Question: In the context of IP Multimedia Subsystem (IMS) Performance Management, what triggers the increment of a failed HSS initiated user profile update procedure measurement at the S-CSCF?
Option 1: Receipt by the S-CSCF of a Push-Profile-Request Diameter command from the HSS
Option 2: Transmission by the S-CSCF to the HSS of a Push-Profile-Answer Diameter command indicating procedure failure
Option 3: Successful update of a user profile at the HSS initiated by the S-CSCF
Option 4: Periodic synchronization between S-CSCF and HSS for user profile updates
Explanation: The correct answer is Option 2 because each failed user profile update procedure is counted when the S-CSCF transmits a Push-Profile-Answer Diameter command to the HSS, indicating the update procedure has failed for a specific cause. This action of transmission upon failure triggers the increment of the measurement.