Question: What action should a GTPv2 entity take when receiving a GTPv1 message if it does not support GTPv1?
Option 1: Return a Version Not Supported Indication message and process the received message.
Option 2: Silently discard the received message.
Option 3: Send an error message to the sender indicating that GTPv1 is not supported.
Option 4: Upgrade the received message to GTPv2 and process it.
Explanation: According to the specifications, if a GTPv2 entity does not support GTPv1 and receives a GTPv1 message, it should silently discard the received message. This ensures that the entity does not attempt to process an unsupported version of the protocol.