Lag = Latency = Sloppy connection between your computer and the server.
Therefor, Lag is not = Sloppy performance by your computer.

You can play lag-free on a 28.8kb modem, as long as your computer has a connection to the server without any latency (which is hardly possible with any dial-up modem), and if your computer is strong enough to run the crunchy game code.
So it\'s not allways possible your 56k modem isn\'t the cause for lag, even though the game uses only 1-2 kb/s., but I would say it\'s mainly \"your\" computers that are too slow (because mine is just soooo fast, you know).
