I live in canada but i have 2 friends that live in the UK. When they finallly got their halo 4 copies we started playing it. When we play war games everything seems to be fine, but whenever we try to play coop campaign or spartan ops only the 3 of us, we always experience lag. We have tried everything : we have switched our internet from wifi to wired and we have forwarded our ports. If anyone knows a solution to this problem, please post a comment.
You live on different continents, there is no solution. You should be experiencing lag in customs and MM as well so that makes no sense.