Is it my NAT type, or my xbox?

I'm having trouble finding matches on red dead redemption free roam, call of duty 4, modern warefare 2, and sometimes black ops. I can get into parties or play when my friends invite me, but I can't get into matches myself. I've read about red dead redemption problems, my screen says "cannot find a match due to connection issues with other players" many other people have that problem, too. Is it NAT type? Or something wrong with my xbox?