I've got a fair internet connection, and I'll be going through a mission without any significant amount of lag spikes or anything. However, the game will occasionally freeze up for a second, and then enemies will stop reacting and go through walls, players will stop moving, and chat becomes disabled. Nothing works, and so I surmise that the game has absolutely no connection to the game server. When I restart SK, I'll almost always find myself dead in the corner, including my emergency revive.