Question: In a multi-access IP-CAN session, how does a PCRF (Policy and Charging Rules Function) initiate the removal of one access due to a change in operator policy or user subscriptions?
Option 1: By sending a CCA (Credit-Control-Answer) command with the IP-CAN-Type AVP set to "ADD_ACCESS" and the Access-Type AVP indicating the access to be removed.
Option 2: Through a direct request to the UE (User Equipment) to disable the specific access, using NAS (Non-Access Stratum) signaling.
Option 3: By including the Removal-Of-Access AVP set to "REMOVAL_OF_ACCESS" and specifying the IP-CAN-Type AVP for the removed access in a CCA or RAR (Re-Auth Request) command to the PCEF (Policy and Charging Enforcement Function).
Option 4: Via an update to the subscriber's profile on the HSS (Home Subscriber Server), triggering automatic access removal.
Explanation: This is the correct method, where the PCRF initiates access removal by setting specific AVPs in commands sent to the PCEF, ensuring the PCEF can automatically delete corresponding PCC rules and proceed with the access removal procedure.