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diff --git a/lib/diameter/doc/src/diameter_soc_rfc6733.xml b/lib/diameter/doc/src/diameter_soc_rfc6733.xml deleted file mode 100644 index 2098965706..0000000000 --- a/lib/diameter/doc/src/diameter_soc_rfc6733.xml +++ /dev/null @@ -1,8693 +0,0 @@ -<?xml version="1.0" encoding="utf-8" ?> - -<!-- - -<copyright> -<year>2013</year><year>2016</year> -<holder>Ericsson AB. All Rights Reserved.</holder> -</copyright> - -<legalnotice> -Licensed under the Apache License, Version 2.0 (the "License"); -you may not use this file except in compliance with the License. -You may obtain a copy of the License at - - http://www.apache.org/licenses/LICENSE-2.0 - -Unless required by applicable law or agreed to in writing, software -distributed under the License is distributed on an "AS IS" BASIS, -WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -See the License for the specific language governing permissions and -limitations under the License. - -</legalnotice> - ---> - -<!DOCTYPE section SYSTEM "chapter.dtd" [ - <!ENTITY gen_sctp '<seealso marker="kernel:gen_sctp">gen_sctp(3)</seealso>'> - <!ENTITY gen_tcp '<seealso marker="kernel:gen_tcp">gen_tcp(3)</seealso>'> - <!ENTITY service '<seealso marker="diameter#start_service-2">service</seealso>'> - <!ENTITY capabilities '<seealso marker="diameter#capability">capabilities</seealso>'> - <!ENTITY events '<seealso marker="diameter#service_event">events</seealso>'> - <!ENTITY nada '<p>No comment.</p>'> - <!ENTITY % also SYSTEM "seealso.ent" > - %also; -]> - -<section> -<title>Commentary</title> - -<p> -A more detailed commentary on &the_rfc; follows. -Its purpose is to (hopefully) clarify not only what is supported but -how, given that semantics and features discussed in the RFC are not -solely the responsibility of the diameter application: -in many cases much depends on the configuration a user passes to -diameter, the implementation of &man_app; callback modules in -particular.</p> - -<p> -Comments apply to all text following the preceding comment. -Be sure to distinguish between capitalized <em>Diameter</em>, the -protocol defined by the RFC, and lowercase <em>diameter</em>, the -Erlang application to which the commentary applies.</p> - -<warning> -<p> -The commentary is not yet complete. -Comments currently stop at chapter 4.</p> -</warning> - -<pre> -Fajardo, et al. Standards Track [Page 6] - -RFC 6733 Diameter Base Protocol October 2012 - - -1. Introduction - - Authentication, Authorization, and Accounting (AAA) protocols such as - TACACS [RFC1492] and RADIUS [RFC2865] were initially deployed to - provide dial-up PPP [RFC1661] and terminal server access. Over time, - AAA support was needed on many new access technologies, the scale and - complexity of AAA networks grew, and AAA was also used on new - applications (such as voice over IP). This led to new demands on AAA - protocols. -</pre> - -<p> -Note that diameter implements the Diameter protocol as defined in -&the_rfc;. -It also supported the previous version of the protocol, as defined in -RFC 3588, when there are differences. -(Which will be noted below.) -It does not support RADIUS.</p> - -<pre> - - Network access requirements for AAA protocols are summarized in - Aboba, et al. [RFC2989]. These include: - - Failover - - [RFC2865] does not define failover mechanisms and, as a result, - failover behavior differs between implementations. In order to - provide well-defined failover behavior, Diameter supports - application-layer acknowledgements and defines failover algorithms - and the associated state machine. -</pre> - -&nada; - -<pre> - - Transmission-level security - - RADIUS [RFC2865] defines an application-layer authentication and - integrity scheme that is required only for use with response - packets. While [RFC2869] defines an additional authentication and - integrity mechanism, use is only required during Extensible - Authentication Protocol (EAP) [RFC3748] sessions. While attribute - hiding is supported, [RFC2865] does not provide support for per- - packet confidentiality. In accounting, [RFC2866] assumes that - replay protection is provided by the backend billing server rather - than within the protocol itself. - - While [RFC3162] defines the use of IPsec with RADIUS, support for - IPsec is not required. In order to provide universal support for - transmission-level security, and enable both intra- and inter- - domain AAA deployments, Diameter provides support for TLS/TCP and - DTLS/SCTP. Security is discussed in Section 13. -</pre> - -<p> -Whether or not IPsec is used is transparent to diameter.</p> - -<p> -The transport protocol used on a given peer connection is also -transparent to diameter in that transport to diameter is simply a -module that implements the transport protocol documented in -&man_transport;. -A diameter user configures this module as the &mod_transport_opt; -<c>transport_module</c>.</p> - -<p> -While a user can implement their own transport modules, diameter -includes implementations for TCP and SCTP: -&man_tcp; based on &gen_tcp; and &man_sctp; based on &gen_sctp;. -The former supports TLS but the latter does not currently support -DTLS.</p> - -<pre> - - Reliable transport - - RADIUS runs over UDP, and does not define retransmission behavior; - as a result, reliability varies between implementations. As - described in [RFC2975], this is a major issue in accounting, where - packet loss may translate directly into revenue loss. In order to - - - - - - -Fajardo, et al. Standards Track [Page 7] - -RFC 6733 Diameter Base Protocol October 2012 - - - provide well-defined transport behavior, Diameter runs over - reliable transport mechanisms (TCP, Stream Control Transmission - Protocol (SCTP)) as defined in [RFC3539]. - - Agent support - - RADIUS does not provide for explicit support for agents, including - proxies, redirects, and relays. Since the expected behavior is - not defined, it varies between implementations. Diameter defines - agent behavior explicitly; this is described in Section 2.8. -</pre> - -&nada; - -<pre> - - Server-initiated messages - - While server-initiated messages are defined in RADIUS [RFC5176], - support is optional. This makes it difficult to implement - features such as unsolicited disconnect or re-authentication/ - re-authorization on demand across a heterogeneous deployment. To - address this issue, support for server-initiated messages is - mandatory in Diameter. -</pre> - -<p> -A diameter user can both send and receive messages.</p> - -<pre> - - Transition support - - While Diameter does not share a common protocol data unit (PDU) - with RADIUS, considerable effort has been expended in enabling - backward compatibility with RADIUS so that the two protocols may - be deployed in the same network. Initially, it is expected that - Diameter will be deployed within new network devices, as well as - within gateways enabling communication between legacy RADIUS - devices and Diameter agents. This capability enables Diameter - support to be added to legacy networks, by addition of a gateway - or server speaking both RADIUS and Diameter. -</pre> - -<p> -RADIUS Attributes can be redefined as Diameter AVP's using diameter's -&man_dict; interface but diameter provides no such definitions.</p> - -<pre> - - In addition to addressing the above requirements, Diameter also - provides support for the following: - - Capability negotiation - - RADIUS does not support error messages, capability negotiation, or - a mandatory/non-mandatory flag for attributes. Since RADIUS - clients and servers are not aware of each other's capabilities, - they may not be able to successfully negotiate a mutually - acceptable service or, in some cases, even be aware of what - service has been implemented. Diameter includes support for error - handling (Section 7), capability negotiation (Section 5.3), and - mandatory/non-mandatory Attribute-Value Pairs (AVPs) - (Section 4.1). - - - - - -Fajardo, et al. Standards Track [Page 8] - -RFC 6733 Diameter Base Protocol October 2012 - - - Peer discovery and configuration - - RADIUS implementations typically require that the name or address - of servers or clients be manually configured, along with the - corresponding shared secrets. This results in a large - administrative burden and creates the temptation to reuse the - RADIUS shared secret, which can result in major security - vulnerabilities if the Request Authenticator is not globally and - temporally unique as required in [RFC2865]. Through DNS, Diameter - enables dynamic discovery of peers (see Section 5.2). Derivation - of dynamic session keys is enabled via transmission-level - security. - - Over time, the capabilities of Network Access Server (NAS) devices - have increased substantially. As a result, while Diameter is a - considerably more sophisticated protocol than RADIUS, it remains - feasible to implement it within embedded devices. -</pre> - -&nada; - -<pre> - -1.1. Diameter Protocol - - The Diameter base protocol provides the following facilities: - - o Ability to exchange messages and deliver AVPs -</pre> - -<p> -There are two interfaces directly involved in message exchange when -using diameter: the function &mod_call; for sending outgoing requests, -and the application callback interface, documented in &man_app; for -receiving incoming request and answers.</p> - -<pre> - - o Capabilities negotiation -</pre> - -<p> -Capabilities negotiation is the responsibility of diameter: -a user configures a diameter service and/or transport with -&capabilities; to provide AVP values for CER and CEA messages but it -is diameter itself that sends these messages. -A user receives notification of a successful capabilities exchange by -way of &app_peer_up; callbacks.</p> - -<pre> - - o Error notification -</pre> - -<p> -A user can subscribe to &events;, using &mod_subscribe;, in order to -receive notification of various failures. -Errors in Diameter messaging are communicated via the application -callbacks &app_handle_request;, &app_handle_answer; and -&app_handle_error;.</p> - - -<pre> - - o Extensibility, required in [RFC2989], through addition of new - applications, commands, and AVPs -</pre> - -<p> -Support for applications, commands and AVP's is extensible using -diameter's dictionary interface, as documented in &man_dict;. -Dictionaries are compiled to Erlang encode/decode modules using -&man_compile; or &man_make;.</p> - -<pre> - - o Basic services necessary for applications, such as the handling of - user sessions or accounting -</pre> - -<p> -Compiled dictionaries are provided for the RFC 3588 and RFC 6733 -Diameter applications: common, base accounting and relay. -Dictionaries for a number of standardized -applications are provided in uncompiled form below the <c>examples</c> -subdirectory of the diameter application directory.</p> - -<pre> - - All data delivered by the protocol is in the form of AVPs. Some of - these AVP values are used by the Diameter protocol itself, while - others deliver data associated with particular applications that - employ Diameter. AVPs may be arbitrarily added to Diameter messages, - the only restriction being that the Command Code Format (CCF) - specification (Section 3.2) be satisfied. AVPs are used by the base - Diameter protocol to support the following required features: - - o Transporting of user authentication information, for the purposes - of enabling the Diameter server to authenticate the user - - o Transporting of service-specific authorization information, - between client and servers, allowing the peers to decide whether a - user's access request should be granted - - - -Fajardo, et al. Standards Track [Page 9] - -RFC 6733 Diameter Base Protocol October 2012 - - - o Exchanging resource usage information, which may be used for - accounting purposes, capacity planning, etc. - - o Routing, relaying, proxying, and redirecting of Diameter messages - through a server hierarchy - - The Diameter base protocol satisfies the minimum requirements for a - AAA protocol, as specified by [RFC2989]. The base protocol may be - used by itself for accounting purposes only, or it may be used with a - Diameter application, such as Mobile IPv4 [RFC4004], or network - access [RFC4005]. It is also possible for the base protocol to be - extended for use in new applications, via the addition of new - commands or AVPs. The initial focus of Diameter was network access - and accounting applications. A truly generic AAA protocol used by - many applications might provide functionality not provided by - Diameter. Therefore, it is imperative that the designers of new - applications understand their requirements before using Diameter. - See Section 1.3.4 for more information on Diameter applications. - - Any node can initiate a request. In that sense, Diameter is a peer- - to-peer protocol. In this document, a Diameter client is a device at - the edge of the network that performs access control, such as a - Network Access Server (NAS) or a Foreign Agent (FA). A Diameter - client generates Diameter messages to request authentication, - authorization, and accounting services for the user. A Diameter - agent is a node that does not provide local user authentication or - authorization services; agents include proxies, redirects, and relay - agents. A Diameter server performs authentication and/or - authorization of the user. A Diameter node may act as an agent for - certain requests while acting as a server for others. - - The Diameter protocol also supports server-initiated messages, such - as a request to abort service to a particular user. -</pre> - -&nada; - -<pre> - -1.1.1. Description of the Document Set - - The Diameter specification consists of an updated version of the base - protocol specification (this document) and the Transport Profile - [RFC3539]. This document obsoletes both RFC 3588 and RFC 5719. A - summary of the base protocol updates included in this document can be - found in Section 1.1.3. - - This document defines the base protocol specification for AAA, which - includes support for accounting. There are also a myriad of - applications documents describing applications that use this base - specification for Authentication, Authorization, and Accounting. - These application documents specify how to use the Diameter protocol - within the context of their application. - - - -Fajardo, et al. Standards Track [Page 10] - -RFC 6733 Diameter Base Protocol October 2012 - - - The Transport Profile document [RFC3539] discusses transport layer - issues that arise with AAA protocols and recommendations on how to - overcome these issues. This document also defines the Diameter - failover algorithm and state machine. - - "Clarifications on the Routing of Diameter Request Based on the - Username and the Realm" [RFC5729] defines specific behavior on how to - route requests based on the content of the User-Name AVP (Attribute - Value Pair). - -1.1.2. 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 [RFC2119]. -</pre> - -&nada; - -<pre> - -1.1.3. Changes from RFC 3588 - - This document obsoletes RFC 3588 but is fully backward compatible - with that document. The changes introduced in this document focus on - fixing issues that have surfaced during the implementation of - Diameter (RFC 3588). An overview of some the major changes are given - below. -</pre> - -<p> -RFC 6733 is not fully backwards compatible with RFC 3588. -(For example, in what values of Result-Code values are permissible with -the E-bit.) -The implications of incompatibilities for diameter are noted where -appropriate.</p> - -<pre> - - o Deprecated the use of the Inband-Security AVP for negotiating - Transport Layer Security (TLS) [RFC5246]. It has been generally - considered that bootstrapping of TLS via Inband-Security AVP - creates certain security risks because it does not completely - protect the information carried in the CER/CEA (Capabilities- - Exchange-Request/Capabilities-Exchange-Answer). This version of - Diameter adopts the common approach of defining a well-known - secured port that peers should use when communicating via TLS/TCP - and DTLS/SCTP. This new approach augments the existing in-band - security negotiation, but it does not completely replace it. The - old method is kept for backward compatibility reasons. -</pre> - -<p> -&man_tcp; supports both methods of negotiating TLS: -bootstrapping via Inband-Security and directly following connection -establishment.</p> - -<pre> - - o Deprecated the exchange of CER/CEA messages in the open state. - This feature was implied in the peer state machine table of RFC - 3588, but it was not clearly defined anywhere else in that - document. As work on this document progressed, it became clear - that the multiplicity of meaning and use of Application-Id AVPs in - the CER/CEA messages (and the messages themselves) is seen as an - abuse of the Diameter extensibility rules and thus required - simplification. Capabilities exchange in the open state has been - re-introduced in a separate specification [RFC6737], which clearly - defines new commands for this feature. -</pre> - -<p> -Capabilities exchange in the open state is not supported: an incoming -CER in the open state will cause diameter to ask the relevant -transport process to terminate, which implies the loss of the peer -connection in the case of &man_tcp; and &man_sctp;.</p> - -<p> -Capabilities update, as defined by RFC 6737, is not yet supported. -Support will require diameter to handle CUR/CUA in the same way that -it handles CER/CEA.</p> - -<pre> - - - - - -Fajardo, et al. Standards Track [Page 11] - -RFC 6733 Diameter Base Protocol October 2012 - - - o Simplified security requirements. The use of a secured transport - for exchanging Diameter messages remains mandatory. However, TLS/ - TCP and DTLS/SCTP have become the primary methods of securing - Diameter with IPsec as a secondary alternative. See Section 13 - for details. The support for the End-to-End security framework - (E2E-Sequence AVP and 'P'-bit in the AVP header) has also been - deprecated. -</pre> - -<p> -The End-to-End security framework is not supported since it's use is -largely unspecified: diameter will set the P-bit in outgoing AVP's as -directed by the relevant dictionary and/or &app_prepare_request; or -&app_handle_request; callbacks, but whether or not the P-bit is set on -incoming AVP's has no consequence.</p> - -<p> -As noted above, DTLS is not currently supported and whether or not -IPsec is used is transparent to diameter.</p> - -<pre> - - o Changed Diameter extensibility. This includes fixes to the - Diameter extensibility description (Section 1.3 and others) to - better aid Diameter application designers; in addition, the new - specification relaxes the policy with respect to the allocation of - Command Codes for vendor-specific uses. - - o Clarified Application Id usage. Clarify the proper use of - Application Id information, which can be found in multiple places - within a Diameter message. This includes correlating Application - Ids found in the message headers and AVPs. These changes also - clearly specify the proper Application Id value to use for - specific base protocol messages (ASR/ASA, STR/STA) as well as - clarify the content and use of Vendor-Specific-Application-Id. - - o Clarified routing fixes. This document more clearly specifies - what information (AVPs and Application Ids) can be used for making - general routing decisions. A rule for the prioritization of - redirect routing criteria when multiple route entries are found - via redirects has also been added (see Section 6.13). - - o Simplified Diameter peer discovery. The Diameter discovery - process now supports only widely used discovery schemes; the rest - have been deprecated (see Section 5.2 for details). -</pre> - -<p> -Peer discover is not currently supported: peers to which a node should -connect must be configured. -Connection requests are accepted from arbitrary peers but a -&mod_transport_opt; <c>capabilities_cb</c> can be used to reject a -peer based on an incoming CER or CEA.</p> - -<pre> - - There are many other miscellaneous fixes that have been introduced in - this document that may not be considered significant, but they have - value nonetheless. Examples are removal of obsolete types, fixes to - the state machine, clarification of the election process, message - validation, fixes to Failed-AVP and Result-Code AVP values, etc. All - of the errata filed against RFC 3588 prior to the publication of this - document have been addressed. A comprehensive list of changes is not - shown here for practical reasons. - -1.2. Terminology - - AAA - - Authentication, Authorization, and Accounting. - - - - - -Fajardo, et al. Standards Track [Page 12] - -RFC 6733 Diameter Base Protocol October 2012 - - - ABNF - - Augmented Backus-Naur Form [RFC5234]. A metalanguage with its own - formal syntax and rules. It is based on the Backus-Naur Form and - is used to define message exchanges in a bi-directional - communications protocol. - - Accounting - - The act of collecting information on resource usage for the - purpose of capacity planning, auditing, billing, or cost - allocation. - - Accounting Record - - An accounting record represents a summary of the resource - consumption of a user over the entire session. Accounting servers - creating the accounting record may do so by processing interim - accounting events or accounting events from several devices - serving the same user. - - Authentication - - The act of verifying the identity of an entity (subject). - - Authorization - - The act of determining whether a requesting entity (subject) will - be allowed access to a resource (object). - - Attribute-Value Pair (AVP) - - The Diameter protocol consists of a header followed by one or more - Attribute-Value-Pairs (AVPs). An AVP includes a header and is - used to encapsulate protocol-specific data (e.g., routing - information) as well as authentication, authorization, or - accounting information. -</pre> - -&nada; - -<pre> - - Command Code Format (CCF) - - A modified form of ABNF used to define Diameter commands (see - Section 3.2). -</pre> - -<p> -The <c>@messages</c> section of the &man_dict; format has the CCF as -content.</p> - -<pre> - - Diameter Agent - - A Diameter Agent is a Diameter node that provides relay, proxy, - redirect, or translation services. - - - - -Fajardo, et al. Standards Track [Page 13] - -RFC 6733 Diameter Base Protocol October 2012 - - - Diameter Client - - A Diameter client is a Diameter node that supports Diameter client - applications as well as the base protocol. Diameter clients are - often implemented in devices situated at the edge of a network and - provide access control services for that network. Typical - examples of Diameter clients include the Network Access Server - (NAS) and the Mobile IP Foreign Agent (FA). - - Diameter Node - - A Diameter node is a host process that implements the Diameter - protocol and acts as either a client, an agent, or a server. - - Diameter Peer - - Two Diameter nodes sharing a direct TCP or SCTP transport - connection are called Diameter peers. - - Diameter Server - - A Diameter server is a Diameter node that handles authentication, - authorization, and accounting requests for a particular realm. By - its very nature, a Diameter server must support Diameter server - applications in addition to the base protocol. -</pre> - -<p> -A Diameter Node is implemented by configuring a service -using &mod_start_service; and one or more transports using -&mod_add_transport;. -The service typically represents a Diameter Node but since -capabilities can be configured on individual transports it's more -accurate to say that the node is a collection of transports -advertising the same Origin-Host.</p> - -<p> -The role of a node (agent, client or server) is not something that's -configured explicitly. -Transports are either connecting or listening, depending on whether -diameter should establish a peer connection and send CER or accept -connections and receive CER, but the role a node implements depends -largely on dictionary configuration and &man_app; callback -implementation.</p> - -<pre> - - Downstream - - Downstream is used to identify the direction of a particular - Diameter message from the home server towards the Diameter client. - - Home Realm - - A Home Realm is the administrative domain with which the user - maintains an account relationship. - - Home Server - - A Diameter server that serves the Home Realm. - - Interim Accounting - - An interim accounting message provides a snapshot of usage during - a user's session. Typically, it is implemented in order to - provide for partial accounting of a user's session in case a - device reboot or other network problem prevents the delivery of a - session summary message or session record. - - - - -Fajardo, et al. Standards Track [Page 14] - -RFC 6733 Diameter Base Protocol October 2012 - - - Local Realm - - A local realm is the administrative domain providing services to a - user. An administrative domain may act as a local realm for - certain users while being a home realm for others. - - Multi-session - - A multi-session represents a logical linking of several sessions. - Multi-sessions are tracked by using the Acct-Multi-Session-Id. An - example of a multi-session would be a Multi-link PPP bundle. Each - leg of the bundle would be a session while the entire bundle would - be a multi-session. - - Network Access Identifier - - The Network Access Identifier, or NAI [RFC4282], is used in the - Diameter protocol to extract a user's identity and realm. The - identity is used to identify the user during authentication and/or - authorization while the realm is used for message routing - purposes. - - Proxy Agent or Proxy - - In addition to forwarding requests and responses, proxies make - policy decisions relating to resource usage and provisioning. - Typically, this is accomplished by tracking the state of NAS - devices. While proxies usually do not respond to client requests - prior to receiving a response from the server, they may originate - Reject messages in cases where policies are violated. As a - result, proxies need to understand the semantics of the messages - passing through them, and they may not support all Diameter - applications. - - Realm - - The string in the NAI that immediately follows the '@' character. - NAI realm names are required to be unique and are piggybacked on - the administration of the DNS namespace. Diameter makes use of - the realm, also loosely referred to as domain, to determine - whether messages can be satisfied locally or whether they must be - routed or redirected. In RADIUS, realm names are not necessarily - piggybacked on the DNS namespace but may be independent of it. - - - - - - - - -Fajardo, et al. Standards Track [Page 15] - -RFC 6733 Diameter Base Protocol October 2012 - - - Real-Time Accounting - - Real-time accounting involves the processing of information on - resource usage within a defined time window. Typically, time - constraints are imposed in order to limit financial risk. The - Diameter Credit-Control Application [RFC4006] is an example of an - application that defines real-time accounting functionality. - - Relay Agent or Relay - - Relays forward requests and responses based on routing-related - AVPs and routing table entries. Since relays do not make policy - decisions, they do not examine or alter non-routing AVPs. As a - result, relays never originate messages, do not need to understand - the semantics of messages or non-routing AVPs, and are capable of - handling any Diameter application or message type. Since relays - make decisions based on information in routing AVPs and realm - forwarding tables, they do not keep state on NAS resource usage or - sessions in progress. - - Redirect Agent - - Rather than forwarding requests and responses between clients and - servers, redirect agents refer clients to servers and allow them - to communicate directly. Since redirect agents do not sit in the - forwarding path, they do not alter any AVPs transiting between - client and server. Redirect agents do not originate messages and - are capable of handling any message type, although they may be - configured only to redirect messages of certain types, while - acting as relay or proxy agents for other types. As with relay - agents, redirect agents do not keep state with respect to sessions - or NAS resources. -</pre> - -&nada; - -<pre> - - Session - - A session is a related progression of events devoted to a - particular activity. Diameter application documents provide - guidelines as to when a session begins and ends. All Diameter - packets with the same Session-Id are considered to be part of the - same session. -</pre> - -<p> -Sessions are not something that diameter is aware of. -The function &mod_session_id; can be used to construct appropriate -values for Session-Id AVP's but logic connecting events in the same -session is the responsibility of the diameter user.</p> - -<pre> - - Stateful Agent - - A stateful agent is one that maintains session state information, - by keeping track of all authorized active sessions. Each - authorized session is bound to a particular service, and its state - is considered active either until it is notified otherwise or - until expiration. - - - -Fajardo, et al. Standards Track [Page 16] - -RFC 6733 Diameter Base Protocol October 2012 - - - Sub-session - - A sub-session represents a distinct service (e.g., QoS or data - characteristics) provided to a given session. These services may - happen concurrently (e.g., simultaneous voice and data transfer - during the same session) or serially. These changes in sessions - are tracked with the Accounting-Sub-Session-Id. - - Transaction State - - The Diameter protocol requires that agents maintain transaction - state, which is used for failover purposes. Transaction state - implies that upon forwarding a request, the Hop-by-Hop Identifier - is saved; the field is replaced with a locally unique identifier, - which is restored to its original value when the corresponding - answer is received. The request's state is released upon receipt - of the answer. A stateless agent is one that only maintains - transaction state. - - Translation Agent - - A translation agent (TLA in Figure 4) is a stateful Diameter node - that performs protocol translation between Diameter and another - AAA protocol, such as RADIUS. - - Upstream - - Upstream is used to identify the direction of a particular - Diameter message from the Diameter client towards the home server. - - User - - The entity or device requesting or using some resource, in support - of which a Diameter client has generated a request. -</pre> - -&nada; - -<pre> - -1.3. Approach to Extensibility - - The Diameter protocol is designed to be extensible, using several - mechanisms, including: - - o Defining new AVP values - - o Creating new AVPs - - o Creating new commands - - o Creating new applications - - - - -Fajardo, et al. Standards Track [Page 17] - -RFC 6733 Diameter Base Protocol October 2012 - - - From the point of view of extensibility, Diameter authentication, - authorization, and accounting applications are treated in the same - way. -</pre> - -<p> -Extensibility in diameter is by way of the dictionary interface -documented in &man_dict;: a diameter user creates applications, -commands and AVP's by implementing a new dictionary, -compiling the dictionary to a codec module using &man_compile; or -&man_make;, and configuring the resulting dictionary module on a -service. -The dictionary modules provided with diameter are all implemented in -this manner.</p> - -<pre> - Note: Protocol designers should try to reuse existing functionality, - namely AVP values, AVPs, commands, and Diameter applications. Reuse - simplifies standardization and implementation. To avoid potential - interoperability issues, it is important to ensure that the semantics - of the reused features are well understood. Given that Diameter can - also carry RADIUS attributes as Diameter AVPs, such reuse - considerations also apply to existing RADIUS attributes that may be - useful in a Diameter application. -</pre> - -<p> -Reuse in dictionary files is achieved by way of the <c>@inherits</c> -section. -AVP's are inherited, commands are not.</p> - -<pre> - -1.3.1. Defining New AVP Values - - In order to allocate a new AVP value for AVPs defined in the Diameter - base protocol, the IETF needs to approve a new RFC that describes the - AVP value. IANA considerations for these AVP values are discussed in - Section 11.3. - - The allocation of AVP values for other AVPs is guided by the IANA - considerations of the document that defines those AVPs. Typically, - allocation of new values for an AVP defined in an RFC would require - IETF Review [RFC5226], whereas values for vendor-specific AVPs can be - allocated by the vendor. - -1.3.2. Creating New AVPs - - A new AVP being defined MUST use one of the data types listed in - Sections 4.2 or 4.3. If an appropriate derived data type is already - defined, it SHOULD be used instead of a base data type to encourage - reusability and good design practice. - - In the event that a logical grouping of AVPs is necessary, and - multiple "groups" are possible in a given command, it is recommended - that a Grouped AVP be used (see Section 4.4). - - The creation of new AVPs can happen in various ways. The recommended - approach is to define a new general-purpose AVP in a Standards Track - RFC approved by the IETF. However, as described in Section 11.1.1, - there are other mechanisms. -</pre> - -<p> -Creating new AVP's is an issue for the dictionary designer, not -diameter.</p> - -<pre> - -1.3.3. Creating New Commands - - A new Command Code MUST be allocated when required AVPs (those - indicated as {AVP} in the CCF definition) are added to, deleted from, - or redefined in (for example, by changing a required AVP into an - optional one) an existing command. - - - -Fajardo, et al. Standards Track [Page 18] - -RFC 6733 Diameter Base Protocol October 2012 - - - Furthermore, if the transport characteristics of a command are - changed (for example, with respect to the number of round trips - required), a new Command Code MUST be registered. - - A change to the CCF of a command, such as described above, MUST - result in the definition of a new Command Code. This subsequently - leads to the need to define a new Diameter application for any - application that will use that new command. - - The IANA considerations for Command Codes are discussed in - Section 3.1. -</pre> - -<p> -Creating new commands is an issue for the dictionary designer, not -diameter.</p> - -<pre> - -1.3.4. Creating New Diameter Applications - - Every Diameter application specification MUST have an IANA-assigned - Application Id (see Section 2.4). The managed Application ID space - is flat, and there is no relationship between different Diameter - applications with respect to their Application Ids. As such, there - is no versioning support provided by these Application Ids - themselves; every Diameter application is a standalone application. - If the application has a relationship with other Diameter - applications, such a relationship is not known to Diameter. -</pre> - -<p> -Creating new applications is an issue for the dictionary designer, -not diameter.</p> - -<p> -An application's Application Id is specified in the <c>@id</c> section -of a dictionary file.</p> - -<pre> - - Before describing the rules for creating new Diameter applications, - it is important to discuss the semantics of the AVP occurrences as - stated in the CCF and the M-bit flag (Section 4.1) for an AVP. There - is no relationship imposed between the two; they are set - independently. - - o The CCF indicates what AVPs are placed into a Diameter command by - the sender of that command. Often, since there are multiple modes - of protocol interactions, many of the AVPs are indicated as - optional. - - o The M-bit allows the sender to indicate to the receiver whether or - not understanding the semantics of an AVP and its content is - mandatory. If the M-bit is set by the sender and the receiver - does not understand the AVP or the values carried within that AVP, - then a failure is generated (see Section 7). -</pre> - -<p> -The M-bit is set on outgoing AVP's as directed by the relevant -dictionary. -For incoming AVP's, an M-bit set on an AVP that isn't -explicitly included in the definition of the command in question is -interpreted as a 5001 error, DIAMETER_AVP_UNSUPPORTED, the -consequences of which depend on the value of the &mod_application_opt; -<c>answer_errors</c> or <c>request_errors</c>.</p> - -<pre> - - It is the decision of the protocol designer when to develop a new - Diameter application rather than extending Diameter in other ways. - However, a new Diameter application MUST be created when one or more - of the following criteria are met: - - - - - - - -Fajardo, et al. Standards Track [Page 19] - -RFC 6733 Diameter Base Protocol October 2012 - - - M-bit Setting - - An AVP with the M-bit in the MUST column of the AVP flag table is - added to an existing Command/Application. An AVP with the M-bit - in the MAY column of the AVP flag table is added to an existing - Command/Application. - - Note: The M-bit setting for a given AVP is relevant to an - Application and each command within that application that includes - the AVP. That is, if an AVP appears in two commands for - application Foo and the M-bit settings are different in each - command, then there should be two AVP flag tables describing when - to set the M-bit. - - Commands - - A new command is used within the existing application because - either an additional command is added, an existing command has - been modified so that a new Command Code had to be registered, or - a command has been deleted. - - AVP Flag bits - - If an existing application changes the meaning/semantics of its - AVP Flags or adds new flag bits, then a new Diameter application - MUST be created. - - If the CCF definition of a command allows it, an implementation may - add arbitrary optional AVPs with the M-bit cleared (including vendor- - specific AVPs) to that command without needing to define a new - application. Please refer to Section 11.1.1 for details. -</pre> - -&nada; - -<pre> - -2. Protocol Overview - - The base Diameter protocol concerns itself with establishing - connections to peers, capabilities negotiation, how messages are sent - and routed through peers, and how the connections are eventually torn - down. The base protocol also defines certain rules that apply to all - message exchanges between Diameter nodes. - - Communication between Diameter peers begins with one peer sending a - message to another Diameter peer. The set of AVPs included in the - message is determined by a particular Diameter application. One AVP - that is included to reference a user's session is the Session-Id. - - The initial request for authentication and/or authorization of a user - would include the Session-Id AVP. The Session-Id is then used in all - subsequent messages to identify the user's session (see Section 8 for - - - -Fajardo, et al. Standards Track [Page 20] - -RFC 6733 Diameter Base Protocol October 2012 - - - more information). The communicating party may accept the request or - reject it by returning an answer message with the Result-Code AVP set - to indicate that an error occurred. The specific behavior of the - Diameter server or client receiving a request depends on the Diameter - application employed. - - Session state (associated with a Session-Id) MUST be freed upon - receipt of the Session-Termination-Request, Session-Termination- - Answer, expiration of authorized service time in the Session-Timeout - AVP, and according to rules established in a particular Diameter - application. -</pre> - -<p> -Like Session-Id, session state is maintained by the diameter user: -diameter has no session state of its own and does not interpret -STR/STA in any way.</p> - -<pre> - - The base Diameter protocol may be used by itself for accounting - applications. For authentication and authorization, it is always - extended for a particular application. - - Diameter clients MUST support the base protocol, which includes - accounting. In addition, they MUST fully support each Diameter - application that is needed to implement the client's service, e.g., - Network Access Server Requirements (NASREQ) [RFC2881] and/or Mobile - IPv4. A Diameter client MUST be referred to as "Diameter X Client" - where X is the application that it supports and not a "Diameter - Client". - - Diameter servers MUST support the base protocol, which includes - accounting. In addition, they MUST fully support each Diameter - application that is needed to implement the intended service, e.g., - NASREQ and/or Mobile IPv4. A Diameter server MUST be referred to as - "Diameter X Server" where X is the application that it supports, and - not a "Diameter Server". - - Diameter relays and redirect agents are transparent to the Diameter - applications, but they MUST support the Diameter base protocol, which - includes accounting, and all Diameter applications. - - Diameter proxies MUST support the base protocol, which includes - accounting. In addition, they MUST fully support each Diameter - application that is needed to implement proxied services, e.g., - NASREQ and/or Mobile IPv4. A Diameter proxy MUST be referred to as - "Diameter X Proxy" where X is the application which it supports, and - not a "Diameter Proxy". - -</pre> - -&nada; - -<pre> - - - - - - - - - -Fajardo, et al. Standards Track [Page 21] - -RFC 6733 Diameter Base Protocol October 2012 - - -2.1. Transport - - The Diameter Transport profile is defined in [RFC3539]. - - The base Diameter protocol is run on port 3868 for both TCP [RFC0793] - and SCTP [RFC4960]. For TLS [RFC5246] and Datagram Transport Layer - Security (DTLS) [RFC6347], a Diameter node that initiates a - connection prior to any message exchanges MUST run on port 5658. It - is assumed that TLS is run on top of TCP when it is used, and DTLS is - run on top of SCTP when it is used. -</pre> - -<p> -Which port a transport connects to or listens on is a matter of -configuration. -Both &man_tcp; and &man_sctp; will default to 3868 if no other value -is specified.</p> - -<pre> - - If the Diameter peer does not support receiving TLS/TCP and DTLS/SCTP - connections on port 5658 (i.e., the peer complies only with RFC - 3588), then the initiator MAY revert to using TCP or SCTP on port - 3868. Note that this scheme is kept only for the purpose of backward - compatibility and that there are inherent security vulnerabilities - when the initial CER/CEA messages are sent unprotected (see - Section 5.6). - - Diameter clients MUST support either TCP or SCTP; agents and servers - SHOULD support both. - - A Diameter node MAY initiate connections from a source port other - than the one that it declares it accepts incoming connections on, and - it MUST always be prepared to receive connections on port 3868 for - TCP or SCTP and port 5658 for TLS/TCP and DTLS/SCTP connections. - When DNS-based peer discovery (Section 5.2) is used, the port numbers - received from SRV records take precedence over the default ports - (3868 and 5658). - - A given Diameter instance of the peer state machine MUST NOT use more - than one transport connection to communicate with a given peer, - unless multiple instances exist on the peer, in which, case a - separate connection per process is allowed. -</pre> - -<p> -The &mod_service_opt; <c>restrict_connection</c> controls to what -extent a diameter service allows multiple connections to the same -peer. -(As identified by the value of Origin-Host received from it -during capabilities exchange.)</p> - -<pre> - - When no transport connection exists with a peer, an attempt to - connect SHOULD be made periodically. This behavior is handled via - the Tc timer (see Section 12 for details), whose recommended value is - 30 seconds. There are certain exceptions to this rule, such as when - a peer has terminated the transport connection stating that it does - not wish to communicate. - -</pre> - -<p> -The frequency of reconnection attempts is configured with the -&mod_transport_opt; <c>connect_timer</c> and -<c>watchdog_timer</c>.</p> - -<pre> - - When connecting to a peer and either zero or more transports are - specified, TLS SHOULD be tried first, followed by DTLS, then by TCP, - and finally by SCTP. See Section 5.2 for more information on peer - discovery. -</pre> - -<p> -The order in which different transports are attempted depends on the -order of &mod_transport_opt; <c>transport_module</c> and -<c>transport_config</c> tuples in transport configuration.</p> - -<pre> - - - -Fajardo, et al. Standards Track [Page 22] - -RFC 6733 Diameter Base Protocol October 2012 - - - Diameter implementations SHOULD be able to interpret ICMP protocol - port unreachable messages as explicit indications that the server is - not reachable, subject to security policy on trusting such messages. - Further guidance regarding the treatment of ICMP errors can be found - in [RFC5927] and [RFC5461]. Diameter implementations SHOULD also be - able to interpret a reset from the transport and timed-out connection - attempts. If Diameter receives data from the lower layer that cannot - be parsed or identified as a Diameter error made by the peer, the - stream is compromised and cannot be recovered. The transport - connection MUST be closed using a RESET call (send a TCP RST bit) or - an SCTP ABORT message (graceful closure is compromised). -</pre> - -<p> -ICMP messages and other transport-level errors aren't directly -visible to diameter but transport implementations like &man_tcp; and -&man_sctp; propagate these as terminating transport processes.</p> - -<pre> - -2.1.1. SCTP Guidelines - - Diameter messages SHOULD be mapped into SCTP streams in a way that - avoids head-of-the-line (HOL) blocking. Among different ways of - performing the mapping that fulfill this requirement it is - RECOMMENDED that a Diameter node send every Diameter message (request - or response) over stream zero with the unordered flag set. However, - Diameter nodes MAY select and implement other design alternatives for - avoiding HOL blocking such as using multiple streams with the - unordered flag cleared (as originally instructed in RFC 3588). On - the receiving side, a Diameter entity MUST be ready to receive - Diameter messages over any stream, and it is free to return responses - over a different stream. This way, both sides manage the available - streams in the sending direction, independently of the streams chosen - by the other side to send a particular Diameter message. These - messages can be out-of-order and belong to different Diameter - sessions. -</pre> - -<p> -&man_sctp; allows the sender to specify a stream number explicitly. -The stream on which an incoming message is received it passed to -&app_handle_request; and &app_handle_answer; callbacks as -<c>transport_data</c> in a <c>#diameter_packet{}</c>.</p> - -<p> -Ordered or unordered delivery can be configured per transport.</p> - -<pre> - - Out-of-order delivery has special concerns during a connection - establishment and termination. When a connection is established, the - responder side sends a CEA message and moves to R-Open state as - specified in Section 5.6. If an application message is sent shortly - after the CEA and delivered out-of-order, the initiator side, still - in Wait-I-CEA state, will discard the application message and close - the connection. In order to avoid this race condition, the receiver - side SHOULD NOT use out-of-order delivery methods until the first - message has been received from the initiator, proving that it has - moved to I-Open state. To trigger such a message, the receiver side - could send a DWR immediately after sending a CEA. Upon reception of - the corresponding DWA, the receiver side should start using out-of- - order delivery methods to counter the HOL blocking. -</pre> - -<p> -&man_sctp; does not currently allow the user to switch between ordered -and unordered delivery, or to specify the manner of sending per -message: one or the other must be configured, the defaults being -ordered.</p> - -<pre> - - Another race condition may occur when DPR and DPA messages are used. - Both DPR and DPA are small in size; thus, they may be delivered to - the peer faster than application messages when an out-of-order - delivery mechanism is used. Therefore, it is possible that a DPR/DPA - - - -Fajardo, et al. Standards Track [Page 23] - -RFC 6733 Diameter Base Protocol October 2012 - - - exchange completes while application messages are still in transit, - resulting in a loss of these messages. An implementation could - mitigate this race condition, for example, using timers, and wait for - a short period of time for pending application level messages to - arrive before proceeding to disconnect the transport connection. - Eventually, lost messages are handled by the retransmission mechanism - described in Section 5.5.4. - - A Diameter agent SHOULD use dedicated payload protocol identifiers - (PPIDs) for clear text and encrypted SCTP DATA chunks instead of only - using the unspecified payload protocol identifier (value 0). For - this purpose, two PPID values are allocated: the PPID value 46 is for - Diameter messages in clear text SCTP DATA chunks, and the PPID value - 47 is for Diameter messages in protected DTLS/SCTP DATA chunks. -</pre> - -&nada; - -<pre> - -2.2. Securing Diameter Messages - - Connections between Diameter peers SHOULD be protected by TLS/TCP and - DTLS/SCTP. All Diameter base protocol implementations MUST support - the use of TLS/TCP and DTLS/SCTP. If desired, alternative security - mechanisms that are independent of Diameter, such as IPsec [RFC4301], - can be deployed to secure connections between peers. The Diameter - protocol MUST NOT be used without one of TLS, DTLS, or IPsec. -</pre> - -<p> -As noted above, DTLS is not currently supported and IPsec usage is -transparent to diameter. -Security is not enforced by diameter.</p> - -<pre> - -2.3. Diameter Application Compliance - - Application Ids are advertised during the capabilities exchange phase - (see Section 5.3). Advertising support of an application implies - that the sender supports the functionality specified in the - respective Diameter application specification. - - Implementations MAY add arbitrary optional AVPs with the M-bit - cleared (including vendor-specific AVPs) to a command defined in an - application, but only if the command's CCF syntax specification - allows for it. Please refer to Section 11.1.1 for details. -</pre> - -&nada; - -<pre> - -2.4. Application Identifiers - - Each Diameter application MUST have an IANA-assigned Application ID. - The base protocol does not require an Application Id since its - support is mandatory. During the capabilities exchange, Diameter - nodes inform their peers of locally supported applications. - Furthermore, all Diameter messages contain an Application Id, which - is used in the message forwarding process. - - - - - - - -Fajardo, et al. Standards Track [Page 24] - -RFC 6733 Diameter Base Protocol October 2012 - - - The following Application Id values are defined: - - Diameter common message 0 - Diameter base accounting 3 - Relay 0xffffffff -</pre> - -<p> -These applications are implemented in the dictionary modules -<c>diameter_gen_base_rfc6733</c>, <c>diameter_gen_acct_rfc6733</c> and -<c>diameter_relay</c> respectively. -There are also RFC 3588 versions or the common and accounting -dictionaries: <c>diameter_gen_base_rfc3588</c> and -<c>diameter_base_accounting</c>. -(The inconsistent naming is historical.) -Dictionary modules are configured using the &mod_application_opt; -<c>dictionary</c>.</p> - -<pre> - Relay and redirect agents MUST advertise the Relay Application ID, - while all other Diameter nodes MUST advertise locally supported - applications. The receiver of a Capabilities Exchange message - advertising relay service MUST assume that the sender supports all - current and future applications. - - Diameter relay and proxy agents are responsible for finding an - upstream server that supports the application of a particular - message. If none can be found, an error message is returned with the - Result-Code AVP set to DIAMETER_UNABLE_TO_DELIVER. -</pre> - -&nada; - -<pre> - -2.5. Connections vs. Sessions - - This section attempts to provide the reader with an understanding of - the difference between "connection" and "session", which are terms - used extensively throughout this document. - - A connection refers to a transport-level connection between two peers - that is used to send and receive Diameter messages. A session is a - logical concept at the application layer that exists between the - Diameter client and the Diameter server; it is identified via the - Session-Id AVP. - - +--------+ +-------+ +--------+ - | 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 the 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. - - - - -Fajardo, et al. Standards Track [Page 25] - -RFC 6733 Diameter Base Protocol October 2012 - - - 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. Also, note - that Diameter messages pertaining to the session, both application- - specific and those that are defined in this document such as ASR/ASA, - RAR/RAA, and STR/STA, MUST carry the Application Id of the - application. Diameter messages pertaining to peer connection - establishment and maintenance such as CER/CEA, DWR/DWA, and DPR/DPA - MUST carry an Application Id of zero (0). -</pre> - -<p> -As noted above, diameter is not involved in session management. -This is the responsibility of the diameter user.</p> - -<pre> - -2.6. Peer Table - - The Diameter peer table is used in message forwarding and is - referenced by the 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 4.3.1, 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 it 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. If public key - certificates are used for Diameter security (e.g., with TLS), this - value MUST NOT be greater than the expiry times in the relevant - certificates. - - TLS/TCP and DTLS/SCTP Enabled - - Specifies whether TLS/TCP and DTLS/SCTP is to be used when - communicating with the peer. - - Additional security information, when needed (e.g., keys, - certificates). -</pre> - -<p> -The Peer Table is not directly accessible to the diameter user. -Information about connected peers can be retrieved using -&mod_service_info;.</p> - -<pre> - - - -Fajardo, et al. Standards Track [Page 26] - -RFC 6733 Diameter Base Protocol October 2012 - - -2.7. Routing Table - - All Realm-Based routing lookups are performed against what is - commonly known as the routing table (see Section 12). Each routing - table entry contains the following fields: - - Realm Name - - This is the field that MUST be 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 an Application Id. A route entry - can have a different destination based on the Application Id in - the message header. 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 can be satisfied locally and do - not need to be routed to another Diameter entity. - - 2. RELAY - All Diameter messages that fall within this category - MUST be routed to a next-hop Diameter entity that is indicated - by the identifier described below. Routing is done without - modifying any non-routing AVPs. See Section 6.1.9 for - relaying guidelines. - - 3. PROXY - All Diameter messages that fall within this category - MUST be routed to a next Diameter entity that is indicated by - the identifier described below. The local server MAY apply - its local policies to the message by including new AVPs to the - message prior to routing. See Section 6.1.9 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 6.1.8 for redirection guidelines. - - - - - - -Fajardo, et al. Standards Track [Page 27] - -RFC 6733 Diameter Base Protocol October 2012 - - - Server Identifier - - The identity of one or more servers to which the message is to be - routed. This identity MUST also be present in the Host Identity - field of the peer table (Section 2.6). When the Local Action is - set to RELAY or PROXY, this field contains the identity of the - server(s) to which the message MUST be routed. When the Local - Action field is set to REDIRECT, this field contains the identity - of one or more servers to which the message MUST be redirected. - - Static or Dynamic - - Specifies whether a route entry was statically configured or - dynamically discovered. - - Expiration Time - - Specifies the time at which a dynamically discovered route table - entry expires. If public key certificates are used for Diameter - security (e.g., with TLS), this value MUST NOT be greater than the - expiry time in the relevant certificates. - - 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 they MUST follow the - protocol compliance guidelines in Section 2. Relay agents 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 Id (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. -</pre> - -<p> -Routing does not need specific support in diameter: a user can -maintain their own routing table if desired and implement any desired -routing in &man_app; callbacks. -However, it may be convenient to add more specific routing support to -diameter in the future.</p> - -<pre> - -2.8. Role of Diameter Agents - - In addition to clients and servers, the Diameter protocol introduces - relay, proxy, redirect, and translation agents, each of which is - defined in Section 1.2. Diameter agents are useful for several - reasons: -</pre> - -<p> -An noted above, the role a node plays is largely a question of -configuration and &man_app; callback implementation.</p> - -<pre> - - o They can distribute administration of systems to a configurable - grouping, including the maintenance of security associations. - - - - -Fajardo, et al. Standards Track [Page 28] - -RFC 6733 Diameter Base Protocol October 2012 - - - o They can be used for concentration of requests from a number of - co-located or distributed NAS equipment sets to a set of like user - groups. - - o They can do value-added processing to the requests or responses. - - o They can be used for load balancing. - - o A complex network will have multiple authentication sources, they - can sort requests and forward towards the correct target. - - The Diameter protocol requires that agents maintain transaction - state, which is used for failover purposes. Transaction state - implies that upon forwarding a request, its Hop-by-Hop Identifier is - saved; the field is replaced with a locally unique identifier, which - is restored to its original value when the corresponding answer is - received. The request's state is released upon receipt of the - answer. A stateless agent is one that only maintains transaction - state. - - The Proxy-Info AVP allows stateless agents to add local state to a - Diameter request, with the guarantee that the same state will be - present in the answer. However, the protocol's failover procedures - require that agents maintain a copy of pending requests. - - A stateful agent is one that maintains session state information by - keeping track of all authorized active sessions. Each authorized - session is bound to a particular service, and its state is considered - active until either the agent is notified otherwise or the session - expires. Each authorized session has an expiration, which is - communicated by Diameter servers via the Session-Timeout AVP. - - Maintaining session state may be useful in certain applications, such - as: - - o Protocol translation (e.g., RADIUS <-> Diameter) - - o Limiting resources authorized to a particular user - - o Per-user or per-transaction auditing - - A Diameter agent MAY act in a stateful manner for some requests and - be stateless for others. A Diameter implementation MAY act as one - type of agent for some requests and as another type of agent for - others. -</pre> - -&nada; - -<pre> - - - - - - -Fajardo, et al. Standards Track [Page 29] - -RFC 6733 Diameter Base Protocol October 2012 - - -2.8.1. Relay Agents - - Relay agents are Diameter agents that accept requests and route - messages to other Diameter nodes based on information found in the - messages (e.g., the value of the Destination-Realm AVP Section 6.6). - This routing decision is performed using a list of supported realms - and known peers. This is known as the routing table, as is defined - further in Section 2.7. - - Relays may, for example, be used to aggregate requests from multiple - Network Access Servers (NASes) within a common geographical area - (Point of Presence, POP). The use of relays is advantageous since it - eliminates the need for NASes to be configured with the necessary - security information they would otherwise require to communicate with - Diameter servers in other realms. Likewise, this reduces the - configuration load on Diameter servers that would otherwise be - necessary when NASes are added, changed, or deleted. - - Relays modify Diameter messages by inserting and removing routing - information, but they do not modify any other portion of a message. - Relays SHOULD NOT maintain session state but MUST maintain - transaction state. - - +------+ ---------> +------+ ---------> +------+ - | | 1. Request | | 2. Request | | - | NAS | | DRL | | HMS | - | | 4. Answer | | 3. Answer | | - +------+ <--------- +------+ <--------- +------+ - example.net example.net example.com - - Figure 2: Relaying of Diameter messages - - The example provided in Figure 2 depicts a request issued from a NAS, - which is an access device, for the user [email protected]. Prior to - issuing the request, the NAS performs a Diameter route lookup, using - "example.com" as the key, and determines that the message is to be - relayed to a DRL, which is a Diameter relay. The DRL performs the - same route lookup as the NAS, and relays the message to the HMS, - which is example.com's home server. The HMS identifies that the - request can be locally supported (via the realm), processes the - authentication and/or authorization request, and replies with an - answer, which is routed back to the NAS using saved transaction - state. - - Since relays do not perform any application-level processing, they - provide relaying services for all Diameter applications; therefore, - they MUST advertise the Relay Application Id. -</pre> - -<p> -Requests are relayed by returning a <c>relay</c> tuple from a -&app_handle_request; callback.</p> - -<pre> - - - -Fajardo, et al. Standards Track [Page 30] - -RFC 6733 Diameter Base Protocol October 2012 - - -2.8.2. Proxy Agents - - Similar to relays, proxy agents route Diameter messages using the - Diameter routing table. However, they differ since they modify - messages to implement policy enforcement. This requires that proxies - maintain the state of their downstream peers (e.g., access devices) - to enforce resource usage, provide admission control, and provide - provisioning. - - Proxies may, for example, be used in call control centers or access - ISPs that provide outsourced connections; they can monitor the number - and type of ports in use and make allocation and admission decisions - according to their configuration. - - Since enforcing policies requires an understanding of the service - being provided, proxies MUST only advertise the Diameter applications - they support. -</pre> - -&nada; - -<pre> - -2.8.3. Redirect Agents - - Redirect agents are useful in scenarios where the Diameter routing - configuration needs to be centralized. An example is a redirect - agent that provides services to all members of a consortium, but does - not wish to be burdened with relaying all messages between realms. - This scenario is advantageous since it does not require that the - consortium provide routing updates to its members when changes are - made to a member's infrastructure. - - Since redirect agents do not relay messages, and only return an - answer with the information necessary for Diameter agents to - communicate directly, they do not modify messages. Since redirect - agents do not receive answer messages, they cannot maintain session - state. - - The example provided in Figure 3 depicts a request issued from the - access device, NAS, for the user [email protected]. The message is - forwarded by the NAS to its relay, DRL, which does not have a routing - entry in its Diameter routing table for example.com. The DRL has a - default route configured to DRD, which is a redirect agent that - returns a redirect notification to DRL, as well as the HMS' contact - information. Upon receipt of the redirect notification, the DRL - establishes a transport connection with the HMS, if one doesn't - already exist, and forwards the request to it. - - - - - - - - -Fajardo, et al. Standards Track [Page 31] - -RFC 6733 Diameter Base Protocol October 2012 - - - +------+ - | | - | DRD | - | | - +------+ - ^ | - 2. Request | | 3. Redirection - | | Notification - | v - +------+ ---------> +------+ ---------> +------+ - | | 1. Request | | 4. Request | | - | NAS | | DRL | | HMS | - | | 6. Answer | | 5. Answer | | - +------+ <--------- +------+ <--------- +------+ - example.net example.net example.com - - Figure 3: Redirecting a Diameter Message - - Since redirect agents do not perform any application-level - processing, they provide relaying services for all Diameter - applications; therefore, they MUST advertise the Relay Application - ID. -</pre> - -&nada; - -<pre> - -2.8.4. Translation Agents - - A translation agent is a device that provides translation between two - protocols (e.g., RADIUS<->Diameter, TACACS+<->Diameter). Translation - agents are likely to be used as aggregation servers to communicate - with a Diameter infrastructure, while allowing for the embedded - systems to be migrated at a slower pace. - - Given that the Diameter protocol introduces the concept of long-lived - authorized sessions, translation agents MUST be session stateful and - MUST maintain transaction state. - - Translation of messages can only occur if the agent recognizes the - application of a particular request; therefore, translation agents - MUST only advertise their locally supported applications. - - +------+ ---------> +------+ ---------> +------+ - | | RADIUS Request | | Diameter Request | | - | NAS | | TLA | | HMS | - | | RADIUS Answer | | Diameter Answer | | - +------+ <--------- +------+ <--------- +------+ - example.net example.net example.com - - Figure 4: Translation of RADIUS to Diameter -</pre> - -&nada; - -<pre> - - - - -Fajardo, et al. Standards Track [Page 32] - -RFC 6733 Diameter Base Protocol October 2012 - - -2.9. Diameter Path Authorization - - As noted in Section 2.2, Diameter provides transmission-level - security for each connection using TLS/TCP and DTLS/SCTP. Therefore, - each connection can be authenticated and can be replay and integrity - protected. - - In addition to authenticating each connection, the entire session - MUST also be authorized. Before initiating a connection, a Diameter - peer MUST check that its peers are authorized to act in their roles. - For example, a Diameter peer may be authentic, but that does not mean - that it is authorized to act as a Diameter server advertising a set - of Diameter applications. - - Prior to bringing up a connection, authorization checks are performed - at each connection along the path. Diameter capabilities negotiation - (CER/CEA) also MUST be carried out, in order to determine what - Diameter applications are supported by each peer. Diameter sessions - MUST be routed only through authorized nodes that have advertised - support for the Diameter application required by the session. - - As noted in Section 6.1.9, a relay or proxy agent MUST append a - Route-Record AVP to all requests forwarded. The AVP contains the - identity of the peer from which the request was received. - - The home Diameter server, prior to authorizing a session, MUST check - the Route-Record AVPs to make sure that the route traversed by the - request is acceptable. For example, administrators within the home - realm may not wish to honor requests that have been routed through an - untrusted realm. By authorizing a request, the home Diameter server - is implicitly indicating its willingness to engage in the business - transaction as specified by any contractual relationship between the - server and the previous hop. A DIAMETER_AUTHORIZATION_REJECTED error - message (see Section 7.1.5) is sent if the route traversed by the - request is unacceptable. - - A home realm may also wish to check that each accounting request - message corresponds to a Diameter response authorizing the session. - Accounting requests without corresponding authorization responses - SHOULD be subjected to further scrutiny, as should accounting - requests indicating a difference between the requested and provided - service. - - Forwarding of an authorization response is considered evidence of a - willingness to take on financial risk relative to the session. A - local realm may wish to limit this exposure, for example, by - establishing credit limits for intermediate realms and refusing to - accept responses that would violate those limits. By issuing an - - - -Fajardo, et al. Standards Track [Page 33] - -RFC 6733 Diameter Base Protocol October 2012 - - - accounting request corresponding to the authorization response, the - local realm implicitly indicates its agreement to provide the service - indicated in the authorization response. If the service cannot be - provided by the local realm, then a DIAMETER_UNABLE_TO_COMPLY error - message MUST be sent within the accounting request; a Diameter client - receiving an authorization response for a service that it cannot - perform MUST NOT substitute an alternate service and then send - accounting requests for the alternate service instead. -</pre> - -&nada; - -<pre> - -3. Diameter Header - - A summary of the Diameter header format is shown below. The fields - are transmitted in network byte order. - - 0 1 2 3 - 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - | Version | Message Length | - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - | Command Flags | Command Code | - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - | Application-ID | - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - | Hop-by-Hop Identifier | - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - | End-to-End Identifier | - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - | AVPs ... - +-+-+-+-+-+-+-+-+-+-+-+-+- -</pre> - -<p> -The Diameter Header is represented by the <c>diameter_header</c> -record defined in <c>diameter.hrl</c>. -The <c>diameter_packet</c> record contains a <c>header</c> field whose -value will be a decoded <c>#diameter_header{}</c> for incoming -messages passed to &app_handle_request; and &app_handle_answer; -callbacks. -In the case of outgoing messages, diameter and the relevant -dictionary populate the Diameter Header appropriately, although -&app_prepare_request; and &app_handle_request; callbacks can modify -header values. -(Which can be useful in test.)</p> - -<pre> - - Version - - This Version field MUST be set to 1 to indicate Diameter Version - 1. - - Message Length - - The Message Length field is three octets and indicates the length - of the Diameter message including the header fields and the padded - AVPs. Thus, the Message Length field is always a multiple of 4. - - Command Flags - - The Command Flags field is eight bits. The following bits are - assigned: - - - - - - -Fajardo, et al. Standards Track [Page 34] - -RFC 6733 Diameter Base Protocol October 2012 - - - 0 1 2 3 4 5 6 7 - +-+-+-+-+-+-+-+-+ - |R P E T r r r r| - +-+-+-+-+-+-+-+-+ - - R(equest) - - If set, the message is a request. If cleared, the message is - an answer. - - P(roxiable) - - If set, the message MAY be proxied, relayed, or redirected. If - cleared, the message MUST be locally processed. - - E(rror) - - If set, the message contains a protocol error, and the message - will not conform to the CCF described for this command. - Messages with the 'E' bit set are commonly referred to as error - messages. This bit MUST NOT be set in request messages (see - Section 7.2). - - T(Potentially retransmitted message) - - This flag is set after a link failover procedure, to aid the - removal of duplicate requests. It is set when resending - requests not yet acknowledged, as an indication of a possible - duplicate due to a link failure. This bit MUST be cleared when - sending a request for the first time; otherwise, the sender - MUST set this flag. Diameter agents only need to be concerned - about the number of requests they send based on a single - received request; retransmissions by other entities need not be - tracked. Diameter agents that receive a request with the T - flag set, MUST keep the T flag set in the forwarded request. - This flag MUST NOT be set if an error answer message (e.g., a - protocol error) has been received for the earlier message. It - can be set only in cases where no answer has been received from - the server for a request, and the request has been sent again. - This flag MUST NOT be set in answer messages. - - r(eserved) - - These flag bits are reserved for future use; they MUST be set - to zero and ignored by the receiver. -</pre> - -<p> -Reserved bits are set to 0 in outgoing messages.</p> - -<pre> - - - - - - -Fajardo, et al. Standards Track [Page 35] - -RFC 6733 Diameter Base Protocol October 2012 - - - Command Code - - The Command Code field is three octets and is used in order to - communicate the command associated with the message. The 24-bit - address space is managed by IANA (see Section 3.1). Command Code - values 16,777,214 and 16,777,215 (hexadecimal values FFFFFE- - FFFFFF) are reserved for experimental use (see Section 11.2). - - Application-ID - - Application-ID is four octets and is used to identify for which - application the message is applicable. The application can be an - authentication application, an accounting application, or a - vendor-specific application. - - The value of the Application-ID field in the header MUST be the - same as any relevant Application-Id AVPs contained in the message. - - Hop-by-Hop Identifier - - The Hop-by-Hop Identifier is an unsigned 32-bit integer field (in - network byte order) that aids in matching requests and replies. - The sender MUST ensure that the Hop-by-Hop Identifier in a request - is unique on a given connection at any given time, and it MAY - attempt to ensure that the number is unique across reboots. The - sender of an answer message MUST ensure that the Hop-by-Hop - Identifier field contains the same value that was found in the - corresponding request. The Hop-by-Hop Identifier is normally a - monotonically increasing number, whose start value was randomly - generated. An answer message that is received with an unknown - Hop-by-Hop Identifier MUST be discarded. - - End-to-End Identifier - - The End-to-End Identifier is an unsigned 32-bit integer field (in - network byte order) that is used to detect duplicate messages. - Upon reboot, implementations MAY set the high order 12 bits to - contain the low order 12 bits of current time, and the low order - 20 bits to a random value. Senders of request messages MUST - insert a unique identifier on each message. The identifier MUST - remain locally unique for a period of at least 4 minutes, even - across reboots. The originator of an answer message MUST ensure - that the End-to-End Identifier field contains the same value that - was found in the corresponding request. The End-to-End Identifier - MUST NOT be modified by Diameter agents of any kind. The - combination of the Origin-Host AVP (Section 6.3) and this field is - used to detect duplicates. Duplicate requests SHOULD cause the - same answer to be transmitted (modulo the Hop-by-Hop Identifier - - - -Fajardo, et al. Standards Track [Page 36] - -RFC 6733 Diameter Base Protocol October 2012 - - - field and any routing AVPs that may be present), and they MUST NOT - affect any state that was set when the original request was - processed. Duplicate answer messages that are to be locally - consumed (see Section 6.2) SHOULD be silently discarded. - - AVPs - - AVPs are a method of encapsulating information relevant to the - Diameter message. See Section 4 for more information on AVPs. -</pre> - -&nada; - -<pre> - -3.1. Command Codes - - Each command Request/Answer pair is assigned a Command Code, and the - sub-type (i.e., request or answer) is identified via the 'R' bit in - the Command Flags field of the Diameter header. - - Every Diameter message MUST contain a Command Code in its header's - Command Code field, which is used to determine the action that is to - be taken for a particular message. The following Command Codes are - defined in the Diameter base protocol: - - Section - Command Name Abbrev. Code Reference - -------------------------------------------------------- - Abort-Session-Request ASR 274 8.5.1 - Abort-Session-Answer ASA 274 8.5.2 - Accounting-Request ACR 271 9.7.1 - Accounting-Answer ACA 271 9.7.2 - Capabilities-Exchange- CER 257 5.3.1 - Request - Capabilities-Exchange- CEA 257 5.3.2 - Answer - Device-Watchdog-Request DWR 280 5.5.1 - Device-Watchdog-Answer DWA 280 5.5.2 - Disconnect-Peer-Request DPR 282 5.4.1 - Disconnect-Peer-Answer DPA 282 5.4.2 - Re-Auth-Request RAR 258 8.3.1 - Re-Auth-Answer RAA 258 8.3.2 - Session-Termination- STR 275 8.4.1 - Request - Session-Termination- STA 275 8.4.2 - Answer -</pre> - -<p> -These messages are all defined in diameter's implementation of the -common dictionary in modules <c>diameter_gen_base_rfc6733</c> and -<c>diameter_gen_base_rfc3588</c>. -Corresponding record definitions are found in -<c>diameter_gen_base_rfc6733.hrl</c> and -<c>diameter_gen_base_rfc3588.hrl</c>.</p> - -<pre> - - - - - - - - - -Fajardo, et al. Standards Track [Page 37] - -RFC 6733 Diameter Base Protocol October 2012 - - -3.2. Command Code Format Specification - - Every Command Code defined MUST include a corresponding Command Code - Format (CCF) specification, which is used to define the AVPs that - MUST or MAY be present when sending the message. The following ABNF - specifies the CCF used in the definition: -</pre> - -<p> -The CCF is what is specified in the <c>@messages</c> section of the -&man_dict; format, except as noted below.</p> - -<pre> - - command-def = "<" command-name ">" "::=" diameter-message -</pre> - -<p> -Angle brackets are currently not allowed here. -This was a change between RFC 3588 and RFC 6733: the former disallowed -them in the grammar but included them in its own command definitions.</p> - -<pre> - - command-name = diameter-name - - diameter-name = ALPHA *(ALPHA / DIGIT / "-") - - diameter-message = header *fixed *required *optional - - header = "<Diameter-Header:" command-id - [r-bit] [p-bit] [e-bit] [application-id]">" - - application-id = 1*DIGIT - - command-id = 1*DIGIT - ; The Command Code assigned to the command. - - r-bit = ", REQ" - ; If present, the 'R' bit in the Command - ; Flags is set, indicating that the message - ; is a request as opposed to an answer. - - p-bit = ", PXY" - ; If present, the 'P' bit in the Command - ; Flags is set, indicating that the message - ; is proxiable. - - e-bit = ", ERR" - ; If present, the 'E' bit in the Command - ; Flags is set, indicating that the answer - ; message contains a Result-Code AVP in - ; the "protocol error" class. - - fixed = [qual] "<" avp-spec ">" - ; Defines the fixed position of an AVP. - - required = [qual] "{" avp-spec "}" - ; The AVP MUST be present and can appear - ; anywhere in the message. - - - - - - -Fajardo, et al. Standards Track [Page 38] - -RFC 6733 Diameter Base Protocol October 2012 - - - optional = [qual] "[" avp-name "]" - ; The avp-name in the 'optional' rule cannot - ; evaluate to any AVP Name that is included - ; in a fixed or required rule. The AVP can - ; appear anywhere in the message. - ; - ; NOTE: "[" and "]" have a slightly different - ; meaning than in ABNF. These braces - ; cannot be used to express optional fixed rules - ; (such as an optional ICV at the end). To do - ; this, the convention is '0*1fixed'. - - qual = [min] "*" [max] - ; See ABNF conventions, RFC 5234, Section 4. - ; The absence of any qualifier depends on - ; whether it precedes a fixed, required, or - ; optional rule. If a fixed or required rule has - ; no qualifier, then exactly one such AVP MUST - ; be present. If an optional rule has no - ; qualifier, then 0 or 1 such AVP may be - ; present. If an optional rule has a qualifier, - ; then the value of min MUST be 0 if present. - - min = 1*DIGIT - ; The minimum number of times the element may - ; be present. If absent, the default value is 0 - ; for fixed and optional rules and 1 for - ; required rules. The value MUST be at least 1 - ; for required rules. - - max = 1*DIGIT - ; The maximum number of times the element may - ; be present. If absent, the default value is - ; infinity. A value of 0 implies the AVP MUST - ; NOT be present. - - avp-spec = diameter-name - ; The avp-spec has to be an AVP Name, defined - ; in the base or extended Diameter - ; specifications. - - avp-name = avp-spec / "AVP" - ; The string "AVP" stands for *any* arbitrary AVP - ; Name, not otherwise listed in that Command Code - ; definition. The inclusion of this string - ; is recommended for all CCFs to allow for - ; extensibility. - - - - -Fajardo, et al. Standards Track [Page 39] - -RFC 6733 Diameter Base Protocol October 2012 - - - The following is a definition of a fictitious Command Code: - - Example-Request ::= < Diameter Header: 9999999, REQ, PXY > - { User-Name } - 1* { Origin-Host } - * [ AVP ] -</pre> - -&nada; - -<pre> - -3.3. Diameter Command Naming Conventions - - Diameter command names typically includes one or more English words - followed by the verb "Request" or "Answer". Each English word is - delimited by a hyphen. A three-letter acronym for both the request - and answer is also normally provided. - - An example is a message set used to terminate a session. The command - name is Session-Terminate-Request and Session-Terminate-Answer, while - the acronyms are STR and STA, respectively. - - Both the request and the answer for a given command share the same - Command Code. The request is identified by the R(equest) bit in the - Diameter header set to one (1), to ask that a particular action be - performed, such as authorizing a user or terminating a session. Once - the receiver has completed the request, it issues the corresponding - answer, which includes a result code that communicates one of the - following: - - o The request was successful - - o The request failed - - o An additional request has to be sent to provide information the - peer requires prior to returning a successful or failed answer. - - o The receiver could not process the request, but provides - information about a Diameter peer that is able to satisfy the - request, known as redirect. - - Additional information, encoded within AVPs, may also be included in - answer messages. -</pre> - -<p> -The &man_dict; format places no requirement on the naming of commands.</p> - -<pre> - -4. Diameter AVPs - - Diameter AVPs carry specific authentication, accounting, - authorization, and routing information as well as configuration - details for the request and reply. - - - - - - -Fajardo, et al. Standards Track [Page 40] - -RFC 6733 Diameter Base Protocol October 2012 - - - Each AVP of type OctetString MUST be padded to align on a 32-bit - boundary, while other AVP types align naturally. A number of zero- - valued bytes are added to the end of the AVP Data field until a word - boundary is reached. The length of the padding is not reflected in - the AVP Length field. - -4.1. AVP Header - - The fields in the AVP header MUST be sent in network byte order. The - format of the header is: - - 0 1 2 3 - 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - | AVP Code | - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - |V M P r r r r r| AVP Length | - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - | Vendor-ID (opt) | - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - | Data ... - +-+-+-+-+-+-+-+-+ - - AVP Code - - The AVP Code, combined with the Vendor-Id field, identifies the - attribute uniquely. AVP numbers 1 through 255 are reserved for - reuse of RADIUS attributes, without setting the Vendor-Id field. - AVP numbers 256 and above are used for Diameter, which are - allocated by IANA (see Section 11.1.1). - - AVP Flags - - The AVP Flags field informs the receiver how each attribute must - be handled. New Diameter applications SHOULD NOT define - additional AVP Flag bits. However, note that new Diameter - applications MAY define additional bits within the AVP header, and - an unrecognized bit SHOULD be considered an error. The sender of - the AVP MUST set 'R' (reserved) bits to 0 and the receiver SHOULD - ignore all 'R' (reserved) bits. The 'P' bit has been reserved for - future usage of end-to-end security. At the time of writing, - there are no end-to-end security mechanisms specified; therefore, - the 'P' bit SHOULD be set to 0. - - The 'M' bit, known as the Mandatory bit, indicates whether the - receiver of the AVP MUST parse and understand the semantics of the - AVP including its content. The receiving entity MUST return an - appropriate error message if it receives an AVP that has the M-bit - - - -Fajardo, et al. Standards Track [Page 41] - -RFC 6733 Diameter Base Protocol October 2012 - - - set but does not understand it. An exception applies when the AVP - is embedded within a Grouped AVP. See Section 4.4 for details. - Diameter relay and redirect agents MUST NOT reject messages with - unrecognized AVPs. - - The 'M' bit MUST be set according to the rules defined in the - application specification that introduces or reuses this AVP. - Within a given application, the M-bit setting for an AVP is - defined either for all command types or for each command type. - - AVPs with the 'M' bit cleared are informational only; a receiver - that receives a message with such an AVP that is not supported, or - whose value is not supported, MAY simply ignore the AVP. - - The 'V' bit, known as the Vendor-Specific bit, indicates whether - the optional Vendor-ID field is present in the AVP header. When - set, the AVP Code belongs to the specific vendor code address - space. - - AVP Length - - The AVP Length field is three octets, and indicates the number of - octets in this AVP including the AVP Code field, AVP Length field, - AVP Flags field, Vendor-ID field (if present), and the AVP Data - field. If a message is received with an invalid attribute length, - the message MUST be rejected. - -4.1.1. Optional Header Elements - - The AVP header contains one optional field. This field is only - present if the respective bit-flag is enabled. - - Vendor-ID - - The Vendor-ID field is present if the 'V' bit is set in the AVP - Flags field. The optional four-octet Vendor-ID field contains the - IANA-assigned "SMI Network Management Private Enterprise Codes" - [ENTERPRISE] value, encoded in network byte order. Any vendors or - standardization organizations that are also treated like vendors - in the IANA-managed "SMI Network Management Private Enterprise - Codes" space wishing to implement a vendor-specific Diameter AVP - MUST use their own Vendor-ID along with their privately managed - AVP address space, guaranteeing that they will not collide with - any other vendor's vendor-specific AVP(s) or with future IETF - AVPs. - - - - - - -Fajardo, et al. Standards Track [Page 42] - -RFC 6733 Diameter Base Protocol October 2012 - - - A Vendor-ID value of zero (0) corresponds to the IETF-adopted AVP - values, as managed by IANA. Since the absence of the Vendor-ID - field implies that the AVP in question is not vendor specific, - implementations MUST NOT use the value of zero (0) for the - Vendor-ID field. - -4.2. Basic AVP Data Formats - - The Data field is zero or more octets and contains information - specific to the Attribute. The format and length of the Data field - is determined by the AVP Code and AVP Length fields. The format of - the Data field MUST be one of the following base data types or a data - type derived from the base data types. In the event that a new Basic - AVP Data Format is needed, a new version of this RFC MUST be created. - - OctetString - - The data contains arbitrary data of variable length. Unless - otherwise noted, the AVP Length field MUST be set to at least 8 - (12 if the 'V' bit is enabled). AVP values of this type that are - not a multiple of 4 octets in length are followed by the necessary - padding so that the next AVP (if any) will start on a 32-bit - boundary. - - Integer32 - - 32-bit signed value, in network byte order. The AVP Length field - MUST be set to 12 (16 if the 'V' bit is enabled). - - Integer64 - - 64-bit signed value, in network byte order. The AVP Length field - MUST be set to 16 (20 if the 'V' bit is enabled). - - Unsigned32 - - 32-bit unsigned value, in network byte order. The AVP Length - field MUST be set to 12 (16 if the 'V' bit is enabled). - - Unsigned64 - - 64-bit unsigned value, in network byte order. The AVP Length - field MUST be set to 16 (20 if the 'V' bit is enabled). - - - - - - - - -Fajardo, et al. Standards Track [Page 43] - -RFC 6733 Diameter Base Protocol October 2012 - - - Float32 - - This represents floating point values of single precision as - described by [FLOATPOINT]. The 32-bit value is transmitted in - network byte order. The AVP Length field MUST be set to 12 (16 if - the 'V' bit is enabled). - - Float64 - - This represents floating point values of double precision as - described by [FLOATPOINT]. The 64-bit value is transmitted in - network byte order. The AVP Length field MUST be set to 16 (20 if - the 'V' bit is enabled). - - Grouped - - The Data field is specified as a sequence of AVPs. These AVPs are - concatenated -- including their headers and padding -- in the - order in which they are specified and the result encapsulated in - the Data field. The AVP Length field is set to 8 (12 if the 'V' - bit is enabled) plus the total length of all included AVPs, - including their headers and padding. Thus, the AVP Length field - of an AVP of type Grouped is always a multiple of 4. - -4.3. Derived AVP Data Formats - - In addition to using the Basic AVP Data Formats, applications may - define data formats derived from the Basic AVP Data Formats. An - application that defines new Derived AVP Data Formats MUST include - them in a section titled "Derived AVP Data Formats", using the same - format as the definitions below. Each new definition MUST be either - defined or listed with a reference to the RFC that defines the - format. - -4.3.1. Common Derived AVP Data Formats - - The following are commonly used Derived AVP Data Formats. - - Address - - The Address format is derived from the OctetString Basic AVP - Format. It is a discriminated union representing, for example, a - 32-bit (IPv4) [RFC0791] or 128-bit (IPv6) [RFC4291] address, most - significant octet first. The first two octets of the Address AVP - represent the AddressType, which contains an Address Family, - defined in [IANAADFAM]. The AddressType is used to discriminate - the content and format of the remaining octets. - - - - -Fajardo, et al. Standards Track [Page 44] - -RFC 6733 Diameter Base Protocol October 2012 - - - Time - - The Time format is derived from the OctetString Basic AVP Format. - The string MUST contain four octets, in the same format as the - first four bytes are in the NTP timestamp format. The NTP - timestamp format is defined in Section 3 of [RFC5905]. - - This represents the number of seconds since 0h on 1 January 1900 - with respect to the Coordinated Universal Time (UTC). - - On 6h 28m 16s UTC, 7 February 2036, the time value will overflow. - Simple Network Time Protocol (SNTP) [RFC5905] describes a - procedure to extend the time to 2104. This procedure MUST be - supported by all Diameter nodes. - - UTF8String - - The UTF8String format is derived from the OctetString Basic AVP - Format. This is a human-readable string represented using the - ISO/IEC IS 10646-1 character set, encoded as an OctetString using - the UTF-8 transformation format [RFC3629]. - - Since additional code points are added by amendments to the 10646 - standard from time to time, implementations MUST be prepared to - encounter any code point from 0x00000001 to 0x7fffffff. Byte - sequences that do not correspond to the valid encoding of a code - point into UTF-8 charset or are outside this range are prohibited. - - The use of control codes SHOULD be avoided. When it is necessary - to represent a new line, the control code sequence CR LF SHOULD be - used. - - The use of leading or trailing white space SHOULD be avoided. - - For code points not directly supported by user interface hardware - or software, an alternative means of entry and display, such as - hexadecimal, MAY be provided. - - For information encoded in 7-bit US-ASCII, the UTF-8 charset is - identical to the US-ASCII charset. - - UTF-8 may require multiple bytes to represent a single character / - code point; thus, the length of a UTF8String in octets may be - different from the number of characters encoded. - - Note that the AVP Length field of an UTF8String is measured in - octets not characters. - - - - -Fajardo, et al. Standards Track [Page 45] - -RFC 6733 Diameter Base Protocol October 2012 - - - DiameterIdentity - - The DiameterIdentity format is derived from the OctetString Basic - AVP Format. - - DiameterIdentity = FQDN/Realm - - The DiameterIdentity value is used to uniquely identify either: - - * A Diameter node for purposes of duplicate connection and - routing loop detection. - - * A Realm to determine whether messages can be satisfied locally - or whether they must be routed or redirected. - - When a DiameterIdentity value is used to identify a Diameter node, - the contents of the string MUST be the Fully Qualified Domain Name - (FQDN) of the Diameter node. If multiple Diameter nodes run on - the same host, each Diameter node MUST be assigned a unique - DiameterIdentity. If a Diameter node can be identified by several - FQDNs, a single FQDN should be picked at startup and used as the - only DiameterIdentity for that node, whatever the connection on - which it is sent. In this document, note that DiameterIdentity is - in ASCII form in order to be compatible with existing DNS - infrastructure. See Appendix D for interactions between the - Diameter protocol and Internationalized Domain Names (IDNs). - - DiameterURI - - The DiameterURI MUST follow the Uniform Resource Identifiers (RFC - 3986) syntax [RFC3986] rules specified below: - - "aaa://" FQDN [ port ] [ transport ] [ protocol ] - - ; No transport security - - "aaas://" FQDN [ port ] [ transport ] [ protocol ] - - ; Transport security used - - FQDN = < Fully Qualified Domain Name > - - - - - - - - - - -Fajardo, et al. Standards Track [Page 46] - -RFC 6733 Diameter Base Protocol October 2012 - - - port = ":" 1*DIGIT - - ; One of the ports used to listen for - ; incoming connections. - ; If absent, the default Diameter port - ; (3868) is assumed if no transport - ; security is used and port 5658 when - ; transport security (TLS/TCP and DTLS/SCTP) - ; is used. - - transport = ";transport=" transport-protocol - - ; One of the transports used to listen - ; for incoming connections. If absent, - ; the default protocol is assumed to be TCP. - ; UDP MUST NOT be used when the aaa-protocol - ; field is set to diameter. - - transport-protocol = ( "tcp" / "sctp" / "udp" ) - - protocol = ";protocol=" aaa-protocol - - ; If absent, the default AAA protocol - ; is Diameter. - - aaa-protocol = ( "diameter" / "radius" / "tacacs+" ) - - The following are examples of valid Diameter host identities: - - aaa://host.example.com;transport=tcp - aaa://host.example.com:6666;transport=tcp - aaa://host.example.com;protocol=diameter - aaa://host.example.com:6666;protocol=diameter - aaa://host.example.com:6666;transport=tcp;protocol=diameter - aaa://host.example.com:1813;transport=udp;protocol=radius - - Enumerated - - The Enumerated format is derived from the Integer32 Basic AVP - Format. The definition contains a list of valid values and their - interpretation and is described in the Diameter application - introducing the AVP. - - - - - - - - - -Fajardo, et al. Standards Track [Page 47] - -RFC 6733 Diameter Base Protocol October 2012 - - - IPFilterRule - - The IPFilterRule format is derived from the OctetString Basic AVP - Format and uses the ASCII charset. The rule syntax is a modified - subset of ipfw(8) from FreeBSD. Packets may be filtered based on - the following information that is associated with it: - - Direction (in or out) - Source and destination IP address (possibly masked) - Protocol - Source and destination port (lists or ranges) - TCP flags - IP fragment flag - IP options - ICMP types - - Rules for the appropriate direction are evaluated in order, with the - first matched rule terminating the evaluation. Each packet is - evaluated once. If no rule matches, the packet is dropped if the - last rule evaluated was a permit, and passed if the last rule was a - deny. - - IPFilterRule filters MUST follow the format: - - action dir proto from src to dst [options] - - action permit - Allow packets that match the rule. - deny - Drop packets that match the rule. - - dir "in" is from the terminal, "out" is to the - terminal. - - proto An IP protocol specified by number. The "ip" - keyword means any protocol will match. - - src and dst <address/mask> [ports] - - The <address/mask> may be specified as: - ipno An IPv4 or IPv6 number in dotted- - quad or canonical IPv6 form. Only - this exact IP number will match the - rule. - - - - - - - - - -Fajardo, et al. Standards Track [Page 48] - -RFC 6733 Diameter Base Protocol October 2012 - - - ipno/bits An IP number as above with a mask - width of the form 192.0.2.10/24. In - this case, all IP numbers from - 192.0.2.0 to 192.0.2.255 will match. - The bit width MUST be valid for the - IP version, and the IP number MUST - NOT have bits set beyond the mask. - For a match to occur, the same IP - version must be present in the - packet that was used in describing - the IP address. To test for a - particular IP version, the bits part - can be set to zero. The keyword - "any" is 0.0.0.0/0 or the IPv6 - equivalent. The keyword "assigned" - is the address or set of addresses - assigned to the terminal. For IPv4, - a typical first rule is often "deny - in ip! assigned". - - The sense of the match can be inverted by - preceding an address with the not modifier (!), - causing all other addresses to be matched - instead. This does not affect the selection of - port numbers. - - With the TCP, UDP, and SCTP protocols, optional - ports may be specified as: - - {port/port-port}[,ports[,...]] - - The '-' notation specifies a range of ports - (including boundaries). - - Fragmented packets that have a non-zero offset - (i.e., not the first fragment) will never match - a rule that has one or more port - specifications. See the frag option for - details on matching fragmented packets. - - options: - frag Match if the packet is a fragment and this is not - the first fragment of the datagram. frag may not - be used in conjunction with either tcpflags or - TCP/UDP port specifications. - - - - - - -Fajardo, et al. Standards Track [Page 49] - -RFC 6733 Diameter Base Protocol October 2012 - - - ipoptions spec - Match if the IP header contains the comma-separated - list of options specified in spec. The - supported IP options are: - - ssrr (strict source route), lsrr (loose source - route), rr (record packet route), and ts - (timestamp). The absence of a particular option - may be denoted with a '!'. - - tcpoptions spec - Match if the TCP header contains the comma-separated - list of options specified in spec. The - supported TCP options are: - - mss (maximum segment size), window (tcp window - advertisement), sack (selective ack), ts (rfc1323 - timestamp), and cc (rfc1644 t/tcp connection - count). The absence of a particular option may - be denoted with a '!'. - - established - TCP packets only. Match packets that have the RST - or ACK bits set. - - setup TCP packets only. Match packets that have the SYN - bit set but no ACK bit. - - - tcpflags spec - TCP packets only. Match if the TCP header - contains the comma-separated list of flags - specified in spec. The supported TCP flags are: - - fin, syn, rst, psh, ack, and urg. The absence of a - particular flag may be denoted with a '!'. A rule - that contains a tcpflags specification can never - match a fragmented packet that has a non-zero - offset. See the frag option for details on - matching fragmented packets. - - icmptypes types - ICMP packets only. Match if the ICMP type is in - the list types. The list may be specified as any - combination of ranges or individual types - separated by commas. Both the numeric values and - the symbolic values listed below can be used. The - supported ICMP types are: - - - -Fajardo, et al. Standards Track [Page 50] - -RFC 6733 Diameter Base Protocol October 2012 - - - echo reply (0), destination unreachable (3), - source quench (4), redirect (5), echo request - (8), router advertisement (9), router - solicitation (10), time-to-live exceeded (11), IP - header bad (12), timestamp request (13), - timestamp reply (14), information request (15), - information reply (16), address mask request (17), - and address mask reply (18). - - There is one kind of packet that the access device MUST always - discard, that is an IP fragment with a fragment offset of one. This - is a valid packet, but it only has one use, to try to circumvent - firewalls. - - An access device that is unable to interpret or apply a deny rule - MUST terminate the session. An access device that is unable to - interpret or apply a permit rule MAY apply a more restrictive rule. - An access device MAY apply deny rules of its own before the supplied - rules, for example to protect the access device owner's - infrastructure. - -4.4. Grouped AVP Values - - The Diameter protocol allows AVP values of type 'Grouped'. This - implies that the Data field is actually a sequence of AVPs. It is - possible to include an AVP with a Grouped type within a Grouped type, - that is, to nest them. AVPs within an AVP of type Grouped have the - same padding requirements as non-Grouped AVPs, as defined in - Section 4.4. - - The AVP Code numbering space of all AVPs included in a Grouped AVP is - the same as for non-Grouped AVPs. Receivers of a Grouped AVP that - does not have the 'M' (mandatory) bit set and one or more of the - encapsulated AVPs within the group has the 'M' (mandatory) bit set - MAY simply be ignored if the Grouped AVP itself is unrecognized. The - rule applies even if the encapsulated AVP with its 'M' (mandatory) - bit set is further encapsulated within other sub-groups, i.e., other - Grouped AVPs embedded within the Grouped AVP. - - Every Grouped AVP definition MUST include a corresponding grammar, - using ABNF [RFC5234] (with modifications), as defined below. - - grouped-avp-def = "<" name ">" "::=" avp - - name-fmt = ALPHA *(ALPHA / DIGIT / "-") - - - - - - -Fajardo, et al. Standards Track [Page 51] - -RFC 6733 Diameter Base Protocol October 2012 - - - name = name-fmt - ; The name has to be the name of an AVP, - ; defined in the base or extended Diameter - ; specifications. - - avp = header *fixed *required *optional - - header = "<" "AVP-Header:" avpcode [vendor] ">" - - avpcode = 1*DIGIT - ; The AVP Code assigned to the Grouped AVP. - - vendor = 1*DIGIT - ; The Vendor-ID assigned to the Grouped AVP. - ; If absent, the default value of zero is - ; used. - -4.4.1. Example AVP with a Grouped Data Type - - The Example-AVP (AVP Code 999999) is of type Grouped and is used to - clarify how Grouped AVP values work. The Grouped Data field has the - following CCF grammar: - - Example-AVP ::= < AVP Header: 999999 > - { Origin-Host } - 1*{ Session-Id } - *[ AVP ] - - An Example-AVP with Grouped Data follows. - - The Origin-Host AVP (Section 6.3) is required. In this case: - - Origin-Host = "example.com". - - One or more Session-Ids must follow. Here there are two: - - Session-Id = - "grump.example.com:33041;23432;893;0AF3B81" - - Session-Id = - "grump.example.com:33054;23561;2358;0AF3B82" - - - - - - - - - - -Fajardo, et al. Standards Track [Page 52] - -RFC 6733 Diameter Base Protocol October 2012 - - - 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 hexadecimal form - since the format of these AVPs is not known at the time of definition - of the Example-AVP group nor (likely) at the time when the example - instance of this AVP is interpreted -- except by Diameter - implementations that support the same set of AVPs. The encoding - example illustrates how padding is used and how length fields are - calculated. Also, note that AVPs may be present in the Grouped AVP - value that the receiver cannot interpret (here, the Recover-Policy - and Futuristic-Acct-Record AVPs). The length of the Example-AVP is - the sum of all the length of the member AVPs, including their - padding, plus the Example-AVP header size. - - - - - - - - - - - - - - - - - - - - - - -Fajardo, et al. Standards Track [Page 53] - -RFC 6733 Diameter Base Protocol October 2012 - - - This AVP would be encoded as follows: - - 0 1 2 3 4 5 6 7 - +-------+-------+-------+-------+-------+-------+-------+-------+ - 0 | Example AVP Header (AVP Code = 999999), Length = 496 | - +-------+-------+-------+-------+-------+-------+-------+-------+ - 8 | Origin-Host AVP Header (AVP Code = 264), Length = 19 | - +-------+-------+-------+-------+-------+-------+-------+-------+ - 16 | 'e' | 'x' | 'a' | 'm' | 'p' | 'l' | 'e' | '.' | - +-------+-------+-------+-------+-------+-------+-------+-------+ - 24 | 'c' | 'o' | 'm' |Padding| Session-Id AVP Header | - +-------+-------+-------+-------+-------+-------+-------+-------+ - 32 | (AVP Code = 263), Length = 49 | 'g' | 'r' | 'u' | 'm' | - +-------+-------+-------+-------+-------+-------+-------+-------+ - . . . - +-------+-------+-------+-------+-------+-------+-------+-------+ - 72 | 'F' | '3' | 'B' | '8' | '1' |Padding|Padding|Padding| - +-------+-------+-------+-------+-------+-------+-------+-------+ - 80 | Session-Id AVP Header (AVP Code = 263), Length = 50 | - +-------+-------+-------+-------+-------+-------+-------+-------+ - 88 | 'g' | 'r' | 'u' | 'm' | 'p' | '.' | 'e' | 'x' | - +-------+-------+-------+-------+-------+-------+-------+-------+ - . . . - +-------+-------+-------+-------+-------+-------+-------+-------+ - 120| '5' | '8' | ';' | '0' | 'A' | 'F' | '3' | 'B' | - +-------+-------+-------+-------+-------+-------+-------+-------+ - 128| '8' | '2' |Padding|Padding| Recovery-Policy Header (AVP | - +-------+-------+-------+-------+-------+-------+-------+-------+ - 136| Code = 8341), Length = 223 | 0x21 | 0x63 | 0xbc | 0x1d | - +-------+-------+-------+-------+-------+-------+-------+-------+ - 144| 0x0a | 0xd8 | 0x23 | 0x71 | 0xf6 | 0xbc | 0x09 | 0x48 | - +-------+-------+-------+-------+-------+-------+-------+-------+ - . . . - +-------+-------+-------+-------+-------+-------+-------+-------+ - 352| 0x8c | 0x7f | 0x92 |Padding| Futuristic-Acct-Record Header | - +-------+-------+-------+-------+-------+-------+-------+-------+ - 328|(AVP Code = 15930),Length = 137| 0xfe | 0x19 | 0xda | 0x58 | - +-------+-------+-------+-------+-------+-------+-------+-------+ - 336| 0x02 | 0xac | 0xd9 | 0x8b | 0x07 | 0xa5 | 0xb8 | 0xc6 | - +-------+-------+-------+-------+-------+-------+-------+-------+ - . . . - +-------+-------+-------+-------+-------+-------+-------+-------+ - 488| 0xe4 | 0x99 | 0x68 | 0xf8 | 0x41 |Padding|Padding|Padding| - +-------+-------+-------+-------+-------+-------+-------+-------+ - - - - - - - -Fajardo, et al. Standards Track [Page 54] - -RFC 6733 Diameter Base Protocol October 2012 - - -4.5. Diameter Base Protocol AVPs - - The following table describes the Diameter AVPs defined in the base - protocol, their AVP Code values, types, and possible flag values. - - Due to space constraints, the short form DiamIdent is used to - represent DiameterIdentity. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Fajardo, et al. Standards Track [Page 55] - -RFC 6733 Diameter Base Protocol October 2012 - - - +----------+ - | AVP Flag | - | rules | - |----+-----| - AVP Section | |MUST | - Attribute Name Code Defined Data Type |MUST| NOT | - -----------------------------------------|----+-----| - Acct- 85 9.8.2 Unsigned32 | M | V | - Interim-Interval | | | - Accounting- 483 9.8.7 Enumerated | M | V | - Realtime-Required | | | - Acct- 50 9.8.5 UTF8String | M | V | - Multi-Session-Id | | | - Accounting- 485 9.8.3 Unsigned32 | M | V | - Record-Number | | | - Accounting- 480 9.8.1 Enumerated | M | V | - Record-Type | | | - Acct- 44 9.8.4 OctetString| M | V | - Session-Id | | | - Accounting- 287 9.8.6 Unsigned64 | M | V | - Sub-Session-Id | | | - Acct- 259 6.9 Unsigned32 | M | V | - Application-Id | | | - Auth- 258 6.8 Unsigned32 | M | V | - Application-Id | | | - Auth-Request- 274 8.7 Enumerated | M | V | - Type | | | - Authorization- 291 8.9 Unsigned32 | M | V | - Lifetime | | | - Auth-Grace- 276 8.10 Unsigned32 | M | V | - Period | | | - Auth-Session- 277 8.11 Enumerated | M | V | - State | | | - Re-Auth-Request- 285 8.12 Enumerated | M | V | - Type | | | - Class 25 8.20 OctetString| M | V | - Destination-Host 293 6.5 DiamIdent | M | V | - Destination- 283 6.6 DiamIdent | M | V | - Realm | | | - Disconnect-Cause 273 5.4.3 Enumerated | M | V | - Error-Message 281 7.3 UTF8String | | V,M | - Error-Reporting- 294 7.4 DiamIdent | | V,M | - Host | | | - Event-Timestamp 55 8.21 Time | M | V | - Experimental- 297 7.6 Grouped | M | V | - Result | | | - -----------------------------------------|----+-----| - - - - -Fajardo, et al. Standards Track [Page 56] - -RFC 6733 Diameter Base Protocol October 2012 - - - +----------+ - | AVP Flag | - | rules | - |----+-----| - AVP Section | |MUST | - Attribute Name Code Defined Data Type |MUST| NOT | - -----------------------------------------|----+-----| - Experimental- 298 7.7 Unsigned32 | M | V | - Result-Code | | | - Failed-AVP 279 7.5 Grouped | M | V | - Firmware- 267 5.3.4 Unsigned32 | | V,M | - Revision | | | - Host-IP-Address 257 5.3.5 Address | M | V | - Inband-Security | M | V | - -Id 299 6.10 Unsigned32 | | | - Multi-Round- 272 8.19 Unsigned32 | M | V | - Time-Out | | | - Origin-Host 264 6.3 DiamIdent | M | V | - Origin-Realm 296 6.4 DiamIdent | M | V | - Origin-State-Id 278 8.16 Unsigned32 | M | V | - Product-Name 269 5.3.7 UTF8String | | V,M | - Proxy-Host 280 6.7.3 DiamIdent | M | V | - Proxy-Info 284 6.7.2 Grouped | M | V | - Proxy-State 33 6.7.4 OctetString| M | V | - Redirect-Host 292 6.12 DiamURI | M | V | - Redirect-Host- 261 6.13 Enumerated | M | V | - Usage | | | - Redirect-Max- 262 6.14 Unsigned32 | M | V | - Cache-Time | | | - Result-Code 268 7.1 Unsigned32 | M | V | - Route-Record 282 6.7.1 DiamIdent | M | V | - Session-Id 263 8.8 UTF8String | M | V | - Session-Timeout 27 8.13 Unsigned32 | M | V | - Session-Binding 270 8.17 Unsigned32 | M | V | - Session-Server- 271 8.18 Enumerated | M | V | - Failover | | | - Supported- 265 5.3.6 Unsigned32 | M | V | - Vendor-Id | | | - Termination- 295 8.15 Enumerated | M | V | - Cause | | | - User-Name 1 8.14 UTF8String | M | V | - Vendor-Id 266 5.3.3 Unsigned32 | M | V | - Vendor-Specific- 260 6.11 Grouped | M | V | - Application-Id | | | - -----------------------------------------|----+-----| - - - - - - -Fajardo, et al. Standards Track [Page 57] - -RFC 6733 Diameter Base Protocol October 2012 - - -5. Diameter Peers - - This section describes how Diameter nodes establish connections and - communicate with peers. - -5.1. Peer Connections - - Connections between diameter peers are established using their valid - DiameterIdentity. A Diameter node initiating a connection to a peer - MUST know the peer's DiameterIdentity. Methods for discovering a - Diameter peer can be found in Section 5.2. - - Although a Diameter node may have many possible peers with which it - is able to communicate, it may not be economical to have an - established connection to all of them. At a minimum, a Diameter node - SHOULD have an established connection with two peers per realm, known - as the primary and secondary peers. Of course, a node MAY have - additional connections, if it is deemed necessary. Typically, all - messages for a realm are sent to the primary peer but, in the event - that failover procedures are invoked, any pending requests are sent - to the secondary peer. However, implementations are free to load - balance requests between a set of peers. - - Note that a given peer MAY act as a primary for a given realm while - acting as a secondary for another realm. - - When a peer is deemed suspect, which could occur for various reasons, - including not receiving a DWA within an allotted time frame, no new - requests should be forwarded to the peer, but failover procedures are - invoked. When an active peer is moved to this mode, additional - connections SHOULD be established to ensure that the necessary number - of active connections exists. - - There are two ways that a peer is removed from the suspect peer list: - - 1. The peer is no longer reachable, causing the transport connection - to be shut down. The peer is moved to the closed state. - - 2. Three watchdog messages are exchanged with accepted round-trip - times, and the connection to the peer is considered stabilized. - - In the event the peer being removed is either the primary or - secondary, an alternate peer SHOULD replace the deleted peer and - assume the role of either primary or secondary. - - - - - - - -Fajardo, et al. Standards Track [Page 58] - -RFC 6733 Diameter Base Protocol October 2012 - - -5.2. Diameter Peer Discovery - - Allowing for dynamic Diameter agent discovery makes possible simpler - and more robust deployment of Diameter services. In order to promote - interoperable implementations of Diameter peer discovery, the - following mechanisms (manual configuration and DNS) are described. - These are based on existing IETF standards. Both mechanisms MUST be - supported by all Diameter implementations; either MAY be used. - - There are two cases where Diameter peer discovery may be performed. - The first is when a Diameter client needs to discover a first-hop - Diameter agent. The second case is when a Diameter agent needs to - discover another agent for further handling of a Diameter operation. - In both cases, the following 'search order' is recommended: - - 1. The Diameter implementation consults its list of statically - (manually) configured Diameter agent locations. These will be - used if they exist and respond. - - 2. The Diameter implementation performs a NAPTR query for a server - in a particular realm. The Diameter implementation has to know, - in advance, in which realm to look for a Diameter agent. This - could be deduced, for example, from the 'realm' in an NAI on - which a Diameter implementation needed to perform a Diameter - operation. - - The NAPTR usage in Diameter follows the S-NAPTR DDDS application - [RFC3958] in which the SERVICE field includes tags for the - desired application and supported application protocol. The - application service tag for a Diameter application is 'aaa' and - the supported application protocol tags are 'diameter.tcp', - 'diameter.sctp', 'diameter.dtls', or 'diameter.tls.tcp' - [RFC6408]. - - The client can follow the resolution process defined by the - S-NAPTR DDDS [RFC3958] application to find a matching SRV, A, or - AAAA record of a suitable peer. The domain suffixes in the NAPTR - replacement field SHOULD match the domain of the original query. - An example can be found in Appendix B. - - 3. If no NAPTR records are found, the requester directly queries for - one of the following SRV records: for Diameter over TCP, use - "_diameter._tcp.realm"; for Diameter over TLS, use - "_diameters._tcp.realm"; for Diameter over SCTP, use - "_diameter._sctp.realm"; for Diameter over DTLS, use - "_diameters._sctp.realm". If SRV records are found, then the - requester can perform address record query (A RR's and/or AAAA - - - - -Fajardo, et al. Standards Track [Page 59] - -RFC 6733 Diameter Base Protocol October 2012 - - - RR's) for the target hostname specified in the SRV records - following the rules given in [RFC2782]. If no SRV records are - found, the requester gives up. - - If the server is using a site certificate, the domain name in the - NAPTR 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/TCP and DTLS/SCTP or Internet Key Exchange Protocol (IKE) - exchange. Similarly, the domain name in the SRV query and the domain - name in the target in the SRV record MUST both be valid based on the - same site certificate. Otherwise, an attacker could modify the DNS - records to contain replacement values in a different domain, and the - client could not validate whether this was the desired behavior or - the result of an attack. - - Also, the Diameter peer MUST check to make sure that the discovered - peers are authorized to act in its role. Authentication via IKE or - TLS/TCP and DTLS/SCTP, or validation of DNS RRs via DNSSEC is not - sufficient to conclude this. For example, a web server may have - obtained a valid TLS/TCP and DTLS/SCTP certificate, and secured RRs - may be included in the DNS, but this does not imply that it is - authorized to act as a Diameter server. - - Authorization can be achieved, for example, by the configuration of a - Diameter server Certification Authority (CA). The server CA issues a - certificate to the Diameter server, which includes an Object - Identifier (OID) to indicate the subject is a Diameter server in the - Extended Key Usage extension [RFC5280]. This certificate is then - used during TLS/TCP, DTLS/SCTP, or IKE security negotiation. - However, note that, at the time of writing, no Diameter server - Certification Authorities exist. - - A dynamically discovered peer causes an entry in the peer table (see - Section 2.6) to be created. Note that entries created via DNS MUST - expire (or be refreshed) within the DNS Time to Live (TTL). If a - peer is discovered outside of the local realm, a routing table entry - (see Section 2.7) for the peer's realm is created. The routing table - entry's expiration MUST match the peer's expiration value. - -5.3. Capabilities Exchange - - When two Diameter peers establish a transport connection, they MUST - exchange the Capabilities Exchange messages, as specified in the peer - state machine (see Section 5.6). This message allows the discovery - of a peer's identity and its capabilities (protocol version number, - the identifiers of supported Diameter applications, security - mechanisms, etc.). - - - - -Fajardo, et al. Standards Track [Page 60] - -RFC 6733 Diameter Base Protocol October 2012 - - - The receiver only issues commands to its peers that have advertised - support for the Diameter application that defines the command. A - Diameter node MUST cache the supported Application Ids in order to - ensure that unrecognized commands and/or AVPs are not unnecessarily - sent to a peer. - - A receiver of a Capabilities-Exchange-Request (CER) message that does - not have any applications in common with the sender MUST return a - Capabilities-Exchange-Answer (CEA) with the Result-Code AVP set to - DIAMETER_NO_COMMON_APPLICATION and SHOULD disconnect the transport - layer connection. Note that receiving a CER or CEA from a peer - advertising itself as a relay (see Section 2.4) MUST be interpreted - as having common applications with the peer. - - The receiver of the Capabilities-Exchange-Request (CER) MUST - determine common applications by computing the intersection of its - own set of supported Application Ids against all of the - Application-Id AVPs (Auth-Application-Id, Acct-Application-Id, and - Vendor-Specific-Application-Id) present in the CER. The value of the - Vendor-Id AVP in the Vendor-Specific-Application-Id MUST NOT be used - during computation. The sender of the Capabilities-Exchange-Answer - (CEA) SHOULD include all of its supported applications as a hint to - the receiver regarding all of its application capabilities. - - Diameter implementations SHOULD first attempt to establish a TLS/TCP - and DTLS/SCTP connection prior to the CER/CEA exchange. This - protects the capabilities information of both peers. To support - older Diameter implementations that do not fully conform to this - document, the transport security MAY still be negotiated via an - Inband-Security AVP. In this case, the receiver of a Capabilities- - Exchange-Request (CER) message that does not have any security - mechanisms in common with the sender MUST return a Capabilities- - Exchange-Answer (CEA) with the Result-Code AVP set to - DIAMETER_NO_COMMON_SECURITY and SHOULD disconnect the transport layer - connection. - - CERs received from unknown peers MAY be silently discarded, or a CEA - MAY be issued with the Result-Code AVP set to DIAMETER_UNKNOWN_PEER. - In both cases, the transport connection is closed. If the local - policy permits receiving CERs from unknown hosts, a successful CEA - MAY be returned. If a CER from an unknown peer is answered with a - successful CEA, the lifetime of the peer entry is equal to the - lifetime of the transport connection. In case of a transport - failure, all the pending transactions destined to the unknown peer - can be discarded. - - The CER and CEA messages MUST NOT be proxied, redirected, or relayed. - - - - -Fajardo, et al. Standards Track [Page 61] - -RFC 6733 Diameter Base Protocol October 2012 - - - Since the CER/CEA messages cannot be proxied, it is still possible - that an upstream agent will receive a message for which it has no - available peers to handle the application that corresponds to the - Command Code. In such instances, the 'E' bit is set in the answer - message (Section 7) with the Result-Code AVP set to - DIAMETER_UNABLE_TO_DELIVER to inform the downstream agent to take - action (e.g., re-routing request to an alternate peer). - - With the exception of the Capabilities-Exchange-Request message, a - message of type Request that includes the Auth-Application-Id or - Acct-Application-Id AVPs, or a message with an application-specific - Command Code MAY only be forwarded to a host that has explicitly - advertised support for the application (or has advertised the Relay - Application Id). - -5.3.1. Capabilities-Exchange-Request - - The Capabilities-Exchange-Request (CER), indicated by the Command - Code set to 257 and the Command Flags' 'R' bit set, is sent to - exchange local capabilities. Upon detection of a transport failure, - this message MUST NOT be sent to an alternate peer. - - When Diameter is run over SCTP [RFC4960] or DTLS/SCTP [RFC6083], - which allow for connections to span multiple interfaces and multiple - IP addresses, the Capabilities-Exchange-Request message MUST contain - one Host-IP-Address AVP for each potential IP address that MAY be - locally used when transmitting Diameter messages. - - Message Format - - <CER> ::= < Diameter Header: 257, REQ > - { Origin-Host } - { Origin-Realm } - 1* { Host-IP-Address } - { Vendor-Id } - { Product-Name } - [ Origin-State-Id ] - * [ Supported-Vendor-Id ] - * [ Auth-Application-Id ] - * [ Inband-Security-Id ] - * [ Acct-Application-Id ] - * [ Vendor-Specific-Application-Id ] - [ Firmware-Revision ] - * [ AVP ] - - - - - - - -Fajardo, et al. Standards Track [Page 62] - -RFC 6733 Diameter Base Protocol October 2012 - - -5.3.2. Capabilities-Exchange-Answer - - The Capabilities-Exchange-Answer (CEA), indicated by the Command Code - set to 257 and the Command Flags' 'R' bit cleared, is sent in - response to a CER message. - - When Diameter is run over SCTP [RFC4960] or DTLS/SCTP [RFC6083], - which allow connections to span multiple interfaces, hence, multiple - IP addresses, the Capabilities-Exchange-Answer message MUST contain - one Host-IP-Address AVP for each potential IP address that MAY be - locally used when transmitting Diameter messages. - - Message Format - - <CEA> ::= < Diameter Header: 257 > - { Result-Code } - { Origin-Host } - { Origin-Realm } - 1* { Host-IP-Address } - { Vendor-Id } - { Product-Name } - [ Origin-State-Id ] - [ Error-Message ] - [ Failed-AVP ] - * [ Supported-Vendor-Id ] - * [ Auth-Application-Id ] - * [ Inband-Security-Id ] - * [ Acct-Application-Id ] - * [ Vendor-Specific-Application-Id ] - [ Firmware-Revision ] - * [ AVP ] - -5.3.3. Vendor-Id AVP - - The Vendor-Id AVP (AVP Code 266) is of type Unsigned32 and contains - the IANA "SMI Network Management Private Enterprise Codes" - [ENTERPRISE] value assigned to the Diameter Software vendor. It is - envisioned that the combination of the Vendor-Id, Product-Name - (Section 5.3.7), and Firmware-Revision (Section 5.3.4) AVPs may - provide useful debugging information. - - A Vendor-Id value of zero in the CER or CEA message is reserved and - indicates that this field is ignored. - - - - - - - - -Fajardo, et al. Standards Track [Page 63] - -RFC 6733 Diameter Base Protocol October 2012 - - -5.3.4. Firmware-Revision AVP - - The Firmware-Revision AVP (AVP Code 267) is of type Unsigned32 and is - used to inform a Diameter peer of the firmware revision of the - issuing device. - - For devices that do not have a firmware revision (general-purpose - computers running Diameter software modules, for instance), the - revision of the Diameter software module may be reported instead. - -5.3.5. Host-IP-Address AVP - - The Host-IP-Address AVP (AVP Code 257) is of type Address and is used - to inform a Diameter peer of the sender's IP address. All source - addresses that a Diameter node expects to use with SCTP [RFC4960] or - DTLS/SCTP [RFC6083] MUST be advertised in the CER and CEA messages by - including a Host-IP-Address AVP for each address. - -5.3.6. Supported-Vendor-Id AVP - - The Supported-Vendor-Id AVP (AVP Code 265) is of type Unsigned32 and - contains the IANA "SMI Network Management Private Enterprise Codes" - [ENTERPRISE] value assigned to a vendor other than the device vendor - but including the application vendor. This is used in the CER and - CEA messages in order to inform the peer that the sender supports (a - subset of) the Vendor-Specific AVPs defined by the vendor identified - in this AVP. The value of this AVP MUST NOT be set to zero. - Multiple instances of this AVP containing the same value SHOULD NOT - be sent. - -5.3.7. Product-Name AVP - - The Product-Name AVP (AVP Code 269) is of type UTF8String and - contains the vendor-assigned name for the product. The Product-Name - AVP SHOULD remain constant across firmware revisions for the same - product. - -5.4. Disconnecting Peer Connections - - When a Diameter node disconnects one of its transport connections, - its peer cannot know the reason for the disconnect and will most - likely assume that a connectivity problem occurred or that the peer - has rebooted. In these cases, the peer may periodically attempt to - reconnect, as stated in Section 2.1. In the event that the - disconnect was a result of either a shortage of internal resources or - simply that the node in question has no intentions of forwarding any - Diameter messages to the peer in the foreseeable future, a periodic - - - - -Fajardo, et al. Standards Track [Page 64] - -RFC 6733 Diameter Base Protocol October 2012 - - - connection request would not be welcomed. The Disconnection-Reason - AVP contains the reason the Diameter node issued the Disconnect-Peer- - Request message. - - The Disconnect-Peer-Request message is used by a Diameter node to - inform its peer of its intent to disconnect the transport layer and - that the peer shouldn't reconnect unless it has a valid reason to do - so (e.g., message to be forwarded). Upon receipt of the message, the - Disconnect-Peer-Answer message is returned, which SHOULD contain an - error if messages have recently been forwarded, and are likely in - flight, which would otherwise cause a race condition. - - The receiver of the Disconnect-Peer-Answer message initiates the - transport disconnect. The sender of the Disconnect-Peer-Answer - message should be able to detect the transport closure and clean up - the connection. - -5.4.1. Disconnect-Peer-Request - - The Disconnect-Peer-Request (DPR), indicated by the Command Code set - to 282 and the Command Flags' 'R' bit set, is sent to a peer to - inform it of its intentions to shut down the transport connection. - Upon detection of a transport failure, this message MUST NOT be sent - to an alternate peer. - - Message Format - - <DPR> ::= < Diameter Header: 282, REQ > - { Origin-Host } - { Origin-Realm } - { Disconnect-Cause } - * [ AVP ] - -5.4.2. Disconnect-Peer-Answer - - The Disconnect-Peer-Answer (DPA), indicated by the Command Code set - to 282 and the Command Flags' 'R' bit cleared, is sent as a response - to the Disconnect-Peer-Request message. Upon receipt of this - message, the transport connection is shut down. - - - - - - - - - - - - -Fajardo, et al. Standards Track [Page 65] - -RFC 6733 Diameter Base Protocol October 2012 - - - Message Format - - <DPA> ::= < Diameter Header: 282 > - { Result-Code } - { Origin-Host } - { Origin-Realm } - [ Error-Message ] - [ Failed-AVP ] - * [ AVP ] - - -5.4.3. Disconnect-Cause AVP - - The Disconnect-Cause AVP (AVP Code 273) is of type Enumerated. A - Diameter node MUST include this AVP in the Disconnect-Peer-Request - message to inform the peer of the reason for its intention to shut - down the transport connection. The following values are supported: - - REBOOTING 0 - A scheduled reboot is imminent. A receiver of a DPR with - above result code MAY attempt reconnection. - - BUSY 1 - The peer's internal resources are constrained, and it has - determined that the transport connection needs to be closed. - A receiver of a DPR with above result code SHOULD NOT attempt - reconnection. - - DO_NOT_WANT_TO_TALK_TO_YOU 2 - The peer has determined that it does not see a need for the - transport connection to exist, since it does not expect any - messages to be exchanged in the near future. A receiver of a - DPR with above result code SHOULD NOT attempt reconnection. - -5.5. Transport Failure Detection - - Given the nature of the Diameter protocol, it is recommended that - transport failures be detected as soon as possible. Detecting such - failures will minimize the occurrence of messages sent to unavailable - agents, resulting in unnecessary delays, and will provide better - failover performance. The Device-Watchdog-Request and Device- - Watchdog-Answer messages, defined in this section, are used to pro- - actively detect transport failures. - - - - - - - - -Fajardo, et al. Standards Track [Page 66] - -RFC 6733 Diameter Base Protocol October 2012 - - -5.5.1. Device-Watchdog-Request - - The Device-Watchdog-Request (DWR), indicated by the Command Code set - to 280 and the Command Flags' 'R' bit set, is sent to a peer when no - traffic has been exchanged between two peers (see Section 5.5.3). - Upon detection of a transport failure, this message MUST NOT be sent - to an alternate peer. - - Message Format - - <DWR> ::= < Diameter Header: 280, REQ > - { Origin-Host } - { Origin-Realm } - [ Origin-State-Id ] - * [ AVP ] - -5.5.2. Device-Watchdog-Answer - - The Device-Watchdog-Answer (DWA), indicated by the Command Code set - to 280 and the Command Flags' 'R' bit cleared, is sent as a response - to the Device-Watchdog-Request message. - - Message Format - - <DWA> ::= < Diameter Header: 280 > - { Result-Code } - { Origin-Host } - { Origin-Realm } - [ Error-Message ] - [ Failed-AVP ] - [ Origin-State-Id ] - * [ AVP ] - -5.5.3. Transport Failure Algorithm - - The transport failure algorithm is defined in [RFC3539]. All - Diameter implementations MUST support the algorithm defined in that - specification in order to be compliant to the Diameter base protocol. - -5.5.4. Failover and Failback Procedures - - In the event that a transport failure is detected with a peer, it is - necessary for all pending request messages to be forwarded to an - alternate agent, if possible. This is commonly referred to as - "failover". - - - - - - -Fajardo, et al. Standards Track [Page 67] - -RFC 6733 Diameter Base Protocol October 2012 - - - In order for a Diameter node to perform failover procedures, it is - necessary for the node to maintain a pending message queue for a - given peer. When an answer message is received, the corresponding - request is removed from the queue. The Hop-by-Hop Identifier field - is used to match the answer with the queued request. - - When a transport failure is detected, if possible, all messages in - the queue are sent to an alternate agent with the T flag set. On - booting a Diameter client or agent, the T flag is also set on any - remaining records in non-volatile storage that are still waiting to - be transmitted. An example of a case where it is not possible to - forward the message to an alternate server is when the message has a - fixed destination, and the unavailable peer is the message's final - destination (see Destination-Host AVP). Such an error requires that - the agent return an answer message with the 'E' bit set and the - Result-Code AVP set to DIAMETER_UNABLE_TO_DELIVER. - - It is important to note that multiple identical requests or answers - MAY be received as a result of a failover. The End-to-End Identifier - field in the Diameter header along with the Origin-Host AVP MUST be - used to identify duplicate messages. - - As described in Section 2.1, a connection request should be - periodically attempted with the failed peer in order to re-establish - the transport connection. Once a connection has been successfully - established, messages can once again be forwarded to the peer. This - is commonly referred to as "failback". - -5.6. Peer State Machine - - This section contains a finite state machine that MUST be observed by - all Diameter implementations. Each Diameter node MUST follow the - state machine described below when communicating with each peer. - Multiple actions are separated by commas, and may continue on - succeeding lines, as space requires. Similarly, state and next state - may also span multiple lines, as space requires. - - This state machine is closely coupled with the state machine - described in [RFC3539], which is used to open, close, failover, - probe, and reopen transport connections. In particular, note that - [RFC3539] requires the use of watchdog messages to probe connections. - For Diameter, DWR and DWA messages are to be used. - - The I- prefix is used to represent the initiator (connecting) - connection, while the R- prefix is used to represent the responder - (listening) connection. The lack of a prefix indicates that the - event or action is the same regardless of the connection on which the - event occurred. - - - -Fajardo, et al. Standards Track [Page 68] - -RFC 6733 Diameter Base Protocol October 2012 - - - The stable states that a state machine may be in are Closed, I-Open, - and R-Open; all other states are intermediate. Note that I-Open and - R-Open are equivalent except for whether the initiator or responder - transport connection is used for communication. - - A CER message is always sent on the initiating connection immediately - after the connection request is successfully completed. In the case - of an election, one of the two connections will shut down. The - responder connection will survive if the Origin-Host of the local - Diameter entity is higher than that of the peer; the initiator - connection will survive if the peer's Origin-Host is higher. All - subsequent messages are sent on the surviving connection. Note that - the results of an election on one peer are guaranteed to be the - inverse of the results on the other. - - For TLS/TCP and DTLS/SCTP usage, a TLS/TCP and DTLS/SCTP handshake - SHOULD begin when both ends are in the closed state prior to any - Diameter message exchanges. The TLS/TCP and DTLS/SCTP connection - SHOULD be established before sending any CER or CEA message to secure - and protect the capabilities information of both peers. The TLS/TCP - and DTLS/SCTP connection SHOULD be disconnected when the state - machine moves to the closed state. When connecting to responders - that do not conform to this document (i.e., older Diameter - implementations that are not prepared to received TLS/TCP and DTLS/ - SCTP connections in the closed state), the initial TLS/TCP and DTLS/ - SCTP connection attempt will fail. The initiator MAY then attempt to - connect via TCP or SCTP and initiate the TLS/TCP and DTLS/SCTP - handshake when both ends are in the open state. If the handshake is - successful, all further messages will be sent via TLS/TCP and DTLS/ - SCTP. If the handshake fails, both ends move to the closed state. - - The state machine constrains only the behavior of a Diameter - implementation as seen by Diameter peers through events on the wire. - - Any implementation that produces equivalent results is considered - compliant. - - - - - - - - - - - - - - - -Fajardo, et al. Standards Track [Page 69] - -RFC 6733 Diameter Base Protocol October 2012 - - - state event action next state - ----------------------------------------------------------------- - Closed Start I-Snd-Conn-Req Wait-Conn-Ack - R-Conn-CER R-Accept, R-Open - Process-CER, - R-Snd-CEA - - Wait-Conn-Ack I-Rcv-Conn-Ack I-Snd-CER Wait-I-CEA - I-Rcv-Conn-Nack Cleanup Closed - R-Conn-CER R-Accept, Wait-Conn-Ack/ - Process-CER Elect - Timeout Error Closed - - Wait-I-CEA I-Rcv-CEA Process-CEA I-Open - R-Conn-CER R-Accept, Wait-Returns - Process-CER, - Elect - I-Peer-Disc I-Disc Closed - I-Rcv-Non-CEA Error Closed - Timeout Error Closed - - Wait-Conn-Ack/ I-Rcv-Conn-Ack I-Snd-CER,Elect Wait-Returns - Elect I-Rcv-Conn-Nack R-Snd-CEA R-Open - R-Peer-Disc R-Disc Wait-Conn-Ack - R-Conn-CER R-Reject Wait-Conn-Ack/ - Elect - Timeout Error Closed - - Wait-Returns Win-Election I-Disc,R-Snd-CEA R-Open - I-Peer-Disc I-Disc, R-Open - R-Snd-CEA - I-Rcv-CEA R-Disc I-Open - R-Peer-Disc R-Disc Wait-I-CEA - R-Conn-CER R-Reject Wait-Returns - Timeout Error Closed - - R-Open Send-Message R-Snd-Message R-Open - R-Rcv-Message Process R-Open - R-Rcv-DWR Process-DWR, R-Open - R-Snd-DWA - R-Rcv-DWA Process-DWA R-Open - R-Conn-CER R-Reject R-Open - Stop R-Snd-DPR Closing - R-Rcv-DPR R-Snd-DPA Closing - R-Peer-Disc R-Disc Closed - - - - - - -Fajardo, et al. Standards Track [Page 70] - -RFC 6733 Diameter Base Protocol October 2012 - - - I-Open Send-Message I-Snd-Message I-Open - I-Rcv-Message Process I-Open - I-Rcv-DWR Process-DWR, I-Open - I-Snd-DWA - I-Rcv-DWA Process-DWA I-Open - R-Conn-CER R-Reject I-Open - Stop I-Snd-DPR Closing - I-Rcv-DPR I-Snd-DPA Closing - I-Peer-Disc I-Disc Closed - - Closing I-Rcv-DPA I-Disc Closed - R-Rcv-DPA R-Disc Closed - Timeout Error Closed - I-Peer-Disc I-Disc Closed - R-Peer-Disc R-Disc Closed - -5.6.1. Incoming Connections - - When a connection request is received from a Diameter peer, it is - not, in the general case, possible to know the identity of that peer - until a CER is received from it. This is because host and port - determine the identity of a Diameter peer; the source port of an - incoming connection is arbitrary. Upon receipt of a CER, the - identity of the connecting peer can be uniquely determined from the - Origin-Host. - - For this reason, a Diameter peer must employ logic separate from the - state machine to receive connection requests, accept them, and await - the CER. Once the CER arrives on a new connection, the Origin-Host - that identifies the peer is used to locate the state machine - associated with that peer, and the new connection and CER are passed - to the state machine as an R-Conn-CER event. - - The logic that handles incoming connections SHOULD close and discard - the connection if any message other than a CER arrives or if an - implementation-defined timeout occurs prior to receipt of CER. - - Because handling of incoming connections up to and including receipt - of a CER requires logic, separate from that of any individual state - machine associated with a particular peer, it is described separately - in this section rather than in the state machine above. - -5.6.2. Events - - Transitions and actions in the automaton are caused by events. In - this section, we will ignore the I- and R- prefixes, since the actual - event would be identical, but it would occur on one of two possible - connections. - - - -Fajardo, et al. Standards Track [Page 71] - -RFC 6733 Diameter Base Protocol October 2012 - - - Start The Diameter application has signaled that a - connection should be initiated with the peer. - - R-Conn-CER An acknowledgement is received stating that the - transport connection has been established, and the - associated CER has arrived. - - Rcv-Conn-Ack A positive acknowledgement is received confirming that - the transport connection is established. - - Rcv-Conn-Nack A negative acknowledgement was received stating that - the transport connection was not established. - - Timeout An application-defined timer has expired while waiting - for some event. - - Rcv-CER A CER message from the peer was received. - - Rcv-CEA A CEA message from the peer was received. - - Rcv-Non-CEA A message, other than a CEA, from the peer was - received. - - Peer-Disc A disconnection indication from the peer was received. - - Rcv-DPR A DPR message from the peer was received. - - Rcv-DPA A DPA message from the peer was received. - - Win-Election An election was held, and the local node was the - winner. - - Send-Message A message is to be sent. - - Rcv-Message A message other than CER, CEA, DPR, DPA, DWR, or DWA - was received. - - Stop The Diameter application has signaled that a - connection should be terminated (e.g., on system - shutdown). - -5.6.3. Actions - - Actions in the automaton are caused by events and typically indicate - the transmission of packets and/or an action to be taken on the - connection. In this section, we will ignore the I- and R- prefixes, - since the actual action would be identical, but it would occur on one - of two possible connections. - - - -Fajardo, et al. Standards Track [Page 72] - -RFC 6733 Diameter Base Protocol October 2012 - - - Snd-Conn-Req A transport connection is initiated with the peer. - - Accept The incoming connection associated with the R-Conn-CER - is accepted as the responder connection. - - Reject The incoming connection associated with the R-Conn-CER - is disconnected. - - Process-CER The CER associated with the R-Conn-CER is processed. - - Snd-CER A CER message is sent to the peer. - - Snd-CEA A CEA message is sent to the peer. - - Cleanup If necessary, the connection is shut down, and any - local resources are freed. - - Error The transport layer connection is disconnected, - either politely or abortively, in response to - an error condition. Local resources are freed. - - Process-CEA A received CEA is processed. - - Snd-DPR A DPR message is sent to the peer. - - Snd-DPA A DPA message is sent to the peer. - - Disc The transport layer connection is disconnected, - and local resources are freed. - - Elect An election occurs (see Section 5.6.4 for more - information). - - Snd-Message A message is sent. - - Snd-DWR A DWR message is sent. - - Snd-DWA A DWA message is sent. - - Process-DWR The DWR message is serviced. - - Process-DWA The DWA message is serviced. - - Process A message is serviced. - - - - - - - -Fajardo, et al. Standards Track [Page 73] - -RFC 6733 Diameter Base Protocol October 2012 - - -5.6.4. The Election Process - - The election is performed on the responder. The responder compares - the Origin-Host received in the CER with its own Origin-Host as two - streams of octets. If the local Origin-Host lexicographically - succeeds the received Origin-Host, a Win-Election event is issued - locally. Diameter identities are in ASCII form; therefore, the - lexical comparison is consistent with DNS case insensitivity, where - octets that fall in the ASCII range 'a' through 'z' MUST compare - equally to their uppercase counterparts between 'A' and 'Z'. See - Appendix D for interactions between the Diameter protocol and - Internationalized Domain Name (IDNs). - - The winner of the election MUST close the connection it initiated. - Historically, maintaining the responder side of a connection was more - efficient than maintaining the initiator side. However, current - practices makes this distinction irrelevant. - -6. Diameter Message Processing - - This section describes how Diameter requests and answers are created - and processed. - -6.1. Diameter Request Routing Overview - - A request is sent towards its final destination using one of the - following three combinations of the Destination-Realm and - Destination-Host AVPs: - - o A request that is not able to be proxied (such as a CER) MUST NOT - contain either Destination-Realm or Destination-Host AVPs. - - o A request that needs to be sent to a home server serving a - specific realm, but not to a specific server (such as the first - request of a series of round trips), MUST contain a Destination- - Realm AVP but MUST NOT contain a Destination-Host AVP. For - Diameter clients, the value of the Destination-Realm AVP MAY be - extracted from the User-Name AVP, or other methods. - - o Otherwise, a request that needs to be sent to a specific home - server among those serving a given realm MUST contain both the - Destination-Realm and Destination-Host AVPs. - - The Destination-Host AVP is used as described above when the - destination of the request is fixed, which includes: - - o Authentication requests that span multiple round trips. - - - - -Fajardo, et al. Standards Track [Page 74] - -RFC 6733 Diameter Base Protocol October 2012 - - - o 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. - - o Server-initiated messages that MUST be received by a specific - Diameter client (e.g., access device), such as the Abort-Session- - Request message, which is used to request that a particular user's - session be terminated. - - Note that an agent can only forward a request to a host described in - the Destination-Host AVP if the host in question is included in its - peer table (see Section 2.6). Otherwise, the request is routed based - on the Destination-Realm only (see Section 6.1.6). - - When a message is received, the message is processed in the following - order: - - o If the message is destined for the local host, the procedures - listed in Section 6.1.4 are followed. - - o If the message is intended for a Diameter peer with whom the local - host is able to directly communicate, the procedures listed in - Section 6.1.5 are followed. This is known as "Request - Forwarding". - - o The procedure listed in Section 6.1.6 is followed, which is known - as "Request Routing". - - o If none of the above are successful, an answer is returned with - the Result-Code set to DIAMETER_UNABLE_TO_DELIVER, with the 'E' - bit set. - - For routing of Diameter messages to work within an administrative - domain, all Diameter nodes within the realm MUST be peers. - - The overview contained in this section (6.1) is intended to provide - general guidelines to Diameter developers. Implementations are free - to use different methods than the ones described here as long as they - conform to the requirements specified in Sections 6.1.1 through - 6.1.9. See Section 7 for more details on error handling. - -6.1.1. Originating a Request - - When creating a request, in addition to any other procedures - described in the application definition for that specific request, - the following procedures MUST be followed: - - - - - -Fajardo, et al. Standards Track [Page 75] - -RFC 6733 Diameter Base Protocol October 2012 - - - o the Command Code is set to the appropriate value; - - o the 'R' bit is set; - - o the End-to-End Identifier is set to a locally unique value; - - o the Origin-Host and Origin-Realm AVPs MUST be set to the - appropriate values, used to identify the source of the message; - and - - o the Destination-Host and Destination-Realm AVPs MUST be set to the - appropriate values, as described in Section 6.1. - -6.1.2. Sending a Request - - When sending a request, originated either locally or as the result of - a forwarding or routing operation, the following procedures SHOULD be - followed: - - o The Hop-by-Hop Identifier SHOULD be set to a locally unique value. - - o The message SHOULD be saved in the list of pending requests. - - Other actions to perform on the message based on the particular role - the agent is playing are described in the following sections. - -6.1.3. Receiving Requests - - A relay or proxy agent MUST check for forwarding loops when receiving - requests. A loop is detected if the server finds its own identity in - a Route-Record AVP. When such an event occurs, the agent MUST answer - with the Result-Code AVP set to DIAMETER_LOOP_DETECTED. - -6.1.4. Processing Local Requests - - A request is known to be for local consumption when one of the - following conditions occurs: - - o The Destination-Host AVP contains the local host's identity; - - o The Destination-Host AVP is not present, the Destination-Realm AVP - contains a realm the server is configured to process locally, and - the Diameter application is locally supported; or - - o Both the Destination-Host and the Destination-Realm are not - present. - - - - - -Fajardo, et al. Standards Track [Page 76] - -RFC 6733 Diameter Base Protocol October 2012 - - - When a request is locally processed, the rules in Section 6.2 should - be used to generate the corresponding answer. - -6.1.5. Request Forwarding - - Request forwarding is done using the Diameter peer table. The - Diameter peer table contains all of the peers with which the local - node is able to directly communicate. - - When a request is received, and the host encoded in the Destination- - Host AVP is one that is present in the peer table, the message SHOULD - be forwarded to the peer. - -6.1.6. Request Routing - - Diameter request message routing is done via realms and Application - Ids. A Diameter message that may be forwarded by Diameter agents - (proxies, redirect agents, or relay agents) MUST include the target - realm in the Destination-Realm AVP. Request routing SHOULD rely on - the Destination-Realm AVP and the Application Id present in the - request message header to aid in the routing decision. The realm MAY - be retrieved from the User-Name AVP, which is in the form of a - Network Access Identifier (NAI). The realm portion of the NAI is - inserted in the Destination-Realm AVP. - - Diameter agents MAY have a list of locally supported realms and - applications, and they MAY have a list of externally supported realms - and applications. When a request is received that includes a realm - and/or application that is not locally supported, the message is - routed to the peer configured in the routing table (see Section 2.7). - - Realm names and Application Ids are the minimum supported routing - criteria, additional information may be needed to support redirect - semantics. - -6.1.7. Predictive Loop Avoidance - - Before forwarding or routing a request, Diameter agents, in addition - to performing the processing described in Section 6.1.3, SHOULD check - for the presence of a candidate route's peer identity in any of the - Route-Record AVPs. In the event of the agent detecting the presence - of a candidate route's peer identity in a Route-Record AVP, the agent - MUST ignore such a route for the Diameter request message and attempt - alternate routes if any exist. In case all the candidate routes are - eliminated by the above criteria, the agent SHOULD return a - DIAMETER_UNABLE_TO_DELIVER message. - - - - - -Fajardo, et al. Standards Track [Page 77] - -RFC 6733 Diameter Base Protocol October 2012 - - -6.1.8. Redirecting Requests - - When a redirect agent receives a request whose routing entry is set - to REDIRECT, it MUST reply with an answer message with the 'E' bit - set, while maintaining the Hop-by-Hop Identifier in the header, and - include the Result-Code AVP to DIAMETER_REDIRECT_INDICATION. Each of - the servers associated with the routing entry are added in a separate - Redirect-Host AVP. - - +------------------+ - | Diameter | - | Redirect Agent | - +------------------+ - ^ | 2. command + 'E' bit - 1. Request | | Result-Code = - [email protected] | | DIAMETER_REDIRECT_INDICATION + - | | Redirect-Host AVP(s) - | v - +-------------+ 3. Request +-------------+ - | example.com |------------->| example.net | - | Relay | | Diameter | - | Agent |<-------------| Server | - +-------------+ 4. Answer +-------------+ - - Figure 5: Diameter Redirect Agent - - The receiver of an answer message with the 'E' bit set and the - Result-Code AVP set to DIAMETER_REDIRECT_INDICATION uses the Hop-by- - Hop Identifier in the Diameter header to identify the request in the - pending message queue (see Section 5.5.4) that is to be redirected. - If no transport connection exists with the new peer, one is created, - and the request is sent directly to it. - - Multiple Redirect-Host AVPs are allowed. The receiver of the answer - message with the 'E' bit set selects exactly one of these hosts as - the destination of the redirected message. - - When the Redirect-Host-Usage AVP included in the answer message has a - non-zero value, a route entry for the redirect indications is created - and cached by the receiver. The redirect usage for such a route - entry is set by the value of Redirect-Host-Usage AVP and the lifetime - of the cached route entry is set by Redirect-Max-Cache-Time AVP - value. - - It is possible that multiple redirect indications can create multiple - cached route entries differing only in their redirect usage and the - peer to forward messages to. As an example, two(2) route entries - that are created by two(2) redirect indications results in two(2) - - - -Fajardo, et al. Standards Track [Page 78] - -RFC 6733 Diameter Base Protocol October 2012 - - - cached routes for the same realm and Application Id. However, one - has a redirect usage of ALL_SESSION, where matching requests will be - forwarded to one peer; the other has a redirect usage of ALL_REALM, - where request are forwarded to another peer. Therefore, an incoming - request that matches the realm and Application Id of both routes will - need additional resolution. In such a case, a routing precedence - rule MUST be used against the redirect usage value to resolve the - contention. The precedence rule can be found in Section 6.13. - -6.1.9. Relaying and Proxying Requests - - A relay or proxy agent MUST append a Route-Record AVP to all requests - forwarded. The AVP contains the identity of the peer from which the - request was received. - - The Hop-by-Hop Identifier in the request is saved and replaced with a - locally unique value. The source of the request is also saved, which - includes the IP address, port, and protocol. - - A relay or proxy agent MAY include the Proxy-Info AVP in requests if - it requires access to any local state information when the - corresponding response is received. The Proxy-Info AVP has security - implications as state information is distributed to other entities. - As such, it is RECOMMENDED that the content of the Proxy-Info AVP be - protected with cryptographic mechanisms, for example, by using a - keyed message digest such as HMAC-SHA1 [RFC2104]. Such a mechanism, - however, requires the management of keys, although only locally at - the Diameter server. Still, a full description of the management of - the keys used to protect the Proxy-Info AVP is beyond the scope of - this document. Below is a list of common recommendations: - - o The keys should be generated securely following the randomness - recommendations in [RFC4086]. - - o The keys and cryptographic protection algorithms should be at - least 128 bits in strength. - - o The keys should not be used for any other purpose than generating - and verifying instances of the Proxy-Info AVP. - - o The keys should be changed regularly. - - o The keys should be changed if the AVP format or cryptographic - protection algorithms change. - - The message is then forwarded to the next hop, as identified in the - routing table. - - - - -Fajardo, et al. Standards Track [Page 79] - -RFC 6733 Diameter Base Protocol October 2012 - - - Figure 6 provides an example of message routing using the procedures - listed in these sections. - - (Origin-Host=nas.example.net) (Origin-Host=nas.example.net) - (Origin-Realm=example.net) (Origin-Realm=example.net) - (Destination-Realm=example.com) (Destination-Realm=example.com) - (Route-Record=nas.example.net) - +------+ ------> +------+ ------> +------+ - | | (Request) | | (Request) | | - | NAS +-------------------+ DRL +-------------------+ HMS | - | | | | | | - +------+ <------ +------+ <------ +------+ - example.net (Answer) example.net (Answer) example.com - (Origin-Host=hms.example.com) (Origin-Host=hms.example.com) - (Origin-Realm=example.com) (Origin-Realm=example.com) - - Figure 6: Routing of Diameter messages - - Relay and proxy agents are not required to perform full inspection of - incoming messages. At a minimum, validation of the message header - and relevant routing AVPs has to be done when relaying messages. - Proxy agents may optionally perform more in-depth message validation - for applications in which it is interested. - -6.2. Diameter Answer Processing - - When a request is locally processed, the following procedures MUST be - applied to create the associated answer, in addition to any - additional procedures that MAY be discussed in the Diameter - application defining the command: - - o The same Hop-by-Hop Identifier in the request is used in the - answer. - - o The local host's identity is encoded in the Origin-Host AVP. - - o The Destination-Host and Destination-Realm AVPs MUST NOT be - present in the answer message. - - o The Result-Code AVP is added with its value indicating success or - failure. - - o If the Session-Id is present in the request, it MUST be included - in the answer. - - o Any Proxy-Info AVPs in the request MUST be added to the answer - message, in the same order they were present in the request. - - - - -Fajardo, et al. Standards Track [Page 80] - -RFC 6733 Diameter Base Protocol October 2012 - - - o The 'P' bit is set to the same value as the one in the request. - - o The same End-to-End identifier in the request is used in the - answer. - - Note that the error messages (see Section 7) are also subjected to - the above processing rules. - -6.2.1. Processing Received Answers - - A Diameter client or proxy MUST match the Hop-by-Hop Identifier in an - answer received against the list of pending requests. The - corresponding message should be removed from the list of pending - requests. It SHOULD ignore answers received that do not match a - known Hop-by-Hop Identifier. - -6.2.2. Relaying and Proxying Answers - - If the answer is for a request that was proxied or relayed, the agent - MUST restore the original value of the Diameter header's Hop-by-Hop - Identifier field. - - If the last Proxy-Info AVP in the message is targeted to the local - Diameter server, the AVP MUST be removed before the answer is - forwarded. - - If a relay or proxy agent receives an answer with a Result-Code AVP - indicating a failure, it MUST NOT modify the contents of the AVP. - Any additional local errors detected SHOULD be logged but not - reflected in the Result-Code AVP. If the agent receives an answer - message with a Result-Code AVP indicating success, and it wishes to - modify the AVP to indicate an error, it MUST modify the Result-Code - AVP to contain the appropriate error in the message destined towards - the access device as well as include the Error-Reporting-Host AVP; it - MUST also issue an STR on behalf of the access device towards the - Diameter server. - - The agent MUST then send the answer to the host that it received the - original request from. - -6.3. Origin-Host AVP - - The Origin-Host AVP (AVP Code 264) is of type DiameterIdentity, and - it MUST be present in all Diameter messages. This AVP identifies the - endpoint that originated the Diameter message. Relay agents MUST NOT - modify this AVP. - - - - - -Fajardo, et al. Standards Track [Page 81] - -RFC 6733 Diameter Base Protocol October 2012 - - - The value of the Origin-Host AVP is guaranteed to be unique within a - single host. - - Note that the Origin-Host AVP may resolve to more than one address as - the Diameter peer may support more than one address. - - This AVP SHOULD be placed as close to the Diameter header as - possible. - -6.4. Origin-Realm AVP - - The Origin-Realm AVP (AVP Code 296) is of type DiameterIdentity. - This AVP contains the Realm of the originator of any Diameter message - and MUST be present in all messages. - - This AVP SHOULD be placed as close to the Diameter header as - possible. - -6.5. Destination-Host AVP - - The Destination-Host AVP (AVP Code 293) is of type DiameterIdentity. - This AVP MUST be present in all unsolicited agent initiated messages, - MAY be present in request messages, and MUST NOT be present in answer - messages. - - The absence of the Destination-Host AVP will cause a message to be - sent to any Diameter server supporting the application within the - realm specified in Destination-Realm AVP. - - This AVP SHOULD be placed as close to the Diameter header as - possible. - -6.6. Destination-Realm AVP - - The Destination-Realm AVP (AVP Code 283) is of type DiameterIdentity - and contains the realm to which the message is to be routed. The - Destination-Realm AVP MUST NOT be present in answer messages. - Diameter clients insert the realm portion of the User-Name AVP. - Diameter servers initiating a request message use the value of the - Origin-Realm AVP from a previous message received from the intended - target host (unless it is known a priori). When present, the - Destination-Realm AVP is used to perform message routing decisions. - - The CCF for a request message that includes the Destination-Realm AVP - SHOULD list the Destination-Realm AVP as a required AVP (an AVP - indicated as {AVP}); otherwise, the message is inherently a non- - routable message. - - - - -Fajardo, et al. Standards Track [Page 82] - -RFC 6733 Diameter Base Protocol October 2012 - - - This AVP SHOULD be placed as close to the Diameter header as - possible. - -6.7. Routing AVPs - - The AVPs defined in this section are Diameter AVPs used for routing - purposes. These AVPs change as Diameter messages are processed by - agents. - -6.7.1. Route-Record AVP - - The Route-Record AVP (AVP Code 282) is of type DiameterIdentity. The - identity added in this AVP MUST be the same as the one received in - the Origin-Host of the Capabilities Exchange message. - -6.7.2. Proxy-Info AVP - - The Proxy-Info AVP (AVP Code 284) is of type Grouped. This AVP - contains the identity and local state information of the Diameter - node that creates and adds it to a message. The Grouped Data field - has the following CCF grammar: - - Proxy-Info ::= < AVP Header: 284 > - { Proxy-Host } - { Proxy-State } - * [ AVP ] - -6.7.3. Proxy-Host AVP - - The Proxy-Host AVP (AVP Code 280) is of type DiameterIdentity. This - AVP contains the identity of the host that added the Proxy-Info AVP. - -6.7.4. Proxy-State AVP - - The Proxy-State AVP (AVP Code 33) is of type OctetString. It - contains state information that would otherwise be stored at the - Diameter entity that created it. As such, this AVP MUST be treated - as opaque data by other Diameter entities. - -6.8. Auth-Application-Id AVP - - The Auth-Application-Id AVP (AVP Code 258) is of type Unsigned32 and - is used in order to advertise support of the Authentication and - Authorization portion of an application (see Section 2.4). If - present in a message other than CER and CEA, the value of the Auth- - Application-Id AVP MUST match the Application Id present in the - Diameter message header. - - - - -Fajardo, et al. Standards Track [Page 83] - -RFC 6733 Diameter Base Protocol October 2012 - - -6.9. Acct-Application-Id AVP - - The Acct-Application-Id AVP (AVP Code 259) is of type Unsigned32 and - is used in order to advertise support of the accounting portion of an - application (see Section 2.4). If present in a message other than - CER and CEA, the value of the Acct-Application-Id AVP MUST match the - Application Id present in the Diameter message header. - -6.10. Inband-Security-Id AVP - - The Inband-Security-Id AVP (AVP Code 299) is of type Unsigned32 and - is used in order to advertise support of the security portion of the - application. The use of this AVP in CER and CEA messages is NOT - RECOMMENDED. Instead, discovery of a Diameter entity's security - capabilities can be done either through static configuration or via - Diameter Peer Discovery as described in Section 5.2. - - The following values are supported: - - - NO_INBAND_SECURITY 0 - - This peer does not support TLS/TCP and DTLS/SCTP. This is the - default value, if the AVP is omitted. - - TLS 1 - - This node supports TLS/TCP [RFC5246] and DTLS/SCTP [RFC6083] - security. - -6.11. Vendor-Specific-Application-Id AVP - - The Vendor-Specific-Application-Id AVP (AVP Code 260) is of type - Grouped and is used to advertise support of a vendor-specific - Diameter application. Exactly one instance of either Auth- - Application-Id or Acct-Application-Id AVP MUST be present. The - Application Id carried by either Auth-Application-Id or Acct- - Application-Id AVP MUST comply with vendor-specific Application Id - assignment described in Section 11.3. It MUST also match the - Application Id present in the Diameter header except when used in a - CER or CEA message. - - The Vendor-Id AVP is an informational AVP pertaining to the vendor - who may have authorship of the vendor-specific Diameter application. - It MUST NOT be used as a means of defining a completely separate - vendor-specific Application Id space. - - - - - -Fajardo, et al. Standards Track [Page 84] - -RFC 6733 Diameter Base Protocol October 2012 - - - The Vendor-Specific-Application-Id AVP SHOULD be placed as close to - the Diameter header as possible. - - AVP Format - - <Vendor-Specific-Application-Id> ::= < AVP Header: 260 > - { Vendor-Id } - [ Auth-Application-Id ] - [ Acct-Application-Id ] - - A Vendor-Specific-Application-Id AVP MUST contain exactly one of - either Auth-Application-Id or Acct-Application-Id. If a Vendor- - Specific-Application-Id is received without one of these two AVPs, - then the recipient SHOULD issue an answer with a Result-Code set to - DIAMETER_MISSING_AVP. The answer SHOULD also include a Failed-AVP, - which MUST contain an example of an Auth-Application-Id AVP and an - Acct-Application-Id AVP. - - If a Vendor-Specific-Application-Id is received that contains both - Auth-Application-Id and Acct-Application-Id, then the recipient MUST - issue an answer with Result-Code set to - DIAMETER_AVP_OCCURS_TOO_MANY_TIMES. The answer MUST also include a - Failed-AVP, which MUST contain the received Auth-Application-Id AVP - and Acct-Application-Id AVP. - -6.12. Redirect-Host AVP - - The Redirect-Host AVP (AVP Code 292) is of type DiameterURI. One or - more instances of this AVP MUST be present if the answer message's - 'E' bit is set and the Result-Code AVP is set to - DIAMETER_REDIRECT_INDICATION. - - Upon receiving the above, the receiving Diameter node SHOULD forward - the request directly to one of the hosts identified in these AVPs. - The server contained in the selected Redirect-Host AVP SHOULD be used - for all messages matching the criteria set by the Redirect-Host-Usage - AVP. - -6.13. Redirect-Host-Usage AVP - - The Redirect-Host-Usage AVP (AVP Code 261) is of type Enumerated. - This AVP MAY be present in answer messages whose 'E' bit is set and - the Result-Code AVP is set to DIAMETER_REDIRECT_INDICATION. - - When present, this AVP provides hints about how the routing entry - resulting from the Redirect-Host is to be used. The following values - are supported: - - - - -Fajardo, et al. Standards Track [Page 85] - -RFC 6733 Diameter Base Protocol October 2012 - - - DONT_CACHE 0 - - The host specified in the Redirect-Host AVP SHOULD NOT be cached. - This is the default value. - - ALL_SESSION 1 - - All messages within the same session, as defined by the same value - of the Session-ID AVP SHOULD be sent to the host specified in the - Redirect-Host AVP. - - ALL_REALM 2 - - All messages destined for the realm requested SHOULD be sent to - the host specified in the Redirect-Host AVP. - - REALM_AND_APPLICATION 3 - - All messages for the application requested to the realm specified - SHOULD be sent to the host specified in the Redirect-Host AVP. - - ALL_APPLICATION 4 - - All messages for the application requested SHOULD be sent to the - host specified in the Redirect-Host AVP. - - ALL_HOST 5 - - All messages that would be sent to the host that generated the - Redirect-Host SHOULD be sent to the host specified in the - Redirect-Host AVP. - - ALL_USER 6 - - All messages for the user requested SHOULD be sent to the host - specified in the Redirect-Host AVP. - - When multiple cached routes are created by redirect indications and - they differ only in redirect usage and peers to forward requests to - (see Section 6.1.8), a precedence rule MUST be applied to the - redirect usage values of the cached routes during normal routing to - resolve contentions that may occur. The precedence rule is the order - that dictate which redirect usage should be considered before any - other as they appear. The order is as follows: - - - - - - - -Fajardo, et al. Standards Track [Page 86] - -RFC 6733 Diameter Base Protocol October 2012 - - - 1. ALL_SESSION - - 2. ALL_USER - - 3. REALM_AND_APPLICATION - - 4. ALL_REALM - - 5. ALL_APPLICATION - - 6. ALL_HOST - -6.14. Redirect-Max-Cache-Time AVP - - The Redirect-Max-Cache-Time AVP (AVP Code 262) is of type Unsigned32. - This AVP MUST be present in answer messages whose 'E' bit is set, - whose Result-Code AVP is set to DIAMETER_REDIRECT_INDICATION, and - whose Redirect-Host-Usage AVP set to a non-zero value. - - This AVP contains the maximum number of seconds the peer and route - table entries, created as a result of the Redirect-Host, SHOULD be - cached. Note that once a host is no longer reachable, any associated - cache, peer, and routing table entries MUST be deleted. - -7. Error Handling - - There are two different types of errors in Diameter; protocol errors - and application errors. A protocol error is one that occurs at the - base protocol level and MAY require per-hop attention (e.g., a - message routing error). Application errors, on the other hand, - generally occur due to a problem with a function specified in a - Diameter application (e.g., user authentication, missing AVP). - - Result-Code AVP values that are used to report protocol errors MUST - only be present in answer messages whose 'E' bit is set. When a - request message is received that causes a protocol error, an answer - message is returned with the 'E' bit set, and the Result-Code AVP is - set to the appropriate protocol error value. As the answer is sent - back towards the originator of the request, each proxy or relay agent - MAY take action on the message. - - - - - - - - - - - -Fajardo, et al. Standards Track [Page 87] - -RFC 6733 Diameter Base Protocol October 2012 - - - 1. Request +---------+ Link Broken - +-------------------------->|Diameter |----///----+ - | +---------------------| | v - +------+--+ | 2. answer + 'E' set | Relay 2 | +--------+ - |Diameter |<-+ (Unable to Forward) +---------+ |Diameter| - | | | Home | - | Relay 1 |--+ +---------+ | Server | - +---------+ | 3. Request |Diameter | +--------+ - +-------------------->| | ^ - | Relay 3 |-----------+ - +---------+ - - Figure 7: Example of Protocol Error Causing Answer Message - - Figure 7 provides an example of a message forwarded upstream by a - Diameter relay. When the message is received by Relay 2, and it - detects that it cannot forward the request to the home server, an - answer message is returned with the 'E' bit set and the Result-Code - AVP set to DIAMETER_UNABLE_TO_DELIVER. Given that this error falls - within the protocol error category, Relay 1 would take special - action, and given the error, attempt to route the message through its - alternate Relay 3. - - +---------+ 1. Request +---------+ 2. Request +---------+ - | Access |------------>|Diameter |------------>|Diameter | - | | | | | Home | - | Device |<------------| Relay |<------------| Server | - +---------+ 4. Answer +---------+ 3. Answer +---------+ - (Missing AVP) (Missing AVP) - - Figure 8: Example of Application Error Answer Message - - Figure 8 provides an example of a Diameter message that caused an - application error. When application errors occur, the Diameter - entity reporting the error clears the 'R' bit in the Command Flags - and adds the Result-Code AVP with the proper value. Application - errors do not require any proxy or relay agent involvement; - therefore, the message would be forwarded back to the originator of - the request. - - In the case where the answer message itself contains errors, any - related session SHOULD be terminated by sending an STR or ASR - message. The Termination-Cause AVP in the STR MAY be filled with the - appropriate value to indicate the cause of the error. An application - MAY also send an application-specific request instead of an STR or - ASR message to signal the error in the case where no state is - maintained or to allow for some form of error recovery with the - corresponding Diameter entity. - - - -Fajardo, et al. Standards Track [Page 88] - -RFC 6733 Diameter Base Protocol October 2012 - - - There are certain Result-Code AVP application errors that require - additional AVPs to be present in the answer. In these cases, the - Diameter node that sets the Result-Code AVP to indicate the error - MUST add the AVPs. Examples are as follows: - - o A request with an unrecognized AVP is received with the 'M' bit - (Mandatory bit) set causes an answer to be sent with the Result- - Code AVP set to DIAMETER_AVP_UNSUPPORTED and the Failed-AVP AVP - containing the offending AVP. - - o A request with an AVP that is received with an unrecognized value - causes an answer to be returned with the Result-Code AVP set to - DIAMETER_INVALID_AVP_VALUE, with the Failed-AVP AVP containing the - AVP causing the error. - - o A received command that is missing AVPs that are defined as - required in the commands CCF; examples are AVPs indicated as - {AVP}. The receiver issues an answer with the Result-Code set to - DIAMETER_MISSING_AVP and creates an AVP with the AVP Code and - other fields set as expected in the missing AVP. The created AVP - is then added to the Failed-AVP AVP. - - The Result-Code AVP describes the error that the Diameter node - encountered in its processing. In case there are multiple errors, - the Diameter node MUST report only the first error it encountered - (detected possibly in some implementation-dependent order). The - specific errors that can be described by this AVP are described in - the following section. - -7.1. Result-Code AVP - - The Result-Code AVP (AVP Code 268) is of type Unsigned32 and - indicates whether a particular request was completed successfully or - an error occurred. All Diameter answer messages in IETF-defined - Diameter application specifications MUST include one Result-Code AVP. - A non-successful Result-Code AVP (one containing a non-2xxx value - other than DIAMETER_REDIRECT_INDICATION) MUST include the Error- - Reporting-Host AVP if the host setting the Result-Code AVP is - different from the identity encoded in the Origin-Host AVP. - - The Result-Code data field contains an IANA-managed 32-bit address - space representing errors (see Section 11.3.2). Diameter provides - the following classes of errors, all identified by the thousands - digit in the decimal notation: - - - - - - - -Fajardo, et al. Standards Track [Page 89] - -RFC 6733 Diameter Base Protocol October 2012 - - - o 1xxx (Informational) - - o 2xxx (Success) - - o 3xxx (Protocol Errors) - - o 4xxx (Transient Failures) - - o 5xxx (Permanent Failure) - - An unrecognized class (one whose first digit is not defined in this - section) MUST be handled as a permanent failure. - -7.1.1. Informational - - Errors that fall within this category are used to inform the - requester that a request could not be satisfied, and additional - action is required on its part before access is granted. - - DIAMETER_MULTI_ROUND_AUTH 1001 - - This informational error is returned by a Diameter server to - inform the access device that the authentication mechanism being - used requires multiple round trips, and a subsequent request needs - to be issued in order for access to be granted. - -7.1.2. Success - - Errors that fall within the Success category are used to inform a - peer that a request has been successfully completed. - - DIAMETER_SUCCESS 2001 - - The request was successfully completed. - - DIAMETER_LIMITED_SUCCESS 2002 - - When returned, the request was successfully completed, but - additional processing is required by the application in order to - provide service to the user. - -7.1.3. Protocol Errors - - Errors that fall within the Protocol Error category SHOULD be treated - on a per-hop basis, and Diameter proxies MAY attempt to correct the - error, if it is possible. Note that these errors MUST only be used - in answer messages whose 'E' bit is set. - - - - -Fajardo, et al. Standards Track [Page 90] - -RFC 6733 Diameter Base Protocol October 2012 - - - DIAMETER_COMMAND_UNSUPPORTED 3001 - - This error code is used when a Diameter entity receives a message - with a Command Code that it does not support. - - DIAMETER_UNABLE_TO_DELIVER 3002 - - This error is given when Diameter cannot deliver the message to - the destination, either because no host within the realm - supporting the required application was available to process the - request or because the Destination-Host AVP was given without the - associated Destination-Realm AVP. - - DIAMETER_REALM_NOT_SERVED 3003 - - The intended realm of the request is not recognized. - - DIAMETER_TOO_BUSY 3004 - - When returned, a Diameter node SHOULD attempt to send the message - to an alternate peer. This error MUST only be used when a - specific server is requested, and it cannot provide the requested - service. - - DIAMETER_LOOP_DETECTED 3005 - - An agent detected a loop while trying to get the message to the - intended recipient. The message MAY be sent to an alternate peer, - if one is available, but the peer reporting the error has - identified a configuration problem. - - DIAMETER_REDIRECT_INDICATION 3006 - - A redirect agent has determined that the request could not be - satisfied locally, and the initiator of the request SHOULD direct - the request directly to the server, whose contact information has - been added to the response. When set, the Redirect-Host AVP MUST - be present. - - DIAMETER_APPLICATION_UNSUPPORTED 3007 - - A request was sent for an application that is not supported. - - DIAMETER_INVALID_HDR_BITS 3008 - - A request was received whose bits in the Diameter header were set - either to an invalid combination or to a value that is - inconsistent with the Command Code's definition. - - - -Fajardo, et al. Standards Track [Page 91] - -RFC 6733 Diameter Base Protocol October 2012 - - - DIAMETER_INVALID_AVP_BITS 3009 - - A request was received that included an AVP whose flag bits are - set to an unrecognized value or that is inconsistent with the - AVP's definition. - - DIAMETER_UNKNOWN_PEER 3010 - - A CER was received from an unknown peer. - -7.1.4. Transient Failures - - Errors that fall within the transient failures category are used to - inform a peer that the request could not be satisfied at the time it - was received but MAY be able to satisfy the request in the future. - Note that these errors MUST be used in answer messages whose 'E' bit - is not set. - - DIAMETER_AUTHENTICATION_REJECTED 4001 - - The authentication process for the user failed, most likely due to - an invalid password used by the user. Further attempts MUST only - be tried after prompting the user for a new password. - - DIAMETER_OUT_OF_SPACE 4002 - - A Diameter node received the accounting request but was unable to - commit it to stable storage due to a temporary lack of space. - - ELECTION_LOST 4003 - - The peer has determined that it has lost the election process and - has therefore disconnected the transport connection. - -7.1.5. Permanent Failures - - Errors that fall within the permanent failures category are used to - inform the peer that the request failed and should not be attempted - again. Note that these errors SHOULD be used in answer messages - whose 'E' bit is not set. In error conditions where it is not - possible or efficient to compose application-specific answer grammar, - answer messages with the 'E' bit set and which comply to the grammar - described in Section 7.2 MAY also be used for permanent errors. - - - - - - - - -Fajardo, et al. Standards Track [Page 92] - -RFC 6733 Diameter Base Protocol October 2012 - - - DIAMETER_AVP_UNSUPPORTED 5001 - - The peer received a message that contained an AVP that is not - recognized or supported and was marked with the 'M' (Mandatory) - bit. A Diameter message with this error MUST contain one or more - Failed-AVP AVPs containing the AVPs that caused the failure. - - DIAMETER_UNKNOWN_SESSION_ID 5002 - - The request contained an unknown Session-Id. - - 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 when 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 it is not willing to provide service - to the user. The Failed-AVP AVP MUST be present, which contain - the AVPs that contradicted each other. - - - - - - -Fajardo, et al. Standards Track [Page 93] - -RFC 6733 Diameter Base Protocol October 2012 - - - DIAMETER_AVP_NOT_ALLOWED 5008 - - A message was received with an AVP that MUST NOT be present. The - Failed-AVP AVP MUST be included and contain a copy of the - offending AVP. - - DIAMETER_AVP_OCCURS_TOO_MANY_TIMES 5009 - - A message was received that included an AVP that appeared more - often than permitted in the message definition. The Failed-AVP - AVP MUST be included and contain a copy of the first instance of - the offending AVP that exceeded the maximum number of occurrences. - - DIAMETER_NO_COMMON_APPLICATION 5010 - - This error is returned by a Diameter node that receives a CER - whereby no applications are common between the CER sending peer - and the CER receiving peer. - - DIAMETER_UNSUPPORTED_VERSION 5011 - - This error is returned when a request was received, whose version - number is unsupported. - - 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 a reserved bit in the Diameter header - is set to one (1) or the bits in the Diameter header are set - incorrectly. - - 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. In cases where the erroneous AVP length - value exceeds the message length or is less than the minimum AVP - header length, it is sufficient to include the offending AVP - header and a zero filled payload of the minimum required length - for the payloads data type. If the AVP is a Grouped AVP, the - Grouped AVP header with an empty payload would be sufficient to - indicate the offending AVP. In the case where the offending AVP - header cannot be fully decoded when the AVP length is less than - - - - -Fajardo, et al. Standards Track [Page 94] - -RFC 6733 Diameter Base Protocol October 2012 - - - the minimum AVP header length, it is sufficient to include an - offending AVP header that is formulated by padding the incomplete - AVP header with zero up to the minimum AVP header length. - - 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) message 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 CCF specification for the command; - instead, it and will conform to the following CCF: - - Message Format - - <answer-message> ::= < Diameter Header: code, ERR [, PXY] > - 0*1< Session-Id > - { Origin-Host } - { Origin-Realm } - { Result-Code } - [ Origin-State-Id ] - [ Error-Message ] - [ Error-Reporting-Host ] - [ Failed-AVP ] - [ Experimental-Result ] - * [ Proxy-Info ] - * [ AVP ] - - - - -Fajardo, et al. Standards Track [Page 95] - -RFC 6733 Diameter Base Protocol October 2012 - - - 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 an environment - where error messages are processed automatically. It SHOULD NOT be - expected that the content of this AVP 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 it MUST be set when the - Result-Code AVP indicates a failure. - -7.5. Failed-AVP AVP - - The Failed-AVP AVP (AVP Code 279) is of type Grouped and provides - debugging information in cases where a request is rejected or not - fully processed due to erroneous information in a specific AVP. The - value of the Result-Code AVP will provide information on the reason - for the Failed-AVP AVP. A Diameter answer message SHOULD contain an - instance of the Failed-AVP AVP that corresponds to the error - indicated by the Result-Code AVP. For practical purposes, this - Failed-AVP would typically refer to the first AVP processing error - that a Diameter node encounters. - - 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 that is restricted to 0, 1, or 0-1 - occurrences. - - A Diameter message SHOULD contain one Failed-AVP AVP, containing the - entire AVP that could not be processed successfully. If the failure - reason is omission of a required AVP, an AVP with the missing AVP - code, the missing Vendor-Id, and a zero-filled payload of the minimum - required length for the omitted AVP will be added. If the failure - reason is an invalid AVP length where the reported length is less - - - -Fajardo, et al. Standards Track [Page 96] - -RFC 6733 Diameter Base Protocol October 2012 - - - than the minimum AVP header length or greater than the reported - message length, a copy of the offending AVP header and a zero-filled - payload of the minimum required length SHOULD be added. - - In the case where the offending AVP is embedded within a Grouped AVP, - the Failed-AVP MAY contain the grouped AVP, which in turn contains - the single offending AVP. The same method MAY be employed if the - grouped AVP itself is embedded in yet another grouped AVP and so on. - In this case, the Failed-AVP MAY contain the grouped AVP hierarchy up - to the single offending AVP. This enables the recipient to detect - the location of the offending AVP when embedded in a group. - - AVP Format - - <Failed-AVP> ::= < AVP Header: 279 > - 1* {AVP} - -7.6. Experimental-Result AVP - - The Experimental-Result AVP (AVP Code 297) is of type Grouped, and - indicates whether a particular vendor-specific request was completed - successfully or whether an error occurred. This AVP has the - following structure: - - AVP Format - - Experimental-Result ::= < AVP Header: 297 > - { Vendor-Id } - { Experimental-Result-Code } - - The Vendor-Id AVP (see Section 5.3.3) in this grouped AVP identifies - the vendor responsible for the assignment of the result code that - follows. All Diameter answer messages defined in vendor-specific - applications MUST include either one Result-Code AVP or one - Experimental-Result AVP. - -7.7. Experimental-Result-Code AVP - - The Experimental-Result-Code AVP (AVP Code 298) is of type Unsigned32 - and contains a vendor-assigned value representing the result of - processing the request. - - It is recommended that vendor-specific result codes follow the same - conventions given for the Result-Code AVP regarding the different - types of result codes and the handling of errors (for non-2xxx - values). - - - - - -Fajardo, et al. Standards Track [Page 97] - -RFC 6733 Diameter Base Protocol October 2012 - - -8. Diameter User Sessions - - In general, Diameter can provide two different types of services to - applications. The first involves authentication and authorization, - and it can optionally make use of accounting. The second only makes - use of accounting. - - When a service makes use of the authentication and/or authorization - portion of an application, and a user requests access to the network, - the Diameter client issues an auth request to its local server. The - auth request is defined in a service-specific Diameter application - (e.g., NASREQ). The request contains a Session-Id AVP, which is used - in subsequent messages (e.g., subsequent authorization, accounting, - etc.) relating to the user's session. The Session-Id AVP is a means - for the client and servers to correlate a Diameter message with a - user session. - - When a Diameter server authorizes a user to implement network - resources for a finite amount of time, and it is willing to extend - the authorization via a future request, it MUST add the - Authorization- Lifetime AVP to the answer message. The - Authorization-Lifetime AVP defines the maximum number of seconds a - user MAY make use of the resources before another authorization - request is expected by the server. The Auth-Grace-Period AVP - contains the number of seconds following the expiration of the - Authorization-Lifetime, after which the server will release all state - information related to the user's session. Note that if payment for - services is expected by the serving realm from the user's home realm, - the Authorization-Lifetime AVP, combined with the Auth-Grace-Period - AVP, implies the maximum length of the session for which the home - realm is willing to be fiscally responsible. Services provided past - the expiration of the Authorization-Lifetime and Auth-Grace-Period - AVPs are the responsibility of the access device. Of course, the - actual cost of services rendered is clearly outside the scope of the - protocol. - - An access device that does not expect to send a re-authorization or a - session termination request to the server MAY include the Auth- - Session-State AVP with the value set to NO_STATE_MAINTAINED as a hint - to the server. If the server accepts the hint, it agrees that since - no session termination message will be received once service to the - user is terminated, it cannot maintain state for the session. If the - answer message from the server contains a different value in the - Auth-Session-State AVP (or the default value if the AVP is absent), - the access device MUST follow the server's directives. Note that the - value NO_STATE_MAINTAINED MUST NOT be set in subsequent re- - authorization requests and answers. - - - - -Fajardo, et al. Standards Track [Page 98] - -RFC 6733 Diameter Base Protocol October 2012 - - - The base protocol does not include any authorization request - messages, since these are largely application-specific and are - defined in a Diameter application document. However, the base - protocol does define a set of messages that are used to terminate - user sessions. These are used to allow servers that maintain state - information to free resources. - - When a service only makes use of the accounting portion of the - Diameter protocol, even in combination with an application, the - Session-Id is still used to identify user sessions. However, the - session termination messages are not used, since a session is - signaled as being terminated by issuing an accounting stop message. - - Diameter may also be used for services that cannot be easily - categorized as authentication, authorization, or accounting (e.g., - certain Third Generation Partnership Project Internet Multimedia - System (3GPP IMS) interfaces). In such cases, the finite state - machine defined in subsequent sections may not be applicable. - Therefore, the application itself MAY need to define its own finite - state machine. However, such application-specific state machines - SHOULD follow the general state machine framework outlined in this - document such as the use of Session-Id AVPs and the use of STR/STA, - ASR/ASA messages for stateful sessions. - -8.1. Authorization Session State Machine - - This section contains a set of finite state machines, which represent - the life cycle of Diameter sessions and which MUST be observed by all - Diameter implementations that make use of the authentication and/or - authorization portion of a Diameter application. The term "Service- - Specific" below refers to a message defined in a Diameter application - (e.g., Mobile IPv4, NASREQ). - - There are four different authorization session state machines - supported in the Diameter base protocol. The first two describe a - session in which the server is maintaining session state, indicated - by the value of the Auth-Session-State AVP (or its absence). One - describes the session from a client perspective, the other from a - server perspective. The second two state machines are used when the - server does not maintain session state. Here again, one describes - the session from a client perspective, the other from a server - perspective. - - When a session is moved to the Idle state, any resources that were - allocated for the particular session must be released. Any event not - listed in the state machines MUST be considered an error condition, - and an answer, if applicable, MUST be returned to the originator of - the message. - - - -Fajardo, et al. Standards Track [Page 99] - -RFC 6733 Diameter Base Protocol October 2012 - - - In the case that an application does not support re-auth, the state - transitions related to server-initiated re-auth, when both client and - server sessions maintain state (e.g., Send RAR, Pending, Receive - RAA), MAY be ignored. - - In the state table, the event "Failure to send X" means that the - Diameter agent is unable to send command X to the desired - destination. This could be due to the peer being down or due to the - peer sending back a transient failure or temporary protocol error - notification DIAMETER_TOO_BUSY or DIAMETER_LOOP_DETECTED in the - Result-Code AVP of the corresponding Answer command. The event 'X - successfully sent' is the complement of 'Failure to send X'. - - The following state machine is observed by a client when state is - maintained on the server: - - CLIENT, STATEFUL - State Event Action New State - --------------------------------------------------------------- - Idle Client or device requests Send Pending - access service- - specific - auth req - - Idle ASR Received Send ASA Idle - for unknown session with - Result-Code = - UNKNOWN_ - SESSION_ID - - Idle RAR Received Send RAA Idle - for unknown session with - Result-Code = - UNKNOWN_ - SESSION_ID - - Pending Successful service-specific Grant Open - authorization answer Access - received with default - Auth-Session-State value - - Pending Successful service-specific Sent STR Discon - authorization answer received, - but service not provided - - Pending Error processing successful Sent STR Discon - service-specific authorization - answer - - - -Fajardo, et al. Standards Track [Page 100] - -RFC 6733 Diameter Base Protocol October 2012 - - - Pending Failed service-specific Clean up Idle - authorization answer received - - Open User or client device Send Open - requests access to service service- - specific - auth req - - Open Successful service-specific Provide Open - authorization answer received service - - Open Failed service-specific Discon. Idle - authorization answer user/device - received. - - Open RAR received and client will Send RAA Open - perform subsequent re-auth with - Result-Code = - SUCCESS - - Open RAR received and client will Send RAA Idle - not perform subsequent with - re-auth Result-Code != - SUCCESS, - Discon. - user/device - - Open Session-Timeout expires on Send STR Discon - access device - - Open ASR received, Send ASA Discon - client will comply with - with request to end the Result-Code = - session = SUCCESS, - Send STR. - - Open ASR Received, Send ASA Open - client will not comply with - with request to end the Result-Code != - session != SUCCESS - - Open Authorization-Lifetime + Send STR Discon - Auth-Grace-Period expires on - access device - - Discon ASR received Send ASA Discon - - - - - -Fajardo, et al. Standards Track [Page 101] - -RFC 6733 Diameter Base Protocol October 2012 - - - Discon STA received Discon. Idle - user/device - - The following state machine is observed by a server when it is - maintaining state for the session: - - SERVER, STATEFUL - State Event Action New State - --------------------------------------------------------------- - Idle Service-specific authorization Send Open - request received, and successful - user is authorized service- - specific - answer - - Idle Service-specific authorization Send Idle - request received, and failed - user is not authorized service- - specific - answer - - Open Service-specific authorization Send Open - request received, and user successful - is authorized service- - specific - answer - - Open Service-specific authorization Send Idle - request received, and user failed - is not authorized service- - specific - answer, - Clean up - - Open Home server wants to confirm Send RAR Pending - authentication and/or - authorization of the user - - Pending Received RAA with a failed Clean up Idle - Result-Code - - Pending Received RAA with Result-Code Update Open - = SUCCESS session - - Open Home server wants to Send ASR Discon - terminate the service - - - - - -Fajardo, et al. Standards Track [Page 102] - -RFC 6733 Diameter Base Protocol October 2012 - - - Open Authorization-Lifetime (and Clean up Idle - Auth-Grace-Period) expires - on home server - - Open Session-Timeout expires on Clean up Idle - home server - - Discon Failure to send ASR Wait, Discon - resend ASR - - Discon ASR successfully sent and Clean up Idle - ASA Received with Result-Code - - Not ASA Received None No Change - Discon - - Any STR Received Send STA, Idle - Clean up - - The following state machine is observed by a client when state is not - maintained on the server: - - CLIENT, STATELESS - State Event Action New State - --------------------------------------------------------------- - Idle Client or device requests Send Pending - access service- - specific - auth req - - Pending Successful service-specific Grant Open - authorization answer access - received with Auth-Session- - State set to - NO_STATE_MAINTAINED - - Pending Failed service-specific Clean up Idle - authorization answer - received - - Open Session-Timeout expires on Discon. Idle - access device user/device - - Open Service to user is terminated Discon. Idle - user/device - - - - - - -Fajardo, et al. Standards Track [Page 103] - -RFC 6733 Diameter Base Protocol October 2012 - - - The following state machine is observed by a server when it is not - maintaining state for the session: - - SERVER, STATELESS - State Event Action New State - --------------------------------------------------------------- - Idle Service-specific authorization Send Idle - request received, and service- - successfully processed specific - answer - -8.2. Accounting Session State Machine - - The following state machines MUST be supported for applications that - have an accounting portion or that require only accounting services. - The first state machine is to be observed by clients. - - See Section 9.7 for Accounting Command Codes and Section 9.8 for - Accounting AVPs. - - The server side in the accounting state machine depends in some cases - on the particular application. The Diameter base protocol defines a - default state machine that MUST be followed by all applications that - have not specified other state machines. This is the second state - machine in this section described below. - - The default server side state machine requires the reception of - accounting records in any order and at any time, and it does not - place any standards requirement on the processing of these records. - Implementations of Diameter may perform checking, ordering, - correlation, fraud detection, and other tasks based on these records. - AVPs may need to be inspected as a part of these tasks. The tasks - can happen either immediately after record reception or in a post- - processing phase. However, as these tasks are typically application - or even policy dependent, they are not standardized by the Diameter - specifications. Applications MAY define requirements on when to - accept accounting records based on the used value of Accounting- - Realtime-Required AVP, credit-limit checks, and so on. - - However, the Diameter base protocol defines one optional server side - state machine that MAY be followed by applications that require - keeping track of the session state at the accounting server. Note - that such tracking is incompatible with the ability to sustain long - duration connectivity problems. Therefore, the use of this state - machine is recommended only in applications where the value of the - Accounting-Realtime-Required AVP is DELIVER_AND_GRANT; hence, - accounting connectivity problems are required to cause the serviced - user to be disconnected. Otherwise, records produced by the client - - - -Fajardo, et al. Standards Track [Page 104] - -RFC 6733 Diameter Base Protocol October 2012 - - - may be lost by the server, which no longer accepts them after the - connectivity is re-established. This state machine is the third - state machine in this section. The state machine is supervised by a - supervision session timer Ts, whose value should be reasonably higher - than the Acct_Interim_Interval value. Ts MAY be set to two times the - value of the Acct_Interim_Interval so as to avoid the accounting - session in the Diameter server to change to Idle state in case of - short transient network failure. - - Any event not listed in the state machines MUST be considered as an - error condition, and a corresponding answer, if applicable, MUST be - returned to the originator of the message. - - In the state table, the event "Failure to send" means that the - Diameter client is unable to communicate with the desired - destination. This could be due to the peer being down, or due to the - peer sending back a transient failure or temporary protocol error - notification DIAMETER_OUT_OF_SPACE, DIAMETER_TOO_BUSY, or - DIAMETER_LOOP_DETECTED in the Result-Code AVP of the Accounting - Answer command. - - The event "Failed answer" means that the Diameter client received a - non-transient failure notification in the Accounting Answer command. - - Note that the action "Disconnect user/dev" MUST also have an effect - on the authorization session state table, e.g., cause the STR message - to be sent, if the given application has both authentication/ - authorization and accounting portions. - - The states PendingS, PendingI, PendingL, PendingE, and PendingB stand - for pending states to wait for an answer to an accounting request - related to a Start, Interim, Stop, Event, or buffered record, - respectively. - - CLIENT, ACCOUNTING - State Event Action New State - --------------------------------------------------------------- - Idle Client or device requests Send PendingS - access accounting - start req. - - Idle Client or device requests Send PendingE - a one-time service accounting - event req - - Idle Records in storage Send PendingB - record - - - - -Fajardo, et al. Standards Track [Page 105] - -RFC 6733 Diameter Base Protocol October 2012 - - - PendingS Successful accounting Open - start answer received - - PendingS Failure to send and buffer Store Open - space available and real time Start - not equal to DELIVER_AND_GRANT Record - - PendingS Failure to send and no buffer Open - space available and real time - equal to GRANT_AND_LOSE - - PendingS Failure to send and no Disconnect Idle - buffer space available and user/dev - real time not equal to - GRANT_AND_LOSE - - PendingS Failed accounting start answer Open - received and real time equal - to GRANT_AND_LOSE - - PendingS Failed accounting start answer Disconnect Idle - received and real time not user/dev - equal to GRANT_AND_LOSE - - PendingS User service terminated Store PendingS - stop - record - - Open Interim interval elapses Send PendingI - accounting - interim - record - - Open User service terminated Send PendingL - accounting - stop req. - - PendingI Successful accounting interim Open - answer received - - PendingI Failure to send and (buffer Store Open - space available or old interim - record can be overwritten) record - and real time not equal to - DELIVER_AND_GRANT - - - - - - -Fajardo, et al. Standards Track [Page 106] - -RFC 6733 Diameter Base Protocol October 2012 - - - PendingI Failure to send and no buffer Open - space available and real time - equal to GRANT_AND_LOSE - - PendingI Failure to send and no Disconnect Idle - buffer space available and user/dev - real time not equal to - GRANT_AND_LOSE - - PendingI Failed accounting interim Open - answer received and real time - equal to GRANT_AND_LOSE - - PendingI Failed accounting interim Disconnect Idle - answer received and user/dev - real time not equal to - GRANT_AND_LOSE - - PendingI User service terminated Store PendingI - stop - record - PendingE Successful accounting Idle - event answer received - - PendingE Failure to send and buffer Store Idle - space available event - record - - PendingE Failure to send and no buffer Idle - space available - - PendingE Failed accounting event answer Idle - received - - PendingB Successful accounting answer Delete Idle - received record - - PendingB Failure to send Idle - - PendingB Failed accounting answer Delete Idle - received record - - PendingL Successful accounting Idle - stop answer received - - PendingL Failure to send and buffer Store Idle - space available stop - record - - - -Fajardo, et al. Standards Track [Page 107] - -RFC 6733 Diameter Base Protocol October 2012 - - - PendingL Failure to send and no buffer Idle - space available - - PendingL Failed accounting stop answer Idle - received - - - SERVER, STATELESS ACCOUNTING - State Event Action New State - --------------------------------------------------------------- - - Idle Accounting start request Send Idle - received and successfully accounting - processed. start - answer - - Idle Accounting event request Send Idle - received and successfully accounting - processed. event - answer - - Idle Interim record received Send Idle - and successfully processed. accounting - interim - answer - - Idle Accounting stop request Send Idle - received and successfully accounting - processed stop answer - - Idle Accounting request received; Send Idle - no space left to store accounting - records answer; - Result-Code = - OUT_OF_ - SPACE - - - - - - - - - - - - - - - -Fajardo, et al. Standards Track [Page 108] - -RFC 6733 Diameter Base Protocol October 2012 - - - SERVER, STATEFUL ACCOUNTING - State Event Action New State - --------------------------------------------------------------- - - Idle Accounting start request Send Open - received and successfully accounting - processed. start - answer; - Start Ts - - Idle Accounting event request Send Idle - received and successfully accounting - processed. event - answer - Idle Accounting request received; Send Idle - no space left to store accounting - records answer; - Result-Code = - OUT_OF_ - SPACE - - Open Interim record received Send Open - and successfully processed. accounting - interim - answer; - Restart Ts - - Open Accounting stop request Send Idle - received and successfully accounting - processed stop answer; - Stop Ts - - Open Accounting request received; Send Idle - no space left to store accounting - records answer; - Result-Code = - OUT_OF_ - SPACE; - Stop Ts - - Open Session supervision timer Ts Stop Ts Idle - expired - - - - - - - - - -Fajardo, et al. Standards Track [Page 109] - -RFC 6733 Diameter Base Protocol October 2012 - - -8.3. Server-Initiated Re-Auth - - A Diameter server may initiate a re-authentication and/or re- - authorization service for a particular session by issuing a Re-Auth- - Request (RAR). - - For example, for prepaid services, the Diameter server that - originally authorized a session may need some confirmation that the - user is still using the services. - - An access device that receives an RAR message with the Session-Id - equal to a currently active session MUST initiate a re-auth towards - the user, if the service supports this particular feature. Each - Diameter application MUST state whether server-initiated re-auth is - supported, since some applications do not allow access devices to - prompt the user for re-auth. - -8.3.1. Re-Auth-Request - - The Re-Auth-Request (RAR), indicated by the Command Code set to 258 - and the message flags' 'R' bit set, may be sent by any server to the - access device that is providing session service, to request that the - user be re-authenticated and/or re-authorized. - - - Message Format - - <RAR> ::= < Diameter Header: 258, REQ, PXY > - < Session-Id > - { Origin-Host } - { Origin-Realm } - { Destination-Realm } - { Destination-Host } - { Auth-Application-Id } - { Re-Auth-Request-Type } - [ User-Name ] - [ Origin-State-Id ] - * [ Proxy-Info ] - * [ Route-Record ] - * [ AVP ] - -8.3.2. Re-Auth-Answer - - The Re-Auth-Answer (RAA), indicated by the Command Code set to 258 - and the message flags' 'R' bit clear, is sent in response to the RAR. - The Result-Code AVP MUST be present, and it indicates the disposition - of the request. - - - - -Fajardo, et al. Standards Track [Page 110] - -RFC 6733 Diameter Base Protocol October 2012 - - - A successful RAA message MUST be followed by an application-specific - authentication and/or authorization message. - - Message Format - - <RAA> ::= < Diameter Header: 258, PXY > - < Session-Id > - { Result-Code } - { Origin-Host } - { Origin-Realm } - [ User-Name ] - [ Origin-State-Id ] - [ Error-Message ] - [ Error-Reporting-Host ] - [ Failed-AVP ] - * [ Redirect-Host ] - [ Redirect-Host-Usage ] - [ Redirect-Max-Cache-Time ] - * [ Proxy-Info ] - * [ AVP ] - -8.4. Session Termination - - It is necessary for a Diameter server that authorized a session, for - which it is maintaining state, to be notified when that session is no - longer active, both for tracking purposes as well as to allow - stateful agents to release any resources that they may have provided - for the user's session. For sessions whose state is not being - maintained, this section is not used. - - When a user session that required Diameter authorization terminates, - the access device that provided the service MUST issue a Session- - Termination-Request (STR) message to the Diameter server that - authorized the service, to notify it that the session is no longer - active. An STR MUST be issued when a user session terminates for any - reason, including user logoff, expiration of Session-Timeout, - administrative action, termination upon receipt of an Abort-Session- - Request (see below), orderly shutdown of the access device, etc. - - The access device also MUST issue an STR for a session that was - authorized but never actually started. This could occur, for - example, due to a sudden resource shortage in the access device, or - because the access device is unwilling to provide the type of service - requested in the authorization, or because the access device does not - support a mandatory AVP returned in the authorization, etc. - - It is also possible that a session that was authorized is never - actually started due to action of a proxy. For example, a proxy may - - - -Fajardo, et al. Standards Track [Page 111] - -RFC 6733 Diameter Base Protocol October 2012 - - - modify an authorization answer, converting the result from success to - failure, prior to forwarding the message to the access device. If - the answer did not contain an Auth-Session-State AVP with the value - NO_STATE_MAINTAINED, a proxy that causes an authorized session not to - be started MUST issue an STR to the Diameter server that authorized - the session, since the access device has no way of knowing that the - session had been authorized. - - A Diameter server that receives an STR message MUST clean up - resources (e.g., session state) associated with the Session-Id - specified in the STR and return a Session-Termination-Answer. - - A Diameter server also MUST clean up resources when the Session- - Timeout expires, or when the Authorization-Lifetime and the Auth- - Grace-Period AVPs expire without receipt of a re-authorization - request, regardless of whether an STR for that session is received. - The access device is not expected to provide service beyond the - expiration of these timers; thus, expiration of either of these - timers implies that the access device may have unexpectedly shut - down. - -8.4.1. Session-Termination-Request - - The Session-Termination-Request (STR), indicated by the Command Code - set to 275 and the Command Flags' 'R' bit set, is sent by a Diameter - client or by a Diameter proxy to inform the Diameter server that an - authenticated and/or authorized session is being terminated. - - Message Format - - <STR> ::= < Diameter Header: 275, REQ, PXY > - < Session-Id > - { Origin-Host } - { Origin-Realm } - { Destination-Realm } - { Auth-Application-Id } - { Termination-Cause } - [ User-Name ] - [ Destination-Host ] - * [ Class ] - [ Origin-State-Id ] - * [ Proxy-Info ] - * [ Route-Record ] - * [ AVP ] - - - - - - - -Fajardo, et al. Standards Track [Page 112] - -RFC 6733 Diameter Base Protocol October 2012 - - -8.4.2. Session-Termination-Answer - - The Session-Termination-Answer (STA), indicated by the Command Code - set to 275 and the message flags' 'R' bit clear, is sent by the - Diameter server to acknowledge the notification that the session has - been terminated. The Result-Code AVP MUST be present, and it MAY - contain an indication that an error occurred while servicing the STR. - - Upon sending or receipt of the STA, the Diameter server MUST release - all resources for the session indicated by the Session-Id AVP. Any - intermediate server in the Proxy-Chain MAY also release any - resources, if necessary. - - Message Format - - <STA> ::= < Diameter Header: 275, PXY > - < Session-Id > - { Result-Code } - { Origin-Host } - { Origin-Realm } - [ User-Name ] - * [ Class ] - [ Error-Message ] - [ Error-Reporting-Host ] - [ Failed-AVP ] - [ Origin-State-Id ] - * [ Redirect-Host ] - [ Redirect-Host-Usage ] - [ Redirect-Max-Cache-Time ] - * [ Proxy-Info ] - * [ AVP ] - -8.5. Aborting a Session - - A Diameter server may request that the access device stop providing - service for a particular session by issuing an Abort-Session-Request - (ASR). - - For example, the Diameter server that originally authorized the - session may be required to cause that session to be stopped for lack - of credit or other reasons that were not anticipated when the session - was first authorized. - - An access device that receives an ASR with Session-ID equal to a - currently active session MAY stop the session. Whether the access - device stops the session or not is implementation and/or - configuration dependent. For example, an access device may honor - ASRs from certain agents only. In any case, the access device MUST - - - -Fajardo, et al. Standards Track [Page 113] - -RFC 6733 Diameter Base Protocol October 2012 - - - respond with an Abort-Session-Answer, including a Result-Code AVP to - indicate what action it took. - -8.5.1. Abort-Session-Request - - The Abort-Session-Request (ASR), indicated by the Command Code set to - 274 and the message flags' 'R' bit set, may be sent by any Diameter - server or any Diameter proxy to the access device that is providing - session service, to request that the session identified by the - Session-Id be stopped. - - Message Format - - <ASR> ::= < Diameter Header: 274, REQ, PXY > - < Session-Id > - { Origin-Host } - { Origin-Realm } - { Destination-Realm } - { Destination-Host } - { Auth-Application-Id } - [ User-Name ] - [ Origin-State-Id ] - * [ Proxy-Info ] - * [ Route-Record ] - * [ AVP ] - -8.5.2. Abort-Session-Answer - - The Abort-Session-Answer (ASA), indicated by the Command Code set to - 274 and the message flags' 'R' bit clear, is sent in response to the - ASR. The Result-Code AVP MUST be present and indicates the - disposition of the request. - - If the session identified by Session-Id in the ASR was successfully - terminated, the Result-Code is set to DIAMETER_SUCCESS. If the - session is not currently active, the Result-Code is set to - DIAMETER_UNKNOWN_SESSION_ID. If the access device does not stop the - session for any other reason, the Result-Code is set to - DIAMETER_UNABLE_TO_COMPLY. - - - - - - - - - - - - -Fajardo, et al. Standards Track [Page 114] - -RFC 6733 Diameter Base Protocol October 2012 - - - Message Format - - <ASA> ::= < Diameter Header: 274, PXY > - < Session-Id > - { Result-Code } - { Origin-Host } - { Origin-Realm } - [ User-Name ] - [ Origin-State-Id ] - [ Error-Message ] - [ Error-Reporting-Host ] - [ Failed-AVP ] - * [ Redirect-Host ] - [ Redirect-Host-Usage ] - [ Redirect-Max-Cache-Time ] - * [ Proxy-Info ] - * [ AVP ] - -8.6. Inferring Session Termination from Origin-State-Id - - The Origin-State-Id is used to allow detection of terminated sessions - for which no STR would have been issued, due to unanticipated - shutdown of an access device. - - A Diameter client or access device increments the value of the - Origin-State-Id every time it is started or powered up. The new - Origin-State-Id is then sent in the CER/CEA message immediately upon - connection to the server. The Diameter server receiving the new - Origin-State-Id can determine whether the sending Diameter client had - abruptly shut down by comparing the old value of the Origin-State-Id - it has kept for that specific client is less than the new value and - whether it has un-terminated sessions originating from that client. - - An access device can also include the Origin-State-Id in request - messages other than the CER if there are relays or proxies in between - the access device and the server. In this case, however, the server - cannot discover that the access device has been restarted unless and - until it receives a new request from it. Therefore, this mechanism - is more opportunistic across proxies and relays. - - The Diameter server may assume that all sessions that were active - prior to detection of a client restart have been terminated. The - Diameter server MAY clean up all session state associated with such - lost sessions, and it MAY also issue STRs for all such lost sessions - that were authorized on upstream servers, to allow session state to - be cleaned up globally. - - - - - -Fajardo, et al. Standards Track [Page 115] - -RFC 6733 Diameter Base Protocol October 2012 - - -8.7. Auth-Request-Type AVP - - The Auth-Request-Type AVP (AVP Code 274) is of type Enumerated and is - included in application-specific auth requests to inform the peers - whether a user is to be authenticated only, authorized only, or both. - Note any value other than both MAY cause RADIUS interoperability - issues. The following values are defined: - - AUTHENTICATE_ONLY 1 - - The request being sent is for authentication only, and it MUST - contain the relevant application-specific authentication AVPs that - are needed by the Diameter server to authenticate the user. - - AUTHORIZE_ONLY 2 - - The request being sent is for authorization only, and it MUST - contain the application-specific authorization AVPs that are - necessary to identify the service being requested/offered. - - AUTHORIZE_AUTHENTICATE 3 - - The request contains a request for both authentication and - authorization. The request MUST include both the relevant - application-specific authentication information and authorization - information necessary to identify the service being requested/ - offered. - -8.8. Session-Id AVP - - The Session-Id AVP (AVP Code 263) is of type UTF8String and is used - to identify a specific session (see Section 8). All messages - pertaining to a specific session MUST include only one Session-Id - AVP, and the same value MUST be used throughout the life of a - session. When present, the Session-Id SHOULD appear immediately - following the Diameter header (see Section 3). - - The Session-Id MUST be globally and eternally unique, as it is meant - to uniquely identify a user session without reference to any other - information, and it may be needed to correlate historical - authentication information with accounting information. The - Session-Id includes a mandatory portion and an implementation-defined - portion; a recommended format for the implementation-defined portion - is outlined below. - - The Session-Id MUST begin with the sender's identity encoded in the - DiameterIdentity type (see Section 4.3.1). The remainder of the - Session-Id is delimited by a ";" character, and it MAY be any - - - -Fajardo, et al. Standards Track [Page 116] - -RFC 6733 Diameter Base Protocol October 2012 - - - sequence that the client can guarantee to be eternally unique; - however, the following format is recommended, (square brackets [] - indicate an optional element): - - <DiameterIdentity>;<high 32 bits>;<low 32 bits>[;<optional value>] - - <high 32 bits> and <low 32 bits> are decimal representations of the - high and low 32 bits of a monotonically increasing 64-bit value. The - 64-bit value is rendered in two part to simplify formatting by 32-bit - processors. At startup, the high 32 bits of the 64-bit value MAY be - initialized to the time in NTP format [RFC5905], and the low 32 bits - MAY be initialized to zero. This will for practical purposes - eliminate the possibility of overlapping Session-Ids after a reboot, - assuming the reboot process takes longer than a second. - Alternatively, an implementation MAY keep track of the increasing - value in non-volatile memory. - - - <optional value> is implementation specific, but it may include a - modem's device Id, a Layer 2 address, timestamp, etc. - - Example, in which there is no optional value: - - accesspoint7.example.com;1876543210;523 - - Example, in which there is an optional value: - - accesspoint7.example.com;1876543210;523;[email protected] - - The Session-Id is created by the Diameter application initiating the - session, which, in most cases, is done by the client. Note that a - Session-Id MAY be used for both the authentication, authorization, - and accounting commands of a given application. - -8.9. Authorization-Lifetime AVP - - The Authorization-Lifetime AVP (AVP Code 291) is of type Unsigned32 - and contains the maximum number of seconds of service to be provided - to the user before the user is to be re-authenticated and/or re- - authorized. Care should be taken when the Authorization-Lifetime - value is determined, since a low, non-zero value could create - significant Diameter traffic, which could congest both the network - and the agents. - - A value of zero (0) means that immediate re-auth is necessary by the - access device. The absence of this AVP, or a value of all ones - (meaning all bits in the 32-bit field are set to one) means no re- - auth is expected. - - - -Fajardo, et al. Standards Track [Page 117] - -RFC 6733 Diameter Base Protocol October 2012 - - - If both this AVP and the Session-Timeout AVP are present in a - message, the value of the latter MUST NOT be smaller than the - Authorization-Lifetime AVP. - - An Authorization-Lifetime AVP MAY be present in re-authorization - messages, and it contains the number of seconds the user is - authorized to receive service from the time the re-auth answer - message is received by the access device. - - This AVP MAY be provided by the client as a hint of the maximum - lifetime that it is willing to accept. The server MUST return a - value that is equal to, or smaller than, the one provided by the - client. - -8.10. Auth-Grace-Period AVP - - The Auth-Grace-Period AVP (AVP Code 276) is of type Unsigned32 and - contains the number of seconds the Diameter server will wait - following the expiration of the Authorization-Lifetime AVP before - cleaning up resources for the session. - -8.11. Auth-Session-State AVP - - The Auth-Session-State AVP (AVP Code 277) is of type Enumerated and - specifies whether state is maintained for a particular session. The - client MAY include this AVP in requests as a hint to the server, but - the value in the server's answer message is binding. The following - values are supported: - - STATE_MAINTAINED 0 - - This value is used to specify that session state is being - maintained, and the access device MUST issue a session termination - message when service to the user is terminated. This is the - default value. - - NO_STATE_MAINTAINED 1 - - This value is used to specify that no session termination messages - will be sent by the access device upon expiration of the - Authorization-Lifetime. - -8.12. Re-Auth-Request-Type AVP - - The Re-Auth-Request-Type AVP (AVP Code 285) is of type Enumerated and - is included in application-specific auth answers to inform the client - of the action expected upon expiration of the Authorization-Lifetime. - - - - -Fajardo, et al. Standards Track [Page 118] - -RFC 6733 Diameter Base Protocol October 2012 - - - If the answer message contains an Authorization-Lifetime AVP with a - positive value, the Re-Auth-Request-Type AVP MUST be present in an - answer message. The following values are defined: - - AUTHORIZE_ONLY 0 - - An authorization only re-auth is expected upon expiration of the - Authorization-Lifetime. This is the default value if the AVP is - not present in answer messages that include the Authorization- - Lifetime. - - AUTHORIZE_AUTHENTICATE 1 - - An authentication and authorization re-auth is expected upon - expiration of the Authorization-Lifetime. - -8.13. Session-Timeout AVP - - The Session-Timeout AVP (AVP Code 27) [RFC2865] is of type Unsigned32 - and contains the maximum number of seconds of service to be provided - to the user before termination of the session. When both the - Session-Timeout and the Authorization-Lifetime AVPs are present in an - answer message, the former MUST be equal to or greater than the value - of the latter. - - A session that terminates on an access device due to the expiration - of the Session-Timeout MUST cause an STR to be issued, unless both - the access device and the home server had previously agreed that no - session termination messages would be sent (see Section 8). - - A Session-Timeout AVP MAY be present in a re-authorization answer - message, and it contains the remaining number of seconds from the - beginning of the re-auth. - - A value of zero, or the absence of this AVP, means that this session - has an unlimited number of seconds before termination. - - This AVP MAY be provided by the client as a hint of the maximum - timeout that it is willing to accept. However, the server MAY return - a value that is equal to, or smaller than, the one provided by the - client. - -8.14. User-Name AVP - - The User-Name AVP (AVP Code 1) [RFC2865] is of type UTF8String, which - contains the User-Name, in a format consistent with the NAI - specification [RFC4282]. - - - - -Fajardo, et al. Standards Track [Page 119] - -RFC 6733 Diameter Base Protocol October 2012 - - -8.15. Termination-Cause AVP - - The Termination-Cause AVP (AVP Code 295) is of type Enumerated, and - is used to indicate the reason why a session was terminated on the - access device. The currently assigned values for this AVP can be - found in the IANA registry for Termination-Cause AVP Values - [IANATCV]. - -8.16. Origin-State-Id AVP - - The Origin-State-Id AVP (AVP Code 278), of type Unsigned32, is a - monotonically increasing value that is advanced whenever a Diameter - entity restarts with loss of previous state, for example, upon - reboot. Origin-State-Id MAY be included in any Diameter message, - including CER. - - A Diameter entity issuing this AVP MUST create a higher value for - this AVP each time its state is reset. A Diameter entity MAY set - Origin-State-Id to the time of startup, or it MAY use an incrementing - counter retained in non-volatile memory across restarts. - - The Origin-State-Id, if present, MUST reflect the state of the entity - indicated by Origin-Host. If a proxy modifies Origin-Host, it MUST - either remove Origin-State-Id or modify it appropriately as well. - Typically, Origin-State-Id is used by an access device that always - starts up with no active sessions; that is, any session active prior - to restart will have been lost. By including Origin-State-Id in a - message, it allows other Diameter entities to infer that sessions - associated with a lower Origin-State-Id are no longer active. If an - access device does not intend for such inferences to be made, it MUST - either not include Origin-State-Id in any message or set its value to - 0. - -8.17. Session-Binding AVP - - The Session-Binding AVP (AVP Code 270) is of type Unsigned32, and it - MAY be present in application-specific authorization answer messages. - If present, this AVP MAY inform the Diameter client that all future - application-specific re-auth and Session-Termination-Request messages - for this session MUST be sent to the same authorization server. - - - - - - - - - - - -Fajardo, et al. Standards Track [Page 120] - -RFC 6733 Diameter Base Protocol October 2012 - - - This field is a bit mask, and the following bits have been defined: - - RE_AUTH 1 - - When set, future re-auth messages for this session MUST NOT - include the Destination-Host AVP. When cleared, the default - value, the Destination-Host AVP MUST be present in all re-auth - messages for this session. - - STR 2 - - When set, the STR message for this session MUST NOT include the - Destination-Host AVP. When cleared, the default value, the - Destination-Host AVP MUST be present in the STR message for this - session. - - ACCOUNTING 4 - - When set, all accounting messages for this session MUST NOT - include the Destination-Host AVP. When cleared, the default - value, the Destination-Host AVP, if known, MUST be present in all - accounting messages for this session. - -8.18. Session-Server-Failover AVP - - The Session-Server-Failover AVP (AVP Code 271) is of type Enumerated - and MAY be present in application-specific authorization answer - messages that either do not include the Session-Binding AVP or - include the Session-Binding AVP with any of the bits set to a zero - value. If present, this AVP MAY inform the Diameter client that if a - re-auth or STR message fails due to a delivery problem, the Diameter - client SHOULD issue a subsequent message without the Destination-Host - AVP. When absent, the default value is REFUSE_SERVICE. - - The following values are supported: - - REFUSE_SERVICE 0 - - If either the re-auth or the STR message delivery fails, terminate - service with the user and do not attempt any subsequent attempts. - - - - - - - - - - - -Fajardo, et al. Standards Track [Page 121] - -RFC 6733 Diameter Base Protocol October 2012 - - - TRY_AGAIN 1 - - If either the re-auth or the STR message delivery fails, resend - the failed message without the Destination-Host AVP present. - - ALLOW_SERVICE 2 - - If re-auth message delivery fails, assume that re-authorization - succeeded. If STR message delivery fails, terminate the session. - - TRY_AGAIN_ALLOW_SERVICE 3 - - If either the re-auth or the STR message delivery fails, resend - the failed message without the Destination-Host AVP present. If - the second delivery fails for re-auth, assume re-authorization - succeeded. If the second delivery fails for STR, terminate the - session. - -8.19. Multi-Round-Time-Out AVP - - The Multi-Round-Time-Out AVP (AVP Code 272) is of type Unsigned32 and - SHOULD be present in application-specific authorization answer - messages whose Result-Code AVP is set to DIAMETER_MULTI_ROUND_AUTH. - This AVP contains the maximum number of seconds that the access - device MUST provide the user in responding to an authentication - request. - -8.20. Class AVP - - The Class AVP (AVP Code 25) is of type OctetString and is used by - Diameter servers to return state information to the access device. - When one or more Class AVPs are present in application-specific - authorization answer messages, they MUST be present in subsequent re- - authorization, session termination and accounting messages. Class - AVPs found in a re-authorization answer message override the ones - found in any previous authorization answer message. Diameter server - implementations SHOULD NOT return Class AVPs that require more than - 4096 bytes of storage on the Diameter client. A Diameter client that - receives Class AVPs whose size exceeds local available storage MUST - terminate the session. - -8.21. Event-Timestamp AVP - - The Event-Timestamp (AVP Code 55) is of type Time and MAY be included - in an Accounting-Request and Accounting-Answer messages to record the - time that the reported event occurred, in seconds since January 1, - 1900 00:00 UTC. - - - - -Fajardo, et al. Standards Track [Page 122] - -RFC 6733 Diameter Base Protocol October 2012 - - -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 [RFC2975] have been built into the - protocol in order minimize loss of accounting data in various fault - situations and under different assumptions about the capabilities of - the used devices. - -9.1. Server Directed Model - - The server directed model means that the device generating the - accounting data gets information from either the authorization server - (if contacted) or the accounting server regarding the way accounting - data shall be forwarded. This information includes accounting record - timeliness requirements. - - As discussed in [RFC2975], real-time transfer of accounting records - is a requirement, such as the need to perform credit-limit checks and - fraud detection. Note that batch accounting is not a requirement, - and is therefore not supported by Diameter. Should batched - accounting be required in the future, a new Diameter application will - need to be created, or it could be handled using another protocol. - Note, however, that even if at the Diameter layer, accounting - requests are processed one by one; transport protocols used under - Diameter typically batch several requests in the same packet under - heavy traffic conditions. This may be sufficient for many - applications. - - The authorization server (chain) directs the selection of proper - transfer strategy, based on its knowledge of the user and - relationships of roaming partnerships. The server (or agents) uses - the Acct-Interim-Interval and Accounting-Realtime-Required AVPs to - control the operation of the Diameter peer operating as a client. - The Acct-Interim-Interval AVP, when present, instructs the Diameter - node acting as a client to produce accounting records continuously - even during a session. Accounting-Realtime-Required AVP is used to - control the behavior of the client when the transfer of accounting - records from the Diameter client is delayed or unsuccessful. - - The Diameter accounting server MAY override the interim interval or - the real-time requirements by including the Acct-Interim-Interval or - Accounting-Realtime-Required AVP in the Accounting-Answer message. - When one of these AVPs is present, the latest value received SHOULD - be used in further accounting activities for the same session. - - - - - - -Fajardo, et al. Standards Track [Page 123] - -RFC 6733 Diameter Base Protocol October 2012 - - -9.2. Protocol Messages - - A Diameter node that receives a successful authentication and/or - authorization message from the Diameter server SHOULD collect - accounting information for the session. The Accounting-Request - message is used to transmit the accounting information to the - Diameter server, which MUST reply with the Accounting-Answer message - to confirm reception. The Accounting-Answer message includes the - Result-Code AVP, which MAY indicate that an error was present in the - accounting message. The value of the Accounting-Realtime-Required - AVP received earlier for the session in question may indicate that - the user's session has to be terminated when a rejected Accounting- - Request message was received. - -9.3. Accounting Application Extension and Requirements - - Each Diameter application (e.g., NASREQ, Mobile IP) SHOULD define its - service-specific AVPs that MUST be present in the Accounting-Request - message in a section titled "Accounting AVPs". The application MUST - assume that the AVPs described in this document will be present in - all Accounting messages, so only their respective service-specific - AVPs need to be defined in that section. - - Applications have the option of using one or both of the following - accounting application extension models: - - Split Accounting Service - - The accounting message will carry the Application Id of the - Diameter base accounting application (see Section 2.4). - Accounting messages may be routed to Diameter nodes other than the - corresponding Diameter application. These nodes might be - centralized accounting servers that provide accounting service for - multiple different Diameter applications. These nodes MUST - advertise the Diameter base accounting Application Id during - capabilities exchange. - - Coupled Accounting Service - - The accounting message will carry the Application Id of the - application that is using it. The application itself will process - the received accounting records or forward them to an accounting - server. There is no accounting application advertisement required - during capabilities exchange, and the accounting messages will be - routed the same way as any of the other application messages. - - In cases where an application does not define its own accounting - service, it is preferred that the split accounting model be used. - - - -Fajardo, et al. Standards Track [Page 124] - -RFC 6733 Diameter Base Protocol October 2012 - - -9.4. Fault Resilience - - Diameter base protocol mechanisms are used to overcome small message - loss and network faults of a temporary nature. - - Diameter peers acting as clients MUST implement the use of failover - to guard against server failures and certain network failures. - Diameter peers acting as agents or related off-line processing - systems MUST detect duplicate accounting records caused by the - sending of the same record to several servers and duplication of - messages in transit. This detection MUST be based on the inspection - of the Session-Id and Accounting-Record-Number AVP pairs. Appendix C - discusses duplicate detection needs and implementation issues. - - Diameter clients MAY have non-volatile memory for the safe storage of - accounting records over reboots or extended network failures, network - partitions, and server failures. If such memory is available, the - client SHOULD store new accounting records there as soon as the - records are created and until a positive acknowledgement of their - reception from the Diameter server has been received. Upon a reboot, - the client MUST start sending the records in the non-volatile memory - to the accounting server with the appropriate modifications in - termination cause, session length, and other relevant information in - the records. - - A further application of this protocol may include AVPs to control - the maximum number of accounting records that may be stored in the - Diameter client without committing them to the non-volatile memory or - transferring them to the Diameter server. - - The client SHOULD NOT remove the accounting data from any of its - memory areas before the correct Accounting-Answer has been received. - The client MAY remove the oldest, undelivered, or as yet - unacknowledged accounting data if it runs out of resources such as - memory. It is an implementation-dependent matter for the client to - accept new sessions under this condition. - -9.5. Accounting Records - - In all accounting records, the Session-Id AVP MUST be present; the - User-Name AVP MUST be present if it is available to the Diameter - client. - - Different types of accounting records are sent depending on the - actual type of accounted service and the authorization server's - directions for interim accounting. If the accounted service is a - - - - - -Fajardo, et al. Standards Track [Page 125] - -RFC 6733 Diameter Base Protocol October 2012 - - - one-time event, meaning that the start and stop of the event are - simultaneous, then the Accounting-Record-Type AVP MUST be present and - set to the value EVENT_RECORD. - - If the accounted service is of a measurable length, then the AVP MUST - use the values START_RECORD, STOP_RECORD, and possibly, - INTERIM_RECORD. If the authorization server has not directed interim - accounting to be enabled for the session, two accounting records MUST - be generated for each service of type session. When the initial - Accounting-Request for a given session is sent, the Accounting- - Record-Type AVP MUST be set to the value START_RECORD. When the last - Accounting-Request is sent, the value MUST be STOP_RECORD. - - If the authorization server has directed interim accounting to be - enabled, the Diameter client MUST produce additional records between - the START_RECORD and STOP_RECORD, marked INTERIM_RECORD. The - production of these records is directed by Acct-Interim-Interval as - well as any re-authentication or re-authorization of the session. - The Diameter client MUST overwrite any previous interim accounting - records that are locally stored for delivery, if a new record is - being generated for the same session. This ensures that only one - pending interim record can exist on an access device for any given - session. - - A particular value of Accounting-Sub-Session-Id MUST appear only in - one sequence of accounting records from a Diameter client, except for - the purposes of retransmission. The one sequence that is sent MUST - be either one record with Accounting-Record-Type AVP set to the value - EVENT_RECORD or several records starting with one having the value - START_RECORD, followed by zero or more INTERIM_RECORDs and a single - STOP_RECORD. A particular Diameter application specification MUST - define the type of sequences that MUST be used. - -9.6. Correlation of Accounting Records - - If an application uses accounting messages, it can correlate - accounting records with a specific application session by using the - Session-Id of the particular application session in the accounting - messages. Accounting messages MAY also use a different Session-Id - from that of the application sessions, in which case, other session- - related information is needed to perform correlation. - - In cases where an application requires multiple accounting sub- - sessions, an Accounting-Sub-Session-Id AVP is used to differentiate - each sub-session. The Session-Id would remain constant for all sub- - sessions and is used to correlate all the sub-sessions to a - particular application session. Note that receiving a STOP_RECORD - - - - -Fajardo, et al. Standards Track [Page 126] - -RFC 6733 Diameter Base Protocol October 2012 - - - 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. - - There are also cases where an application needs to correlate multiple - application sessions into a single accounting record; the accounting - record may span multiple different Diameter applications and sessions - used by the same user at a given time. In such cases, the Acct- - Multi-Session-Id AVP is used. The Acct-Multi-Session-Id AVP SHOULD - be signaled by the server to the access device (typically, during - authorization) when it determines that a request belongs to an - existing session. The access device MUST then include the Acct- - Multi-Session-Id AVP in all subsequent accounting messages. - - The Acct-Multi-Session-Id AVP MAY include the value of the original - Session-Id. Its contents are implementation specific, but the MUST - be globally unique across other Acct-Multi-Session-Ids 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 it 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. - - In addition to the AVPs listed below, Accounting-Request messages - SHOULD include service-specific accounting AVPs. - - - - - - - - - - - - -Fajardo, et al. Standards Track [Page 127] - -RFC 6733 Diameter Base Protocol October 2012 - - - Message Format - - <ACR> ::= < Diameter Header: 271, REQ, PXY > - < Session-Id > - { Origin-Host } - { Origin-Realm } - { Destination-Realm } - { Accounting-Record-Type } - { Accounting-Record-Number } - [ Acct-Application-Id ] - [ Vendor-Specific-Application-Id ] - [ User-Name ] - [ Destination-Host ] - [ Accounting-Sub-Session-Id ] - [ Acct-Session-Id ] - [ Acct-Multi-Session-Id ] - [ Acct-Interim-Interval ] - [ Accounting-Realtime-Required ] - [ Origin-State-Id ] - [ Event-Timestamp ] - * [ Proxy-Info ] - * [ Route-Record ] - * [ AVP ] - -9.7.2. Accounting-Answer - - The Accounting-Answer (ACA) command, indicated by the Command Code - field set to 271 and the Command Flags' 'R' bit cleared, is used to - acknowledge an Accounting-Request command. The Accounting-Answer - command contains the same Session-Id as the corresponding request. - - Only the target Diameter server, known as the home Diameter server, - SHOULD respond with the Accounting-Answer command. - - In addition to the AVPs listed below, Accounting-Answer messages - SHOULD include service-specific accounting AVPs. - - - - - - - - - - - - - - - -Fajardo, et al. Standards Track [Page 128] - -RFC 6733 Diameter Base Protocol October 2012 - - - Message Format - - <ACA> ::= < Diameter Header: 271, PXY > - < Session-Id > - { Result-Code } - { Origin-Host } - { Origin-Realm } - { Accounting-Record-Type } - { Accounting-Record-Number } - [ Acct-Application-Id ] - [ Vendor-Specific-Application-Id ] - [ User-Name ] - [ Accounting-Sub-Session-Id ] - [ Acct-Session-Id ] - [ Acct-Multi-Session-Id ] - [ Error-Message ] - [ Error-Reporting-Host ] - [ Failed-AVP ] - [ Acct-Interim-Interval ] - [ Accounting-Realtime-Required ] - [ Origin-State-Id ] - [ Event-Timestamp ] - * [ Proxy-Info ] - * [ AVP ] - -9.8. Accounting AVPs - - This section contains AVPs that describe accounting usage information - related to a specific session. - -9.8.1. Accounting-Record-Type AVP - - The Accounting-Record-Type AVP (AVP Code 480) is of type Enumerated - and contains the type of accounting record being sent. The following - values are currently defined for the Accounting-Record-Type AVP: - - EVENT_RECORD 1 - - An Accounting Event Record is used to indicate that a one-time - event has occurred (meaning that the start and end of the event - are simultaneous). This record contains all information relevant - to the service, and it is the only record of the service. - - - - - - - - - -Fajardo, et al. Standards Track [Page 129] - -RFC 6733 Diameter Base Protocol October 2012 - - - START_RECORD 2 - - 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. - - INTERIM_RECORD 3 - - An Interim Accounting Record contains cumulative accounting - information for an existing accounting session. Interim - Accounting Records SHOULD be sent every time a re-authentication - or re-authorization occurs. Further, additional interim record - triggers MAY be defined by application-specific Diameter - applications. The selection of whether to use INTERIM_RECORD - records is done by the Acct-Interim-Interval AVP. - - STOP_RECORD 4 - - An Accounting Stop Record is sent to terminate an accounting - session and contains cumulative accounting information relevant to - the existing session. - -9.8.2. Acct-Interim-Interval AVP - - The Acct-Interim-Interval AVP (AVP Code 85) is of type Unsigned32 and - is sent from the Diameter home authorization server to the Diameter - client. The client uses information in this AVP to decide how and - when to produce accounting records. With different values in this - AVP, service sessions can result in one, two, or two+N accounting - records, based on the needs of the home organization. The following - accounting record production behavior is directed by the inclusion of - this AVP: - - 1. The omission of the Acct-Interim-Interval AVP or its inclusion - with Value field set to 0 means that EVENT_RECORD, START_RECORD, - and STOP_RECORD are produced, as appropriate for the service. - - 2. The inclusion of the AVP with Value field set to a non-zero value - means that INTERIM_RECORD records MUST be produced between the - START_RECORD and STOP_RECORD records. The Value field of this - AVP is the nominal interval between these records in seconds. - The Diameter node that originates the accounting information, - known as the client, MUST produce the first INTERIM_RECORD record - roughly at the time when this nominal interval has elapsed from - - - - - -Fajardo, et al. Standards Track [Page 130] - -RFC 6733 Diameter Base Protocol October 2012 - - - the START_RECORD, the next one again as the interval has elapsed - once more, and so on until the session ends and a STOP_RECORD - record is produced. - - The client MUST ensure that the interim record production times - are randomized so that large accounting message storms are not - created either among records or around a common service start - time. - -9.8.3. Accounting-Record-Number AVP - - The Accounting-Record-Number AVP (AVP Code 485) is of type Unsigned32 - and identifies this record within one session. As Session-Id AVPs - are globally unique, the combination of Session-Id and Accounting- - Record-Number AVPs is also globally unique and can be used in - matching accounting records with confirmations. An easy way to - produce unique numbers is to set the value to 0 for records of type - EVENT_RECORD and START_RECORD and set the value to 1 for the first - INTERIM_RECORD, 2 for the second, and so on until the value for - STOP_RECORD is one more than for the last INTERIM_RECORD. - -9.8.4. Acct-Session-Id AVP - - The Acct-Session-Id AVP (AVP Code 44) is of type OctetString is only - used when RADIUS/Diameter translation occurs. This AVP contains the - contents of the RADIUS Acct-Session-Id attribute. - -9.8.5. Acct-Multi-Session-Id AVP - - The Acct-Multi-Session-Id AVP (AVP Code 50) is of type UTF8String, - following the format specified in Section 8.8. The Acct-Multi- - Session-Id AVP is used to link multiple related accounting sessions, - where each session would have a unique Session-Id but the same Acct- - Multi-Session-Id AVP. This AVP MAY be returned by the Diameter - server in an authorization answer, and it MUST be used in all - accounting messages for the given session. - -9.8.6. Accounting-Sub-Session-Id AVP - - The Accounting-Sub-Session-Id AVP (AVP Code 287) is of type - Unsigned64 and contains the accounting sub-session identifier. The - combination of the Session-Id and this AVP MUST be unique per sub- - session, and the value of this AVP MUST be monotonically increased by - one for all new sub-sessions. The absence of this AVP implies no - sub-sessions are in use, with the exception of an Accounting-Request - whose Accounting-Record-Type is set to STOP_RECORD. A STOP_RECORD - message with no Accounting-Sub-Session-Id AVP present will signal the - termination of all sub-sessions for a given Session-Id. - - - -Fajardo, et al. Standards Track [Page 131] - -RFC 6733 Diameter Base Protocol October 2012 - - -9.8.7. Accounting-Realtime-Required AVP - - The Accounting-Realtime-Required AVP (AVP Code 483) is of type - Enumerated and is sent from the Diameter home authorization server to - the Diameter client or in the Accounting-Answer from the accounting - server. The client uses information in this AVP to decide what to do - if the sending of accounting records to the accounting server has - been temporarily prevented due to, for instance, a network problem. - - DELIVER_AND_GRANT 1 - - The AVP with Value field set to DELIVER_AND_GRANT means that the - service MUST only be granted as long as there is a connection to - an accounting server. Note that the set of alternative accounting - servers are treated as one server in this sense. Having to move - the accounting record stream to a backup server is not a reason to - discontinue the service to the user. - - GRANT_AND_STORE 2 - - The AVP with Value field set to GRANT_AND_STORE means that service - SHOULD be granted if there is a connection, or as long as records - can still be stored as described in Section 9.4. - - This is the default behavior if the AVP isn't included in the - reply from the authorization server. - - GRANT_AND_LOSE 3 - - The AVP with Value field set to GRANT_AND_LOSE means that service - SHOULD be granted even if the records cannot be delivered or - stored. - -10. AVP Occurrence Tables - - The following tables present the AVPs defined in this document and - specify in which Diameter messages they MAY or MAY NOT be present. - AVPs that occur only inside a Grouped AVP are not shown in these - tables. - - The tables use the following symbols: - - 0 The AVP MUST NOT be present in the message. - - 0+ Zero or more instances of the AVP MAY be present in the - message. - - - - - -Fajardo, et al. Standards Track [Page 132] - -RFC 6733 Diameter Base Protocol October 2012 - - - 0-1 Zero or one instance of the AVP MAY be present in the message. - It is considered an error if there are more than one instance - of the AVP. - - 1 One instance of the AVP MUST be present in the message. - - 1+ At least one instance of the AVP MUST be present in the - message. - -10.1. Base Protocol Command AVP Table - - The table in this section is limited to the non-Accounting Command - Codes defined in this specification. - - +-----------------------------------------------+ - | 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 |0-1|0 |0-1|0 |0-1|0 |0-1|0 |0-1|0 |0-1| - 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 | - - - - - - - - - - -Fajardo, et al. Standards Track [Page 133] - -RFC 6733 Diameter Base Protocol October 2012 - - - Origin-Host |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 | - Origin-Realm |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 | - Origin-State-Id |0-1|0-1|0 |0 |0-1|0-1|0-1|0-1|0-1|0-1|0-1|0-1| - Product-Name |1 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | - Proxy-Info |0 |0 |0 |0 |0 |0 |0+ |0+ |0+ |0+ |0+ |0+ | - Redirect-Host |0 |0 |0 |0 |0 |0 |0 |0+ |0 |0+ |0 |0+ | - Redirect-Host-Usage |0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1| - Redirect-Max-Cache- |0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1| - Time | | | | | | | | | | | | | - Result-Code |0 |1 |0 |1 |0 |1 |0 |1 |0 |1 |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 | - Vendor-Specific- |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | - Application-Id | | | | | | | | | | | | | - --------------------+---+---+---+---+---+---+---+---+---+---+---+---+ - -10.2. Accounting AVP Table - - The table in this section is used to represent which AVPs defined in - this document are to be present in the Accounting messages. These - AVP occurrence requirements are guidelines, which may be expanded, - and/or overridden by application-specific requirements in the - Diameter applications documents. - - - - - - - - - - - - - - - - - - - -Fajardo, et al. Standards Track [Page 134] - -RFC 6733 Diameter Base Protocol October 2012 - - - +-----------+ - | 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 | - Failed-AVP | 0 | 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 | 0 | - User-Name | 0-1 | 0-1 | - Vendor-Specific-Application-Id| 0-1 | 0-1 | - ------------------------------+-----+-----+ - -11. IANA Considerations - - This section provides guidance to the Internet Assigned Numbers - Authority (IANA) regarding registration of values related to the - Diameter protocol, in accordance with [RFC5226]. Existing IANA - registries and assignments put in place by RFC 3588 remain the same - unless explicitly updated or deprecated in this section. - -11.1. AVP Header - - As defined in Section 4, the AVP header contains three fields that - require IANA namespace management: the AVP Code, Vendor-ID, and Flags - fields. - - - - - - -Fajardo, et al. Standards Track [Page 135] - -RFC 6733 Diameter Base Protocol October 2012 - - -11.1.1. AVP Codes - - There are multiple namespaces. Vendors can have their own AVP Codes - namespace that will be identified by their Vendor-ID (also known as - Enterprise-Number), and they control the assignments of their vendor- - specific AVP Codes within their own namespace. The absence of a - Vendor-ID or a Vendor-ID value of zero (0) identifies the IETF AVP - Codes namespace, which is under IANA control. The AVP Codes and - sometimes possible values in an AVP are controlled and maintained by - IANA. AVP Code 0 is not used. AVP Codes 1-255 are managed - separately as RADIUS Attribute Types. Where a Vendor-Specific AVP is - implemented by more than one vendor, allocation of global AVPs should - be encouraged instead. - - AVPs may be allocated following Expert Review (by a Designated - Expert) with Specification Required [RFC5226]. A block allocation - (release of more than three AVPs at a time for a given purpose) - requires IETF Review [RFC5226]. - -11.1.2. AVP Flags - - Section 4.1 describes the existing AVP Flags. The remaining bits can - only be assigned via a Standards Action [RFC5226]. - -11.2. Diameter Header - -11.2.1. Command Codes - - For the Diameter header, the Command Code namespace allocation has - changed. The new allocation rules are as follows: - - The Command Code values 256 - 8,388,607 (0x100 to 0x7fffff) are - for permanent, standard commands, allocated by IETF Review - [RFC5226]. - - The values 8,388,608 - 16,777,213 (0x800000 - 0xfffffd) are - reserved for vendor-specific Command Codes, to be allocated on a - First Come, First Served basis by IANA [RFC5226]. The request to - IANA for a Vendor-Specific Command Code SHOULD include a reference - to a publicly available specification that documents the command - in sufficient detail to aid in interoperability between - independent implementations. If the specification cannot be made - publicly available, the request for a vendor-specific Command Code - MUST include the contact information of persons and/or entities - responsible for authoring and maintaining the command. - - - - - - -Fajardo, et al. Standards Track [Page 136] - -RFC 6733 Diameter Base Protocol October 2012 - - - The values 16,777,214 and 16,777,215 (hexadecimal values 0xfffffe - - 0xffffff) are reserved for experimental commands. As these - codes are only for experimental and testing purposes, no guarantee - is made for interoperability between Diameter peers using - experimental commands. - -11.2.2. Command Flags - - Section 3 describes the existing Command Flags field. The remaining - bits can only be assigned via a Standards Action [RFC5226]. - -11.3. AVP Values - - For AVP values, the Experimental-Result-Code AVP value allocation has - been added; see Section 11.3.1. The old AVP value allocation rule, - IETF Consensus, has been updated to IETF Review as per [RFC5226], and - affected AVPs are listed as reminders. - -11.3.1. Experimental-Result-Code AVP - - Values for this AVP are purely local to the indicated vendor, and no - IANA registry is maintained for them. - -11.3.2. Result-Code AVP Values - - New values are available for assignment via IETF Review [RFC5226]. - -11.3.3. Accounting-Record-Type AVP Values - - New values are available for assignment via IETF Review [RFC5226]. - -11.3.4. Termination-Cause AVP Values - - New values are available for assignment via IETF Review [RFC5226]. - -11.3.5. Redirect-Host-Usage AVP Values - - New values are available for assignment via IETF Review [RFC5226]. - -11.3.6. Session-Server-Failover AVP Values - - New values are available for assignment via IETF Review [RFC5226]. - -11.3.7. Session-Binding AVP Values - - New values are available for assignment via IETF Review [RFC5226]. - - - - - -Fajardo, et al. Standards Track [Page 137] - -RFC 6733 Diameter Base Protocol October 2012 - - -11.3.8. Disconnect-Cause AVP Values - - New values are available for assignment via IETF Review [RFC5226]. - -11.3.9. Auth-Request-Type AVP Values - - New values are available for assignment via IETF Review [RFC5226]. - -11.3.10. Auth-Session-State AVP Values - - New values are available for assignment via IETF Review [RFC5226]. - -11.3.11. Re-Auth-Request-Type AVP Values - - New values are available for assignment via IETF Review [RFC5226]. - -11.3.12. Accounting-Realtime-Required AVP Values - - New values are available for assignment via IETF Review [RFC5226]. - -11.3.13. Inband-Security-Id AVP (code 299) - - The use of this AVP has been deprecated. - -11.4. _diameters Service Name and Port Number Registration - - IANA has registered the "_diameters" service name and assigned port - numbers for TLS/TCP and DTLS/SCTP according to the guidelines given - in [RFC6335]. - - Service Name: _diameters - - Transport Protocols: TCP, SCTP - - Assignee: IESG <[email protected]> - - Contact: IETF Chair <[email protected]> - - Description: Diameter over TLS/TCP and DTLS/SCTP - - Reference: RFC 6733 - - Port Number: 5868, from the User Range - - - - - - - - -Fajardo, et al. Standards Track [Page 138] - -RFC 6733 Diameter Base Protocol October 2012 - - -11.5. SCTP Payload Protocol Identifiers - - Two SCTP payload protocol identifiers have been registered in the - SCTP Payload Protocol Identifiers registry: - - - Value | SCTP Payload Protocol Identifier - -------|----------------------------------- - 46 | Diameter in a SCTP DATA chunk - 47 | Diameter in a DTLS/SCTP DATA chunk - - -11.6. S-NAPTR Parameters - - The following tag has been registered in the S-NAPTR Application - Protocol Tags registry: - - Tag | Protocol - -------------------|--------- - diameter.dtls.sctp | DTLS/SCTP - -12. Diameter Protocol-Related Configurable Parameters - - This section contains the configurable parameters that are found - throughout this document: - - Diameter Peer - - A Diameter entity MAY communicate with peers that are statically - configured. A statically configured Diameter peer would require - that either the IP address or the fully qualified domain name - (FQDN) be supplied, which would then be used to resolve through - DNS. - - Routing Table - - A Diameter proxy server routes messages based on the realm portion - of a Network Access Identifier (NAI). The server MUST have a - table of Realm Names, and the address of the peer to which the - message must be forwarded. The routing table MAY also include a - "default route", which is typically used for all messages that - cannot be locally processed. - - Tc timer - - The Tc timer controls the frequency that transport connection - attempts are done to a peer with whom no active transport - connection exists. The recommended value is 30 seconds. - - - -Fajardo, et al. Standards Track [Page 139] - -RFC 6733 Diameter Base Protocol October 2012 - - -13. Security Considerations - - The Diameter base protocol messages SHOULD be secured by using TLS - [RFC5246] or DTLS/SCTP [RFC6083]. Additional security mechanisms - such as IPsec [RFC4301] MAY also be deployed to secure connections - between peers. However, all Diameter base protocol implementations - MUST support the use of TLS/TCP and DTLS/SCTP, and the Diameter - protocol MUST NOT be used without one of TLS, DTLS, or IPsec. - - If a Diameter connection is to be protected via TLS/TCP and DTLS/SCTP - or IPsec, then TLS/TCP and DTLS/SCTP or IPsec/IKE SHOULD begin prior - to any Diameter message exchange. All security parameters for TLS/ - TCP and DTLS/SCTP or IPsec are configured independent of the Diameter - protocol. All Diameter messages will be sent through the TLS/TCP and - DTLS/SCTP or IPsec connection after a successful setup. - - For TLS/TCP and DTLS/SCTP connections to be established in the open - state, the CER/CEA exchange MUST include an Inband-Security-ID AVP - with a value of TLS/TCP and DTLS/SCTP. The TLS/TCP and DTLS/SCTP - handshake will begin when both ends successfully reach the open - state, after completion of the CER/CEA exchange. If the TLS/TCP and - DTLS/SCTP handshake is successful, all further messages will be sent - via TLS/TCP and DTLS/SCTP. If the handshake fails, both ends MUST - move to the closed state. See Section 13.1 for more details. - -13.1. TLS/TCP and DTLS/SCTP Usage - - Diameter nodes using TLS/TCP and DTLS/SCTP for security MUST mutually - authenticate as part of TLS/TCP and DTLS/SCTP session establishment. - In order to ensure mutual authentication, the Diameter node acting as - the TLS/TCP and DTLS/SCTP server MUST request a certificate from the - Diameter node acting as TLS/TCP and DTLS/SCTP client, and the - Diameter node acting as the TLS/TCP and DTLS/SCTP client MUST be - prepared to supply a certificate on request. - - Diameter nodes MUST be able to negotiate the following TLS/TCP and - DTLS/SCTP 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/TCP and - DTLS/SCTP cipher suite: - - TLS_RSA_WITH_AES_128_CBC_SHA - - - - - -Fajardo, et al. Standards Track [Page 140] - -RFC 6733 Diameter Base Protocol October 2012 - - - Note that it is quite possible that support for the - TLS_RSA_WITH_AES_128_CBC_SHA cipher suite will be REQUIRED at some - future date. Diameter nodes MAY negotiate other TLS/TCP and DTLS/ - SCTP cipher suites. - - If public key certificates are used for Diameter security (for - example, with TLS), the value of the expiration times in the routing - and peer tables MUST NOT be greater than the expiry time in the - relevant certificates. - -13.2. Peer-to-Peer Considerations - - As with any peer-to-peer protocol, proper configuration of the trust - model within a Diameter peer is essential to security. When - certificates are used, it is necessary to configure the root - certificate authorities trusted by the Diameter peer. These root CAs - are likely to be unique to Diameter usage and distinct from the root - CAs that might be trusted for other purposes such as Web browsing. - In general, it is expected that those root CAs will be configured so - as to reflect the business relationships between the organization - hosting the Diameter peer and other organizations. As a result, a - Diameter peer will typically not be configured to allow connectivity - with any arbitrary peer. With certificate authentication, Diameter - peers may not be known beforehand and therefore peer discovery may be - required. - -13.3. AVP Considerations - - Diameter AVPs often contain security-sensitive data; for example, - user passwords and location data, network addresses and cryptographic - keys. The following AVPs defined in this document are considered to - be security-sensitive: - - o Acct-Interim-Interval - - o Accounting-Realtime-Required - - o Acct-Multi-Session-Id - - o Accounting-Record-Number - - o Accounting-Record-Type - - o Accounting-Session-Id - - o Accounting-Sub-Session-Id - - o Class - - - -Fajardo, et al. Standards Track [Page 141] - -RFC 6733 Diameter Base Protocol October 2012 - - - o Session-Id - - o Session-Binding - - o Session-Server-Failover - - o User-Name - - Diameter messages containing these or any other AVPs considered to be - security-sensitive MUST only be sent protected via mutually - authenticated TLS or IPsec. In addition, those messages MUST NOT be - sent via intermediate nodes unless there is end-to-end security - between the originator and recipient or the originator has locally - trusted configuration that indicates that end-to-end security is not - needed. For example, end-to-end security may not be required in the - case where an intermediary node is known to be operated as part of - the same administrative domain as the endpoints so that an ability to - successfully compromise the intermediary would imply a high - probability of being able to compromise the endpoints as well. Note - that no end-to-end security mechanism is specified in this document. - -14. References - -14.1. Normative References - - [FLOATPOINT] - Institute of Electrical and Electronics Engineers, "IEEE - Standard for Binary Floating-Point Arithmetic, ANSI/IEEE - Standard 754-1985", August 1985. - - [IANAADFAM] - IANA, "Address Family Numbers", - <http://www.iana.org/assignments/address-family-numbers>. - - [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, - September 1981. - - [RFC0793] Postel, J., "Transmission Control Protocol", STD 7, - RFC 793, September 1981. - - [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate - Requirement Levels", BCP 14, RFC 2119, March 1997. - - [RFC3492] Costello, A., "Punycode: A Bootstring encoding of Unicode - for Internationalized Domain Names in Applications - (IDNA)", RFC 3492, March 2003. - - - - - -Fajardo, et al. Standards Track [Page 142] - -RFC 6733 Diameter Base Protocol October 2012 - - - [RFC3539] Aboba, B. and J. Wood, "Authentication, Authorization and - Accounting (AAA) Transport Profile", RFC 3539, June 2003. - - [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO - 10646", STD 63, RFC 3629, November 2003. - - [RFC3958] Daigle, L. and A. Newton, "Domain-Based Application - Service Location Using SRV RRs and the Dynamic Delegation - Discovery Service (DDDS)", RFC 3958, January 2005. - - [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform - Resource Identifier (URI): Generic Syntax", STD 66, - RFC 3986, January 2005. - - [RFC4004] Calhoun, P., Johansson, T., Perkins, C., Hiller, T., and - P. McCann, "Diameter Mobile IPv4 Application", RFC 4004, - August 2005. - - [RFC4005] Calhoun, P., Zorn, G., Spence, D., and D. Mitton, - "Diameter Network Access Server Application", RFC 4005, - August 2005. - - [RFC4006] Hakala, H., Mattila, L., Koskinen, J-P., Stura, M., and J. - Loughney, "Diameter Credit-Control Application", RFC 4006, - August 2005. - - [RFC4086] Eastlake, D., Schiller, J., and S. Crocker, "Randomness - Requirements for Security", BCP 106, RFC 4086, June 2005. - - [RFC4282] Aboba, B., Beadles, M., Arkko, J., and P. Eronen, "The - Network Access Identifier", RFC 4282, December 2005. - - [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing - Architecture", RFC 4291, February 2006. - - [RFC4960] Stewart, R., "Stream Control Transmission Protocol", - RFC 4960, September 2007. - - [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an - IANA Considerations Section in RFCs", BCP 26, RFC 5226, - May 2008. - - [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax - Specifications: ABNF", STD 68, RFC 5234, January 2008. - - [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security - (TLS) Protocol Version 1.2", RFC 5246, August 2008. - - - - -Fajardo, et al. Standards Track [Page 143] - -RFC 6733 Diameter Base Protocol October 2012 - - - [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., - Housley, R., and W. Polk, "Internet X.509 Public Key - Infrastructure Certificate and Certificate Revocation List - (CRL) Profile", RFC 5280, May 2008. - - [RFC5729] Korhonen, J., Jones, M., Morand, L., and T. Tsou, - "Clarifications on the Routing of Diameter Requests Based - on the Username and the Realm", RFC 5729, December 2009. - - [RFC5890] Klensin, J., "Internationalized Domain Names for - Applications (IDNA): Definitions and Document Framework", - RFC 5890, August 2010. - - [RFC5891] Klensin, J., "Internationalized Domain Names in - Applications (IDNA): Protocol", RFC 5891, August 2010. - - [RFC6083] Tuexen, M., Seggelmann, R., and E. Rescorla, "Datagram - Transport Layer Security (DTLS) for Stream Control - Transmission Protocol (SCTP)", RFC 6083, January 2011. - - [RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer - Security Version 1.2", RFC 6347, January 2012. - - [RFC6408] Jones, M., Korhonen, J., and L. Morand, "Diameter - Straightforward-Naming Authority Pointer (S-NAPTR) Usage", - RFC 6408, November 2011. - -14.2. Informative References - - [ENTERPRISE] IANA, "SMI Network Management Private Enterprise - Codes", - <http://www.iana.org/assignments/enterprise-numbers>. - - [IANATCV] IANA, "Termination-Cause AVP Values (code 295)", - <http://www.iana.org/assignments/aaa-parameters/ - aaa-parameters.xml#aaa-parameters-16>. - - [RFC1492] Finseth, C., "An Access Control Protocol, Sometimes - Called TACACS", RFC 1492, July 1993. - - [RFC1661] Simpson, W., "The Point-to-Point Protocol (PPP)", - STD 51, RFC 1661, July 1994. - - [RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: - Keyed-Hashing for Message Authentication", RFC 2104, - February 1997. - - - - - -Fajardo, et al. Standards Track [Page 144] - -RFC 6733 Diameter Base Protocol October 2012 - - - [RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR - for specifying the location of services (DNS SRV)", - RFC 2782, February 2000. - - [RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson, - "Remote Authentication Dial In User Service (RADIUS)", - RFC 2865, June 2000. - - [RFC2866] Rigney, C., "RADIUS Accounting", RFC 2866, June 2000. - - [RFC2869] Rigney, C., Willats, W., and P. Calhoun, "RADIUS - Extensions", RFC 2869, June 2000. - - [RFC2881] Mitton, D. and M. Beadles, "Network Access Server - Requirements Next Generation (NASREQNG) NAS Model", - RFC 2881, July 2000. - - [RFC2975] Aboba, B., Arkko, J., and D. Harrington, "Introduction - to Accounting Management", RFC 2975, October 2000. - - [RFC2989] Aboba, B., Calhoun, P., Glass, S., Hiller, T., McCann, - P., Shiino, H., Walsh, P., Zorn, G., Dommety, G., - Perkins, C., Patil, B., Mitton, D., Manning, S., - Beadles, M., Chen, X., Sivalingham, S., Hameed, A., - Munson, M., Jacobs, S., Lim, B., Hirschman, B., Hsu, - R., Koo, H., Lipford, M., Campbell, E., Xu, Y., Baba, - S., and E. Jaques, "Criteria for Evaluating AAA - Protocols for Network Access", RFC 2989, November 2000. - - [RFC3162] Aboba, B., Zorn, G., and D. Mitton, "RADIUS and IPv6", - RFC 3162, August 2001. - - [RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and - H. Levkowetz, "Extensible Authentication Protocol - (EAP)", RFC 3748, June 2004. - - [RFC4301] Kent, S. and K. Seo, "Security Architecture for the - Internet Protocol", RFC 4301, December 2005. - - [RFC4690] Klensin, J., Faltstrom, P., Karp, C., and IAB, "Review - and Recommendations for Internationalized Domain Names - (IDNs)", RFC 4690, September 2006. - - [RFC5176] Chiba, M., Dommety, G., Eklund, M., Mitton, D., and B. - Aboba, "Dynamic Authorization Extensions to Remote - Authentication Dial In User Service (RADIUS)", - RFC 5176, January 2008. - - - - -Fajardo, et al. Standards Track [Page 145] - -RFC 6733 Diameter Base Protocol October 2012 - - - [RFC5461] Gont, F., "TCP's Reaction to Soft Errors", RFC 5461, - February 2009. - - [RFC5905] Mills, D., Martin, J., Burbank, J., and W. Kasch, - "Network Time Protocol Version 4: Protocol and - Algorithms Specification", RFC 5905, June 2010. - - [RFC5927] Gont, F., "ICMP Attacks against TCP", RFC 5927, - July 2010. - - [RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and - S. Cheshire, "Internet Assigned Numbers Authority - (IANA) Procedures for the Management of the Service - Name and Transport Protocol Port Number Registry", - BCP 165, RFC 6335, August 2011. - - [RFC6737] Kang, J. and G. Zorn, "The Diameter Capabilities Update - Application", RFC 6737, October 2012. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Fajardo, et al. Standards Track [Page 146] - -RFC 6733 Diameter Base Protocol October 2012 - - -Appendix A. Acknowledgements - -A.1. This Document - - The authors would like to thank the following people that have - provided proposals and contributions to this document: - - To Vishnu Ram and Satendra Gera for their contributions on - capabilities updates, predictive loop avoidance, as well as many - other technical proposals. To Tolga Asveren for his insights and - contributions on almost all of the proposed solutions incorporated - into this document. To Timothy Smith for helping on the capabilities - Update and other topics. To Tony Zhang for providing fixes to - loopholes on composing Failed-AVPs as well as many other issues and - topics. To Jan Nordqvist for clearly stating the usage of - Application Ids. To Anders Kristensen for providing needed technical - opinions. To David Frascone for providing invaluable review of the - document. To Mark Jones for providing clarifying text on vendor - command codes and other vendor-specific indicators. To Victor - Pascual and Sebastien Decugis for new text and recommendations on - SCTP/DTLS. To Jouni Korhonen for taking over the editing task and - resolving last bits from versions 27 through 29. - - Special thanks to the Diameter extensibility design team, which - helped resolve the tricky question of mandatory AVPs and ABNF - semantics. The members of this team are as follows: - - Avi Lior, Jari Arkko, Glen Zorn, Lionel Morand, Mark Jones, Tolga - Asveren, Jouni Korhonen, and Glenn McGregor. - - Special thanks also to people who have provided invaluable comments - and inputs especially in resolving controversial issues: - - Glen Zorn, Yoshihiro Ohba, Marco Stura, Stephen Farrel, Pete Resnick, - Peter Saint-Andre, Robert Sparks, Krishna Prasad, Sean Turner, Barry - Leiba, and Pasi Eronen. - - Finally, we would like to thank the original authors of this - document: - - Pat Calhoun, John Loughney, Jari Arkko, Erik Guttman, and Glen Zorn. - - Their invaluable knowledge and experience has given us a robust and - flexible AAA protocol that many people have seen great value in - adopting. We greatly appreciate their support and stewardship for - the continued improvements of Diameter as a protocol. We would also - like to extend our gratitude to folks aside from the authors who have - - - - -Fajardo, et al. Standards Track [Page 147] - -RFC 6733 Diameter Base Protocol October 2012 - - - assisted and contributed to the original version of this document. - Their efforts significantly contributed to the success of Diameter. - -A.2. RFC 3588 - - The authors would like to thank Nenad Trifunovic, Tony Johansson and - Pankaj Patel for their participation in the pre-IETF Document Reading - Party. Allison Mankin, Jonathan Wood, and Bernard Aboba provided - invaluable assistance in working out transport issues and this was - also the case with Steven Bellovin in the security area. - - Paul Funk and David Mitton were instrumental in getting the Peer - State Machine correct, and our deep thanks go to them for their time. - - Text in this document was also provided by Paul Funk, Mark Eklund, - Mark Jones, and Dave Spence. Jacques Caron provided many great - comments as a result of a thorough review of the spec. - - The authors would also like to acknowledge the following people for - their contribution in the development of the Diameter protocol: - - Allan C. Rubens, Haseeb Akhtar, William Bulley, Stephen Farrell, - David Frascone, Daniel C. Fox, Lol Grant, Ignacio Goyret, Nancy - Greene, Peter Heitman, Fredrik Johansson, Mark Jones, Martin Julien, - Bob Kopacz, Paul Krumviede, Fergal Ladley, Ryan Moats, Victor Muslin, - Kenneth Peirce, John Schnizlein, Sumit Vakil, John R. Vollbrecht, and - Jeff Weisberg. - - Finally, Pat Calhoun would like to thank Sun Microsystems since most - of the effort put into this document was done while he was in their - employ. - -Appendix B. S-NAPTR Example - - As an example, consider a client that wishes to resolve aaa: - ex1.example.com. The client performs a NAPTR query for that domain, - and the following NAPTR records are returned: - - ;; order pref flags service regexp replacement - IN NAPTR 50 50 "s" "aaa:diameter.tls.tcp" "" - _diameter._tls.ex1.example.com - IN NAPTR 100 50 "s" "aaa:diameter.tcp" "" - _aaa._tcp.ex1.example.com - IN NAPTR 150 50 "s" "aaa:diameter.sctp" "" - _diameter._sctp.ex1.example.com - - This indicates that the server supports TLS, TCP, and SCTP in that - order. If the client supports TLS, TLS will be used, targeted to a - - - -Fajardo, et al. Standards Track [Page 148] - -RFC 6733 Diameter Base Protocol October 2012 - - - host determined by an SRV lookup of _diameter._tls.ex1.example.com. - That lookup would return: - - ;; Priority Weight Port Target - IN SRV 0 1 5060 server1.ex1.example.com - IN SRV 0 2 5060 server2.ex1.example.com - - As an alternative example, a client that wishes to resolve aaa: - ex2.example.com. The client performs a NAPTR query for that domain, - and the following NAPTR records are returned: - - ;; order pref flags service regexp replacement - IN NAPTR 150 50 "a" "aaa:diameter.tls.tcp" "" - server1.ex2.example.com - IN NAPTR 150 50 "a" "aaa:diameter.tls.tcp" "" - server2.ex2.example.com - - This indicates that the server supports TCP available at the returned - host names. - -Appendix C. Duplicate Detection - - As described in Section 9.4, accounting record duplicate detection is - based on session identifiers. Duplicates can appear for various - reasons: - - o Failover to an alternate server. Where close to real-time - performance is required, failover thresholds need to be kept low. - This may lead to an increased likelihood of duplicates. Failover - can occur at the client or within Diameter agents. - - o Failure of a client or agent after sending a record from non- - volatile memory, but prior to receipt of an application-layer ACK - and deletion of the record to be sent. This will result in - retransmission of the record soon after the client or agent has - rebooted. - - o Duplicates received from RADIUS gateways. Since the - retransmission behavior of RADIUS is not defined within [RFC2865], - the likelihood of duplication will vary according to the - implementation. - - o Implementation problems and misconfiguration. - - The T flag is used as an indication of an application-layer - retransmission event, e.g., due to failover to an alternate server. - It is defined only for request messages sent by Diameter clients or - agents. For instance, after a reboot, a client may not know whether - - - -Fajardo, et al. Standards Track [Page 149] - -RFC 6733 Diameter Base Protocol October 2012 - - - it has already tried to send the accounting records in its non- - volatile memory before the reboot occurred. Diameter servers MAY use - the T flag as an aid when processing requests and detecting duplicate - messages. However, servers that do this MUST ensure that duplicates - are found even when the first transmitted request arrives at the - server after the retransmitted request. It can be used only in cases - where no answer has been received from the server for a request and - the request is sent again, (e.g., due to a failover to an alternate - peer, due to a recovered primary peer or due to a client re-sending a - stored record from non-volatile memory such as after reboot of a - client or agent). - - In some cases, the Diameter accounting server can delay the duplicate - detection and accounting record processing until a post-processing - phase takes place. At that time records are likely to be sorted - according to the included User-Name and duplicate elimination is easy - in this case. In other situations, it may be necessary to perform - real-time duplicate detection, such as when credit limits are imposed - or real-time fraud detection is desired. - - In general, only generation of duplicates due to failover or re- - sending of records in non-volatile storage can be reliably detected - by Diameter clients or agents. In such cases, the Diameter client or - agents can mark the message as a possible duplicate by setting the T - flag. Since the Diameter server is responsible for duplicate - detection, it can choose whether or not to make use of the T flag, in - order to optimize duplicate detection. Since the T flag does not - affect interoperability, and it may not be needed by some servers, - generation of the T flag is REQUIRED for Diameter clients and agents, - but it MAY be implemented by Diameter servers. - - As an example, it can be usually be assumed that duplicates appear - within a time window of longest recorded network partition or device - fault, perhaps a day. So only records within this time window need - to be looked at in the backward direction. Secondly, hashing - techniques or other schemes, such as the use of the T flag in the - received messages, may be used to eliminate the need to do a full - search even in this set except for rare cases. - - The following is an example of how the T flag may be used by the - server to detect duplicate requests. - - A Diameter server MAY check the T flag of the received message to - determine if the record is a possible duplicate. If the T flag is - set in the request message, the server searches for a duplicate - within a configurable duplication time window backward and - forward. This limits database searching to those records where - the T flag is set. In a well-run network, network partitions and - - - -Fajardo, et al. Standards Track [Page 150] - -RFC 6733 Diameter Base Protocol October 2012 - - - device faults will presumably be rare events, so this approach - represents a substantial optimization of the duplicate detection - process. During failover, it is possible for the original record - to be received after the T-flag-marked record, due to differences - in network delays experienced along the path by the original and - duplicate transmissions. The likelihood of this occurring - increases as the failover interval is decreased. In order to be - able to detect duplicates that are out of order, the Diameter - server should use backward and forward time windows when - performing duplicate checking for the T-flag-marked request. For - example, in order to allow time for the original record to exit - the network and be recorded by the accounting server, the Diameter - server can delay processing records with the T flag set until a - time period TIME_WAIT + RECORD_PROCESSING_TIME has elapsed after - the closing of the original transport connection. After this time - period, it may check the T-flag-marked records against the - database with relative assurance that the original records, if - sent, have been received and recorded. - -Appendix D. Internationalized Domain Names - - To be compatible with the existing DNS infrastructure and simplify - host and domain name comparison, Diameter identities (FQDNs) are - represented in ASCII form. This allows the Diameter protocol to fall - in-line with the DNS strategy of being transparent from the effects - of Internationalized Domain Names (IDNs) by following the - recommendations in [RFC4690] and [RFC5890]. Applications that - provide support for IDNs outside of the Diameter protocol but - interacting with it SHOULD use the representation and conversion - framework described in [RFC5890], [RFC5891], and [RFC3492]. -</pre> - -</section> |