Question: What is the primary action taken by the Mobility Management Entity (MME) when initiating an Implicit IMSI Detach from EPS services for a User Equipment (UE) with an established SGs association?
Option 1: Update the UE's EMM context to reflect a new location area.
Option 2: Notify the Serving Gateway (S-GW) to release UE's bearer resources.
Option 3: Initiate a handover procedure to another base station.
Option 4: Delete the UE's EMM context or mark it as detached based on predefined criteria.
Explanation: The Implicit IMSI Detach from EPS services is a procedure where the MME, based on specific criteria (e.g., those outlined in 3GPP TS 23.401 for GPRS enhancements in E-UTRAN), decides to either delete the Evolved Mobility Management (EMM) context of a UE or mark it as detached. This action is crucial for managing UE states efficiently within the network, especially when there's an established SGs association and the network supports Idle Mode Signaling Reduction (ISR). The correct answer reflects this key aspect of the procedure's purpose.