Question: For an N5CW device attempting to register to a 5GCN via trusted non-3GPP access in a selected PLMN, what determines whether the username part of the NAI is derived from SUCI or 5G-GUTI?
Option 1: The type of access network (NG-RAN or non-NG-RAN) through which the N5CW device is registered to the 5GCN.
Option 2: The presence of a USIM storing the HPLMN identity in the N5CW device.
Option 3: The specific PLMN (HPLMN or VPLMN) to which the N5CW device attempts to connect.
Option 4: The version of EAP authentication procedure (e.g., EAP-AKA') being used.
Explanation: According to the specifications for NAI format when an N5CW device accesses a 5GCN via trusted non-3GPP access, the username part (<5G_device_unique_identity>) is derived from SUCI if the UE is not registered to 5GCN via NG-RAN, or from 5G-GUTI if the N5CW device **is** registered to 5GCN via NG-RAN. This highlights the importance of the access network type in determining the NAI format for secure authentication and identification processes in telecom networks.