P-CSCF Restoration aids in successful establishment of MT VoLTE calls when the serving P-CSCF has failed or unreachable.
The HSS-based P-CSCF Restoration mechanism is executed when a terminating request cannot be serviced due to a P-CSCF failure. The execution is possible if there are no other registration flows available for the terminating UE using an available P-CSCF.
The HSS-based P-CSCF restoration consists of a basic mechanism that makes usage of a path through HSS and MME/SGSN to request the release of the IMS PDN connection to the corresponding UE and an optional extension that avoids the IMS PDN deactivation and re-activation.
The HSS-based P-CSCF Restoration complies with the following standard: 3gpp TS 23.380 section 5.4 HSS-based P-CSCF Restoration
The HSS-based P-CSCF Restoration feature is license controlled. Contact your Cisco Account or Support representative for information on how to obtain a license.