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IETF RFC 4740
Diameter Session Initiation Protocol (SIP) Application
Last modified on Wednesday, November 22nd, 2006
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Network Working Group M. Garcia-Martin, Ed.
Request for Comments: 4740 Nokia
Category: Standards Track M. Belinchon
M. Pallares-Lopez
C. Canales-Valenzuela
Ericsson
K. Tammi
Nokia
November 2006
Diameter Session Initiation Protocol (SIP) Application
 Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright © The IETF Trust (2006).
Abstract
This document specifies the Diameter Session Initiation Protocol
(SIP) application. This is a Diameter application that allows a
Diameter client to request authentication and authorization
information. This application is designed to be used in conjunction
with SIP and provides a Diameter client co-located with a SIP server,
with the ability to request the authentication of users and
authorization of SIP resources usage from a Diameter server.
Garcia-Martin, et al. Standards Track PAGE 1 
RFC 4740 Diameter SIP Application November 2006
Table of Contents
1. Introduction ....................................................4
2. Terminology .....................................................5
3. Definitions .....................................................5
4. Acronyms ........................................................6
5. Applicability Statement .........................................6
6. Overview of Operation ...........................................7
6.1. General Architecture .......................................7
6.2. Diameter Server Authenticates the User .....................9
6.3. Delegating Final Authentication Check to the SIP Server ...12
6.4. SIP Server Requests Authentication and Authorization ......15
6.5. Locating the Recipient of the SIP Request .................16
6.6. Update of the User Profile ................................17
6.7. SIP Soft State Termination ................................18
6.8. Diameter Server Discovery .................................19
7. Advertising Application Support ................................21
8. Diameter SIP Application Command Codes .........................22
8.1. User-Authorization-Request (UAR) Command ..................22
8.2. User-Authorization-Answer (UAA) Command ...................23
8.3. Server-Assignment-Request (SAR) Command ...................27
8.4. Server-Assignment-Answer (SAA) Command ....................29
8.5. Location-Info-Request (LIR) Command .......................33
8.6. Location-Info-Answer (LIA) Command ........................33
8.7. Multimedia-Auth-Request (MAR) Command .....................35
8.8. Multimedia-Auth-Answer (MAA) Command ......................36
8.9. Registration-Termination-Request (RTR) Command ............39
8.10. Registration-Termination-Answer (RTA) Command ............39
8.11. Push-Profile-Request (PPR) Command .......................41
8.12. Push-Profile-Answer (PPA) Command ........................42
9. Diameter SIP Application AVPs ..................................44
9.1. SIP-Accounting-Information AVP ............................46
9.1.1. SIP-Accounting-Server-URI AVP ......................47
9.1.2. SIP-Credit-Control-Server-URI AVP ..................47
9.2. SIP-Server-URI AVP ........................................47
9.3. SIP-Server-Capabilities AVP ...............................47
9.3.1. SIP-Mandatory-Capability AVP .......................48
9.3.2. SIP-Optional-Capability AVP ........................48
9.4. SIP-Server-Assignment-Type AVP ............................48
9.5. SIP-Auth-Data-Item AVP ....................................50
9.5.1. SIP-Authentication-Scheme AVP ......................50
9.5.2. SIP-Item-Number AVP ................................51
9.5.3. SIP-Authenticate AVP ...............................51
9.5.4. SIP-Authorization AVP ..............................52
9.5.5. SIP-Authentication-Info AVP ........................52
9.5.6. Digest AVPs ........................................53
9.6. SIP-Number-Auth-Items AVP .................................55
Garcia-Martin, et al. Standards Track PAGE 2
RFC 4740 Diameter SIP Application November 2006
9.7. SIP-Deregistration-Reason AVP .............................55
9.7.1. SIP-Reason-Code AVP ................................55
9.7.2. SIP-Reason-Info AVP ................................56
9.8. SIP-AOR AVP ...............................................56
9.9. SIP-Visited-Network-Id AVP ................................56
9.10. SIP-User-Authorization-Type AVP ..........................56
9.11. SIP-Supported-User-Data-Type AVP .........................57
9.12. SIP-User-Data AVP ........................................57
9.12.1. SIP-User-Data-Type AVP ............................58
9.12.2. SIP-User-Data-Contents AVP ........................58
9.13. SIP-User-Data-Already-Available AVP ......................58
9.14. SIP-Method AVP ...........................................59
10. New Values for Existing AVPs ..................................59
10.1. Extension to the Result-Code AVP Values ..................59
10.1.1. Success Result-Code AVP Values ....................59
10.1.2. Transient Failures Result-Code AVP Values .........60
10.1.3. Permanent Failures Result-Code AVP Values .........60
11. Authentication Details ........................................61
12. Migration from RADIUS .........................................63
12.1. Gateway from RADIUS Client to Diameter Server ............63
12.2. Gateway from Diameter Client to RADIUS Server ............63
12.3. Known Limitations ........................................64
13. IANA Considerations ...........................................64
13.1. Application Identifier ...................................64
13.2. Command Codes ............................................65
13.3. AVP Codes ................................................65
13.4. Additional Values for the Result-Code AVP Value ..........65
13.5. Creation of the SIP-Server-Assignment-Type
Section in the AAA .......................................66
13.6. Creation of the SIP-Authentication-Scheme Section
in the AAA ...............................................66
13.7. Creation of the SIP-Reason-Code Section in the
AAA Registry .............................................66
13.8. Creation of the SIP-User-Authorization-Type
Section in the AAA .......................................66
13.9. Creation of the SIP-User-Data-Already-Available
Section in the ...........................................66
14. Security Considerations .......................................67
14.1. Final Authentication Check in the Diameter
Client/SIP Server ........................................67
15. Contributors ..................................................68
16. Acknowledgements ..............................................68
17. References ....................................................68
17.1. Normative References .....................................68
17.2. Informative References ...................................69
Garcia-Martin, et al. Standards Track PAGE 3
RFC 4740 Diameter SIP Application November 2006
1. Introduction
This document specifies the Diameter Session Initiation Protocol
(SIP) application. This is a Diameter application that allows a
Diameter client to request authentication and authorization
information to a Diameter server for SIP-based IP multimedia services
(see [RFC 3261] about SIP). Furthermore, this Diameter SIP
application provides the Diameter client with functions that go
beyond the typical authorization and authentication, such as the
ability to download or receive updated user profiles, or rudimentary
routing functions that can assist a SIP server in finding another SIP
server allocated to the user.
We assume that the SIP server (such as SIP proxy server, registrar,
redirect server, or alike) and the Diameter client are co-located in
the same node, so that the SIP server is able to receive and process
SIP requests and responses. In turn, the SIP server relies on the
Authentication, Authorization, and Accounting (AAA) infrastructure
for authenticating the SIP request and authorizing the usage of
particular SIP services.
This document provides Diameter procedures to implement certain
required functionality when SIP is the protocol chosen to initiate
and tear down multimedia sessions or when SIP is used for other
non-session-related applications. However, this document does not
mandate any particular mapping of SIP procedures to Diameter SIP
application procedures, nor does it mandate any particular sequence
of events between SIP and Diameter. This document provides useful
examples to show the interaction between SIP and the Diameter SIP
application in order to achieve the desired functionality.
This application does not require and is not related to other
authentication services provided by the Diameter Mobile IPv4
[RFC 4004] or the Diameter Network Access Server [RFC 4005]
applications.
This Diameter SIP application is loosely related to the Diameter
credit-control application [RFC 4006]. Although both applications are
independent, the Diameter SIP application is able to supply the
addresses of credit-control servers that will be implementing the
Diameter credit-control application [RFC 4006].
Section 5 discusses assumptions and configurations assumed by this
document.
Section 6 provides the reader with informative descriptions of the
Diameter SIP application commands and responses and with some
guidance about their linkage with SIP procedures.
Garcia-Martin, et al. Standards Track PAGE 4
RFC 4740 Diameter SIP Application November 2006
Advertisement of this application is specified in Section 7.
Section 8 provides a normative description of all the new Diameter
commands defined by this specification.
This application extends the Result-Code Attribute-Value-Pair (AVP)
with some new values. Further information is described in
Section 10.
This application defines some new AVPs. All these AVPs are described
in Section 9.
Some extra information about authentication is provided in
Section 11.
2. Terminology
In this document, the key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT
RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as
described in BCP 14, RFC 2119 [RFC 2119] and indicate requirement
levels for compliant implementations.
3. Definitions
For the purpose of this document, the following terms and definitions
apply:
Node: an addressable device attached to a computer network that
implements SIP functionality, Diameter functionality, or a
combination of both.
For the purpose of this document, the following terms and definitions
given in RFC 3261 [RFC 3261] Section 6, apply:
o Address-of-Record (AOR)
o Outbound proxy
o Proxy
o Registrar
o Server (SIP server)
o User Agent (UA)
o User Agent Client (UAC)
o User Agent Server (UAS)
For the purpose of this document, the following terms and definitions
given in RFC 3588 [RFC 3588] Section 1.3, apply:
Garcia-Martin, et al. Standards Track PAGE 5
RFC 4740 Diameter SIP Application November 2006
o Authorization
o Authentication
o Attribute-Value Pair (AVP)
o Diameter Client
o Diameter Server
o Home Realm
o Redirect Agent
o User
4. Acronyms
AKA: Authentication and Key Agreement
LIR: Location-Info-Request
LIA: Location-Info-Answer
MAR: Multimedia-Auth-Request
MAA: Multimedia-Auth-Answer
PPR: Push-Profile-Request
PPA: Push-Profile-Answer
RTR: Registration-Termination-Request
RTA: Registration-Termination-Answer
SAR: Server-Assignment-Request
SAA: Server-Assignment-Answer
SL: Subscriber Locator
UAR: User-Authorization-Request
UAA: User-Authorization-Answer
5. Applicability Statement
This document assumes a general architecture where a Home Realm is
composed of one or more nodes implementing Diameter or SIP functions.
Users are issuing SIP requests to access SIP resources. For each
particular user, the Home Realm needs to authenticate and authorize
the usage of those resources and/or the route to the appropriate
node. We assume that the database containing the user-related data
is located outside the SIP node that requires authorization. Data
belonging to different users may be stored in different nodes in the
Home Realm, but we assume that all the data related to a particular
user is stored in a single node.
Note: Central to the architecture is the fact that the user data
is stored in a single point in the network. This restriction does
not mandate a particular implementation, e.g., it is possible to
implement clusters of databases operating in mirror mode to
provide redundancy. The property required by this specification
is that the user data the Diameter server has access to is stored
safely in what is seen, from the external point of view, as a
single user database.
Garcia-Martin, et al. Standards Track PAGE 6
RFC 4740 Diameter SIP Application November 2006
This document allows several configurations of the Home Realm. In
one configuration, a SIP server (proxy, registrar, etc.) is allocated
to a user for the purpose of triggering and executing services. The
allocation of the SIP server may be done dynamically, e.g., at the
time the user registers in the network. This configuration requires
a SIP server, typically located at the edge of the network, that is
able to allocate another SIP server for the user and that also
supports routing of SIP requests and responses towards that allocated
SIP server. Both SIP server nodes implement a Diameter client.
In another configuration, the address of a SIP outbound proxy is
configured (by means outside the scope of this specification) into
the SIP User Agent. The outbound Diameter client in the SIP outbound
proxy node authenticates the user, requests authorization for SIP
requests, and performs accounting activities.
6. Overview of Operation
This section provides an informative description of how the Diameter
SIP application can be used together with SIP. This section is not
intended to mandate any specific usage of the Diameter SIP
application nor does it mandate a specific mapping between SIP and
Diameter messages. We provide a collection of examples that show how
the required AAA functionality can be achieved in conjunction with
SIP.
6.1. General Architecture
The Diameter SIP application can be used in a SIP environment where
an interface to a AAA infrastructure is required to authenticate and
authorize the usage of SIP resources. This application provides
support for SIP User Agents and proxies that implement and use HTTP
Digest authentication [RFC 2617], which is the authentication
mechanism mandated by SIP [RFC 3261]. The application is extensible
and, if need arises, it can be extended to provide support for other
authentication mechanisms or extensions to HTTP Digest authentication
when they occur.
This application provides limited support for accounting services as
follows: the Diameter server is able to provide the addresses of
accounting severs to the Diameter client. Figure 1, below, shows a
general overview of the integration of the SIP architecture with the
AAA architecture.
According to Figure 1, there are one or more SIP User Agents (UAs)
that initiate or terminate SIP traffic through one or more SIP
servers. Both SIP servers implement a Diameter client that supports
the Diameter application described in this specification.
Garcia-Martin, et al. Standards Track PAGE 7
RFC 4740 Diameter SIP Application November 2006
+--------+
UAR/UAA +--->|Diameter|<----+ PPR/PPA
LIR/LIA | | server | | MAR/MAA
| +--------+ | SAR/SAA
| | RTR/RTA
| |
v v
+------+ SIP +--------+ SIP +--------+ SIP +------+
| SIP |<--------->| SIP |<-------->| SIP |<--------->| SIP |
| UA | |server 1| |server 2| | UA |
+------+ +--------+ +--------+ +------+
^ ^
UAR/UAA | |
LIR/LIA | | MAR/MAA
| +--------+ | SAR/SAA
+--->|Diameter|<----+
| SL |
+--------+
Figure 1: Architecture of the Diameter application for SIP
In Figure 1, it can be seen that SIP server 1 sends different
Diameter commands and receives different responses than those sent
and received by SIP server 2. This is because SIP server 1 in
Figure 1 is located at the edge of a network, and its main task is to
locate SIP server 2. SIP server 2 is requesting and receiving
authentication and authorization data from the Diameter server and is
not located at the edge of the network.
This Diameter application assumes that all the data pertaining to a
given user is stored in a single Diameter server. For redundancy
purposes, several Diameter servers can be configured in a redundancy
fashion, in which case all of them keep the data synchronized and
operate externally as a single Diameter server.
With respect to SIP server 1 in Figure 1, the Diameter SIP
application provides support for the existence of a farm of these
servers, typically configured through one or more DNS records that
point to several hosts (this is a typical configuration in common SIP
deployments). There is no requirement for these types of servers to
keep state related to the Diameter SIP application.
The Diameter SIP application provides support for a feature that
allows an administrative domain to provide a collection of SIP
servers 2 (as per Figure 1). Once the user registers for the first
time, one of these SIP servers is selected and all the SIP requests
related to the user are processed by the same SIP server.
Garcia-Martin, et al. Standards Track PAGE 8
RFC 4740 Diameter SIP Application November 2006
The Diameter Subscriber Locator (SL) serves the purpose of locating
the Diameter server that contains the user-related data. Its
functionality is based on the Diameter redirect mechanism and is
further described in Section 6.8.
It should be noted that this document does not mandate any particular
SIP/AAA architecture. However, the Diameter SIP application provides
the functionality needed to accommodate all the different
architectures where SIP and Diameter are used.
The following subsections provide an informative overview of the
Diameter SIP application, its commands, and a possible interaction
with SIP signaling.
6.2. Diameter Server Authenticates the User
This is the generic mechanism to authenticate users. In this
approach, we show an example of an administrative network where the
Diameter server is authenticating SIP user requests. This could be
the case of a medium-size network where the Diameter server is
keeping user records and authenticating SIP requests to perform a
certain transaction. We have chosen to show a SIP REGISTER request
in the example, but the SIP server could request authentication of
any other SIP request.
Garcia-Martin, et al. Standards Track PAGE 9
RFC 4740 Diameter SIP Application November 2006
+--------+ +--------+ +--------+
| SIP | |Diameter| | SIP |
|server 1| | server | |server 2|
+--------+ +--------+ +--------+
| | |
1. SIP REGISTER | | |
-------------------->| 2. UAR | |
|------------------>| |
| 3. UAA | |
|<------------------| |
| 4. SIP REGISTER |
|-------------------------------------->|
| | 5. MAR |
| |<------------------|
| | 6. MAA |
| |------------------>|
| 7. SIP 401 (Unauthorized) |
8. SIP 401 (Unauth.) |<--------------------------------------|
<--------------------| | |
9. SIP REGISTER | | |
-------------------->| 10. UAR | |
|------------------>| |
| 11. UAA | |
|<------------------| |
| 12. SIP REGISTER |
|-------------------------------------->|
| | 13. MAR |
| |<------------------|
| | 14. MAA |
| |------------------>|
| 15. SIP 200 (OK) |
16. SIP 200 (OK) |<--------------------------------------|
<--------------------| | |
| | 17. SAR |
| |<------------------|
| | 18. SAA |
| |------------------>|
| | |
Figure 2: Authentication performed in the Diameter server
According to Figure 2, a SIP User Agent Client (UAC) sends a SIP
REGISTER request (step 1) to SIP server 1, which receives the SIP
request. In Figure 2, we assume that this SIP server is located at
the edge of the administrative home domain. The Diameter client in
SIP server 1 contacts its Diameter server by sending a Diameter
User-Authorization-Request (UAR) message (step 2) to determine if
this user is allowed to receive service, and if so, request the
Garcia-Martin, et al. Standards Track PAGE 10
RFC 4740 Diameter SIP Application November 2006
address of a local SIP server capable of handling this user. The
Diameter server answers with a Diameter User-Authorization-Answer
(UAA) message (step 3), which indicates a list of capabilities that
SIP server 1 may use to select an appropriate SIP server (SIP server
2) and/or a SIP or SIPS URI pointing to SIP server 2.
SIP server 1 forwards the SIP REGISTER request (step 4) to an
appropriate SIP server (SIP server 2). Then the Diameter client in
SIP server 2 requests user authentication from the Diameter server by
sending a Diameter Multimedia-Auth-Request (MAR) message (step 5).
This request also serves to make the Diameter server aware of the SIP
or SIPS URI of SIP server 2, so as to return subsequent requests for
the same user to the same SIP server 2. The Diameter server responds
with a Diameter Multimedia-Auth-Answer (MAA) message (step 6) with
Result-Code AVP set to the value DIAMETER_MULTI_ROUND_AUTH. The
Diameter server also generates a nonce and includes a challenge in
the MAA message. SIP server 2 uses that challenge to map into the
WWW-Authenticate header in the SIP 401 (Unauthorized) response (step
7), which is sent back to SIP server 1 and then to the SIP UAC (step
8).
SIP server 1 receives a next SIP REGISTER request containing the user
credentials (step 9). Note that SIP server 1 does not need to keep a
state, and even more, there is no guarantee that the SIP request
arrives at the same SIP server 1; there could be a farm of SIP
servers 1 operating in redundant configuration. The Diameter client
in SIP server 1 contacts the Diameter server by sending a Diameter
UAR message (step 10) to determine the SIP server allocated to the
user. The Diameter server sends the SIP or SIPS URI of SIP server 2
in a Diameter UAA message (step 11).
Then SIP server 1 forwards the SIP REGISTER request to SIP server 2
(step 12). SIP server 2 extracts the credentials from the SIP
REGISTER request. The Diameter client in SIP server 2 sends those
credentials in a Diameter MAR message (step 13) to the Diameter
server. At this point, the Diameter server is able to authenticate
the user, and upon success, returns a Diameter MAA message (step 14)
with the AVP Result-Code set to the value DIAMETER_SUCCESS.
Then SIP server 2 generates a SIP 200 (OK) response (step 15), which
is forwarded to SIP server 1 and eventually to the SIP UAC (step 16).
If the Diameter client in SIP server 2 is interested in downloading
the user profile information or is required to store the address of
the SIP server in the Diameter server, then the Diameter client sends
a Diameter SAR message (step 17) to the Diameter server. The
Diameter server replies with a Diameter SAA message (step 18) that
contains the requested user profile information and the
Garcia-Martin, et al. Standards Track PAGE 11
RFC 4740 Diameter SIP Application November 2006
acknowledgement of the SIP server address storage. These actions are
needed when the SIP server has to retrieve a user profile used to
provide services to the served user, or when the SIP server keeps a
state for the user, so the Diameter server needs to store the SIP
server's address.
6.3. Delegating Final Authentication Check to the SIP Server
An operator with a large base of installed SIP servers may wish to
minimize the number of round-trips between the Diameter client and
the Diameter server. We provide support for a mechanism where the
Diameter server delegates the final authentication check to the SIP
server, thereby saving a round-trip. Section 14.1 discusses the
security considerations of this scenario.
It must noted that this scenario is not applicable when the Diameter
server is configured to use a session MD5 (MD5-sess) algorithm,
because the Diameter server requires the client nonce to compute the
H(A1) before sending it to the Diameter client. However, the client
nonce might not be available at that time.
Garcia-Martin, et al. Standards Track PAGE 12
RFC 4740 Diameter SIP Application November 2006
+--------+ +--------+ +--------+
| SIP | |Diameter| | SIP |
|server 1| | server | |server 2|
+--------+ +--------+ +--------+
| | |
1. SIP REGISTER | | |
-------------------->| 2. UAR | |
|------------------>| |
| 3. UAA | |
|<------------------| |
| 4. SIP REGISTER |
|-------------------------------------->|
| | 5. MAR |
| |<------------------|
| | 6. MAA |
| |------------------>|
| 7. SIP 401 (Unauthorized) |
8. SIP 401 (Unauth.) |<--------------------------------------|
<--------------------| | |
9. SIP REGISTER | | |
-------------------->| 10. UAR | |
|------------------>| |
| 11. UAA | |
|<------------------| |
| 12. SIP REGISTER |
|-------------------------------------->|
| | 13. SAR |
| |<------------------|
| | 14. SAA |
| |------------------>|
| 15. SIP 200 (OK) |
16. SIP 200 (OK) |<--------------------------------------|
<--------------------| | |
| | |
Figure 3: Delegation of authentication to the SIP server
Figure 3 shows an example where a SIP server is dynamically allocated
to serve a SIP User Agent with the support of the Diameter server.
This may be the case of certain architectures, such as that of the
3rd Generation Partnership Project (3GPP) IP Multimedia Core Network
Subsystem.
A first SIP server receives a SIP REGISTER request (step 1) whose
target is the home network domain. In Figure 3, we assume that this
SIP server is located at the edge of the administrative home domain.
The Diameter client in this SIP server requests authorization from
the Diameter server to proceed with the registration, by sending a
Garcia-Martin, et al. Standards Track PAGE 13
RFC 4740 Diameter SIP Application November 2006
Diameter User-Authorization-Request (UAR) message (step 2). The
message includes, among other Attribute-Value-Pairs (AVPs), the SIP
Address-Of-Record (AOR) that is included in the SIP REGISTER request.
The Diameter server verifies the SIP AOR and, if it is a valid
defined user in the home network, authorizes the registration to
proceed. The Diameter server responds with a Diameter
User-Authorization-Answer (UAA) message (step 3), which informs the
Diameter client/SIP server about the result of the user
authorization. In case of a successful authorization, the Diameter
UAA message indicates the address of a local SIP server (SIP server 2
in Figure 3) and/or a list of capabilities that SIP server 1 may use
to select an appropriate SIP server 2.
When the authorization is successful, SIP server 1 forwards the SIP
REGISTER request (step 4) to the appropriate SIP server (SIP server
2). The Diameter client in SIP server 2 requests authentication
parameters by sending a Diameter Multimedia-Auth-Request (MAR)
message (step 5) to the Diameter server. This request also makes the
Diameter server aware of the SIP or SIPS URI of SIP server 2, so as
to return subsequent requests of the same user to the same SIP server
2. The Diameter server responds with a Diameter
Multimedia-Auth-Answer (MAA) message (step 6), which includes a nonce
and all the rest of the parameters necessary for the designated
authentication algorithm associated with the user. Among others, the
MAA message includes a Digest-HA1 AVP that contains H(A1) (as defined
in RFC 2617 [RFC 2617]), and that allows the Diameter client to
calculate the expected response. Then the Diameter client can
compare this expected response with the response to the challenge
sent from the SIP UA. The absence of the Digest-HA1 AVP in MAA
indicates that authentication and authorization take place in the
Diameter server, as per the scenario described in Section 6.2.
SIP server 2 creates a SIP 401 (Unauthorized) SIP response (step 7)
based on the challenge included in the MAA message, including the
authentication material needed by the SIP User Agent Client (UAC) to
include the appropriate credentials. SIP server 1 forwards the SIP
response to the SIP UAC (step 8).
The SIP server 1 receives the next SIP REGISTER request containing
the user credentials (step 9). Because SIP server 1 does not need to
keep a state (and there is no guarantee that the SIP request arrives
to the same SIP server 1), the Diameter client in SIP server 1
contacts the Diameter server again by sending a Diameter UAR message
(step 10) to determine the SIP server allocated to the user. The
Diameter server sends the SIP or SIPS URI of SIP server 2 in a
Diameter UAA message (step 11).
Garcia-Martin, et al. Standards Track PAGE 14
RFC 4740 Diameter SIP Application November 2006
SIP server 1 forwards the SIP REGISTER request to SIP server 2 (step
12). SIP server 2 validates the credentials by comparing the
response supplied by the SIP UA with the expected response calculated
by the SIP server 2 (based on the H(A1) received from the Diameter
server).
If the credentials are valid, SIP server 2 sends a Diameter
Server-Assignment-Request (SAR) message (step 13) requesting the
Diameter server to confirm the completion of the authentication
procedure and to confirm the SIP or SIPS URI of the SIP server that
is currently serving the user. The Diameter SAR message also serves
the purpose of requesting that the Diameter server send the user
profile to the SIP server. The Diameter server responds with a
Diameter Server-Assignment-Answer (SAA) message (step 14). If the
Result-Code AVP value does not inform SIP Server 2 of an error, the
SAA message can include zero or more SIP-User-Data AVPs containing
the information that SIP server 2 needs in order to provide a service
to the user.
SIP server 2 generates a SIP 200 (OK) response (step 15), which is
forwarded to SIP server 1 and eventually to the SIP UAC (step 16).
6.4. SIP Server Requests Authentication and Authorization
Figure 4 depicts a typical scenario where a stateless SIP proxy
requests authentication information and authorization to a Diameter
server, for the purpose of providing SIP routing services to a SIP
User Agent. The SIP proxy server may be configured as an outbound
SIP proxy, so that all the requests initiated by the SIP UA traverse
the SIP proxy.
According to Figure 4, a SIP User Agent sends a SIP request to its
outbound SIP proxy server. In this case, the message is a SIP INVITE
request (see step 1), but it could be any other SIP request. We
assume that this SIP request does not contain any credentials at this
time. The outbound SIP proxy server needs to authenticate and
authorize the proxy services offered to the user. The Diameter
client in the SIP server sends a Multimedia-Auth-Request (MAR)
message (step 2). The Diameter server generates a nonce and sends a
Multimedia-Auth-Answer (MAA) message (step 3) that includes the nonce
and the rest of the data necessary for the SIP server to challenge
the user, typically with HTTP Digest Authentication indicated in the
MAA message. This data enables the SIP server to create a SIP 407
(Proxy Authentication Required) response (step 4) that contains a
challenge. The SIP UA creates a new INVITE request (step 5) that
contains the credentials. The Diameter client in the SIP server
sends the credentials to the Diameter server in a new Diameter MAR
message (step 6). The Diameter server validates the credentials and
Garcia-Martin, et al. Standards Track PAGE 15
RFC 4740 Diameter SIP Application November 2006
authorize the SIP transaction in a Diameter MAA message (step 7).
The SIP server forwards the SIP INVITE request to its destination
(step 8) as per regular SIP procedures. Eventually, the session
setup is confirmed with a SIP 200 (OK) response (step 9) that is
forwarded to the SIP UA (step 10). The session setup is complete.
+--------+ +--------+
|Diameter| | SIP |
| server | | server |
+--------+ +--------+
| |
| |
1. SIP INVITE |
----------------------------------->|
| 2. MAR |
|<------------------|
| 3. MAA |
|------------------>|
| |
4. SIP 407 (Proxy |
Authentication Required) |
<-----------------------------------|
| |
5. SIP INVITE |
----------------------------------->|
| 6. MAR |
|<------------------|
| 7. MAA |
|------------------>| 8. SIP INVITE
| |---------------->
| | 9. SIP 200 (OK)
10. SIP 200 (OK) |<----------------
<-----------------------------------|
| |
Figure 4: SIP server requests authorization
6.5. Locating the Recipient of the SIP Request
Figure 5 shows the scenario where SIP server 1 may be configured as a
SIP edge proxy server, processing SIP traffic at the edge of a
network. SIP server 1 receives a SIP INVITE request (step 1). SIP
server 1 needs to find the address of SIP server 2, which is serving
the recipient of the SIP request. The Diameter client in SIP server
1 sends a Diameter Location-Info-Request (LIR) message (step 2) to
the Diameter server. The Diameter server responds with a Diameter
Location-Info-Answer (LIA) message (step 3) that contains the SIP or
Garcia-Martin, et al. Standards Track PAGE 16
RFC 4740 Diameter SIP Application November 2006
SIPS URI of SIP server 2. SIP server 1 then forwards the SIP INVITE
to SIP server 2 (step 4). SIP server 2 eventually forwards the SIP
INVITE to the appropriate UAS (step 5).
+--------+ +--------+ +--------+
| SIP | |Diameter| | SIP |
|server 1| | server | |server 2|
+--------+ +--------+ +--------+
| | |
1. SIP INVITE | | |
-------------->| 2. LIR | |
|---------------->| |
| 3. LIA | |
|<----------------| |
| 4. SIP INVITE |
|--------------------------------->|
| | | 5. SIP INVITE
| | |-------------->
| | |
| | |
Figure 5: Locating the SIP server of the recipient
Although the example shows the connection between a SIP INVITE
request and the Diameter LIR message, any SIP request other than
REGISTER (such as SUBSCRIBE, OPTIONS, etc.) would trigger the same
Diameter message. (A SIP REGISTER request will trigger a Diameter
UAR message, as indicated in Figure 2 and Figure 3.)
The scenario described in this section is also applicable in case an
outbound SIP server is not interested in authenticating the user, but
is required to locate a further SIP server to route the outbound SIP
requests. In this case, the outbound SIP server is mapped to SIP
server 1 as shown in Figure 5.
6.6. Update of the User Profile
The Diameter SIP application provides a mechanism for a Diameter
server to asynchronously download a user profile to a SIP server
whenever there is an update of such user profile. It must be noted
that the Diameter server also attaches the user profile to the
Diameter Server-Assignment-Answer (SAA) message. This is valid for
most of the daily situations; however, the administrator may decide
to update or modify the user profile for a particular user, due to,
e.g., new services made available to the user. This may involve
mechanisms outside the scope of this specification, such as human
Garcia-Martin, et al. Standards Track PAGE 17
RFC 4740 Diameter SIP Application November 2006
intervention, in the Diameter server. In this situation, the
Diameter server is able to push the new user profile into the SIP
server allocated to the user.
The scenario is illustrated in Figure 6. When the user profile
changes, the Diameter server sends a Diameter Push-Profile-Request
(PPR) message (step 1) to the Diameter client in the SIP server
allocated to that user (SIP server 2 in the examples). The Diameter
PPR message contains one or more SIP-User-Data AVPs, a User-Name AVP
and zero or more SIP-AOR AVPs. The Diameter client in SIP server 2
acknowledges the Diameter PPR message by sending a Diameter
Push-Profile-Answer (PPA) message (step 2) to the Diameter server.
+--------+ +--------+
|Diameter| | SIP |
| server | |server 2|
+--------+ +--------+
| |
| 1. PPR |
|------------------>|
| |
| 2. PPA |
|<------------------|
| |
Figure 6: Diameter server pushes an update of the user profile
6.7. SIP Soft State Termination
SIP can create soft states in SIP nodes based on events such as SIP
registrations or SIP event subscriptions. These states are
periodically refreshed, and cease to exist if they are not refreshed.
Additionally, an administrative action can be taken to terminate a
SIP soft state, or the SIP UA can explicitly terminate a SIP soft
state.
The Diameter base protocol offers a mechanism to create and delete
states in Diameter nodes. These states are called Diameter user
sessions. The Diameter server decides whether to use a Diameter user
session as a mechanism to map to a SIP soft state. If the Diameter
server decides to use Diameter user sessions, the termination of a
Diameter user session implies the termination of the corresponding
SIP soft state (e.g., registration, event subscription), and vice
versa. If the Diameter server does not use Diameter user sessions,
this Diameter SIP application offers specific commands to manage the
SIP soft states. Implementations compliant with this specification
MUST support both mechanisms of session management.
Garcia-Martin, et al. Standards Track PAGE 18
RFC 4740 Diameter SIP Application November 2006
We provide support for both Diameter client- and Diameter
server-initiated session termination. Depending on whether Diameter
sessions are used, termination of a SIP soft state can be achieved by
one of the following methods:
o When the Diameter client (SIP proxy) wants to terminate the SIP
soft state and Diameter user sessions are not maintained (i.e.,
the Auth-Session-State AVP has been previously set to
NO_STATE_MAINTAINED), the Diameter client MUST send a
Server-Assignment-Request (SAR) message with the
SIP-Server-Assignment-Type AVP (Section 9.4) set to any of the
deregistration values: TIMEOUT_DEREGISTRATION,
USER_DEREGISTRATION, TIMEOUT_DEREGISTRATION_STORE_SERVER_NAME,
USER_DEREGISTRATION_STORE_SERVER_NAME,
ADMINISTRATIVE_DEREGISTRATION, DEREGISTRATION_TOO_MUCH_DATA.
o When the Diameter client (SIP proxy) wants to terminate the SIP
soft state and Diameter user sessions are maintained (i.e., the
Auth-Session-State AVP has been previously set to
STATE_MAINTAINED), the Diameter client MUST send a Session-
Termination-Request (STR) message as per regular procedures
according to RFC 3588 [RFC 3588].
o When the Diameter server wants to terminate the SIP soft state and
Diameter user sessions are not maintained (i.e., the
Auth-Session-State AVP has been previously set to
NO_STATE_MAINTAINED), the Diameter server MUST send a
Registration-Termination-Request (RTR) message (see Section 8.9).
o When the Diameter server wants to terminate the SIP soft state and
Diameter user sessions are maintained (i.e., the
Auth-Session-State AVP has been previously set to
STATE_MAINTAINED), the Diameter server MUST send an
Abort-Session-Request (ASR) message as per regular procedures
according to RFC 3588 [RFC 3588].
6.8. Diameter Server Discovery
The basic architecture assumption of this document is that all the
data related to a user is stored in a unique Diameter server.
Contrary to general opinion, this does not create a single point of
failure. It is assumed that Diameter servers are configured in a
redundant fashion in an attempt to mitigate the
single-point-of-failure problem.
In large networks, where the number of users may be significantly
high, there might be a need to scale the number of Diameter servers.
All the data associated with a user is still stored in one Diameter
Garcia-Martin, et al. Standards Track PAGE 19
RFC 4740 Diameter SIP Application November 2006
server (typically, operating in a redundant configuration), but the
data associated with different users may reside in different Diameter
servers.
Although this configuration scales well, it introduces a new problem,
namely: given the user's SIP AOR as an input, how to determine which
of various Diameter servers is storing the data for that particular
SIP AOR. We solve this problem with inspiration from the Diameter
redirection mechanism specified in RFC 3588 [RFC 3588]. We include in
the architecture a new Diameter node that, for the purpose of this
document, is known as Diameter Subscriber Locator (SL). The Diameter
SL contains a database or routing tables that map SIP AORs to
Diameter server URIs. A particular Diameter server URI points to the
actual Diameter server that stores all the data related to a
particular SIP AOR, and in consequence, to the user who owns the SIP
AOR. The Diameter SL acts in a similar way to a Diameter Redirect
Agent, dispatching Diameter requests (e.g., providing the redirection
URI in the answer). The Diameter SL can redirect all the request
pertaining to a user by setting the Redirect-Host-Usage AVP with a
value ALL_USER, as specified in RFC 3588 [RFC 3588].
The Diameter SL can be replicated in different nodes along the
network, for the purpose of building scalability and redundancy. The
database or routing tables have to be consistent across all these
different Diameter SLs, so that equal Diameter requests will produce
equal Diameter answers, no matter which Diameter SL processes the
request.
+--------+ +--------+ +--------+ +--------+
| SIP | |Diameter| |Diameter| | SIP |
|server 1| |SL red. | |server 1| |server 2|
+--------+ +--------+ +--------+ +--------+
| | | |
1. SIP INVITE| | | |
------------>| 2. LIR | | |
|---------->| | |
| 3. LIA | | |
|<----------| | |
| 4. LIR | |
|---------------------->| |
| 5. LIA | |
|<----------------------| |
| 6. SIP INVITE | |
|----------------------------------->| 7. SIP INVITE
| | | | ------------->
| | | |
Figure 7: Locating a Diameter server. SL redirecting requests
Garcia-Martin, et al. Standards Track PAGE 20
RFC 4740 Diameter SIP Application November 2006
Figure 7 shows an example of operation of a Diameter SL acting in
redirect mode. SIP server 1 receives an INVITE request (step 1)
addressed (in the SIP Request-URI) to a user for which the Diameter
client in SIP server 1 does not possess routing information. In
other words, the Diameter client in SIP server 1 does not know the
URI of the Diameter server 1. The Diameter client sends a Diameter
LIR message (step 2) to any of the Diameter SLs configured in the
network. The address of those SLs is assumed to be pre-provisioned
in the Diameter client. The Diameter SL, based on the contents of
the SIP-AOR AVP and its own routing tables, determines the Diameter
server that stores the information allocated to such user. Then it
builds a Diameter LIA message (step 3) that includes a Result-Code
AVP set to DIAMETER_REDIRECT_INDICATION and one Redirect-Host AVP,
whose value is set to the URI of the Diameter server that stores the
information related to such user. Then the Diameter client in SIP
server 1 builds a new LIR message (step 4) addressed to the Diameter
server received in the Redirect-Host AVP. The rest of the procedure
is completed as described in previous sections.
7. Advertising Application Support
Diameter implementations conforming to this specification MUST
advertise its support by including an Auth-Application-Id AVP in the
Capabilities-Exchange-Request (CER) and Capabilities-Exchange-Answer
(CEA) commands, according to the Diameter base protocol, RFC 3588
[RFC 3588]. This Auth-Application-Id AVP MUST be set to the value of
this Diameter SIP application (Section 13.1 indicates the actual
value allocated by IANA).
Garcia-Martin, et al. Standards Track PAGE 21
RFC 4740 Diameter SIP Application November 2006
8. Diameter SIP Application Command Codes
All the Diameter implementations conforming to this specification
MUST implement and support the list of Diameter commands listed in
Table 1.
+-------------------------------------+-------+------+--------------+
| Command Name | Abbr. | Code | Reference |
+-------------------------------------+-------+------+--------------+
| User-Authorization-Request | UAR | 283 | Section 8.1 |
| User-Authorization-Answer | UAA | 283 | Section 8.2 |
| Server-Assignment-Request | SAR | 284 | Section 8.3 |
| Server-Assignment-Answer | SAA | 284 | Section 8.4 |
| Location-Info-Request | LIR | 285 | Section 8.5 |
| Location-Info-Answer | LIA | 285 | Section 8.6 |
| Multimedia-Auth-Request | MAR | 286 | Section 8.7 |
| Multimedia-Auth-Answer | MAA | 286 | Section 8.8 |
| Registration-Termination-Request | RTR | 287 | Section 8.9 |
| Registration-Termination-Answer | RTA | 287 | Section 8.10 |
| Push-Profile-Request | PPR | 288 | Section 8.11 |
| Push-Profile-Answer | PPA | 288 | Section 8.12 |
+-------------------------------------+-------+------+--------------+
Table 1: Defined command codes
Sections defining commands contain the Message Format for that
particular command. The Message Formats included in this document
are defined as per Section 3.2 of RFC 3588 [RFC 3588].
8.1. User-Authorization-Request (UAR) Command
The User-Authorization-Request (UAR) is indicated by the Command-Code
set to 283 and the Command Flags' 'R' bit set. The Diameter client
in a SIP server sends this command to the Diameter server to request
authorization for the SIP User Agent to route a SIP REGISTER request.
Because the SIP REGISTER request implicitly carries a permission to
bind an AOR to a contact address, the Diameter client uses the
Diameter UAR as a first authorization request towards the Diameter
server to authorize the registration. For instance, the Diameter
server can verify that the AOR is a legitimate user of the realm.
The Diameter client in the SIP server requests authorization for one
of the possible values defined in the SIP-User-Authorization-Type AVP
(Section 9.10).
The user name used for authentication of the user is conveyed in a
User-Name AVP (defined in the Diameter base protocol, RFC 3588
[RFC 3588]). The location of the authentication user name in the SIP
Garcia-Martin, et al. Standards Track PAGE 22
RFC 4740 Diameter SIP Application November 2006
REGISTER request varies depending on the authentication mechanism.
When the authentication mechanism is HTTP Digest as defined in RFC
2617 [RFC 2617], the authentication user name is found in the
"username" directive of the SIP Authorization header field value.
This Diameter SIP application only provides support for HTTP Digest
authentication in SIP; other authentication mechanisms are not
currently supported.
The SIP or SIPS URI to be registered is conveyed in the SIP-AOR AVP
(Section 9.8). Typically this SIP or SIPS URI is found in the To
header field value of the SIP REGISTER request that triggered the
Diameter UAR message.
The SIP-Visited-Network-Id AVP indicates the network that is
providing SIP services (e.g., SIP proxy functionality or any other
kind of services) to the SIP User Agent.
The Message Format of the UAR command is as follows:
<UAR> ::= < Diameter Header: 283, REQ, PXY >
< Session-Id >
{ Auth-Application-Id }
{ Auth-Session-State }
{ Origin-Host }
{ Origin-Realm }
{ Destination-Realm }
{ SIP-AOR }
[ Destination-Host ]
[ User-Name ]
[ SIP-Visited-Network-Id ]
[ SIP-User-Authorization-Type ]
* [ Proxy-Info ]
* [ Route-Record ]
* [ AVP ]
8.2. User-Authorization-Answer (UAA) Command
The User-Authorization-Answer (UAA) is indicated by the Command-Code
set to 283 and the Command Flags' 'R' bit cleared. The Diameter
server sends this command in response to a previously received
Diameter User-Authorization-Request (UAR) command. The Diameter
server indicates the result of the requested registration
authorization. Additionally, the Diameter server may indicate a
collection of SIP capabilities that assists the Diameter client to
select a SIP proxy to the AOR under registration.
Garcia-Martin, et al. Standards Track PAGE 23
RFC 4740 Diameter SIP Application November 2006
In addition to the values already defined in RFC 3588 [RFC 3588], the
Result-Code AVP may contain one of the values defined in
Section 10.1.
Whenever the Diameter server fails to process the Diameter UAR
message, it MUST stop processing and return the relevant error in the
Diameter UAA message. When there is success in the process, the
Diameter server MUST set the code to DIAMETER_SUCCESS in the Diameter
UAA message.
If the Diameter server requires a User-Name AVP value to process the
Diameter UAR request, but the Diameter UAR message did not contain a
User-Name AVP value, the Diameter server MUST set the Result-Code AVP
value to DIAMETER_USER_NAME_REQUIRED (see Section 10.1.2) and return
it in a Diameter UAA message. Upon reception of this Diameter UAA
message with the Result-Code AVP value set to
DIAMETER_USER_NAME_REQUIRED, the SIP server typically requests
authentication by sending a SIP 401 (Unauthorized) or SIP 407 (Proxy
Authentication Required) response back to the originator.
When the authorization procedure succeeds, the Diameter server
constructs a User-Authorization-Answer (UAA) message that MUST
include (1) the address of the SIP server already assigned to the
user name, (2) the capabilities needed by the SIP server (Diameter
client) to select another SIP server for the user, or (3) a
combination of the previous two options.
If the Diameter server is already aware of a SIP server allocated to
the user, the Diameter UAA message contains the address of that SIP
server.
The Diameter UAA message contains the capabilities required by a SIP
server to trigger and execute services. It is required that these
capabilities are present in the Diameter UAA message due to the
possibility that the Diameter client (in the SIP server) allocates a
different SIP server to trigger and execute services for that
particular user.
If a User-Name AVP is present in the Diameter UAR message, then the
Diameter server MUST verify the existence of the user in the realm,
i.e., the User-Name AVP value is a valid user within that realm. If
the Diameter server does not recognize the user name received in the
User-Name AVP, the Diameter server MUST build a Diameter User-
Authorization-Answer (UAA) message and MUST set the Result-Code AVP
to DIAMETER_ERROR_USER_UNKNOWN.
Garcia-Martin, et al. Standards Track PAGE 24
RFC 4740 Diameter SIP Application November 2006
If a User-Name AVP is present in the Diameter UAR message, then the
Diameter server MUST authorize that User-Name AVP value is able to
register the SIP or SIPS URI included in the SIP-AOR AVP. If this
authorization fails, the Diameter server must set the Result-Code AVP
to DIAMETER_ERROR_IDENTITIES_DONT_MATCH and send it in a Diameter
User-Authorization-Answer (UAA) message.
Note: Correlation between User-Name and SIP-AOR AVP values is
required in order to avoid registration of a SIP-AOR allocated to
another user.
If there is a SIP-Visited-Network-Id AVP in the Diameter UAR message,
and the SIP-User-Authorization-Type AVP value received in the
Diameter UAR message is set to REGISTRATION or REGISTRATION&
CAPABILITIES, then the Diameter server SHOULD verify whether the user
is allowed to roam into the network specified in the
SIP-Visited-Network-Id AVP in the Diameter UAR message. If the user
is not allowed to roam into that network, the Diameter AAA server
MUST set the Result-Code AVP value in the Diameter UAA message to
DIAMETER_ERROR_ROAMING_NOT_ALLOWED.
If the SIP-User-Authorization-Type AVP value received in the Diameter
UAR message is set to REGISTRATION or REGISTRATION&CAPABILITIES, then
the Diameter server SHOULD verify whether the SIP-AOR AVP value is
authorized to register in the Home Realm. Where the SIP AOR is not
authorized to register in the Home Realm, the Diameter server MUST
set the Result-Code AVP to DIAMETER_AUTHORIZATION_REJECTED and send
it in a Diameter UAA message.
When the SIP-User-Authorization-Type AVP is not present in the
Diameter UAR message, or when it is present and its value is set to
REGISTRATION, then:
o If the Diameter server is not aware of any previous registration
of the user name (including registrations of other SIP AORs
allocated to the same user name), then the Diameter server does
not know of any SIP server allocated to the user. In this case,
the Diameter server MUST set the Result-Code AVP value to
DIAMETER_FIRST_REGISTRATION in the Diameter UAA message, and the
Diameter server SHOULD include the required SIP server
capabilities in the SIP-Server-Capabilities AVP value in the
Diameter UAA message. The SIP-Server-Capabilities AVP assists the
Diameter client (SIP server) to select an appropriate SIP server
for the user, according to the required capabilities.
o In some cases, the Diameter server is aware of a previously
assigned SIP server for the same or different SIP AORs allocated
to the same user name. In these cases, re-assignment of a new SIP
Garcia-Martin, et al. Standards Track PAGE 25
RFC 4740 Diameter SIP Application November 2006
server may or may not be needed, depending on the capabilities of
the SIP server. The Diameter server MUST always include the
allocated SIP server URI in the SIP-Server-URI AVP of the UAA
message. If the Diameter server does not return the SIP
capabilities, the Diameter server MUST set the Result-Code AVP in
the Diameter UAA message to DIAMETER_SUBSEQUENT_REGISTRATION.
Otherwise (i.e., if the Diameter server includes a
SIP-Server-Capabilities AVP), then the Diameter server MUST set
the Result-Code AVP in the Diameter UAA message to
DIAMETER_SERVER_SELECTION. Then the Diameter client determines,
based on the received information, whether it needs to select a
new SIP server.
When the SIP-User-Authorization-Type AVP value received in the
Diameter UAR message is set to REGISTRATION&CAPABILITIES, then
Diameter Server MUST return the list of capabilities in the
SIP-Server-Capabilities AVP value of the Diameter UAA message, it
MUST set the Result-Code to DIAMETER_SUCCESS, and it MUST NOT return
a SIP-Server-URI AVP. The SIP-Server-Capabilities AVP enables the
SIP server (Diameter client) to select another appropriate SIP server
for invoking and executing services for the user, depending on the
required capabilities. The Diameter server MAY leave the list of
capabilities empty to indicate that any SIP server can be selected.
When the SIP-User-Authorization-Type AVP value received in the
Diameter UAR message is set to DEREGISTRATION, then:
o If the Diameter server is aware of a SIP server assigned to the
SIP AOR under deregistration, the Diameter server MUST set the
Result-Code AVP to DIAMETER_SUCCESS and MUST set the
SIP-Server-URI AVP value to the known SIP server, and return them
in the Diameter UAA message.
o If the Diameter server is not aware of a SIP server assigned to
the SIP AOR under deregistration, then the Diameter server MUST
set the Result-Code AVP in the Diameter UAA message to
DIAMETER_ERROR_IDENTITY_NOT_REGISTERED.
The Message Format of the UAA command is as follows:
<UAA> ::= < Diameter Header: 283, PXY >
< Session-Id >
{ Auth-Application-Id }
{ Auth-Session-State }
{ Result-Code }
{ Origin-Host }
{ Origin-Realm }
[ SIP-Server-URI ]
Garcia-Martin, et al. Standards Track PAGE 26
RFC 4740 Diameter SIP Application November 2006
[ SIP-Server-Capabilities ]
[ Authorization-Lifetime ]
[ Auth-Grace-Period ]
[ Redirect-Host ]
[ Redirect-Host-Usage ]
[ Redirect-Max-Cache-Time ]
* [ Proxy-Info ]
* [ Route-Record ]
* [ AVP ]
8.3. Server-Assignment-Request (SAR) Command
The Server-Assignment-Request (SAR) command is indicated by the
Command-Code set to 284 and the Command Flags' 'R' bit set. The
Diameter client in a SIP server sends this command to the Diameter
server to indicate the completion of the authentication process and
to request that the Diameter server store the URI of the SIP server
that is currently serving the user. The main functions of the
Diameter SAR command are to inform the Diameter server of the URI of
the SIP server allocated to the user, and to store or clear it from
the Diameter server. Additionally, the Diameter client can request
to download the user profile or part of it.
During the registration procedure, a SIP server becomes assigned to
the user. The Diameter client in the assigned SIP server MUST
include its own URI in the SIP-Server-URI AVP of the
Server-Assignment-Request (SAR) Diameter message and send it to the
Diameter server. The Diameter server then becomes aware of the
allocation of the SIP server to the user name and the server's URI.
The Diameter client in the SIP server MAY send a Diameter SAR message
because of other reasons. These reasons are identified in the
SIP-Server-Assignment-Type AVP (Section 9.4) value. For instance, a
Diameter client in a SIP server may contact the Diameter server to
request deregistration of a user, to inform the Diameter server of an
authentication failure, or just to download the user profile. For a
complete description of all the SIP-Server-Assignment-Type AVP
values, see Section 9.4.
Typically the reception of a SIP REGISTER request in a SIP server
will trigger the Diameter client in the SIP server to send the
Diameter SAR message. However, if a SIP server is receiving other
SIP request, such as INVITE, and the SIP server does not have the
user profile, the Diameter client in the SIP server may send the
Diameter SAR message to the Diameter server in order to download the
user profile and make the Diameter server aware of the SIP server
assigned to the user.
Garcia-Martin, et al. Standards Track PAGE 27
RFC 4740 Diameter SIP Application November 2006
The user profile is an important piece of information that dictates
the behavior of the SIP server when triggering or providing services
for the user. Typically the user profile is divided into:
o Services to be rendered to the user when the user is registered
and initiates a SIP request.
o Services to be rendered to the user when the user is registered
and a SIP request destined to that user arrives to the SIP proxy.
o Services to be rendered to the user when the user is not
registered and a SIP request destined to that user arrives to the
SIP proxy.
The SIP-Server-Assignment-Type AVP indicates the reason why the
Diameter client (SIP server) contacted the Diameter server. If the
Diameter client sets the SIP-Server-Assignment-Type AVP value to
REGISTRATION, RE_REGISTRATION, UNREGISTERED_USER, NO_ASSIGNMENT,
AUTHENTICATION_FAILURE or AUTHENTICATION_TIMEOUT, the Diameter client
MUST include exactly one SIP-AOR AVP in the Diameter SAR message.
The SAR message MAY contain zero or more SIP-Supported-User-Data-Type
AVPs. Each of them contains a type of user data understood by the
SIP server. This allows the Diameter client to provide an indication
to the Diameter server of the different format of user data
understood by the SIP server. The Diameter server uses this
information to select one or more SIP-User-Data AVPs that will be
included in the SAA message.
The Message Format of the SAR command is as follows:
<SAR> ::= < Diameter Header: 284, REQ, PXY >
< Session-Id >
{ Auth-Application-Id }
{ Auth-Session-State }
{ Origin-Host }
{ Origin-Realm }
{ Destination-Realm }
{ SIP-Server-Assignment-Type }
{ SIP-User-Data-Already-Available }
[ Destination-Host ]
[ User-Name ]
[ SIP-Server-URI ]
* [ SIP-Supported-User-Data-Type ]
* [ SIP-AOR ]
* [ Proxy-Info ]
* [ Route-Record ]
* [ AVP ]
Garcia-Martin, et al. Standards Track PAGE 28
RFC 4740 Diameter SIP Application November 2006
8.4. Server-Assignment-Answer (SAA) Command
The Server-Assignment-Answer (SAA) is indicated by the Command-Code
set to 284 and the Command Flags' 'R' bit cleared. The Diameter
server sends this command in response to a previously received
Diameter Server-Assignment-Request (SAR) command. The response may
include the user profile or part of it, if requested.
In addition to the values already defined in RFC 3588 [RFC 3588], the
Result-Code AVP may contain one of the values defined in
Section 10.1.
The Result-Code AVP value in the Diameter SAA message may indicate a
success or an error in the execution of the Diameter SAR command. If
Result-Code AVP value in the Diameter SAA message does not contain an
error code, the SAA message MAY include one or more SIP-User-Data
AVPs that typically contain the profile of the user, indicating
services that the SIP server can provide to that user.
The Diameter server MAY include one or more
SIP-Supported-User-Data-Type AVPs, each one identifying a type of
user data format supported in the Diameter server. If there is not a
common supported user data type between the Diameter client and the
Diameter server, the Diameter server SHOULD declare its list of
supported user data types by including one or more
SIP-Supported-User-Data-Type AVPs in a Diameter SAA message. This
indication is merely for debugging reasons, since there is not a
fallback mechanism that allows the Diameter client to retrieve the
profile in a supported format.
If the Diameter server requires a User-Name AVP value to process the
Diameter SAR request, but the Diameter SAR message did not contain a
User-Name AVP value, the Diameter server MUST set the Result-Code AVP
value to DIAMETER_USER_NAME_REQUIRED (see Section 10.1.2) and return
it in a Diameter SAA message. Upon reception of this Diameter SAA
message with the Result-Code AVP value set to
DIAMETER_USER_NAME_REQUIRED, the SIP server typically requests
authentication by generating a SIP 401 (Unauthorized) or SIP 407
(Proxy Authentication Required) response back to the originator.
If the User-Name AVP is included in the Diameter SAR message, upon
reception of the Diameter SAR message, the Diameter server MUST
verify the existence of the user in the realm, i.e., the User-Name
AVP value is a valid user within that realm. If the Diameter server
does not recognize the user name received in the User-Name AVP, the
Diameter server MUST build a Diameter Server-Assignment-Answer (SAA)
message and MUST set the Result-Code AVP to
DIAMETER_ERROR_USER_UNKNOWN.
Garcia-Martin, et al. Standards Track PAGE 29
RFC 4740 Diameter SIP Application November 2006
Then the Diameter server MUST authorize that User-Name AVP value is a
valid authentication name for the SIP or SIPS URI included in the
SIP-AOR AVP of the Diameter SAR message. If this authorization
fails, the Diameter server must set the Result-Code AVP to
DIAMETER_ERROR_IDENTITIES_DONT_MATCH and send it in a Diameter
Server-Assignment-Answer (SAA) message.
After successful execution of the Diameter SAR command, the Diameter
server MUST clear the "authentication pending" flag and SHOULD move
the temporarily stored SIP server URI to permanent storage.
The actions of the Diameter server upon reception of the Diameter SAR
message depend on the value of the SIP-Server-Assignment-Type:
o If the SIP-Server-Assignment-Type AVP value in the Diameter SAR
message is set to REGISTRATION or RE_REGISTRATION, the Diameter
server SHOULD verify that there is only one SIP-AOR AVP.
Otherwise, the Diameter server MUST answer with a Diameter SAA
message with the Result-Code AVP value set to
DIAMETER_AVP_OCCURS_TOO_MANY_TIMES and MUST NOT include any
SIP-User-Data AVP. If there is only one SIP-AOR AVP and if the
SIP-User-Data-Already-Available AVP value is set to
USER_DATA_NOT_AVAILABLE, then the Diameter server SHOULD include
one or more user profile data with the SIP or SIPS URI (SIP-AOR
AVP) and all other SIP identities associated with that AVP in the
SIP-User-Data AVP value of the Diameter SAA message. On selecting
the type of user data, the Diameter server SHOULD take into
account the supported formats at the SIP server
(SIP-Supported-User-Data-Type AVP in the SAR message) and the
local policy. Additionally, the Diameter server MUST set the
Result-Code AVP value to DIAMETER_SUCCESS in the Diameter SAA
message. The Diameter server considers the SIP AOR authenticated
and registered.
o If the SIP-Server-Assignment-Type AVP value in the Diameter SAR
message is set to UNREGISTERED_USER, then the Diameter server MUST
store the SIP server address included in the SIP-Server-URI AVP
value. The Diameter server will return the SIP server address in
Diameter Location-Info-Answer (LIA) messages. If the
SIP-User-Data-Already-Available AVP value is set to
USER_DATA_NOT_AVAILABLE, then the Diameter server SHOULD include
one or more user profile data associated with the SIP or SIPS URI
(SIP-AOR AVP) and associated identities in the SIP-User-Data AVP
value of the Diameter SAA message. On selecting the type of user
data, the Diameter server SHOULD take into account the supported
formats at the SIP server (SIP-Supported-User-Data-Type AVP in the
SAR message) and the local policy. The Diameter server MUST set
the Result-Code AVP value to DIAMETER_SUCCESS. The Diameter
Garcia-Martin, et al. Standards Track PAGE 30
RFC 4740 Diameter SIP Application November 2006
server considers the SIP AOR UNREGISTERED, but with a SIP server
allocated to trigger and provide services for unregistered users.
Note that in case of UNREGISTERED_USER (SIP-Server-Assignment-Type
AVP), the Diameter server MUST verify that there is only one
SIP-AOR AVP. Otherwise, the Diameter server MUST answer the
Diameter SAR message with a Diameter SAA message, and it MUST set
the Result-Code AVP value to DIAMETER_AVP_OCCURS_TOO_MANY_TIMES
and MUST NOT include any SIP-User-Data AVP.
If the User-Name AVP was not present in the Diameter SAR message
and the SIP-AOR is not known for the Diameter server, the Diameter
server MUST NOT include a User-Name AVP in the Diameter SAA
message and MUST set the Result-Code AVP value to
DIAMETER_ERROR_USER_UNKNOWN.
o If the SIP-Server-Assignment-Type AVP value in the Diameter SAR
message is set to TIMEOUT_DEREGISTRATION, USER_DEREGISTRATION,
DEREGISTRATION_TOO_MUCH_DATA, or ADMINISTRATIVE_DEREGISTRATION,
the Diameter server MUST clear the SIP server address associated
with all SIP AORs indicated in each of the SIP-AOR AVP values
included in the Diameter SAR message. The Diameter server
considers all of these SIP AORs as not registered. The Diameter
server MUST set the Result-Code AVP value to DIAMETER_SUCCESS in
the Diameter SAA message.
o If the SIP-Server-Assignment-Type AVP value in the Diameter SAR
message is set to TIMEOUT_DEREGISTRATION_STORE_SERVER_NAME or
USER_DEREGISTRATION_STORE_SERVER_NAME, the Diameter server MAY
keep the SIP server address associated with the SIP AORs included
in the SIP-AOR AVP values of the Diameter SAR message, even though
the SIP AORs become unregistered. This feature allows a SIP
server to request that the Diameter server remain an assigned SIP
server for those SIP AORs (SIP-AOR AVP values) allocated to the
same user name, and avoid SIP server assignment. The Diameter
server MUST consider all these SIP AORs as not registered. If the
Diameter server honors the request of the Diameter client (SIP
server) to remain as an allocated SIP server, then the Diameter
server MUST keep the SIP server assigned to those SIP AORs
allocated to the username and MUST set the Result-Code AVP value
to DIAMETER_SUCCESS in the Diameter SAA message. Otherwise, when
the Diameter server does not honor the request of the Diameter
client (SIP server) to remain as an allocated SIP server, the
Diameter server MUST clear the SIP server name assigned to those
SIP AORs and it MUST set the Result-Code AVP value to
DIAMETER_SUCCESS_SERVER_NAME_NOT_STORED in the Diameter SAA
message.
Garcia-Martin, et al. Standards Track PAGE 31
RFC 4740 Diameter SIP Application November 2006
o If the SIP-Server-Assignment-Type AVP value in the Diameter SAR
message is set to NO_ASSIGNMENT, the Diameter server SHOULD first
verify that the SIP-Server-URI AVP value in the Diameter SAR
message is the same URI as the one assigned to the SIP-AOR AVP
value. If they differ, then the Diameter server MUST set the
Result-Code AVP value to DIAMETER_UNABLE_TO_COMPLY in the Diameter
SAA message. Otherwise, if the SIP-User-Data-Already-Available
AVP value is set to USER_DATA_NOT_AVAILABLE, then the Diameter
server SHOULD include the user profile data with the SIP or SIPS
URI (SIP-AOR AVP) and all other SIP identities associated with
that AVP in the SIP-User-Data AVP value of the Diameter SAA
message. On selecting the type of user data, the Diameter server
SHOULD take into account the supported formats at the SIP server
(SIP-Supported-User-Data-Type AVP in the SAR message) and the
local policy.
o If the SIP-Server-Assignment-Type AVP value in the Diameter SAR
message is set to AUTHENTICATION_FAILURE or
AUTHENTICATION_TIMEOUT, the Diameter server MUST verify that there
is exactly one SIP-AOR AVP in the Diameter SAR message. If the
number of occurrences of the SIP-AOR AVP is not exactly one, the
Diameter server MUST set the Result-Code AVP value to
DIAMETER_AVP_OCCURS_TOO_MANY_TIMES in the Diameter SAA message,
and SHOULD not take further actions. If there is exactly one
SIP-AOR AVP in the Diameter SAR message, the Diameter server MUST
clear the address of the SIP server assigned to the SIP AOR
allocated to the user name, and the Diameter server MUST set the
Result-Code AVP value to DIAMETER_SUCCESS in the Diameter SAA
message. The Diameter server MUST consider the SIP AOR as not
registered.
The Message Format of the SAA command is as follows:
<SAA> ::= < Diameter Header: 284, PXY >
< Session-Id >
{ Auth-Application-Id }
{ Result-Code }
{ Auth-Session-State }
{ Origin-Host }
{ Origin-Realm }
* [ SIP-User-Data ]
[ SIP-Accounting-Information ]
* [ SIP-Supported-User-Data-Type ]
[ User-Name ]
[ Auth-Grace-Period ]
[ Authorization-Lifetime ]
[ Redirect-Host ]
[ Redirect-Host-Usage ]
Garcia-Martin, et al. Standards Track PAGE 32
RFC 4740 Diameter SIP Application November 2006
[ Redirect-Max-Cache-Time ]
* [ Proxy-Info ]
* [ Route-Record ]
* [ AVP ]
8.5. Location-Info-Request (LIR) Command
The Location-Info-Request (LIR) is indicated by the Command-Code set
to 285 and the Command Flags' 'R' bit set. The Diameter client in a
SIP server sends this command to the Diameter server to request
routing information, e.g., the URI of the SIP server assigned to the
SIP-AOR AVP value allocated to the users.
The Message Format of the LIR command is as follows:
<LIR> ::= < Diameter Header: 285, REQ, PXY >
< Session-Id >
{ Auth-Application-Id }
{ Auth-Session-State }
{ Origin-Host }
{ Origin-Realm }
{ Destination-Realm }
{ SIP-AOR }
[ Destination-Host ]
* [ Proxy-Info ]
* [ Route-Record ]
* [ AVP ]
8.6. Location-Info-Answer (LIA) Command
The Location-Info-Answer (LIA) is indicated by the Command-Code set
to 285 and the Command Flags' 'R' bit cleared. The Diameter server
sends this command in response to a previously received Diameter
Location-Info-Request (LIR) command.
In addition to the values already defined in RFC 3588 [RFC 3588], the
Result-Code AVP may contain one of the values defined in
Section 10.1. When the Diameter server finds an error in processing
the Diameter LIR message, the Diameter server MUST stop the process
of the message and answer with a Diameter LIA message that includes
the appropriate error code in the Result-Code AVP value. When there
is no error, the Diameter server MUST set the Result-Code AVP value
to DIAMETER_SUCCESS in the Diameter LIA message.
One of the errors that the Diameter server may find is that the
SIP-AOR AVP value is not a valid user in the realm. In such cases,
the Diameter server MUST set the Result-Code AVP value to
DIAMETER_ERROR_USER_UNKNOWN and return it in a Diameter LIA message.
Garcia-Martin, et al. Standards Track PAGE 33
RFC 4740 Diameter SIP Application November 2006
If the Diameter server cannot process the Diameter LIR command, e.g.,
due to a database error, the Diameter server MUST set the Result-Code
AVP value to DIAMETER_UNABLE_TO_COMPLY and return it in a Diameter
LIA message. The Diameter server MUST NOT include any SIP-Server-URI
or SIP-Server-Capabilities AVP in the Diameter LIA message.
The Diameter server may or may not be aware of a SIP server assigned
to the SIP-AOR AVP value included in the Diameter LIR message. If
the Diameter server is aware of a SIP server allocated to that
particular user, the Diameter server MUST include the URI of such SIP
server in the SIP-Server-URI AVP and return it in a Diameter LIA
message. This is typically the situation when the user is either
registered, or unregistered but a SIP server is still assigned to the
user.
When the Diameter server is not aware of a SIP server allocated to
the user (typically the case when the user unregistered), the
Result-Code AVP value in the Diameter LIA message depends on whether
the Diameter server is aware that the user has services defined for
unregistered users:
o Those users who have services defined for unregistered users may
require the allocation of a SIP server to trigger and perhaps
execute those services. Therefore, when the Diameter server is
not aware of an assigned SIP server, but the user has services
defined for unregistered users, the Diameter server MUST set the
Result-Code AVP value to DIAMETER_UNREGISTERED_SERVICE and return
it in a Diameter LIA message. The Diameter server MAY also
include a SIP-Server-Capabilities AVP to facilitate the SIP server
(Diameter client) with the selection of an appropriate SIP server
with the required capabilities. Absence of the SIP-Server-
Capabilities AVP indicates to the SIP server (Diameter client)
that any SIP server is suitable to be allocated for the user.
o Those users who do not have service defined for unregistered users
do not require further processing. The Diameter server MUST set
the Result-Code AVP value to
DIAMETER_ERROR_IDENTITY_NOT_REGISTERED and return it to the
Diameter client in a Diameter LIA message. The SIP server
(Diameter client) may return the appropriate SIP response (e.g.,
480 (Temporarily unavailable)) to the original SIP request.
The Message Format of the LIA command is as follows:
<LIA> ::= < Diameter Header: 285, PXY >
< Session-Id >
{ Auth-Application-Id }
{ Result-Code }
Garcia-Martin, et al. Standards Track PAGE 34
RFC 4740 Diameter SIP Application November 2006
{ Auth-Session-State }
{ Origin-Host }
{ Origin-Realm }
[ SIP-Server-URI ]
[ SIP-Server-Capabilities ]
[ Auth-Grace-Period ]
[ Authorization-Lifetime ]
[ Redirect-Host ]
[ Redirect-Host-Usage ]
[ Redirect-Max-Cache-Time ]
* [ Proxy-Info ]
* [ Route-Record ]
* [ AVP ]
8.7. Multimedia-Auth-Request (MAR) Command
The Multimedia-Auth-Request (MAR) command is indicated by the
Command-Code set to 286 and the Command Flags' 'R' bit set. The
Diameter client in a SIP server sends this command to the Diameter
server to request that the Diameter server authenticate and authorize
a user attempt to use some SIP service (in this context, SIP service
can be something as simple as a SIP subscription or using the proxy
services for a SIP request).
The MAR command may also register the SIP server's own URI to the
Diameter server, so that future LIR/LIA messages can return this URI.
If the SIP server is acting as a SIP registrar (see examples in
Sections 6.2 and 6.3), its Diameter client MUST include a SIP-
Server-URI AVP in the MAR command. In any other cases (see example
in Section 6.4), its Diameter client MUST NOT include a SIP-Server-
URI AVP in the MAR command.
The SIP-Method AVP MUST include the SIP method name of the SIP
request that triggered this Diameter MAR message. The Diameter
server can use this AVP to authorize some SIP requests depending on
the method.
The Diameter MAR message MUST include a SIP-AOR AVP. The SIP-AOR AVP
indicates the target of the SIP request. The value of the AVP is
extracted from different places in SIP request, depending on the
semantics of the SIP request. For SIP REGISTER messages the SIP-AOR
AVP value indicates the intended public user identity under
registration, and it is the SIP or SIPS URI populated in the To
header field value (addr-spec as per RFC 3261 [RFC 3261]) of the SIP
REGISTER request. For other types of SIP requests, such as INVITE,
SUBSCRIBE, MESSAGE, etc., the SIP-AOR AVP value indicates the
intended destination of the request. This is typically populated in
the Request-URI of the SIP request. Extracting the SIP-AOR AVP value
Garcia-Martin, et al. Standards Track PAGE 35
RFC 4740 Diameter SIP Application November 2006
from the proper SIP header field is the Diameter client's
responsibility. Extensions to SIP (new SIP methods or new semantics)
may require the SIP-AOR to be extracted from other parts of the
request.
If the SIP request includes some sort of authentication information,
the Diameter client MUST include the user name, extracted from the
authentication information of the SIP request, in the User-Name AVP
value.
The Message Format of the MAR command is as follows:
<MAR> ::= < Diameter Header: 286, REQ, PXY >
< Session-Id >
{ Auth-Application-Id }
{ Auth-Session-State }
{ Origin-Host }
{ Origin-Realm }
{ Destination-Realm }
{ SIP-AOR }
{ SIP-Method }
[ Destination-Host ]
[ User-Name ]
[ SIP-Server-URI ]
[ SIP-Number-Auth-Items ]
[ SIP-Auth-Data-Item ]
* [ Proxy-Info ]
* [ Route-Record ]
* [ AVP ]
8.8. Multimedia-Auth-Answer (MAA) Command
The Multimedia-Auth-Answer (MAA) is indicated by the Command-Code set
to 286 and the Command Flags' 'R' bit cleared. The Diameter server
sends this command in response to a previously received Diameter
Multimedia-Auth-Request (MAR) command.
In addition to the values already defined in RFC 3588 [RFC 3588], the
Result-Code AVP may contain one of the values defined in
Section 10.1.
If the Diameter server requires a User-Name AVP value to process the
Diameter MAR request, but the Diameter MAR message did not contain a
User-Name AVP value, the Diameter server MUST set the Result-Code AVP
value to DIAMETER_USER_NAME_REQUIRED (see Section 10.1.2) and return
it in a Diameter MAA message. The Diameter server MAY include a
SIP-Number-Auth-Items AVP and one or more SIP-Auth-Data-Item AVPs
with authentication information (e.g., a challenge). Upon reception
Garcia-Martin, et al. Standards Track PAGE 36
RFC 4740 Diameter SIP Application November 2006
of this Diameter MAA message with the Result-Code AVP value set to
DIAMETER_USER_NAME_REQUIRED, the SIP server typically requests
authentication by generating a SIP 401 (Unauthorized) or SIP 407
(Proxy Authentication Required) response back to the originator.
If the User-Name AVP is present in the Diameter MAR message, the
Diameter server MUST verify the existence of the user in the realm,
i.e., the User-Name AVP value is a valid user within that realm. If
the Diameter server does not recognize the user name received in the
User-Name AVP, the Diameter server MUST build a Diameter
Multimedia-Auth-Answer (MAA) message and MUST set the Result-Code AVP
to DIAMETER_ERROR_USER_UNKNOWN.
If the SIP-Methods AVP value of the Diameter MAR message is set to
REGISTER and a User-Name AVP is present, then the Diameter server
MUST authorize that User-Name AVP value is able to use the URI
included in the SIP-AOR AVP. If this authorization fails, the
Diameter server must set the Result-Code AVP to
DIAMETER_ERROR_IDENTITIES_DONT_MATCH and send it in a Diameter
Multimedia-Auth-Answer (MAA) message.
Note: Correlation between User-Name and SIP-AOR AVP values is only
required for SIP REGISTER request, to prevent a user from
registering a SIP-AOR allocated to another user. In other types
of SIP requests (e.g., INVITE), the SIP-AOR indicates the intended
destination of the request, rather than the originator of it.
The Diameter server MUST verify whether the authentication scheme
(SIP-Authentication-Scheme AVP value) indicated in the grouped
SIP-Auth-Data-Item AVP is supported or not. If that authentication
scheme is not supported, then the Diameter server MUST set the
Result-Code AVP to DIAMETER_ERROR_AUTH_SCHEME_NOT_SUPPORTED and send
it in a Diameter Multimedia-Auth-Answer (MAA) message.
If the SIP-Number-Auth-Items AVP is present in the Diameter MAR
message, it indicates the number of authentication data items that
the Diameter client is requesting. It is RECOMMENDED that the
Diameter server, when building the Diameter MAA message, includes a
number of SIP-Auth-Data-Item AVPs that are a subset of the
authentication data items requested by the Diameter client in the
SIP-Number-Auth-Items AVP value of the Diameter MAR message.
If the SIP-Server-URI AVP is present in the Diameter MAR message,
then the Diameter server MUST compare the stored SIP server (assigned
to the user) with the SIP-Server-URI AVP value (received in the
Diameter MAR message). If they don't match, the Diameter server MUST
temporarily save the newly received SIP server assigned to the user,
and MUST set an "authentication pending" flag for the user. If they
Garcia-Martin, et al. Standards Track PAGE 37
RFC 4740 Diameter SIP Application November 2006
match, the Diameter server shall clear the "authentication pending"
flag for the user.
In any other situation, if there is a success in processing the
Diameter MAR command and the Diameter server stored the
SIP-Server-URI, the Diameter server MUST set the Result-Code AVP
value to DIAMETER_SUCCESS and return it in a Diameter MAA message.
If there is a success in processing the Diameter MAR command, but the
Diameter server does not store the SIP-Server-URI because the AVP was
not present in the Diameter MAR command, then the Diameter server
MUST set the Result-Code AVP value to either:
1. DIAMETER_SUCCESS_AUTH_SENT_SERVER_NOT_STORED, if the Diameter
server is sending authentication credentials to create a
challenge.
2. DIAMETER_SUCCESS_SERVER_NAME_NOT_STORED, if the Diameter server
successfully authenticated the user and authorized the SIP server
to proceed with the SIP request.
Otherwise, the Diameter server MUST set the Result-Code AVP value to
DIAMETER_UNABLE_TO_COMPLY, and it MUST NOT include any
SIP-Auth-Data-Item AVP.
The Message Format of the MAA command is as follows:
<MAA> ::= < Diameter Header: 286, PXY >
< Session-Id >
{ Auth-Application-Id }
{ Result-Code }
{ Auth-Session-State }
{ Origin-Host }
{ Origin-Realm }
[ User-Name ]
[ SIP-AOR ]
[ SIP-Number-Auth-Items ]
* [ SIP-Auth-Data-Item ]
[ Authorization-Lifetime ]
[ Auth-Grace-Period ]
[ Redirect-Host ]
[ Redirect-Host-Usage ]
[ Redirect-Max-Cache-Time ]
* [ Proxy-Info ]
* [ Route-Record ]
* [ AVP ]
Garcia-Martin, et al. Standards Track PAGE 38
RFC 4740 Diameter SIP Application November 2006
8.9. Registration-Termination-Request (RTR) Command
The Registration-Termination-Request (RTR) command is indicated by
the Command-Code set to 287 and the Command Flags' 'R' bit set. The
Diameter server sends this command to the Diameter client in a SIP
server to indicate to the SIP server that one or more SIP AORs have
to be deregistered. The command allows an operator to
administratively cancel the registration of a user from a centralized
Diameter server.
The Diameter server has the capability to initiate the deregistration
of a user and inform the SIP server by means of the Diameter RTR
command. The Diameter server can decide whether only one SIP AOR is
going to be deregistered, a list of SIP AORs, or all the SIP AORs
allocated to the user.
The absence of a SIP-AOR AVP in the Diameter RTR message indicates
that all the SIP AORs allocated to the user identified by the
User-Name AVP are being deregistered.
The Diameter server MUST include a SIP-Deregistration-Reason AVP
value to indicate the reason for the deregistration.
The Message Format of the RTR command is as follows:
<RTR> ::= < Diameter Header: 287, REQ, PXY >
< Session-Id >
{ Auth-Application-Id }
{ Auth-Session-State }
{ Origin-Host }
{ Origin-Realm }
{ Destination-Host }
{ SIP-Deregistration-Reason }
[ Destination-Realm ]
[ User-Name ]
* [ SIP-AOR ]
* [ Proxy-Info ]
* [ Route-Record ]
* [ AVP ]
8.10. Registration-Termination-Answer (RTA) Command
The Registration-Termination-Answer (RTA) is indicated by the
Command-Code set to 287 and the Command Flags' 'R' bit cleared. The
Diameter client sends this command in response to a previously
received Diameter Registration-Termination-Request (RTR) command.
Garcia-Martin, et al. Standards Track PAGE 39
RFC 4740 Diameter SIP Application November 2006
In addition to the values already defined in RFC 3588 [RFC 3588], the
Result-Code AVP may contain one of the values defined in
Section 10.1.
If the SIP server (Diameter client) requires a User-Name AVP value to
process the Diameter RTR request, but the Diameter RTR message did
not contain a User-Name AVP value, the Diameter client MUST set the
Result-Code AVP value to DIAMETER_USER_NAME_REQUIRED (see Section
10.1.2) and return it in a Diameter RTA message.
The SIP server (Diameter client) applies the administrative
deregistration to each of the URIs included in each of the SIP-AOR
AVP values, or, if there is no SIP-AOR AVP present in the Diameter
RTR request, to all the URIs allocated to the User-Name AVP value.
The value of the SIP-Deregistration-Reason AVP in the Diameter RTR
command has an effect on the actions performed at the SIP server
(Diameter client):
o If the value is set to PERMANENT_TERMINATION, then the user has
terminated his/her registration to the realm. If informing the
interested parties (e.g., subscribers to the "reg" event
[RFC 3680]) about the administrative deregistration is supported
through SIP procedures, the SIP server (Diameter client) will do
so. The Diameter Client in the SIP Server SHOULD NOT request a
new user registration. The SIP server clears the registration
state of the deregistered AORs.
o If the value is set to NEW_SIP_SERVER_ASSIGNED, the Diameter
server informs the SIP server (Diameter client) that a new SIP
server has been allocated to the user, due to some reason. The
SIP server, if supported through SIP procedures, will inform the
interested parties (e.g., subscribers to the "reg" event
[RFC 3680]) about the administrative deregistration at this SIP
server. The Diameter client in the SIP server SHOULD NOT request
a new user registration. The SIP server clears the registration
state of the deregistered SIP AORs.
o If the value is set to SIP_SERVER_CHANGE, the Diameter server
informs the SIP server (Diameter client) that a new SIP server has
to be allocated to the user, e.g., due to user's capabilities
requiring a new SIP server, or not enough resources in the current
SIP server. If informing the interested parties about the
administrative deregistration is supported through SIP procedures
(e.g., subscriptions to the "reg" event [RFC 3680]), the SIP server
will do so. The Diameter client in the SIP Server SHOULD NOT
request a new user registration. The SIP server clears the
registration state of the deregistered SIP AORs.
Garcia-Martin, et al. Standards Track PAGE 40
RFC 4740 Diameter SIP Application November 2006
o If the value is set to REMOVE_SIP_SERVER, the Diameter server
informs the SIP server (Diameter client) that the SIP server will
no longer be bound in the Diameter server with that user. The SIP
server can delete all data related to the user.
The Message Format of the RTA command is as follows:
<RTA> ::= < Diameter Header: 287, PXY >
< Session-Id >
{ Auth-Application-Id }
{ Result-Code }
{ Auth-Session-State }
{ Origin-Host }
{ Origin-Realm }
[ Authorization-Lifetime ]
[ Auth-Grace-Period ]
[ Redirect-Host ]
[ Redirect-Host-Usage ]
[ Redirect-Max-Cache-Time ]
* [ Proxy-Info ]
* [ Route-Record ]
* [ AVP ]
8.11. Push-Profile-Request (PPR) Command
The Push-Profile-Request (PPR) command is indicated by the
Command-Code set to 288 and the Command Flags' 'R' bit set. The
Diameter server sends this command to the Diameter client in a SIP
server to update either the user profile of an already registered
user in that SIP server or the SIP accounting information. This
allows an operator to modify the data of a user profile or the
accounting information and push it to the SIP server where the user
is registered.
Each user has a user profile associated with him/her and other
accounting information. The profile or the accounting information
may change with time, e.g., due to addition of new services to the
user. When the user profile or the accounting information changes,
the Diameter server sends a Diameter Push-Profile-Request (PPR)
command to the Diameter client in a SIP server, in order to start
applying those new services.
A PPR command MAY contain a SIP-Accounting-Information AVP that
updates the addresses of the accounting servers. Changes in the
addresses of the accounting servers take effect immediately. The
Diameter client SHOULD close any existing accounting session with the
existing server and start providing accounting information to the
newly acquired accounting server.
Garcia-Martin, et al. Standards Track PAGE 41
RFC 4740 Diameter SIP Application November 2006
A PPR command MAY contain zero or more SIP-User-Data AVP values
containing the new user profile. On selecting the type of user data,
the Diameter server SHOULD take into account the supported formats at
the SIP server (SIP-Supported-User-Data-Type AVP sent in a previous
SAR message) and the local policy.
The User-Name AVP indicates the user to whom the profile is
applicable.
The Message Format of the PPR command is as follows:
<PPR> ::= < Diameter Header: 288, REQ, PXY >
< Session-Id >
{ Auth-Application-Id }
{ Auth-Session-State }
{ Origin-Host }
{ Origin-Realm }
{ Destination-Realm }
{ User-Name }
* [ SIP-User-Data ]
[ SIP-Accounting-Information ]
[ Destination-Host ]
[ Authorization-Lifetime ]
[ Auth-Grace-Period ]
* [ Proxy-Info ]
* [ Route-Record ]
* [ AVP ]
8.12. Push-Profile-Answer (PPA) Command
The Push-Profile-Answer (PPA) is indicated by the Command-Code set to
288 and the Command Flags' 'R' bit cleared. The Diameter client
sends this command in response to a previously received Diameter
Push-Profile-Request (PPR) command.
In addition to the values already defined in RFC 3588 [RFC 3588], the
Result-Code AVP may contain one of the values defined in
Section 10.1.
If there is no error when processing the received Diameter PPR
message, the SIP server (Diameter client) MUST download the received
user profile from the SIP-User-Data AVP values in the Diameter PPR
message and store it associated with the user specified in the
User-Name AVP value.
If the SIP server does not recognize or does not support some of the
data transferred in the SIP-User-Data AVP values, the Diameter client
in the SIP server MUST return a Diameter PPA message that includes a
Garcia-Martin, et al. Standards Track PAGE 42
RFC 4740 Diameter SIP Application November 2006
Result-Code AVP set to the value
DIAMETER_ERROR_NOT_SUPPORTED_USER_DATA.
If the SIP server (Diameter client) receives a Diameter PPR message
with a User-Name AVP that is unknown, the Diameter client MUST set
the Result-Code AVP value to DIAMETER_ERROR_USER_UNKNOWN and MUST
return it to the Diameter server in a Diameter PPA message.
If the SIP server (Diameter client) receives in the
SIP-User-Data-Content AVP value (of the grouped SIP-User-Data AVP)
more data than it can accept, it MUST set the Result-Code AVP value
to DIAMETER_ERROR_TOO_MUCH_DATA and MUST return it to the Diameter
server in a Diameter PPA message. The SIP server MUST NOT override
the existing user profile with the one received in the PPR message.
If the Diameter server receives the Result-Code AVP value set to
DIAMETER_ERROR_TOO_MUCH_DATA in a Diameter PPA message, it SHOULD
force a new re-registration of the user by sending to the Diameter
client a Diameter Registration-Termination-Request (RTR) with the
SIP-Deregistration-Reason AVP value set to SIP_SERVER_CHANGE. This
will force a re-registration of the user and will trigger a selection
of a new SIP server.
If the Diameter client is not able to honor the command, for any
other reason, it MUST set the Result-Code AVP value to
DIAMETER_UNABLE_TO_COMPLY and it MUST return it in a Diameter PPA
message.
The Message Format of the PPA command is as follows:
<PPA> ::= < Diameter Header: 288, PXY >
< Session-Id >
{ Auth-Application-Id }
{ Result-Code }
{ Auth-Session-State }
{ Origin-Host }
{ Origin-Realm }
[ Redirect-Host ]
[ Redirect-Host-Usage ]
[ Redirect-Max-Cache-Time ]
* [ Proxy-Info ]
* [ Route-Record ]
* [ AVP ]
Garcia-Martin, et al. Standards Track PAGE 43
RFC 4740 Diameter SIP Application November 2006
9. Diameter SIP Application AVPs
This section defines new AVPs used in this Diameter SIP application.
Applications compliant with this specification MUST implement these
AVPs.
Table 2 lists the new AVPs defined in this Diameter SIP application.
The following abbreviations are used in the Data-Type column:
o DURI: DiameterURI
o E: Enumerated
o G: Grouped
o OS: OctetString
o UTF8S: UTF8String
o U32: Unsigned32
Garcia-Martin, et al. Standards Track PAGE 44
RFC 4740 Diameter SIP Application November 2006
+-----------------------------------+------+----------------+-------+
| Attribute Name | AVP | Reference | Data- |
| | Code | | Type |
+-----------------------------------+------+----------------+-------+
| SIP-Accounting-Information | 368 | Section 9.1 | G |
| SIP-Accounting-Server-URI | 369 | Section 9.1.1 | DURI |
| SIP-Credit-Control-Server-URI | 370 | Section 9.1.2 | DURI |
| SIP-Server-URI | 371 | Section 9.2 | UTF8S |
| SIP-Server-Capabilities | 372 | Section 9.3 | G |
| SIP-Mandatory-Capability | 373 | Section 9.3.1 | U32 |
| SIP-Optional-Capability | 374 | Section 9.3.2 | U32 |
| SIP-Server-Assignment-Type | 375 | Section 9.4 | E |
| SIP-Auth-Data-Item | 376 | Section 9.5 | G |
| SIP-Authentication-Scheme | 377 | Section 9.5.1 | E |
| SIP-Item-Number | 378 | Section 9.5.2 | U32 |
| SIP-Authenticate | 379 | Section 9.5.3 | G |
| SIP-Authorization | 380 | Section 9.5.4 | G |
| SIP-Authentication-Info | 381 | Section 9.5.5 | G |
| SIP-Number-Auth-Items | 382 | Section 9.6 | U32 |
| SIP-Deregistration-Reason | 383 | Section 9.7 | G |
| SIP-Reason-Code | 384 | Section 9.7.1 | E |
| SIP-Reason-Info | 385 | Section 9.7.2 | UTF8S |
| SIP-Visited-Network-Id | 386 | Section 9.9 | UTF8S |
| SIP-User-Authorization-Type | 387 | Section 9.10 | E |
| SIP-Supported-User-Data-Type | 388 | Section 9.11 | UTF8S |
| SIP-User-Data | 389 | Section 9.12 | G |
| SIP-User-Data-Type | 390 | Section 9.12.1 | UTF8S |
| SIP-User-Data-Contents | 391 | Section 9.12.2 | OS |
| SIP-User-Data-Already-Available | 392 | Section 9.13 | E |
| SIP-Method | 393 | Section 9.14 | UTF8S |
+-----------------------------------+------+----------------+-------+
Table 2: Defined AVPs
Table 3 expands the table of AVPs included in Section 4.5 of RFC 3588
[RFC 3588]. The table indicates the Diameter AVPs defined in this
Diameter SIP Application, their possible flag values, and whether the
AVP may be encrypted. The acronyms 'M', 'P', and 'V' refer to AVP
flags whose semantics are described in RFC 3588 [RFC 3588]. The value
of the 'Encr' column is also described in RFC 3588 [RFC 3588].
Garcia-Martin, et al. Standards Track PAGE 45
RFC 4740 Diameter SIP Application November 2006
+----------------------------------+------+-----+-----+------+------+
| Attribute Name | MUST | MAY | SHD | MUST | Encr |
| | | | NOT | NOT | |
+----------------------------------+------+-----+-----+------+------+
| SIP-Accounting-Information | M | P | | V | N |
| SIP-Accounting-Server-URI | M | P | | V | N |
| SIP-Credit-Control-Server-URI | M | P | | V | N |
| SIP-Server-URI | M | P | | V | N |
| SIP-Server-Capabilities | M | P | | V | N |
| SIP-Mandatory-Capability | M | P | | V | N |
| SIP-Optional-Capability | M | P | | V | N |
| SIP-Server-Assignment-Type | M | P | | V | N |
| SIP-Auth-Data-Item | M | P | | V | N |
| SIP-Authentication-Scheme | M | P | | V | N |
| SIP-Item-Number | M | P | | V | N |
| SIP-Authenticate | M | P | | V | N |
| SIP-Authorization | M | P | | V | N |
| SIP-Authentication-Info | M | P | | V | N |
| SIP-Number-Auth-Items | M | P | | V | N |
| SIP-Deregistration-Reason | M | P | | V | N |
| SIP-Reason-Code | M | P | | V | N |
| SIP-Reason-Info | M | P | | V | N |
| SIP-Visited-Network-Id | M | P | | V | N |
| SIP-User-Authorization-Type | M | P | | V | N |
| SIP-Supported-User-Data-Type | M | P | | V | N |
| SIP-User-Data | M | P | | V | N |
| SIP-User-Data-Type | M | P | | V | N |
| SIP-User-Data-Contents | M | P | | V | N |
| SIP-User-Data-Already-Available | M | P | | V | N |
| SIP-Method | M | P | | V | N |
+----------------------------------+------+-----+-----+------+------+
Table 3: Summary of the new AVPs flags
9.1. SIP-Accounting-Information AVP
The SIP-Accounting-Information (AVP Code 368) is of type Grouped, and
contains the Diameter addresses of those nodes that are able to
collect accounting information.
The SIP-Accounting-Information AVP is defined as follows (per the
grouped-avp-def of RFC 3588 [RFC 3588]):
SIP-Accounting-Information ::= < AVP Header: 368 >
* [ SIP-Accounting-Server-URI ]
* [ SIP-Credit-Control-Server-URI ]
* [ AVP]
Garcia-Martin, et al. Standards Track PAGE 46
RFC 4740 Diameter SIP Application November 2006
9.1.1. SIP-Accounting-Server-URI AVP
The SIP-Accounting-Server-URI AVP (AVP Code 369) is of type
DiameterURI. This AVP contains the address of a Diameter server that
is able to receive SIP-session-related accounting information.
9.1.2. SIP-Credit-Control-Server-URI AVP
The SIP-Credit-Control-Server-URI AVP (AVP Code 370) is of type
DiameterURI. This AVP contains the address of a Diameter server that
is able to authorize real-time credit control usage. The Diameter
Credit-Control Application [RFC 4006] may be used for this purpose.
9.2. SIP-Server-URI AVP
The SIP-Server-URI AVP (AVP Code 371) is of type UTF8String. This
AVP contains a SIP or SIPS URI (as defined in RFC 3261 [RFC 3261])
that identifies a SIP server.
9.3. SIP-Server-Capabilities AVP
The SIP-Server-Capabilities AVP (AVP Code 372) is of type Grouped.
The Diameter indicates in this AVP the requirements for a particular
SIP capability, so that the Diameter client (SIP server) is able to
select another appropriate SIP server to serve the user.
The SIP-Server-Capabilities AVP allows a Diameter client (SIP server)
to select another SIP server for triggering or executing services to
the user. A user may have enabled some services that require the
implementation of certain capabilities in the SIP server that
triggers or executes those services. For example, the SIP server
that triggers or executes services to this user may need to implement
SIP servlets [JSR-000116], Call Processing Language (CPL) [RFC 3880],
or any other kind of capability. Or perhaps that user belongs to a
premium users group that has a certain stringent quality-of-service
agreement that requires a fast SIP server. The capabilities required
or recommended to a given user are conveyed in the
SIP-Server-Capabilities AVP. When it receives them, the Diameter
client (SIP server) that does the SIP server selection needs to have
the means to find out available SIP servers that meet the required or
optional capabilities. Such means are outside the scope of this
specification.
Note that the SIP-Server-Capabilities AVP assists the Diameter client
(SIP server) to produce a subset of all the available SIP servers to
be allocated to the user in the Home Realm; this is the subset that
conforms the requirements of capabilities on a per-user basis.
Typically this subset will be formed of more than a single SIP
Garcia-Martin, et al. Standards Track PAGE 47
RFC 4740 Diameter SIP Application November 2006
server, so once the subset of those SIP servers is identified, it is
possible that several instances of these SIP servers exist, in which
case the Diameter client (SIP server) should choose one particular
SIP server to execute and trigger services to this user. It is
expected that at this point the SIP server (Diameter client) will
follow the procedures of RFC 3263 [RFC 3263] to allocate one SIP
server to the user.
The SIP-Server-Capabilities AVP is defined as follows (per the
grouped-avp-def of RFC 3588 [RFC 3588]):
SIP-Server-Capabilities ::= < AVP Header: 372 >
* [ SIP-Mandatory-Capability ]
* [ SIP-Optional-Capability ]
* [ SIP-Server-URI ]
* [ AVP ]
9.3.1. SIP-Mandatory-Capability AVP
The SIP-Mandatory-Capability AVP (AVP Code 373) is of type
Unsigned32. The value represents a certain capability (or set of
capabilities) that have to be fulfilled by the SIP server allocated
to the user.
The semantics of the different values are not standardized, as it is
a matter of the administrative network to allocate its own semantics
within its own network. Each value has to represent a single
capability within the administrative network.
9.3.2. SIP-Optional-Capability AVP
The SIP-Optional-Capability AVP (AVP Code 374) is of type Unsigned32.
The value represents a certain capability (or set of capabilities)
that, optionally, may be fulfilled by the SIP server allocated to the
user.
The semantics of the different values are not standardized, as it is
a matter of the administrative network to allocate its own semantics
within its own network. Each value has to represent a single
capability within the administrative network.
9.4. SIP-Server-Assignment-Type AVP
The SIP-Server-Assignment-Type AVP (AVP Code 375) is of type
Enumerated and indicates the type of server update being performed in
a Diameter Server-Assignment-Request (SAR) operation. The following
values are defined:
Garcia-Martin, et al. Standards Track PAGE 48
RFC 4740 Diameter SIP Application November 2006
o NO_ASSIGNMENT (0)
The Diameter client uses this value to request the user profile of
a SIP AOR, without affecting the registration state of that
identity.
o REGISTRATION (1)
First SIP registration of a SIP AOR.
o RE_REGISTRATION (2)
Subsequent SIP registration of a SIP AOR.
o UNREGISTERED_USER (3)
The SIP server has received a SIP request (e.g., SIP INVITE)
addressed for a SIP AOR that is not registered.
o TIMEOUT_DEREGISTRATION (4)
The SIP registration timer of an identity has expired.
o USER_DEREGISTRATION (5)
The SIP server has received a request to deregister a SIP AOR.
o TIMEOUT_DEREGISTRATION_STORE_SERVER_NAME (6)
The SIP registration timer of an identity has expired. The SIP
server keeps the user data stored and requests the Diameter server
to store the SIP server address.
o USER_DEREGISTRATION_STORE_SERVER_NAME (7)
The SIP server has received a user-initiated deregistration
request. The SIP server keeps the user data stored and requests
the Diameter server to store the SIP server address.
o ADMINISTRATIVE_DEREGISTRATION (8)
The SIP server, due to administrative reasons, has deregistered a
SIP AOR.
o AUTHENTICATION_FAILURE (9)
The authentication of a user has failed.
o AUTHENTICATION_TIMEOUT (10)
The authentication timer has expired.
o DEREGISTRATION_TOO_MUCH_DATA (11)
The SIP server has requested user profile information from the
Diameter server and has received a volume of data higher than it
can accept.
Garcia-Martin, et al. Standards Track PAGE 49
RFC 4740 Diameter SIP Application November 2006
9.5. SIP-Auth-Data-Item AVP
The SIP-Auth-Data-Item (AVP Code 376) is of type Grouped and contains
the authentication and/or authorization information pertaining to a
user.
When the Diameter server uses the grouped SIP-Auth-Data-Item AVP to
include a SIP-Authenticate AVP, the Diameter server MUST send a
maximum of one authentication data item (e.g., in case the SIP
request contained several credentials). Section 11 contains a
detailed discussion and normative text of the case when a SIP request
contains several credentials.
The SIP-Auth-Data-Item AVP is defined as follows (per the
grouped-avp-def of RFC 3588 [RFC 3588]):
SIP-Auth-Data-Item ::= < AVP Header: 376 >
{ SIP-Authentication-Scheme }
[ SIP-Item-Number ]
[ SIP-Authenticate ]
[ SIP-Authorization ]
[ SIP-Authentication-Info ]
* [ AVP ]
9.5.1. SIP-Authentication-Scheme AVP
The SIP-Authentication-Scheme AVP (AVP Code 377) is of type
Enumerated and indicates the authentication scheme used in the
authentication of SIP services. RFC 2617 identifies this value as an
"auth-scheme" (see Section 1.2 of RFC 2617 [RFC 2617]). The only
currently defined value is:
o DIGEST (0) to indicate HTTP Digest authentication as specified in
RFC 2617 [RFC 2617] Section 3.2.1. Derivative work is also
considered Digest authentication scheme, as long as the
"auth-scheme" is identified as Digest in the SIP headers carrying
the HTTP authentication. This includes, e.g., the HTTP Digest
authentication using AKA [RFC 3310].
Each HTTP Digest directive (parameter) is transported in a
corresponding AVP, whose name follows the pattern Digest-*. The
Digest-* AVPs are RADIUS attributes imported from the RADIUS
Extension for Digest Authentication [RFC 4590] namespace, allowing a
smooth transition between RADIUS and Diameter applications supporting
SIP. The Diameter SIP application goes a step further by grouping
the Digest-* AVPs into the SIP-Authenticate, SIP-Authorization, and
Garcia-Martin, et al. Standards Track PAGE 50
RFC 4740 Diameter SIP Application November 2006
SIP-Authentication-Info grouped AVPs that correspond to the SIP WWW-
Authenticate/Proxy-Authentication, Authorization/Proxy-Authorization,
and Authentication-Info headers fields, respectively.
Note: Due to the fact that HTTP Digest authentication [RFC 2617] is
the only mandatory authentication mechanism in SIP, this memo only
provides support for HTTP Digest authentication and derivative
work such as HTTP Digest authentication using AKA [RFC 3310].
Extensions to this memo can register new values and new AVPs to
provide support for other authentication schemes or extensions to
HTTP Digest authentication.
Note: Although RFC 2617 [RFC 2617] defines the Basic and Digest
schemes for authenticating HTTP requests, RFC 3261 [RFC 3261] only
imports HTTP Digest as a mechanism to provide authentication in
SIP.
Due to syntactic requirements, HTTP Digest authentication has to
escape quote characters in contents of HTTP Digest directives. When
translating directives into Digest-* AVPs, the Diameter client or
server removes the surrounding quotes where present, as required by
the syntax of the Digest-* attributes defined in the "RADIUS
Extension for Digest Authentication" [RFC 4590].
9.5.2. SIP-Item-Number AVP
The SIP-Item-Number (AVP Code 378) 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 of processing is relevant. The AVP indicates the order in
which the Grouped SIP-Auth-Data-Item should be processed. Lower
values of the SIP-Item-Number AVP indicate that the whole
SIP-Auth-Data-Item SHOULD be processed before other
SIP-Auth-Data-Item AVPs that contain higher values in the
SIP-Item-Number AVP.
9.5.3. SIP-Authenticate AVP
The SIP-Authenticate AVP (AVP Code 379) is of type Grouped and
contains a reconstruction of either the SIP WWW-Authenticate or
Proxy-Authentication header fields specified in RFC 2617 [RFC 2617]
for the HTTP Digest authentication scheme. Additionally, the AVP may
include a Digest-HA1 AVP that contains H(A1) (as defined in RFC 2617
[RFC 2617]). H(A1) allows the Diameter client to create an expected
response and compare it with the Digest response received from the
SIP UA.
Garcia-Martin, et al. Standards Track PAGE 51
RFC 4740 Diameter SIP Application November 2006
The SIP-Authenticate AVP is defined as follows (per the
grouped-avp-def of RFC 3588 [RFC 3588]):
SIP-Authenticate ::= < AVP Header: 379 >
{ Digest-Realm }
{ Digest-Nonce }
[ Digest-Domain ]
[ Digest-Opaque ]
[ Digest-Stale ]
[ Digest-Algorithm ]
[ Digest-QoP ]
[ Digest-HA1]
* [ Digest-Auth-Param ]
* [ AVP ]
9.5.4. SIP-Authorization AVP
The SIP-Authorization AVP (AVP Code 380) is of type Grouped and
contains a reconstruction of either the SIP Authorization or
Proxy-Authorization header fields specified in RFC 2617 [RFC 2617] for
the HTTP Digest authentication scheme.
The SIP-Authorization AVP is defined as follows (per the
grouped-avp-def of RFC 3588 [RFC 3588]):
SIP-Authorization ::= < AVP Header: 380 >
{ Digest-Username }
{ Digest-Realm }
{ Digest-Nonce }
{ Digest-URI }
{ Digest-Response }
[ Digest-Algorithm ]
[ Digest-CNonce ]
[ Digest-Opaque ]
[ Digest-QoP ]
[ Digest-Nonce-Count ]
[ Digest-Method]
[ Digest-Entity-Body-Hash ]
* [ Digest-Auth-Param ]
* [ AVP ]
9.5.5. SIP-Authentication-Info AVP
The SIP-Authentication-Info AVP (AVP Code 381) is of type Grouped and
contains a reconstruction of the SIP Authentication-Info header
specified in RFC 2617 [RFC 2617] for the HTTP Digest authentication
scheme.
Garcia-Martin, et al. Standards Track PAGE 52
RFC 4740 Diameter SIP Application November 2006
The SIP-Authentication-Info AVP is defined as follows (per the
grouped-avp-def of RFC 3588 [RFC 3588]):
SIP-Authentication-Info ::= < AVP Header: 381 >
[ Digest-Nextnonce ]
[ Digest-QoP ]
[ Digest-Response-Auth ]
[ Digest-CNonce ]
[ Digest-Nonce-Count ]
* [ AVP ]
Note that, in some cases, the Digest-Response-Auth AVP cannot be
calculated at the Diameter server, but has to be calculated at the
Diameter client (SIP server). For example, if the value of the
quality of protection (qop) parameter in Digest is set to "auth-int",
then the response-digest (rspauth parameter value in Digest) is
calculated with the hash of the body of the SIP response, which is
not available at the Diameter server. In this case, the Diameter
client (SIP server) must calculate the response-digest once the body
of the SIP response is calculated.
Therefore, a value of "auth-int" in the Digest-QoP AVP of the
SIP-Authentication-Info AVP indicates that the Diameter client (SIP
server) MUST compute the Digest "rspauth" parameter value at the
Diameter client (SIP server).
9.5.6. Digest AVPs
The following AVPs are RADIUS attributes defined in the RADIUS
Extension for Digest Authentication [RFC 4590] and imported by this
specification: Digest-AKA-Auts, Digest-Algorithm, Digest-Auth-Param,
Digest-CNonce, Digest-Domain, Digest-Entity-Body-Hash, Digest-HA1,
Digest-Method, Digest-Nextnonce, Digest-Nonce, Digest-Nonce-Count,
Digest-Opaque, Digest-QoP, Digest-Realm, Digest-Response,
Digest-Response-Auth, Digest-URI, Digest-Username, and Digest-Stale.
9.5.6.1. Considerations about Digest-HA1 AVP
The Digest-HA1 AVP contains the value, pre-calculated at the Diameter
server, of H(A1) as defined in RFC 2617 [RFC 2617]. The Diameter
client can use H(A1) to calculate the expected Digest response,
according to this challenge. If the SIP UA is in possession of the
credentials, the calculated expected response and the response sent
from the SIP UA will match. The Diameter server MAY include this AVP
to enable and assist the SIP server in authenticating the SIP UA.
This scenario is not applicable when the Diameter server is
configured to use a session MD5 (MD5-sess) algorithm, because the
Garcia-Martin, et al. Standards Track PAGE 53
RFC 4740 Diameter SIP Application November 2006
Diameter server requires the client nonce to compute the H(A1) before
sending it to the Diameter client, and the client nonce might not be
available when the computation of H(A1) is done. Therefore, if the
final authentication is delegated to the Diameter client, it is
RECOMMENDED to configure the Diameter server to use algorithms
different than MD5-sess in HTTP Digest.
It is up to the Diameter server to include a Digest-HA1 AVP. The
Diameter server calculates the Digest H(A1) with the username,
password, and realm (and nonce and cnonce, if applicable) as inputs,
and places the result in the Digest-HA1 AVP value. For more details
of the A1 computation, see RFC 2617 [RFC 2617] Section 3.2.2.2. The
Diameter client can calculate the Digest expected response with H(A1)
as input, as described in RFC 2617 [RFC 2617] Section 3.2.2.
Section 11 provides further normative details about the usage of the
Digest-HA1 AVP.
9.5.6.2. Considerations about Digest-Entity-Body-Hash AVP
The Digest-Entity-Body-Hash AVP contains a hash of the entity body
contained in the SIP message. This hash is required by HTTP Digest
with quality of protection set to "auth-int". Diameter clients MUST
use this AVP to transport the hash of the entity body when HTTP
Digest is the authentication mechanism and the Diameter server
requires verification of the integrity of the entity body (e.g., qop
parameter set to "auth-int").
The clarifications described in Section 22.4 of RFC 3261 [RFC 3261]
about the hash of empty entity bodies apply to the
Digest-Entity-Body-Hash AVP.
9.5.6.3. Considerations about Digest-Auth-Param AVP
The Digest-Auth-Param AVP is the mechanism whereby the Diameter
client and Diameter server can exchange possible extension parameters
contained in Digest headers that are either not understood by the
Diameter client or for which there are no corresponding stand-alone
AVPs. Unlike the previously listed Digest-* AVPs, the
Digest-Auth-Param contains not only the value, but also the parameter
name, since it is unknown to the Diameter client. The Diameter node
MUST insert one Digest parameter/value combination per AVP value. If
the Digest header contains several unknown parameters, then the
Diameter implementation MUST repeat this AVP and each instance MUST
contain one different unknown Digest parameter/value combination.
This AVP corresponds to the "auth-param" parameter defined in Section
3.2.1 of RFC 2617 [RFC 2617].
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Example: Assume that the Diameter server wants the SIP server to send
a "foo" parameter with the value set to "bar", so that the SIP server
sends that combination in a SIP WWW-Authenticate header field. The
Diameter server builds a grouped SIP-Authenticate AVP that contains a
Digest-Auth-Param whose value is set to foo="bar". Then the SIP
server creates the WWW-Authenticate header field with all the digest
parameters (received in Digest-* AVPs) and adds the foo="bar"
parameter to that header field.
9.6. SIP-Number-Auth-Items AVP
The SIP-Number-Auth-Items AVP (AVP Code 382) is of type Unsigned32
and indicates the number of authentication and/or authorization
credentials that the Diameter server included in a Diameter message.
When the AVP is present in a request, it indicates the number of
SIP-Auth-Data-Items the Diameter client is requesting. This can be
used, for instance, when the SIP server is requesting several
pre-calculated authentication credentials. In the answer message,
the SIP-Number-Auth-Items AVP indicates the actual number of items
that the Diameter server included.
9.7. SIP-Deregistration-Reason AVP
The SIP-Deregistration-Reason AVP (AVP Code 383) is of type Grouped
and indicates the reason for a deregistration operation.
The SIP-Deregistration-Reason AVP is defined as follows (per the
grouped-avp-def of RFC 3588 [RFC 3588]):
SIP-Deregistration-Reason ::= < AVP Header: 383 >
{ SIP-Reason-Code }
[ SIP-Reason-Info ]
* [ AVP ]
9.7.1. SIP-Reason-Code AVP
The SIP-Reason-Code AVP (AVP Code 384) is of type Enumerated and
defines the reason for the network initiated deregistration. The
following values are defined:
o PERMANENT_TERMINATION (0)
o NEW_SIP_SERVER_ASSIGNED (1)
o SIP_SERVER_CHANGE (2)
o REMOVE_SIP_SERVER (3)
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9.7.2. SIP-Reason-Info AVP
The SIP-Reason-Info AVP (AVP Code 385) is of type UTF8String and
contains textual information that can be rendered to the user, about
the reason for a deregistration.
9.8. SIP-AOR AVP
The SIP-AOR AVP is a RADIUS attribute imported from the RADIUS
Extension for Digest Authentication [RFC 4590] namespace, allowing a
smooth transition between RADIUS and Diameter applications supporting
SIP. The SIP-AOR AVP carries the URI of the intended user related to
the SIP request (whose location in SIP may vary depending on the
actual SIP request and whether the SIP server is acting on Diameter
due to a SIP-originated or terminating requests).
The Diameter client (SIP server) uses the value found in a SIP
Request-URI or a header field value of the SIP request to construct
the SIP-AOR AVP. The selection of a Request-URI or a particular
header field to create the value of the SIP-AOR AVP depends on the
semantics of the SIP message and whether the SIP server is acting for
originating or terminating requests. For instance, when the SIP
server receives an INVITE request addressed to the served user (e.g.,
the SIP server is receiving a terminating SIP request), it maps the
SIP Request-URI of the SIP request to this AVP. However, when the
SIP server receives an INVITE request originated by the served user,
it can map either the P-Asserted-Identity or the From header field
values to this AVP. If the SIP server is acting as a SIP registrar,
then it maps the To header field of the REGISTER request to the
SIP-AOR AVP.
9.9. SIP-Visited-Network-Id AVP
The SIP-Visited-Network-Id AVP (AVP Code 386) is of type UTF8String.
This AVP contains an identifier that helps the home network identify
the visited network (e.g., the visited network domain name), in order
to authorize roaming to that visited network.
9.10. SIP-User-Authorization-Type AVP
The SIP-User-Authorization-Type AVP (AVP Code 387) is of type
Enumerated and indicates the type of user authorization being
performed in a User Authorization operation, i.e., the Diameter
User-Authorization-Request (UAR) command. The following values are
defined:
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o REGISTRATION (0)
This value is used for initial registration or re-registration.
This is the default value.
o DEREGISTRATION (1)
This value is used for deregistration.
o REGISTRATION_AND_CAPABILITIES (2)
This value is used for initial registration or re-registration
when the SIP server explicitly requests the Diameter server to get
capability information. This capability information helps the SIP
server to allocate another SIP server to serve the user.
9.11. SIP-Supported-User-Data-Type AVP
The SIP-Supported-User-Data-Type AVP (AVP Code 388) is of type
UTF8String and contains a string that identifies the type of
supported user data (user profile, see SIP-User-Data AVP
(Section 9.12)) supported in the node. The AVP can be repeated, if
the SIP server supports several user data types. In case of
repetition, the Diameter client should order the different instances
of this AVP according to its preferences.
When the Diameter client inserts this AVP in a SAR message, it allows
the Diameter client to provide an indication to the Diameter server
of the types of user data supported by the SIP server. The Diameter
server, upon inspection of these AVPs, will return a suitable
SIP-User-Data AVP (Section 9.12) of the type indicated in the
SIP-User-Data-Type AVP (Section 9.12.1).
9.12. SIP-User-Data AVP
The SIP-User-Data AVP (AVP Code 389) is of type Grouped. This AVP
allows the Diameter server to transport user-specific data, such as a
user profile, to the SIP server (in the Diameter client). The
Diameter server selects a type of user data that is understood by the
SIP server in the Diameter client, and has been indicated in a
SIP-Supported-User-Data-Type AVP. In case the Diameter client
indicated support for several types of user data, the Diameter server
SHOULD choose the first type supported by the client.
The SIP-User-Data grouped AVP contains a SIP-User-Data-Type AVP that
indicates the type of user data included in the
SIP-User-Data-Contents-AVP.
The SIP-User-Data AVP is defined as follows (per the grouped-avp-def
of RFC 3588 [RFC 3588]):
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SIP-User-Data ::= < AVP Header: 389 >
{ SIP-User-Data-Type }
{ SIP-User-Data-Contents }
* [ AVP ]
9.12.1. SIP-User-Data-Type AVP
The SIP-User-Data AVP (AVP Code 390) is of type UTF8String and
contains a string that identifies the type of user data included in
the SIP-User-Data AVP (Section 9.12).
This document does not specify a convention to characterize the type
of user data contained in the SIP-User-Data AVP (Section 9.12). It
is believed that in most cases this feature will be used in
environments controlled by a network administrator who can configure
both the client and server to assign the same value type at the
client and server. It is also RECOMMENDED that organizations
developing their own profile of SIP-User-Data AVP (Section 9.12)
allocate a type based on their canonical DNS name. For instance,
organization "example.com" can define several types of SIP-User-Data
and allocate the types "type1.dsa.example.com",
"type2.dsa.example.com", and so on. This convention will avoid a
clash in the allocation of types of SIP-User-Data AVP (Section 9.12).
9.12.2. SIP-User-Data-Contents AVP
The SIP-User-Data-Contents AVP (AVP Code 391) is of type OctetString.
The Diameter peers do not need to understand the value of this AVP.
The AVP contains the user profile data required for a SIP server to
give service to the user.
9.13. SIP-User-Data-Already-Available AVP
The SIP-User-Data-Already-Available AVP (AVP Code 392) is of type
Enumerated and gives an indication to the Diameter server about
whether the Diameter client (SIP server) already received the portion
of the user profile needed in order to serve the user. The following
values are defined:
o USER_DATA_NOT_AVAILABLE (0)
The Diameter client (SIP server) does not have the data that it
needs to serve the user.
o USER_DATA_ALREADY_AVAILABLE (1)
The Diameter client (SIP server) already has received the data
that it needs to serve the user.
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9.14. SIP-Method AVP
The SIP-Method-AVP (AVP Code 393) is of type UTF8String and contains
the method of the SIP request that triggered the Diameter message.
The Diameter server MUST use this AVP solely for authorization of SIP
requests, and MUST NOT use it to compute the Digest authentication.
To compute the Digest authentication, the Diameter server MUST use
the Digest-Method AVP instead.
10. New Values for Existing AVPs
This section defines new values that the Diameter SIP application
extends to already existing AVPs.
10.1. Extension to the Result-Code AVP Values
The Result-Code AVP is already defined in RFC 3588 [RFC 3588]. In
addition to the values already defined in RFC 3588 [RFC 3588], the
Diameter SIP application defines the following new Result-Code AVP
values:
10.1.1. Success Result-Code AVP Values
A Diameter peer uses Result-Code AVP values that fall into the
success category to inform the remote peer that a request has been
successfully completed.
o DIAMETER_FIRST_REGISTRATION 2003
The user was not previously registered. The Diameter server has
now authorized the registration.
o DIAMETER_SUBSEQUENT_REGISTRATION 2004
The user is already registered. The Diameter server has now
authorized the re-registration.
o DIAMETER_UNREGISTERED_SERVICE 2005
The user is not currently registered, but the requested service
can still be granted to the user.
o DIAMETER_SUCCESS_SERVER_NAME_NOT_STORED 2006
The request operation was successfully processed. The Diameter
server does not keep a record of the SIP server address assigned
to the user.
o DIAMETER_SERVER_SELECTION 2007
The Diameter server has authorized the registration. The user has
already been assigned a SIP server, but it may be necessary to
select a new SIP server for the user.
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o DIAMETER_SUCCESS_AUTH_SENT_SERVER_NOT_STORED 2008
The requested operation was successfully executed. The Diameter
server is sending a number of authentication credentials in the
answer message. The Diameter server does not keep a record of the
SIP server.
10.1.2. Transient Failures Result-Code AVP Values
A Diameter peer uses a Result-Code AVP value that falls in the
transient failures category to inform the remote peer that a request
could not be satisfied at the time it was received, but it MAY be
satisfied by the Diameter peer in the future.
o DIAMETER_USER_NAME_REQUIRED 4013
The Diameter request did not contain a User-Name AVP, which is
required to complete the transaction. The Diameter peer MAY
include a User-Name AVP and attempt the request again.
10.1.3. Permanent Failures Result-Code AVP Values
A Diameter peer uses a Result-Code AVP value that falls into the
permanent failure category to inform the remote peer that the request
failed and should not be attempted again.
o DIAMETER_ERROR_USER_UNKNOWN 5032
The SIP-AOR AVP value does not belong to a known user in this
realm.
o DIAMETER_ERROR_IDENTITIES_DONT_MATCH 5033
The value in one of the SIP-AOR AVPs is not allocated to the user
specified in the User-Name AVP.
o DIAMETER_ERROR_IDENTITY_NOT_REGISTERED 5034
A query for location information is received for a SIP AOR that
has not been registered before. The user to which this identity
belongs cannot be given service in this situation.
o DIAMETER_ERROR_ROAMING_NOT_ALLOWED 5035
The user is not allowed to roam to the visited network.
o DIAMETER_ERROR_IDENTITY_ALREADY_REGISTERED 5036
The identity being registered has already been assigned a server
and the registration status does not allow that it is overwritten.
o DIAMETER_ERROR_AUTH_SCHEME_NOT_SUPPORTED 5037
The authentication scheme indicated in an authentication request
is not supported.
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o DIAMETER_ERROR_IN_ASSIGNMENT_TYPE 5038
The SIP server address sent in the SIP-Server-URI AVP value of the
Diameter Server-Assignment-Request (SAR) command is the same SIP
server address that is currently assigned to the user name, but
the SIP-Server-Assignment-Type AVP is not allowed. For example,
the user is registered and the Server-Assignment-Request indicates
the assignment for an unregistered user.
o DIAMETER_ERROR_TOO_MUCH_DATA 5039
The Diameter peer in the SIP server receives more data than it can
accept. The SIP server cannot overwrite the already stored data.
o DIAMETER_ERROR_NOT SUPPORTED_USER_DATA 5040
The SIP server informs the Diameter server that the received
subscription data contained information that was not recognized or
supported.
11. Authentication Details
Authenticating a user can occur through various mechanisms.
Currently HTTP Digest authentication is supported. The actual
authentication is performed in either the SIP server or the Diameter
server.
If the Diameter server wants to assure that authentication will take
place in the Diameter server (as opposed to a delegated
authentication taking place in the SIP server), it MUST NOT include a
Digest-HA1 AVP (part of the grouped SIP-Authenticate AVP, which in
turn is part of the SIP-Auth-Data-Item AVP) in a MAA message. The
Diameter server MAY include a pre-calculated Digest-HA1 AVP in the
MAA message if it wants to delegate authentication of the user to the
SIP server.
Note that on systems where the SIP User Agent is using HTTP Digest
authentication [RFC 2617] inside of Transport Layer Security (TLS)
[RFC 4346], where only the SIP proxy server has a certificate,
delegating authentication to the SIP server (by making Digest-HA1
available to the SIP server) might reduce the load on the Diameter
server.
When requesting authentication, the Diameter client indicates in the
SIP-Number-Auth-Items AVP value of a Diameter MAR message how many
authentication credentials are being requested. In the Diameter MAA
message, the Diameter server MAY include more than one
SIP-Auth-Data-Item AVP, but it is only useful for the Diameter client
if the Digest-QoP AVP was set to 'auth-int' (in the MAR message), and
if future authentications will have the same realm. When including
more than one SIP-Auth-Data-Item AVP, the Diameter server SHOULD
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indicate how many instances of SIP-Auth-Data-Item AVPs are present
with the SIP-Number-Auth-Items AVP. This number may be different
from the one requested in the Diameter MAR message. If multiple
SIP-Auth-Data-Item AVPs are present, and their ordering is
significant, the Diameter server MUST include a SIP-Item-Number AVP
in each grouping to indicate the order. The
SIP-Authentication-Scheme AVP indicates "Digest" and the
SIP-Authenticate AVP contains data (typically a challenge of some
kind) that the user can use for her authentication. The grouped
SIP-Authorization AVP contains the AVPs that conform to the response
expected from the user.
If the Diameter server performs the authentication of the user, the
Diameter MAR message that the Diameter client sends to the Diameter
server MUST include all the authentication credentials supplied by
the SIP UA (there might be more than one credential, e.g., different
realms, authentication of proxies, etc.). Each credential is
inserted in a grouped SIP-Authorization AVP (part of the grouped
SIP-Auth-Data-Item AVP). The Diameter client MUST insert a
SIP-Number-Auth-Items AVP with the value set to the number of
credentials enclosed. If necessary, the Digest-Entity-Body-Hash AVP
will contain a hash of the body, needed to perform the
authentication. If the authentication is successful, the Diameter
MAA message will contain a Result-Code AVP indicating success, and if
necessary, the Diameter server MAY include one or more
SIP-Auth-Data-Item AVPs to provide further authentication credentials
to the SIP server. If the authentication is unsuccessful due to
missing credentials, the Diameter MAA message will include a
SIP-Auth-Data-Item AVP with the SIP-Authentication-Scheme and
SIP-Authenticate AVPs containing data (typically a challenge of some
kind) that the user can use to authenticate itself.
There are situations where a SIP request traverses several proxies,
and each of the proxies requests to authenticate the SIP UA. In this
situation, it is a valid scenario that a SIP request received at a
SIP server contains several sets of credentials. The 'realm'
directive in HTTP is the key that the Diameter client can use to
determine which credential is applicable. Also, none of the realms
may be of interest to the Diameter client, in which case the Diameter
client MUST consider that no credentials (of interest) were sent. In
any case, a Diameter client MUST send zero or exactly one credential
to the Diameter server. The Diameter client MUST choose the
credential based on the 'realm' directive in the
Authorization/Proxy-Authorization header field, and it MUST match the
realm of the Diameter client.
It must be noted that nonces are always generated in the Diameter
server.
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12. Migration from RADIUS
RADIUS offers support for HTTP Digest authentication in the RADIUS
Extension for Digest Authentication [RFC 4590]. A number of AVPs (the
Digest-* AVPs) of this Diameter SIP application are imported from the
RADIUS attributes namespace, thus making the migration from RADIUS to
Diameter smooth.
Note that the RADIUS Extension for Digest Authentication [RFC 4590]
provides a more limited scope than this Diameter SIP application.
Specifically, the RADIUS extension for Digest Authentication merely
provides support for HTTP Digest authentication, whereas the Diameter
SIP application provides support for user location, profile
downloading and update, etc.
The following sections discuss several configurations in which a
gateway translates RADIUS to Diameter and vice versa.
12.1. Gateway from RADIUS Client to Diameter Server
The gateway maps Access-Request messages to MAR request. If a RADIUS
Access-Request message contains at least one Digest-* attribute, the
gateway maps all Digest-* attributes to the AVPs of a Diameter
SIP-Authorization AVP, constructs a MAR message, and sends it to the
Diameter server. If the RADIUS Access-Request message does not
contain any Digest-* attribute, then the RADIUS client does not want
to apply HTTP Digest authentication, in which case, actions at the
gateway are outside the scope of this document.
The Diameter server responds with a MAA message. If the MAA message
contains a Result-Code AVP set to the value DIAMETER_MULTI_ROUND_AUTH
and contains challenge parameters in a SIP-Authenticate AVP, then the
gateway translates the AVPs of SIP-Authenticate AVP and puts the
resulting RADIUS attributes into an Access-Challenge message. It
sends the Access-Challenge message to the RADIUS client.
If the MAA message contains a SIP-Authentication-Info and a
Digest-Response AVP, the gateway converts these AVPs to the
corresponding RADIUS attributes and constructs a RADIUS message. If
the Result-Code AVP is DIAMETER_SUCCESS, an Access-Accept is sent.
In all other cases, an Access-Reject is sent.
12.2. Gateway from Diameter Client to RADIUS Server
The Diameter client sends a Diameter MAR message to the gateway. If
the MAR message does not contain SIP-Auth-Data-Item AVPs, the gateway
constructs an Access-Request message and maps the SIP-AOR and
SIP-Method AVPs to RADIUS attributes. The gateway sends the
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Access-Request message to the RADIUS server, which will respond with
an Access-Challenge. The gateway creates a MAA message with a
Result-Code AVP set to DIAMETER_MULTI_ROUND_AUTH and maps the
Digest-* attributes to Diameter AVPs in a SIP-Authenticate AVP. The
gateway sends the resulting MAA to the Diameter client, which will
respond with a new MAR.
The gateway checks the SIP-Auth-Data-Item AVPs of this MAR for an AVP
where the Digest-Realm AVP matches the locally configured realm
value. It takes the AVPs from this SIP-Auth-Data-Item AVP, converts
them into the corresponding RADIUS attributes and constructs a RADIUS
Access-Request message. The gateway sends the Access-Request message
to the RADIUS server. If the RADIUS server responds with an
Access-Accept message, the gateway converts the RADIUS attributes to
Diameter AVPs, constructs a MAA message with a Result-Code AVP set to
DIAMETER_SUCCESS and sends this message to the Diameter client. If
the RADIUS server responds with an Access-Reject message, the gateway
converts the RADIUS attributes to Diameter AVPs, constructs a MAA
message with a Result-Code AVP set to
DIAMETER_ERROR_IDENTITIES_DONT_MATCH, and sends this message to the
Diameter client.
12.3. Known Limitations
As mentioned earlier, there is not a 100% match between the Diameter
SIP application and the RADIUS Extension for Digest Authentication
[RFC 4590]. In particular, the RADIUS Extension for Digest
Authentication [RFC 4590] does not offer equivalent functionality to
the Diameter UAR/UAA, SAR/SAA, LIR/LIA, RTR/RTA, and PPR/PPA messages
defined by this specification.
13. IANA Considerations
This document serves as IANA registration request for a number of
items that should be registered in the AAA parameters registry.
13.1. Application Identifier
This document defines a standards-track Application-ID that falls
into the Application Identifier standards-track address space defined
by RFC 3588 [RFC 3588] Section 11.3. This Application-ID has been
registered in the Application IDs sub-registry of the AAA parameters
registry with the following data:
ID values Name Reference
----------- ------------------------ ---------
6 Diameter Session Initiation RFC 4740
Protocol (SIP) Application
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13.2. Command Codes
This document defines new standard commands whose Command Codes are
to be allocated within the standard permanent Command Codes address
space defined in RFC 3588 [RFC 3588] Section 11.2.1. These command
codes should be registered in the Command Codes sub-registry of the
AAA parameters registry.
Table 1 in Section 8 contains the detailed list of Command Code names
and values that are part of this Diameter application.
13.3. AVP Codes
This document defines new standard AVPs, whose AVP Codes are to be
allocated within the AVP Codes address space defined in RFC 3588
[RFC 3588] Section 11.4. These AVP codes have been registered in the
AVP Codes sub-registry of the AAA parameters registry.
Table 2 in Section 9 contains the detailed list of AVP names and AVP
codes that are part of this Diameter application.
13.4. Additional Values for the Result-Code AVP Value
This document defines new standard Result-Code AVP values to be
allocated within the Result-Code AVP address space defined in RFC
3588 [RFC 3588] Section 14.4.1. These values are listed in the
Result-Code AVP values section of the AVP Specific Values
sub-registry of the AAA parameters registry.
Section 10.1.1 lists the new Result-Code AVP values that fall into
the success category, according to RFC 3588 [RFC 3588] Section 7.1.2.
Section 10.1.2 lists the new Result-Code AVP values that fall into
the transient failures category, according to RFC 3588 [RFC 3588]
Section 7.1.4.
Section 10.1.3 lists the new Result-Code AVP values that fall into
the permanent failures category, according to RFC 3588 [RFC 3588]
Section 7.1.5.
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13.5. Creation of the SIP-Server-Assignment-Type Section in the AAA
Registry
This document defines a new SIP-Server-Assignment-Type AVP (see
Section 9.4). This AVP is of type Enumerated. We define an initial
set of values that should be registered by IANA. IANA should create
a new "SIP-Sever-Assignment-Type AVP values" section under the AVP
Specific Values sub-registry of the AAA parameters registry. The
initial list of values is listed in Section 9.4.
13.6. Creation of the SIP-Authentication-Scheme Section in the AAA
Registry
This document defines a new SIP-Authentication-Scheme AVP (see
Section 9.5.1). This AVP is of type Enumerated. We currently define
a single value that should be registered by IANA. IANA should create
a new "SIP-Authentication-Scheme AVP values" section under the AVP
Specific Values sub-registry of the AAA parameters registry. The
initial list of values is included in Section 9.5.1.
13.7. Creation of the SIP-Reason-Code Section in the AAA Registry
This document defines a new SIP-Reason-Code AVP (see Section 9.7.1).
This AVP is of type Enumerated. We define an initial set of values
that should be registered by IANA. IANA should create a new
"SIP-Reason-Code AVP values" section under the AVP Specific Values
sub-registry of the AAA parameters registry. The initial list of
values is listed in Section 9.7.1.
13.8. Creation of the SIP-User-Authorization-Type Section in the AAA
Registry
This document defines a new SIP-User-Authorization-Type AVP (see
Section 9.10). This AVP is of type Enumerated. We define an initial
set of values that should be registered by IANA. IANA should create
a new "SIP-User-Authorization-Type AVP values" section under the AVP
Specific Values sub-registry of the AAA parameters registry. The
initial list of values is listed in Section 9.10.
13.9. Creation of the SIP-User-Data-Already-Available Section in the
AAA Registry
This document defines a new SIP-User-Data-Already-Available AVP (see
Section 9.13). This AVP is of type Enumerated. We define an initial
set of values which should be registered by IANA. IANA should create
a new "SIP-User-Data-Already-Available AVP values" section under the
AVP Specific Values sub-registry of the AAA parameters registry. The
initial list of values is listed in Section 9.13.
Garcia-Martin, et al. Standards Track PAGE 66
RFC 4740 Diameter SIP Application November 2006
14. Security Considerations
This memo does not describe a stand-alone protocol, but a particular
application for the Diameter protocol [RFC 3588]. Consequently, all
the security considerations applicable to Diameter automatically
apply to this memo. In particular, Section 13 of RFC 3588 applies to
this memo.
This Diameter SIP application allows a Diameter client to use the
properties of HTTP Digest authentication [RFC 2617] by evaluating or
sending to the Diameter server the credentials supplied by a user.
The discussion of HTTP Digest authentication in Section 4 of RFC 2617
[RFC 2617] is also applicable to this memo.
This Diameter SIP application also allows a Diameter client to use
the properties of HTTP Digest authentication using AKA [RFC 3310] by
evaluating or sending to the Diameter server the credentials supplied
by a user. Section 5 of RFC 3310 [RFC 3310] is also applicable to
this memo.
14.1. Final Authentication Check in the Diameter Client/SIP Server
The Diameter SIP application can be configured to operate in a
scenario where the final authentication check is performed in the
Diameter client (SIP server). There are a number of security
considerations associated to it; all of them are consequences of the
requirement to transfer H(A1) from the Diameter server to the
Diameter client:
o Both Diameter client and server must trust each other, such as
when both client and server belong to the same administrative
domain.
o To avoid eavesdroppers, the transport protocol between the
Diameter client and server MUST be secured. RFC 3588 [RFC 3588]
specifies TLS [RFC 4346] and IPsec as possible transport protection
mechanisms for Diameter.
Due to these security considerations, it is RECOMMENDED to configure
the Diameter SIP application to operate in the mode where the final
authentication check is performed in the Diameter server.
Garcia-Martin, et al. Standards Track PAGE 67
RFC 4740 Diameter SIP Application November 2006
15. Contributors
The authors would like to thank the following contributors who made
substantial contributions to this work:
Pete McCann Lucent
Jaakko Rajaniemi Nokia
Wolfgang Beck (Deutsche Telekom AG) provided the text in Section 12,
"Migration from RADIUS".
16. Acknowledgements
The authors would like to thank Tony Johansson and Kevin Purser for
their invaluable contribution to the start-up of this application and
the continuous progress. The authors would like to thank Daniel
Warren, Jayshree Bharatia, Kuntal Chowdhury, Jari Arkko, Avi Lior,
Wolfgang Beck, Ulrich Wiehe, Cullen Jennings, Anu Leinonen, Glen
Zorn, German Blanco, Mikko Aittola, Bert Wijnen, and Sam Hartman for
their reviews and valuable comments.
The Diameter SIP application is based on the Diameter application for
the Cx interface of the 3GPP IP Multimedia Subsystem [3GPP.29.229].
The authors would like to thank 3GPP Working Group CN4 for this work.
17. References
17.1. Normative References
[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC 2617] Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence,
S., Leach, P., Luotonen, A., and L. Stewart, "HTTP
Authentication: Basic and Digest Access
Authentication", RFC 2617, June 1999.
[RFC 3261] Rosenberg, J., Schulzrinne, H., Camarillo, G.,
Johnston, A., Peterson, J., Sparks, R., Handley, M.,
and E. Schooler, "SIP: Session Initiation Protocol",
RFC 3261, June 2002.
[RFC 3310] Niemi, A., Arkko, J., and V. Torvinen, "Hypertext
Transfer Protocol (HTTP) Digest Authentication Using
Authentication and Key Agreement (AKA)", RFC 3310,
September 2002.
Garcia-Martin, et al. Standards Track PAGE 68
RFC 4740 Diameter SIP Application November 2006
[RFC 3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and
J. Arkko, "Diameter Base Protocol", RFC 3588,
September 2003.
[RFC 4590] Sterman, B., Sadolevsky, D., Schwartz, D., Williams,
D., and W. Beck, "RADIUS Extension for Digest
Authentication", RFC 4590, July 2006.
17.2. Informative References
[RFC 4346] Dierks, T. and E. Rescorla, "The Transport Layer
Security (TLS) Protocol Version 1.1", RFC 4346, April
2006.
[RFC 3263] Rosenberg, J. and H. Schulzrinne, "Session Initiation
Protocol (SIP): Locating SIP Servers", RFC 3263,
June 2002.
[RFC 3680] Rosenberg, J., "A Session Initiation Protocol (SIP)
Event Package for Registrations", RFC 3680,
March 2004.
[RFC 3880] Lennox, J., Wu, X., and H. Schulzrinne, "Call
Processing Language (CPL): A Language for User Control
of Internet Telephony Services", RFC 3880,
October 2004.
[RFC 4004] Calhoun, P., Johansson, T., Perkins, C., Hiller, T.,
and P. McCann, "Diameter Mobile IPv4 Application",
RFC 4004, August 2005.
[RFC 4005] Calhoun, P., Zorn, G., Spence, D., and D. Mitton,
"Diameter Network Access Server Application",
RFC 4005, August 2005.
[RFC 4006] Hakala, H., Mattila, L., Koskinen, J-P., Stura, M.,
and J. Loughney, "Diameter Credit-Control
Application", RFC 4006, August 2005.
[3GPP.29.229] 3GPP, "Cx and Dx interfaces based on the Diameter
protocol; Protocol details", 3GPP TS 29.229 5.12.0,
June 2006.
[JSR-000116] Java Community Process, "SIP Servlet API Specification
1.0 Final Release", JSR 000116, March 2003.
Garcia-Martin, et al. Standards Track PAGE 69
RFC 4740 Diameter SIP Application November 2006
Authors' Addresses
Miguel A. Garcia-Martin (Editor)
Nokia
P.O. Box 407
NOKIA GROUP, FIN 00045
Finland
Phone: +358 50 480 4586
EMail: miguel.an.garcia@nokia.com
Maria-Carmen Belinchon
Ericsson
Via de los Poblados 13
Madrid 28033
Spain
Phone: +34 91 339 3535
EMail: maria.carmen.belinchon@ericsson.com
Miguel A. Pallares-Lopez
Ericsson
Via de los Poblados 13
Madrid 28033
Spain
Phone: +34 91 339 4222
EMail: miguel-angel.pallares@ericsson.com
Carolina Canales-Valenzuela
Ericsson
Via de los Poblados 13
Madrid 28033
Spain
Phone: +34 91 339 2680
EMail: carolina.canales@ericsson.com
Garcia-Martin, et al. Standards Track PAGE 70
RFC 4740 Diameter SIP Application November 2006
Kalle Tammi
Nokia
P.O.Box 785
Tampere 33101
Finland
Phone: +358 40 505 8670
EMail: kalle.tammi@nokia.com
Garcia-Martin, et al. Standards Track PAGE 71
RFC 4740 Diameter SIP Application November 2006
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Garcia-Martin, et al. Standards Track PAGE 72
Diameter Session Initiation Protocol (SIP) Application
RFC TOTAL SIZE: 174175 bytes
PUBLICATION DATE: Wednesday, November 22nd, 2006
LEGAL RIGHTS: The IETF Trust (see BCP 78)
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