Network archicteture for simple 2D realtime multiplayer game

[Safadurimo]

Hi,
I've written a simple 2D-Game (You can imagine something like "pong") and now I would like to add a network mode. What would be the right Network archicteture for this? Is there any example code out there?
Thanks a lot for your help,
Safadurimo

[Nate]

Shameless plug of my own project:
http://code.google.com/p/kryonet

[taksan]

I also wrote a tutorial on how to write 2D and 3D multiplayer games with java, here it is:

http://code.google.com/p/lucu

hope it helps