AAA Working Group Pat R. Calhoun Internet-Draft Sun Microsystems, Inc. Category: Standards Track Haseeb Akhtar <draft-ietf-aaa-diameter-02.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. April 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. Abstract The Diameter base protocol is intended to provide a AAA framework for Calhoun et al. expires September 2001 [Page 1]
Internet-Draft April 2001 Mobile-IP, NASREQ and ROAMOPS. This draft specifies the message format, transport, error reporting and security services to be used by all Diameter extensions and MUST be supported by all Diameter implementations. Calhoun et al. expires September 2001 [Page 2]
Internet-Draft April 2001 Table of Contents 1.0 Introduction 1.1 Diameter Protocol 1.2 Requirements language 1.3 Terminology 2.0 Protocol Overview 2.1 Transport 2.2 Securing Diameter Messages 2.3 Diameter Extensions 2.4 Diameter Server Discovery 3.0 Diameter Header 3.1 Command Code Definitions 3.2 Command Code ABNF specification 3.3 Diameter Command Naming Conventions 3.3.1 Request/Answer 3.3.2 Query/Response 3.3.3 Indication 4.0 Diameter AVPs 4.1 AVP Header 4.2 Optional Header Elements 4.3 AVP Data Formats 4.4 Grouped AVP Values 4.4.1 Example AVP with a Grouped Data type 4.5 Diameter Base Protocol AVPs 5.0 Message Forwarding 5.1 Origin-FQDN AVP 5.2 Origin-Realm AVP 5.3 Destination-FQDN AVP 6.0 Capabilities Negotiation 6.1 Device-Reboot-Ind (DRI) Command 6.1.1 Vendor-Id AVP 6.1.2 Firmware-Revision AVP 6.1.3 Extension-Id AVP 6.1.4 Host-IP-Address AVP 6.1.5 Supported-Vendor-Id AVP 6.1.6 Product-Name AVP 7.0 Transport Failure Detection 7.1 Device-Watchdog-Request 7.2 Device-Watchdog-Answer 7.3 Failover/Failback Procedures 8.0 Peer State Machine 8.1 States 8.2 Events 8.3 Actions 8.4 The Election Process 9.0 Per-Hop Error Signaling 9.1 Device-Status-Ind Calhoun et al. expires September 2001 [Page 3]
Internet-Draft April 2001 9.1.1 DSI-Event AVP 9.1.1.1 Informational Events 9.1.1.2 Redirect Event 9.1.1.3 Transient Failure Events 9.1.1.4 Permanent Failure Events 10.0 End-to-End Error Signaling 10.1 Message-Reject-Ind (MRI) Command 10.1.1 Failed-AVP AVP 10.1.2 Failed-Command-Code AVP 10.1.3 Failed-Vendor-Id AVP 10.2 Result-Code AVP 10.2.1 Informational 10.2.2 Success 10.2.3 Redirect Notification 10.2.4 Transient Failures 10.2.5 Permanent Failures 10.3 Error-Message AVP 10.4 Error-Reporting-FQDN AVP 11.0 "User" Sessions 11.1 Session State Machine 11.2 Session-Id AVP 11.3 Authorization-Lifetime AVP 11.4 Session-Timeout AVP 11.5 User-Name AVP 11.6 Max-Wait-Time AVP 11.7 Original-Session-Id AVP 11.8 Session Termination 11.8.1 Session-Termination-Ind 11.8.2 Session-Termination-Request 11.8.3 Session-Termination-Answer 12.0 Message Routing 12.1 Realm-Based Message Routing 12.1.1 Realm-Based Routing Table 12.2 Proxy and Redirect Server handling of requests 12.2.1 Proxy and Redirect Server handling of requests 12.3 Redirect Server 12.3.1 Redirect-Host AVP 12.3.2 Redirect-Host-Address AVP 12.3.3 Redirect-Host-Port AVP 12.4 Proxy Server 12.4.1 Proxying Requests 12.4.2 Proxying Responses 12.4.3 Route-Record AVP 12.4.4 Proxy-State AVP 12.4.5 Proxy-Address AVP 12.4.6 Proxy-Info AVP 12.4.7 Destination-Realm AVP 12.5 Applying Local Policies Calhoun et al. expires September 2001 [Page 4]
Internet-Draft April 2001 12.6 Hiding Network Topology 12.7 Loop Detection 13.0 Accounting 13.1 Authorization-Server Directed Model 13.2 Protocol Messages 13.3 Extension document requirements 13.4 Fault Resilience 13.5 Session Records 14.0 Accounting Command-Codes 14.1 Accounting-Request (ACR) Command 14.2 Accounting-Answer (ACA) Command 14.3 Accounting-Status-Ind (ASI) Command 14.4 Accounting-Poll-Ind (API) Command 15.0 Accounting AVPs 15.1 Accounting-Record-Type AVP 15.2 Accounting-Interim-Interval AVP 15.3 Accounting-Record-Number AVP 15.4 Accounting-State AVP 15.5 Accounting-Session-Id AVP 16.0 AVP Occurrence Table 16.1 Base Protocol Command AVP Table 16.2 Accounting AVP Table 17.0 IANA Considerations 17.1 AVP Attributes 17.2 Command Code AVP Values 17.3 Extension Identifier Values 17.4 Result-Code AVP Values 17.5 Message Header Bits 17.6 AVP Header Bits 17.7 DSI-Event AVP Values 18.0 Open Issues 19.0 Diameter protocol related configurable parameters 20.0 Security Considerations 21.0 References 22.0 Acknowledgements 23.0 Authors' Addresses 24.0 Full Copyright Statement Appendix A. Diameter Service Template Calhoun et al. expires September 2001 [Page 5]
Internet-Draft April 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 September 2001 [Page 6]
Internet-Draft April 2001 ensure that the effort remains focussed 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. - Proxying and Re-directing 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 an application-specific extension, such as Mobile IP [10]. The Diameter protocol was heavily inspired and builds upon the tradition of the RADIUS [1] protocol. See section 2.3. for more information on Diameter extensions. Any node can initiate a request. In that sense, Diameter is a peer to peer protocol. In this document, a Diameter client is the device that Calhoun et al. expires September 2001 [Page 7]
Internet-Draft April 2001 normally initiates a request for authentication and/or authorization of a user. A Diameter server is the device that either forwards the request to another Diameter server (known as a proxy), or one that performs the actual authentication and/or authorization of the user based on some profile. Given that the server MAY send unsolicited messages to clients, it is possible for the server to initiate such messages. An example of an unsolicited message would be for a request that the client issue an accounting update. Diameter services require sequenced in-order reliable delivery of data, with congestion control (receiver windowing). Timely detection of failed or unresponsive peers is also required, allowing for robust operation. TCP is insufficient for this second requirement. Diameter SHOULD be transported over SCTP [26]. 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. 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 authentication, authorization or accounting information. Broker A broker is a business term commonly used in AAA infrastructures. A broker is either a proxy or redirect server, and MAY be operated by roaming consortiums. Calhoun et al. expires September 2001 [Page 8]
Internet-Draft April 2001 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 Server A Diameter server is a device that is not acting as a NAS or FA. Servers can be proxy, redirect, or home servers Downstream Server Diameter Proxy servers identify a downstream server as one that is providing routing services towards the home server for a particular message. Home Domain A Home Domain is the administrative domain with whom the user maintains an account relationship. Home Server A Diameter Home Server is one that authenticates and/or authorizes access for users of a particular realm. The same server MAY also act as a proxy or redirect server for other realms, in which case it is not acting as a Home Server for these realms. Integrity Check Value (ICV) An Integrity Check Value is an unforgeable or secure hash of the message with a shared secret. 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 Domain A local domain is the administrative domain providing services to a user. An administrative domain MAY act as a local domain for certain users, while being a home domain for others. Network Access Identifier The Network Access Identifier, or NAI [3], 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 Server Calhoun et al. expires September 2001 [Page 9]
Internet-Draft April 2001 A proxy server ”ses the realm portion of the NAI to route Diameter messages. Proxy servers are typically used to minimize the number of security relationships that are required between Diameter servers. 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. Redirect Server A Diameter redirect server provides realm to address translation, by returning information necessary for Diameter peers to communicate directly. Redirect servers are different from proxies since they do not participate in the routing of messages between end Diameter nodes. 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 The Diameter protocol is session based. When an authorization request is initially transmitted, it includes a session identifier that is used for the duration of the session. The Session- Identifier AVP contains the identifier and must be globally unique. Session 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. Upstream Server Calhoun et al. expires September 2001 [Page 10]
Internet-Draft April 2001 Diameter Proxy servers identify an upstream server as one that is providing routing services towards the Diameter client. 2.0 Protocol Overview The base Diameter protocol is never used on its own. It is always extended for a particular application. Four extensions to Diameter are defined by companion documents: NASREQ [7], Mobile IP [10], Strong Security [11]. These options are introduced in this document but specified elsewhere. Additional extensions to Diameter may be defined in the future (see Section 17.3). The base Diameter protocol concerns itself with capabilities negotiation, and 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 peers. Communication between Diameter peers begins with one peer sending a message to another Diameter peer. The set of AVPs included in the message is determined by a particular application of or extension to Diameter. We will refer to this as the Diameter extension. One AVP 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 11.0 for more information). The communicating party may accept the request, or reject it by returning a response 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 extension 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 extension/application of Diameter. Exchanges of messages are either request/reply oriented, or in some special cases, do not require replies. All such messages that do not require replies have names ending with '-Ind' (short for Indication). The Diameter base protocol provides the Authorization-Lifetime AVP, which MAY be used by extensions to specify the duration of a specific authorized session. Calhoun et al. expires September 2001 [Page 11]
Internet-Draft April 2001 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 April 2001). Diameter clients [9] MUST support TCP, but are warned that future versions of this specification may mandate SCTP support. Diameter servers MUST support both TCP and SCTP. A Diameter node MAY send packets from any source port, but MUST be prepared to receive packets on port TBD. When a request is received, the source and destionation ports in the reply are reversed. Note that the source and destination addresses used in request and replies MAY any of a peer's valid IP addresses. A given Diameter process SHOULD use the same port number to send all messages to aid in identifying which process sent a given message. More than one Diameter process MAY exist within a single host, so the sender's port number is needed to discriminate them. When no transport connection exists with a peer, an attempt to connect SHOULD be periodically attempted. The recommended connection interval is 30 seconds. 2.2 Securing Diameter Messages All Diameter messages MUST be secured between peers, and both SSL [38] and IP Security [37] are supported. Network Access Servers (NASes) and Foreign Agents, commonly referred to as clients, MUST support IP Security, while servers MUST support both SSL and IP Security. The communication between a client and server MUST use IP Security, while communication between servers MUST use SSL. All hosts running the Diameter protocol MUST have the necessary security policies to ensure that unauthenticated Diameter packets are not processed. 2.3 Diameter Extensions As previously mentioned, the Diameter base protocol does not operate on its own, but requires appplication-specific extensions, commonly referred to as Diameter extensions. A Diameter extension is a specification that defines one or more Diameter Command-Codes, the expected AVPs in an ABNF [31] grammar (see section 3.2), and MAY also define new AVPs. If the Diameter extension has any accounting requirements, it MUST also specify the AVPs that are to be present in Calhoun et al. expires September 2001 [Page 12]
Internet-Draft April 2001 the Diameter Accounting messages (see section 13.3). Every Diameter Extension specification MUST have an IANA assigned Extension-Id value (see section 6.1.3). This Extension-Id is advertised during the capabilities exchange phase (see section 6.0). Advertising support of a particular extension implies that the sender support all of the Command Codes, and the AVPs specified in the associated ABNF, described in the specification. An implementation MAY add arbitrary AVPs to any command defined in an extension, including vendor-specific AVPs. However, such AVPs MUST NOT have the M(andatory) bit set. An implementation that adds AVPs not specified in a command's ABNF, and sets the AVP's M(andatory) bit MUST NOT advertise support of the extension. An implementation MAY support both a proprietary version of an extension by requesting an IANA extension identifier (see section 17.3), while supporting the original extension. During the capabilities exchange, a Diameter node could know whether it should send the prorietary version, or the standards one, by inspecting the extensions advertised by the peer. 2.4 Diameter Server Discovery Allowing for dynamic Diameter server discovery will make it possible for simpler and more robust deployment of AAA services. In order to promote interoperable implementations of Diameter server discovery, the following mechanisms are described. These are based on existing IETF standards. There are two cases where Diameter server discovery may be performed. The first is when a Diameter client needs to discover a first-hop Diameter server. The second case is when a Diameter server needs to discover another server - 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 server locations. These will be 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. Calhoun et al. expires September 2001 [Page 13]
Internet-Draft April 2001 SLPv2 will allow Diameter implementations to discover the location of Diameter servers in the local site, as well as their characteristics. Diameter servers with specific capabilities (say support for the Accounting extension) 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 domain. The Diameter implementation has to know in advance which domain to look for an Diameter server in. This could be deduced, for example, from the 'realm' in a NAI that an Diameter implementation needed to perform an Diameter operation on. 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 server. [34, 35, 36] 3.0 Diameter Header A summary of the Diameter header format is shown below. The fields are transmitted in network byte order. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |r r r r r r r r r r E I R| Ver | Message Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Hop-by-Hop Identifier | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | End-to-End Identifier | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Command-Code | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Vendor-ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | AVPs ... +-+-+-+-+-+-+-+-+-+-+-+-+- Flags The Message Flags field is thirteen bits. The following bits are assigned: r(eserved) MUST be zero - this flag bit is reserved for future use. Calhoun et al. expires September 2001 [Page 14]
Internet-Draft April 2001 E(xpected Reply) - The message solicits a response. I(nterrogation) - The message is a Query or a Reply. R(esponse) - The message is a response to another message. These flags MUST be set depending on the command code used in a Diameter message. This enables the type of message to be interpreted, even if the specific command code is not recognized. Command Type Flags Set Indication - - - Request E - - Answer - - R Query E I - Reply - I R A Diameter node MUST NOT set these flags in any other combination. A Diameter node receiving a message in which these flags are not set appropriately MAY reject the message for this reason, but SHOULD log the event for diagnosis. Version This Version field MUST be set to 1 to indicate Diameter Version 1. Message Length The Message Length field is two octets and indicates the length of the Diameter message including the header fields. Hop-by-Hop Identifier The Hop-by-Hop Identifier field is four octets, and aids in matching requests and replies. The sender MUST ensure that the Hop-by-Hop identifier in a request (*-Request or *-Query) or indication (*-Ind) message is locally unique (to the sender) at any given time, and MAY attempt to ensure that the number is unique across reboots. The sender of a response (*-Answer or *- Response) 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. End-to-End Identifier Unlike the Hop-by-Hop Identifier, the End-to-End Identifier is used by servers to detect duplicate messages, and proxies MUST NOT modify this field. The sender of a request, query, indication, answer or response message MUST insert a locally unique value in this field. The combination of the Session-Id AVP and this field is used to detect duplicates. Calhoun et al. expires September 2001 [Page 15]
Internet-Draft April 2001 Command-Code The Command-Code field is four octets, and is used in order to communicate the command associated with the message. The 32-bit address space is managed by IANA (see section 17.2). Vendor-ID 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). 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 Every Diameter message MUST contain a value 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 -------------------------------------------------------- Accounting-Answer ACA 272 14.2 Accounting-Poll-Ind API 273 14.4 Accounting-Request ACR 271 14.1 Accounting-Status-Ind ASI 279 14.3 Device-Reboot-Ind DRI 257 6.1 Device-Status-Ind DSI 282 9.1 Device-Watchdog-Req DWR 280 7.1 Device-Watchdog-Answer DWA 281 7.2 Message-Reject-Ind MRI 259 10.1 Session-Termination-Ind STI 274 11.8.1 Session-Termination- STR 275 11.8.2 Request Session-Termination- STA 276 11.8.3 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, MAY and MUST NOT be present. The following format is used in the definition: Calhoun et al. expires September 2001 [Page 16]
Internet-Draft April 2001 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] header = "<Diameter-Header:" command-id ">" 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 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 = diameter-name ; The avp-spec has to be an AVP Name, defined ; in the base or extended Diameter ; specifications. avp-name = avp-spec | "AVP" Calhoun et al. expires September 2001 [Page 17]
Internet-Draft April 2001 ; 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-Command ::= < Diameter-Header: 9999999 > { User-Name } * { Origin-FQDN } * [ AVP ] 3.3 Diameter Command Naming Conventions The following conventions are required for the naming of Diameter messages. Diameter commands typically start with an object name, and end with one of the following verbs: 3.3.1 Request/Answer Request is used when the command is asking the peer to do something for it, for example, authorize a user, or terminate a session. The Answer MUST contain either a positive or negative result code, telling the requester whether or not the request successfully occurred. Other information can also be returned in the Answer. For example, AA-Request asks the peer device to authorize and/or authenticate a user in order to set up a session. The request may fail, thus the answer may be positive or negative. 3.3.2 Query/Response Query is used when the command is asking for information that it expects the peer to have. An example would be querying for current configuration information, or querying for information on resources or sessions in use. The Response usually contains a positive result code and the information, or a negative result code with the reason for not completing the query. For example, Resource-Query requests the peer device to return specific information about one or more resources. The answer is returned in a Resource-Response. 3.3.3 Indication Calhoun et al. expires September 2001 [Page 18]
Internet-Draft April 2001 Indication is used either when the node wishes to inform the peer that an event occured, or is requesting that a particular function be performed, but is not expecting a response. The transport level acknowledgement is used to ensure that the message was reliably delivered. 4.0 Diameter AVPs Diameter AVPs carry specific authentication, accounting and authorization information, security information as well as configuration details for the request and reply. Some AVPs MAY be listed more than once. The effect of 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | AVP Length | Reserved |P|r|V|r|M| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Vendor-ID (opt) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data ... +-+-+-+-+-+-+-+-+ AVP Code The AVP Code identifies the attribute uniquely. The first 256 AVP numbers 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 17.1). AVP Length The AVP Length field is two octets, and indicates the length of Calhoun et al. expires September 2001 [Page 19]
Internet-Draft April 2001 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. AVP Flags The AVP Flags field informs the Diameter host how each attribute must be handled. Note that subsequent Diameter extensions MAY define bits to be used within the AVP Header, and an unrecognized bit should be considered an error. The 'r' and the reserved bits are unused and should be set to 0 and ignored on receipt, while 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 is received by a Home server or NAS with the 'M' bit enabled and the receiver does not support the AVP, the message MUST be rejected. If such an AVP is received by a Proxy or Redirect Server, the message MUST be forwarded to its logical destination, and MUST NOT be rejected. It is the responsibility of the originator of a message that is rejected for this purpose to correct the error. AVPs without the 'M' bit enabled are informational only and a receiver that receives a message with such an AVP that is not supported MAY simply ignore the AVP. The 'V' bit, known as the Vendor-Specific bit, indicates whether the optional Vendor-ID field is present in the AVP header. When set the AVP Code belongs to the specific vendor code address space. 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. 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 Diameter extension 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 extensions, nor with Calhoun et al. expires September 2001 [Page 20]
Internet-Draft April 2001 future IETF extensions. A vendor ID value of zero (0) corresponds to the IETF adopted AVP values, as managed by the IANA. Since the absence of the vendor ID field implies that the AVP in question is not vendor specific, implementations SHOULD not use the zero (0) vendor ID. 4.3 AVP Data Formats The Data field is zero or more octets and contains information specific to the Attribute. The format and length of the Data field is determined by the AVP Code and AVP Length fields. The format of the Data field MAY be one of the following data types. The interpretation of the values depends on the specification of the AVP. For example, an OctetString may be used to transmit human readable string data and Unsigned32 may be used to transmit a time value. Conventions for these common interpretations are described below. OctetString The data contains arbitrary data of variable length. Unless otherwise noted, the AVP Length field MUST be set to at least 9 (13 if the 'V' bit is enabled). Data used to transmit (human readable) character string data uses the UTF-8 [24] character set and is NOT NULL-terminated. The minimum Length field MUST be 9, but can be set to any value up to 65504 bytes. AVP Values of this type that do not align on a 32-bit boundary MUST have the necessary padding. Address 32 bit (IPv4) [17] or 128 bit (IPv6) [16] address, most significant octet first. The format of the address (IPv4 or IPv6) is determined by the length. If the attribute value is an IPv4 address, the AVP Length field MUST be 12 (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. Integer32 32 bit signed value, in network byte order. The AVP Length field MUST be set to 12 (16 if the 'V' bit is enabled). Integer64 64 bit signed value, in network byte order. The AVP Length field MUST be set to 16 (20 if the 'V' bit is enabled). Unsigned32 Calhoun et al. expires September 2001 [Page 21]
Internet-Draft April 2001 32 bit unsigned value, in network byte order. The AVP Length field MUST be set to 12 (16 if the 'V' bit is enabled). Unsigned32 values used to transmit time data contains the four most significant octets returned from NTP [18], in network byte order. Unsigned64 32 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). Float128 This represents floating point values of quadruple precision as described by [30]. The 128 bit value is transmitted in network byte order. The AVP Length field MUST be set to 24 (28 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 Grouped AVP Values The Diameter protocol allows AVP values of type 'Grouped.' This implies that the Data field is actually a well defined 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. Grouped type AVP specifications include an ABNF grammar [31] specifying the required sequence of AVPs. Grouped AVP values MUST be in the specified sequence and MUST NOT include other AVP values Calhoun et al. expires September 2001 [Page 22]
Internet-Draft April 2001 besides those specified by the Grouped AVP grammar. 4.4.1 Example AVP with a Grouped Data type The Example AVP (AVP Code 999999) is of type Grouped and is used to clarify how Grouped AVP values work. The Grouped Data field has the following ABNF grammar: example-avp-val = Origin-FQDN Host-IP-Address Origin-FQDN = ; See Section 5.1 Host-IP-Address = ; See Section 6.1.4 An Example AVP with the Grouped Data Origin-FQDN = "example.com", Host-IP-Address = "10.10.10.10" would be encoded as follows: 0 1 2 3 4 5 6 7 +-------+-------+-------+-------+-------+-------+-------+-------+ 0 | Example AVP Header (AVP Code = 999999), Length = 40 | +-------+-------+-------+-------+-------+-------+-------+-------+ 8 | Origin-FQDN AVP Header (AVP Code = 264), Length = 19 | +-------+-------+-------+-------+-------+-------+-------+-------+ 16 | 'e' | 'x' | 'a' | 'm' | 'p' | 'l' | 'e' | '.' | +-------+-------+-------+-------+-------+-------+-------+-------+ 24 | 'c' | 'o' | 'm' |Padding| Host-IP-Addr AVP Header | +-------+-------+-------+-------+-------+-------+-------+-------+ 32 | (AVP Code = 257), Length = 12 | 0x0a | 0x0a | 0x0a | 0x0a | +-------+-------+-------+-------+-------+-------+-------+-------+ 4.5 Diameter Base Protocol AVPs The following table describes the Diameter AVPs defined in the base protocol, their AVP Code values, types, possible flag values and whether the AVP MAY be encrypted. Calhoun et al. expires September 2001 [Page 23]
Internet-Draft April 2001 +---------------------+ | AVP Flag rules | |----+-----+----+-----|----+ AVP Section | | |SHLD| MUST|MAY | Attribute Name Code Defined Data Type |MUST| MAY | NOT| NOT|Encr| -----------------------------------------|----+-----+----+-----|----| Accounting- 482 15.2 Unsigned32 | M | P | | V | Y | Interim-Interval | | | | | | Accounting- 485 15.3 Unsigned32 | M | P | | V | Y | Record-Number | | | | | | Accounting- 480 15.1 Unsigned32 | M | P | | V | Y | Record-Type | | | | | | Accounting- 44 15.5 OctetString| M | P | | V | Y | Session-Id | | | | | | Accounting-State 486 15.4 Unsigned32 | M | P | | V | Y | Authorization- 291 11.3 Unsigned32 | | | | | N | Lifetime | | | | | | Destination-FQDN 293 5.3 OctetString| | | | | Y | Destination- 283 12.4.7 OctetString| M | | | V | N | Realm | | | | | | DSI-Event 297 9.1.1 Unsigned32 | M | | | | N | Error-Message 281 10.3 OctetString| | | | | N | Error-Reporting- 294 10.4 OctetString| | | | | Y | FQDN | | | | | | Extension-Id 258 6.1.3 Integer32 | M | | | | Y | Failed-AVP 279 10.1.1 OctetString| | | | | Y | Failed-Command- 270 10.1.2 Unsigned32 | | | | | Y | Code | | | | | | Failed-Vendor-Id 262 10.1.3 Unsigned32 | | | | | Y | Firmware- 267 6.1.2 Unsigned32 | | | | V,M | Y | Revision | | | | | | Host-IP-Address 257 6.1.4 Address | M | | | V | N | Max-Wait-Time 295 11.6 Unsigned32 | M | | | V | N | Origin-FQDN 264 5.1 OctetString| M | | | V | N | Origin-Realm 296 5.2 OctetString| M | | | V | N | Original- 261 11.7 OctetString| M | | | V | N | Session-Id | | | | | | Product-Name 269 6.1.6 OctetString| | | | | N | Proxy-Address 280 12.4.5 Address | M | | | V | N | Proxy-Info 284 12.4.6 OctetString| M | | | V | N | Proxy-State 33 12.4.4 Grouped | M | | | V | N | Redirect-Host 292 12.3.1 Grouped | | | | | Y | Redirect-Host- 278 12.3.2 Address | | | | | Y | Address | | | | | | Redirect-Host- 277 12.3.3 Unsigned32 | | | | | Y | Port | | | | | | Result-Code 268 10.2 Unsigned32 | M | | | | N | -----------------------------------------|----+-----+----+-----|----| Calhoun et al. expires September 2001 [Page 24]
Internet-Draft April 2001 +---------------------+ | AVP Flag rules | |----+-----+----+-----|----+ AVP Section | | |SHLD| MUST|MAY | Attribute Name Code Defined Data Type |MUST| MAY | NOT| NOT|Encr| -----------------------------------------|----+-----+----+-----|----| Route-Record 282 12.4.3 OctetString| M | | | V | N | Session-Id 263 11.2 OctetString| M | | | | Y | Session-Timeout 27 11.4 Unsigned32 | | | | | Y | Supported- 265 6.1.5 Unsigned32 | | | | | N | Vendor-Id | | | | | | User-Name 1 11.5 OctetString| | | | | Y | Vendor-Id 266 6.1.1 Unsigned32 | | | | V,M | Y | -----------------------------------------|----+-----+----+-----|----| 5.0 Message Forwarding All Diameter messages MUST include the Origin-FQDN and Origin-Realm AVPs. These AVPs are used to identify the source of the message. When responding to a request or query message, the Origin-FQDN and Origin-Realm AVPs are replaced with the local node's information. When a Diameter entity receives a Diameter message of type Request, Query or Indication that includes a Destination-FQDN AVP, and the host specified in the AVP can be contacted directly, the message MUST be forwarded to the host in question. The Destination-FQDN AVP is used when the destination of the message is fixed, such as: - 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. NAS), such as the Session-Termination-Ind message, which is used to request that a particular user's session be terminated. Proxies receiving messages that contain the Destination-FQDN AVP MUST verify whether they are able to forward Diameter messages to the host specified in the AVP, and if so, MUST forward the message to the host in question. Otherwise, the message routing procedures described in section 12.0 MUST be followed. This section defines the Diameter AVPs that MUST be added in all messages originated by a Diameter node (including nodes creating Calhoun et al. expires September 2001 [Page 25]
Internet-Draft April 2001 Response and Answer messages). 5.1 Origin-FQDN AVP The Origin-FQDN AVP (AVP Code 264) is of type OctetString, encoded in the UTF-8 [24] format. This AVP identifies the endpoint which originated the Diameter message, i.e. the NAS, home server, or broker. Proxy servers do not modify this AVP. All Diameter messages MUST include the Origin-FQDN AVP, which contains the host name of the originator of the Diameter message and MUST follow the Fully Qualified Domain Name naming conventions. Note that the Origin-FQDN AVP may resolve to more than one address as the Diameter peer may support more than one address. 5.2 Origin-Realm AVP The Origin-Realm AVP (AVP Code 296) is of type OctetString, encoded in the UTF-8 [24] format. This AVP contains the Realm of the originator of any Diameter message. 5.3 Destination-FQDN AVP The Destination-FQDN AVP (AVP Code 293) is of type OctetString, encoded in the UTF-8 [24] format, and contains the Fully Qualified Domain Name (FQDN) of the intended recipient of the message. This AVP MUST be present in all unsolicited server initiated messages. The value of the Destination-FQDN AVP is set to the value of the Origin- FQDN AVP found in a message from the intended target host. 6.0 Capabilities Exchange When two Diameter peers establish a transport connection, they MUST send the Device-Reboot-Ind message. This message has two purposes. First it allows a peer's identity to be discovered, and allows for capabilities exchange, such as the supported protocol version number, and the locally supported extensions. The receiver uses the extensions advertised in order to determine whether it SHOULD send certain application-specific Diameter commands. A Diameter node MUST retain the supported extensions in order to ensure that unrecognized commands and/or AVPs are not sent to a peer. Calhoun et al. expires September 2001 [Page 26]
Internet-Draft April 2001 The Device-Reboot-Ind message MUST NOT be proxied, or redirected. Since the DRI cannot be proxied, it is still possible that a upstream proxy receives a message for which it has no available peers to handle the extension that corresponds to the Command-Code. In such instances, the Device-Status-Ind message is used (see Section 9.1) to inform the downstream to take action. With the exception of the Device-Reboot-Ind message, a message of type Request, Query or Indication that includes the Extension-Id AVP, or a message with an extension-specific command code, MAY only be forwarded to a host that has explicitely advertised support for the extension (or has advertised the Wildcard Extension). 6.1 Device-Reboot-Ind (DRI) Command The Device-Reboot-Ind (DRI), indicated by the Command-Code set to 257, is sent to inform a peer that a reboot has, or will, occur. When Diameter is run over SCTP [26], which allows for connections to span multiple interfaces, hence multiple IP addresses, the Device- Reboot-Ind message MUST contain one Host-IP-Address AVP for each potential IP address that MAY be locally used when transmitting Diameter messages. If a Diameter node receives a DRI message that results in an error, a Message-Reject-Ind message MUST be returned. Message Format <Device-Reboot-Ind> ::= < Diameter Header: 257 > { Origin-FQDN } { Origin-Realm } 1* { Host-IP-Address } { Vendor-Id } { Product-Name } * { Supported-Vendor-Id } * { Extension-Id } [ Firmware-Revision ] * [ AVP ] 6.1.1 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. Calhoun et al. expires September 2001 [Page 27]
Internet-Draft April 2001 In combination with the Supported-Vendor-Id AVP (section 6.1.5), 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 6.1.6) and the Firmware-Revision (section 6.1.2) AVPs MAY provide very useful debugging information. A Vendor-Id value of zero in the DRI 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. 6.1.2 Firmware-Revision AVP The Firmware-Revision AVP (AVP Code 267) is of type Unsigned32 and is used to inform a Diameter peer of the firmware revision of the issuing device. For devices that do not have a firmware revision (general purpose computers running Diameter software modules, for instance), the revision of the Diameter software module may be reported instead. 6.1.3 Extension-Id AVP The Extension-Id AVP (AVP Code 258) is of type Unsigned32 and is used in order to identify a specific Diameter extension. This AVP is used in the Device-Reboot-Ind message in order to inform the peer what extensions are locally supported. The Extension-Id MUST also be present in all messages that are defined in a separate Diameter specification and have an Extension ID assigned. Each Diameter extension draft MUST have an IANA assigned extension Identifier (see section 17.3). The base protocol does not require an Extension-Id since its support is mandatory. There MAY be more than one Extension-Id AVP within a Diameter Device-Reboot-Ind message. The following values are recognized: NASREQ 1 [7] Strong Security 2 [11] Resource Management 3 [29] Mobile-IP 4 [10] Wildcard Extension 0xffffffff Servers acting as Redirect or Proxy servers (see Section 12.0) MAY wish to either advertise all supported extensions, or the wildcard extension. The receiver of a wildcard extension MUST assume that the Calhoun et al. expires September 2001 [Page 28]
Internet-Draft April 2001 sender supports all extensions. Proxy servers are responsible for finding a downstream server that supports the extension of a particular message. If none can be found, a DSI message is returned with the DSI-Event AVP set to DIAMETER_UNABLE_TO_DELIVER. 6.1.4 Host-IP-Address AVP The Host-IP-Address AVP (AVP Code 257) is of type Address and is used to inform a Diameter peer of the sender's IP address. All source addresses that a Diameter node expects to use with SCTP [26] MUST be advertised in the Device-Reboot-Ind message by including a Host-IP- Address AVP for each address. This AVP MUST ONLY be used in the Device-Reboot-Ind message. 6.1.5 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 Device-Reboot-Ind message in order to inform the peer that the sender supports a subset of the vendor-specific commands and/or attributes defined by the vendor identified in this AVP. 6.1.6 Product-Name AVP The Product-Name AVP (AVP Code 269) is of type OctetString, encoded in the UTF-8 [25] format, and contains the vendor assigned name for the product. The Product-Name AVP SHOULD remain constant across firmware revisions for the same product. 7.0 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 servers, resulting in unnecessary delays, and will provide better failover performance. In order to pro-actively detect such failures, the Diameter protocol defines the Device-Watchdog-Request message, which is sent to an inactive peer. A peer is considered inactive if no messages were sent or received from the peer within the current watchdog interval period Calhoun et al. expires September 2001 [Page 29]
Internet-Draft April 2001 (see Section 19.0), and no request or query messages are pending with the peer. For implementations that have access to the Retransmission Time-Out (RTO) value of the underlying transport connection, a DWR SHOULD be sent once per RTO of that connection, plus the watchdog interval period, with a jiterring of +/- 50%. If the DWR is unanswered, the time until the next DWR is sent MUST be recalculated after exponentially backing off the RTO portion. When the value of the DWR's current watchdog interval period reaches the maximum watchdog interval (Secton 19.0), backoff is not continued, and the peer is marked as failed. DWR messages continue to be sent (jittered) at the final interval for detection for failover. The current watchdog interval is returned to its starting point when a DWA is received or the peer resumes activity. Implementations that do not have access to the RTO SHOULD perform an Round Trip Time (RTT) measurement for a given peer when a Device- Watchdog-Answer message is received for a non-backed off DWR. The fixed RTO base should be replaced by RTT-Multiplier (Section 19.0) times the measured RTT. An example of the backoff sequence, excluding jitter, would be: 30+RTO , 30+2*RTO , 30+4*RTO , 30+8*RTO, 60, 60, 60 Note that exponential backoff MUST be performed before the maximum is reached. 7.1 Device-Watchdog-Request The Device-Watchdog-Request (DWR), indicated by the Command-Code set to 280, is sent to a peer when no traffic has been exchanged between two peers as defined in Section 7.0, and no requests are pending with the peer. Message Format <Device-Watchdog-Request> ::= < Diameter Header: 280 > { Origin-FQDN } { Origin-Realm } 7.2 Device-Watchdog-Answer The Device-Watchdog-Answer (DWA), indicated by the Command-Code set to 281, is sent as a response to the Device-Watchdog-Request message. Calhoun et al. expires September 2001 [Page 30]
Internet-Draft April 2001 A receiver of the DWA SHOULD perform RTT calculation in the event that the transport RTO information is not available. Message Format <Device-Watchdog-Answer> ::= < Diameter Header: 281 > { Result-Code } { Origin-FQDN } { Origin-Realm } 7.3 Failover/Failback Procedures In the event that a transport failure is detected with a peer, it is necessary for all pending request, query and indication messages to be forwarded to an alternate server, 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 a response is received, the message is removed from the queue. The Hop-by-Hop Identifier field MAY be used to match the corresponding response with the queued request. When a transport failure is detected, all messages in the queue are sent to an alternate server, if possible. An example of a case where it is not possible for 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-FQDN AVP). Such an error requires that the server return an DSI with the DSI-Event AVP set to DIAMETER_UNABLE_TO_DELIVER. It is important to note that multiple identical request or responses MAY be received as a result of a failover. The End-to-End Identifier field in the Diameter header MUST be used to identify duplicate messages. As described in section 2.1, a connection request should be periodically attempted with the failed peer in order to re-establish the transport connection. Once a connection has been successfully established, messages can once again be forwarded to the peer. This is commonly referred to as failback. 8.0 Peer State Machine This section contains a finite state machine, that MUST be observed by all Diameter implementations. Each Diameter node MUST follow the Calhoun et al. expires September 2001 [Page 31]
Internet-Draft April 2001 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. 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. 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 occured. 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 DRI message is always sent on the responder connection immediately after accepting the connection request. The non-elected connection will close down. All subsesquent messages are sent on the elected connection. 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-Rcv-Conn-Req I-Snd-Conn-Ack Wait-R-DRI Wait-Conn-Ack I-Rcv-Conn-Ack I-Snd-DRI Wait-I-DRI I-Rcv-Conn-Nack Cleanup Closed R-Rcv-Conn-Req R-Snd-Conn-Ack Wait-Conn-Ack/ Wait-R-DRI Timeout Error Closed Wait-I-DRI I-Rcv-DRI Process-DRI I-Open R-Rcv-Conn-Req R-Snd-Conn-Ack Wait-R-DRI/ Elect Calhoun et al. expires September 2001 [Page 32]
Internet-Draft April 2001 I-Peer-Disc I-Disc Closed Timeout Error Closed Wait-Conn-Ack/ I-Rcv-Conn-Ack I-Snd-DRI Wait-R-DRI/ Wait-R-DRI Elect I-Rcv-Conn-Nack Cleanup Wait-R-DRI R-Rcv-DRI Process-DRI Wait-Conn-Ack/ Elect Timeout Error Closed Wait-R-DRI/ R-Rcv-DRI Process-DRI, Wait-Returns Elect Elect I-Peer-Disc I-Disc Wait-R-DRI Timeout Error Closed Wait-Conn-Ack/ I-Rcv-Conn-Ack I-Snd-DRI,Elect Wait-Returns Elect I-Rcv-Conn-Nack R-Snd-DRI R-Open R-Peer-Disc R-Disc Wait-Conn-Ack-2 Timeout Error Closed Wait-Returns Win-Election I-Disc,R-Snd-DRI R-Open I-Peer-Disc I-Disc,R-Snd-DRI R-Open I-Rcv-DRI R-Disc I-Open R-Peer-Disc R-Disc Wait-I-DRI-2 Timeout Error Closed Wait-Conn-Ack-2 I-Rcv-Conn-Ack I-Snd-DRI Wait-I-DRI-2 I-Rcv-Conn-Nack Cleanup Closed R-Rcv-Conn-Req R-Snd-Conn-Nack Wait-Conn-Ack-2 Timeout Error Closed Wait-I-DRI-2 I-Rcv-DRI Process-DRI I-Open I-Peer-Disc I-Disc Closed R-Rcv-Conn-Req R-Snd-Conn-Nack Wait-I-DRI-2 Timeout Error Closed Wait-R-DRI R-Rcv-DRI R-Snd-DRI R-Open Timeout Error Closed R-Open Send-Message R-Snd-Non-DRI R-Open R-Rcv-Non-DRI Process R-Open R-WatchDog-Timer R-Snd-DWR R-Open R-Rcv-DWA Process-DWA R-Open Stop R-Snd-Disc Closed R-Peer-Disc R-Disc Closed R-Rcv-DRI Error Closed I-Open Send-Message I-Snd-Non-DRI R-Open Calhoun et al. expires September 2001 [Page 33]
Internet-Draft April 2001 I-Rcv-Non-DRI Process I-Open R-WatchDog-Timer R-Snd-DWR R-Open R-Rcv-DWA Process-DWA R-Open Stop I-Disc Closed I-Peer-Disc I-Disc Closed I-Rcv-DRI Error Closed R-Rcv-Conn-Req R-Snd-Conn-Nack I-Open 8.1 States Following is a more detailed description of each automaton state. Closed A peer is initially in the closed state, and no transport connection exists with the peer. Wait-Conn-Ack A transport connection has been initiated with the peer, and an acknowledgement is pending. Wait-I-DRI The local Diameter node is waiting for the peer to issue a DRI. Wait-Conn-Ack/Wait-R-DRI A transport connection indication from the peer was received, while a transport connection has already been locally initiated. Wait-R-DRI/Elect Two transport connections have been established with the peer, and a DRI is pending on the responder connection. Wait-Conn-Ack/Elect A transport connection exists on the responder connection, while an acknowlegement has yet to be received on the initiator connection. Wait-Returns Multiple transport connections caused an election to occur. Wait-Conn-Ack-2 While an acknowledgement to a locally initiated transport connection hasn't been received, an election has failed and the initiator connection will be used between the peers. Wait-I-DRI-2 Following an election, the initiator connection won, and a DRI has yet to be received by the peer. Calhoun et al. expires September 2001 [Page 34]
Internet-Draft April 2001 Wait-R-DRI A transport connection indication has been received from the peer, and a DRI has yet to be received by the peer. R-Open The responder connection will be used to communicate with the peer. I-Open The initiator connection will be used to communicate with the peer. 8.2 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 signalled that a connection should be initiated with the peer. Rcv-Conn-Req A transport connection indication from the peer has been received. Rcv-Conn-Ack A positive acknowlegement was received to a locally initiated transport connection. Rcv-Conn-Nack A negative acknowledgement was received to a locally initiated transport connection. Timeout An application-defined timer has expired while waiting for some event. Rcv-DRI A DRI message from the peer was received. Peer-Disc A disconnection indication from the peer was received. Win-Election An election was held, and the local node was the winner. Send-Message A Non-DRI message is to be sent. Rcv-Non-DRI A Non-DRI message was received. WatchDog-Timer The Watchdog timer expired, indicating that a DWR message is to be sent to the peer. Calhoun et al. expires September 2001 [Page 35]
Internet-Draft April 2001 Rcv-DWA A DWA message was received. Stop The Diameter application has signalled that a connection should be terminated (e.g., on system shutdown). 8.3 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. Snd-Conn-Ack an acknowledgement is sent in response to a connect request, confirming that the transport layer connection is open. Snd-Conn-Nack A negative acknowledgement is sent in response to a connect request, indicating that the request was refused. Snd-DRI A DRI 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-DRI A received DRI is processed. Disc The transport layer connection is disconnected, and local resources are freed. Elect An election occurs (see Section 8.4 for more information). Snd-Non-DRI A non-DRI message is sent. Snd-DWR A DWR message is sent. Process-DWA The DWA message is serviced. Calhoun et al. expires September 2001 [Page 36]
Internet-Draft April 2001 Process A non-DRI Diameter message is serviced. 8.4 The Election Process The election is performed on the responder. The responder compares the Origin-FQDN received in the DRI sent by its peer with its own Origin-FQDN (which it may or may not have actually sent). The transport layer connection with the higher value of Origin-FQDN is the one that survives. 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. 9.0 Per-Hop Error Signaling There are many instances where error conditions occur on a Diameter node, that needs to be signalled to the downstream server, and not necessarily to the Diameter client. Examples of such error conditions are inability to forward a message to a particular domain, etc. In these cases, returning the error back to the Diameter client will only cause delay, and perhaps confusion in roaming networks. Therefore, when such errors occur, it is necessary for the error to be handled by the downstream next hop, and some local action be taken to rectify the problem, such as forwarding to a different next hop. Request +--------+ Link Broken +-------------------------->|Diameter|----///----+ | +---------------------| | v +-----+---+ | DSI | Server | +--------+ |Diameter |<-+ (Unable to Forward) +--------+ |Diameter| |Client or| | | | Server |--+ +--------+ | Server | +---------+ | Request |Diameter| +--------+ +-------------------->| | ^ | Server |-----------+ +--------+ Figure 1 - Example of Per-Hop Error Condition 9.1 Device-Status-Ind The Device-Status-Ind (DSI), indicated by the Command-Code set to 282, is sent to inform a peer that an event has occurred. Calhoun et al. expires September 2001 [Page 37]
Internet-Draft April 2001 When a Diameter node issues a DSI message downstream, the target peer MUST attempt to rectify the problem, or issue a similar message downstream. The Device-Status-Ind message MUST NOT be proxied, but MAY be forwarded, as long as the Origin-FQDN and Origin-Realm AVPs are replaced to include the local node's identity. The Device-Status-Ind message MUST contain the same Hop-by-Hop Identifier value in the header as the message which motivated sending the DSI. If the Session-Id AVP was present in the original message, the same AVP MUST be present in the DSI. Message Format <Device-Status-Ind> ::= < Diameter Header: 282 > { Origin-FQDN } { Origin-Realm } [ DSI-Event ] * [ AVP ] 9.1.1 DSI-Event AVP The DSI-Event AVP (AVP Code 297) is of type Unsigned32 and indicates that an event occurred which requires attention from a Diameter peer. The DSI-Event contains an IANA-managed 32-bit address space representing events (see section 17.7). Diameter provides four different classes of event notification, all identified by the thousands digit: - 1xxx (Informational Events) - 3xxx (Redirect Notification) - 4xxx (Transient Failure Events) - 5xxx (Permanent Failure Events) A non-recognize class (one whose first digit is not defined in this section) MUST be handled as a permanent failure. 9.1.1.1 Informational Events Events that fall within the Informational category are used to inform a peer that a request cannot be immediately satisfied, and a further response will be issued in the near future. DIAMETER_STILL_WORKING 1001 A request's Max-Wait-Time has expired, and the request is still being serviced. This event MAY be sent prior to the Max-Wait- Time expiration, to inform the peer that the request is not Calhoun et al. expires September 2001 [Page 38]
Internet-Draft April 2001 expected to be serviced in the alloted time, but the request is not being abandoned. It is important to note that receiving this event will result in another Diameter message being received with the same Hop-by-Hop and End-to-End identifiers. 9.1.1.2 Redirect Event Errors that fall within the Redirect Notification category are used to inform a peer that the request cannot be satisfied locally and should instead be forwarded to another server. DIAMETER_REDIRECT_INDICATION 3001 A proxy or redirect server 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. 9.1.1.3 Transient Failure Events 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 if the error is corrected. DIAMETER_UNSUPPORTED_TRANSFORM 4001 A message was received that included an CMS-Data AVP [11] that made use of an unsupported transform. 9.1.1.4 Permanent Failure Events Errors that fall within the permanent failures category are used to inform the peer that the request failed, and cannot be satified by the originator of the Device-Status-Ind. The receiver of a DSI message with the DSI-Event set to a value that falls within this event class SHOULD forward the message to an alternate peer, if one is available. DIAMETER_INVALID_RECORD_ROUTE 5001 The last Route-Record AVP in the message is not set to the identity of the sender of the message. See Section 12.0 for more information. DIAMETER_COMMAND_UNSUPPORTED 5002 The Request contained a Command-Code that the receiver did not recognize or support. The Device-Status-Ind message MUST also Calhoun et al. expires September 2001 [Page 39]
Internet-Draft April 2001 contain an Failed-Command-Code AVP containing the unrecognized Command-Code. DIAMETER_UNABLE_TO_DELIVER 5003 The request could not be delivered to a host that handles the realm, and extension, requested at this time. DIAMETER_REALM_NOT_SERVED 5004 The originator of the DSI message could not deliver the message since the realm requested is unknown. DIAMETER_ERROR_TOO_BUSY 5005 When returned, a Diameter node SHOULD attempt to sent the message to an alternate peer. DIAMETER_CANNOT_PROCESS_IN_TIME 5006 The time limit in a request's Max-Wait-Time AVP has expired, and no response is available. This value MAY also be used to inform a peer that the request is not expected to be processed within the Max-Wait-Time value. 10.0 End-to-End Error Signaling There are six different types of error conditions that can occur within Diameter. The first occurs when a Diameter message is poorly formatted, and unrecognizable, indicated in the figure below as "Bad Message". This error condition applies if a received message is less than the length of the Diameter header. Messages that generate such an error are ignored. A second case occurs when a Command-Code field is set to an unsupported value, which is shown as "Unknown Command" in the figure. Such errors generate a Device-Status-Ind message, and require per-hop behavior. A third case occurs when an AVP is received, marked as Mandatory ('M' bit is set), and is unknown by the receiver. This error condition is labelled as "Unknown AVP" in the figure below, and causes a Message- Reject-Ind message to be sent. The fourth case occurs when a message is received that contains an AVP with either an unknown or illegal value. This is labelled as "Bad AVP Value", and requires that a Message-Reject-Ind message be sent. The last two cases require that a Message-Reject-Ind message be Calhoun et al. expires September 2001 [Page 40]
Internet-Draft April 2001 generated to ensure that such errors are identified in both request and response messages. The last error condition occurs when an extension specific error is identified in a request or response message. In a message of type request or query, the natural corresponding answer or response message MUST be used. However, if an error occurs while processing an indication, answer or response message, a Message-Reject-Ind is used to inform the peer that an error occurred while processing the message. Error Type Ignore Send Send Send Message MRI DSI Response Bad Message X Unknown Command X Unknown AVP X Bad AVP Value X Request,Query Error X Answer,Response,Ind Error X "Ignore Message" indicates that the message is simply dropped. "Send MRI" means that a Message-Reject-Ind message is sent to report the error condition, while "Send DSI" requires that a Device-Status-Ind message is sent (see Section 9.1). "Send Response" means that the response message for a request or query message is returned. 10.1 Message-Reject-Ind (MRI) Command The Message-Reject-Ind (MRI), indicated by the Command-Code set to 259, provides a generic means of completing transactions by indicating errors in the messages that initiated them. The Message- Reject-Ind command is sent in response: 1. An error is found in a message of type Ind, Answer and Response 2. A Unknown AVP, marked as Mandatory, is received 3. An AVP was received with an unknown, or illegal, value. The Message-Reject-Ind message MUST contain the same Hop-by-Hop Identifier value in the header as the message that caused the error condition. If the Session-Id AVP was present in the original message, the same AVP MUST be present in the MRI. Message Format Calhoun et al. expires September 2001 [Page 41]
Internet-Draft April 2001 <Message-Reject-Ind message> ::= < Diameter Header: 259 > [ Session-Id ] { Result-Code } { Origin-FQDN } { Origin-Realm } { Error-Reporting-FQDN } [ Failed-Command-Code ] [ Failed-AVP ] * [ AVP ] * [ Proxy-State ] * [ Route-Record ] * [ Destination-Realm ] where the Result-Code AVP indicate the nature of the error causing rejection, and the Failed-AVP AVP provides some minimal debugging data by indicating a specific AVP type which caused the problem. See the description of the Result-Code AVP for indication of when the Failed-AVP AVP MUST be present in the message. See [25] for more information. 10.1.1 Failed-AVP AVP The Failed-AVP AVP (AVP Code 279) is of type OctetString and provides debugging information in cases where a request is rejected or not fully processed due to erroneous information in a specific AVP. The value of the Result-Code AVP will provide information on the reason for the Failed-AVP AVP. A Diameter message MAY contain one or more Failed-AVP AVPs, each containing a complete AVP that could not be processed successfully. The possible reasons for this AVP are the presence of an improperly constructed AVP, an unsupported or unrecognized AVP, an invalid AVP value, the omission of a required AVP, the presence of an explicitly excluded AVP (see table 14.0), or the presence of two or more occurances of an AVP which table 14.0 restricts to 0, 1, or 0-1 occurances. 10.1.2 Failed-Command-Code AVP The Failed-Command-Code AVP (AVP Code 270) is of type Unsigned32 and contains the offending Command-Code that resulted in sending the Message-Reject-Ind message. 10.1.3 Failed-Vendor-Id AVP Calhoun et al. expires September 2001 [Page 42]
Internet-Draft April 2001 The Failed-Command-Code-Vendor-Id AVP (AVP Code 262) is of type Unsigned32 and MUST be present if a vendor-specific Command-Code or AVP caused the error. 10.2 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 messages of type *-Response or *-Answer MUST include one Result-Code AVP, while messages of type -Ind MAY include the Result-Code AVP. A non-successful Result-Code AVP (one containing a non 2001 value) MUST include the Error- Reporting-FQDN AVP. The Result-Code data field contains an IANA-managed 32-bit address space representing errors (see section 17.4). Diameter provides four different classes of errors, all identified by the thousands digit: - 1xxx (Informational) - 2xxx (Success) - 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. 10.2.1 Informational Errors that fall within the Informational category are used to inform a requester that the request cannot be immediately satisfied and a further response will be issued in the near future. There are currently no errors that fall within this class. 10.2.2 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. 10.2.4 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 Calhoun et al. expires September 2001 [Page 43]
Internet-Draft April 2001 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_NO_END_2_END_SECURITY 4002 A proxy has detected that end-to-end security has been applied to portions of the Diameter message, and the proxy does not allow this security mode since it needs to alter the message by applying some local policies. DIAMETER_OUT_OF_SPACE 4003 A Diameter node received the accounting request but was unable to commit it to stable storage due to a temporary lack of space. 10.2.5 Permanent Failures Errors that fall within the permanent failures category are used to inform the peer that the request failed, and should not be attempted again. DIAMETER_USER_UNKNOWN 5001 A request was received for a user that is unknown, therefore authentication and/or authorization failed. DIAMETER_AVP_UNSUPPORTED 5002 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 5003 The request or response contained an unknown Session-Id. DIAMETER_AUTHORIZATION_REJECTED 5004 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 5005 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 5006 Calhoun et al. expires September 2001 [Page 44]
Internet-Draft April 2001 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 data portion of the Failed-AVP MUST only contain the AVP Code of the missing AVP. DIAMETER_INVALID_CMS_DATA 5007 The Request did not contain a valid CMS-Data [11] AVP. DIAMETER_LOOP_DETECTED 5008 A Proxy or Redirect server detected a loop while trying to get the message to the Home Diameter server. Further attempts should not be attempted until the loop has been fixed. DIAMETER_AUTHORIZATION_FAILED 5009 A request was received for which the user could not be authorized at this time. This error could occur when the user has already expended allowed resources, or is only permitted to access services within a time period. DIAMETER_CONTRADICTING_AVPS 5010 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 5011 A message was received with an AVP that MUST NOT be present. The Failed-AVP AVP MUST be included and contain the AVP Code of the offending AVP. DIAMETER_AVP_OCCURS_TOO_MANY_TIMES 5012 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 the AVP Code of the offending AVP. 10.3 Error-Message AVP The Error-Message AVP (AVP Code 281) is of type OctetString. It is a human readable UTF-8 character encoded string. 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. 10.4 Error-Reporting-FQDN AVP Calhoun et al. expires September 2001 [Page 45]
Internet-Draft April 2001 The Error-Reporting-FQDN AVP (AVP Code 294) is of type OctetString, encoded in the UTF-8 [24] format. This AVP contains the Network Access Identifier of the Diameter host that set the Result-Code AVP to a value other than 2001 (Success). This AVP is intended to be used for troubleshooting purposes, and MUST be set when the Result-Code AVP indicates a failure. 11.0 "User" Sessions When a user requests access to the network, a Diameter client issues an authentication and authorization request to its local server. The request contains a Session-Id AVP, which is used in subsequent messages (e.g. subsequent authorization, accounting, etc) relating to the user's session. The Session-Id AVP is a means for the client and servers to correlate a Diameter message with a user session. When a Diameter server authorizes a user to use network resources, it SHOULD add the Authorization-Lifetime AVP to the response. The Authorization-Lifetime AVP defines the maximum amount of time a user MAY make use of the resources before another authorization request is to be transmitted to the server. If the server does not receive another authorization request before the timeout occurs, it SHOULD release any state information related to the user's session. Note that the Authorization-Lifetime AVP implies how long the Diameter server is willing to pay for the services rendered, therefore a Diameter client SHOULD NOT expect payment for services rendered past the session expiration time. The base protocol does not include any authorization request messages, since these are largely application-specific and are defined in a Diameter protocol extension document. 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. 11.1 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. The term Service-Specific below refers to a message defined in a Diameter extension (e.g. Mobile IP, NASREQ). Calhoun et al. expires September 2001 [Page 46]
Internet-Draft April 2001 State Event Action New State ------------------------------------------------------------- Idle Client or Device Requests send serv. Pending access specific auth req Idle Service-Specific authorization send serv. Open request received, and specific successfully processed response Pending Successful Service-Specific Grant Open Authorization response Access received Open Authorization-Lifetime expires send serv. Open specific auth req Open Successful Service-Specific Extend Open Authorization response Access received Open Failed Service-Specific Discon. Closed Authorization response user/device received. Open Session-Timeout Expires on send STR Discon Access Device Open STI Received send STR Discon Open Session-Timeout Expires on send STI Discon home AAA server Discon STI Received ignore Discon Discon STR Received Send STA Closed Discon STA Received Discon. Closed user/device Closed Transition to state Cleanup When the Cleanup action is invoked, the Diameter node MAY attempt to release all resources for the particular session. Any event not listed above MUST be considered as an error condition, and a response, if applicable, MUST be returned to the originator of the message. Calhoun et al. expires September 2001 [Page 47]
Internet-Draft April 2001 11.2 Session-Id AVP The Session-Id AVP (AVP Code 263) is of type OctetString and is used to identify a specific session (see section 11.0). The Session-Id data uses the UTF-8 [24] character set. 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). For messages that do not pertain to a specific session, multiple Session-Id AVPs MAY be present as long as they are encapsulated within an AVP of type Grouped. The Session-Id MUST be globally unique at any given time since it is used by the server to identify the session (or flow). The format of the session identifier SHOULD be as follows: <Sender's Origin-FQDN><sender's port number> <monotonically increasing 32 bit value><optional value> The monotonically increasing 32 bit value SHOULD NOT start at zero upon reboot, but rather start at a random value. This will minimize the possibility of overlapping Session-Ids after a reboot. Alternatively, an implementation MAY keep track of the increasing value in non-volatile memory. The optional value is implementation specific but may include a modem's device Id, a layer 2 address, timestamp, etc. The session Id is created by the Diameter device initiating the session, which in most cases is done by the client. Note that a Session-Id MAY be used by more than one extension (e.g. authentication for a specific service and accounting, both of which have separate extensions). 11.3 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 value could create significant Diameter traffic, which could congest both the network and the servers. This AVP MAY be provided by the client as a hint of the maximum duration that it is willing to accept. However, the server DOES NOT Calhoun et al. expires September 2001 [Page 48]
Internet-Draft April 2001 have to observe the hint, and MAY return a value that is smaller than the hint. A value of zero means that no re-authorization is required. 11.4 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. A value of zero means that this session has an unlimited number of seconds before termination. This AVP MAY be provided by the client as a hint of the maximum duration that it is willing to accept. However, the server DOES NOT have to observe the hint, and MAY return a value that is smaller than the hint. 11.5 User-Name AVP The User-Name AVP (AVP Code 1) [1] is of type OctetString, which contains the User-Name. The value is represented as a UTF-8 character encoded string in a format consistent with the NAI specification [8]. 11.6 Max-Wait-Time AVP The Max-Wait-Time AVP (AVP Code 295) is of type Unsigned32, and contains the maximum amount of time the downstream server is willing to wait for a response. A server that determines that it cannot satisfy a request within the requested time MUST issue a DSI message with the DSI-Event set to DIAMETER_STILL_WORKING or DIAMETER_CANNOT_PROCESS_IN_TIME. 11.7 Original-Session-Id AVP The Original-Session-Id AVP (AVP Code 261) is of type OctetString and MAY be sent in a message of type Response or Answer if the Home AAA server already has a session identifier for the user, and wishes to keep the existing Session-Id. All further messages from the Access Device for this session MUST use the session identifier in this AVP. This shouldn't be viewed as a new session, but rather renaming the old session. 11.8 Session Termination Calhoun et al. expires September 2001 [Page 49]
Internet-Draft April 2001 The Diameter Base Protocol provides a set of messages that MUST be used by any peer to explicitly request that a previously authenticated and/or authorized session be terminated. Since the Session-Id is typically tied to a particular service (i.e. Mobile IP, NASREQ, etc), the session termination messages are used to request that the service tied to the Session Id be terminated. 11.8.1 Session-Termination-Ind The Session-Termination-Ind (STI), indicated by the Command-Code set to 274, MAY be sent by any Diameter entity to the access device to request that a particular session be terminated. This message MAY be used when a server detects that a session MUST be terminated, which is typically done as a policy decision (e.g. local resources have been expended, etc). The Destination-FQDN AVP MUST be present, and contain the fully qualified domain name of the access device that initiated the session (see section 11.0). Upon receipt of the STI message, the access device SHOULD issue a Session-Terminate-Request message. Message Format <Session-Termination-Ind> ::= < Diameter Header: 274 > < Session-Id > { Origin-FQDN } { Origin-Realm } { User-Name } { Destination-Realm } { Destination-FQDN } * [ AVP ] * [ Proxy-State ] 11.8.2 Session-Termination-Request The Session-Termination-Request (STR), indicated by the Command-Code set to 275, is sent by the access device to inform the Diameter Server that an authenticated and/or authorized session is being terminated. Message Format Calhoun et al. expires September 2001 [Page 50]
Internet-Draft April 2001 <Session-Termination-Request> ::= < Diameter Header: 275 > < Session-Id > { Origin-FQDN } { Origin-Realm } { User-Name } { Destination-Realm } { Destination-FQDN } * [ AVP ] * [ Proxy-State ] * [ Route-Record ] 11.8.3 Session-Termination-Answer The Session-Termination-Answer (STA), indicated by the Command-Code set to 276, is sent by the Diameter Server to acknowledge that the session has been terminated. The Result-Code AVP MUST be present, and MAY contain an indication that an error occurred while servicing the STR. Upon sending or receipt of the STA, the Diameter Server MUST release all resources for the session indicated by the Session-Id AVP. Any intermediate server in the Proxy-Chain MAY also release any resources, if necessary. Message Format <Session-Termination-Answer> ::= < Diameter Header: 276 > < Session-Id > { Result-Code } { Origin-FQDN } { Origin-Realm } { Destination-FQDN } { User-Name } * [ AVP ] * [ Proxy-State ] * [ Route-Record ] 12.0 Message Routing This section describes the expected behavior of a Diameter server acting as a proxy or redirect server. 12.1 Realm-Based Message Routing Diameter request, query and indication message routing is done Calhoun et al. expires September 2001 [Page 51]
Internet-Draft April 2001 through the use of the realm portion of the Network Access Identifier (NAI) or via a realm encoded in an AVP (e.g. Origin-Realm, Destination-Realm), and an associated realm routing table (see section 12.1.1). When an NAI is used, the realm portion of the user@realm is used to perform the realm lookup. Diameter servers have a list of locally supported realms, and MAY have a list of externally supported realms. When a request, query or indication message is received that includes a realm that is not locally supported, the message is proxied to the Diameter entity configured in the "route" table. Figure 2 depicts an example where DIA1 receives a request to authenticate user "joe@abc.com". DIA1 looks up "abc.com" in its local realm route table and determines that the message must be proxied to DIA2. DIA2 does the same check, and proxies the message to DIA3. DIA3 checks its realm route table, and determines that the realm is locally supported, and processes the authentication request, and returns the response. How the response actually makes it back to the sender of the original request is described in the next section. (Origin-FQDN=dia1.mno.net) (Origin-FQDN=dia1.mno.net) (Origin-Realm=mno.net) (Origin-Realm=mno.net) (Destination-Realm=abc.com) (Destination-Realm=abc.com) (Route-Record=dia1.mno.net) (Route-Record=dia1.mno.net) (Route-Record=dia2.xyz.com) +------+ ------> +------+ ------> +------+ | | (Request) | | (Request) | | | DIA1 +-------------------+ DIA2 +-------------------+ DIA3 | | | | | | | +------+ <------ +------+ <------ +------+ mno.net (Response) xyz.com (Response) abc.com (Origin-Realm=abc.com) (Origin-Realm=abc.com) (Destination-FQDN=dia1.mno.net) (Destination-FQDN=dia1.mno.net) (Route-Record=dia2.xyz.com) Figure 2: Realm-Based Routing 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. 12.1.1 Realm-Based Routing Table All Realm-Based routing lookups are performed against what is commonly known as the Domain Routing Table (see section 19.0). A Domain Routing Table Entry contains the following fields: Calhoun et al. expires September 2001 [Page 52]
Internet-Draft April 2001 - Domain Name. The Domain Name is analogous to the realm portion of the NAI. 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. - Extension Id. It is possible for a routing entry to have a different destination based on the extension identifier 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 routing entry with the Local Action set to Local can be satisfied locally, and do not need to be forwarded to another server. 2. PROXY - All Diameter messages that fall within this category MUST be forwarded 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 forwarding. See section 12.4 for more information. 3. 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 12.3 for more information. - Server Identifier - One or more servers the message is to be forwarded to. When the Local Action is set to PROXY, this field contains the identities of the server(s) the message must be forwarded to. When the Local Action field is set to REDIRECT, this field contains the Home Diameter server(s) for the realm. It is important to note that Diameter servers MUST support at least one of the PROXY, REDIRECT, or LOCAL modes of operation. Servers do not need to support all modes of operation in order to conform with the protocol specification. Servers MUST NOT reorder AVPs with the same AVP Code. When a message is being proxied, the servers in a given domain routing entry MUST have advertised the Extension Identifier (see section 6.1.3) for the given message, or have advertised the Wildcard Extension. 12.2 Proxy and Redirect Server handling of requests When a message of type request, query or indication is received by a proxy or redirect server, and it is determined that the request cannot be locally handled, the next hop for the request is determined Calhoun et al. expires September 2001 [Page 53]
Internet-Draft April 2001 in the following order: 1. If the Destination-FQDN AVP is present, and the host specified in the AVP can be directly contacted, the message is forwarded to the host (see section 5.1 for more information), or 2. If the Destination-Realm AVP is present, a routing table lookup is performed using the domain specific in the AVP. A message that does not contain any of the above AVPs MUST NOT be routed. If the message in question cannot be handled locally, a Message-Reject-Ind is sent with the Result-Code AVP set to an appropriate error condition. 12.3 Redirect Server A Redirect Server is one that provides Realm to Diameter Home Server address resolution. When a message is received by a peer, the Destination-Realm AVP (or the User-Name AVP if the Destination-Realm AVP is not present) is extracted from the message, and is used to perform a lookup in the domain routing table. Implementations MAY also use the Extension-Id as a secondary key in the domain routing table lookup. Successful routing table lookups will return one or more home Diameter servers that could satisfy the message. The home servers are encoded in one or more Redirect-Host AVPs, and the Command-Code field is set to Device-Status-Ind. +------------------+ | Diameter | | Redirect Server | +------------------+ ^ | Request | | DSI + joe@xyz.com | | DSI-Event = Redirect + | | Redirect-Host AVP(s) | v +----------+ Request +----------+ | abc.net |------------->| xyz.net | | Diameter | | Diameter | | Server |<-------------| Server | +----------+ Response +----------+ Figure 3: Diameter Redirect Server Lastly, the DSI-Event AVP is added with the Data field of the AVP set to DIAMETER_REDIRECT_INDICATION, and the message is returned to the sender of the request. Redirect servers MAY also include the certificate of the Home server(s). These certificates are Calhoun et al. expires September 2001 [Page 54]
Internet-Draft April 2001 encapsulated in a CMS-Data AVP [11]. When this occurs, the server forwarding the request directly to the Home Diameter server SHOULD include its own certificate in the message. 12.3.1 Redirect-Host AVP The Redirect-Host AVP (AVP Code 292) is of type Grouped and is found in Device-Status-Ind messages that include the DSI-Event AVP set to DIAMETER_REDIRECT_REQUEST. This AVP only needs to be used if the host the message is to be redirected to is not listening on the standard Diameter port. Its Data field has the following ABNF grammar: Redirect-Host = Redirect-Host-Address Redirect-Host-Port Redirect-Host-Address = ; See Section 12.3.2 Redirect-Host-Port = ; See Section 12.3.3 The Redirect-Host-Address AVP Data field contains the IP Address of the Diameter host to which the request MUST be redirected. The Redirect-Host-Port contains the port number to which the request should be sent. Upon receipt of such a event, and this AVP, the receiving host SHOULD send the request directly to the host identified by the Redirect-Host-Address AVP. +---------------------------------------------------------------+ | AVP Header (AVP Code = 292) | +---------------------------------------------------------------+ | Redirect-Host-Address AVP | +---------------------------------------------------------------+ | Redirect-Host-Port AVP | +---------------------------------------------------------------+ 12.3.2 Redirect-Host-Address AVP The Redirect-Host-Address AVP (AVP Code 278) is of type Address. Its use is described in Section 12.3.1. 12.3.3 Redirect-Host-Port AVP The Redirect-Host-Port AVP (AVP Code 277) is of type Unsigned32. Its use is described in Section 12.3.1. 12.4 Proxy Server This section outlines the processing rules for Diameter proxy servers. A proxy server can either be stateful or stateless. A Proxy Calhoun et al. expires September 2001 [Page 55]
Internet-Draft April 2001 server MAY act in a stateful manner for some requests, and be stateless for others. There are two types of states that servers MAY wish to maintain; transaction and session. Maintaining transaction state implies that a server keeps a copy of a request, which is then used when the corresponding response is received. This could be done to apply local policies to the message, or simply for auditing purposes. Maintaining session state implies that a server keeps track of all "active" users. An active user is one that has been authorized for a particular service, and the server has not received any indication that the user has relinquished access. A stateless proxy is one that does not maintain session state, but MUST maintain transaction state. Transaction state SHOULD be released after a request's corresponding response has been forwarded towards the recipient, and has been acknowledged by the underlying transport. A stateful proxy is one that maintains both transaction and session state, the latter being done by observing request and responses. Session state SHOULD be released once it is informed that a user and/or device has relinquished access. A stateful server MAY provide the following features: - Protocol translation (e.g. RADIUS <-> Diameter) - Limiting resources authorized to a particular user - Per user or transaction auditing Home servers processing requests that include the Route-Record and/or the Proxy-State AVPs MUST return these AVPs in the same order in the corresponding response. 12.4.1 Proxying Requests In addition to the rules defined in section 12.2, the following procedures MUST be handled by proxy servers handling messages of type request, query or indication. A proxy server MUST check for forwarding loops before proxying a message of type Request, Query or Indication. Such as message has been looped if the server finds its own address in a Route-Record AVP. A Diameter server that proxies a message or type Request, Query or Indication MUST append a Route-Record AVP, which includes its identity. Diameter Servers that receive messages MUST validate the last Route-Record AVP in the message and ensure that the host identified in the AVP is the same as the sender of the message. Calhoun et al. expires September 2001 [Page 56]
Internet-Draft April 2001 A Proxy Server MAY also include the Proxy-State AVP in a message of type Request or Query, which is used to encode local state information. The Proxy-State AVP is guaranteed to be present in the corresponding response. The message is then forwarded to the downstream Diameter server, as identified in the Domain Routing Table. Proxy Server MUST save the Hop-by-Hop Identifier in request messages, if the value of the field is changed, with a locally unique value. The saved identifier MAY be encoded in the Proxy-State AVP, and will be required in the processing of the corresponding response. 12.4.2 Proxying Responses A proxy server MUST only process messges of type Response or Answer whose last Route-Record AVP matches one of its addresses. Any responses that do not conform to this rule MUST be dropped. The last Route-Record AVP MUST be removed from the message before it is forwarded to the next hop, which is identified by the second to last Route-Record AVP. If the last Proxy-State AVP in the message is targeted to the local Diameter server, the AVP MUST be removed. If a proxy server receives a response 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. Prior to forwarding the response, proxy servers MUST restore the original value of the Diameter header's Hop-by-Hop Identifier field. 12.4.3 Route-Record AVP The Route-Record AVP (AVP Code 282) is of type OctetString, encoded in the UTF-8 [24] format, and contains the Fully Qualified Domain Name of the Proxy appending this AVP to a Diameter message. The FQDN added in this AVP MUST be the same as the FQDN sent in the Origin- FQDN in the Device-Reboot-Ind message. 12.4.4 Proxy-State AVP The Proxy-State AVP (AVP Code = 33) is of type Grouped. The Grouped Data field has the following ABNF grammar: Calhoun et al. expires September 2001 [Page 57]
Internet-Draft April 2001 Proxy-State = Proxy-Address Proxy-Info Proxy-Address = ; See Section 12.4.5 Proxy-Info = ; See Section 12.4.6 The Proxy-Address AVP Data field contains one of the IP addresses of the system that created the AVP. This assists hosts in determining whether a Proxy-State AVP is intended for the local host. The Proxy- Info AVP contains state information, and MUST be treated as opaque data. +---------------------------------------------------------------+ | AVP Header (AVP Code = 33) | +---------------------------------------------------------------+ | Proxy-Address AVP | +---------------------------------------------------------------+ | Proxy-Info AVP | +---------------------------------------------------------------+ 12.4.5 Proxy-Address AVP The Proxy-Address AVP (AVP Code = 280) is of type Address. Its use is described in Section 12.4.4. 12.4.6 Proxy-Info AVP The Proxy-Info AVP (AVP Code = 284) is of type OctetString. Its use is described in Section 12.4.4. 12.4.7 Destination-Realm AVP The Destination-Realm AVP (AVP Code 283) is of type OctetString, encoded in the UTF-8 [24] format, and contains the realm the message is to be routed to. The Destination-Realm AVP MUST NOT be present in messages of type Answer of Reply. Diameter Clients insert the realm portion of the User-Name AVP. Home servers initiating a message of type Request, Query or Indication 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. 12.5 Applying Local Policies Proxies MAY apply local access policies to Diameter requests, or responses, by adding, changing or deleting AVPs in the messages. Calhoun et al. expires September 2001 [Page 58]
Internet-Draft April 2001 Proxies that apply local policies MUST NOT allow end-to-end security on any messages that traverse through it, unless security is terminated locally. A proxy wishing to modify a Diameter message to enforce some local policy that detects that end-to-end security has been applied to the message MUST return a response to the originator with the Result-Code set to DIAMETER_NO_END_2_END_SECURITY. The originator of the request MAY re-issue the request with no end-to-end security if it falls within its local policy. In the event that the Home Diameter server receives a request with contradictory information (possibly due to some proxy adding a local policy), it MAY accept the latest AVP, or MAY return the response with the Result-Code AVP set to DIAMETER_CONTRADICTING_AVPS. However, a NAS receiving a response that contains contradictory information SHOULD reject service to the user. 12.6 Hiding Network Topology Stateful proxies forwarding requests to servers outside of their administrative domain MAY hide the internal network topology. Servers perform this by removing all Route-Record AVPs in the message, and maintains the Route-Record AVPs to add to the corresponding response. Such stateful servers MUST still add their own Route-Record AVP to the request prior to forwarding. 12.7 Loop Detection When a Diameter Proxy or Redirect server receives a message of type Request, Query or Indication, it MUST examine all Route-Record AVPs in the message to determine whether such an AVP already exists with the local server's identity. If an AVP with the local host's identity is found in the request, it is an indication that the message is being looped through the same set of proxies. When such an event occurs, the Diameter server that detects the loop returns a response with the Result-Code AVP set to DIAMETER_LOOP_DETECTED. 13.0 Accounting This accounting protocol is based on an authorization-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 Calhoun et al. expires September 2001 [Page 59]
Internet-Draft April 2001 capabilities of the used devices. 13.1 Authorization-Server Directed Model The authorization-server directed model means that at authorization time, the device generating the accounting data gets information from the authorization 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 this extension. Should Batched Accounting be required in the future, a new Diameter extension 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 proxies in between) 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. 13.2 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. 13.3 Extension document requirements Each Service-Specific Diameter extension (e.g. NASREQ, MobileIP), Calhoun et al. expires September 2001 [Page 60]
Internet-Draft April 2001 MUST define their Service-Specific AVPs that MUST be present in the Accounting-Request message in a section entitled "Accounting AVPs". The extension 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. 13.4 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 servers 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 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 extension 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. 13.5 Session Records In all accounting records the Session-Id and User-Name AVPs MUST be present. If strong authentication is required, as described in [11], Calhoun et al. expires September 2001 [Page 61]
Internet-Draft April 2001 the CMS-Data AVP may be used to authenticate the Accounting Data and Service Specific AVPs. It is not typically necessary, nor recommended, that the strong authentication cover any additional AVPs since the Data and Service Specific AVP, and associated CMS-Data, MAY need to be submitted to a third party. Different types of session 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, 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 a NAS for any given session. 14.0 Accounting Command-Codes This section defines new Command-Code values that MUST be supported by all Diameter implementations that provide Accounting services. 14.1 Accounting-Request (ACR) Command The Accounting-Request command, indicated by the Command-Code field set to 271, 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 broker, and includes the CMS-Data AVP [11], the CMS-Data AVP MUST be signed by Calhoun et al. expires September 2001 [Page 62]
Internet-Draft April 2001 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 13.3. Message Format <Accounting-Request> ::= < Diameter Header: 271 > < Session-Id > { Extension-Id } { User-Name } { Origin-FQDN } { Origin-Realm } { Destination-Realm } { Accounting-Record-Type } { Accounting-Record-Number } [ Accounting-Interim-Interval ] { Accounting-Session-Id } * [ AVP ] [ CMS-Data ] * [ Proxy-State ] * [ Route-Record ] 14.2 Accounting-Answer (ACA) Command The Accounting-Answer command, indicated by the Command-Code field set to 272, 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 13.3. Calhoun et al. expires September 2001 [Page 63]
Internet-Draft April 2001 Message Format <Accounting-Answer> ::= < Diameter Header: 272 > < Session-Id > { Extension-Id } { User-Name } { Result-Code } { Origin-FQDN } { Origin-Realm } { Accounting-Record-Type } { Accounting-Record-Number } { Accounting-Session-Id } [ Error-Reporting-FQDN ] [ Accounting-Interim-Interval ] * [ AVP ] [ CMS-Data ] * [ Proxy-State ] * [ Route-Record ] 14.3 Accounting-Status-Ind (ASI) Command The Accounting-Status-Ind command, indicated by the Command-Code field set to 279, is sent by a Diameter node in order to inform its peer of whether Accounting messages will be sent in the future. A Diameter node that is about to be taken out of service SHOULD issue an Accounting-Status-Ind message, with the Accounting-State AVP set to DISABLED. A Diameter node that detected that it is able to issue Accounting messages MUST issue an Accounting-Status-Ind message, with the Accounting-State AVP set to ENABLED. Message Format <Accounting-Status-Ind> ::= < Diameter Header: 279 > { Extension-Id } { Origin-FQDN } { Origin-Realm } { Destination-Realm } { Accounting-State } * [ AVP ] * [ Proxy-State ] * [ Route-Record ] 14.4 Accounting-Poll-Ind (API) Command The Accounting-Poll-Ind command, indicated by the Command-Code field set to 273, is sent by a Diameter Server in order to force the peer Calhoun et al. expires September 2001 [Page 64]
Internet-Draft April 2001 to send current accounting data. This data MUST include not yet sent accounting records from completed sessions, as well as INTERIM_RECORD records from all ongoing sessions. Diameter implementations MAY support the Accounting-Poll-Ind command. An implementation still conforms to this specification if API is not supported. The receiver MUST use the Accounting-Request command to send the accounting data. The use of Accounting-Poll-Ind is useful in situations where a Diameter server comes up after an unscheduled downtime, and wishes to synchronize with the client(s) sooner than at the end of the next INTERIM_RECORD or at the end of a session. Warning: The use of the Accounting-Poll-Ind message is discouraged in roaming networks, since it is unfeasible for a server to attempt to poll all of it's roaming partner's Diameter peers. Message Format <Accounting-Poll-Ind> ::= < Diameter Header: 273 > < Session-Id > { Extension-Id } { Destination-FQDN } { Origin-FQDN } { Origin-Realm } { Destination-Realm } { Accounting-Session-Id } [ Destination-FQDN ] * [ AVP ] * [ Proxy-State ] * [ Route-Record ] 15.0 Accounting AVPs This section contains AVPs that describe accounting usage information related to a specific session. 15.1 Accounting-Record-Type AVP The Accounting-Record-Type AVP (AVP Code 480) is of type Unsigned32 and contains the type of accounting record being sent. The following values are currently defined for the Accounting-Record-Type AVP: Calhoun et al. expires September 2001 [Page 65]
Internet-Draft April 2001 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 extensions. 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. 15.2 Accounting-Interim-Interval AVP The Accounting-Interim-Interval AVP (AVP Code 482) is of type Unsigned32 and is sent from the Diameter authenticating/authorizing 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 behaviour 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. 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 Calhoun et al. expires September 2001 [Page 66]
Internet-Draft April 2001 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. 15.3 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. 15.4 Accounting-State AVP The Accounting-State AVP (AVP Code 486) is of type Unsigned32 and is used to communicate to a peer whether Accounting messages will be sent in the future. A node that issues an ASI with the Accounting- State AVP set to DISABLED is informing its peer that it will no longer be transmitting Accounting messages until a subsequent ASI message is sent with the Accounting-State AVP set to ENABLED. The following values have been defined: 1 ENABLED 2 DISABLED 15.5 Accounting-Session-Id AVP The Accounting-Session-Id AVP (AVP Code 44) is of type OctetString, and SHOULD be encoded in UTF-8 format [13]. The Accounting-Session-Id is not used by the Diameter protocol, since the Session-Id defined in [1] is used for both authentication/authorization and accounting purposes. However, a RADIUS/Diameter gateway MAY need to include the Calhoun et al. expires September 2001 [Page 67]
Internet-Draft April 2001 Accounting-Session-Id in Diameter accounting messages. 16.0 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. 16.1 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 September 2001 [Page 68]
Internet-Draft April 2001 +-------------------------------+ | Command-Code | |---+---+---+---+---+---+---+---+ Attribute Name |DRI|DSI|DWR|DWA|MRI|STI|STR|STA| ------------------------------|---+---+---+---+---+---+---+---| Authorization-Lifetime |0 |0 |0 |0 |0 |0 |0 |0 | Destination-FQDN |0 |0 |0 |1 |0+ |1 |0+ |1 | Destination-Realm |1 |1 |0 |0 |1 |1 |1 |0 | DSI-Event |0 |1 |0 |0 |0 |0 |0 |0 | Error-Message |0 |0 |0 |0 |0 |0 |0 |0 | Error-Reporting-FQDN |0 |0 |0 |0 |1 |0 |0 |0 | Extension-Id |1+ |0 |0 |0 |0 |0 |0 |0 | Failed-AVP |0 |0 |0 |0 |0-1|0 |0 |0 | Failed-Command-Code |0 |0 |0 |0 |0-1|0 |0 |0 | Failed-Vendor-Id |0 |0 |0 |0 |0-1|0 |0 |0 | Firmware-Revision |0-1|0 |0 |0 |0 |0 |0 |0 | Host-IP-Address |1+ |0 |0 |0 |0 |0 |0 |0 | Max-Time-Wait |0 |0 |0 |0 |0 |0 |0 |0 | Origin-FQDN |1 |1 |1 |1 |1 |1 |1 |1 | Origin-Realm |1 |1 |1 |1 |1 |1 |1 |1 | Original-Session-Id |0 |0 |0 |0 |0 |0 |0 |0 | Product-Name |1 |0 |0 |0 |0 |0 |0 |0 | Proxy-State |0 |0 |0 |0 |0+ |0+ |0+ |0+ | Redirect-Host |0 |0 |0 |0 |0 |0 |0 |0 | Result-Code |0 |0 |0 |1 |1 |0 |0 |1 | Route-Record |0 |0 |0 |0 |0+ |0+ |0+ |0+ | Session-Id |0 |0 |0 |0 |0-1|1 |1 |1 | Session-Timeout |0 |0 |0 |0 |0 |0 |0 |0 | Supported-Vendor-Id |0+ |0 |0 |0 |0 |0 |0 |0 | User-Name |0 |0 |0 |0 |0 |1 |1 |1 | Vendor-Id |1 |0 |0 |0 |0 |0 |0 |0 | ------------------------------|---+---+---+---+---+---+---+---| 16.2 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. Calhoun et al. expires September 2001 [Page 69]
Internet-Draft April 2001 +-----------------------+ | Command-Code | |-----+-----+-----+-----+ Attribute Name | ACR | ACA | API | ASI | ------------------------------|-----+-----+-----+-----+ Accounting-Interim-Interval | 0-1 | 0-1 | 0 | 0 | Accounting-Record-Number | 1 | 1 | 0 | 0 | Accounting-Record-Type | 1 | 1 | 0 | 0 | Accounting-Session-Id | 1 | 1 | 0 | 1 | Accounting-State | 0 | 0 | 1 | 0 | Destination-FQDN | 0+ | 1 | 0+ | 0-1 | Destination-Realm | 1 | 0 | 1 | 1 | Error-Reporting-FQDN | 0 | 0+ | 0 | 0 | Extension-Id | 1 | 1 | 1 | 1 | Integrity-Check-Value | 0-1 | 0-1 | 0-1 | 0-1 | Origin-FQDN | 1 | 1 | 1 | 1 | Origin-Realm | 1 | 1 | 1 | 1 | Proxy-State | 0+ | 0+ | 0+ | 0+ | Route-Record | 0+ | 0+ | 0+ | 0+ | Result-Code | 0 | 1 | 0 | 0 | Session-Id | 1 | 1 | 0 | 1 | ------------------------------|-----+-----+-----+-----+ 17.0 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. 17.1 AVP Attributes As defined in section 4.0, AVPs contain vendor ID, attribute and Data fields. For vendor ID value of 0, IANA will maintain a registry of assigned AVP codes and in some case also values. Attribute 0-254 are assigned from the RADIUS protocol [1], whose attributes are also maintained through IANA. AVP Codes 256-284, 480, 482, 485 and 486 are assigned within this document. The remaining values are available for assignment through Designated Expert [12]. 17.2 Command Code Values As defined in section 3.0, the Command Code field has an associated value maintained by IANA. Values 0-255 are reserved for backward Calhoun et al. expires September 2001 [Page 70]
Internet-Draft April 2001 RADIUS compatibility, and values 257, 259, 271, 272, 273, 274, 275, 276, 279, 280, 281, and 282 are in this specification. The remaining values are available for assignment via Designated Expert [12]. 17.3 Extension Identifier Values As defined in section 6.1.3, the Extension Identifier is used to identify a specific Diameter Extension. All values, other than zero (0) are available for assignment via Standards Action [12]. Note that the Diameter protocol is not inteded to be extended for any purpose. Any extensions added to the protocol MUST ensure that they fit within the existing framework, and that no changes to the base protocol are required. 17.4 Result-Code AVP Values As defined in Section 10.2, the Result-Code AVP (AVP Code 268) defines the values 2001, 4001-4003 and 5001-5012. All remaining values are available for assignment via IETF Consensus [12]. 17.5 Message Header Bits There are thirteen bits in the Flags field of the Diameter header. This document assigns bit 1 ('R'esponse), bit 2 ('I'nterrogation) and bit 3 ('E'xpected Reply). Bits 4 through 13 should only be assigned via a Standards Action [12]. 17.6 AVP Header Bits There are 16 bits in the Flags field of the AVP Header, defined in section 4.0. This document assigns bit 1 ('M'andatory), bit 3 ('V'endor Specific) and bit 5 ('P'rotected). The remaining bits should only be assigned via a Standards Action [12]. 17.7 DSI-Event AVP Values As defined in Section 9.1.1, the DSI-Event AVP (AVP Code 297) defines the values 1001, 3001, 4001 and 5001-5006. All remaining values are available for assignment via IETF Consensus [12]. 18.0 Open Issues Calhoun et al. expires September 2001 [Page 71]
Internet-Draft April 2001 The following are the open issues that SHOULD be addressed in future versions of the Diameter protocol: - AVPs with time values are represented by Unsigned32 type data. This value is a timestamp consistent with NTP [18]. This field is expected to expire sometime in 2038. Future investigation SHOULD be done to determine if a 64 bit time format could be used. - The fact that the Sender's IP Address is used in the construction of the Session-Id means that the introduction of Network Address Translation MAY cause two hosts to represent the same Session Identifier. This area needs to be investigated further to be able to support Diameter hosts on a private network. 19.0 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. RTT-Multiplier The Round Trip Time Multiplier is used to determine when a DWR message is to be sent to an inactive peer. The recommended valus is 4. Watchdog Interval Period The Watchdog Interval Period is the frequency at which DWR messages are sent to inactive peers. The recommended value is 30 seconds. Calhoun et al. expires September 2001 [Page 72]
Internet-Draft April 2001 20.0 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 Diameter brokers, or redirect servers. When third party brokers or redirect servers 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 extension 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. 21.0 References [1] Rigney, et alia, "RADIUS", RFC-2138, April 1997. [2] Reynolds, Postel, "Assigned Numbers", RFC 1700, October 1994. [3] Postel, "User Datagram Protocol", RFC 768, August 1980. [4] Rivest, "The MD5 Message-Digest Algorithm", RFC 1321, April 1992. [5] Kaufman, Perlman, Speciner, "Network Security: Private Communi- cations 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 Extension", draft-ietf-aaa-diameter-nasreq-01.txt, IETF work in progress, March 2001. [8] Aboba, Beadles "The Network Access Identifier." RFC 2486. Janu- ary 1999. [9] Calhoun, Zorn, Pan, Akhtar, "Diameter Framework", draft-ietf- aaa-diameter-framework-01.txt, IETF work in progress, March 2001. [10] P. Calhoun, C. Perkins, "Diameter Mobile IP Extensions", draft- Calhoun et al. expires September 2001 [Page 73]
Internet-Draft April 2001 ietf-aaa-diameter-mobileip-01.txt, IETF work in progress, March 2001. [11] P. Calhoun, W. Bulley, S. Farrell, "Diameter Strong Security Extension", draft-calhoun-diameter-strong-crypto-06.txt (work in progress), February 2001. [12] Narten, Alvestrand,"Guidelines for Writing an IANA Considera- tions Section in RFCs", BCP 26, RFC 2434, October 1998 [13] S. Bradner, "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [14] Myers, Ankney, Malpani, Galperin, Adams, "X.509 Internet Public Key Infrastructure Online Certificate Status Protocol (OCSP)", RFC 2560, June 1999. [15] 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 Infras- tructure 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", draft-ietf-nasreq-criteria-05.txt, IETF work in progress, June 2000. [22] T. Hiller and al, "CDMA2000 Wireless Data Requirements for AAA", draft-hiller-cdma2000-aaa-02.txt, IETF work in progress, Sep- tember 2000. [23] S. Glass, S. Jacobs, C. Perkins, "Mobile IP Authentication, Authorization, 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 September 2001 [Page 74]
Internet-Draft April 2001 [25] P. Calhoun, A. Rubens, H. Akhtar, E. Guttman, W. Bulley, J. Haag, "Diameter Implementation Guidelines", draft-ietf-aaa- diameter-impl-guide-00.txt, IETF work in progress, June 2000. [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 Protocol, Version 2", RFC 2165, June 1999. [29] P. Calhoun, "Diameter Resource Management", draft-calhoun- diameter-res-mgmt-06.txt, IETF Work in Progress, February 2001. [30] Institute of Electrical and Electronics Engineers, "IEEE Stan- dard for Binary Floating-Point Arithmetic", ANSI/IEEE Standard 754-1985, August 1985. [31] D. Crocker, P. Overell, "Augmented BNF for Syntax Specifica- tions: ABNF", RFC 2234, November 1997. [32] E. Guttman, C. Perkins, J. Kempf, "Service Templates and Ser- vice: 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 Protocol", RFC 2401, November 1998. [38] A. Frier, P. Karlton, and P. Kocher, "The SSL 3.0 Protocol", Netscape Communications Corp., Nov 18, 1996. [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 Calhoun et al. expires September 2001 [Page 75]
Internet-Draft April 2001 Management", RFC 2975, October 2000. [41] A. Shacham, R. Monsour, R. Pereira, M. Thomas, "IP Payload Compression 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 Implementa- tion in Roaming", RFC 2607, June 1999. [45] C. Perkins, Editor. IP Mobility Support. RFC 2002, October 1996. 22.0 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 assistance 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. The authors would also like to acknowledge the following people for their contribution in the development of the Diameter protocol: Bernard Aboba, William Bulley, Mark Eklund, David Frascone, Daniel C. Fox, Lol Grant, Ignacio Goyret, Nancy Greene, Peter Heitman, Fredrik Johansson, Mark Jones, Paul Krumviede, Fergal Ladley, Ryan Moats, Victor Muslin, Kenneth Peirce, Stephen Farrell, Sumit Vakil, John R. Vollbrecht, Jeff Weisberg and Jonathan Wood 23.0 Authors' Addresses Questions about this memo can be directed to: Calhoun et al. expires September 2001 [Page 76]
Internet-Draft April 2001 Pat R. Calhoun Network and Security Research Center, Sun Laboratories Sun Microsystems, Inc. 15 Network Circle Menlo Park, California, 94025 USA Phone: +1 650-786-7733 Fax: +1 650-786-6445 E-mail: pcalhoun@eng.sun.com 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 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 Calhoun et al. expires September 2001 [Page 77]
Internet-Draft April 2001 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 24.0 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 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. 25.0 Expiration Date This memo is filed as <draft-ietf-aaa-diameter-02.txt> and expires in Calhoun et al. expires September 2001 [Page 78]
Internet-Draft April 2001 September 2001. Calhoun et al. expires September 2001 [Page 79]
Internet-Draft April 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-00.txt template-url-syntax= url-path= ; The standard service URL syntax is used. ; For example: 'service:diameter://aaa.example.com:1812 Calhoun et al. expires September 2001 [Page 80]
Internet-Draft April 2001 supported-extensions= string L M # This attribute lists the Diameter extensions supported by the # AAA implementation. The extensions currently defined are: # Extension Name Defined by # --------------- ----------------------------------- # NASREQ draft-ietf-aaa-diameter-nasreq-00.txt # MobileIP draft-ietf-aaa-diameter-mobileip-00.txt # Strong Security draft-calhoun-diameter-strong-crypto-05.txt # Resource Management draft-calhoun-diameter-res-mgmt-06.txt # # Notes: # . Diameter implementations support one or more extensions. # . Additional extensions may be defined in the future. # An updated service template will be created at that time. # NASREQ,MobileIP,Accounting,Strong Security,Resource Management 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 September 2001 [Page 81]
