Question: What happens if an MME doesn't receive an SGsAP-EPS-DETACH-ACK message after sending an SGsAP-EPS-DETACH-INDICATION message and the timer Ts8 expires, up to a maximum of Ns8 retries?
Option 1: The MME transitions the SGs association state to SGs-ACTIVE.
Option 2: The MME initiates a new EPS session for the UE.
Option 3: The MME sends an SGsAP-EPS-DETACH-INDICATION message to all neighboring eNodeBs.
Option 4: A report is made to the O&M system, with the SGs association state remaining SGs-NULL.
Explanation: This correct answer reflects the procedure outlined for abnormal cases where acknowledgement is not received. The MME, after retrying up to Ns8 times without receiving an SGsAP-EPS-DETACH-ACK, will report the issue to the Operations and Maintenance (O&M) system. Throughout this process, the state of the SGs association remains unchanged at SGs-NULL, indicating no active association. This highlights the importance of error reporting in telecom networks for efficient management and troubleshooting.