1) You need to assign a static ip to your ps3 so that your router will always find your ps3 on the same ip address.
2)Go to Settings > Network Settings > Internet Connection Settings on the XMB and Select custom and Insert all that apply to you for example Wired, Wireless and when you get to Address settings STOP!
3)You will see IP Address, Subnet mask, Default Router, Primary Dns and Secondary DNS.
4)For IP Address you should put in something that the router won't assign to a different device like 192.168.1.101
5)The Subnet Mask is always set to 255.255.255.0
6)The Default router is your routers IP address. In most cases it will be 192.168.1.1 but to check you should find a computer, go to start, type in CMD and hit Enter. A command prompt should pop up and you should type in ipconfig. You will be looking for
Default Gateway at the top and then put that on the PS3 for Default Router.
[ATTACH]3555[/ATTACH]
7)Both the primary and secondary DNS Should be set the same as the Default Router.
8 )Hit right on the D-Pad then and select MTU Automatic.
9)Proxy-Do Not Use
10)UPnP-Enabled. Save The settings and test connection.

1)Remember the Default Router from above? Type that in Your address bar and this will take you to your router page. There will be some type of login, and if you don't know it google your router brand for default password.
2)Now on your router you will be looking for DMZ or DMZ host. If you have a linksys router or Cisco router then your DMZ will be under applications and Gaming. Once you are there it will have a place to put a destination IP address and that is where you put your PS3's Static IP from earlier. If it asks for source IP put any, or your pc's IP.
3)Save the settings on the router and you're DONE!!!