Question: Upon receipt of an SGsAP-SERVICE-REQUEST message with a 'CS call indicator' from the MME, what action does the VLR take regarding timer Ts14?
Option 1: The VLR stops timer Ts14 immediately to prioritize CS call setup.
Option 2: The VLR starts timer Ts14 to supervise the success of UE fallback.
Option 3: The VLR resets all existing timers related to the UE's previous activities.
Option 4: The VLR sends an SGsAP-PAGING-REJECT message to the MME as a response.
Explanation: When the VLR receives an SGsAP-SERVICE-REQUEST with a 'CS call indicator', it initiates a process to manage UE fallback for a CS (Circuit Switched) call. Starting timer Ts14 is crucial for supervising the success of this fallback, ensuring timely handling of the call setup process.