Question: What action is required by the UE when it receives a NOTIFICATION message with a notification indicator value of "#1"?
Option 1: Perform a Location Update procedure.
Option 2: Re-establish an IMS session and cancel SRVCC handover.
Option 3: Release all ongoing sessions and re-register with the network.
Option 4: Ignore the notification and continue with current activities.
Explanation: When the UE receives a NOTIFICATION message with a notification indicator value of "#1", it indicates that an SRVCC handover has been cancelled, and IMS session re-establishment is required. This requires the UE to take action to re-establish the IMS session, ensuring continuity of service.