Question: What is the correct order of messages when piggybacking is used, as per the GTPv2 protocol stack?
Option 1: Triggered Response message, followed by additional information, and then the piggybacked Initial message.
Option 2: Triggered Response message, immediately followed by the piggybacked Initial message, with no additional information present.
Option 3: Piggybacked Initial message, followed by the Triggered Response message, and then additional information.
Option 4: Additional information, followed by the Triggered Response message, and then the piggybacked Initial message.
Explanation: According to the GTPv2 protocol stack, when piggybacking is used, a common IP header and a common UDP header shall be used for the triggered response message and the piggybacked initial message. The correct order of messages is that the Triggered Response message is immediately followed by the piggybacked Initial message, with no additional information present. This ensures efficient transmission of messages in the GTPv2 protocol stack.