Question: What action does the UPF take when notified by the SMF that an access type of an MA PDU session has become transiently unavailable?
Option 1: Immediately release all resources associated with the MA PDU session.
Option 2: Continue sending DL traffic on the unavailable access, assuming temporary loss of coverage.
Option 3: Stop sending DL traffic on this access until notified by the SMF or receiving a PMF access available report from the UE that it becomes available again.
Option 4: Send an error response to the SMF indicating inability to comply with the request.
Explanation: When an access type becomes transiently unavailable (e.g., temporary loss of coverage), the UPF should temporarily halt downstream (DL) traffic on that specific access. This pause is in place until either the Session Management Function (SMF) signals its availability again or the UE confirms access recovery via a report, minimizing unnecessary traffic and potential packet loss during transient outages.