Question: When multiple CN nodes send MBMS CN DE-REGISTRATION REQUEST messages for a certain MBMS Bearer Service to an RNC with active NNSF, how does the RNC handle these requests?
Option 1: The RNC processes all requests simultaneously and sends separate MBMS CN DE-REGISTRATION RESPONSE messages to each CN node with a "Successful De-registration" cause value.
Option 2: The RNC only proceeds with the first received MBMS CN DE-REGISTRATION REQUEST message, responding to it without a cause value, while sending an MBMS CN DE-REGISTRATION RESPONSE with a "TMGI unknown" cause value to all other CN nodes.
Option 3: The RNC aggregates the requests and sends a single MBMS CN DE-REGISTRATION RESPONSE message to all CN nodes involved, indicating a "Multiple De-registration Requests" cause value.
Option 4: The RNC ignores all subsequent MBMS CN DE-REGISTRATION REQUEST messages after receiving the first one and does not send any response to the additional requests.
Explanation: This is because, according to the specified behavior for handling multiple de-registration requests when NNSF is active, the RNC prioritizes the first received request, completes the procedure with the respective CN node without a cause value, and informs other nodes of the situation with a "TMGI unknown" cause, indicating the RNC's handling logic for duplicate or subsequent requests.