On last GDC (Game developers conference) Michael Stallone, lead softrware engineer from NRS gave an almost 1 hour talk about implementing rollback netcode.
If anyone is interested what it took to switch from one of the worst to one of the best netcode in business, here it is.
The talk is really great and explains a lot of details I don't think are not commonly known. You don't need to be technical person to enjoy this. I recommend it for anyone.
Technical insight of GGPO netcode by NRS