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: Mechanisms for the Proxy-CSCF to recover its relationship with the user equipment (UE) after a restart.

: 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

: 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

: Procedures for recovering the Home Subscriber Server, which acts as the central database for user identities and profiles. messaging). 3. Key Technical Mechanisms

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