Question: When is the UE required to include the Ethernet header compression configuration Information Element (IE) in a message?
Option 1: When the PDU session type value is set to "IP".
Option 2: When the network indicates support for user plane CIoT optimization.
Option 3: When the UE and network both indicate support for control plane CIoT optimization, but not specifically for Ethernet header compression.
Option 4: When all of the following conditions are met: the PDU session type value is set to "Ethernet", the UE indicated support for control plane CIoT 5GS optimization and Ethernet header compression in the REGISTRATION REQUEST message, and the network indicated support for these features in the REGISTRATION ACCEPT message.
Explanation: The correct answer requires a combination of specific conditions related to PDU session type, UE capabilities, and network support. This ensures that the UE only includes the Ethernet header compression configuration IE when both the UE and network have explicitly indicated support for control plane CIoT optimization with Ethernet header compression.