Question: What does the SMF set the PTI IE of the SERVICE-LEVEL AUTHENTICATION COMMAND message to when initiating the service-level authentication and authorization procedure?
Option 1: Procedure transaction identity assigned
Option 2: No procedure transaction identity assigned
Option 3: Service-level-AA payload type
Option 4: PDU session ID
Explanation: The SMF sets the PTI IE of the SERVICE-LEVEL AUTHENTICATION COMMAND message to "No procedure transaction identity assigned" when initiating the service-level authentication and authorization procedure, as specified in the 3GPP TS 24.501 standard. This is a crucial step in the process, as it indicates that no procedure transaction identity has been assigned at this point.