Question: What action does a Visitor Location Register (VLR) take upon receiving an SGsAP-TMSI-REALLOCATION-COMPLETE message during a TMSI reallocation procedure for a User Equipment (UE)?
Option 1: The VLR immediately deallocates the old Temporary Mobile Subscriber Identity (TMSI) and stops timer Ts6-2.
Option 2: The VLR sends an additional SGsAP-LOCATION-UPDATE-ACCEPT message to confirm receipt.
Option 3: The VLR stops timer Ts6-2 and considers the new TMSI as valid for the UE.
Option 4: The VLR restarts the TMSI reallocation procedure with a new TMSI.
Explanation: Upon receiving the SGsAP-TMSI-REALLOCATION-COMPLETE message, the VLR's primary actions are to validate the new TMSI for use and to stop the Ts6-2 timer, which was started after sending the SGsAP-LOCATION-UPDATE-ACCEPT with the new TMSI. This ensures the successful completion of the TMSI reallocation procedure from the VLR's perspective, making the new TMSI usable for subsequent communications with the UE.