This is the first of the Thomson Alcatel modedem's pages

In this device the settings for Port Forwarding are called NAPT

They are Accessed is Advanced > NAPT, as shown by the yellow higlights and arrows.

At this point the actual screen you see will have a smaller gold section at the bottom but hwere it currently says "Apply" will say "New". Clicking "New" will expand to this view. The view shown here shows "Temp" entries because NAPT is not ON for this device.

The arrows then lead to where I have entered "This for Your IP" is where you type the IP of your computer (or router if that is the next device).

I have gone straight past the "Outside IP" box as this setting of 0.0.0.0 is the recognised way of accepting incoming data from anywhere on the Internet (which is what you want with iChat or any online game for that matter).

Just above that is the Protocol choice.

I have gone on to enter the incoming (strangely labled "Outside") port of 5190 and then the port on the next device ("Inside"). As we want anything coming to the modem on port 5190 to go to the next device on port 5190 both are the same.

This device can only enter one port at a time. It needs, therefore a total of 31 entries for the fact two of the ports rewuire UDP and TCP to be set and this device does not have a "Both" or "Any" setting in the Protocol choice.

This set of three pictures are mainly to show the differences between this and the Linksys pages. I hope that from between the two sets you might fathom your own device(s) better.