on the pc clans setup their own games servers to play on, where as the consoles only use P2P, should that be console to console lol, hence the very high levels of lag with high ping rates
cod:mw2 on the pc uses a similar system to the consoles,someones pc is the host not a remote server, so my ping is almost always over 120 where as the pc servers i play on with cod:mw1 i have a ping of around 26, the lower the number the better
google ping and lag.
if you only play console games then you'll be totally amazed at the difference when playing on a remote server on the pc