Question: Which of the following nodes can initiate the procedure of releasing a NAS signalling connection in a 5G System (5GS)?
Option 1: UE: User Equipment
Option 2: AN node (either 5G (R)AN node or N3IWF) or the AMF
Option 3: NG-RAN node only
Option 4: SMF: Session Management Function
Explanation: The procedure of releasing a NAS signalling connection can be initiated by either the AN node (which includes 5G (R)AN node or N3IWF) or the AMF, as specified in the 3GPP TS 23.501 document. This highlights the roles of these nodes in managing and controlling the NAS signalling connections within the 5GS architecture.