Question: In a 5G network, which entity is responsible for managing the related MBS User Service for MBS group message delivery, based on a request from an Application Function (AF)?
Option 1: The external/untrusted AF (e.g., MBS Application Provider) via the Network Exposure Function (NEF)
Option 2: The NEF, interacting directly with the MBSF using the Nmbsf_MBSUserService API
Option 3: The User Equipment (UE), configuring its multicast/broadcast settings to receive group messages
Option 4: The MBSF, autonomously establishing services based on predefined network policies
Explanation: For MBS group message delivery, the Network Exposure Function (NEF) acts as an Application Function (AF) and is thus responsible for establishing and managing the related MBS User Service. This is achieved through direct interaction with the Multicast/Broadcast Service Function (MBSF) using the Nmbsf_MBSUserService API, highlighting the NEF's pivotal role in this specific scenario within 5G multicast-broadcast services.