Question: In a 5G network, what triggers the increment of the 'Number of successful registrations allowed for SMS over NAS via non-3GPP access' measurement?
Option 1: Receipt of an SMS message by the UE from the AF via non-3GPP access.
Option 2: Transmission of a Registration Request message by the UE to the AMF via non-3GPP access.
Option 3: Transmission of a Registration Accept message containing the 'SMS allowed' indication by the AMF to UE via non-3GPP access.
Option 4: Delivery of an SMS over NAS to the UE via 3GPP access.
Explanation: This measurement is incremented when the Access and Mobility Management Function (AMF) successfully responds to a UE's registration request with an acceptance that includes permission for SMS over NAS, enabling SMS services for UEs connected via non-3GPP access networks. Options 1 and 4 are incorrect as they describe unrelated actions or a different access type. Option 2 is incorrect as it describes an initial request, not the successful outcome being measured.