Implementation of a layer 7 BSD firewall

Peer-to-peer (p2p) traffic not only encourages illegal distribution of copyrighted material but also takes most of the bandwidth, therefore reducing the service quality of business critical network applications. While corporate firewalls are trying to address this issue by blocking certain TCP ports, p2p applications avoid those by disguising as well known applications such as HTTP, HTTPS, SMTP or instant messaging which are allowed by most firewalls. Therefore application layer content inspection is required to limit or block such unwanted traffic. In this context we propose and implement a layer 7 firewall for BSD based software routers.