Question: When should a User Equipment (UE) include an RRC Transaction Identifier in an Uplink (UL) message, according to 3GPP guidelines for Radio Resource Control (RRC) protocol?
Option 1: Always, in every UL message to ensure consistent network tracking.
Option 2: Only when the UE is transitioning from RRC-Connected to RRC-Idle state.
Option 3: When the UL message is either a direct response to a Downlink (DL) message with an RRC Transaction Identifier or requires a direct DL response from the network.
Option 4: Never, as it is only required for network-initiated DL messages.
Explanation: Including an RRC Transaction Identifier in UL messages that respond to identified DL messages or those expecting a direct network response enables the network to correlate messages effectively, ensuring efficient communication and resource management in the RRC protocol.