameter proxy server routes messages based on the realm portion of a Network Access Identifier (NAI). and the address of the peer to which the message must be forwarded to. 13. Diameter servers MUST support TLS and IPsec. If the handshake fails. The server MUST have a table of Realm Names.RFC 3588 Diameter Based Protocol September 2003 Diameter Peer A Diameter entity MAY communicate with peers that are statically configured. which is typically used for all messages that cannot be locally processed. A statically configured Diameter peer would require that either the IP address or the fully qualified domain name (FQDN) be supplied. Diameter implementations MUST use transmission-level security of some kind (IPsec or TLS) on each connection.2 for more details on IPsec and TLS usage. end-to-end security is needed. TLS is recommended. This security mechanism is acceptable in environments where there is no untrusted third party agent.1 and 13. all further messages will be sent via TLS. See Sections 13. Diameter clients. In other situations. The routing table MAY also include a "default route". If the TLS handshake is successful. both ends move to the closed state. which would then be used to resolve through DNS. Tc timer The Tc timer controls the frequency that transport connection attempts are done to a peer with whom no active transport connection exists. Standards Track [Page 132] . The recommended value is 30 seconds. such as Network Access Servers (NASes) and Mobility Agents MUST support IP Security [SECARCH] and MAY support TLS [TLS]. Security Considerations The Diameter base protocol assumes that messages are secured by using either IPSec or TLS. For TLS usage. For NAS devices without certificate support.
integrity protection and confidentiality. to bring up another IKE Phase 2 SA to protect it. The receipt of an IKE Phase 2 delete message SHOULD NOT be interpreted as a reason for tearing down a Diameter connection. This avoids the potential for continually bringing connections up and down. and IKE Main Mode SHOULD NOT be used.1. it is preferable to leave the connection up. When digital signatures are used for authentication. This allows the Phase 2 security association to correspond to specific TCP and SCTP connections. when used in conformant implementations. and key management. either IKE Main Mode or IKE Aggressive Mode MAY be used. Conformant implementations MUST support both IKE Main Mode and Aggressive Mode. Phase 2 delete messages may be sent for idle SAs. Rather. IKE Aggressive Mode SHOULD be used. 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.RFC 3588 Diameter Based Protocol September 2003 13. When pre-shared keys are used for authentication. The Phase 2 Quick Mode exchanges used to negotiate protection for Diameter connections MUST explicitly carry the Identity Payload fields (IDci and IDcr). IKE negotiators SHOULD use pertinent certificate revocation checks before accepting a PKI certificate for use in IKE's authentication procedures. 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. using the IPsec DOI [IPSECDOI]. When digital signatures are used to achieve authentication. Standards Track [Page 133] .3 [IKE] SHOULD NOT be used. and MUST support the replay protection mechanisms of IPsec. Peer authentication using the public key encryption methods outlined in IKE's Sections 5. Calhoun. However. Diameter implementations MUST support peer authentication using a pre-shared key. The DOI provides for several types of identification data.2 and 5. Diameter implementations MUST support IKE for peer authentication. each ID Payload MUST carry a single IP address and a single non-zero port number. Since IPsec acceleration hardware may only be able to handle a limited number of active IKE Phase 2 SAs. et al. and MAY support certificatebased peer authentication using digital signatures. and MUST NOT use the IP Subnet or IP Address Range formats. negotiation of security associations. and if additional traffic is sent on it. as a means of keeping the number of active Phase 2 SAs to a minimum.
and a Diameter node that accepts a connection acts as a TLS server. As a result. Note that IPsec is considerably less flexible than TLS when it comes to configuring root CAs. In general. Standards Track [Page 134] . it is necessary to configure the root certificate authorities trusted by the Diameter peer. In order to ensure mutual authentication. Diameter nodes implementing TLS for security MUST mutually authenticate as part of TLS session establishment. and therefore peer discovery may be required. proper configuration of the trust model within a Diameter peer is essential to security. 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. When certificate authentication Diameter peers may not be known beforehand. the Diameter node acting as TLS server must request a certificate from the Diameter node acting as TLS client. TLS Usage A Diameter node that initiates a connection to another Diameter node acts as a TLS client according to [TLS]. within IPsec it is not possible to uniquely configure trusted root CAs for each application individually. et al. Since use of Port identifiers is prohibited within IKE Phase 1. Peer-to-Peer Considerations As with any peer-to-peer protocol. that a root CA trusted for use with Diameter must also be Calhoun.RFC 3588 Diameter Based Protocol September 2003 13. the same policy must be used for all applications. a Diameter peer will typically not be configured to allow connectivity with any arbitrary peer. This implies. for example. 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. 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.2. and the Diameter node acting as TLS client MUST be prepared to supply a certificate on request. When certificates are used.3. 13.
Calhoun. it would be necessary to plumb peer-specific policies either statically or dynamically. use of a simple static policy is the often the simplest route to IPsec-enabling a Diameter implementation. the policy would be "Require IPsec. TLS SHOULD be used to protect Diameter connections between administrative domains.g. Therefore. When pre-shared key authentication is used with IPsec to protect Diameter. a typical security policy for outbound traffic is "Initiate IPsec. a TLS-protected connection will match the IPsec policy. One implication of the recommended policy is that if a node is using both TLS and IPsec. and to be required whenever an inbound Diameter connection occurs. it is necessary for the set of Diameter peers to be known beforehand. Since IPsec extensions are typically not available to the sockets API on most platforms. This policy causes IPsec to be used whenever a Diameter peer initiates a connection to another Diameter peer.. Since Diameter uses the same port for TLS and non-TLS usage. but not both. peer discovery is typically not necessary. Standards Track [Page 135] . destination port Diameter". and both IPsec and TLS will be used to protect the Diameter connection. This policy is attractive. Inconsistent use of security mechanisms can result in redundant security mechanisms being used (e. These restrictions can be awkward at best. IPsec is most appropriate for intra-domain usage when pre-shared keys are used as a security mechanism. et al. As a result. To avoid this. When IPsec is used with Diameter. without reserving an additional port for TLS usage. an IPsec SA is automatically created based on a simple static policy. unique pre-shared keys are configured with Diameter peers. for inbound traffic. since it does not require policy to be set for each peer or dynamically modified each time a new Diameter connection is created. Since TLS supports application-level granularity in certificate policy. from any to me. potential security vulnerabilities. where the recommended IPsec policy is put in place. from me to any. there is not a convenient way in which to use either TLS or IPsec. and IPsec policy functionality is implementation dependent. destination port Diameter".RFC 3588 Diameter Based Protocol September 2003 trusted to protect SNMP. TLS over IPsec) or worse. It is recommended that a Diameter peer implement the same security mechanism (IPsec or TLS) across all its peer-to-peer connections. who are identified by their IP address (Main Mode). The following is intended to provide some guidance on the issue. or possibly their FQDN (Aggressive Mode).
14. Wroclawski. Narten. March 2002. Benson. RFC 3232. Firoiu. Overell. Stiliadis. and H. References Normative References Aboba.. and L. and J. Davie.. "An Expedited Forwarding PHB". T. P. Reynolds. BCP 26. Esibov. Crocker. "IEEE Standard for Binary Floating-Point Arithmetic". J. This can be accomplished via use of inbound and outbound filter policy. "Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers". Wood. RFC 3539. August 1985. "Assured Forwarding PHB Group". K.1.. "Authentication.. Le Boudec. Bennet. January 2002. June 2003. Black. Heinanen. Standards Track [Page 136] . B. and D. A. June 1999.. et al. and J. and J. RFC 2782. Alvestrand. "Augmented BNF for Syntax Specifications: ABNF". "A DNS RR for specifying the location of services (DNS SRV)". Weiss. and P.RFC 3588 Diameter Based Protocol September 2003 If IPsec is used to secure Diameter peer-to-peer connections. J.. Authorization and Accounting (AAA) Transport Profile".. Gulbrandsen.. and D. November 1997. Baker. F. Vollbrecht.. S. Institute of Electrical and Electronics Engineers. J. Baker. K. and to initiate IPsec protection for outbound connections. L. Blunk. B. V. "Assigned Numbers: RFC 1700 is Replaced by an On-line Database". W. "Guidelines for Writing an IANA Considerations Section in RFCs". W.. J. March 1998. Charny. RFC 2284. RFC 2234.. IPsec policy SHOULD be set so as to require IPsec protection for inbound connections. ANSI/IEEE Standard 754-1985. "PPP Extensible Authentication Protocol (EAP)". D. RFC 3246. RFC 2434. Vixie. [AAATRANS] [ABNF] [ASSIGNNO] [DIFFSERV] [DIFFSERVAF] [DIFFSERVEF] [DNSSRV] [EAP] [FLOATPOINT] [IANA] Calhoun. 14. December 1998. February 2000. October 1998. Courtney. Blake.. S. Davari. RFC 2597. RFC 2474. Nichols. A.. F.
C.iana. "Internet Protocol". and M. Paxson.. D. Shacham.. "RADIUS Types". Standards Track [Page 137] ." RFC 2915. July 1998. RFC 2373.org/assignments/radius-types Stewart. Hinden. Day. "Simple Network Time Protocol (SNTP) Version 4 for IPv4.RFC 3588 Diameter Based Protocol September 2003 [IANAADFAM] IANA.. T. "Service Location Protocol. J. Version 2". Guttman. and R. Pereira. November 1998... M. B. Beadles. "Stream Control Transmission Protocol".. I. November 1998. S. D.. September 2001. Monsour. Sharp. "Address Family Numbers". March 1997. RFC 2119.iana. RFC 2486.. RFC 2960. Kalla. IANA. D.iana. IPv6 and OSI". http://www. L. R.. Rytina. R. J. K. Mealling. C. RFC 2030. "Key words for use in RFCs to Indicate Requirement Levels". October 1996. RFC 3173. E. "The Network Access Identifier". October 2000. et al. "The naming authority pointer (NAPTR) DNS resource record.. Mills. Daniel. and M. http://www.. Morneault. Bradner. Xie. "The Internet Key Exchange (IKE)". September 1981.. "The Internet IP Security Domain of Interpretation for ISAKMP". and V. Taylor. BCP 14. Aboba. R. "Number assignment". R.. "IP Payload Compression Protocol (IPComp)". January 1999. Zhang. Perkins.. and M..org Harkins. [IANAWEB] [IKE] [IPComp] [IPSECDOI] [IPV4] [IPV6] [KEYWORDS] [NAI] [NAPTR] [RADTYPE] [SCTP] [SLP] [SNTP] Calhoun. RFC 2409. and S. "IP Version 6 Addressing Architecture". Piper. RFC 2407. Q. Carrel. A. September 2000. H. Veizades. Schwarzbauer. June 1999.org/assignments/address-family-numbers IANA. M.. Deering. and D. RFC 791. Thomas. http://www. RFC 2165. STD 5. Postel.
. T. H.. Campbell. RFC 2975. Baba.... Work in Progress. Shiino. RFC 2246. C. Sivalingham. H. Y.. T. B. Bulley. T. January 1981. Allen. A... P. [AAACMS] [AAAREQ] [ACCMGMT] [CDMA2000] [DIAMMIP] Calhoun. S.. Perkins. [TEMPLATE] [TLS] [TLSSCTP] [URI] [UTF8] 14. Aboba. and L. Perkins. B. RFC 2279. Jungmaier. RFC 793.. Zorn. Shiino. December 2002. H. "Diameter CMS Security Application". January 1999. Farrell.. G. Patil. "CDMA2000 Wireless Data Requirements for AAA". B. Chen. RFC 3141. E. Masinter.. Arkko. Informative References P... October 2000. and M... Glass. Manning. C. E.... Manning.. Dommety. B. and D... Ayaki... Jaques. "UTF-8. T. June 2001. Jacobs. W. "Transmission Control Protocol". C. Koo.RFC 3588 Diameter Based Protocol September 2003 [TCP] Postel. P. Calhoun. S. Lo. "Diameter Mobile IP Application". Berners-Lee.. Tuexen. J. Hirschman. S. "Criteria for Evaluating AAA Protocols for Network Access". Mitton. et al. Hameed. Guttman. Lim. S. a transformation format of ISO 10646". C. E. and A. Aboba. Munson. B. P. P. Lim.. R. E.. "The TLS Protocol Version 1.. Hsu.. R. Hiller. "Service Templates and Service: Schemes". S.. and C. A..... Standards Track [Page 138] . D. Rescorla. Hsu. Calhoun. Chen. M... Beadles. B. Perkins. and E. S. Sivalingham. RFC 3436.. "Uniform Resource Identifiers (URI): Generic Syntax". August 1998. Jaques. P. R.. M. Calhoun. Yergeau.. P. Calhoun..2. November 2000. McCann. Work in Progress.. P. "Introduction to Accounting Management".. F. Fielding. RFC 2609. Hiller. M. STD 7. X. McCann. January 1998. Hameed. T. Campbell. Walsh. Xu. Harrington. Hirschman. June 1999. Munson. G.0". Lipford. RFC 2396. Kempf. G. X.. T. S. Seki. Walsh. B. Dommety.. J.. Xu. Baba. S.. S. M.. Y. Dierks. RFC 2989... "Transport Layer Security over Stream Control Transmission Protocol".. and J. E.
Work in Progress. Narten. June 1999. and P. RFC 3576. RFC 2865. Ding. and C. Standards Track [Page 139] . Calhoun. P. RFC 2194. RFC 2977. T. Hiller. RFC 1661. B. C. T. "Proxy Chaining and Policy Implementation in Roaming". Perkins. "Mobile IP Authentication.RFC 3588 Diameter Based Protocol September 2003 [DYNAUTH] Chiba. RFC 2869.. M. Alsop. Zorn. September 1997.. October 2000.. "Dynamic Authorization Extensions to Remote Authentication Dial In User Service (RADIUS)". Authorization. Mitton. Beadles. January 1999. Jacobs. W. S. J. and W. D. RFC 2607. Glass. W. and D. RFC 3344. Vollbrecht. [IANA-EXP] [MIPV4] [MIPREQ] [NASNG] [NASREQ] [NASCRIT] [PPP] [PROXYCHAIN] [RADACCT] [RADEXT] [RADIUS] [ROAMREV] [ROAMCRIT] Calhoun. and B. August 2002. Wang. Work in Progress. W. "RADIUS Accounting". "Assigning Experimental and Testing Numbers Considered Useful". Dommety. Perkins. Willens. RFC 3169. and Accounting Requirements". S. "IP Mobility Support for IPv4". D. Mitton. and J. RFC 2866. "RADIUS Extensions".. A. June 2000. Haag. B. Willats. Simpson. G. "Criteria for Evaluating Network Access Server Protocols".. J. "Network Access Server Requirements Next Generation (NASREQNG) NAS Model". M... Aboba. Aboba. Eklund. Aboba. RFC 2477.. RFC 2881. September 2001. Aboba. Rubens.. Simpson. J. Beadles. "Criteria for Evaluating Roaming Protocols". "Review of Roaming Implementations". and G. and M. Rigney. and W.. July 2000. S. STD 51. Rubens. "Diameter NASREQ Application". June 2000. Bulley.. "Remote Authentication Dial In User Service (RADIUS)". et al.. M.. Calhoun. C. July 1994. Mitton. Rigney.. July 2003. C. C. "The Point-to-Point Protocol (PPP)". B. J. Rigney. A. Lu. June 2000.
Fox. Paul Funk and David Mitton were instrumental in getting the Peer State Machine correct. Mark Jones. RFC 1492. Kenneth Peirce. Sometimes Called TACACS". Lol Grant. et al. and our deep thanks go to them for their time. Bob Kopacz. Martin Julien. Haseeb Akhtar. RFC 2401. [TACACS] 15. William Bulley. Sumit Vakil. John R. and R. Jonathan Wood and Bernard Aboba provided invaluable assistance in working out transport issues. Victor Muslin. Finseth. C. Ryan Moats. Calhoun. "An Access Control Protocol. Atkinson. Jacques Caron provided many great comments as a result of a thorough review of the spec. Finally. November 1998.. July 1993. Allison Mankin. The authors would also like to acknowledge the following people for their contribution in the development of the Diameter protocol: Allan C. and similarly with Steven Bellovin in the security area. Rubens. Tony Johansson and Pankaj Patel for their participation in the pre-IETF Document Reading Party. "Security Architecture for the Internet Protocol". Mark Jones and Dave Spence. Acknowledgements The authors would like to thank Nenad Trifunovic. Standards Track [Page 140] . Text in this document was also provided by Paul Funk. Fredrik Johansson. Stephen Farrell. Nancy Greene. Paul Krumviede. Peter Heitman.RFC 3588 Diameter Based Protocol September 2003 [SECARCH] Kent. Vollbrecht and Jeff Weisberg. Ignacio Goyret. S. 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. Mark Eklund. Fergal Ladley. Daniel C. David Frascone. John Schnizlein.
) Name of submitter: "Erik Guttman" <Erik. template-url-syntax= url-path= .example. 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. A Diameter client can request specific Diameter servers based on characteristics of the Diameter service desired (for example.com:1812. confidentiality as well as perform end-point authentication. Standards Track [Page 141] .transport=tcp supported-auth-applications= string L M # This attribute lists the Diameter applications supported by the # AAA implementation. Calhoun. Template text: -------------------------template begins here----------------------template-type=service:diameter template-version=0. 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. Example: 'aaa://aaa.9. . Additional applications may be defined in the future.Guttman@sun. an AAA server to use for accounting.RFC 3588 Diameter Based Protocol September 2003 Appendix A.0 template-description= The Diameter protocol is defined by RFC 3588. Diameter Service Template The following service template describes the attributes used by Diameter servers to advertise themselves. Still. # An updated service template will be created at that time. This simplifies the process of selecting an appropriate server to communicate with.com> Language of service template: en Security Considerations: Diameter clients and servers use various cryptographic mechanisms to protect communication integrity. The Diameter URL format is described in Section 2. et al. # . Diameter implementations support one or more applications. The applications currently defined are: # Application Name Defined by # -------------------------------------------------# NASREQ Diameter Network Access Server Application # MobileIP Diameter Mobile IP Application # # Notes: # .
MobileIP supported-acct-applications= string L M # This attribute lists the Diameter applications supported by the # AAA implementation. Priority Weight Port Target IN SRV 0 1 5060 server1.example.. The applications currently defined are: # Application Name Defined by # -------------------------------------------------# NASREQ Diameter Network Access Server Application # MobileIP Diameter Mobile IP Application # # Notes: # . Standards Track [Page 142] .example._sctp. # An updated service template will be created at that time. though it MAY support other # transports._tcp.. and the following NAPTR records are returned: . Note that a compliant Diameter # implementation MUST support SCTP. SCTP will be used.ex.example.com. in that order. SCTP. The client performs a NAPTR query for that domain. order pref flags service IN NAPTR 50 50 "s" "AAA+D2S" _diameter. # . If the client supports over SCTP. Additional applications may be defined in the future.com regexp replacement "" 50 "s" "AAA+D2T" This indicates that the server supports SCTP. That lookup would return: .com 0 Calhoun.example.RFC 3588 Diameter Based Protocol September 2003 # NASREQ._sctp. consider a client that wishes to resolve aaa:ex.com. NAPTR Example As an example. et al. targeted to a host determined by an SRV lookup of _diameter. # NASREQ.com IN NAPTR 100 "" _aaa. Diameter implementations support one or more applications. too. and TCP.TCP -------------------------template ends here----------------------Appendix B.MobileIP supported-transports= string L M SCTP # This attribute lists the supported transports that the Diameter # implementation accepts.com IN SRV 2 5060 server2.
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. - - - The T flag is used as an indication of an application layer retransmission event.. Duplicate Detection As described in Section 9. the likelihood of duplication will vary according to the implementation.4. record to be sent. e. However. 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. (e. Duplicates can appear for various reasons: Failover to an alternate server. a client may not know whether it has already tried to send the accounting records in its nonvolatile memory before the reboot occurred. In other situations it may be necessary to perform real-time duplicate detection. accounting record duplicate detection is based on session identifiers. At that time records are likely to be sorted according to the included User-Name and duplicate elimination is easy in this case. Where close to real-time performance is required. due to a failover to an alternate peer. such as when credit limits are imposed or real-time fraud detection is desired. et al. Diameter servers MAY use the T flag as an aid when processing requests and detecting duplicate messages. Standards Track [Page 143] .g. after a reboot. Implementation problems and misconfiguration. Failover can occur at the client or within Diameter agents. due to failover to an alternate server. It is defined only for request messages sent by Diameter clients or agents. For instance. Since the retransmission behavior of RADIUS is not defined within [RFC2865].RFC 3588 Diameter Based Protocol September 2003 Appendix C. but prior to receipt of an application layer ACK and deletion of the record. Duplicates received from RADIUS gateways.g. Failure of a client or agent after sending of a record from nonvolatile memory. This will result in retransmission of the record soon after the client or agent has rebooted.. Calhoun. failover thresholds need to be kept low and this may lead to an increased likelihood of duplicates.
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. In a well run network. hashing techniques or other schemes. The likelihood of this occurring increases as the failover interval is decreased. A Diameter server MAY check the T flag of the received message to determine if the record is a possible duplicate. if sent. So only records within this time window need to be looked at in the backward direction. For example. After this time period has expired. Since the T flag does not affect interoperability. If the T flag is set in the request message. perhaps a day. the server searches for a duplicate within a configurable duplication time window backward and forward. have been received and recorded. in order to optimize duplicate detection. Since the Diameter server is responsible for duplicate detection. In order to be able to detect out of order duplicates. only generation of duplicates due to failover or resending of records in non-volatile storage can be reliably detected by Diameter clients or agents. in order to allow time for the original record to exit the network and be recorded by the accounting server.RFC 3588 Diameter Based Protocol September 2003 In general. et al. network partitions and device faults will presumably be rare events. then it may check the T flag marked records against the database with relative assurance that the original records. and may not be needed by some servers. The following is an example of how the T flag may be used by the server to detect duplicate requests. it can choose to make use of the T flag or not. generation of the T flag is REQUIRED for Diameter clients and agents. so this approach represents a substantial optimization of the duplicate detection process. it is possible for the original record to be received after the T flag marked record. may be used to eliminate the need to do a full search even in this set except for rare cases. it can be usually be assumed that duplicates appear within a time window of longest recorded network partition or device fault. Secondly. In such cases the Diameter client or agents can mark the message as possible duplicate by setting the T flag. but MAY be implemented by Diameter servers. such as the use of the T flag in the received messages. the Diameter server should use backward and forward time windows when performing duplicate checking for the T flag marked request. due to differences in network delays experienced along the path by the original and duplicate transmissions. As an example. This limits database searching to those records where the T flag is set. During failover. Standards Track [Page 144] . Calhoun.
Please address the information to the IETF Executive Director. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11. patents or patent applications. et al. neither does it represent that it has made any effort to identify any such rights. 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.RFC 3588 Diameter Based Protocol September 2003 Appendix D. 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. Calhoun. Standards Track [Page 145] . The IETF invites any interested party to bring to its attention any copyrights. or other proprietary rights which may cover technology that may be required to practice this standard. Copies of claims of rights made available for publication and any assurances of licenses to be made available.
com Jari Arkko Ericsson 02420 Jorvas Finland Phone: +358 40 5079256 EMail: Jari. 110 Nortech Parkway San Jose. Suite 500 Bellevue.RFC 3588 Diameter Based Protocol September 2003 Authors' Addresses Pat R. Calhoun Airespace. WA 98004 USA Phone: +1 425 438 8218 Calhoun. 7 74915 Waibstadt Germany Phone: EMail: +49 7263 911 701 erik.guttman@sun.. Eichhoelzelstr. California. 95134 USA Phone: +1 408-635-2023 Fax: +1 408-635-2020 EMail: firstname.lastname@example.com@nokia. Inc. Inc. et al. Standards Track [Page 146] .com John Loughney Nokia Research Center Itamerenkatu 11-13 00180 Helsinki Finland Phone: EMail: +358 50 483 6242 john.E.com Erik Guttman Sun email@example.com Glen Zorn Cisco Systems. 500 108th Avenue N. Inc.
RFC 3588 Diameter Based Protocol September 2003 Full Copyright Statement Copyright (C) The Internet Society (2003). EXPRESS OR IMPLIED. published and distributed. 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. Calhoun. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. provided that the above copyright notice and this paragraph are included on all such copies and derivative works. without restriction of any kind. 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. 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. All Rights Reserved. in whole or in part. et al. or as required to translate it into languages other than English. copied. 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. and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared. Standards Track [Page 147] . However. This document and translations of it may be copied and furnished to others. Acknowledgement Funding for the RFC Editor function is currently provided by the Internet Society.
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