Question: What triggers the Network Slice-Specific Authentication and Authorization procedure for an S-NSSAI requiring authentication and authorization with an AAA Server?
Option 1: The AMF determines that Network Slice-Specific Authentication and Authorization is required for an S-NSSAI in the current Allowed NSSAI or Partially Allowed NSSAI during a UE-initiated service request.
Option 2: The H-PLMN operator manually initiates the procedure for all UEs with an active subscription to the network slice.
Option 3: The AMF determines that Network Slice-Specific Authentication and Authorization is required for an S-NSSAI in the current Allowed NSSAI or Partially Allowed NSSAI during a Registration procedure, or when the AAA Server that authenticated the Network Slice triggers a re-authentication.
Option 4: The UE initiates the procedure by sending a specific request to the AMF.
Explanation: According to the 3GPP specification, the Network Slice-Specific Authentication and Authorization procedure is triggered when the AMF determines that authentication and authorization are required for an S-NSSAI in the current Allowed NSSAI or Partially Allowed NSSAI during a Registration procedure, or when the AAA Server that authenticated the Network Slice triggers a re-authentication. This ensures secure access to network slices with specific requirements.