Question: Upon restarting after a failure, what action does a Visitor Location Register (VLR) take regarding its connection with Mobility Management Entities (MMEs) via the SGs interface for UEs that had lost SGs association information?
Option 1: The VLR immediately sends an SGsAP-MM-INFORMATION-REQUEST to re-establish connections for all affected UEs.
Option 2: The VLR enters a standby mode, awaiting manual intervention before reconnecting with MMEs.
Option 3: The VLR updates its database without notifying the MMEs about the lost associations.
Option 4: The VLR sends an SGsAP-RESET-INDICATION message to all connected MMEs and starts a timer (Ts11) for each, indicating unreliable SGs associations.
Explanation: This is the correct action in case of a VLR failure leading to lost UE association information. The SGsAP-RESET-INDICATION message informs MMEs that the SGs association for affected UEs is no longer reliable, prompting necessary actions at the MME end. Starting a separate timer (Ts11) for each MME helps in managing the re-establishment process or handling potential subsequent timeouts, ensuring synchronization and reliability across the network after a failure.