Question: What is the primary criterion for defining a new feature in GTPv2 functionality?
Option 1: Addition of a new parameter to an existing message.
Option 2: Extension of an existing message over a new interface.
Option 3: A function that has significant meaning to the operation of GTPv2 and is independent from other features.
Option 4: Definition of a new GTPv2 message for a minor functionality.
Explanation: According to the definition, a feature in GTPv2 is a function that extends the base GTPv2 functionality and has significant meaning to its operation. This means that the primary criterion for defining a new feature is not just about adding a new parameter or message, but rather about introducing a function that substantially impacts the operation of GTPv2.