Question: What is a prerequisite for the procedure of using L2TP between UPF and DN via N6 to carry traffic of a PDU Session?
Option 1: The UE must be aware of the L2TP procedure.
Option 2: The UE is already registered to the 5GC and both SMF and UPF support the L2TP feature.
Option 3: The DN-AAA Server has provided the L2TP Tunnel parameters to the SMF.
Option 4: The UPF has an existing L2TP Tunnel setup.
Explanation: According to the text, it is a prerequisite that "the UE is already registered to the 5GC and both SMF and UPF support the L2TP feature" for the procedure of using L2TP between UPF and DN via N6 to carry traffic of a PDU Session.