Question: Upon receiving an SGsAP-IMSI-DETACH-INDICATION message, what action does a Visitor Location Register (VLR) take if the received name matches the stored name and the SGs association state is not SGs-NULL?
Option 1: The VLR updates the stored name and sends an SGsAP-DETACH-ACK to the Mobility Management Entity (MME).
Option 2: The VLR moves the SGs association state for the User Equipment (UE) to SGs-NULL, marks the UE as detached if no signaling connection exists, and marks the association as "IMSI implicitly detached for EPS and non-EPS services".
Option 3: The VLR ignores the message if the UE has an existing signaling connection.
Option 4: The VLR sends a new SGsAP-IMSI-DETACH-INDICATION back to the MME for confirmation.
Explanation: This is the correct procedure as per the specified behavior when a VLR receives an SGsAP-IMSI-DETACH-INDICATION message with a matching name and a non-SGs-NULL state. It ensures proper detachment handling for both EPS (Evolved Packet System) and non-EPS services, updating the UE's and SGs association's states accordingly.