Filtering out P2P traffic

Hello!

In an educational institution I use Solaris 10 on the gateway between  
internet and internal network. I would like to filter out P2P  
traffic. But since the P2P clients can use any port which is open for  
traffic, I would need to do content-based filtering.

Is possible to block P2P traffic with the IPFilter included in  
Solaris 10? I see in the IPFilter FAQ (http://www.phildev.net/ipf/ 
IPFques.html#ques36), that you can do "simple matching of content for  
TCP session startup" on the first 16 bytes. But that means I need to  
find out what to match for all P2P protocols. Also, I could not find  
on docs.sun.com if this kind of rules are supported in IPFilter  
integrated in Solaris 10.

I do not want to block anything else except P2P. There are many  
protocols which I would like to go though like SSH, VNC, RDC etc.

What options are there to build such filter on Solaris? Is there any  
other free/cheap option to do it? If not, is it possible to slow down  
P2P traffic via IPQoS?


Regards,
Damjan