Question: What should the UE do when it encounters an IE with an unknown IEI in a message that is not encoded as "comprehension required"?
Option 1: Send an error message to the network
Option 2: Ignore all IEs in the message
Option 3: Ignore only the IEs with unknown IEIs
Option 4: Abort the current procedure
Explanation: The UE should ignore only the IEs with unknown IEIs that are not encoded as "comprehension required", allowing it to continue processing other IEs in the message. This approach ensures that the UE can still understand and process relevant information in the message, while avoiding potential errors or conflicts caused by unknown IEs.