Question: During a Successful IMS Registration, what additional step is performed by the S-CSCF that was not done in an unsuccessful registration scenario?
Option 1: The S-CSCF updates HSS with the S-CSCF name being allocated to the UE, downloads the UE profile from HSS, and stores it.
Option 2: The S-CSCF only authenticates the UE without updating any records.
Option 3: The S-CSCF notifies all P-CSCFs in the network about the successful registration.
Option 4: The S-CSCF changes the UE's IP address to ensure security.
Explanation: In the context of IMS (IP Multimedia Subsystem) registrations, the step described in Option 1 is crucial for completing the registration process successfully. By updating the Home Subscriber Server (HSS) with the allocated S-CSCF name, downloading the User Equipment's (UE) profile, and storing it, the Serving Call Session Control Function (S-CSCF) ensures that the UE's registration is properly recorded and configured for subsequent IMS services. This step is distinct from an unsuccessful registration scenario, where such updates would not be necessary.