What ports do I need to open for Fios Firewall in order to run Call of Duty Modern Warfare 2 on my computer?

I have run Call of Duty MW2 online multiplayer successfully for a month now when all of a sudden, the multiplayer menu says my NAT is too strict and I suddenly can't connect to any multiplayer matches. Since then I have figured out how to open the ports(UDP and TCP), but do not know which specific ports and which specific triggers for each port should be used. I have looked for over two hours online to find some directions but they all contradict each other and none have yet to work. Could somebody please give me coherent directions!!!