Question: What triggers the increment of the 'Number of periodic registration update requests via untrusted non-3GPP access' counter in a 5G network?
Option 1: Receipt by the AMF (Access and Mobility Management Function) of an N2 message from the N3IWF (Non-3GPP Interworking Function) containing a Registration Request for Periodic Registration Update.
Option 2: Successful completion of a periodic registration update request via trusted non-3GPP access.
Option 3: Arrival of user data packets at the UPF (User Plane Function) from an untrusted non-3GPP network.
Option 4: Expiration of a timer for periodic registration updates in the UE (User Equipment).
Explanation: This question requires understanding of how periodic registration update requests are handled in a 5G network, particularly via untrusted non-3GPP access. The correct answer is based on the process where the receipt of a specific N2 message by the AMF from the N3IWF triggers the counter increment. This highlights the interaction between network functions for managing user registrations and the importance of accurate counting for network performance and management. Options 2 through 4 are incorrect because they refer to different scenarios that do not directly trigger the counter in question.