A ordinary Asterisk server installation does not neccessarely need that amount of open ports to "work".
First of all the IAX2 protocoll normally useses only one port, UDP 4569 and can be used for (some) clients and for server to server connections. (I also use UDP 53 as an alternative, to come trough from "everywhere".)
For SIP I have configured my Asterisk server to use only a few ports: UDP 5060 + UDP 10000-10010. (By nature I don't like to see a wide range of open ports, so I will automatically start to reduce it down to smething less, just an idea.)
It have worked fine for a couple of years. I have allways believed that the reason it works is due to a low level of traffic in a private home, and that more traffic will require more open ports. (But this is just a some kind of believe, I dont know if its right.)
This setup is used for a "manually configured" standard Asterisk server.
Confiuration of UDP 4569 for IAX2: iax.conf
Configuration of UDP 5060 for SIP/calling: sip.conf
Configuration of UDP 10000-10010 for SIP/voice: rtp.conf
I think Skype does not use TCP 80 or 443 as first or default ports. Those are both "backup ports" if the standard ports don't work. I did some traffic analysis on Skype before, but I forget. I think it were some other TCP ports.
And to fresh up my memory, I Googled a bit:
http://www.skype.com/help/guides/firewalls/technical.htmlIt looks like it would be difficult to give some priority to Skype, but for IAX2 and SIP, it should actually be possible (!!??)
I don't understand this guide completely, but it might give some ideas to get started:
http://www.voip-info.org/wiki/view/Linux+Router... Well thinking it ower .. the guide from voip-info.org might work directly, and more or less, "as-is" for a Linux gatway router, that has no other purpose than giving priority to ip telehony traffic. It will on the other side not work at all as an "as-is" implementation at the SME server, that has a bit more complex traffic pattern than "the pure Linux router".