AAA Working Group Pat R. Calhoun Internet-Draft Black Storm Networks Category: Standards Track Haseeb Akhtar <draft-ietf-aaa-diameter-08.txt> Nortel Networks Jari Arkko Oy LM Ericsson Ab Erik Guttman Sun Microsystems, Inc. Allan C. Rubens Tut Systems, Inc. Glen Zorn Cisco Systems, Inc. November 2001 Diameter Base Protocol Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at: http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at: http://www.ietf.org/shadow.html. Distribution of this memo is unlimited. Copyright (C) The Internet Society 2001. All Rights Reserved. Calhoun et al. expires May 2002 [Page 1]
Internet-Draft November 2001 Abstract The Diameter base protocol is intended to provide a AAA framework for Mobile-IP, NASREQ and ROAMOPS. This draft specifies the message format, transport, error reporting and security services to be used by all Diameter applications and MUST be supported by all Diameter implementations. Table of Contents 1.0 Introduction 1.1 Diameter Protocol 1.2 Requirements language 1.3 Terminology 2.0 Protocol Overview 2.1 Transport 2.1.1 SCTP Guidelines 2.2 Securing Diameter Messages 2.3 Diameter Protocol Extensibility 2.3.1 Defining new AVP Values 2.3.2 Creating new AVPs 2.3.3 Creating a new Auth Applications 2.3.4 Creating a new Accounting Application 2.3.5 Application authentication procedures 2.4 Diameter Application Compliance 2.5 Application Identifiers 2.7 Peer Table 2.8 Realm-Based Routing Table 2.9 Role of Diameter Agents 2.9.1 Relay Agents 2.9.2 Proxy Agents 2.9.3 Redirect Agents 2.9.4 Translation Agents 3.0 Diameter Header 3.1 Command Code Definitions 3.2 Command Code ABNF specification 3.3 Diameter Command Naming Conventions 4.0 Diameter AVPs 4.1 AVP Header 4.2 Optional Header Elements 4.3 AVP Data Formats 4.4 Derived AVP Data Formats 4.5 Grouped AVP Values 4.5.1 Example AVP with a Grouped Data type 4.6 Diameter Base Protocol AVPs 5.0 Diameter Peers 5.1 Connecting to Peers Calhoun et al. expires May 2002 [Page 2]
Internet-Draft November 2001 5.2 Diameter Peer Discovery 5.3 Capabilities Negotiation 5.3.1 Capabilities-Exchange-Request 5.3.2 Capabilities-Exchange-Answer 5.3.3 Vendor-Id AVP 5.3.4 Firmware-Revision AVP 5.3.5 Host-IP-Address AVP 5.3.6 Supported-Vendor-Id AVP 5.3.7 Product-Name AVP 5.4 Disconnecting Peer connections 5.4.1 Disconnect-Peer-Request 5.4.2 Disconnect-Peer-Answer 5.4.3 Disconnect-Cause AVP 5.5 Transport Failure Detection 5.5.1 Device-Watchdog-Request 5.5.2 Device-Watchdog-Answer 5.5.3 Transport Failure Algorithm 5.5.4 Failover/Failback Procedures 5.6 Peer State Machine 5.6.1 Incoming connections 5.6.2 Events 5.6.3 Actions 5.6.4 The Election Process 6.0 Diameter message processing 6.1 Diameter request routing overview 6.1.1 Originating a Request 6.1.2 Sending a Request 6.1.3 Receiving Requests 6.1.4 Processing Local Requests 6.1.5 Request Forwarding 6.1.6 Request Routing 6.1.7 Redirecting requests 6.1.8 Relaying and Proxying Requests 6.2 Diameter Answer Processing 6.2.1 Processing received Answers 6.2.2 Relaying and Proxying Answers 6.3 Origin-Host AVP 6.4 Origin-Realm AVP 6.5 Destination-Host AVP 6.6 Destination-Realm AVP 6.7 Routing AVPs 6.7.1 Route-Record AVP 6.7.2 Proxy-Info AVP 6.7.3 Proxy-Host AVP 6.7.4 Proxy-State AVP 6.8 Auth-Application-Id AVP 6.9 Acct-Application-Id AVP 6.10 Vendor-Specific-Application-Id AVP Calhoun et al. expires May 2002 [Page 3]
Internet-Draft November 2001 6.11 Redirect-Host AVP 6.12 Redirect-Host-Usage AVP 6.13 Redirect-Max-Cache-Time AVP 7.0 Error Handling 7.1 Result-Code AVP 7.1.1 Informational 7.1.2 Success 7.1.3 Protocol Errors 7.1.4 Transient Failures 7.1.5 Permanent Failures 7.2 Error Bit 7.3 Error-Message AVP 7.4 Error-Reporting-Host AVP 7.5 Failed-AVP AVP 8.0 Diameter User Sessions 8.1 Authorization Session State Machine 8.2 Accounting Session State Machine 8.3 Server-Initiated Re-Auth 8.3.1 Re-Auth-Request 8.3.2 Re-Auth-Answer 8.4 Session Termination 8.4.1 Session-Termination-Request 8.4.2 Session-Termination-Answer 8.5 Aborting a Session 8.5.1 Abort-Session-Request 8.5.2 Abort-Session-Answer 8.6 Inferring Session Termination from Origin-State-Id 8.7 Auth-Request-Type AVP 8.8 Session-Id AVP 8.9 Authorization-Lifetime AVP 8.10 Auth-Grace-Period AVP 8.11 Auth-Session-State AVP 8.12 Re-Auth-Request-Type AVP 8.13 Session-Timeout AVP 8.14 User-Name AVP 8.15 Termination-Cause AVP 8.16 Origin-State-Id AVP 8.17 Session-Binding AVP 8.18 Session-Server-Failover AVP 8.19 Multi-Round-Time-Out AVP 8.20 Class AVP 9.0 Accounting 9.1 Server Directed Model 9.2 Protocol Messages 9.3 Application document requirements 9.4 Fault Resilience 9.5 Accounting Records 9.6 Correlation of Accounting Records Calhoun et al. expires May 2002 [Page 4]
Internet-Draft November 2001 9.7 Accounting Command-Codes 9.7.1 Accounting-Request 9.7.2 Accounting-Answer 9.8 Accounting AVPs 9.8.1 Accounting-Record-Type AVP 9.8.2 Accounting-Interim-Interval AVP 9.8.3 Accounting-Record-Number AVP 9.8.4 Accounting-RADIUS-Session-Id AVP 9.8.5 Accounting-Multi-Session-Id AVP 9.8.6 Accounting-Sub-Session-Id AVP 10.0 AVP Occurrence Table 10.1 Base Protocol Command AVP Table 10.2 Accounting AVP Table 11.0 IANA Considerations 11.1 AVP Header 11.1.1 AVP Code 11.1.2 AVP Flags 11.2 Diameter Header 11.2.1 Command Codes 11.2.2 Message Flags 11.3 Application Identifier Values 11.4 Result-Code AVP Values 11.5 Accounting-Record-Type AVP Values 11.6 Termination-Cause AVP Values 11.7 Redirect-Host-Usage AVP Values 11.8 Session-Server-Failover AVP Values 11.9 Session-Binding AVP Values 11.10 Diameter TCP/SCTP Port Numbers 11.11 Disconnect-Cause AVP Values 11.12 Auth-Request-Type AVP Values 11.13 Auth-Session-State AVP Values 11.14 Re-Auth-Request-Type AVP Values 12.0 Diameter protocol related configurable parameters 13.0 Security Considerations 14.0 References 15.0 Acknowledgements 16.0 Authors' Addresses 17.0 Full Copyright Statement 18.0 Expiration Date Appendix A. Diameter Service Template Calhoun et al. expires May 2002 [Page 5]
Internet-Draft November 2001 1.0 Introduction Historically, the RADIUS protocol has been used to provide AAA services for dial-up PPP [42] and terminal server access. Over time, routers and network access servers (NAS) have increased in complexity and density, making the RADIUS protocol increasingly unsuitable for use in such networks. The Roaming Operations Working Group (ROAMOPS) has published a set of specifications [20, 43, 44] that define how a PPP user can gain access to the Internet without having to dial into his/her home service provider's modem pool. This is achieved by allowing service providers to cross-authenticate their users. Effectively, a user can dial into any service provider's point of presence (POP) that has a roaming agreement with his/her home Internet service provider (ISP), the benefit being that the user does not have to incur a long distance charge while traveling, which can sometimes be quite expensive. Given the number of ISPs today, ROAMOPS realized that requiring each ISP to set up roaming agreements with all other ISPs did not scale. Therefore, the working group defined a "broker", which acts as an intermediate server, whose sole purpose is to set up these roaming agreements. A collection of ISPs and a broker is called a "roaming consortium". There are many such brokers in existence today; many also provide settlement services for member ISPs. The Mobile-IP Working Group has recently changed its focus to inter administrative domain mobility, which is a requirement for cellular carriers wishing to deploy IETF-based mobility protocols. The current cellular carriers requirements [22, 23] are very similar to the ROAMOPS model, with the exception that the access protocol is Mobile- IP [45] instead of PPP. The Diameter protocol was not designed from the ground up. Instead, the basic RADIUS model was retained while fixing the flaws in the RADIUS protocol itself. Diameter does not share a common protocol data unit (PDU) with RADIUS, but does borrow sufficiently from the protocol to ease migration. The basic concept behind Diameter is to provide a base protocol that can be extended in order to provide AAA services to new access technologies. Currently, the protocol only concerns itself with Internet access, both in the traditional PPP sense as well as taking into account the ROAMOPS model, and Mobile-IP. Although Diameter could be used to solve a wider set of AAA problems, we are currently limiting the scope of the protocol in order to Calhoun et al. expires May 2002 [Page 6]
Internet-Draft November 2001 ensure that the effort remains focused on satisfying the requirements of network access. Note that 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. 1.1 Diameter Protocol The Diameter protocol allows peers to exchange a variety of messages. The base protocol provides the following facilities: - Delivery of AVPs (attribute value pairs) - Capabilities negotiation, as required in [20] - Error notification - Extensibility, through addition of new commands and AVPs, as required in [21] All data delivered by the protocol is in the form of an AVP. Some of these AVP values are used by the Diameter protocol itself, while others deliver data associated with particular applications which employ Diameter. AVPs may be added arbitrarily to Diameter messages, so long as the required AVPs are included and AVPs which are explicitly excluded are not included. AVPs are used by base Diameter protocol to support the following required features: - Transporting of user authentication information, for the purposes of enabling the Diameter server to authenticate the user. - Transporting of service specific authorization information, between client and servers, allowing the peers to decide whether a user's access request should be granted. - Exchanging resource usage information, which MAY be used for accounting purposes, capacity planning, etc. - Relaying, proxying and redirecting of Diameter messages through a server hierarchy. The Diameter base protocol provides the minimum requirements needed for an AAA transport protocol, as required by NASREQ [21], Mobile IP [22, 23], and ROAMOPS [20]. The base protocol is not intended to be used by itself, and must be used with a Diameter application, such as Mobile IP [10]. The Diameter protocol was heavily inspired and builds upon the tradition of the RADIUS [1] protocol. See section 2.4. for more information on Diameter applications. Any node can initiate a request. In that sense, Diameter is a peer to peer protocol. In this document, a Diameter client is an access device that initiates a request for authentication and/or Calhoun et al. expires May 2002 [Page 7]
Internet-Draft November 2001 authorization of a given user. A Diameter agent is a node that does not authenticate and/or authorize messages locally, such as proxies and relay agents. A Diameter server is one that performs authentication and/or authorization of the user based on some profile. A Diameter node MAY act as an agent for certain requests while act as a server for others. The Diameter protocol also supports server initiated messages towards access devices, such as a request to abort service to a particular user. 1.2 Requirements language In this document, the key words "MAY", "MUST", "MUST NOT", "optional", "recommended", "SHOULD", and "SHOULD NOT", are to be interpreted as described in [13]. 1.3 Terminology Accounting The act of collecting information on resource usage for the purpose of trend analysis, auditing, billing, or cost allocation. Accounting record A session record represents a summary of the resource consumption of a user over the entire session. Accounting gateways creating the session record may do so by processing interim accounting events or accounting events from several devices serving the same user. Authentication The act of verifying the identity of an entity (subject). Authorization The act of determining whether a requesting entity (subject) will be allowed access to a resource (object). AVP The Diameter protocol consists of a header followed by one or more Attribute-Value-Pair (AVP). The AVP includes a header and is used to encapsulation protocol-specific data (e.g. routing information) as well as authentication, authorization or accounting information. Broker A broker is a business term commonly used in AAA infrastructures. Calhoun et al. expires May 2002 [Page 8]
Internet-Draft November 2001 A broker is either a relay, proxy or redirect agent, and MAY be operated by roaming consortiums. Diameter Agent A Diameter Agent is a host that is providing either relay, proxy, redirect or translation services. Diameter Client A Diameter Client is a device at the edge of the network that performs access control. An example of a Diameter client is a Network Access Server (NAS) or a Foreign Agent (FA). Diameter Node A Diameter node is a host that implements the Diameter protocol, and acts either as a Client, Agent or Server. Diameter Server A Diameter Server is one that handles authentication, authorization and accounting requests for a particular realm. By its very nature, a Diameter Server MUST support Diameter applications in addition to the base protocol. Downstream Downstream is used to identify the direction of a particular Diameter message from the home server towards the access device. Home Realm A Home Realm is the administrative domain with whom the user maintains an account relationship. Home Server See Diameter Server. Interim accounting An interim accounting message provides a snapshot of usage during a user's session. It is typically implemented in order to provide for partial accounting of a user's session in the event of a device reboot or other network problem that prevents the reception of a session summary message or session record. Local Realm A local realm is the administrative domain providing services to a user. An administrative domain MAY act as a local realm for certain users, while being a home realm for others. Multi-session A multi-session represents a logical linking of several sessions. Calhoun et al. expires May 2002 [Page 9]
Internet-Draft November 2001 Multi-sessions are tracked by using the Accounting-Multi-Session- Id. An example of a multi-session would be a MLP 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 [8], 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 In addition to forwarding requests and responses, proxies enforce policies relating to resource usage and provisioning. This is typically accomplished by tracking the state of NAS devices. While proxies typically do not respond to client Requests prior to receiving a Response from the server, they may originate Reject messages in cases where policies are violated. As a result, proxies need to understand the semantics of the messages passing through them, and may not support all Diameter applications. Realm The string in the NAI that immediately follows the '@' character. NAI realm names are required to be unique, and are piggybacked on the administration of the DNS namespace. Diameter makes use of the realm, also loosely referred to as domain, to determine whether messages can be satisfied locally, or whether they must be proxied. Real-time Accounting Real-time accounting involves the processing of information on resource usage within a defined time window. Time constraints are typically imposed in order to limit financial risk. Relay Relays forward requests and responses based on routing-related AVPs and realm forwarding table entries. Since relays do not enforce policies, 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 applications 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 conversations in progress. Redirect Agent Calhoun et al. expires May 2002 [Page 10]
Internet-Draft November 2001 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 transitting 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 Routing or Policy proxies for other types. As with Routing proxies, redirect agents do not keep state with respect to conversations or NAS resources. Roaming Relationships Roaming relationships include relationships between companies and ISPs, relationships among peer ISPs within a roaming association, and relationships between an ISP and a roaming consortia. Together, the set of relationships forming a path between a local ISP's authentication proxy and the home authentication server is known as the roaming relationship path. Session A session is a related progression of events devoted to a particular activity. Each application SHOULD provide guidelines as to when a session begins and ends. All Diameter packets with the same Session-Identifier are considered to be part of the same session. 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. An example of a session divided into several sub-sessions would be a dial-up connection in which the pre-authentication activity (call setup, resource allocation, etc.), interactive login, and PPP communication would all be sub-sessions. Translation Agent A translation agent is a stateful Diameter node that performs protocol translation between Diameter and another AAA protocol. Upstream Upstream is used to identify the direction of a particular Diameter message from the access device towards the home server. 2.0 Protocol Overview Calhoun et al. expires May 2002 [Page 11]
Internet-Draft November 2001 The base Diameter protocol is never used on its own. It is always extended for a particular application. Three Diameter applications are defined by companion documents: NASREQ [7], Mobile IP [10], CMS Security [11]. These options are introduced in this document but specified elsewhere. Additional Diameter applications MAY be defined in the future (see Section 11.3). Diameter Clients MUST support the base protocol, which includes accounting. In addition, they MUST fully support each Diameter application which is needed to implement the client's service, e.g. NASREQ and/or Mobile IP. A Diameter Client which does not support both NASREQ and Mobile IP, MUST be referred to as "Diameter X Client" where X is the application which it supports, and not a "Diameter Client." Diameter Servers must support the base protocol, which includes accounting. In addition, they MUST fully support each Diameter application which is needed to implement the intended service, e.g. NASREQ and/or Mobile IP. A Diameter Server which does not support both NASREQ and Mobile IP, MUST be referred to as "Diameter X Server" where X is the application which it supports, and not a "Diameter Server." Diameter Relays and Redirect agents are, by definition, protocol transparent, and MUST transparently support the Diameter base protocol, which includes accounting, and all Diameter applications. Diameter Proxies MUST support the base protocol, which includes accounting. In addition, they MUST fully support each Diameter application which is needed to implement proxied services, e.g. NASREQ and/or Mobile IP. A Diameter Proxy which does not support also both NASREQ and Mobile IP, MUST be referred to as "Diameter X Proxy" where X is the application which it supports, and not a "Diameter Proxy." The Diameter CMS security application [11] contains two features: 1. A set of messages that allows a Diameter node to establish a security association, which is used to secure AVPs within a Diameter message, even though the message may traverse intermediate Diameter agents. A set of AVPs are also defined to sign and encrypt AVPs, as well as to transport certificates. This feature MUST be supported by Diameter server and proxy agents, SHOULD be supported by Diameter clients, and MAY be supported by relay and redirect agents. 2. A set of messages, known as PDSR and PDSA, allows a Diameter client to request that an agent establish a Diameter security association with a server in a specific realm. This feature MUST be supported by Diameter clients and Proxy agents, and MAY Calhoun et al. expires May 2002 [Page 12]
Internet-Draft November 2001 be supported by Diameter servers, relay and redirect agents. The base Diameter protocol concerns itself with capabilities negotiation, how messages are sent and how peers may eventually be abandoned. The base protocol also defines certain rules which apply to all exchanges of messages between Diameter nodes. Communication between Diameter peers begins with one peer sending a message to another Diameter peer. The set of AVPs included in the message is determined by a particular Diameter application. One AVP that is included to reference a user's session is the Session-Id. The initial request for authentication and/or authorization of a user would include the Session-Id. The Session-Id is then used in all subsequent messages to identify the user's session (see section 8.0 for more information). The communicating party may accept the request, or reject it by returning an answer message with Result-Code AVP set to indicate an error occurred. The specific behavior of the diameter server or client receiving a request depends on the Diameter application employed. Session state (associated with a Session-Id) MUST be freed upon receipt of the Session-Termination-Request, Session-Termination- Answer, expiration of authorized service time in the Session-Timeout AVP, and according to rules established in a particular Diameter application. 2.1 Transport The base Diameter protocol is run on port TBD of both TCP [27] and SCTP [26] transport protocols (for interoperability test purposes port 1812 will be used until IANA assigns a port to the protocol). When used with TLS [38], The Diameter protocol is run on port TBD of both TCP and SCTP. Diameter clients MUST support either TCP or SCTP, while agents and servers MUST support both. Future versions of this specification MAY mandate that clients support SCTP. A Diameter node MAY initiate connections from any source port, other than the one which they declare they accept incoming connections on, and MUST be prepared to receive connections on port TBD. A given Diameter process MUST NOT use more than one transport connection to communicate with a given peer, unless multiple processes exist on the peer in which case a separate connection per process is allowed. When no transport connection exists with a peer, an attempt to Calhoun et al. expires May 2002 [Page 13]
Internet-Draft November 2001 connect SHOULD be periodically attempted. This behavior is handled via the Tc timer, whose recommended value is 30 seconds. There are certain exceptions to this rule, such as when a peer has terminated the transport connection stating that it does not wish to communicate. When connecting to a peer, and either zero or more transports are specified, SCTP SHOULD be tried first, followed by TCP. See section 5.2 for more information on peer discovery. Diameter implementations SHOULD be able to interpret ICMP protocol and port unreachable messages as explicit indications that the server is not reachable, in addition to interpreting ECONNREFUSED (a reset from the transport) and timed-out connection attempts. If Diameter receives data up from TCP that cannot be parsed or identified as a Diameter error made by the peer, the stream is compromised and cannot be recovered. The transport connection MUST be closed using a RESET call (graceful closure is also compromised). 2.1.1 SCTP Guidelines The following are guidelines for Diameter implementations that support SCTP: 1. For interoperability: All Diameter nodes MUST be prepared to receive Diameter messages on any SCTP stream in the association. 2. To prevent blocking: All Diameter nodes SHOULD utilize all SCTP streams available to the association to prevent head-of-the- line blocking. 2.2 Securing Diameter Messages Diameter clients, such as Network Access Servers (NASes) and Mobility Agents MUST support IP Security [37], and MAY support TLS [38]. Diameter servers MUST support TLS and IPSec. Operating the Diameter protocol without any security mechanism is not recommended. 2.3 Diameter Protocol Extensibility There are various ways the Diameter protocol can be extended. This section is intended to assist protocol designers in selecting the best method of using the Diameter protocol. Calhoun et al. expires May 2002 [Page 14]
Internet-Draft November 2001 2.3.1 Defining new AVP Values New applications should attempt to reuse AVPs defined in existing application when possible, as opposed to creating a new AVP. For AVPs of type Enumerated, it is possible the application requires a new value to communicate some service-specific information. In order to allocate a new AVP value, a request MUST be sent to IANA [47], with a detailed explanation of the value. If the new AVP value changes an existing command code's ABNF, the IANA AVP value request MUST include the new ABNF itself. 2.3.2 Creating new AVPs When no existing AVP can be used appropriately to communicate some service-specific information, a new AVP should be created. The new AVP being defined MUST follow one of the types listed in section 4.3. In the event that a logical grouping of AVPs is necessary, and multiple "groups" are possible in a given command, it is highly recommended that a Grouped AVP be used (see Section 4.5). In order to create a new AVP, a request MUST be sent to IANA, with a detailed explanation of the AVP, its type and possible values. Furthermore, the request MUST include the commands that would make use of the AVP. 2.3.3 Creating new Auth Applications Should a new application require Diameter support, but it cannot fit within an existing application without requiring major changes to the specification, it may be desirable to create a new Diameter application. Major changes to an application include: - Requiring a whole different set of mandatory AVPs to a command - Requiring a command that has a different number of round trips to satisfy a request (e.g. application foo has a command that requires one round trip, but new application bar has a command that requires two round trips to complete). - The method used to authenticate the user is drastically different from any existing application, and the authentication information cannot be carried within the AVPs defined in the application. Note that the creation of a new application should be viewed as a last resort. New Diameter applications MUST define at least one Command Code, the Calhoun et al. expires May 2002 [Page 15]
Internet-Draft November 2001 expected AVPs in an ABNF [31] grammar (see section 3.2), and MAY also define new AVPs. If the Diameter application has any accounting requirements, it MUST also specify the AVPs that are to be present in the Diameter Accounting messages (see section 9.3). When possible, a new Diameter application SHOULD attempt to re-use any existing Diameter AVP, in order to reduce the possibility of having multiple AVPs that carry similar information. Every Diameter application specification MUST have an IANA assigned Application Identifier (see section 2.4). 2.3.4 Creating a new Accounting Application There are services that only require the use of Diameter accounting. Since such services need to define the service specific AVPs that must be carried in the Accounting-Request/Answer messages, but do not need to define command codes, the rules on allocation of Accounting Application Identifiers is different from the ones defined in section 2.3.3. When possible, a new Diameter accounting application SHOULD attempt to re-use any existing Diameter AVP, in order to reduce the possibility of having multiple AVPs that carry similar information. Every Diameter accounting application specification MUST have an IANA assigned Application Identifier (see section 2.4). 2.3.5 Application authentication procedures When possible, applications SHOULD be designed such that new authentication methods MAY be added without requiring changes to the application. This MAY require that new AVP values be assigned to represent the new authentication transform, or any other scheme that produces similar results. When possible, authentication frameworks, such as Extensible Authentication Protocol [25], SHOULD be used. 2.4 Diameter Application Compliance Application Identifiers are advertised during the capabilities exchange phase (see section 2.5). For a given application, there are two different ways of advertising support. First, advertising support of the application via the Auth-Application-Id implies that the sender supports all authentication and authorization command codes, and the AVPs specified in the associated ABNFs, described in the Calhoun et al. expires May 2002 [Page 16]
Internet-Draft November 2001 specification. Second, advertising support of the application via the Acct-Application-Id implies that the sender supports the Accounting command codes defined in this specification, as well as the accounting AVPs defined in the application's specification. An implementation MAY add arbitrary AVPs to any command defined in an application, including vendor-specific AVPs. However, implementations that add such AVPs with the Mandatory 'M' bit set are not compliant, and are at fault if the peer rejects the request. If the sender of such a message wishes to provide service, it MUST resend the message with the offending AVPs removed. 2.5 Application Identifiers Each Diameter application MUST have an IANA assigned Application Identifier (see section 11.3). The base protocol does not require an application Identifier since its support is mandatory. During the capabilities exchange, Diameter nodes inform their peers of locally supported applications. Furthermore, all Diameter messages contain an application identifier, which is used in the message forwarding process. The following Application Identifier values are defined: NASREQ 1 [7] CMS Security 2 [11] Mobile-IP 4 [10] Relay 0xffffffff Relay and redirect agents MUST advertise the Relay application identifier, while all other Diameter nodes MUST advertise locally supported applications. The receiver of a Capabilities Exchange message advertising Relay service MUST assume that the sender supports all current and future applications. Diameter relay and proxy agents are responsible for finding an upstream server that supports the application of a particular message. If none can be found, an error message is returned with the Result-Code AVP set to DIAMETER_UNABLE_TO_DELIVER. 2.6 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. Calhoun et al. expires May 2002 [Page 17]
Internet-Draft November 2001 A connection is a transport level connection between two peers, used to send and receive Diameter messages. A session is a logical concept at the application layer, and is shared between an access device and a server, and is identified via the Session-Id AVP +--------+ +-------+ +--------+ | Client | | Relay | | Server | +--------+ +-------+ +--------+ <----------> <----------> peer connection A peer connection B <-----------------------------> User session x Figure 1: Diameter connections and sessions In the example provided in figure 1, peer connection A is established between the Client and its local Relay. Peer connection B is established between the Relay and the Server. User session x spans from the Client via the Relay to the Server. Each "user" of a service causes an auth request to be sent, with a unique session identifier. Once accepted by the server, both the client and the server are aware of the session. It is important to note that there is no relationship between a connection and a session, and that Diameter messages for multiple sessions are all multiplexed through a single connection. 2.7 Peer Table The Diameter Peer Table is used in message forwarding, and referenced by the Realm Routing Table. A Peer Table entry contains the following fields: - Host identity. following the conventions described for the DiameterIdentity derived AVP data format in section 4.4. This field contains the contents of the Origin-Host AVP found in the CER or CEA message. - Status. This is the state of the peer entry, and MUST match one of the values listed in section 5.6. - Role. This field specifies whether a peer is a primary, secondary or alternate. - Static or Dynamic. Specifies whether a peer entry was statically configured, or dynamically discovered. - Expiration time. Specifies the time which dynamically discovered peer table entries are to be either refreshed, or expired. - TLS Enabled. Specifies whether TLS is to be used when communicating with the peer. - Additional security information, when needed (e.g. keys, certificates) Calhoun et al. expires May 2002 [Page 18]
Internet-Draft November 2001 2.8 Realm-Based Routing Table All Realm-Based routing lookups are performed against what is commonly known as the Realm Routing Table (see section 12.0). A Realm Routing Table Entry contains the following fields: - Realm Name. This is the field that is typically used as a primary key in the routing table lookups. Note that some implementations perform their lookups based on longest-match- from-the-right on the realm rather than requiring an exact match. - Application Identifier. It is possible for a route entry to have a different destination based on the Acct-Application-Id (for accounting messages) or Auth-Application-Id (for non-accounting messages) of the message. This field is typically used as a secondary key field in routing table lookups. - Local Action. The Local Action field is used to identify how a message should be treated. The following actions are supported: 1. LOCAL - Diameter messages that resolve to a route entry with the Local Action set to Local can be satisfied locally, and do not need to be routed to another server. 2. RELAY - All Diameter messages that fall within this category MUST be routed to a next hop server, without modifying any non-routing AVPs. See section 6.1.8 for relaying guidelines 3. PROXY - All Diameter messages that fall within this category MUST be routed to a next hop server. The local server MAY apply its local policies to the message by including new AVPs to the message prior to routing. See section 6.1.8 for proxying guidelines. 4. REDIRECT - Diameter messages that fall within this category MUST have the identity of the home Diameter server(s) appended, and returned to the sender of the message. See section 6.1.7 for redirect guidelines. - Server Identifier. One or more servers the message is to be routed to. These servers MUST also be present in the Peer table. When the Local Action is set to RELAY or PROXY, this field contains the identity of the server(s) the message must be routed to. When the Local Action field is set to REDIRECT, this field contains the identity of one or more servers the message should be redirected to. - Static or Dynamic. Specifies whether a route entry was statically configured, or dynamically discovered. - Expiration time. Specifies the time which a dynamically discovered route table entry expires. It is important to note that Diameter agents MUST support at least one of the LOCAL, RELAY, PROXY or REDIRECT modes of operation. Agents do not need to support all modes of operation in order to conform Calhoun et al. expires May 2002 [Page 19]
Internet-Draft November 2001 with the protocol specification, but MUST follow the protocol compliance guidelines in section 2.0. Relay agents MUST NOT reorder AVPs, and proxies MUST NOT reorder AVPs. The routing table MAY include a default entry which MUST be used for any requests not matching any of the other entries. The routing table MAY consist of only such an entry. When a request is routed, the target server MUST have advertised the Application Identifier (see section 2.5) for the given message, or have advertised itself as a relay or proxy agent. Oherwise an error is returned with the Result-Code AVP set to DIAMETER_UNABLE_TO_DELIVER. 2.9 Role of Diameter Agents In addition to client and servers, the Diameter protocol introduces relay, proxy and redirect agents, each of which is defined in Section 1.3. These Diameter agents are useful for several reasons: - They can distribute administration of systems to a configurable grouping, including the maintenance of security associations. - They can be used for concentration of requests from an number of co-located or distributed NAS equipment sets to a set of like user groups. - They can do value-added processing to the requests or responses. - They can be used for load balancing. - A complex network will have multiple authentication sources, they can sort requests and forward towards the correct target. The Diameter protocol requires that agents maintain transaction state, which is used for failover purposes. Transaction state implies that upon forwarding a request, it's Hop-by-Hop identifier is saved, the field is replaced with a locally unique identifier, which is restored to its original value when the corresponding answer is received. The request's state is released upon receipt of the answer. A stateless agent is one that only maintains transaction state. The Proxy-Info AVP allows stateless agents to add local state to a Diameter request, with the guarantee that the same state will be present in the answer. However, the protocol's failover procedures require that agents maintain a copy of pending requests. A stateful agent is one that maintains session state information, by keeping track of all authorized active sessions. Each authorized session is bound to a particular service, and its state is considered active either until it is notified otherwise, or by expiration. Each authorized session has a expiration, which is communicated by Calhoun et al. expires May 2002 [Page 20]
Internet-Draft November 2001 Diameter servers via the Session-Timeout AVP. Maintaining session state MAY be useful in certain applications, such as: - Protocol translation (e.g. RADIUS <-> Diameter) - Limiting resources authorized to a particular user - Per user or transaction auditing A Diameter agent MAY act in a stateful manner for some requests, while be stateless for others. A Diameter implementation MAY act as one type of agent for some requests, and as another type of agent for others. 2.9.1 Relay Agents Relay Agents are Diameter agents that accept requests and route messages to other Diameter agents based on information found in the messages (e.g. Destination-Realm). This routing decision is performed using a list of supported realms, and known peers. This is known as the Diameter Routing Table, as is defined further in section 2.8. Relays MAY be used to aggregate requests from multiple Network Access Servers (NASes) within a common geographical area (POP). The use of Relays is advantageous since it eliminates the need for NASes to be configured with the necessary security information they would otherwise require to communicate with Diameter servers in other realms. Likewise, this reduces the configuration load on Diameter servers that would otherwise be necessary when NASes are added, changed or deleted. Relays modify Diameter messages by inserting, and removing, routing information, but do not modify any other portion of a message. Further, Relays inherent simplicity implies that they are stateless, and therefore SHOULD NOT maintain session state, but MUST maintain transaction state. +------+ ---------> +------+ ---------> +------+ | | 1. Request | | 2. Request | | | NAS | | DRL | | HMS | | | 4. Answer | | 3. Answer | | +------+ <--------- +------+ <--------- +------+ mno.net mno.net abc.com Figure 2: Relaying of Diameter messages The example provided in Figure 2 depicts a request issued from NAS, which is an access device, for the user bob@abc.com. Prior to issuing the request, NAS performs a Diameter route lookup, using "abc.com" as Calhoun et al. expires May 2002 [Page 21]
Internet-Draft November 2001 the key, and determines that the message is to be relayed to DRL, which is a Diameter Relay. DRL performs the same route lookup as NAS, and relays the message to HMS, which is abc.com's Home Diameter Server. HMS identifies that the request can be locally supported (via the realm), processes the authentication and/or authorization request, and replies with an answer, which is routed back to NAS using saved transaction state. Since Relays do not perform any application level processing, they provide relaying services for all Diameter applications, and therefore MUST advertise the Relay Application Identifier. 2.9.2 Proxy Agents Similarly to Relays, Proxy agents route Diameter messages using the Diameter Routing Table. However, they differ since they modify messages to implement policy enforcement. This requires that proxies maintain the state of their downstream peers (e.g. access devices) to enforce resource usage, provide admission control, and provisioning. It is important to note that although proxies MAY provide a value-add function for NASes, they do not allow access devices to use the Diameter CMS Security application, since modifying messages breaks authentication. Proxies MAY be used in call control centers or access ISPs that provide outsourced connections, they can monitor the number and types of ports in use, and make allocation and admission decisions according to their configuration. Proxies that wish to limit resources MUST be stateful, and all Proxies MUST maintain transaction state. Proxy agents MUST NOT allow CMS security to be established between two peers if it expects to modify ANY non-routing AVP in messages exchanged between the peers. See [11] for more information. Since enforcing policies requires an understanding of the service being provided, Proxies MUST only advertise the Diameter applications they support. 2.9.3 Redirect Agents Redirect agents provide Realm to Server address resolution, and use the Diameter routing table to determine where a given request should be forwarded. When a request is received by a redirect agent, a Calhoun et al. expires May 2002 [Page 22]
Internet-Draft November 2001 special answer is created, which includes the identity of the Diameter server(s) the originator of the request should contact directly. Redirect agents are useful in scenarios where the Diameter routing configuration needs to be centralized. An example is a redirect agent that provides services to all members of a consortium, but does not wish to be burdened with relaying all messages between realms. This scenario is advantageous since it does not require that the consortium provide routing updates to its members when changes are made to a member's infrastructure. Since redirect agents do not relay messages, and only return an answer with the information necessary for Diameter agents to communicate directly, they do not modify messages. Since redirect agents do not receive answer messages, they cannot maintain session state. Further, since redirect agents never relay requests, they are not required to maintain transaction state. The example provided in Figure 3 depicts a request issued from the access device, NAS, for the user bob@abc.com. The message is forwarded by the NAS to its relay, DRL, which does not have a routing entry in its Diameter Routing Table for abc.com. DRL has a default route configured to DRD, which is a redirect agent that returns a redirect notification to DRL, as well as HMS' contact information. Upon receipt of the redirect notification, DRL establishes a transport connection with HMS, if one doesn't already exist, and forwards the request to it. +------+ | | | DRD | | | +------+ ^ | 2. Request | | 3. Redirection | | Notification | v +------+ ---------> +------+ ---------> +------+ | | 1. Request | | 4. Request | | | NAS | | DRL | | HMS | | | 6. Answer | | 5. Answer | | +------+ <--------- +------+ <--------- +------+ mno.net mno.net abc.com Figure 3: Redirecting a Diameter Message Since Redirect agents do not perform any application level processing, they provide relaying services for all Diameter Calhoun et al. expires May 2002 [Page 23]
Internet-Draft November 2001 applications, and therefore MUST advertise the Relay Application Identifier. 2.9.4 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 stateful and MUST maintain transaction state. Translation of messages can only occur if the agent recognizes the application of a particular request, and therefore MUST only advertise their locally supported applications. +------+ ---------> +------+ ---------> +------+ | | RADIUS Request | | Diameter Request | | | NAS | | TLA | | HMS | | | RADIUS Answer | | Diameter Answer | | +------+ <--------- +------+ <--------- +------+ mno.net mno.net abc.com Figure 4: Translation of RADIUS to Diameter 3.0 Diameter Header A summary of the Diameter header format is shown below. The fields are transmitted in network byte order. Calhoun et al. expires May 2002 [Page 24]
Internet-Draft November 2001 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Ver | Message Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |R P E r r r r r| Command-Code | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Vendor-ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Hop-by-Hop Identifier | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | End-to-End Identifier | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | AVPs ... +-+-+-+-+-+-+-+-+-+-+-+-+- Version This Version field MUST be set to 1 to indicate Diameter Version 1. Message Length The Message Length field is three octets and indicates the length of the Diameter message including the header fields. Command Flags The Command Flags field is eight bits. The following bits are assigned: 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. If cleared, the message MUST be locally processed. E(rror) - If set, the message contains a protocol error, and the message will not conform to the ABNF described for this command. Messages with the 'E' bit set is commonly referred to as an error message. This bit MUST NOT be set in request messages. See section 7.2. r(eserved) - these flag bits are reserved for future use, and MUST be set to zero, otherwise an error MUST be sent to the sender. Command-Code The Command-Code field is three octets, and is used in order to communicate the command associated with the message. The 24-bit address space is managed by IANA (see section 11.2). Vendor-ID Calhoun et al. expires May 2002 [Page 25]
Internet-Draft November 2001 In the event that the Command-Code field contains a vendor specific command, the four octet Vendor-ID field contains the IANA assigned "SMI Network Management Private Enterprise Codes" [2] value. If the Command-Code field contains an IETF standard Command, the Vendor-ID field MUST be set to zero (0). Any vendor wishing to implement a vendor-specific Diameter command MUST use their own Vendor-ID along with their privately managed Command- Code address space, guaranteeing that they will not collide with any other vendor's vendor-specific command, nor with future IETF applications. Hop-by-Hop Identifier The Hop-by-Hop Identifier is an Unsigned32 field and aids in matching requests and replies. The sender MUST ensure that the Hop-by-Hop identifier in a request is unique on a given connection at any given time, and MAY attempt to ensure that the number is unique across reboots. The sender of an Answer message MUST ensure that the Hop-by-Hop Identifier field contains the same value that was found in the corresponding request. The Hop-by-Hop identifier is normally a monotonically increasing number, whose start value was randomly generated. An answer message that is received with an unknown Hop-by-Hop Identifier MUST be discarded. End-to-End Identifier The End-to-End Identifier is an Unsigned32 field and is used to detect duplicate messages. Upon reboot implementations MAY set the high order 12 bits to contain the low order 12 bits of current time, and the low order 20 bits to a random value. Senders of request messages MUST insert a unique identifier on each message. The identifier MUST remain locally unique for a period of at least 4 minutes, even across reboots. The originator of an Answer message MUST ensure that the End-to-End Identifier field contains the same value that was found in the corresponding request. The End-to-End Identifier MUST NOT be modified by relay agents. The combination of the Origin-Host and this field is used to detect duplicates. Duplicate requests SHOULD cause the same answer to be transmitted (modulo the hop-by-hop Identifier field and any routing AVPs that may be present), and MUST NOT affect any state that was set when the original request was processed. Duplicate answer messages that are to be locally consumed (see Section 6.2) SHOULD be silently discarded. AVPs AVPs are a method of encapsulating information relevant to the Diameter message. See section 4. for more information on AVPs. 3.1 Command Codes Calhoun et al. expires May 2002 [Page 26]
Internet-Draft November 2001 Each command Request/Answer pair is assigned a command code, and the sub-type (e.g. request or answer) is identified via the 'R' bit in the Command Flags field of the Diameter header. Every Diameter message MUST contain a command code in its header's Command-Code field, which is used to determine the action that is to be taken for a particular message. The following Command Codes are defined in the Diameter base protocol: Command-Name Abbrev. Code Reference -------------------------------------------------------- Abort-Session-Request ASR 274 8.5.1 Abort-Session-Answer ASA 274 8.5.2 Accounting-Request ACR 271 9.7.1 Accounting-Answer ACA 271 9.7.2 Capabilities-Exchange- CER 257 5.3.1 Request Capabilities-Exchange- CEA 257 5.3.2 Answer Device-Watchdog-Request DWR 280 5.5.1 Device-Watchdog-Answer DWA 280 5.5.2 Disconnect-Peer-Request DPR 282 5.4.1 Disconnect-Peer-Answer DPA 282 5.4.2 Re-Auth-Request RAR 258 8.3.1 Re-Auth-Answer RAA 258 8.3.2 Session-Termination- STR 275 8.4.1 Request Session-Termination- STA 275 8.4.2 Answer 3.2 Command Code ABNF specification Every Command Code defined MUST include a corresponding ABNF specification, which is used to define the AVPs that MUST or MAY be present. The following format is used in the definition: command-def = command-name "::=" diameter-message diameter-name = ALPHA *(ALPHA / DIGIT / "-") command-name = diameter-name ; The command-name has to be Command name, ; defined in the base or extended Diameter ; specifications. diameter-message = header [ *fixed] [ *required] [ *optional] [ *fixed] Calhoun et al. expires May 2002 [Page 27]
Internet-Draft November 2001 header = "< Diameter-Header:" [vendor-id] command-id [r-bit] [p-bit] [e-bit] ">" vendor-id = 1*DIGIT ":" ; The optional vendor-id is used to define ; vendor specific commands 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, indication that the message ; is proxiable. e-bit = ", ERR" ; If present, the 'E' bit in the Command ; Flags is set, indication 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. optional = [qual] "[" avp-name "]" ; The avp-name in the 'optional' rule cannot ; evaluate to any AVP Name which is included ; in a fixed or required rule. The AVP can ; appear anywhere in the message. qual = [min] "*" [max] ; See ABNF conventions, RFC 2234 section 6.6. ; The absence of any qualifiers implies that ; one and only one such AVP MUST be present. ; ; NOTE: "[" and "]" have a different meaning ; than in ABNF (see the optional rule, above). ; These braces cannot be used to express ; optional fixed rules (such as an optional Calhoun et al. expires May 2002 [Page 28]
Internet-Draft November 2001 ; ICV at the end.) To do this, the convention ; is '0*1fixed'. min = 1*DIGIT ; The minimum number of times the element may ; be present. The default value is zero. max = 1*DIGIT ; The maximum number of times the element may ; be present. The default value is infinity. A ; value of zero implies the AVP MUST NOT be ; present. avp-spec = diameter-name ; The avp-spec has to be an AVP Name, defined ; in the base or extended Diameter ; specifications. avp-name = avp-spec | "AVP" ; The string "AVP" stands for *any* arbitrary ; AVP Name, which does not conflict with the ; required or fixed position AVPs defined in ; the command code definition. The following is a definition of a fictitious command code: Example-Request ::= < Diameter-Header: 9999999, REQ, PXY > { User-Name } * { Origin-Host } * [ AVP ] 3.3 Diameter Command Naming Conventions Diameter commands typically includes one or more English words followed by the verb Request or Answer. Each English word is delimited by a hyphen. An 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 Calhoun et al. expires May 2002 [Page 29]
Internet-Draft November 2001 answer, which includes a result code that communicates one of the following: - The request was successful - The request failed - An additional request must be sent to provide information the peer requires prior to returning a successful or failed answer. - The receiver could not process the request, but provides information about a Diameter peer that is able to satisfy the request, known as redirect. Additional information, encoded within AVPs, MAY also be included in answer messages. 4.0 Diameter AVPs Diameter AVPs carry specific authentication, accounting, authorization, routing and security information as well as configuration details for the request and reply. Some AVPs MAY be listed more than once. The effect of such an AVP is specific, and is specified in each case by the AVP description. Each AVP of type OctetString MUST be padded to align on a 32 bit boundary, while other AVP types align naturally. NULL bytes are added to the end of the AVP Data field till a word boundary is reached. The length of the padding is not reflected in the AVP Length field. 4.1 AVP Header The fields in the AVP header MUST be sent in network byte order. The format of the header is: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | AVP Code | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |V M P r r r r r| AVP Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Vendor-ID (opt) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data ... +-+-+-+-+-+-+-+-+ AVP Code Calhoun et al. expires May 2002 [Page 30]
Internet-Draft November 2001 The AVP Code, combined with the Vendor-Id field, identifies the attribute uniquely. The first 256 AVP numbers, with the Vendor-Id set to zero (0) are reserved for backward compatibility with RADIUS and are to be interpreted as per NASREQ [7]. AVP numbers 256 and above are used for Diameter, which are allocated by IANA (see section 11.1). AVP Flags The AVP Flags field informs the receiver how each attribute must be handled. The 'r' (reserved) bits are unused and SHOULD be set to 0. Note that subsequent Diameter applications MAY define additional bits within the AVP Header, and an unrecognized bit SHOULD be considered an error. The 'P' bit is defined in [11]. The 'M' Bit, known as the Mandatory bit, indicates whether support of the AVP is required. If an AVP with the 'M' bit set is received by a Diameter client, server or proxy and either the AVP or its value is unrecognized, the message MUST be rejected. Diameter Relay and Redirect agents MUST NOT reject messages with unrecognized AVPs. A Diameter node that sets the 'M' bit in an AVP that is not defined in a given message's ABNF is at fault if the message is rejected. In order to provide service to the user, the node at fault MUST re-issue a request either without the AVP, or without setting its 'M' bit. Alternatively, the node at fault MAY decide to simply not provide service to the user. A Diameter node that rejects a message due to an unrecognized AVP with the 'M' bit set, and the AVP in question is defined in the message's ABNF, is at fault. In most cases the initiator of the failing request will not provide service to the user. AVPs with the 'M' bit cleared are informational only and a receiver that receives a message with such an AVP that is not supported, or whose value is not supported, MAY simply ignore the AVP. The 'V' bit, known as the Vendor-Specific bit, indicates whether the optional Vendor-ID field is present in the AVP header. When set the AVP Code belongs to the specific vendor code address space. Unless otherwise noted, AVPs will have the following default AVP Flags field settings: The 'M' bit MUST be set. The 'V' bit MUST NOT be set. AVP Length Calhoun et al. expires May 2002 [Page 31]
Internet-Draft November 2001 The AVP Length field is three octets, and indicates the length of this AVP including the AVP Code, AVP Length, AVP Flags, Reserved, the Vendor-ID field (if present) and the AVP data. If a message is received with an invalid attribute length, the message SHOULD be rejected. 4.2 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" [2] value, encoded in network byte order. Any vendor wishing to implement a vendor-specific Diameter AVP MUST use their own Vendor-ID along with their privately managed AVP address space, guaranteeing that they will not collide with any other vendor's vendor-specific AVP, nor with future IETF applications. A vendor ID value of zero (0) corresponds to the IETF adopted AVP values, as managed by the IANA. Since the absence of the vendor ID field implies that the AVP in question is not vendor specific, implementations SHOULD not use the zero (0) vendor ID. 4.3 AVP Base Data Format 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 AVP Base 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 do not align on a 32-bit boundary MUST have the necessary padding. 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). Calhoun et al. expires May 2002 [Page 32]
Internet-Draft November 2001 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). Float32 This represents floating point values of single precision as described by [30]. 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 [30]. The 64 bit value is transmitted in network byte order. The AVP Length field MUST be set to 16 (20 if the 'V' bit is enabled). Grouped The Data field is specified as a sequence of AVPs. Each of these AVPs follows - in the order in which they are specified - including their headers and padding. The AVP Length field is set to 8 (12 if the 'V' bit is enabled) plus the total length of all included AVPs, including their headers and padding. 4.4 Derived AVP Data Formats In addition to using the AVP Base Data Formats, applications may define data formats derived from the AVP Base Data Formats. An application that defines new AVP Derived Data Formats MUST include them in a section entitled "AVP Derived Data Formats", using the same format as the definitions below. Each new definition must be either defined or listed with a reference to the RFC that defines the format. The below AVP Derived Data Formats are commonly used by applications. IPAddress The IPAddress format is derived from the OctetString AVP Base Format. It represents 32 bit (IPv4) [17] or 128 bit (IPv6) [16] address, most significant octet first. The format of the Calhoun et al. expires May 2002 [Page 33]
Internet-Draft November 2001 address (IPv4 or IPv6) is determined by the length. If the attribute value is an IPv4 address, the AVP Length field MUST be 12 (16 if 'V' bit is enabled), otherwise the AVP Length field MUST be set to 24 (28 if the 'V' bit is enabled) for IPv6 addresses. Time The Time format is derived from the Unsigned32 AVP Base Format. This is 32 bit unsigned value containing the four most significant octets returned from NTP [18], in network byte order. This represent 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. NTP [18] describes a procedure to extend the time to 2104. UTF8String The UTF8String format is derived from the OctetString AVP Base Format. This is a human readable string represented using the ISO/IEC IS 10646-1 character set, encoded as an OctetString using the UTF-8 [24] transformation format described in RFC 2279. Since additional code points are added by amendments to the 10646 standard from time to time, implementations MUST be prepared to encounter any code point from 0x00000001 to 0x7fffffff. Byte sequences that do not correspond to the valid UTF-8 encoding of a code point or are outside this range are prohibited. Note that since a code point of 0x00000000 is prohibited, no octet will contain a value of 0x00. The use of control codes SHOULD be avoided. When it is necessary to represent a newline, 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 encoding is identical to the US-ASCII encoding. UTF-8 may require multiple bytes to represent a single Calhoun et al. expires May 2002 [Page 34]
Internet-Draft November 2001 character / code point; thus the length of a UTF8String in octets may be different from the number of characters encoded. Note that the size of an UTF8String is measured in octets, not characters. DiameterIdentity The DiameterIdentity format is derived from the OctetString AVP Base Format. It uses the UTF-8 encoding and has the same requirements as the UTF8String. In addition, it must follow the Uniform Resource Identifiers (URI) syntax [29] rules specified below: Diameter-Identity = "aaa://" fqdn [ port ] [ transport ] [ protocol ] [ transport-security ] fqdn = Fully Qualified Host Name port = ":" 1*DIGIT ; One of the ports used to listen for ; incoming connections. ; If absent, ; the default Diameter port (TBD) is ; assumed. transport-protocol = ( "tcp" | "sctp" | "udp" ) transport = ";transport=" transport-protocol ; One of the transports used to listen ; for incoming connections. If absent, ; the default SCTP [26] protocol is ; assumed. UDP MUST NOT be used when ; the aaa-protocol field is set to ; diameter. aaa-protocol = ( "diameter" | "radius" | "tacacs+" ) protocol = ";protocol=" aaa-protocol ; If absent, the default AAA protocol ; is diameter. transport-security = ( "none" | "TLS" ) ; Specifies whether TLS [or other future ; transport layer mechanisms supported] is ; to be used when communicating with the ; peer. The default value is none. The following are examples of valid Diameter host identities: Calhoun et al. expires May 2002 [Page 35]
Internet-Draft November 2001 aaa://host.abc.com;transport=tcp aaa://host.abc.com:6666;transport=tcp aaa://host.abc.com;protocol=diameter aaa://host.abc.com:6666;protocol=diameter aaa://host.abc.com:6666;transport=tcp;protocol=diameter aaa://host.abc.com:1813;transport=udp;protocol=radius Since multiple Diameter processes on a single host cannot listen for incoming connections on the same port on a given protocol, the DiameterIdentity of any process is guaranteed to be unique. Unless a Diameter node is sitting on the border of two routing domains (e.g. private and public), a Diameter node MUST advertise the same identity on all connections, via the CER and CEA's Origin-Host AVP. The same identity advertised in a connection's CER and CEA MUST be used in any AVP of type DiameterIdentity sent on that connection. When comparing AVPs of this format, it is necessary to add any absent fields with the default values prior to the comparison. For example, diameter-host.abc.com would be expanded to aaa://diameter- host.abc.com:TBD;protocol=diameter;transport=sctp; transport- security=none. Enumerated Enumerated is derived from the Integer32 AVP Base Format. This contains a list of valid values and their interpretation and is described in the Diameter application introducing the AVP. IPFilterRule The IPFilterRule format is derived from the OctetString AVP Base Format. It uses the UTF-8 encoding and has the same requirements as the UTF8String. 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 Calhoun et al. expires May 2002 [Page 36]
Internet-Draft November 2001 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. ipno/bits An IP number as above with a mask width of the form 1.2.3.4/24. In this case all IP numbers from 1.2.3.0 to 1.2.3.255 will match. The bit width MUST be valid for the IP version and the IP number MUST NOT have bits set beyond the mask. 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. 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. The first rule SHOULD be "deny in ip !assigned". With the TCP, UDP and SCTP protocols, optional ports may be specified as: {port|port-port}[,port[,...]] Calhoun et al. expires May 2002 [Page 37]
Internet-Draft November 2001 The `-' notation specifies a range of ports (including boundaries). Fragmented packets which have a non-zero offset (i.e. not the first fragment) will never match a rule which has one or more port specifications. See the frag option for details on matching fragmented packets. options: frag Match if the packet is a fragment and this is not the first fragment of the datagram. frag may not be used in conjunction with either tcpflags or TCP/UDP port specifications. ipoptions spec Match if the IP header contains the comma separated list of options specified in spec. The supported IP options are: ssrr (strict source route), lsrr (loose source route), rr (record packet route) and ts (timestamp). The absence of a particular option may be denoted with a `!'. tcpoptions spec Match if the TCP header contains the comma separated list of options specified in spec. The supported TCP options are: mss (maximum segment size), window (tcp window advertisement), sack (selective ack), ts (rfc1323 timestamp) and cc (rfc1644 t/tcp connection count). The absence of a particular option may be denoted with a `!'. established TCP packets only. Match packets that have the RST or ACK bits set. setup TCP packets only. Match packets that have the SYN bit set but no ACK bit. 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: Calhoun et al. expires May 2002 [Page 38]
Internet-Draft November 2001 fin, syn, rst, psh, ack and urg. The absence of a particular flag may be denoted with a `!'. A rule which contains a tcpflags specification can never match a fragmented packet which 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. The supported ICMP types are: echo reply (0), destination unreachable (3), source quench (4), redirect (5), echo request (8), router advertisement (9), router solicitation (10), time-to-live exceeded (11), IP header bad (12), timestamp request (13), timestamp reply (14), information request (15), information reply (16), address mask request (17) and address mask reply (18). There is one kind of packet that the access device MUST always discard, that is an IP fragment with a fragment offset of one. This is a valid packet, but it only has one use, to try to circumvent firewalls. An access device that is unable to interpret or apply a deny rule MUST terminate the session. An access device that is unable to interpret or apply a permit rule MAY apply a more restrictive rule. An access device MAY apply deny rules of its own before the supplied rules, for example to protect the access device owner's infrastructure. The rule syntax is a modified subset of ipfw(8) from FreeBSD, and the ipfw.c code may provide a useful base for implementations. QoSFilterRule The QosFilterRule format is derived from the OctetString AVP Base Format. It uses the UTF-8 encoding and has the same requirements as the UTF8String. Packets may be marked or metered based on the following information that is associated with it: Direction (in or out) Source and destination IP address (possibly masked) Calhoun et al. expires May 2002 [Page 39]
Internet-Draft November 2001 Protocol Source and destination port (lists or ranges) DSCP values (no mask or range) Rules for the appropriate direction are evaluated in order, with the first matched rule terminating the evaluation. Each packet is evaluated once. If no rule matches, the packet is treated as best effort. QoSFilterRule filters MUST follow the format: action dir proto from src to dst [options] tag - Mark packet with a specific DSCP [49]. The DSCP option MUST be included. meter - Meter traffic. The metering options MUST be included. dir "in" is from the terminal, "out" is to the terminal. proto An IP protocol specified by number. The "ip" keyword means any protocol will match. src and dst <address/mask> [ports] The <address/mask> may be specified as: ipno An IPv4 or IPv6 number in dotted- quad or canonical IPv6 form. Only this exact IP number will match the rule. ipno/bits An IP number as above with a mask width of the form 1.2.3.4/24. In this case all IP numbers from 1.2.3.0 to 1.2.3.255 will match. The bit width MUST be valid for the IP version and the IP number MUST NOT have bits set beyond the mask. 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. 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 Calhoun et al. expires May 2002 [Page 40]
Internet-Draft November 2001 terminal. The first rule SHOULD be "deny in ip !assigned". With the TCP, UDP and SCTP protocols, optional ports may be specified as: {port|port-port}[,port[,...]] The `-' notation specifies a range of ports (including boundaries). options: DSCP <color> color values as defined in [49]. Exact matching of DSCP values is required (no masks or ranges). the "deny" can replace the color_under or color_over values in the meter action for rate- dependent packet drop. metering <rate> <color_under> <color_over> The metering option provides Assured Forwarding, as defined in [50], and MUST be present if the action is set to meter. The rate option is the throughput, in bits per second, which is used by the access device to mark packets. Traffic above the rate is marked with the color_over codepoint, while traffic under the rate is marked with the color_under codepoint. The color_under and color_over options contain the drop preferences, and MUST conform to the recommended codepoint keywords described in [50] (e.g. AF13). The metering option also supports the strict limit on traffic required by Expedited Forwarding, as defined in [51]. The color_over option may contain the keyword "drop" to prevent forwarding of traffic that exceeds the rate parameter. The rule syntax is a modified subset of ipfw(8) from FreeBSD, and the ipfw.c code may provide a useful base for implementations. 4.5 Grouped AVP Values The Diameter protocol allows AVP values of type 'Grouped.' This Calhoun et al. expires May 2002 [Page 41]
Internet-Draft November 2001 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 4.0. The AVP Code numbering space of all AVPs included in a Grouped AVP is the same as for non-grouped AVPs. Further, if any of the AVPs encapsulated within a Grouped AVP has the 'M' (mandatory) bit set, the Grouped AVP itself MUST also include the 'M' bit set. Every Grouped AVP defined MUST include a corresponding grammar, using ABNF [31] (with modifications), as defined below. avp-def = name "::=" avp name-fmt = ALPHA *(ALPHA / DIGIT / "-") name = name-fmt ; The name has to be the name of an AVP, ; defined in the base or extended Diameter ; specifications. avp = header [ *fixed] [ *required] [ *optional] [ *fixed] header = "<AVP-Header:" avpcode [vendor] ">" avpcode = 1*DIGIT ; The AVP Code assigned to the Grouped AVP vendor = 1*DIGIT ; The Vendor-ID assigned to the Grouped AVP. ; If absent, the default value of zero is ; used. fixed = [qual] "<" avp-spec ">" required = [qual] "{" avp-spec "}" optional = [qual] "[" avp-name "]" ; The avp-name in the 'optional' rule cannot ; evaluate to any AVP Name which is included ; in a fixed or required rule. qual = [min] "*" [max] ; See ABNF conventions, RFC 2234 section 6.6. ; The absence of any qualifiers implies that Calhoun et al. expires May 2002 [Page 42]
Internet-Draft November 2001 ; one and only one such AVP MUST be present. ; ; NOTE: "[" and "]" have a different meaning ; than in ABNF (see the optional rule, above). ; These braces cannot be used to express ; optional fixed rules (such as an optional ; ICV at the end.) To do this, the convention ; is '0*1fixed'. min = 1*DIGIT ; The minimum number of times the element may ; be present. max = 1*DIGIT ; The maximum number of times the element may ; be present. avp-spec = name-fmt ; The avp-spec has to be an AVP Name, defined ; in the base or extended Diameter ; specifications. avp-name = avp-spec | "AVP" ; The string "AVP" stands for *any* arbitrary ; AVP Name, which does not conflict with the ; required or fixed position AVPs defined in ; the command code definition. 4.5.1 Example AVP with a Grouped Data type The Example AVP (AVP Code 999999) is of type Grouped and is used to clarify how Grouped AVP values work. The Grouped Data field has the following ABNF grammar: Example-AVP ::= < AVP Header: 999999 > { Origin-Host } 1*{ Session-Id } *[ AVP ] An Example AVP with Grouped Data follows. The Origin-Host AVP is required. In this case: Origin-Host = "example.com". One or more Session-Ids must follow. Here there are two: Calhoun et al. expires May 2002 [Page 43]
Internet-Draft November 2001 Session-Id = "grump.example.com:33041;23432;893;0AF3B81" Session-Id = "grump.example.com:33054;23561;2358;0AF3B82" optional AVPs included are Recovery-Policy = <binary> 2163bc1d0ad82371f6bc09484133c3f09ad74a0dd5346d54195a7cf0b35 2cabc881839a4fdcfbc1769e2677a4c1fb499284c5f70b48f58503a45c5 c2d6943f82d5930f2b7c1da640f476f0e9c9572a50db8ea6e51e1c2c7bd f8bb43dc995144b8dbe297ac739493946803e1cee3e15d9b765008a1b2a cf4ac777c80041d72c01e691cf751dbf86e85f509f3988e5875dc905119 26841f00f0e29a6d1ddc1a842289d440268681e052b30fb638045f7779c 1d873c784f054f688f5001559ecff64865ef975f3e60d2fd7966b8c7f92 Futuristic-Acct-Record = <binary> fe19da5802acd98b07a5b86cb4d5d03f0314ab9ef1ad0b67111ff3b90a0 57fe29620bf3585fd2dd9fcc38ce62f6cc208c6163c008f4258d1bc88b8 17694a74ccad3ec69269461b14b2e7a4c111fb239e33714da207983f58c 41d018d56fe938f3cbf089aac12a912a2f0d1923a9390e5f789cb2e5067 d3427475e49968f841 The data for the optional AVPs is represented in hex since the format of these AVPs is neither known at the time of definition of the Example-AVP group, nor (likely) at the time when the example instance of this AVP is interpreted - except by Diameter implementations which support the same set of AVPs. The encoding example illustrates how padding is used and how length fields are calculated. Also note that AVPs may be present in the Grouped AVP value which the receiver cannot interpret (here, the Recover-Policy and Futuristic-Acct-Record AVPs). This AVP would be encoded as follows: Calhoun et al. expires May 2002 [Page 44]
Internet-Draft November 2001 0 1 2 3 4 5 6 7 +-------+-------+-------+-------+-------+-------+-------+-------+ 0 | Example AVP Header (AVP Code = 999999), Length = 468 | +-------+-------+-------+-------+-------+-------+-------+-------+ 8 | Origin-Host AVP Header (AVP Code = 264), Length = 19 | +-------+-------+-------+-------+-------+-------+-------+-------+ 16 | 'e' | 'x' | 'a' | 'm' | 'p' | 'l' | 'e' | '.' | +-------+-------+-------+-------+-------+-------+-------+-------+ 24 | 'c' | 'o' | 'm' |Padding| Session-Id AVP Header | +-------+-------+-------+-------+-------+-------+-------+-------+ 32 | (AVP Code = 263), Length = 50 | 'g' | 'r' | 'u' | 'm' | +-------+-------+-------+-------+-------+-------+-------+-------+ . . . +-------+-------+-------+-------+-------+-------+-------+-------+ 64 | 'A' | 'F' | '3' | 'B' | '8' | '1' |Padding|Padding| +-------+-------+-------+-------+-------+-------+-------+-------+ 68 | Session-Id AVP Header (AVP Code = 263), Length = 51 | +-------+-------+-------+-------+-------+-------+-------+-------+ 72 | 'g' | 'r' | 'u' | 'm' | 'p' | '.' | 'e' | 'x' | +-------+-------+-------+-------+-------+-------+-------+-------+ . . . +-------+-------+-------+-------+-------+-------+-------+-------+ 104 | '0' | 'A' | 'F' | '3' | 'B' | '8' | '2' |Padding| +-------+-------+-------+-------+-------+-------+-------+-------+ 112 | Recovery-Policy Header (AVP Code = 8341), Length = 223 | +-------+-------+-------+-------+-------+-------+-------+-------+ 120 | 0x21 | 0x63 | 0xbc | 0x1d | 0x0a | 0xd8 | 0x23 | 0x71 | +-------+-------+-------+-------+-------+-------+-------+-------+ . . . +-------+-------+-------+-------+-------+-------+-------+-------+ 320 | 0x2f | 0xd7 | 0x96 | 0x6b | 0x8c | 0x7f | 0x92 |Padding| +-------+-------+-------+-------+-------+-------+-------+-------+ 328 | Futuristic-Acct-Record Header (AVP Code = 15930), Length = 137| +-------+-------+-------+-------+-------+-------+-------+-------+ 336 | 0xfe | 0x19 | 0xda | 0x58 | 0x02 | 0xac | 0xd9 | 0x8b | +-------+-------+-------+-------+-------+-------+-------+-------+ . . . +-------+-------+-------+-------+-------+-------+-------+-------+ 464 | 0x41 |Padding|Padding|Padding| +-------+-------+-------+-------+ 4.6 Diameter Base Protocol AVPs The following table describes the Diameter AVPs defined in the base protocol, their AVP Code values, types, possible flag values and whether the AVP MAY be encrypted. Calhoun et al. expires May 2002 [Page 45]
Internet-Draft November 2001 Due to space constraints, the short form DiamIdent is used to represent DiameterIdentity. +---------------------+ | AVP Flag rules | |----+-----+----+-----|----+ AVP Section | | |SHLD| MUST|MAY | Attribute Name Code Defined Data Type |MUST| MAY | NOT| NOT|Encr| -----------------------------------------|----+-----+----+-----|----| Accounting- 482 9.8.2 Unsigned32 | M | P | | V | Y | Interim-Interval | | | | | | Accounting- 50 9.8.5 UTF8String | M | P | | V | Y | Multi-Session-Id | | | | | | Accounting- 485 9.8.3 Unsigned32 | M | P | | V | Y | Record-Number | | | | | | Accounting- 480 9.8.1 Enumerated | M | P | | V | Y | Record-Type | | | | | | Accounting- 44 9.8.4 OctetString| M | P | | V | Y | RADIUS-Session-Id | | | | | | Accounting- 287 9.8.6 Unsigned64 | M | P | | V | Y | Sub-Session-Id | | | | | | Acct- 259 6.9 Integer32 | M | P | | V | N | Application-Id | | | | | | Auth- 258 6.8 Integer32 | M | P | | V | N | Application-Id | | | | | | Auth-Request- 274 8.7 Enumerated | M | P | | V | N | Type | | | | | | Authorization- 291 8.9 Unsigned32 | M | P | | V | N | Lifetime | | | | | | Auth-Grace- 276 8.10 Unsigned32 | M | P | | V | N | Period | | | | | | Auth-Session- 277 8.11 Enumerated | M | P | | V | N | State | | | | | | Re-Auth-Request- 285 8.12 Enumerated | M | P | | V | N | Type | | | | | | Class 25 8.20 OctetString| M | P | | V | Y | Destination-Host 293 6.5 DiamIdent | M | P | | V | N | Destination- 283 6.6 UTF8String | M | P | | V | N | Realm | | | | | | Disconnect-Cause 273 5.4.3 Enumerated | M | P | | V | N | Error-Message 281 7.3 OctetString| | P | | V | N | Error-Reporting- 294 7.4 UTF8String | | P | | V | N | Host | | | | | | Failed-AVP 279 7.5 Grouped | M | P | | V | N | Firmware- 267 5.3.4 Unsigned32 | | P | | V,M | N | Revision | | | | | | Host-IP-Address 257 5.3.5 IPAddress | M | P | | V | N | -----------------------------------------|----+-----+----+-----|----| Calhoun et al. expires May 2002 [Page 46]
Internet-Draft November 2001 +---------------------+ | AVP Flag rules | |----+-----+----+-----|----+ AVP Section | | |SHLD| MUST|MAY | Attribute Name Code Defined Data Type |MUST| MAY | NOT| NOT|Encr| -----------------------------------------|----+-----+----+-----|----| Multi-Round- 272 8.19 Unsigned32 | M | P | | V | Y | Time-Out | | | | | | Origin-Host 264 6.3 DiamIdent | M | P | | V | N | Origin-Realm 296 6.4 UTF8String | M | P | | V | N | Origin-State-Id 278 8.16 Unsigned32 | M | P | | V | N | Product-Name 269 5.3.7 UTF8String | | P | | V | N | Proxy-Host 280 6.7.3 IPAddress | M | | | P,V | N | Proxy-Info 284 6.7.2 Grouped | M | | | P,V | N | Proxy-State 33 6.7.4 OctetString| M | | | P,V | N | Redirect-Host 292 6.11 DiamIdent | M | | | V | N | Redirect-Host- 261 6.12 Enumerated | M | P | | V | N | Usage | | | | | | Redirect-Max- 262 6.13 Unsigned32 | M | P | | V | N | Cache-Time | | | | | | Result-Code 268 7.1 Unsigned32 | M | P | | V | N | Route-Record 282 6.7.1 DiamIdent | M | | | P,V | N | Session-Id 263 8.8 UTF8String | M | P | | V | Y | Session-Timeout 27 8.13 Unsigned32 | M | P | | V | N | Session-Binding 270 8.17 Unsigned32 | M | P | | V | Y | Session-Server- 271 8.18 Enumerated | M | P | | V | Y | Failover | | | | | | Supported- 265 5.3.6 Unsigned32 | M | P | | V | N | Vendor-Id | | | | | | Termination- 295 8.15 Enumerated | M | P | | V | N | Cause | | | | | | User-Name 1 8.14 UTF8String | M | P | | V | Y | Vendor-Id 266 5.3.3 Unsigned32 | M | P | | V | N | Vendor-Specific- 260 6.10 Grouped | M | P | | V | N | Application-Id | | | | | | -----------------------------------------|----+-----+----+-----|----| 5.0 Diameter Peers This section describes how Diameter nodes establish connections and communicate with peers. 5.1 Peer Connections Although a Diameter node may have many possible peers that it is able to communicate with, it may not be economical to have an established Calhoun et al. expires May 2002 [Page 47]
Internet-Draft November 2001 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 alloted timeframe, no new requests should be forwarded to the peer, but failover procedures are not invoked. When an active peer is moved to this mode, additional connections SHOULD be established to ensure that the necessary number of active connections exists. There are two ways that a peer is removed from the suspect peer list: 1. The peer is no longer reachable, causing the transport connection to be shutdown. The peer is moved to the closed state. 2. Three watchdog messages are exchanged with accepted round trip times, and the connection to the peer is considered stabilized. In the event the peer being removed is either the primary or secondary, an alternate peer SHOULD replace the deleted peer, and assume the role of either primary or secondary. 5.2 Diameter Peer Discovery Allowing for dynamic Diameter agent discovery will make it possible for simpler and more robust deployment of Diameter services. In order to promote interoperable implementations of Diameter peer discovery, the following mechanisms are described. These are based on existing IETF standards. There are two cases where Diameter peer discovery may be performed. The first is when a Diameter client needs to discover a first-hop Diameter agent. The second case is when a Diameter agent needs to discover another agent - for further handling of a Diameter operation. In both cases, the following 'search order' is recommended: 1. The Diameter implementation consults its list of static (manual) configured Diameter agent locations. These will be Calhoun et al. expires May 2002 [Page 48]
Internet-Draft November 2001 used if they exist and respond. 2. The Diameter implementation uses SLPv2 [28] to discover Diameter services. The Diameter service template [32] is included in Appendix A. It is recommended that SLPv2 security be deployed (this requires distributing keys to SLPv2 agents). This is discussed further in Appendix A. SLPv2 will allow Diameter implementations to discover the location of Diameter agents in the local site, as well as their characteristics. Diameter agents with specific capabilities (say support for the Mobile IP application) can be requested, and only those will be discovered. 3. The Diameter implementation uses DNS to request the SRV RR [33] for the '_diameter._sctp' and/or '_diameter._tcp' server in a particular realm. The Diameter implementation has to know in advance which realm to look for a Diameter agent in. This could be deduced, for example, from the 'realm' in a NAI that a Diameter implementation needed to perform a Diameter operation on. 3.1 If the destination address is a numeric IP address, the requestor contacts the peer at the given address and the port number specified in the SRV record or, if not specified, the default port (TBD). 3.2 The results of the query or queries are merged and ordered based on priority. Then, the searching technique outlined in [46] is used to select servers in order. The requestor attempts to contact each peer in the order listed, at the port number specified in the SRV record. If none of the servers can be contacted, the requestor gives up. If there are no SRV records, DNS address records are used, as described below. 3.3 If there are no SRV records, the requestor queries the DNS server for address records for the destination address '_diameter._sctp'.realm or '_diameter._tcp'.realm. Address records include A RR's, AAAA RR's, A6 RR's or other similar records, chosen according to the requestor's network protocol capabilities. If the DNS server returns no address records, the requestor gives up. If there are address records, the same rules as in step 3.2 apply. Requestors MUST NOT cache query results except according to the Calhoun et al. expires May 2002 [Page 49]
Internet-Draft November 2001 rules in [33]. Diameter allows AAA peers to protect the integrity and privacy of communication as well as to perform end-point authentication. Still, it is prudent to employ DNS Security as a precaution when using DNS SRV RRs to look up the location of a Diameter agent [34, 35, 36]. A dynamically discovered peer causes an entry in the Peer Table (see section 2.7) to be created. Note that entries created via DNS MUST expire (or be refreshed) within the DNS TTL. If a peer is discovered outside of the local realm, a routing table entry (see Section 2.8) for the peer's realm is created. The routing table entry's expiration MUST match the peer's expiration value. 5.3 Capabilities Exchange When two Diameter peers establish a transport connection, they MUST exchange the Capabilities Exchange messages, as specified in the peer state machine (see section 5.6). This message allows the discovery of a peer's identity and its capabilities (protocol version number, supported Diameter applications, etc.) The receiver only issues commands to its peers that have advertised support for the Diameter application that defines the command. A Diameter node MUST cache the supported applications in order to ensure that unrecognized commands and/or AVPs are not unnecessarily sent to a peer. A receiver of a Capabilities-Exchange-Req (CER) message which 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 2.5) MUST be interpreted as having common applications with the peer. 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. The CER and CEA messages MUST NOT be proxied, or redirected. Since the CER/CEA messages cannot be proxied, it is still possible that an upstream agent receives a message for which it has no available peers to handle the application that corresponds to the Command-Code. In such instances, the 'E' bit is set in the answer Calhoun et al. expires May 2002 [Page 50]
Internet-Draft November 2001 message (see Section 7.2) with the Result-Code AVP set to DIAMETER_UNABLE_TO_DELIVER to inform the downstream to take action (e.g. re-routing request to an alternate peer). With the exception of the Capabilities-Exchange-Request message, a message of type Request that includes the Auth-Application-Id or Acct-Application-Id AVPs, or a message with an application-specific command code, MAY only be forwarded to a host that has explicitly advertised support for the application (or has advertised the Relay Application Identifier). 5.3.1 Capabilities-Exchange-Request The Capabilities-Exchange-Request (CER), indicated by the Command- Code set to 257 and the Command Flags' 'R' bit set, is sent to exchange local capabilities. Upon detection of a transport failure, this message MUST NOT be sent to an alternate peer. When Diameter is run over SCTP [26], which allows for connections to span multiple interfaces, hence 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 ] * [ Acct-Application-Id ] * [ Vendor-Specific-Application-Id ] [ Firmware-Revision ] * [ AVP ] 5.3.2 Capabilities-Exchange-Answer The Capabilities-Exchange-Answer (CEA), indicated by the Command-Code set to 257 and the Command Flags' 'R' bit cleared, is sent in response to a CER message. Calhoun et al. expires May 2002 [Page 51]
Internet-Draft November 2001 When Diameter is run over SCTP [26], which allows for 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 ] * [ 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" [2] value assigned to the vendor of the Diameter device. In combination with the Supported-Vendor-Id AVP (section 5.3.6), this MAY be used in order to know which vendor specific attributes may be sent to the peer. It is also envisioned that the combination of the Vendor-Id, Product-Name (section 5.3.7) and the Firmware-Revision (section 5.3.4) AVPs MAY provide very useful debugging information. A Vendor-Id value of zero in the CER or CEA messages is reserved and indicates that the Diameter peer is in the experimental or concept stage and that an IANA Private Enterprise Number has yet to be obtained by the implementor. 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 Calhoun et al. expires May 2002 [Page 52]
Internet-Draft November 2001 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 IPAddress 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 [26] MUST be advertised in the CER and CEA messages by including a Host- IP-Address AVP for each address. This AVP MUST ONLY be used in the CER and CEA messages. 5.3.6 Supported-Vendor-Id AVP The Supported-Vendor-Id AVP (AVP Code 265) is of type Unsigned32 and contains the IANA "SMI Network Management Private Enterprise Codes" [2] value assigned to a vendor other than the device vendor. This is used in the CER and CEA messages in order to inform the peer that the sender supports a subset of the vendor-specific commands and/or AVPs defined by the vendor identified in this AVP. 5.3.7 Product-Name AVP The Product-Name AVP (AVP Code 269) is of type UTF8String, and contains the vendor assigned name for the product. The Product-Name AVP SHOULD remain constant across firmware revisions for the same product. 5.4 Disconnecting Peer connections When a Diameter node disconnects one of its transport connections, its peer cannot know the reason for the disconnect, and will most likely assume that a connectivity problem occurred, or that the peer has rebooted. In these cases, the peer may periodically attempt to reconnect, as stated in section 2.1. In the event that the disconnect was a result of either a shortage of internal resources, or simply that the node in question has no intentions of forwarding any Diameter messages to the peer in the foreseeable future, a periodic connection request would not be welcomed. The Disconnection-Reason AVP contains the reason the Diameter node issued the Disconnect-Peer- Request message. Calhoun et al. expires May 2002 [Page 53]
Internet-Draft November 2001 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 is returned, which SHOULD contain an error if messages have recently be forwarded, and are likely in flight, which would otherwise cause a race condition. The receiver of the Disconnect-Peer-Answer initiates the transport disconnect. 5.4.1 Disconnect-Peer-Request The Disconnect-Peer-Request (DPR), indicated by the Command-Code set to 282 and the Command Flags' 'R' bit set, is sent to a peer to inform its intentions to shutdown the transport connection. Upon detection of a transport failure, this message MUST NOT be sent to an alternate peer. Message Format <DPR> ::= < Diameter Header: 282, REQ > { Origin-Host } { Origin-Realm } { Disconnect-Cause } 5.4.2 Disconnect-Peer-Answer The Disconnect-Peer-Answer (DPA), indicated by the Command-Code set to 282 and the Command Flags' 'R' bit cleared, is sent as a response to the Disconnect-Peer-Request message. Upon receipt of this message, the transport connection is shutdown. Message Format <DPA> ::= < Diameter Header: 282 > { Result-Code } { Origin-Host } { Origin-Realm } [ Error-Message ] * [ Failed-AVP ] 5.4.3 Disconnect-Cause AVP The Disconnect-Cause AVP (AVP Code 273) is of type Enumerated. A Diameter node MUST include this AVP in the Disconnect-Peer-Request Calhoun et al. expires May 2002 [Page 54]
Internet-Draft November 2001 message to inform the peer of the reason for its intention to shutdown the transport connection. The following values are supported: REBOOTING 0 A scheduled reboot is imminent. BUSY 1 The peer's internal resources are constrained, and it has determined that the transport connection needs to be shutdown. 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 foreseeable future. ELECTION_LOST 3 The peer has determined that it has lost the election process and has therefore disconnected the transport connection. 5.5 Transport Failure Detection Given the nature of the Diameter protocol, it is recommended that transport failures be detected as soon as possible. Detecting such failures will minimize the occurrence of messages sent to unavailable agents, resulting in unnecessary delays, and will provide better failover performance. The Device-Watchdog-Request and Device- Watchdog-Answer messages, defined in this section, are used to pro- actively detect transport failures. 5.5.1 Device-Watchdog-Request The Device-Watchdog-Request (DWR), indicated by the Command-Code set to 280 and the Command Flags' 'R' bit set, is sent to a peer when no traffic has been exchanged between two peers (see Section 5.5.3). Upon detection of a transport failure, this message MUST NOT be sent to an alternate peer. Message Format <DWR> ::= < Diameter Header: 280, REQ > { Origin-Host } { Origin-Realm } [ Origin-State-Id ] Calhoun et al. expires May 2002 [Page 55]
Internet-Draft November 2001 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 ] [ Original-State-Id ] 5.5.3 Transport Failure Algorithm The transport failure algorithm is defined in [52]. All Diameter implementations MUST support the algorithm defined in the specification in order to be compliant to the Diameter base protocol. 5.5.4 Failover/Failback Procedures In the event that a transport failure is detected with a peer, it is necessary for all pending request messages to be forwarded to an alternate agent, if possible. This is commonly referred to as failover. In order for a Diameter node to perform failover procedures, it is necessary for the node to maintain a pending message queue for a given peer. When an answer message is received, the corresponding request is removed from the queue. The Hop-by-Hop Identifier field is used to match the answer with the queued request. When a transport failure is detected, all messages in the queue are sent to an alternate agent, if possible. 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 Calhoun et al. expires May 2002 [Page 56]
Internet-Draft November 2001 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 [52], which is used to establish transport connections with Diameter peers. When the state machine below requests a transport connection with the peer, the state machine in [52] is invoked. Once the connection has been established, the state machine in this section is followed. There may be at most one transport connection between any two peers over which Diameter messages may be passed. This state machine is intended to handle both the simple case, in which one peer initiates a connection to the other, and the complex case, in which each peer simultaneously initiates a connection to the other. In the complex case, an election occurs to determine which transport connection will survive. It is important to note that the port on which a connection is initiated from MUST NOT be the port Diameter listens for incoming connections. I- is used to represent the initiator (connecting) connection, while the R- is used to represent the responder (listening) connection. The lack of a prefix indicates that the event or action is the same regardless of the connection on which the event occurred. The stable states that a state machine may be in are Closed, I-Open and R-Open; all other states are intermediate. Note that I-Open and R-Open are equivalent except for whether the initiator or responder transport connection is used for communication. A CER message is always sent on the initiating connection immediately after the connection request is successfully completed. In the case of an election, one of the two connections will shut down. The Calhoun et al. expires May 2002 [Page 57]
Internet-Draft November 2001 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. 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. 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 Calhoun et al. expires May 2002 [Page 58]
Internet-Draft November 2001 R-Open Send-Message R-Snd-Message R-Open R-Rcv-Message Process R-Open WatchDog-Timer R-Snd-DWR R-Open R-Rcv-DWR Process-DWR, R-Open R-Snd-DWA R-Rcv-DWA Process-DWA R-Open R-Conn-CER R-Snd-CEA R-Open R-Reject Stop R-Snd-DPR Closing R-Rcv-DPR R-Snd-DPA, Closed R-Disc R-Peer-Disc R-Disc Closed R-Rcv-CER R-Snd-CEA R-Open R-Rcv-CEA Process-CEA R-Open I-Open Send-Message I-Snd-Message I-Open I-Rcv-Message Process I-Open WatchDog-Timer I-Snd-DWR I-Open I-Rcv-DWR Process-DWR, I-Open I-Snd-DWA I-Rcv-DWA Process-DWA I-Open R-Conn-CER R-Reject I-Open Stop I-Snd-DPR Closing I-Rcv-DPR I-Snd-DPA, Closed I-Disc I-Peer-Disc I-Disc Closed I-Rcv-CER I-Snd-CEA I-Open I-Rcv-CEA Process-CEA I-Open Closing I-Rcv-DPA I-Disc Closed R-Rcv-DPA R-Disc Closed Timeout Error Closed I-Peer-Disc I-Disc Closed R-Peer-Disc R-Disc Closed 5.6.1 Incoming connections When a connection request is received from a Diameter peer, it is not, in the general case, possible to know the identity of that peer until a CER is received from it. This is because the identity of a Diameter peer is determined by host and port; and the source port of an incoming connection is arbitrary. Upon receipt of CER, the identity of the connecting peer can be uniquely determined from Origin-Host. For this reason, a Diameter peer must employ logic separate from the state machine to receive connection requests, accept them, and await Calhoun et al. expires May 2002 [Page 59]
Internet-Draft November 2001 CER. Once CER arrives on a new connection, the Origin-Host which identifies the peer is used to locate the state machine associated with that peer, and the new connection and CER are passed to the state machine as an R-Conn-CER event. The logic that handles incoming connections SHOULD close and discard the connection if any message other than CER arrives, or if an implementation-defined timeout occurs prior to receipt of CER. Because handling of incoming connections up to and including receipt of CER requires logic separate from that of any individual state machine associated with a particular peer, it is described separately in this section rather than in the state machine above. 5.6.2 Events Transitions and actions in the automaton are caused by events. In this section we will ignore the -I and -R prefix, since the actual event would be identical, but would occur on one of two possible connections. Start The Diameter application has signaled that a connection should be initiated with the peer. The state machine in [52] is to be initiated to create a transport connection. R-Conn-CER An acknowledgement is received from the state machine in [52] stating that the transport connection has been established, and the associated CER has arrived. Rcv-Conn-Ack A positive acknowledgement is received from the state machine in [52] confirming that the transport connection is established. Rcv-Conn-Nack A negative acknowledgement was received from the state machine in [52] stating that the transport connection was not established. Timeout An application-defined timer has expired while waiting for some event. Rcv-CER A CER message from the peer was received. Rcv-CEA A CEA message from the peer was received. Rcv-Non-CEA A message other than CEA from the peer was Calhoun et al. expires May 2002 [Page 60]
Internet-Draft November 2001 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, DWR, or DWA was received. WatchDog-Timer The Watchdog timer expired, indicating that a DWR message is to be sent to the peer. Rcv-DWR A DWR message was received. Rcv-DWA A DWA message 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- prefix, since the actual action would be identical, but would occur on one of two possible connections. Snd-Conn-Req A transport connection is initiated with the peer. The state machine in [52] is used to establish the transport connection 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 Calhoun et al. expires May 2002 [Page 61]
Internet-Draft November 2001 processed. Snd-Conn-Ack an acknowledgement is received from the state machine in [52] confirming that the transport connection is established. Snd-CER A CER message is sent to the peer. Snd-CEA A CEA message is sent to the peer. Cleanup If necessary, the connection is shutdown, and any local resources are freed. Error The transport layer connection is disconnected, either politely or abortively, in response to an error condition. Local resources are freed. Process-CEA A received CEA is processed. Snd-DPR A DPR message is sent to the peer. Snd-DPA A DPA message is sent to the peer. Disc The transport layer connection is disconnected, and local resources are freed. Elect An election occurs (see Section 5.6.4 for more information). Snd-Message A message is sent. Snd-DWR A DWR message is sent. Snd-DWA A DWA message is sent. Process-DWR The DWR message is serviced. Process-DWA The DWA message is serviced. Process A message is serviced. 5.6.4 The Election Process The election is performed on the responder. The responder compares the Origin-Host received in the CER sent by its peer with its own Origin-Host. If the local Diameter entity's Origin-Host is higher than the peer's, a Win-Election event is issued locally. Calhoun et al. expires May 2002 [Page 62]
Internet-Draft November 2001 The comparison proceeds by considering the shorter OctetString to be null-padded to the length of the longer, then performing an octet by octet unsigned comparison with the first octet being most significant. Hanging octets are assumed to have value 0x80, but dimpled octets are ignored. 6.0 Diameter message processing This section describes how Diameter requests and answers are created and processed. 6.1 Diameter request routing overview A request is sent towards its final destination using a combination of the Destination-Realm and Destination-Host AVPs, in one of these three combinations: - a request that is not proxiable (such as CER) MUST NOT contain either Destination-Realm or Destination-Host AVPs. - a request that needs to be sent to a home server serving a specific realm, but not to a specific server (such as the first request of a series of round-trips), MUST contain a Destination- Realm AVP, but MUST NOT contain a Destination-Host AVP. - a request that needs to be sent to a specific home server among those serving a given realm, MUST contain both the Destination- Realm and Destination-Host AVPs. The Destination-Host AVP is used as described above when the destination of the request is fixed, which includes: - Authentication requests that span multiple round trips - A Diameter message that uses a security mechanism that makes use of a pre-established session key shared between the source and the final destination of the message. - Server initiated messages that MUST be received by a specific Diameter client (e.g. access device), such as the Abort-Session- Request message, which is used to request that a particular user's session be terminated. Note that an agent can forward a request to a host described in the Destination-Host AVP only if the host in question is included in its peer table (see section 2.7). Otherwise, the request is routed based on the Destination-Realm only (see sections 6.1.6). The Destination-Realm AVP MUST be present if the message is routable. A message that MUST NOT be relayed, proxied or redirected MUST NOT include the Destination-Realm in its ABNF. The value of the Destination-Realm AVP MAY be extracted from the User-Name AVP, or Calhoun et al. expires May 2002 [Page 63]
Internet-Draft November 2001 other application-specific methods. When a message is received, the message is processed in the following order: 1. If the message is destined for the local host, the procedures listed in section 6.1.4 are followed. 2. If the message is intended for a Diameter peer with whom the local host is able to directly communicate, the procedures listed in section 6.1.5 are followed. This is known as Request Forwarding. 3. The procedures listed in section 6.1.6 are followed, which is known as Request Routing. 4. If none of the above are successful, an answer is returned with the Result-Code set to DIAMETER_UNABLE_TO_DELIVER. For routing of Diameter messages to work within an administrative domain, all Diameter nodes within the realm MUST be peers. If intermediate nodes are desired (see Figure 5), the destination node MUST be in a subrealm and routes to that subrealm MUST exist in the routing table on the sending node and all intermediate nodes. Figure 5 shows an example of a hierarchical network that requires the use of subrealms. In such a network, routing must be performed with longest match from right. +---------+ | abc.com | +---------+ +-------+ +-------+ | agent | | agent | +-------+ +-------+ +-------------+ +--------------+ +-------------+ +--------------+ | eng.abc.com | | acct.abc.com | | mkt.abc.com | | exec.abc.com | +-------------+ +--------------+ +-------------+ +--------------+ Figure 5: Hierarchical administrative domain Note the processing rules contained in this section are intended to be used as general guidelines to Diameter developers. Certain implementations MAY use different methods than the ones described here, and still be in compliance with the protocol specification. 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: Calhoun et al. expires May 2002 [Page 64]
Internet-Draft November 2001 - the Command-Code should be set to the appropriate value - the 'R' bit should be set - the End-to-End Identifier should be set to a locally unique value - the Origin-Host and Origin-Realm AVPs MUST be set to the appropriate values, used to identify the source of the message - the Destination-Host and Destination-Realm AVPs MUST be set to the appropriate values as described in section 6.1. 6.1.2 Sending a Request When sending a request, either originated locally, or as the result of a forwarding or routing operation, the following procedures MUST be followed: - the Hop-by-Hop Identifier should be set to a locally unique value - The message should be saved in the list of pending requests. Other actions to perform on the message based on the particular role the agent is playing are described in the following sections. 6.1.3 Receiving Requests A relay or proxy agent MUST check for forwarding loops when receiving requests. A loop is detected if the server finds its own identity in a Route-Record AVP. When such an event occurs, the agent MUST answer with the Result-Code AVP set to DIAMETER_LOOP_DETECTED. 6.1.4 Processing Local Requests A request is known to be for local consumption when one of the following conditions occur: - The Destination-Host AVP contains the local host's identity, - The Destination-Host AVP is not present, the Destination-Realm AVP contains a realm the server is configured to process locally, and the Diameter application is locally supported, or - Both the Destination-Host and the Destination-Realm are not present. When a request is locally processed, the rules in section 6.2 should be used to generate the corresponding answer. 6.1.5 Request Forwarding Calhoun et al. expires May 2002 [Page 65]
Internet-Draft November 2001 Request forwarding is done using the Diameter Peer Table. The Diameter peer table contains all of the peers that the local node is able to directly communicate with. When a request is received, and the host encoded in the Destination- Host AVP is one that is present in the peer table, the message SHOULD be forwarded to the peer. 6.1.6 Request Routing Diameter request message routing is done via realms. A Diameter message that is proxyable MUST include the target realm in the Destination-Realm AVP. 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 MAY have a list of externally supported realms. When a request is received that includes a realm that is not locally supported, the message is routed to the peer configured in the Realm Routing Table table (see section 2.8). 6.1.7 Redirecting requests When a redirect agent receives a request whose routing entry is set to REDIRECT, it MUST reply with an answer message with the 'E' bit set, while maintaining the Hop-by-Hop Identifier in the header, and include the Result-Code AVP to DIAMETER_REDIRECT_INDICATION. Each of the servers associated with the routing entry are added in separate Redirect-Host AVP. Calhoun et al. expires May 2002 [Page 66]
Internet-Draft November 2001 +------------------+ | Diameter | | Redirect Agent | +------------------+ ^ | 2. command + 'E' bit 1. Request | | Result-Code = joe@xyz.com | | DIAMETER_REDIRECT_INDICATION + | | Redirect-Host AVP(s) | v +---------+ 3. Request +----------+ | abc.net |------------->| xyz.net | | Relay | | Diameter | | Agent |<-------------| Server | +---------+ 4. Answer +----------+ Figure 6: Diameter Redirect Agent Redirect agents MAY also include the certificate of the servers in the Redirect-Host AVP(s). These certificates are encapsulated in a CMS-Cert AVP [11]. The receiver of the answer message with the 'E' bit set, and the Result-Code AVP set to DIAMETER_REDIRECT_INDICATION uses the hop-by- hop field in the Diameter header to identify the request in the pending message queue (see Section 5.3) that is to be redirected. If no transport connection exists with the new agent, one is created, and the request is sent directly to it. 6.1.8 Relaying and Proxying Requests A relay or proxy agent MUST append a Route-Record AVP to all requests forwarded. The AVP contains the identity of the peer the request was received from. The Hop-by-Hop identifier in the request is saved, and replaced with a locally unique value. The source of the request is also saved, which includes the IP address, port and protocol. Relay and Proxy agents MAY include the Proxy-Info AVP in requests if it requires access any local state information when the corresponding response is received. Alternatively, it MAY simply use local storage to store state information. The message is then forwarded to the next hop, as identified in the Realm Routing Table. Figure 7 provides an example of message routing using the procedures listed in these sections. Calhoun et al. expires May 2002 [Page 67]
Internet-Draft November 2001 (Origin-Host=nas.mno.net) (Origin-Host=nas.mno.net) (Origin-Realm=mno.net) (Origin-Realm=mno.net) (Destination-Realm=abc.com) (Destination-Realm=abc.com) (Route-Record=nas.mno.net) +------+ ------> +------+ ------> +------+ | | (Request) | | (Request) | | | NAS +-------------------+ DRL +-------------------+ HMS | | | | | | | +------+ <------ +------+ <------ +------+ mno.net (Answer) mno.net (Answer) abc.com (Origin-Host=hms.abc.com) (Origin-Host=hms.abc.com) (Origin-Realm=abc.com) (Origin-Realm=abc.com) Figure 7: Routing of Diameter messages 6.2 Diameter Answer Processing When a request is locally processed, the following procedures MUST be applied to create the associated answer, in addition to any additional procedures that MAY be discussed in the Diameter application defining the command: - The same Hop-by-Hop identifier in the request is used in the answer. - The local host's identity is encoded in the Origin-Host AVP. - The Destination-Host and Destination-Realm AVPs MUST NOT be present in the answer message. - The Result-Code AVP is added with its value indicating success or failure. - If the Session-Id is present in the request, it MUST be included in the answer. - Any Proxy-Info AVPs in the request MUST be added to the answer message, in the same order they were present in the request. - The 'P' bit is set to the same value as the one in the request. - The same End-to-End identifier in the request is used in the answer. Note that the error messages (see section 7.2) 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. Calhoun et al. expires May 2002 [Page 68]
Internet-Draft November 2001 6.2.2 Relaying and Proxying Answers If the answer is for a request which was proxied or relayed, the agent MUST restore the original value of the Diameter header's Hop- by-Hop Identifier field. If the last Proxy-Info AVP in the message is targeted to the local Diameter server, the AVP MUST be removed before the answer is forwarded. If a relay or proxy agent receives an answer with a Result-Code AVP indicating a failure, it MUST NOT modify the contents of the AVP. Any additional local errors detected SHOULD be logged, but not reflected in the Result-Code AVP. If the agent receives an answer message with a Result-Code AVP indicating success, and it wishes to modify the AVP to indicate an error, it MUST modify the Result-Code AVP to contain the appropriate error in the message destined towards the access device as well as include the Error-Reporting-Host AVP and it MUST issue an STR on behalf of the access device. The agent MUST then send the answer to the host which it received the original request from. 6.3 Origin-Host AVP The Origin-Host AVP (AVP Code 264) is of type DiameterIdentity, and MUST be present in all Diameter messages. This AVP identifies the endpoint which originated the Diameter message. Relay agents MUST NOT modify this AVP. The value of the Origin-Host AVP is guaranteed to be unique within a single host. Note that the Origin-Host AVP may resolve to more than one address as the Diameter peer may support more than one address. 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 UTF8String. 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 Calhoun et al. expires May 2002 [Page 69]
Internet-Draft November 2001 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 UTF8String, and contains the realm the message is to be routed to. The Destination- Realm AVP MUST NOT be present in Answer messages. Diameter Clients insert the realm portion of the User-Name AVP. Diameter servers initiating a request message use the value of the Origin-Realm AVP from a previous message received from the intended target host (unless it is known a priori). When present, the Destination-Realm AVP is used to perform message routing decisions. Request messages whose ABNF does not list the Destination-Realm AVP as a mandatory AVP are inherently non-routable messages. This AVP SHOULD be placed as close to the Diameter header as possible. 6.7 Routing AVPs The AVPs defined in this section are Diameter AVPs used for routing purposes. These AVPs change as Diameter messages are processed by agents, and therefore MUST NOT be protected using the Diameter CMS Security application [11]. 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 Calhoun et al. expires May 2002 [Page 70]
Internet-Draft November 2001 the Origin-Host of the Capabilities Exchange message. 6.7.2 Proxy-Info AVP The Proxy-Info AVP (AVP Code 284) is of type Grouped. The Grouped Data field has the following ABNF grammar: Proxy-Info ::= < AVP Header: 284 > { Proxy-Host } { Proxy-State } * [ AVP ] 6.7.3 Proxy-Host AVP The Proxy-Host AVP (AVP Code 280) is of type DiameterIdentity. This AVP contains the identity of the host that added the Proxy-Info AVP. 6.7.4 Proxy-State AVP The Proxy-State AVP (AVP Code 33) is of type OctetString, and contains state local information, and MUST be treated as opaque data. 6.8 Auth-Application-Id AVP The Auth-Application-Id AVP (AVP Code 258) is of type Unsigned32 and is used in order to advertise support of the Authentication and Authorization portion of an application (see Section 2.5). The Auth- Application-Id MUST also be present in all Authentication and/or Authorization messages that are defined in a separate Diameter specification and have an Application ID assigned. This AVP SHOULD be placed as close to the Diameter header as possible. 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 2.5). The Acct-Application-Id MUST also be present in all Accounting messages that are defined in a separate Diameter specification and have an Application ID assigned. This AVP SHOULD be placed as close to the Diameter header as Calhoun et al. expires May 2002 [Page 71]
Internet-Draft November 2001 possible. 6.10 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. Either the Auth-Application-Id or the Acct- Application-Id AVP MAY be present. Both AVPs MAY be present if they both contain the same value. This AVP MUST also be present in all vendor-specific commands defined in the vendor-specific application. This AVP SHOULD be placed as close to the Diameter header as possible. AVP Format <Vendor-Specific-Application-Id> ::= < AVP Header: 260 > 1* [ Vendor-Id ] 0*1{ Auth-Application-Id } 0*1{ Acct-Application-Id } 6.11 Redirect-Host AVP The Redirect-Host AVP (AVP Code 292) is of type DiameterIdentity. 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 the host identified in this AVP. The server contained in the Redirect-Host SHOULD be used for all messages pertaining to this session. 6.12 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 dictates how the routing entry resulting from the Redirect-Host is to be used. The following values are supported: DONT_CACHE 0 The host specified in the Redirect-Host AVP should not be Calhoun et al. expires May 2002 [Page 72]
Internet-Draft November 2001 cached. This is the default value. ALL_SESSION 1 All messages within the same session, as defined by the same value of the Session-ID AVP MAY be sent to the host specified in the Redirect-Host AVP. ALL_REALM 2 All messages destined for the realm requested MAY be sent to the host specified in the Redirect-Host AVP. REALM_AND_APPLICATION 3 All messages for the application requested to the realm specified MAY be sent to the host specified in the Redirect- Host AVP. ALL_APPLICATION 4 All messages for the application requested MAY be sent to the host specified in the Redirect-Host AVP. ALL_HOST 5 All messages that would be sent to the host that generated the Redirect-Host MAY be sent to the host specified in the Redirect-Host AVP. 6.13 Redirect-Max-Cache-Time AVP The Redirect-Max-Cache-Time AVP (AVP Code 262) is of type Unsigned32. This AVP MUST be present in answer messages whose 'E' bit is set, the Result-Code AVP is set to DIAMETER_REDIRECT_INDICATION and the Redirect-Host-Usage AVP set to a non-zero value. This AVP contains the maximum number of seconds the peer and route table entries, created as a result of the Redirect-Host, will be cached. Note that once a host created due to a redirect indication is no longer reachable, any associated peer and routing table entries MUST be deleted. 7.0 Error Handling There are two different types of errors in Diameter; protocol and applications. A protocol error is one that occurs at the base protocol level, and MAY require per hop attention (e.g. message routing error). Application errors, on the other hand, are generally occur due to a problem with a function specified in a Diameter application (e.g. user authentication, Missing AVP). Calhoun et al. expires May 2002 [Page 73]
Internet-Draft November 2001 Result-Code AVP values that are used to report protocol errors MUST only be present in answer messages whose 'E' bit is set. When a request message is received that causes a protocol error, an answer message is returned with the 'E' bit set, and the Result-Code AVP is set to the appropriate protocol error value. As the answer is sent back towards the originator of the request, each proxy or relay agent MAY take action on the message. 1. Request +---------+ Link Broken +-------------------------->|Diameter |----///----+ | +---------------------| | v +------+--+ | 2. answer + 'E' set | Relay 2 | +--------+ |Diameter |<-+ (Unable to Forward) +---------+ |Diameter| | | | Home | | Relay 1 |--+ +---------+ | Server | +---------+ | 3. Request |Diameter | +--------+ +-------------------->| | ^ | Relay 3 |-----------+ +---------+ Figure 8: Example of Protocol Error causing answer message Figure 8 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 9: Example of Application Error Answer message Figure 9 provides an example of a Diameter message that caused an application error. When application errors occur, the Diameter entity reporting the error clears the 'R' bit in the Command Flags, and adds the Result-Code AVP with the proper value. Application errors do not require any proxy or relay agent involvement, and therefore the message would be forwarded back to the originator of the request. There are certain Result-Code AVP application errors that require additional AVPs to be present in the answer. In these cases, the Diameter node that sets the Result-Code AVP to indicate the error Calhoun et al. expires May 2002 [Page 74]
Internet-Draft November 2001 MUST add the AVPs. Examples are: - An unrecognized AVP is received with the 'M' bit (Mandatory bit) set, causes an answer to be sent with the Result-Code AVP set to DIAMETER_AVP_UNSUPPORTED, and the Failed-AVP AVP containing the offending AVP. - An AVP that is received with an unrecognized value causes an answer to be returned with the Result-Code AVP set to DIAMETER_INVALID_AVP_VALUE, with the Failed-AVP AVP containing the AVP causing the error. - A command is received with an AVP that is omitted, yet is mandatory according to the command's ABNF. The receiver issues an answer with the Result-Code set to DIAMETER_MISSING_AVP, and creates an AVP with the AVP Code and other fields set to the missing AVP's. The created AVP is then added to the Failed-AVP AVP. The Result-Code AVP contains additional errors conditions, and defines the expected behavior of each. 7.1 Result-Code AVP The Result-Code AVP (AVP Code 268) is of type Unsigned32 and indicates whether a particular request was completed successfully or whether an error occurred. All Diameter answer messages MUST include one Result-Code AVP. A non-successful Result-Code AVP (one containing a non 2xxx value) MUST include the Error-Reporting-Host AVP if the host setting the Result-Code AVP is different from the identity encoded in the Origin-Host AVP. The Result-Code data field contains an IANA-managed 32-bit address space representing errors (see section 11.4). Diameter provides the following classes of errors, all identified by the thousands digit: - 1xxx (Informational) - 2xxx (Success) - 3xxx (Protocol Errors) - 4xxx (Transient Failures) - 5xxx (Permanent Failure) A non-recognize 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 Calhoun et al. expires May 2002 [Page 75]
Internet-Draft November 2001 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 required multiple round trip, 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. DIAMETER_COMMAND_UNSUPPORTED 3001 The Request contained a Command-Code that the receiver did not recognize or support. DIAMETER_UNABLE_TO_DELIVER 3002 This error is given when Diameter can not deliver the message to the destination, either because no host within the realm was available to process the request, or because Destination-Host AVP was given without the associated Destination-Realm AVP. DIAMETER_REALM_NOT_SERVED 3003 The intended realm of the request is not recognized. DIAMETER_TOO_BUSY 3004 When returned, a Diameter node SHOULD attempt to send the message to an alternate peer. This error MUST only be used when a specific server is requested, and it cannot provide the requested service. Calhoun et al. expires May 2002 [Page 76]
Internet-Draft November 2001 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 either set to an invalid combination, or to a value that is inconsistent with the command code's definition. DIAMETER_INVALID_AVP_BITS 3009 A request was received that included an AVP whose flag bits are set to an unrecognized value, or that is inconsistent with the AVP's definition. DIAMETER_UNKNOWN_PEER 3010 A CER was received from an unknown peer. 7.1.4 Transient Failures Errors that fall within the transient failures category are used to inform a peer that the request could not be satisfied at the time it was received, but MAY be able to satisfy the request in the future. DIAMETER_AUTHENTICATION_REJECTED 4001 The authentication process for the user failed, most likely due to an invalid password used by the user. Further attempts MUST only be tried after prompting the user for a new password. DIAMETER_OUT_OF_SPACE 4002 A Diameter node received the accounting request but was unable to commit it to stable storage due to a temporary lack of space. 7.1.5 Permanent Failures Calhoun et al. expires May 2002 [Page 77]
Internet-Draft November 2001 Errors that fall within the permanent failures category are used to inform the peer that the request failed, and should not be attempted again. DIAMETER_AVP_UNSUPPORTED 5001 The peer received a message that contained an AVP that is not recognized or supported and was marked with the Mandatory bit. A Diameter message with this error MUST contain one or more Failed-AVP AVP containing the AVPs that caused the failure. DIAMETER_UNKNOWN_SESSION_ID 5002 The request contained an unknown Session-Id. DIAMETER_AUTHORIZATION_REJECTED 5003 A request was received for which the user could not be authorized. This error could occur if the service requested is not permitted to the user. DIAMETER_INVALID_AVP_VALUE 5004 The request contained an AVP with an invalid value in its data portion. A Diameter message indicating this error MUST include the offending AVPs within a Failed-AVP AVP. DIAMETER_MISSING_AVP 5005 The request did not contain an AVP that is required by the Command Code definition. If this value is sent in the Result- Code AVP, a Failed-AVP AVP SHOULD be included in the message. The Failed-AVP AVP MUST contain an example of the missing AVP complete with the Vendor-Id if applicable. The value field of the missing AVP should be of correct minimum length and contain zeroes. DIAMETER_RESOURCES_EXCEEDED 5006 A request was received that cannot be authorized because the user has already expended allowed resources. An example of this error condition is a user that is restricted to one dial-up PPP port, attempts to establish a second PPP connection. DIAMETER_CONTRADICTING_AVPS 5007 The Home Diameter server has detected AVPs in the request that contradicted each other, and is not willing to provide service to the user. One or more Failed-AVP AVPs MUST be present, containing the AVPs that contradicted each other. DIAMETER_AVP_NOT_ALLOWED 5008 A message was received with an AVP that MUST NOT be present. The Failed-AVP AVP MUST be included and contain a copy of the offending AVP. Calhoun et al. expires May 2002 [Page 78]
Internet-Draft November 2001 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_UNSUPPORTED_TRANSFORM 5010 A message was received that included an CMS-Data AVP [11] that made use of an unsupported transform. DIAMETER_NO_COMMON_APPLICATION 5011 This error is returned when a CER message is received, and there are no common applications supported between the peer. DIAMETER_UNSUPPORTED_VERSION 5012 This error is returned when a request was received, whose version number is unsupported. DIAMETER_UNABLE_TO_COMPLY 5013 This error is returned when a request is rejected for unspecified reasons. DIAMETER_INVALID_BIT_IN_HEADER 5014 This error is returned when an unrecognized bit in the Diameter header is set to one (1). DIAMETER_INVALID_AVP_LENGTH 5015 The request contained an AVP with an invalid length. A Diameter message indicating this error MUST include the offending AVPs within a Failed-AVP AVP. DIAMETER_INVALID_MESSAGE_LENGTH 5016 This error is returned when a request is received with an invalid message length. DIAMETER_INVALID_AVP_BIT_COMBO 5017 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. 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 Calhoun et al. expires May 2002 [Page 79]
Internet-Draft November 2001 that a message with the 'E' bit set is still subjected to the processing rules defined in section 6.2. When set, the answer message will not conform to the ABNF specification for the command, and will instead conform to the following ABNF: Message Format <answer-message> ::= < Diameter Header: code, ERR [PXY] > 0*1< Session-Id > { Origin-Host } { Origin-Realm } { Result-Code } [ Origin-State-Id ] [ Error-Reporting-Host ] [ Proxy-Info ] * [ AVP ] Note that the code used in the header is the same that the one found in the request message, but with the 'R' bit cleared and the 'E' bit set. The 'P' bit in the header is set to the same value as the one found in the request message. 7.3 Error-Message AVP The Error-Message AVP (AVP Code 281) is of type UTF8String. It MAY accompany a Result-Code AVP as a human readable error message. The Error-Message AVP is not intended to be useful in real-time, and SHOULD NOT be expected to be parsed by network entities. 7.4 Error-Reporting-Host AVP The Error-Reporting-Host AVP (AVP Code 294) is of type DiameterIdentity. This AVP contains the identity of the Diameter host that sent the Result-Code AVP to a value other than 2001 (Success), only if the host setting the Result-Code is different from the one encoded in the Origin-Host AVP. This AVP is intended to be used for troubleshooting purposes, and MUST be set when the Result- Code AVP indicates a failure. 7.5 Failed-AVP AVP The Failed-AVP AVP (AVP Code 279) is of type Grouped and provides debugging information in cases where a request is rejected or not fully processed due to erroneous information in a specific AVP. The value of the Result-Code AVP will provide information on the reason Calhoun et al. expires May 2002 [Page 80]
Internet-Draft November 2001 for the Failed-AVP AVP. The possible reasons for this AVP are the presence of an improperly constructed AVP, an unsupported or unrecognized AVP, an invalid AVP value, the omission of a required AVP, the presence of an explicitly excluded AVP (see tables in section 10.0), or the presence of two or more occurrences of an AVP which is restricted to 0, 1, or 0-1 occurrences. A Diameter message MAY contain one Failed-AVP AVP, containing the entire AVP that could not be processed successfully. If the failure reason is omission of a required AVP, an AVP with the missing AVP code, the missing vendor id, and a zero filled payload of the minimum required length for the omitted AVP will be added. AVP Format <Failed-AVP> ::= < AVP Header: 279 > 1* {AVP} 8.0 Diameter User Sessions Diameter can provide two different type of services to applications. The first involves authentication and authorization, and 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 use network resources for a finite amount of time, and it is willing to extend the authorization via a future request, it MUST add the Authorization- Lifetime AVP to the answer message. The Authorization-Lifetime AVP defines the maximum number of seconds a user MAY make use of the resources before another authorization request is expected by the server. The Auth-Grace-Period AVP contains the number of seconds following the expiration of the Authorization-Lifetime, after which the server will release an state information related to the user's session. Note that if payment for services is expected by the serving Calhoun et al. expires May 2002 [Page 81]
Internet-Draft November 2001 realm from the user's home realm, the Authorization-Lifetime AVP, combined with the Auth-Grace-Period AVP, implies the maximum length the session the home realm is willing to be fiscally responsible for. Services provided past the expiration of the Authorization-Lifetime and Auth-Grace-Period AVPs is the responsibility of the access device. Of course, the actual cost of services rendered is clearly outside the scope of the protocol. An access device that does not expect to send a re-authorization or a session termination request to the server MAY include the Auth- Session-State AVP with the value set to NO_STATE_MAINTAINED as a hint to the server. If the server accepts the hint, it agrees that since no session termination message will be received once service to the user is terminated, it cannot maintain state for the session. If the answer message from the server contains a different value in the Auth-Session-State AVP (or the default value if the AVP is absent), the access device MUST follow the server's directives. Note that the value NO_STATE_MAINTAINED MUST NOT be set in subsequent re- authorization requests and answers. The base protocol does not include any authorization request messages, since these are largely application-specific and are defined in a Diameter application document. However, the base protocol does define a set of messages that 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. 8.1 Authorization Session State Machine This section contains a finite state machine, representing the life cycle of Diameter sessions, and MUST be observed by all Diameter implementations that makes 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 IP, NASREQ). There are two different session state machines supported in the Diameter base protocol. The first consists of a session in which the server is maintaining session state, indicated by the value of the Auth-Session-State AVP (or its absence). The second state machine is used when the server does not maintain session state. Calhoun et al. expires May 2002 [Page 82]
Internet-Draft November 2001 When a session is moved to the Idle state, any resources that were allocated for the particular session must be released. Any event not listed in the state machines MUST be considered as an error condition, and an answer, if applicable, MUST be returned to the originator of the message. The following state machine is used when state is maintained on the server: State Event Action New State ------------------------------------------------------------- Idle Client or Device Requests send Pending access service specific auth req Idle Service-specific authorization send Open request received, and successful user is authorized serv. specific answer Idle Service-specific authorization send Idle request received, and failed serv. user is not authorized specific answer Pending Successful Service-specific Grant Open authorization answer Access received with default Auth-Session-State value Pending Successful Service-specific Sent STR Discon authorization answer received but service not provided Pending Error processing successful Sent STR Discon Service-specific authorization answer Pending Failed Service-specific Cleanup Idle authorization answer received Open user or client device send Open requests access to service service specific auth req Open Service-specific authorization send Open request received, and user successful Calhoun et al. expires May 2002 [Page 83]
Internet-Draft November 2001 is authorized serv. specific answer Open Service-specific authorization send Idle request received, and user Failed serv. is not authorized specific answer, Cleanup Open Successful Service-specific Extend Open authorization answer received Answer Open Accounting message sent or process Open received Open Failed Service-specific Discon. Idle authorization answer user/device received. Open Session-Timeout Expires on send STR Discon Access Device Open Home server wants to send ASR Discon terminate the service Open ASR Received send ASA, Discon STR Open Authorization-Lifetime + send STR Discon Auth-Grace-Period expires on access device Open Authorization-Lifetime (and Cleanup Discon Auth-Grace-Period) expires on home server. Open Session-Timeout expires on Cleanup Discon home server Open STR Received Send STA Idle Discon ASA Received Cleanup Idle Discon ASR Received None Discon Discon STR Received Send STA Idle Discon STA Received Discon. Idle Calhoun et al. expires May 2002 [Page 84]
Internet-Draft November 2001 user/device The following state machine is used when state is not maintained on the server: State Event Action New State ------------------------------------------------------------- Idle Client or Device Requests send Pending access service specific auth req Idle Service-specific authorization send serv. Open request received, and specific successfully processed answer Pending Successful Service-specific Grant Open authorization answer Access received with Auth-Session- State set to NO_STATE_MAINTAINED Pending Failed Service-specific Cleanup Idle authorization answer received Open Accounting message sent or process Open received Open Session-Timeout Expires on Discon. Idle Access Device user/device Open Service to user is terminated Discon. Idle user/device 8.2 Accounting Session State Machine For applications that only require accounting services, the following state machine MUST be supported. When a session is moved to the Idle state, any resources that were allocated for the particular session must be released. Any event not listed in the state machines MUST be considered as an error condition, and an answer, if applicable, MUST be returned to the originator of the message. Calhoun et al. expires May 2002 [Page 85]
Internet-Draft November 2001 State Event Action New State ------------------------------------------------------------- Idle Client or device requests send Pending access accounting start req. Idle Accounting start request send Open received, and successfully accounting processed. start answer Pending Successful accounting grant Open start answer received access Open Receive Interim Record send Open accounting answer Open User service terminated send Discon accounting stop req. Open Accounting stop request send Idle received, and successfully accounting processed stop answer Discon Successful accounting discon. Idle stop answer received user/device 8.3 Server-Initiated Re-Auth A Diameter server may initiate a re-authentication and/or re- authorization service for a particular session by issuing a Re-Auth- Request (RAR). For example, for pre-paid services, the Diameter server that originally authorized a session may need some confirmation that the user is still using the services. An access device that receives a RAR message with Session-Id equal to a currently active session MUST initiate a re-auth towards the user, if the service supports this particular feature. Each Diameter application MUST state whether service-initiated re-auth is supported, since some applications do not allow for access devices to prompt the user for re-auth. Calhoun et al. expires May 2002 [Page 86]
Internet-Draft November 2001 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 } { User-Name } { Re-Auth-Request-Type } [ Origin-State-Id ] * [ AVP ] * [ Proxy-Info ] * [ Route-Record ] 8.3.2 Re-Auth-Answer The Re-Auth-Answer (RAA), indicated by the Command-Code set to 258 and the message flags' 'R' bit clear, is sent in response to the RAR. The Result-Code AVP MUST be present, and indicates the disposition of the request. A successful RAA message MUST be followed by an application-specific authentication and/or authorization message. Message Format Calhoun et al. expires May 2002 [Page 87]
Internet-Draft November 2001 <RAR> ::= < Diameter Header: 258, PXY > < Session-Id > { Result-Code } { Origin-Host } { Origin-Realm } { User-Name } [ Origin-State-Id ] [ Error-Message ] [ Error-Reporting-Host ] * [ Failed-AVP ] * [ Redirected-Host ] [ Redirected-Host-Usage ] [ Redirected-Host-Cache-Time ] * [ AVP ] * [ Proxy-Info ] 8.4 Session Termination It is necessary for a Diameter server that authorized a session, for which it is maintaining state, to be notified when that session is no longer active, both for tracking purposes as well as to allow stateful agents to release any resources that they may have provided for the user's session. For sessions whose state is not being maintained, this section is not used. When a user session that required Diameter authorization terminates, the access device that provided the service MUST issue a Session- Termination- Request (STR) message to the Diameter server that authorized the service, to notify it that the session is no longer active. An STR MUST be issued when a user session terminates for any reason, including user logoff, expiration of Session-Timeout, administrative action, termination upon receipt of an Abort-Session- Request (see below), orderly shutdown of the access device, etc. The access device also MUST issue an STR for a session that was authorized but never actually started. This could occur, for example, due to a sudden resource shortage in the access device, or because the access device is unwilling to provide the type of service requested in the authorization, or because the access device does not support a mandatory AVP returned in the authorization, etc. It is also possible that a session that was authorized is never actually started due to action of a proxy. For example, a proxy may modify an authorization answer, converting the result from success to failure, prior to forwarding the message to the access device. 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 Calhoun et al. expires May 2002 [Page 88]
Internet-Draft November 2001 access device has no way of knowing that the session had been authorized. A Diameter server that receives an STR message MUST clean up resources (e.g., session state) associated with the Session-Id specified in the STR, and return a Session-Termination-Answer. A Diameter server also MUST clean up resources when the Session- Timeout expires, or when the Authorization-Lifetime and the Auth- Grace-Period AVPs expires without receipt of a re-authorization request, regardless of whether an STR for that session is received. The access device is not expected to provide service beyond the expiration of these timers; thus, expiration of either of these timers implies that the access device may have unexpectedly shut down. 8.4.1 Session-Termination-Request The Session-Termination-Request (STR), indicated by the Command-Code set to 275 and the Command Flags' 'R' bit set, is sent by the access device to inform the Diameter Server that an authenticated and/or authorized session is being terminated. Message Format <STR> ::= < Diameter Header: 275, REQ, PXY > < Session-Id > { Origin-Host } { Origin-Realm } { Destination-Realm } { Termination-Cause } [ User-Name ] [ Destination-Host ] * [ Class ] [ Origin-State-Id ] * [ AVP ] * [ Proxy-Info ] * [ Route-Record ] 8.4.2 Session-Termination-Answer The Session-Termination-Answer (STA), indicated by the Command- Code set to 275 and the message flags' 'R' bit clear, is sent by the Diameter Server to acknowledge the notification that the session has been terminated. The Result-Code AVP MUST be present, and MAY contain an indication that an error occurred while servicing the STR. Calhoun et al. expires May 2002 [Page 89]
Internet-Draft November 2001 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-Usase ] [ Redirect-Max-Cache-Time ] * [ AVP ] * [ Proxy-Info ] 8.5 Aborting a Session A Diameter server may request that the access device stop providing service for a particular session by issuing an Abort-Session-Request (ASR). For example, the Diameter server that originally authorized the session may be required to cause that session to be stopped for credit or other reasons that were not anticipated when the session was first authorized. Or, an operator may maintain a management server for the purpose of issuing ASRs to administratively remove users from the network. An access device that receives an ASR with Session-ID equal to a currently active session MAY stop the session. Whether the access device stops the session or not is implementation- and/or configuration- dependent. For example, an access device may honor ASRs from certain agents only. In any case, the access device MUST respond with an Abort-Session-Answer, including a Result-Code AVP to indicate what action it took. Note that if the access device does stop the session upon receipt of an ASR, it issues an STR to the authorizing server (which may or may Calhoun et al. expires May 2002 [Page 90]
Internet-Draft November 2001 not be the agent issuing the ASR) just as it would if the session were terminated for any other reason. 8.5.1 Abort-Session-Request The Abort-Session-Request (ASR), indicated by the Command-Code set to 274 and the message flags' 'R' bit set, may be sent by any server to the access device that is providing session service, to request that the session identified by the Session-Id be stopped. Message Format <ASR> ::= < Diameter Header: 274, REQ, PXY > < Session-Id > { Origin-Host } { Origin-Realm } { Destination-Realm } { Destination-Host } [ User-Name ] [ Origin-State-Id ] * [ AVP ] * [ Proxy-Info ] * [ Route-Record ] 8.5.2 Abort-Session-Answer The Abort-Session-Answer (ASA), indicated by the Command-Code set to 274 and the message flags' 'R' bit clear, is sent in response to the ASR. The Result-Code AVP MUST be present, and indicates the disposition of the request. If the session identified by Session-Id in the ASR was successfully terminated, Result-Code is set to DIAMETER_SUCCESS. If the session is not currently active, Result-Code is set to DIAMETER_UNKNOWN_SESSION_ID. If the access device does not stop the session for any other reason, Result-Code is set to DIAMETER_UNABLE_TO_COMPLY. Message Format Calhoun et al. expires May 2002 [Page 91]
Internet-Draft November 2001 <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 ] * [ Redirected-Host ] [ Redirected-Host-Usage ] [ Redirected-Max-Cache-Time ] * [ AVP ] * [ Proxy-Info ] 8.6 Inferring Session Termination from Origin-State-Id Origin-State-Id is used to allow rapid detection of terminated sessions for which no STR would have been issued, due to unanticipated shutdown of an access device. By including Origin-State-Id in CER/CAA messages, an access device allows a next-hop server to determine immediately upon connection whether the device has lost its sessions since the last connection. By including Origin-State-Id in request messages, an access device also allows a server with which it communicates via proxy to make such a determination. However, a server that is not directly connected with the access device will not discover that the access device has been restarted unless and until it receives a new request from the access device. Thus, use of this mechanism across proxies is opportunistic rather than reliable, but useful nonetheless. When a Diameter server receives a Origin-State-Id that is greater than the Origin-State-Id previously received from the same issuer, it may assume that the issuer has lost state since the previous message and that all sessions that were active under the lower Origin-State- Id have been terminated. The Diameter server MAY clean up all session state associated with such lost sessions, and MAY also issues STRs for all such lost sessions that were authorized on upstream servers, to allow session state to be cleaned up globally. 8.7 Auth-Request-Type AVP The Auth-Request-Type AVP (AVP Code 274) is of type Enumerated and is Calhoun et al. expires May 2002 [Page 92]
Internet-Draft November 2001 included in application-specific auth requests to inform the peers whether a user is to be authenticated only, authorized only or both. Note any value other than both MAY cause RADIUS interoperability issues. The following values are defined: AUTHENTICATE_ONLY 1 The request being sent is for authentication only, and MUST contain the relevant application specific authentication AVPs that are needed by the Diameter server to authenticate the user. AUTHORIZE_ONLY 2 The request being sent is for authorization only, and MUST contain the application specific authorization AVPs that are necessary to identify the service being requested/offered. AUTHORIZE_AUTHENTICATE 3 The request contains a request for both authentication and authorization. The request MUST include both the relevant application specific authentication information, and authorization information necessary to identify the service being requested/offered/. 8.8 Session-Id AVP The Session-Id AVP (AVP Code 263) is of type UTF8String and is used to identify a specific session (see section 8.0). All messages pertaining to a specific session MUST include only one Session-Id AVP and the same value MUST be used throughout the life of a session. When present, the Session-Id SHOULD appear immediately following the Diameter Header (see section 3.0). The Session-Id MUST be globally and eternally unique, as it is meant to uniquely identify a user session without reference to any other information, and may be needed to correlate historical authentication information with accounting information. The Session-Id includes a mandatory portion and an implementation-defined portion; a recommended format for the implementation-defined portion is outlined below. The Session-Id MUST begin with the sender's identity encoded in the DiameterIdentity type (see section 4.4). The remainder of the Session-Id MAY be any sequence that the client can guarantee to be eternally unique; however, the following format is recommended, (square brackets [] indicate an optional element): <DiameterIdentity>;<high 32 bits>;<low 32 bits>[;<optional value>] Calhoun et al. expires May 2002 [Page 93]
Internet-Draft November 2001 <high 32 bits> and <low 32 bits> are decimal representations of the high and low 32 bits of a monotonically increasing 64-bit value. The 64-bit value is rendered in two part to simplify formatting by 32-bit processors. At startup, the high 32 bits of the 64-bit value MAY be initialized to the time, and the low 32 bits MAY be initialized to 0. This will for practical purposes eliminate the possibility of overlapping Session-Ids after a reboot, assuming the reboot process takes longer than a second. Alternatively, an implementation MAY keep track of the increasing value in non-volatile memory. <optional value> is implementation specific but may include a modem's device Id, a layer 2 address, timestamp, etc. Example, in which the standard port is used and there is no optional value: aaa://accesspoint7.acme.com;1876543210;523 or accesspoint7.acme.com;1876543210;523 Example, in which a non-standard port is used and there is an optional value: accesspoint7.acme.com:831;1876543210;523;mobile@200.1.1.88 The session Id is created by the Diameter device initiating the session, which in most cases is done by the client. Note that a Session-Id MAY be used for both the authorization and accounting commands of a given application. 8.9 Authorization-Lifetime AVP The Authorization-Lifetime AVP (AVP Code 291) is of type Unsigned32 and contains the maximum number of seconds of service to be provided to the user before the user is to be re-authenticated and/or re- authorized. Great care should be taken when the Authorization- Lifetime value is determined, since a low, non-zero, value could create significant Diameter traffic, which could congest both the network and the agents. A value of zero (0) means that immediate re-auth is necessary by the access device. This is typically used in cases where multiple authentication methods are used, and a successful auth response with this AVP set to one is used to signal that the next authentication method is to be immediately initiated. The absence of this AVP, or a value of all ones (meaning all bits in the 32 bit field are set to one) means no re-auth is expected. If both this AVP and the Session-Timeout AVP are present in a Calhoun et al. expires May 2002 [Page 94]
Internet-Draft November 2001 message, the value of the latter MUST NOT be smaller than the Authorization-Lifetime AVP. An Authorization-Lifetime AVP MAY be present in a re-authorization messages, and contains the number of seconds the user is authorized to receive service from the time the re-auth answer message is received by the access device. This AVP MAY be provided by the client as a hint of the maximum lifetime that it is willing to accept. However, the server MAY return a value that is equal to, or smaller, than the one provided by the client. 8.10 Auth-Grace-Period AVP The Auth-Grace-Period AVP (AVP Code 276) is of type Unsigned32 and contains the number of seconds the Diameter server will wait following the expiration of the Authorization-Lifetime AVP before cleaning up resources for the session. This AVP MAY be provided by the client as a hint of the maximum lifetime that it is willing to accept. However, the server MAY return a value that is equal to, or smaller, than the one provided by the client. 8.11 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 Calhoun et al. expires May 2002 [Page 95]
Internet-Draft November 2001 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. 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) [1] is of type Unsigned32 and contains the maximum number of seconds of service to be provided to the user before termination of the session. When both the Session- Timeout and the Authorization-Lifetime AVPs are present in an answer message, the former MUST be equal to or greater than the value of the latter. A session that terminates on an access device due to the expiration of the Session-Timeout MUST cause an STR to be issued, unless both the access device and the home server had previously agreed that no session termination messages would be sent (see section 8.9). A Session-Timeout AVP MAY be present in a re-authorization messages, and contains the 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) [1] is of type UTF8String, which contains the User-Name, in a format consistent with the NAI specification [8]. Calhoun et al. expires May 2002 [Page 96]
Internet-Draft November 2001 8.15 Termination-Cause AVP The Termination-Cause AVP (AVP Code 295) is of type Enumerated, and is used to indicate the reason why a session was terminated on the access device. The following values are defined: DIAMETER_LOGOUT 1 The user initiated a disconnect DIAMETER_SERVICE_NOT_PROVIDED 2 This value is used when the user disconnected prior to the receipt of the authorization answer message. DIAMETER_BAD_ANSWER 3 This value indicates that the authorization answer received by the access device was not processed successfully. DIAMETER_ADMINISTRATIVE 4 The user was not granted access, or was disconnected, due to administrative reasons, such as the receipt of a Abort-Session- Request message. DIAMETER_LINK_BROKEN 5 The communication to the user was abruptly disconnected. DIAMETER_AUTH_EXPIRED 6 The user's access was terminated since its authorized session time has expired. DIAMETER_USER_MOVED 7 The user is receiving services from another access device. DIAMETER_SESSION_TIMEOUT 8 The user's session has timed out, and service has been terminated. 8.16 Origin-State-Id AVP The Origin-State-Id AVP (AVP Code 278), of type Unsigned32, is a monotonically increasing value that is advanced whenever a Diameter entity restarts with loss of previous state, for example upon reboot. Origin-State-Id MAY be included in any Diameter message, including CER. A Diameter entity issuing this AVP MUST create a higher value for this AVP each time its state is reset. A Diameter entity MAY set Origin-State-Id to the time of startup, or it MAY use an incrementing Calhoun et al. expires May 2002 [Page 97]
Internet-Draft November 2001 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 been lost. By including Origin-State-Id in a message, it allows other Diameter entities to infer that sessions associated with a lower Origin-State-Id are no longer active. If an access device does not intend for such inferences to be made, it MUST either not include Origin-State-Id in any message, or set its value to 0. 8.17 Session-Binding AVP The Session-Binding AVP (AVP Code 270) is of type Unsigned32, and MAY be present in application-specific authorization answer messages. If present, this AVP MAY inform the Diameter client that all future application-specific re-auth messages for this session MUST be sent to the same authorization server. This AVP MAY also specify that a Session-Termination-Request message for this session MUST be sent to the same authorizing server. This field is a bit mask, and the following bits have been defined: RE_AUTH 1 When set, future re-auth messages for this session MUST NOT include the Destination-Host AVP. When cleared, the default value, the Destination-Host AVP MUST be present in all re-auth messages for this session. STR 2 When set, the STR message for this session MUST NOT include the Destination-Host AVP. When cleared, the default value, the Destination-Host AVP MUST be present in the STR message for this session. ACCOUNTING 4 When set, all accounting messages for this session MUST NOT include the Destination-Host AVP. When cleared, the default value, the Destination-Host AVP MUST be present in all accounting messages for this session. Calhoun et al. expires May 2002 [Page 98]
Internet-Draft November 2001 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. TRY_AGAIN 1 If either the re-auth or the STR message delivery fails, resend the failed message without the Destination-Host AVP present. ALLOW_SERVICE 2 If re-auth message delivery fails, assume that re-authorization succeeded. If STR message delivery fails, terminate the session. TRY_AGAIN_ALLOW_SERVICE 3 If either the re-auth or the STR message delivery fails, resend the failed message without the Destination-Host AVP present. If the second delivery fails for re-auth, assume re- authorization succeeded. If the second delivery fails for STR, terminate the session. 8.19 Multi-Round-Time-Out AVP The Multi-Round-Time-Out AVP (AVP Code 272) is of type Unsigned32, and SHOULD be present in application-specific authorization answer messages whose Result-Code AVP is set to DIAMETER_MULTI_ROUND_AUTH. This AVP contains the maximum number of seconds that the access device MUST provide the user in responding to an authentication request. 8.20 Class AVP The Class AVP (AVP Code 25) is of type OctetString and is used to by Calhoun et al. expires May 2002 [Page 99]
Internet-Draft November 2001 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. 9.0 Accounting This accounting protocol is based on a server directed model with capabilities for real-time delivery of accounting information. Several fault resilience methods [40] have been built in to the protocol in order minimize loss of accounting data in various fault situations and under different assumptions about the capabilities of the used devices. 9.1 Server Directed Model The server directed model means that the device generating the accounting data gets information from either the authorization server (if contacted) or the accounting server regarding the way accounting data shall be forwarded. This information includes accounting record timeliness requirements. As discussed in [40], 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. 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 Accounting-Interim-Interval AVP to control the operation of the Diameter peer operating as a client. The Accounting-Interim-Interval AVP, when present, instructs the Diameter node acting as a client to produce accounting records continuously even during a session. The Diameter accounting server MAY override the interim interval by including an Accounting-Interim-Interval AVP in the Accounting-Answer message. When the AVP is present, the latest value received SHOULD be Calhoun et al. expires May 2002 [Page 100]
Internet-Draft November 2001 used in the generation of interim accounting messages. 9.2 Protocol Messages A Diameter node that receives a successful authentication and/or authorization messages from the Home AAA Server, MUST collect accounting information for the session. The Accounting-Request message is used to transmit the accounting information to the Home AAA server, which MUST reply with the Accounting-Answer message to confirm reception. The Accounting-Answer message includes the Result-Code AVP, which MAY indicate that an error was present in the accounting message. A rejected Accounting-Request message SHOULD cause the user's session to be terminated. Each Diameter Accounting protocol message MAY be compressed using IPComp [41] in order to reduce the used network bandwidth, which MAY use IKE [15] to negotiate the compression parameters. 9.3 Application document requirements Each Diameter application (e.g. NASREQ, MobileIP), MUST define their Service-Specific AVPs that MUST be present in the Accounting-Request message in a section entitled "Accounting AVPs". The application MUST assume that the AVPs described in this document will be present in all Accounting messages, so only their respective service-specific AVPs need to be defined in this section. 9.4 Fault Resilience Diameter Base protocol mechanisms are used to overcome small message loss and network faults of temporary nature. Diameter peers acting as clients MUST implement the use of failover to guard against server failures and certain network failures. Diameter peers acting as agents or related off-line processing systems MUST detect duplicate accounting records caused by the sending of same record to several servers and duplication of messages in transit. This detection MUST be based on the inspection of the Session-Id and Accounting-Record-Number AVP pairs. 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 Calhoun et al. expires May 2002 [Page 101]
Internet-Draft November 2001 reception from the Diameter Server has been received. Upon a reboot, the client MUST starting sending the records in the non-volatile memory to the accounting server with appropriate modifications in termination cause, session length, and other relevant information in the records. A further application of this protocol may include AVPs to control how many accounting records may at most be stored in the Diameter client without committing them to the non-volatile memory or transferring them to the Diameter server. The client SHOULD NOT remove the accounting data from any of its memory areas before the correct Accounting-Answer has been received. The client MAY remove oldest, undelivered or yet unacknowledged accounting data if it runs out of resources such as memory. It is an implementation dependent matter for the client to accept new sessions under this condition. 9.5 Accounting Records In all accounting records the Session-Id and User-Name AVPs MUST be present. If strong authentication across agents is required, as described in [11], the CMS-Signed-Data AVP may be used to authenticate the Accounting Data and Service Specific AVPs. It is not typically necessary that the CMS-Signed-Data AVP cover any additional AVPs, but it is permitted as long as the AVPs protected are defined to have their 'P' bit set. Different types of accounting records are sent depending on the actual type of accounted service and the authorization server's directions for interim accounting. If the accounted service is a one- time event, meaning that the start and stop of the event are simultaneous, then the Accounting-Record-Type AVP MUST be present and set to the value EVENT_RECORD. If the accounted service is of a measurable length, then the AVP MUST use the values START_RECORD, STOP_RECORD, and possibly, INTERIM_RECORD. If the authorization server has directed interim accounting to be enabled for the session, but no interim interval was specified, two accounting records MUST be generated for each service of type session. When the initial Accounting-Request is sent 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 a specified interim interval exists, the Diameter client MUST produce additional records between the START_RECORD and STOP_RECORD, Calhoun et al. expires May 2002 [Page 102]
Internet-Draft November 2001 marked INTERIM_RECORD. The production of these records is directed both by Accounting-Interim-Interval as well as any re-authentication or re-authorization of the session. The Diameter client MUST overwrite any previous interim accounting records that are locally stored for delivery, if a new record is being generated for the same session. This ensures that only one pending interim record can exist on an access device for any given session. A particular value of Accounting-Sub-Session-Id MUST appear only in one sequence of accounting records from a DIAMETER client, except for the purposes of retransmission. The one sequence that is sent MUST be either one record with Accounting-Record-Type AVP set to the value EVENT_RECORD, or several records starting with one having the value START_RECORD, followed by zero or more INTERIM_RECORD, and a single STOP_RECORD. A particular Diameter application specification MUST define the type of sequences that MUST be used. 9.6 Correlation of Accounting Records The Diameter protocol's Session-Id AVP, which is globally unique (see section 8.8), is used during the authorization phase to identify a particular session. Services that do not require any authorization still use the Session-Id AVP to identify sessions. However, there are certain applications that require multiple accounting sub-sessions. Such applications would send messages with a constant Session-Id AVP, but a different Accounting-Sub-Session-Id AVP. In these cases, correlation is performed using the Session-Id. It is important to note that receiving a STOP_RECORD with no Accounting-Sub-Session-Id AVP when sub-sessions were originally used in the START_RECORD messages implies that all sub-sessions are terminated. Furthermore, there are certain applications where a user receives service from different access devices (e.g. Mobile IP), each with their own unique Session-Id. In such cases, the Accounting-Multi- Session-Id AVP is used for correlation. During authorization, a server that determines that a request is for an existing session, SHOULD include the Accounting-Multi-Session-Id AVP, which the access device MUST include in all subsequent accounting messages. The Accounting-Multi-Session-Id AVP MAY include the value of the original Session-Id. It's contents are implementation specific, but MUST be globally unique across other Accounting-Multi-Session-Id, and MUST NOT change during the life of a session. A Diameter application document MUST define the exact concept of a Calhoun et al. expires May 2002 [Page 103]
Internet-Draft November 2001 session that is being accounted, and MAY define the concept of a multi-session. For instance, the NASREQ DIAMETER application treats a single PPP connection to a Network Access Server as one session, and a set of Multilink PPP sessions as one multi-session. 9.7 Accounting Command-Codes This section defines new 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. When the Accounting-Request is being submitted to a third party (e.g. settlement service), and includes the CMS-Signed-Data AVP [11], the CMS-Signed-Data AVP MUST be signed by both the local and home Diameter server using the countersignature procedures described in [11]. The AVP listed below SHOULD include service specific accounting AVPs, as described in section 9.3. Message Format <ACR> ::= < Diameter Header: 271, REQ, PXY > < Session-Id > { Acct-Application-Id } { Origin-Host } { Origin-Realm } { Destination-Realm } { Accounting-Record-Type } { Accounting-Record-Number } [ User-Name ] [ Accounting-Sub-Session-Id ] [ Accounting-RADIUS-Session-Id ] [ Accounting-Multi-Session-Id ] [ Accounting-Interim-Interval ] [ Origin-State-Id ] * [ AVP ] * [ Proxy-Info ] * [ Route-Record ] Calhoun et al. expires May 2002 [Page 104]
Internet-Draft November 2001 9.7.2 Accounting-Answer The Accounting-Answer (ACA) command, indicated by the Command-Code field set to 271 and the Command Flags' 'R' bit cleared, is used to acknowledge an Accounting-Request command. The Accounting-Answer command contains the same Session-Id and MAY contains the same Accounting Description and Usage AVPs that were sent in the Accounting-Request command. If the CMS-Data AVP was present in the Accounting-Request, the corresponding ACA message MUST include the CMS-Data AVP signed by the responder to provide strong AVP authentication, which MAY be used for the purposes of repudiation. Only the target Diameter Server, known as the home Diameter Server, SHOULD respond with the Accounting-Answer command. The AVP listed below SHOULD include service specific accounting AVPs, as described in section 9.3. Message Format <ACA> ::= < Diameter Header: 271, PXY > < Session-Id > { Acct-Application-Id } { Result-Code } { Origin-Host } { Origin-Realm } { Accounting-Record-Type } { Accounting-Record-Number } [ User-Name ] [ Accounting-Sub-Session-Id ] [ Accounting-RADIUS-Session-Id ] [ Accounting-Multi-Session-Id ] [ Error-Reporting-Host ] [ Accounting-Interim-Interval ] [ Origin-State-Id ] * [ AVP ] * [ Proxy-Info ] 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 Calhoun et al. expires May 2002 [Page 105]
Internet-Draft November 2001 and contains the type of accounting record being sent. The following values are currently defined for the Accounting-Record-Type AVP: EVENT_RECORD 1 An Accounting Event Record is used to indicate that a one-time event has occurred (meaning that the start and end of the event are simultaneous). This record contains all information relevant to the service, and is the only record of the service. START_RECORD 2 An Accounting Start, Interim, and Stop Records are used to indicate that a service of a measurable length has been given. An Accounting Start Record is used to initiate an accounting session, and contains accounting information that is relevant to the initiation of the session. 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 directed by the Accounting-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 Accounting-Interim-Interval AVP The Accounting-Interim-Interval AVP (AVP Code 482) 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 Accounting-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. Calhoun et al. expires May 2002 [Page 106]
Internet-Draft November 2001 2. The inclusion of the AVP with Value field set to a non-zero value means that INTERIM_RECORD records MUST be produced between the START_RECORD and STOP_RECORD records. The Value field of this AVP is the nominal interval between these records in seconds. The Diameter node that originates the accounting information, known as the client, MUST produce the first INTERIM_RECORD record roughly at the time when this nominal interval has elapsed from the START_RECORD, the next one again as the interval has elapsed once more, and so on until the session ends and a STOP_RECORD record is produced. The client MUST ensure that the interim record production times are randomized so that large accounting message storms are not created either among records or around a common service start time. 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 Accounting-RADIUS-Session-Id AVP The Accounting-RADIUS-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 Accounting-Session-Id attribute. 9.8.5 Accounting-Multi-Session-Id AVP The Accounting-Multi-Session-Id AVP (AVP Code 50) is of type UTF8String, following the format specified in section 8.8. The Accounting-Multi-Session-Id AVP is used to link together multiple related accounting sessions, where each session would have a unique Session-Id, but the same Accounting-Multi-Session-Id AVP. This AVP MAY be returned by the Diameter server in an authorization answer, and MUST be used in all accounting messages for the given session. Calhoun et al. expires May 2002 [Page 107]
Internet-Draft November 2001 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. 10.0 AVP Occurrence Table The following tables presents the AVPs defined in this document, and specifies in which Diameter messages they MAY, or MAY NOT be present. Note that AVPs that can only be present within a Grouped AVP are not represented in this table. The table uses the following symbols: 0 The AVP MUST NOT be present in the message. 0+ Zero or more instances of the AVP MAY be present in the message. 0-1 Zero or one instance of the AVP MAY be present in the message. It is considered an error if there are more than once instance of the AVP. 1 One instance of the AVP MUST be present in the message. 1+ At least one instance of the AVP MUST be present in the message. 10.1 Base Protocol Command AVP Table The table in this section is limited to the non-accounting Command Codes defined in this specification. Calhoun et al. expires May 2002 [Page 108]
Internet-Draft November 2001 +-----------------------------------------------+ | Command-Code | |---+---+---+---+---+---+---+---+---+---+---+---+ Attribute Name |CER|CEA|DPR|DPA|DWR|DWA|RAR|RAA|ASR|ASA|STR|STA| --------------------|---+---+---+---+---+---+---+---+---+---+---+---| Acct-Application-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | Auth-Application-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | Auth-Grace-Period |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | Auth-Request-Type |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | Auth-Session-State |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | Authorization- |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | Lifetime | | | | | | | | | | | | | Class |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0+ |0+ | Destination-Host |0 |0 |0 |0 |0 |0 |1 |0 |1 |0 |0-1|0 | Destination-Realm |0 |0 |0 |0 |0 |0 |1 |0 |1 |0 |1 |0 | Disconnect-Cause |0 |0 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 | Error-Message |0 |0-1|0 |0-1|0 |0-1|0 |0-1|0 |0-1|0 |0-1| Error-Reporting-Host|0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1| Failed-AVP |0 |0+ |0 |0+ |0 |0+ |0 |0+ |0 |0+ |0 |0+ | Firmware-Revision |0-1|0-1|0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | Host-IP-Address |1+ |1+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | Multi-Round-Time-Out|0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | Origin-Host |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 | Origin-Realm |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 | Origin-State-Id |0-1|0-1|0 |0 |0-1|0-1|0-1|0-1|0-1|0-1|0-1|0-1| Product-Name |1 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | Proxy-Info |0 |0 |0 |0 |0 |0 |0+ |0+ |0+ |0+ |0+ |0+ | Redirect-Host |0 |0 |0 |0 |0 |0 |0 |0+ |0 |0+ |0 |0+ | Redirect-Host-Usage |0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1| Redirect-Max-Cache- |0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1| Time | | | | | | | | | | | | | Result-Code |0 |1 |0 |1 |0 |1 |0 |1 |0 |0 |0 |1 | Re-Auth-Request-Type|0 |0 |0 |0 |0 |0 |1 |0 |0 |0 |0 |0 | Route-Record |0 |0 |0 |0 |0 |0 |0+ |0 |0+ |0 |0+ |0 | Session-Binding |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | Session-Id |0 |0 |0 |0 |0 |0 |1 |1 |1 |1 |1 |1 | Session-Server- |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | Failover | | | | | | | | | | | | | Session-Timeout |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | Supported-Vendor-Id |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | Termination-Cause |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |1 |0 | User-Name |0 |0 |0 |0 |0 |0 |1 |1 |1 |1 |1 |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 | | | | | | | | | | | | | --------------------|---+---+---+---+---+---+---+---+---+---+---+---| Calhoun et al. expires May 2002 [Page 109]
Internet-Draft November 2001 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. +-----------+ | Command | | Code | |-----+-----+ Attribute Name | ACR | ACA | ------------------------------|-----+-----+ Accounting-Interim-Interval | 0-1 | 0-1 | Accounting-Multi-Session-Id | 0-1 | 0-1 | Accounting-Record-Number | 1 | 1 | Accounting-Record-Type | 1 | 1 | Accounting-RADIUS-Session-Id | 0-1 | 0-1 | Accounting-Sub-Session-Id | 0-1 | 0-1 | Acct-Application-Id | 1 | 1 | Class | 0+ | 0+ | Destination-Host | 0-1 | 0 | Destination-Realm | 1 | 0 | Error-Reporting-Host | 0 | 0+ | Max-Time-Wait | 0+ | 0 | Origin-Host | 1 | 1 | Origin-Realm | 1 | 1 | Proxy-Info | 0+ | 0+ | Route-Record | 0+ | 0+ | Result-Code | 0 | 1 | Session-Id | 1 | 1 | User-Name | 1 | 1 | ------------------------------|-----+-----+ 11.0 IANA Considerations This document defines a number of assigned numbers to be maintained by the IANA. This section explains the criteria to be used by the IANA to assign additional numbers in each of these lists. The following subsections describe the assignment policy for the namespaces defined elsewhere in this document. 11.1 AVP As defined in section 4.0, the AVP header contains two fields that requires IANA namespace management; the AVP Code and Flags field. 11.1.1 AVP Code Calhoun et al. expires May 2002 [Page 110]
Internet-Draft November 2001 the AVP Code namespace is used to identify attributes. When the Vendor ID value is set to zero (0), IANA will maintain a registry of assigned AVP codes, and in some cases also their values. AVP Codes 0-254 are managed separately as RADIUS Attribute Types [46], while the remaining namespace is available for assignment via Specification Required [12]. Vendor-Specific AVP Codes, where the Vendor-Id field in the AVP header is set to a non-zero value, is for Private Use. This document defines the AVP Codes 257-274, 276-285, 287, 291-297, 480, 482 and 485-486. See section 4.6 for the assignment of the namespace in this specification. 11.1.2 AVP Flags There are 8 bits in the AVP Flags field of the AVP header, defined in section 4.0. This document assigns bit 8 ('V'endor Specific), bit 7 ('M'andatory) and bit 6 ('P'rotected). The remaining bits should only be assigned via a Standards Action [12]. 11.2 Diameter Header As defined in section 3.0, the Diameter header contains two fields that require IANA namespace management; Command Code and Command Flags. 11.2.1 Command Codes The Command Code namespace is used to identify Diameter commands. The values 0-255 are reserved for RADIUS backward compatibility, and are defined as "RADIUS Packet Type Codes" in [46]. The remaining values are available via Standards Action [12]. Vendor-Specific Command Codes, where the Vendor-Id field in the Diameter header is set to a non-zero value, is for Private Use. This document defines the Command Codes 257, 258, 271, 274-275, 280 and 282. See section 3.1 for the assignment of the namespace in this specification. 11.2.2 Command Flags There are eight bits in the Command Flags field of the Diameter Calhoun et al. expires May 2002 [Page 111]
Internet-Draft November 2001 header. This document assigns bit 8 ('R'equest), bit 7 ('P'roxy) and bit 6 ('E'rror). Bits 1 through 5 MUST only be assigned via a Standards Action [12]. 11.3 Application Identifiers As defined in section 2.5, the Application Identifier is used to identify a specific Diameter Application. All values except zero (0) are available for assignment via Standards Action [12]. Vendor-Specific Application Identifiers, encoded in the Vendor- Specific-Application-Id Grouped AVP, with the Vendor-Id AVP set to the vendor's enterprise number, is for Private Use. Note that the Diameter protocol is not intended to be extended for any purpose. Any applications defined MUST ensure that they fit within the existing framework, and that no changes to the base protocol are required. 11.4 Result-Code AVP Values As defined in Section 7.1, the Result-Code AVP (AVP Code 268) defines the values 1001, 2001-2002, 3001-3009, 4001-4002 and 5001-5017. All remaining values are available for assignment via IETF Consensus [12]. 11.5 Accounting-Record-Type AVP Values As defined in Section 9.8.1, the Accounting-Record-Type AVP (AVP Code 480) defines the values 1-4. All remaining values are available for assignment via IETF Consensus [12]. 11.6 Termination-Cause AVP Values As defined in Section 8.15, the Termination-Cause AVP (AVP Code 295) defines the values 1-8. All remaining values are available for assignment via IETF Consensus [12]. 11.7 Redirect-Host-Usage AVP Values As defined in Section 6.12, the Redirect-Host-Usage AVP (AVP Code 261) defines the values 0-5. All remaining values are available for Calhoun et al. expires May 2002 [Page 112]
Internet-Draft November 2001 assignment via IETF Consensus [12]. 11.8 Session-Server-Failover AVP Values As defined in Section 8.18, the Session-Server-Failover AVP (AVP Code 271) defines the values 0-3. All remaining values are available for assignment via IETF Consensus [12]. 11.9 Session-Binding AVP Values As defined in Section 8.17, the Session-Binding AVP (AVP Code 270) defines the bits 1-4. All remaining bits are available for assignment via IETF Consensus [12]. 11.10 Diameter TCP/SCTP Port Numbers An IANA request has been placed for TCP and SCTP port numbers. The IANA has informed the authors that "TBD" should be used in section 2.1 this document, and will be updated by the RFC editor during the RFC publication process. IANA should also replace "TBD" in sections 4.4 and 5.2 with the port number assigned in section 2.1. 11.11 Disconnect-Cause AVP Values As defined in Section 5.4.3, the Disconnect-Cause AVP (AVP Code 273) defines the values 0-2. All remaining values are available for assignment via IETF Consensus [12]. 11.12 Auth-Request-Type AVP Values As defined in Section 8.7, the Auth-Request-Type AVP (AVP Code 274) defines the values 1-3. All remaining values are available for assignment via IETF Consensus [27]. 11.13 Auth-Session-State AVP Values As defined in Section 8.11, the Auth-Session-State AVP (AVP Code 277) defines the values 0-1. All remaining values are available for assignment via IETF Consensus [27]. Calhoun et al. expires May 2002 [Page 113]
Internet-Draft November 2001 11.14 Re-Auth-Request-Type AVP Values As defined in Section 8.12, the Re-Auth-Request-Type AVP (AVP Code 285) defines the values 0-1. All remaining values are available for assignment via IETF Consensus [27]. 12.0 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. Realm Routing Table A Diameter Proxy server routes messages based on the realm portion of a Network Access Identifier (NAI). The server MUST have a table of Realms Names, and the address of the peer to which the message must be forwarded to. The routing table MAY also include a "default route", which is typically used for all messages that cannot be locally processed. Tc timer The Tc timer controls the frequency that transport connection attempts are done to a peer with whom no active transport connection exists. The recommended value is 30 seconds. Td timer The Td timer controls the termination of connections with peer in the SUSPECT state. The recommended value is 5 seconds. Ti timer The Ti timer controls the frequency the watchdog messages are to be sent to idle peers. The recommended value is 30 seconds. Tr timer The Tr timer controls the frequency the watchdog messages are to be sent to peers when there are pending requests, but not messages have been received from the peer. The recommended value is 10 seconds. Tw timer The Tw timer controls the changing of a peer to the SUSPECT Calhoun et al. expires May 2002 [Page 114]
Internet-Draft November 2001 state when no answer is received to a watchdog request. The recommended value is 5 seconds. 13.0 Security Considerations The Diameter base protocol assumes that messages are secured by using either IP Security, or TLS. This security model is acceptable in environments where there are no untrusted third party relay, proxy, or redirect agent. When third party brokers or redirect agents are used, strong application level security SHOULD be required, such as non- repudiation. When the communicating peers do require this level of security either for legal or business purposes, the Diameter application defined in [11] MAY be used. This security model provides AVP-level authentication, and the encryption mechanism is designed such that only the target host has the keying information required to decrypt the information. 14.0 References [1] C. Rigney, A. Rubens, W. Simpson, S. Willens, "Remote Authentica- tion Dial In User Service (RADIUS)", RFC 2865, June 2000. [2] Reynolds, Postel, "Assigned Numbers", RFC 1700, October 1994. [3] Postel, "User Datagram Protocol", RFC 768, August 1980. [4] Rivest, "The MD5 Message-Digest Algorithm", RFC 1321, April 1992. [5] Kaufman, Perlman, Speciner, "Network Security: Private Communica- tions in a Public World", Prentice Hall, March 1995, ISBN 0-13-061466-1. [6] Krawczyk, Bellare, Canetti, "HMAC: Keyed-Hashing for Message Authentication", RFC 2104, January 1997. [7] P. Calhoun, W. Bulley, A. Rubens, J. Haag, "Diameter NASREQ Appli- cation", draft-ietf-aaa-diameter-nasreq-08.txt, IETF work in progress, November 2001. [8] Aboba, Beadles "The Network Access Identifier." RFC 2486. January 1999. Calhoun et al. expires May 2002 [Page 115]
Internet-Draft November 2001 [10] P. Calhoun, C. Perkins, "Diameter Mobile IP Application", draft- ietf-aaa-diameter-mobileip-08.txt, IETF work in progress, November 2001. [11] P. Calhoun, W. Bulley, S. Farrell, "Diameter CMS Security applica- tion", draft-ietf-aaa-diameter-cms-sec-03.txt, IETF work in progress, November 2001. [12] Narten, Alvestrand,"Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 2434, October 1998 [13] S. Bradner, "Key words for use in RFCs to Indicate Requirement Lev- els", BCP 14, RFC 2119, March 1997. [14] Myers, Ankney, Malpani, Galperin, Adams, "X.509 Internet Public Key Infrastructure Online Certificate Status Protocol (OCSP)", RFC 2560, June 1999. [15] D. Harkins, D. Carrel, "The Internet Key Exchange (IKE)", RFC 2409, November 1998. [16] Hinden, Deering, "IP Version 6 Addressing Architecture", RFC 2373, July 1998. [17] ISI, "Internet Protocol", RFC 791, September 1981. [18] Mills, "Simple Network Time Protocol (SNTP) Version 4 for IPv4, IPv6 and OSI, RFC 2030, October 1996. [19] Housley, Ford, Polk, Solo, "Internet X.509 Public Key Infrastruc- ture Certificate and CRL Profile", RFC 2459, January 1999. [20] B. Aboba, G. Zorn, "Criteria for Evaluating Roaming Protocols", RFC 2477, January 1999. [21] M. Beadles, D. Mitton, "Criteria for Evaluating Network Access Server Protocols", RFC 3169, September 2001. [22] T. Hiller and al, "CDMA2000 Wireless Data Requirements for AAA", RFC 3141, June 2001. [23] S. Glass, S. Jacobs, C. Perkins, "Mobile IP Authentication, Autho- rization, and Accounting Requirements". RFC 2977. October 2000. [24] F. Yergeau, "UTF-8, a transformation format of ISO 10646", RFC 2279, January 1998. Calhoun et al. expires May 2002 [Page 116]
Internet-Draft November 2001 [25] L. J. Blunk, J. R. Vollbrecht, "PPP Extensible Authentication Pro- tocol (EAP)." RFC 2284, March 1998. [26] R. Stewart et al., "Stream Control Transmission Protocol". RFC 2960. October 2000. [27] Postel, J. "Transmission Control Protocol", RFC 793, January 1981. [28] E. Guttman, C. Perkins, J. Veizades, M. Day. "Service Location Pro- tocol, Version 2", RFC 2165, June 1999. [29] T. Berners-Lee, R. Fielding, U.C. Irvine, L. Masinter, "Uniform Resource Identifiers (URI): Generic Syntax". RFC 2396, August 1998. [30] Institute of Electrical and Electronics Engineers, "IEEE Standard for Binary Floating-Point Arithmetic", ANSI/IEEE Standard 754-1985, August 1985. [31] D. Crocker, P. Overell, "Augmented BNF for Syntax Specifications: ABNF", RFC 2234, November 1997. [32] E. Guttman, C. Perkins, J. Kempf, "Service Templates and Service: Schemes", RFC 2609, June 1999. [33] A. Gulbrandsen, P. Vixie, L. Esibov, "A DNS RR for specifying the location of services (DNS SRV)", RFC 2782, February 2000. [34] D. Eastlake, "Domain Name System Security Extensions", RFC 2535, March 1999. [35] D. Eastlake, "DNS Security Operational Considerations", RFC 2541, March 1999. [36] D. Eastlake, "DNS Request and Transaction Signatures ( SIG(0)s )", RFC 2931, September 2000. [37] S. Kent, R. Atkinson, "Security Architecture for the Internet Pro- tocol", RFC 2401, November 1998. [38] T. Dierks, C. Allen, "The TLS Protocol Version 1.0", RFC 2246, Jan- uary 1999. [39] "The Communications of the ACM" Vol.33, No.6 (June 1990), pp. 677-680. [40] B. Aboba, J. Arkko, D. Harrington. "Introduction to Accounting Man- agement", RFC 2975, October 2000. Calhoun et al. expires May 2002 [Page 117]
Internet-Draft November 2001 [41] A. Shacham, R. Monsour, R. Pereira, M. Thomas, "IP Payload Compres- sion Protocol (IPComp)", RFC 2393, December 1998. [42] W. Simpson, "The Point-to-Point Protocol (PPP)", RFC 1661, STD 51, July 1994. [43] B. Aboba, J. Lu, J. Alsop, J. Ding, W. Wang, "Review of Roaming Implementations", RFC 2194, September 1997. [44] B. Aboba, J. Vollbrecht, "Proxy Chaining and Policy Implementation in Roaming", RFC 2607, June 1999. [45] C. Perkins, Editor. IP Mobility Support. RFC 2002, October 1996. [46] IANA, "RADIUS Types", http://www.isi.edu/in-notes/iana/assign- ments/radius-types [47] IANA, "Number assignment", http://www.iana.org [48] P. V. Mockapetris, "Domain names - implementation and specifica- tion," RFC 1035, November 1987. [49] K. Nichols, S. Blake, F. Baker, D. Black, "Definition of the Dif- ferentiated Services Field (DS Field) in the IPv4 and IPv6 Head- ers," RFC 2474, December 1998. [50] J. Heinanen, F. Baker, W. Weiss, J. Wroclawski, "Assured Forwarding PHB Group," RFC 2597, June 1999. [51] V. Jacobson, K. Nichols, K. Poduri, "An Expedited Forwarding PHB", RFC 2598, June 1999. [52] B. Aboba, J. Wood, "Authentication, Authorization and Accounting (AAA) Transport Profile", draft-ietf-aaa-transport-04.txt, IETF Work in Progress, June 2001. 15.0 Acknowledgements The authors would like to thank Nenad Trifunovic, Tony Johansson and Pankaj Patel for their participation in the pre-IETF Document Reading Party. Allison Mankin's, Jonathan Wood and Bernard Aboba's assis- tance was invaluable in working out transport issues, and similarly with Steven Bellovin's help 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, Calhoun et al. expires May 2002 [Page 118]
Internet-Draft November 2001 Mark Jones and Dave Spence. Jacques Caron provided many great com- ments 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: William Bulley, Stephen Farrell, David Frascone, Daniel C. Fox, Lol Grant, Ignacio Goyret, Nancy Greene, Peter Heitman, Fredrik Johans- son, Mark Jones, Martin Julien, 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. 16.0 Authors' Addresses Questions about this memo can be directed to: Pat R. Calhoun Black Storm Networks 250 Cambridge Avenue, Suite 200 Palo Alto, California, 94306 USA Phone: +1 650-617-2932 Fax: +1 650-786-6445 E-mail: pcalhoun@diameter.org Haseeb Akhtar Wireless Technology Labs Nortel Networks 2221 Lakeside Blvd. Richardson, TX 75082-4399 USA Phone: +1 972-684-8850 E-Mail: haseeb@nortelnetworks.com Calhoun et al. expires May 2002 [Page 119]
Internet-Draft November 2001 Jari Arkko Oy LM Ericsson Ab 02420 Jorvas Finland Phone: +358 40 5079256 E-Mail: Jari.Arkko@ericsson.com Erik Guttman Solaris Advanced Development Sun Microsystems, Inc. Eichhoelzelstr. 7 74915 Waibstadt Germany Phone: +49-7263-911-701 E-mail: erik.guttman@germany.sun.com Allan C. Rubens Tut Systems, Inc. 220 E. Huron, Suite 260 Ann Arbor, MI 48104 USA Phone: +1 734-995-1697 E-Mail: arubens@tutsys.com Glen Zorn Cisco Systems, Inc. 500 108th Avenue N.E., Suite 500 Bellevue, WA 98004 USA Phone: +1 425 438 8218 17.0 Full Copyright Statement Copyright (C) The Internet Society (2001). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are Calhoun et al. expires May 2002 [Page 120]
Internet-Draft November 2001 included on all such copies and derivative works. However, this docu- ment itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of develop- ing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The lim- ited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DIS- CLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 18.0 Expiration Date This memo is filed as <draft-ietf-aaa-diameter-08.txt> and expires in May 2002. Calhoun et al. expires May 2002 [Page 121]
Internet-Draft November 2001 Appendix A. Diameter Service Template The following service template describes the attributes used by Diam- eter servers to advertise themselves. This simplifies the process of selecting an appropriate server to communicate with. A Diameter client can request specific Diameter servers based on characteristics of the Diameter service desired (for example, an AAA server to use for accounting.) Name of submitter: "Erik Guttman" <Erik.Guttman@sun.com> Language of service template: en Security Considerations: Diameter clients and servers use various cryptographic mechanisms to protect communication integrity, confidentiality as well as perform end-point authentication. It would thus be difficult if not impossible for an attacker to advertise itself using SLPv2 and pose as a legitimate Diameter peer without proper preconfigured secrets or cryptographic keys. Still, as Diameter services are vital for network operation it is important to use SLPv2 authenti- cation to prevent an attacker from modifying or eliminating ser- vice advertisements for legitimate Diameter servers. Template text: -------------------------template begins here----------------------- template-type=service:diameter template-version=0.0 template-description= The Diameter protocol is defined by draft-ietf-aaa-diameter-07.txt template-url-syntax= url-path= ; The Diameter URL format is described in section 4.4. ; Example: 'aaa://aaa.example.com:1812;transport=tcp Calhoun et al. expires May 2002 [Page 122]
Internet-Draft November 2001 supported-auth-applications= string L M # This attribute lists the Diameter applications supported by the # AAA implementation. The applications currently defined are: # Application Name Defined by # ---------------- ----------------------------------- # NASREQ draft-ietf-aaa-diameter-nasreq-07.txt # MobileIP draft-ietf-aaa-diameter-mobileip-07.txt # CMS Security draft-ietf-aaa-diameter-cms-sec-02.txt # # Notes: # . Diameter implementations support one or more applications. # . Additional applications may be defined in the future. # An updated service template will be created at that time. # NASREQ,MobileIP,CMS Security supported-acct-applications= string L M # This attribute lists the Diameter applications supported by the # AAA implementation. The applications currently defined are: # Application Name Defined by # ---------------- ----------------------------------- # NASREQ draft-ietf-aaa-diameter-nasreq-07.txt # MobileIP draft-ietf-aaa-diameter-mobileip-07.txt # CMS Security draft-ietf-aaa-diameter-cms-sec-02.txt # # Notes: # . Diameter implementations support one or more applications. # . Additional applications may be defined in the future. # An updated service template will be created at that time. # NASREQ,MobileIP,CMS Security supported-transports= string L M SCTP # This attribute lists the supported transports that the Diameter # implementation accepts. Note that a compliant Diameter # implementation MUST support SCTP, though it MAY support other # transports, too. SCTP,TCP -------------------------template ends here----------------------- Calhoun et al. expires May 2002 [Page 123]
