hplus0603, thanks for that first detailed reply. It helps me a ton.
At some point, I won't be able to bring down my "upper limit" anymore. So, assuming a frame rate value that works without tunneling (i.e. 30Hz)... there will come a time when my server won't be able to handle more clients because I won't be able to guarantee each frame takes 1/30s. That's when I would need to add servers, correct?