So I never lag in online multiplayer in this, or any other game, or any other game that has online co-op. Yet for some reason I get crazy lag when playing Halo games co-op online. Both Halo: Reach and Halo Anniversary were exactly the same. Anytime I'd try to play a game with my brother one of us would stutter and lag so bad it made the game unplayable.

Yesterday I tried to play Halo 4 with him and had the same result. My NAT is open and there should be no issue. I can play any other game without the slightest issue, it's always Halo that does it, and again only in co-op.

My question exactly. I see no one has an answer around here.

I was wanting to go back and play all 50 Spartan ops missions with a friend but I fear that crippling lag...which is just fucking inexplicable to me, will be there to ruin the fun.

They've put in some effort to fix the mp a bit, and considering how much was put into this game up front, I just don't get why they have been so inattentive to problems and concerns the gamers have been vocal about. Oh yeah, they aren't Bungie...sorry but I had to say it.

Because it has to keep track of enemy positions based on the host's game. Not a good excuse, but I assume that's why it lags in Campaign and Spartan Ops while PvP netcode is much smoother. I'm pretty sure Bungie's Firefight/co-op Campaign had the same issue.

No they didn't; not for me at least. Absolutely something new in Halo 4, and I've played a ton of every game especially in co-op(so many hrs. co-oping in Reach and it worked flawlessly). In those games one player might occasionally experience some slowdown, but that was each person's connection issue(s). This seems to me to be persistent across every game and player. Same laggy performance for me if I play w/a friend 10 miles away as one 3000 miles away, as well as with two, three, or four players. And the mp in Halo 4 runs fine. Too weird. Weapons disappearing super fast in Spartan-ops is also unique to 343's Halo 4 experience btw.

bad net code? maybe the game has trouble communicating all that AI info to other players across a network, I also had the same problem in Halo Reach. Just played the solo firefight mode after a while because i got sick of trying.