There's no "game network protocol". I mean, it depends on the game. It is not the same for action games, simulation, turn based strategy... Each one has different needs.
If the one you're using works, then work on it. You can trace the net traffic and see if there are parts that can be optimized, specially the most common messages.
Also a "prediction algorithm" will help a lot to speed up things as it allows to reduce the frequency and number of messages needed.
Also, if you're interested on games, then you should join the
Pascal Game Development community.