My internet rarely causes trouble, but I have continually had problems with SF4 and PSN throughout their existence. Recently it seems even worse, particularly with SF. I run a wire from my router, and I forwarded the ports 5223, 3478, 3479, and 3658.
Other miscellaneous network settings I have and may not understand:
speed and duplex : auto detect
NAT Type: type 2
If anyone has solved their PSN issues I would love to hear a success story. Cheers.