Question: What triggers the increment of the 'Number of mobility registration update requests via untrusted non-3GPP access' counter in a 5G network?
Option 1: Receipt by the AMF of a UE's periodic registration update over trusted 3GPP access.
Option 2: Receipt by the AMF from N3IWF of an N2 message containing a Registration Request for Mobility Registration Update via untrusted non-3GPP access.
Option 3: Successful handover of a UE from a non-3GPP to a 3GPP access network.
Option 4: Expiration of the UE's registration timer in the AMF for a trusted non-3GPP access.
Explanation: This question requires understanding of how mobility management is handled in 5G networks, especially concerning interactions between the Access and Mobility Management Function (AMF) and non-3GPP accesses via the N3IWF. The correct answer accurately reflects the condition under which the specified counter would be incremented, involving a mobility registration update request from an untrusted non-3GPP access, aligning with 5G network management and orchestration nuances.