Question: In the Sx session termination procedure for an existing PDN connection, what triggers the UP function to remove the Sx session context?
Option 1: Receipt of an Sx session modification request message from the CP function.
Option 2: Identification of the Session ID in the Sx session termination request message sent by the CP function.
Option 3: Expiration of a timer set for the PDN connection at the UP function.
Option 4: Direct instruction from an MME to the UP function without involving the CP function.
Explanation: The correct answer is Option 2 because, according to the Sx session termination procedure, the UP function identifies and removes the Sx session context based on the Session ID provided in the Sx session termination request message sent by the CP function. This highlights the importance of the Session ID in managing and terminating sessions in telecom networks, ensuring efficient resource allocation and release.