universal plug and play firewall - similar feature on linux oes it exist?

["Angel Gabriel" <angel daddyt co uk>]

I run an internet cafe, and I would like for people to be able to run
instant messaging programs on the network, but be able to use them to their
full functionality, i.e. file transfers, voice conversations etc. Has anyone
been able to implement a Linux based firewall that allows ICS/NAT to
function fully? In case people are not sure what a Upnp Firewall is...

http://www.microsoft.com/WindowsXP/pro/techinfo/deployment/natfw/winmesconfi
g.asp#winmesconfig

This is a link that may help in understanding what it is.

Any help would be appreciated, thanks in advance!