Question: When is the Header Compression Configuration Information Element (IE) included in a message?
Option 1: When the UE wishes to re-negotiate header compression configuration associated with an EPS bearer context and both the UE and the network support Control plane CIoT EPS optimization and header compression.
Option 2: Only when the UE is operating in dual-registration mode and has received the interworking without N26 interface indicator set to "interworking without N26 interface supported" from the network.
Option 3: When the UE wishes to establish a new EPS bearer context, regardless of whether control plane CIoT EPS optimization and header compression are supported.
Option 4: Never, as header compression configuration is not negotiable between the UE and the network.
Explanation: The Header Compression Configuration IE is included in a message when the UE wishes to re-negotiate header compression configuration associated with an EPS bearer context, provided that both the UE and the network support Control plane CIoT EPS optimization and header compression. This allows for efficient use of radio resources by compressing headers in packets transmitted over the EPS bearer.