The "easy" fix is actually really hard (Destiny)

by Kahzgul, Wednesday, December 16, 2015, 17:41 (3360 days ago) @ MacAddictXIV

The way to prevent lag switching is to have a true host player whose system broadcasts all player and projectile movement. Hosts are picked for stable, fast, reliable connections, so anyone who lag switches would fall off the "potential host" list pretty quickly (and switching while hosting would result in a host migration). Under this set-up, any lag switcher who stopped sending outbound traffic would stop moving and shooting as far as the host system was concerned. They would still take damage as per normal, so lag switching would be a complete detriment to their play. This is the system Call of Duty and most competitive FPS games use.

In Destiny, the netcode is designed to favor smooth visuals over reliable hit boxes. The game interpolates movement paths for laggy players based on their last available packet (which is why you see laggers running into walls sometimes), but it doesn't interpolate their hit boxes. Rather, it seems to broadcast to all players where bullets went, and rely on reply packets from those players to say "I was hit by a bullet!" which means that, when someone lags, your system guesses where they are and shows you that, but they're actually somewhere else - and you won't know until their packets catch up.

So fixing this issue would be a complete rewrite of the netcode for the entire game (I'm guessing the game uses identical netcode for PvE and PvP scenarios. Not likely to happen, ever.

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A seemingly smaller (but still hard) change, would be to turn off graphic interpolation during PvP matches, so you'd never see a phantom lagswitch character running around where his hitbox isn't. But this may actually be a fundamental feature of their game engine, so it could be just as much work as rewriting the netcode to be more trustworthy all around. I can't say.

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What's clear to me is that the current model of reporting bad actors sucks. The deterrent isn't enough to keep them from lag switching, and they're ruining competitive play modes of PvP for all of us.