: Procedures for recovering the Home Subscriber Server, which acts as the central database for user identities and profiles.
: 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. 123380
: Focused on basic IMS recovery for GSM and UMTS. : Procedures for recovering the Home Subscriber Server,
: 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. 123380
: Nodes use indicators (often via IETF RFC 6223) to detect the availability of peers and trigger restoration if a failure is detected. 4. Evolution and Versions