Question: During an S1-handover with a change of Mobility Management Entity (MME), what procedure is typically executed afterwards, which also applies to specific inter-RAT scenarios?
Option 1: NAS Security Mode Command Procedure
Option 2: Tracking Area Update (TAU) Procedure
Option 3: S1-Handover Confirmation Protocol
Option 4: UE Security Capability Update Process
Explanation: After an S1-handover with a change of MME, or during specific inter-RAT (Radio Access Technology) handovers to E-UTRAN, and for both inter- and intra-RAT idle mode mobility resulting in an MME change, a Tracking Area Update (TAU) procedure is executed. This ensures the network updates the UE's location and other necessary parameters under the new MME.