MS Messanger voice thru SuSEfirewall

Hi all, Thanks for the answers to the previous question - my internal samba now works. My next problem is that I'd like to use MS Messenger voice thru my firewall. I've seen projects such as upnp and Linux UPnP Internet Gateway Device project, do I need to use them ? As you can guess I'm a very inexperienced iptables/firewall user, so I'd really appreciate any help you can give. Thanks CPH