Something like...RdN said:Man.. NT1 is just as unplayable as Campaign and Firefight from previous Halos. Seriously, I don't understand why Campaign and Multiplayer don't use the same netcode.. I'd be very happy if someone explained it to me.
In Matchmaking, there's only one server, everyone else is a client.
In Co-op/Firefight, every player is its own server, and every server need to be 100% completely synchronized with the others (lockstep). It's a lot more network overhead.
Why they do it this way, I'm not sure. But I've heard mention it's how the only way to keep the AI all organized.