Question: Upon detecting a P-CSCF failure, what procedure does the SMF initiate to trigger the UE to re-select a P-CSCF and register again to IMS?
Option 1: DHCP-based P-CSCF Selection Triggering Procedure
Option 2: PDU Session Establishment Request Retry
Option 3: Nsmf_PDUSession_CreateSMContext Service Operation Repeat
Option 4: IMS PDU Session Update Procedure
Explanation: When a P-CSCF is reported as failed, the SMF initiates the IMS PDU Session Update Procedure to trigger the UE to re-select a P-CSCF and then register again with the IMS.