: These are specific Diameter protocol messages (Server-Assignment-Request and Location-Information-Request) used by the HSS and S-CSCF to update and overwrite user data during restoration events.
: Mechanisms for the Proxy-CSCF to recover its relationship with the user equipment (UE) after a restart.
The specification covers several critical failure and recovery scenarios across the IMS domain:
: Procedures for when a Serving-Call Session Control Function (S-CSCF) fails or loses registration data. It defines how the Home Subscriber Server (HSS) and other nodes collaborate to re-register users or restore sessions.
: Focused on basic IMS recovery for GSM and UMTS.
: During initial registration, the S-CSCF backs up critical data—such as the list of SIP proxies, contact information, and authentication schemes—to the HSS.
