The specification has evolved through multiple "Releases" to keep pace with mobile technology:
: Mechanisms for the Proxy-CSCF to recover its relationship with the user equipment (UE) after a restart. 123380
: 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
The specification covers several critical failure and recovery scenarios across the IMS domain: Key Technical Mechanisms
: Integrated support for LTE and 5G networks, ensuring that high-speed packet-based services remain resilient. Summary Table: Typical Restoration Nodes Role in Restoration Primary Data Stored S-CSCF Serving node; handles session control SIP proxies, Contact info, Auth info HSS Central database; restores S-CSCF data Private User Identity, Registration Sets P-CSCF Entry point; detects UE status UE local IP, Security associations
: Handling failures of application servers that provide specific services (e.g., VoLTE, messaging). 3. Key Technical Mechanisms