Table Tennis Touch isn't demanding on bandwidth but it is a super fast game so it is sensitive to high latency and packet loss. We do a lot behind the scenes to try and minimise this but if your (or your opponent's) internet connection suffers from high latency, then it's likely that you'll get disconnected as the messages aren't getting through as fast as the ball is crossing the table. The network meter in the game tells you what the ping time is to your opponent so you should get some warning.
Also consider geography - if you get paired with someone halfway around the world, even an amazing internet connection won't be able to get you guys playing a smooth match.
One more thing...if you're on iOS, there appears to be a bug in Game Center which means that some multiplayer connections will get disconnected around 45 seconds after the initial connection. We think it's a problem with certain routers and hope that a future iOS update will fix this. If you see a consistent pattern of being disconnected, then you could try a different router to get around this problem (if you have one available). It's not ideal and we wish we could fix it but what happens behind-the-scenes with Game Center is sadly out of our control. 🙁