Question: When a UE is in 5GMM-IDLE mode with suspend indication and receives an idle suspend indication from the lower layers, what action does it take regarding the N1 NAS signalling connection?
Option 1: The UE considers the N1 NAS signalling connection released.
Option 2: The UE enters 5GMM-CONNECTED mode immediately.
Option 3: The UE shall not consider the N1 NAS signalling connection released and shall not consider the secure exchange of NAS messages terminated.
Option 4: The UE sends a pending initial NAS message.
Explanation: According to the provided text, when user plane CIoT 5GS optimization is used, upon idle suspend indication from the lower layers, the UE shall enter 5GMM-IDLE mode with suspend indication and shall not consider the N1 NAS signalling connection released. This ensures that the secure exchange of NAS messages remains intact even in a suspended state, allowing for seamless resumption when needed.