Question: In SIPTO (Selected IP Traffic Offload) above RAN with GW selection, what triggers the SGSN to potentially allocate a different Gateway (GW) for a UE's new location?
Option 1: Receipt of a new PDP Context Activation Request from the UE
Option 2: Detection of UE mobility by the RAN, triggering a Location Update procedure
Option 3: SGSN's periodic network optimization scans for all active UEs
Option 4: Detection of UE mobility (e.g., at Routing Area Update - RAU) by the SGSN
Explanation: The correct answer is Option 4 because, according to SIPTO with GW selection functionality, when the SGSN detects UE mobility (for example, during a Routing Area Update), it may determine that the target SGSN should allocate a different GW more suitable for the UE's new location, ensuring optimal network resource utilization and minimizing latency.