Question: What is the general approach to using NAS procedures and messages over non-3GPP access from the UE's perspective?
Option 1: The UE uses completely different procedures and messages for non-3GPP access compared to 3GPP access.
Option 2: The UE uses a combination of 5GMM and 5GSM procedures, but with significant modifications for non-3GPP access.
Option 3: The UE only uses 5GMM procedures over non-3GPP access, and not 5GSM procedures.
Option 4: The UE generally uses the same procedures and messages defined for 5GMM and 5GSM over both 3GPP and non-3GPP access, with some exceptions.
Explanation: From the UE's NAS perspective, the general approach is to reuse the same procedures and messages defined for 5GMM and 5GSM over both 3GPP and non-3GPP access. However, there are some differences and exceptions that apply specifically to non-3GPP access, as described in subsequent subclauses.