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Diameter in the IMS

                The 3GPP standards body has adopted Diameter as the primary signaling protocol for AAA and mobility management in the IP Multimedia Subsystem (IMS). The IMS is the service delivery environment for real-time multimedia services for the 3rd Generation wireless network and is also an ideal architecture for service convergence across fixed, wireless, and corporate enterprise networks. IMS offers a secure, mediated access to value-added services and network resources inside a managed core IP network while providing open interfaces for third party developers and enterprise-based applications that need access to the trusted carrier.

Migration from RADIUS to DIAMETER

 	RADIUS offers support for HTTP Digest authentication in the RADIUS
   Extension for Digest Authentication [RFC4590].  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 [RFC4590]
   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.

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

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