Question: When is the UE required to include the IP header compression configuration Information Element (IE) in a message?
Option 1: Only when the PDU session type value is set to "IPv4" and the UE indicates "Control Plane CIoT EPS optimization supported".
Option 2: When the PDU session type value is set to "IPv4", "IPv6", or "IPv4v6", and both the UE and network indicate support for control plane CIoT 5GS optimization with IP header compression.
Option 3: Only when the UE indicates "Control Plane CIoT 5GS optimization supported" in the 5GMM capability IE of the REGISTRATION REQUEST message.
Option 4: When the PDU session type value is set to "IPv6" and the network indicates "Control plane CIoT EPS optimization supported" in the 5GS network support feature IE.
Explanation: The UE includes the IP header compression configuration IE when specific conditions are met, including the PDU session type being set to "IPv4", "IPv6", or "IPv4v6", and both the UE and network indicating support for control plane CIoT 5GS optimization with IP header compression. This ensures efficient use of resources in the 5G system by compressing IP headers when supported by both the UE and network.