Question: In a Generic Authentication Architecture (GAA) as per 3GPP standards, where can access control based on local policy, potentially evaluating User Security Settings (USSs), be enforced for a subscriber attempting to access a service via a Network Application Function (NAF)?
Option 1: Only within the NAF, upon receiving the B-TID from the User Equipment (UE)
Option 2: Only within the Bootstrapping Server Function (BSF) for Zn requests, primarily for home operator control
Option 3: In both the NAF (for Ua requests) and the BSF (for Zn requests), based on respective local policies
Option 4: Neither in the NAF nor the BSF; access control is handled externally
Explanation: Access control, which may involve evaluating USSs, is enforced in two phases: Within the NAF (for Ua requests) based on its local policy, and within the BSF (for Zn requests) for home operator control, ensuring flexible and robust access management across different network scenarios.