Computer Help: Game lag on university network?

Before coming back to school, I bought a copy of Halo for the PC and played a lot of the multiplayer. However, after coming back to school, the multiplayer has been incredible laggy. By that I mean constant jerky walking, sometime warping right off the edge of a map while walking by it. I've tried reboots, bumping down the graphics, unplugging & replugging my ethernet cable, and getting a new IP address. Is there anything I can do, or is it a problem with trying to play on a protected & firewalled university network? Thanks.

no school = no one using the univ. network
school = everyone using the univ. network

most likely the university's bandwidth is getting sucked up by a bunch of other people trying to do the same thing, plus all the normal people going about their usual surfin'

Spybots, malware, Trojans...? Any defence against those buggers? Shut down all those backround tasks permanitly, too.