Question: Upon release of a multicast MRB, what action(s) shall the User Equipment (UE) take regarding associated entities and resources?
Option 1: Release PDCP, RLC, MAC, and physical layer configurations, and also release SDAP entity if no other MRB is associated with the mbs-SessionId.
Option 2: Only release PDCP, RLC, MAC, and physical layer configurations without considering the status of the SDAP entity or its associated MRBs.
Option 3: Indicate the release of user plane resources for the mbs-SessionId to upper layers without releasing any lower-layer entities (PDCP, RLC, MAC, Physical).
Option 4: Suspend (not release) all entities related to the multicast MRB until further instruction from the network.
Explanation: Upon the release of a multicast MRB, the UE must not only release the lower-layer configurations (PDCP, RLC, MAC, and physical layer) but also consider the status of the SDAP entity. If the SDAP entity has no other associated MRBs for the given mbs-SessionId, it too should be released, aligning with efficient resource management in telecom networks. This ensures both lower-layer resources and service data adaptation resources are properly cleaned up when no longer needed for a multicast session.