Question: After an SGW-U (Serving and Packet Data Network Gateway - User plane) restart, how does the SGW-C (Serving and Packet Data Network Gateway - Control plane) typically initiate restoration of Sx sessions if F-TEID allocation is performed in the SGW-U by network configuration?
Option 1: The SGW-C sends a PFCP Session Establishment Request without any indication, relying on the SGW-U to recognize the session.
Option 2: The SGW-C includes a new F-TEID in the PFCP Session Establishment Request, overriding any previous allocation.
Option 3: The SGW-C waits for the SGW-U to initiate the restoration process with a PFCP Association Setup Request.
Option 4: The SGW-C includes a restoration indication in the PFCP Session Establishment Request to indicate it's for an existing PFCP session, and the SGW-U accepts the SGW-C allocated F-TEID if possible.
Explanation: This is the correct approach as per the specified behavior for restoring Sx sessions after an SGW-U restart when F-TEID allocation is network-configured in the SGW-U. The restoration indication in the PFCP Session Establishment Request informs the SGW-U that this is a restoration of an existing session, and the SGW-U should accept the F-TEID allocated by the SGW-C if possible, facilitating seamless session recovery.