SFV's implementation has one very major and serious issue that remains unfixed since launch. Read that article I linked for more info on that.
All netcode solutions, whether driven by input delay or rollbacks, must keep both systems running completely in sync. This means both systems are showing each player the same frame at the same time, or as close to this as possible. Even though most fighting games try to lock the framerate at 60fps, it is not simply enough to sync at the beginning of a match and assume the players will remain in sync for the whole fight. Many issues outside of networking, such as consoles overheating, computers performing operating system functions, or someone temporarily overloading their CPU, can cause performance drops which will put them out of sync with their opponent.
The consequences of not correcting this sync are catastrophic. Consider a rollback system where player A is being shown frame 20, but player B is being shown frame 23, across a network delay of 3 frames. Player B will send input for their frame 23 to player A. Because they are on frame 20, the network delay means they will receive the input on their own frame 23, which is just in time to execute it and will not have to roll back at all. Meanwhile, player A sends their input for frame 20 to player B. With the network delay, player B will receive this input on their own frame 26, which will repeatedly cause lots of very uncomfortable 6-frame rollbacks.
Note that this rollback is entirely one-sided; only the player who is ahead of the other will experience the effects of the bad connection. Tony Cannon, in many ways the founder of modern rollback with his invention of GGPO, theorizes that this is one of the flaws of Street Fighter V's rollback system, and proper clock syncing might go a long way to addressing SFV's poorly received online play. Some fans have even run their own tests and come to similar conclusions
Hm... This is really interesting. Thanks!
