It’s a good idea to add actual information that’s been suggested specifically by SNKP which is how to achieve NAT1. Forwarding Ports is great, but realize that there are really 3 levels of actual connection settings you can achieve.
NAT3 being the worse and what I assume is most people’s method of connection. This means that you’re running wireless, even with the most optimum settings, this is the worst thing you can do for frame specific gaming.
NAT2 is a happy medium. It can add up to a few frames of delay if the netcode is crap or your router isn’t configured properly, but in general it’s great for online gaming if both sides are working properly. This setting is when you are connected through a router. There’s no way to achieve better than this as long as your router is there, only worse.
NAT1 is all about the quality of your connection. It’s when you have the internet cable from your modem plugged directly into your console. In this way, you don’t have to worry about port forwarding or anything. It’s the fastest possible connection for online play that you can have since if the only place the internet is directed to is your console, there shouldn’t be any hiccups or divergence of data that could mess up anything.
Now SNKP Development suggested you go down to NAT1, but that’s ridiculous honestly. NAT2 should be sufficient and it works rather well with properly coded online games like SF4/BB. The port forwarding information above is only useful for achieving best possible conditions for NAT2 type network settings, NAT3 sucks, don’t kid yourself.