123380

: 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.

For further technical reading, the latest versions (such as ) are available via the ETSI Deliverable Repository . ETSI TS 123 380 V9.6.0 (2014-03) 123380

: 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

: 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 : Focused on basic IMS recovery for GSM and UMTS

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. ETSI TS 123 380 V9

The specification covers several critical failure and recovery scenarios across the IMS domain: