Some quick technical commentary:
The bandwidth calculation in the article is predicated on sending updates at 60 hz -- or what we'd in the Descent community call 60 PPS. Probably because the screen is refreshing at that rate? It's unnecessary. You want a high framerate for control of your own game, but you don't need it to see enemies smoothly. Remember, movies only run at 24 FPS. ;)
The highest I allow in Descent is 30 PPS, and really . . . it's seen as a luxury. 20 is generally fine. Sometimes I play games at 10, and there you can definitely tell -- even with the smoothing (it sends velocity and acceleration, too, and interpolates) -- but it's perfectly playable.
Which is something worth remembering. With old school games, "crappy but perfectly playable" is actually all they were able to achieve.
No, the physics engines aren't perfectly locked, and how tolerable this is will depend on your game. In a simple FPS, this really isn't a big deal. You just lag lead (compensate in aim, both for the motion of your enemy, and the fact that the data is old). :)
Some of how he's proposing to send the data is wasteful. He initially proposes sending "is weapon equipped" and "is firing" as 1 byte a piece -- and later concludes he can get those in 1 bit a piece. True. That's a savings by a factor of 8 right there. But I can do you one better -- don't send it every update. How often do those states really change?
In Descent, we have two classes of data: position and orientation data that's sent at a steady rate (10-30 PPS), and event data that's sent . . . whenever it happens. Equipping weapons is definitely the second type; it happens extremely rarely -- like, seconds pass between weapon switches. :)
One thing that may surprise you. We don't send "is firing" as a flag with every packet -- we send one packet per shot taken! Two reasons for this: one, it's actually lower bandwidth. Shots fire rarely -- our fastest gun fires 20 bullets per second, but the next fastest fires six. Then five, then four, then . . . one shot every two seconds. And you're not always firing, either. Sending one packet per shot saves bandwidth. But it also increases accuracy! We attach those shot packets to a position and orientation update, so -- even if the receiver has incorrectly interpolated your position -- the shot goes exactly where you intended it to. This is very important. :)
As a player (and a programmer -- but mostly a player), I'm concerned about the article's conclusions about the value of prediction, and the recommendation to avoid position popping by applying smoothing -- to quote the article, "it ruins the virtual reality of the game".
Ok, yes, it does. But the thing is, you have a choice here. You can present your players with something pretty and smooth that is fundamentally a lie, or with something jittery that is the best knowledge you have about where the enemy is. This is a fundamental tradeoff: versimiltude or accuracy. You can't have both.
My players overwhelmingly prefer accuracy. To them, the avatars on the screen are targeting aids, and they understand that the data is old and a bit lossy and bursty sometimes, and they want the best data possible so they can take the best shot possible. :)
I suppose your mileage may vary by audience. Mine's been playing this game 20 years and "crappy but playable" is both normal and good to them. :)
But -- I can't imagine this would be different in another FPS -- taking a shot that you know is good on your screen, and have it not hit the other guy . . . that's rage-inducing right there!
Yeah, networked games are hard. For sure. And there are fundamental hard tradeoffs involved in engineering them. For sure. But it's an interesting problem, and also worth it. :)