Known Behavior
This section briefly describes IMS AAA Server behavior and related issues. In some cases the behavior differs from non-IMS AAA Server implementations; in others the behavior is included to emphasize how the IMS AAA Server works.
- The IMS AAA Server does not initiate subscriber de-registration in the HSS (Home Subscriber Server). Subscriber de-registration is performed when the IMS AAA Server receives an HSS Registration-Termination-Request.
- Routing policy download requests are not sent over the Wd reference point (see TS 29.234 9.3.1). These requests are received by the AAA Proxy, and it is 3GPP AAA Proxy's responsibility to locate the WAG (WLAN Access Gateway) responsible for serving the subscriber.
- The IMS AAA Server is capable of serving RADIUS requests with a Service-Type value of "Authorize only." This is done for compatibility with RADIUS CoA (Change of Authorization) functionality.
- An STR (Session-Termination-Request) received without a 3GPP-WLAN-APN-Id attribute causes all authorizations for the given Diameter Session-Id to be terminated.
- An ASR (Abort-Session-Request) received without a 3GPP-WLAN-APN-Id attribute causes all authorizations for the given Diameter Session-ID to be aborted.
- RADIUS CoA and DM (Disconnect Messages) affect all sessions for the subscriber specified in User-Name attribute.
- The IMS AAA Server sends an STR to the WAG and expects an ASR to be returned from the WAG contrary to TS 29.234 which specifies ASR from AAA Server/Proxy to the WAG and STR from the WAG to AAA Server/Proxy. This has been implemented to comply with the Diameter Base Protocol as described in Section 9.2 of TS 29.234, which states: "the 3GPP AAA Server or Proxy shall act as the NAS client and the WAG as the Diameter Server."
- The Diameter REDIRECT INDICATION is supported only over the Wx and Dw reference points. A Diameter REDIRECT INDICATION in an AA-Answer message, received by the AAA Proxy from a AAA Server over the Wd reference point, is returned to the client without attempting to forward the request to the Redirect-Host. This ensures that only routing rules configured by a system administrator are enforced.
- A Diameter Redirect-Host-Usage value included in an MA-Answer (Multimedia-Authentication-Answer) message, and received over either the Wx or Dw reference points is ignored. The value is assumed to be DONT_CACHE.