123380 File

: 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.

The specification has evolved through multiple "Releases" to keep pace with mobile technology: 123380

: 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. : Procedures for when a Serving-Call Session Control

: Handling failures of application servers that provide specific services (e.g., VoLTE, messaging). 3. Key Technical Mechanisms : Handling failures of application servers that provide

: 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.

: Focused on basic IMS recovery for GSM and UMTS.

: 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