AAA Working Group Tony Johansson INTERNET DRAFT Kevin Purser Category: Standards Track Carolina Canales Miguel-Angel Pallares Ericsson Peter J. McCann Lucent Jaakko Rajaniemi Nokia Feb 2002 Diameter Multimedia Application 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. This document is an individual contribution for consideration by the SIP Working Group of the Internet Engineering Task Force. Comments should be submitted to the diameter@diameter.org mailing list. Distribution of this memo is unlimited. Copyright (C) The Internet Society 2001. All Rights Reserved. johansson et al. expires August 2002 [Page 1] INTERNET DRAFT Feb 2002 Abstract This document specifies a Diameter application that allows a Diameter server to authenticate, authorize, and collect accounting information for Session Initiation Protocol (SIP) services rendered to a client node. This application, combined with the base Diameter protocol and appropriate SIP extensions, allows SIP User Agents (UAs) to obtain services from SIP servers that are connected to a Diameter infrastructure. When combined with the Inter-Domain capability of the base protocol, service may even be obtained from SIP servers that belong to foreign domains, as would be encountered by roaming mobile nodes. Note that the specification defined here may be used independently of the authentication technique used for authenticating a node's link- layer or network-layer access. In particular, we do not require that the client node was authenticated for access with the use of either the Mobile IP [3] or NASREQ [2] Diameter application. johansson et al. expires August 2002 [Page 2] INTERNET DRAFT Feb 2002 Table of Contents 1.0 Introduction 1.1 Requirements language 1.2 Abbreviations 2.0 Description of a SIP network architecture 2.1 User Authentication by SSP 2.2 User Authentication by AAA server 2.3 Single SIP server 2.4 Invitation 2.5 Profile Updating 2.6 Termination 3.0 Command Codes 3.1 User-Authorization-Request (UAR) 3.2 User-Authorization-Answer (UAA) 3.3 Multimedia-Auth-Request (MAR) 3.4 Multimedia-Auth-Answer (MAA) 3.5 Profile-Update-Request (PUR) 3.6 Profile-Update-Answer (PUA) 3.7 Location-Info-Request (LIR) 3.8 Location-Info-Answer (LIA) 4.0 Authentication Details 5.0 Result Code AVP values 5.1 Success 5.2 Permanent failures 6.0 Diameter AVP values 6.1 SIP-Server AVP 6.2 SIP-Server-Name AVP 6.3 SIP-Capability AVP 6.4 SIP-Public-Identity AVP 6.5 SIP-Visited-Network-Identifier AVP 6.6 SIP-Profile-Update-Type AVP 6.7 SIP-Server-Type AVP 6.8 SIP-Authentication-Scheme AVP 6.9 SIP-Authenticate AVP 6.10 SIP-Authorization AVP 6.11 SIP-Authentication-Context AVP 6.12 SIP-Number-Auth-Items AVP 6.13 SIP-Auth-Data-Item AVP 6.14 SIP-Item-Number AVP 6.15 SIP-User-Data AVP 6.16 NAS-Session-Key AVP 6.17 NAS-Key-Binding AVP 6.18 SIP-User-Service-Info AVP 6.19 SIP-Deregistration-Reason AVP 6.20 SIP-Capability AVP 6.21 SIP-Version-Number AVP 6.22 SIP-Vendor-ID AVP johansson et al. expires August 2002 [Page 3] INTERNET DRAFT Feb 2002 6.23 SIP-Optional-Parameter AVP 6.24 SIP-Capability-Type AVP 6.25 SIP-Reason AVP 6.26 SIP-Server-Behavior AVP 7.0 References 8.0 Authors' Addresses 9.0 Full Copyright Statement johansson et al. expires August 2002 [Page 4] INTERNET DRAFT Feb 2002 1.0 Introduction This document specifies a Diameter application that allows a Diameter server to authenticate, authorize and collect accounting information for SIP-based IP multimedia services rendered to a client node. We assume that a client node implements a SIP User Agent (UA) that carries out SIP protocol actions with a SIP server, which in turn relies on the AAA infrastructure for authenticating the client, authorizing it for particular SIP services, and accounting for this usage. SIP servers can be proxy, redirect, registration, or user agent servers. Additionally, SIP servers may be arranged in arbitrary ways according to the inter-service provider relationships involved in servicing a given client. For example, a mobile node may use a SIP proxy in the visited network, but its SIP messages may be proxied back to a SIP server in the home network that implements call control features. Combined with the Inter-Domain capability of the base protocol, this extension would allow such mobile terminals to receive service from foreign service providers according to their location and subscription profile. Any or all of the SIP servers may need to independently authenticate the client, authorize service, and account for usage. Authentication must take place at the time the user agent registers with the SIP server (or chain of SIP proxies and servers). The particular algorithm used to authenticate a SIP user agent client is a matter of policy agreement between the user agent client, the SIP server, and the home AAA server. This document supports an embedding of the Extensible Authentication Protocol (EAP) authentication method, along with the WWW-Authenticate methods Basic and Digest which are supported by SIP. This is in the expectation that an EAP authentication method will be added to SIP. In addition to authenticating the user agent client, such a method could also be used to generate or distribute keys for subsequent SIP-layer message integrity and privacy. The specification of such an algorithm, and its embedding in SIP, is outside the scope of this document. Authorization for SIP services may take many forms. For example, a proxy may need to know that the user agent client is authorized to register, but from then on it may simply pass messages through to other SIP servers. However, a SIP server that implements call control features may need a richer and more complete description of the services to which the user has subscribed. johansson et al. expires August 2002 [Page 5] INTERNET DRAFT Feb 2002 Accounting for SIP services is on a per-call basis. An accounting record contains a SIP Call-ID, any SDP that was exchanged to set up the call, the duration of the call, and any resources that were consumed on behalf of the call (such as number of bytes exchanged between the parties). Note that accounting for resources may require the SIP server to interact with other network entities, such as media gateways, for the collection of this information. Such interaction is outside the scope of this document. Some example scenarios, inspired by the emerging wireless applications of SIP, are given in Section 1.2. Sections 2, 3 and 4 address the Diameter Multimedia Application's specific commands, result codes, and AVPs, respectively. Section 5 gives IANA considerations. 1.1 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 [3]. johansson et al. expires August 2002 [Page 6] INTERNET DRAFT Feb 2002 2.0 Description of a SIP network architecture Home Realm +-------+ UAR/UAA +-->| AAA |<--+ PUR/PUA MAR/MAA | |xyz.com| | MAR/MAA LIR/LIA | +-------+ | Local Realm v v +-------+ +-------+ +-------+ | OSP |<----------->| HSP |<----->| SSP | |abc.com| SIP |xyz.com| SIP |xyz.com| +-------+ +-------+ +-------+ ^ ^ | SIP | v | +-------+ SIP | | UAE |<----------------+ +-------+ bob@xyz.com Figure 1: SIP network infrastructure Figure 1 above illustrates the nodes involved in a SIP multimedia network architecture as put forth in [1]. The home realm (xyz.com) is comprised of a Diameter AAA server, at least one home entry SIP proxy (HSP) which is the gateway SIP proxy seen by the rest of the world, and any number of serving SIP proxy (SSP) nodes. These SSP nodes may be deployed piecemeal for various reasons such as but not limited to load balancing, scalability, and offering distinct, separate services. The mobile node in this scenario (bob@xyz.com) may either connect directly to its HSP, or via an outbound SIP server (OSP) in the local realm. In larger networks, registrations MAY be routed to different HSPs, potentially even for a subsequent SIP registration for the same user, and thus HSPs are usually stateless. The next few sections will describe in detail the different modes of operation that are available to such an infrastructure. These options may be either administratively configured to suit local policies, or determined dynamically by the network. For the purposes of authentication and authorization, the procedures involved when using a OSP are a superset of the procedures involved in the absence of a OSP, and therefore we will skip a needless explanation of the latter scenario. 2.1 User authentication by SSP An operator with a large base of installed SIP servers may wish to minimize the impact of modifying SIP servers to interact with johansson et al. expires August 2002 [Page 7] INTERNET DRAFT Feb 2002 Diameter AAA servers. This can be achieved by allowing SIP servers to retain the functionality of authentication, rather than exporting this capability to the AAA server. However, it should be noted that this mode will not leverage the extensive array of authentication and authorization services which will already be present regardless in diameter servers. Below follows an example of a SIP user registration using this mode of operation. +-------+ +-------+ +-------+ | HSP | | AAA | | SSP | +---+---+ +---+---+ +---+---+ | | | 1. SIP-REG | | | ---------->| 2. UAR | | +------------------>| | | 3. UAA | | |<------------------+ | | | 4. SIP-REG | +-------------------------------------->| | | 5. MAR | | |<------------------+ | | 6. MAA | | +------------------>| | 7. 401 (Unauthorized) | 8. 401 |<--------------------------------------+ <-----------+ | | 9. SIP-REG | | | ---------->| 10. UAR | | +------------------>| | | 11. UAA | | |<------------------+ | | | 12. SIP-REG | +-------------------------------------->| | | 13. PUR | | |<------------------+ | | 14. PUA | | +------------------>| | 15. 200 (OK) | | 16. 200 |<--------------------------------------+ <-----------+ | | | | | Figure 2: Authentication performed by the SSP In this scenario, a user sends a SIP registration to the home domain. The HSP will contact its local diameter server with a "User- Authorization-Request" (UAR) to authorize if this user is allowed to receive service and if so, request the identity of a local SIP server capable of handling this user. The diameter server will respond with johansson et al. expires August 2002 [Page 8] INTERNET DRAFT Feb 2002 a "User-Authorization-Answer" (UAA), which will indicate a list of capabilities from which the HSP will use to select the SSP. Once it forwards the initial SIP registration to the appropriate SSP, the SSP will then request authentication parameters from the diameter server through a "Multimedia-Auth-Request" (MAR). This request MAY also serve to identify the SSP, so as to return subsequent registration requests to the same SSP. The diameter server will respond with a "Multimedia-Auth-Answer" (MAA), which will include all parameters necessary for the designated authentication algorithm associated with the user. The SSP will then create the 401 (Unauthorized) message, including the authentication material needed by the mobile user to prove their identity. When the subsequent SIP registration is received from the user, the HSP will once again contact the diameter server with a UAR to determine to which SSP to forward the registration. The HSP will then forward the SIP registration to the SSP node, which will then perform the authentication procedure. Upon completion, the SSP will notify the AAA server through a "Profile-Update-Request" (PUR), indicating successful registration of the user, and the definitive name of the SSP. After the AAA server responds with a "Profile-Update-Answer" (PUA), including user profile information that the SSP will use to provide service to the user, the SSP will produce a 200 (OK) message, and send it to the HSP. The HSP will then forward the 200 (OK) message to the mobile user. 2.2 User authentication by AAA server A different approach in deploying SIP networks is to allow the Diameter server to perform the actual authentication. In addition to leveraging the robust authentication services offered by the AAA server, it will reduce the number of messages sent in the network. johansson et al. expires August 2002 [Page 9] INTERNET DRAFT Feb 2002 +-------+ +-------+ +-------+ | HSP | | AAA | | SSP | +---+---+ +---+---+ +---+---+ | | | 1. SIP-REG | | | ---------->| 2. UAR | | +------------------>| | | 3. UAA | | |<------------------+ | | | 4. SIP-REG | +-------------------------------------->| | | 5. MAR | | |<------------------+ | | 6. MAA | | +------------------>| | 7. 401 (Unauthorized) | 8. 401 |<--------------------------------------+ <-----------+ | | 9. SIP-REG | | | ---------->| 10. UAR | | +------------------>| | | 11. UAA | | |<------------------+ | | | 12. SIP-REG | +-------------------------------------->| | | 13. MAR | | |<------------------+ | | 14. MAA | | +------------------>| | 15. 200 (OK) | | 16. 200 |<--------------------------------------+ <-----------+ | | | | | Figure 3: Authentication performed by the AAA server In this scenario, the user will send a SIP register message to it's home domain. When the HSP receives this request, it will contact its local diameter server with a "User-Authorization-Request" (UAR) to determine if this user is allowed to receive service and if so, request the identity of a local SIP server capable of handling this user, as described in the previous section. The diameter server will respond with a "User-Authorization-Answer" (UAA), which will indicate a list of capabilities from which the HSP will use to select the SSP. Once it forwards the initial SIP registration to the appropriate SSP, the SSP will then request user authentication from the Diameter server through a "Multimedia-Auth-Request" (MAR). This request MAY also serve to identify the SSP, so as to return subsequent registration requests to the same SSP. The Diameter server will then johansson et al. expires August 2002 [Page 10] INTERNET DRAFT Feb 2002 respond with a "Multimedia-Auth-Answer" (MAA) with Result-Code equal to DIAMETER_MULTI_ROUND_AUTH and the challenge information, which the SSP will use to map into the WWW-authentication header in the SIP 401 unauthorized and send back to the HSP. When the subsequent SIP registration is received from the user, the HSP will once again contact the diameter server with a UAR to determine to which SSP to forward the registration. The HSP will then forward the SIP registration to the SSP node, which will then extract the relevant authentication parameters, and include these in a MAR message to the AAA server. This request MAY also serve to identify the SSP, so as to return subsequent registration requests to the same SSP. At this point, the Diameter server will be able to authenticate the user, and upon success, will return a MAA with Result-Code equal to DIAMETER_SUCCESS and include user profile information, which the SSP will use to give service to the user, the SSP will then produce a 200 (OK) message and send it to the HSP, which will then forward it to the mobile user. johansson et al. expires August 2002 [Page 11] INTERNET DRAFT Feb 2002 2.3 Single SIP server Some smaller networks where having more than one SIP server may be either cost-prohibitive, or simply unnecessary due a small number of services or users may decide to forgo the use of SSP nodes. In such a scenario, the gateway HSP node could provide the desired SIP services, using the AAA server as a back-end authentication server. +-------+ +-------+ | HSP | | AAA | +---+---+ +---+---+ | | 1. SIP-REG | | ---------->| 2. MAR | +------------------>| | 3. MAA | 4. 401 |<------------------+ <-----------+ | 5. SIP-REG | | ---------->| 6. MAR | +------------------>| | 7. MAA | 8. 200 |<------------------| <-----------+ | | | Figure 4: Networks with only a single SIP server (HSP) Again, steps 1-6 in this mode of operation are almost identical to those in section 2.3, with the exception that the MAR in this step 6 will also indicate that there are no other SIP servers in the network. If the AAA is able to successfully authenticate the user, it will then be able to directly associate the user with the HSP, and will not send a list of candidate SSPs in the MAA response. The HSP will then produce a 200 (OK) SIP message and send it to the user. 2.4 Invitation When a registered user wishes to invite another registered user, it will send a SIP Invite request to the home domain (HSP) of the invitee. johansson et al. expires August 2002 [Page 12] INTERNET DRAFT Feb 2002 +-------+ +-------+ +-------+ | HSP | | AAA | | SSP | +---+---+ +---+---+ +---+---+ | | | 1. SIP-INV | | | ---------->| 2. LIR | | +------------------>| | | 3. LIA | | |<------------------+ | | | 4. SIP-INV | +-------------------------------------->| | | | Figure 5. A SIP Invite request In this scenario, when a user, say Bob, contacts the HSP to invite another user, say Mary, the HSP will issue a diameter "Location-Info- Request" (LIR) message to the AAA server to request the identity of the SSP currently assigned to Mary. The AAA server will respond with a diameter "Location-Info-Answer" (LIA), indicating the appropriate SSP, and the HSP will forward the SIP Invite message directly to the named SSP. johansson et al. expires August 2002 [Page 13] INTERNET DRAFT Feb 2002 2.5 User Profile Updating Whenever a modification in the user profile has occurred, the AAA server and SSP must synchronize their user profile data. +-------+ +-------+ | AAA | | SSP | +---+---+ +---+---+ | | | 1. PUR | +------------------>| | | | 2. PUA | |<------------------+ | | Figure 6. User profile update initiated by AAA server The AAA server sends a Profile-Update-Request (PUR) to the serving SIP server to which the user is registered. The PUR message contains a SIP-User-Data AVP, a User-Name AVP, and zero or more SIP-Public- Identity AVPs. The presence of the User-Name AVP without any SIP- Public-Identity AVPs serves to indicate that the entire user profile associated with the User-Name AVP should be updated. A PUR with a User-Name AVP and one or more SIP-Public-Identity AVPs serves to indicate that the user profile data associated with each of the SIP- Public-Identity AVPs should be updated. If the user profile changes in the serving SIP server, the same message scheme is used, but is initiated by the serving SIP server (instead of the AAA server). 2.6 User registration termination Termination of an entire user registration can be achieved by one of two mechanisms. In the event that NO_STATE_MAINTAINED (i.e NO Diameter user session-id is maintained) has been indicated in a prior Auth-Session-State AVP, termination is handled with a Profile-Update- Request. On the other hand, if STATE_MAINTAINED has been indicated in a prior Auth-Session-State AVP, the use of Session-Termination-Request (STR) and Abort-Session-Request (ASR) messages as defined in the base protocol are used to terminate an entire user registration. Reasons for terminating a user registration could be due to the expiration of the SIP registration timer in the SIP server, a user initiated SIP de-registration, or a AAA-initiated de-registration as a result of administrative reasons. johansson et al. expires August 2002 [Page 14] INTERNET DRAFT Feb 2002 3.0 Command Codes This section will define the specific message formats used by this diameter application. 3.1 User-Authorization-Request (UAR) The User-Authorization-Request (UAR), indicated by the Command-Code field set to TBD and the 'R' bit set in the Command Flags field, is sent by a HSP node, acting as a Diameter client, to a AAA server in order to request authorization of a mobile user. Message Format < User-Authorization-Request > ::= < Diameter Header: TBD, REQ, PXY> < Session-ID > { Auth-Application-Id } { Auth-Session-State } { User-Name } { Destination-Realm } { Origin-Host } { Origin-Realm } { SIP-Server } [ SIP-Public-Identity ] [ SIP-Visited-Network-Identifier ] [ Authorization-Lifetime ] [ Auth-Grace-Period ] [ Destination-Host ] [ Origin-State-Id ] * [ AVP ] * [ Proxy-Info ] * [ Route-Record ] 3.2 User-Authorization-Answer (UAA) The User-Authorization-Answer (UAA), indicated by the Command-Code field set to TBD and the 'R' bit cleared in the Command Flags field, is sent by a AAA server in response to the User-Authorization-Request command. The Result-Code AVP may contain one of the values defined in section 4.0 in addition to the values defined in [2]. If the user has not previously been authorized, the UAA will make use of the SIP-User-Service-Info and SIP-Server AVPs to convey information needed by the HSP to select an appropriate SSP. If the user has already been authorized and a server has already been assigned which is still valid for the user's service profile, the johansson et al. expires August 2002 [Page 15] INTERNET DRAFT Feb 2002 SIP-Server AVP MUST be present which contains the SIP URL of the currently assigned server, so that the HSP can forward the registration request to it. If the user has already been authorized, and a server has already been assigned which may not be valid for the user's service profile, two pieces of information must be returned to allow the HSP to decide what action to take. First, the SIP-Server AVP MUST be present which contains the SIP URL of the currently assigned server. Second, the SIP-User-Service-Info AVP MUST present which contains information to allow the HSP to select an appropriate SIP server. Message Format < User-Authorization-Answer > ::= < Diameter Header: TBD, PXY > < Session-Id > { Auth-Application-Id } { Auth-Session-State } { Result-Code } { Origin-Host } { Origin-Realm } [ User-Name ] [ Accounting-Multi-Session-Id ] [ Authorization-Lifetime ] [ Auth-Grace-Period ] [ Error-Message ] [ Error-Reporting-Host ] [ SIP-User-Service-Info ] * [ SIP-Server ] * [ AVP ] * [ Proxy-Info ] * [ Route-Record ] 3.3 Multimedia-Auth-Request (MAR) The Multimedia-Auth-Request (MAR), indicated by the Command-Code field set to TBD and the 'R' bit set in the Command Flags field, is sent by a HSP node or SSP node, acting as a Diameter client, to a server in order to request the authentication and authorization of a mobile user. The Diameter client uses information found in the SIP Request to construct the AVPs that are to be included as part of the MAR. Message Format johansson et al. expires August 2002 [Page 16] INTERNET DRAFT Feb 2002 < Multimedia-Auth-Request > ::= < Diameter Header: TBD, REQ, PXY > < Session-ID > { Auth-Application-Id } { Auth-Session-State } { Destination-Realm } { Origin-Host } { Origin-Realm } { SIP-Server } [ User-Name ] [ SIP-Public-Identity ] [ SIP-Number-Auth-Items ] [ SIP-Auth-Data-Item ] [ Authorization-Lifetime ] [ Auth-Grace-Period ] [ Destination-Host ] [ Origin-State-Id ] * [ AVP ] * [ Proxy-Info ] * [ Route-Record ] 3.4 Multimedia-Auth-Answer (MAA) The Multimedia-Auth-Answer (MAA), indicated by the Command-Code field set to TBD and the 'R' bit cleared in the Command Flags field, is sent by the server in response to the Multimedia-Auth-Request command. johansson et al. expires August 2002 [Page 17] INTERNET DRAFT Feb 2002 Message Format < Multimedia-Auth-Answer > ::= < Diameter Header: TBD, PXY > < Session-Id > { Auth-Application-Id } { Auth-Session-State } { Result-Code } { Origin-Host } { Origin-Realm } [ SIP-User-Data ] [ User-Name ] [ Accounting-Multi-Session-Id ] [ Authorization-Lifetime ] [ Auth-Grace-Period ] [ Error-Message ] [ Error-Reporting-Host ] * [ SIP-Server ] [ SIP-Number-Auth-Items ] * [ SIP-Auth-Data-Item ] [ Session-Timeout ] [ Origin-State-Id ] * [ AVP ] * [ Proxy-Info ] * [ Route-Record ] 3.5 Profile-Update-Request The Profile-Update-Request (PUR) command, indicated by the Command- Code field set to TBD and the 'R' bit set in the Command Flags field, is sent in order to update or request the user profile data of a registered user. johansson et al. expires August 2002 [Page 18] INTERNET DRAFT Feb 2002 < Profile-Update-Request > ::= < Diameter Header: TBD, REQ, PXY > < Session-Id > { Auth-Application-Id } { Auth-Session-State } { Origin-Host } { Origin-Realm } { Destination-Realm } { SIP-Profile-Update-Type } [ Destination-Host ] [ User-Name ] [ SIP-User-Data ] [ SIP-Server ] [ SIP-Deregistration-Reason ] * [ SIP-Public-Identity ] * [ AVP ] * [ Proxy-Info ] * [ Route-Record ] 3.6 Profile-Update-Answer The Profile-Update-Answer (PUA) command, indicated by the Command- Code field set to TBD and the 'R' bit cleared in the Command Flags field, is sent in response to the Profile-Update-Request command. The Result-Code AVP may contain one of the values defined in section 4 in addition to the values defined in [2]. < Profile-Update-Answer > ::= < Diameter Header: TBD, PXY > < Session-Id > { Auth-Application-Id } { Auth-Session-State } { Result-Code } { Origin-Host } { Origin-Realm } [ SIP-User-Data ] [ User-Name ] * [ AVP ] * [ Proxy-Info ] * [ Route-Record ] johansson et al. expires August 2002 [Page 19] INTERNET DRAFT Feb 2002 3.7 Location-Info-Request (LIR) The Location-Info-Request (LIR), indicated by the Command-Code field set to TBD and the 'R' bit set in the Command Flags field, is sent by a HSP node, acting as a Diameter client, to a Diameter server in order to request the identity of SIP server currently associated with a particular user. Message Format < Location-Info-Request > ::= < Diameter Header: TBD, REQ, PXY > < Session-ID > { Auth-Application-Id } { Auth-Session-State } { Destination-Realm } { Origin-Host } { Origin-Realm } { SIP-Server } [ Destination-Host ] [ User-Name ] [ SIP-Public-Identity ] * [ AVP ] * [ Proxy-Info ] * [ Route-Record ] 3.8 Location-Info-Answer (LIA) The Location-Info-Answer (LIA), indicated by the Command-Code field set to TBD and the 'R' bit cleared in the Command Flags field, is sent by a Diameter server in response to a Location-Info-Request. If the user in the request is currently registered in the AAA server, the answer will include the identity of the SIP server currently associated with the user. Message Format johansson et al. expires August 2002 [Page 20] INTERNET DRAFT Feb 2002 < Location-Info-Answer > ::= < Diameter Header: TBD, PXY > < Session-Id > { Auth-Application-Id } { Auth-Session-State } { Result-Code } { Origin-Host } { Origin-Realm } [ User-Name ] [ Error-Message ] [ Error-Reporting-Host ] [ SIP-User-Service-Info ] * [ SIP-Server ] * [ AVP ] * [ Proxy-Info ] * [ Route-Record ] 4.0 Authentication Details Authenticating a mobile user can occur through various mechansims (http basic or digest authentication have currently been prescribed), with the actual authentication being performed in either the SIP server or the AAA server. The choice of which server will determine which AVPs will be utilized in the SIP-Auth-Data-Item grouped AVP, as well as a few AVPs in the MAR/MAA. In the event that the SIP server performs the authentication of a mobile user, the MAR from the SIP server to the AAA server will include the User-Name and SIP-Public-Identity AVPs as necessary, as well a SIP-Number-Auth-Items AVP to indicate how many authentication vectors (the actual contents of the vector are dependent upon the authentication method) are being requested. In the MAA, the AAA server SHOULD indicate how many SIP-Auth-Data-Item AVPs are present with the Number-Auth-Items AVP, and may be different from the amount requested in the MAR. If multiple SIP-Auth-Data-Item AVPs are present, and their ordering is significant, the Item-Number MUST be included in each grouping. The Authentication-Scheme and SIP- Authenticate AVPs will contain data (typically a challenge of some kind) to be used by the mobile user to authenticate itself. The SIP- Authorization AVP will contain the response which is expected from the user. In order to support some auth methods which combine key distribution with authentication, NAS-Session-Key AVPs may be included in the event they were requested by including "SIP crypto node" as one of the Server-Type AVPs in the MAR. In the event that the AAA server performs the authentication of a mobile user, the MAR from the SIP server will include a single SIP- Auth-Data-Item AVP. The SIP-Authentication-Scheme and SIP- johansson et al. expires August 2002 [Page 21] INTERNET DRAFT Feb 2002 Authorization AVPs will contain the relevant parameters from the SIP message if present, and if necessary, the SIP-Authentication-Context AVP will contain any additional information needed to perform the authentication. If the authentication is successful, the MAA will contain a result code indicating success, and if necessary, the SIP- Auth-Data-Item AVP may be included to carry session keys back to the SIP server. If the authentication is unsuccessful due to missing credentials, the MAA will include an SIP-Auth-Data-Item with the SIP- Authentication-Scheme and SIP-Authenticate AVPs containing data (typically a challenge of some kind) to be used by the mobile user to authenticate itself. 5.0 Result Code AVP values This section defines new Result codes in addition to the values defined in [2]. 5.1 Success Errors that fall within the Success category are used to inform a peer that a request has been successfully completed. DIAMETER_FIRST_REGISTRATION 2xxx The user was not previously registered, and has now been authorized by the AAA server. Information necessary to select an appropriate SSP SHOULD be included in the message. DIAMETER_SUBSEQUENT_REGISTRATION 2xxx The user has been previously registered, and has now been re- authorized by the AAA server. The identity of the SSP to which the user is currently registered SHOULD by included in the message. DIAMETER_SEPARATE_REGISTRATION 2xxx The user has been previously registered, but with a different public identifier (and associated service profile). The identity of the SSP to which the user is currently registered MUST be included in the message, and in the event a new SSP must be assigned (based on the new service profile), information necessary to select an appropriate SSP MUST be included in the message as well. DIAMETER_UNREGISTERED_SERVICE 2xxx The user is not currently registered, but the requested service can still be granted to the user. 5.2 Permanent failures johansson et al. expires August 2002 [Page 22] INTERNET DRAFT Feb 2002 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_ERROR_ROAMING_NOT_ALLOWED 5xxx This error code is used to indicate that there is no multimedia roaming agreement between the home and visited networks. DIAMETER_ERROR_IDENTITY_ALREADY_REGISTERED 5xxx The identity being registered has already a server assigned and the registration status does not allow that it is overwritten. DIAMETER_ERROR_IDENTITY_NOT_REGISTERED 5xxx This error code is used to inform that the received public identity has not been registered before and the user to which this identity belongs cannot be given service in this situation. DIAMETER_ERROR_IDENTITIES_DONT_MATCH 5xxx The value in one of the Public-Identity AVPs does not correspond to the user specified in the User-Name AVP. 6.0 Diameter AVP values The following sections define the AVPs used in this diameter application. 6.1 SIP-Server AVP The SIP-Server AVP (AVP code TBD) is of type Grouped. This AVP MAY be used by the HSP to assist in the selection of a SSP. SIP-Server ::= < AVP Header: TBD > { SIP-Server-Name } * [ SIP-Server-Type ] * [ SIP-Capability ] * [ AVP ] 6.2 SIP-Server-Name AVP The SIP-Server-Name AVP (AVP Code TBD) is of type UTF8String. This AVP contains a SIP-URL (as defined in [5] and [6]) used to identify a SIP server. The HSP MAY include the SIP-Server-Name AVP to inform the Diameter server which SSP to use for the SIP user or the SIP-Server-Name AVP MAY be used by the Diameter server to inform the HSP that the SIP UA client is assigned at the following SSP server. johansson et al. expires August 2002 [Page 23] INTERNET DRAFT Feb 2002 6.3 SIP-Capability AVP The SIP-Capability AVP (AVP Code TBD) is of type Grouped. This AVP is used to indicate support for particular SIP capability. SIP-Capability ::= < AVP Header: TBD > { SIP-Capability } { SIP-Capability-Type } [ Vendor-ID ] [ SIP-Version-Number ] * [ SIP-Optional-Parameter ] * [ AVP ] A Vendor-ID value of 0, or the absence of a Vendor-ID AVP implies that the value indicated by the SIP-Capability AVP has been assigned by IANA to represent a non-vendor specific capability. Otherwise, the value indicated by the SIP-Capability AVP is defined entirely by the vendor/operator. 6.4 SIP-Public-Identity AVP The SIP-Public-Identity AVP (AVP Code TBD) is of type OctetString, encoded in the UTF-8 [9] format. The syntax of this AVP corresponds either to a SIP URL (with the format defined in [5] and [6]) or a TEL URL (with the format defined in [7]). The Diameter client (HSP or SSP) uses information found in the header of the SIP messages (e.g. To: field in REGISTER messages or From: field in INVITE messages) to construct the SIP-Public-Identity AVP. 6.5 SIP-Visited-Network-Identifier AVP The SIP-Visited-Network-Identifier AVP (AVP Code TBD) is of type OctetString. This AVP contains an identifier that helps the home network to identify the visited network (e.g. the visited network domain name). 6.6 SIP-Profile-Update-Type AVP The SIP-Profile-Update-Type AVP (AVP code TBD) is of type Enumerated, and indicates the type of server update being performed in a Profile- Update-Request operation. The following values are defined: NO_ASSIGNMENT 0 REGISTRATION 1 RE_REGISTRATION 2 UNREGISTERED_USER 3 TIMEOUT_DEREGISTRATION 4 johansson et al. expires August 2002 [Page 24] INTERNET DRAFT Feb 2002 USER_DEREGISTRATION 5 AUTHENTICATION_FAILURE 6 UPDATE_PROFILE 7 RETRIEVE_PROFILE 8 ADMINISTRATIVE_DEREGISTRATION 9 6.7 SIP-Server-Type AVP The SIP-Server-Type AVP (AVP Code TBD) is of type Enumerated, and the value is used to identify a particular type of SIP server. The following values have currently been defined. Stateless proxy 0 This SIP server is a stateless proxy (e.g., HSP), and is only interested in routing the SIP method to the proper SSP. It will not participate in authentication, but may also use e.g., 4 below. Registrar 1 This SIP server is a registrar (e.g., SSP or in some cases HSP). It wants to run authentication, but will use the AAA server to check authenticated results (no secrets given to SSP). Authenticating registrar 2 This SIP server is a registrar, and wants to run authentication, including performing the check of authenticated results itself (values such as challenges and expected responses are given to the SSP). SIP hub 3 This SIP server wants to download a set of filter criteria/AS names for subsequent routing of INVITEs and other messages. SIP crypto node 4 This SIP server wants access to NAS-Session-Key data so that it can verify/decrypt subsequent SIP messages. 6.8 SIP-Authentication-Scheme AVP The SIP-Authentication-Scheme AVP (AVP code TBD) is of type UTF8String and indicates the authentication scheme used in the authentication of SIP messages. Current values are "Basic" and "Digest", defined in [8]. 6.9 SIP-Authenticate AVP The SIP-Authenticate AVP (AVP code TBD) is of type UTF8String and contains the data portion of the WWW-Authenticate or Proxy- Authenticate SIP headers if present in a SIP response. johansson et al. expires August 2002 [Page 25] INTERNET DRAFT Feb 2002 6.10 SIP-Authorization AVP The SIP-Authorization AVP (AVP code TBD) is of type UTF8String and contains the data portion of the Authorization or Proxy-Authorization SIP headers if present in a SIP request. 6.11 SIP-Authentication-Context AVP The SIP-Authentication-Context AVP (AVP code TBD) is of type OctectString, and contains authentication-related information relevant for performing the authentication but that is not part of the SIP authentication headers. Some mechanisms (e.g. PGP, digest with quality of protection set to auth-int [RFC 2617], digest with predictive nonces [7] or sip access digest [8]) request that part or the whole SIP request is passed to the entity performing the authentication. In such cases the SIP- Authentication-Context AVP would be carrying such information. 6.12 SIP-Number-Auth-Items AVP The SIP-Number-Auth-Items AVP (AVP Code TBD) is of type Unsigned32 and indicates the number of authentication and/or authorization vectors provided by the Diameter server. When used in a request, it indicates the number of SIP-Auth-Data- Items the SSP is requesting. This can be used, for instance, when the SSP is requesting several pre-calculated authentication vectors. In the answer message the SIP-Number-Auth-Items AVP indicates the actual number of items provided by the Diameter server. 6.13 SIP-Auth-Data-Item AVP The SIP-Auth-Data-Item (AVP code TDB) is of type Grouped, and contains the authentication and/or authorization information for the Diameter client. SIP-Auth-Data-Item :: = < AVP Header : TBD > [ SIP-Item-Number ] [ SIP-Authentication-Scheme ] [ SIP-Authenticate ] [ SIP-Authorization ] [ SIP-Authentication-Context ] * [ NAS-Session-Key ] * [ AVP ] 6.14 SIP-Item-Number AVP johansson et al. expires August 2002 [Page 26] INTERNET DRAFT Feb 2002 The SIP-Item-Number (AVP code TDB) is of type Unsigned32, and is included in a SIP-Auth-Data-Item grouped AVP in circumstances where there are multiple occurrences of SIP-Auth-Data-Item AVPs, and the order in which they should be processed is significant. In this scenario, SIP-Auth-Data-Item AVPs with a low SIP-Item-Number value (such as 1) should be processed before SIP-Auth-Data-Items AVPs with a high SIP-Item-Number value (such as 13). 6.15 SIP-User-Data AVP The SIP-User-Data AVP (AVP Code TBD) is of type OctetString, and MUST NOT be interpreted by the Diameter protocol. This AVP contains the user profile data required for a SIP server to give service to a user. 6.16 NAS-Session-Key AVP The NAS-Session-Key AVP is defined in [3]. 6.17 NAS-Key-Binding AVP The NAS-Key-Binding AVP is defined in [3]. 6.18 SIP-User-Service-Info AVP The SIP-User-Service-Info AVP (AVP code TBD) is of type Grouped. This AVP is used to communicate two different types of information. First, a list of capabilities that are either required or preferable in order for a SIP server to grant service to a user. Second, a list of default servers (indicated in the user's service profile) which may be used to service the user. An HSP will be able to select an appropriate SSP with these two lists of information. Message format SIP-User-Service-Info ::= < AVP Header: TBD > * [ SIP-Capability ] * [ SIP-Server-Name ] * [ AVP ] 6.19 SIP-Deregistration-Reason AVP The SIP-Deregistration-Reason AVP (AVP Code TBD) is of type Grouped, and indicates the reason for a deregistration operation. johansson et al. expires August 2002 [Page 27] INTERNET DRAFT Feb 2002 Message format SIP-Deregistration-Reason::= < AVP Header: TBD > * [ SIP-Reason ] * [ SIP-Server-Behavior ] * [ AVP ] 6.20 SIP-Capability AVP The SIP-Capability AVP (AVP Code TBD) is of type Unsigned32, and is used to represent a particular capability of a SIP server. 6.21 SIP-Version-Number AVP The SIP-Version-Number AVP (AVP Code TBD) is of type Unsigned32. This AVP is used within a SIP-Capability AVP, and indicates support for a particular version of the capability indicated within the same SIP-Capability AVP. 6.22 Vendor-ID AVP The Vendor-ID AVP is defined in [2]. 6.23 SIP-Optional-Parameter AVP The SIP-Optional-Parameter AVP (AVP Code TBD) is of type OctetString. The value included in this AVP MUST not be interpreted by the Diameter protocol, and is simply passed as opaque data to SIP servers. 6.24 SIP-Capability-Type AVP The SIP-Capability-Type AVP (AVP Code TBD) is of type Enumerated, and specifies the type of capability. The following values are defined. MANDATORY 1 The capability MUST be supported by a server in order to be considered for providing SIP services to a user OPTIONAL 2 This capability MAY be supported by a server in order to be considered for providing SIP services to a user INFORMATIONAL 3 This capability is supported by a SIP server 6.25 SIP-Reason AVP johansson et al. expires August 2002 [Page 28] INTERNET DRAFT Feb 2002 The SIP-Reason AVP (AVP code TBD) is of type UTF8String, and contains textual information to inform the user about the reason for a de- registration. 6.26 SIP-Server-Behavior AVP The SIP-Server-Behaviour AVP (AVP code TBD) is of type Enumerated, and defines the reason for the network initiated de-registration. The following values are defined: PERMANENT_TERMINATION 0 The IMS subscription or service profile(s) has been permanently terminated. The SSP should start the network initiated de- registration towards the user. NEW_SERVER_ASSIGNED 1 A new SSP has been allocated to the user due to some reason, e.g. an error case, where the SIP registration is terminated in a new SSP. The SSP shall not start the network initiated de- registration towards the user but only clears its registration state and information regarding the user, i.e. all service profiles are cleared. 7.0 References [1] Basilier, Calhoun, Holdrege, Johansson, Kempf, Rajaniemi, "AAA Requirements for IP Telephony/Multimedia", draft-calhoun-sip-aaa- reqs-03.txt, IETF work in progress, October 2001 [2] Calhoun, Akhtar, Arkko, Guttman, Rubens, Zorn, "Diameter Base Pro­ tocol", draft-ietf-aaa-diameter-08.txt, IETF work in progress, November 2001 [3] Calhoun, Bulley, Rubens, Haag, Zorn, "Diameter NASREQ Application", draft-ietf-aaa-diameter-nasreq-08.txt, IETF work in progress, November 2001 [4] Calhoun, Perkins, "Diameter Mobile IPv4 Application," draft-ietf- diameter-mobileip-07.txt, IETF work in progress, November 2001. [5] M. Handley, H. Schulzrinne, E. Schooler, J. Rosenberg, "SIP: Ses­ sion Initiation Protocol". RFC 2543, March 1999. [6] IETF RFC 2396: "Uniform Resource Identifiers (URI): generic syntax" [7] IETF RFC 2806: "URLs for Telephone Calls" johansson et al. expires August 2002 [Page 29] INTERNET DRAFT Feb 2002 [8] IETF RFC 2617: "HTTP Authentication: Basic and Digest Access Authentication" 8.0 Authors' Addresses Questions about this memo can be directed to: Tony Johansson Ericsson Inc. 2100 Shattuck Ave. Berkeley, Califonia, 94704 USA Phone: +1 510-305-6108 Fax: +1 510-666-3999 E-mail: tony.johansson@ericsson.com Kevin Purser Ericsson Inc. 2100 Shattuck Ave. Berkeley, Califonia, 94704 USA Phone: +1 510-305-6100 Fax: +1 510-666-3999 E-mail: kevin.purser@ericsson.com Carolina Canales Ericsson Spain C/ Ombu, 3 28045 Madrid Spain Phone: +34 913392680 Fax: +34 913392538 E-mail: carolina.canales-valenzuela@ece.ericsson.se Miguel-Angel Pallares Ericsson Spain C/ Ombu, 3 28045 Madrid Spain Phone: +34 913394222 Fax: +34 913392538 E-mail: miguel-angel.pallares-lopez@ece.ericsson.se johansson et al. expires August 2002 [Page 30] INTERNET DRAFT Feb 2002 Peter J. McCann Lucent Technologies Rm 2Z-305 263 Shuman Blvd Naperville, IL 60566-7050 USA Phone: +1 630 713 9359 Fax: +1 630 713 4982 E-Mail: mccap@lucent.com Jaakko Rajaniemi Nokia Networks P.O. Box 301 00045 Nokia Group Finland Phone: +358 50 3391387 Fax: +358 9 51130163 E-mail: jaakko.rajaniemi@nokia.com 9.0 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. johansson et al. expires August 2002 [Page 31]