I've written a lot of posts about various methods for blocking <acronym title="Peer-to-Peer">P2P</acronym> traffic, especially with Cisco's Network Based Application Recognition (NBAR). Although these posts are probably of interest to smallish Internet Service Providers and administrators of business networks, they don't have much use for the average broadband customer. If you're a BitTorrent user and tired of having your P2P traffic squeezed by your ISP, here are two things you can do to try and defeat that traffic shaping. (These are probably obvious for you BitTorrent veterans, but new users might not be aware of them.)

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1. Change your BitTorrent's client default port.
   By default, many BitTorrent clients use TCP ports 6881 through 6999 for communication. The easiest thing for any network administrator to do is deny access on that port and prevent any BitTorrent traffic. To get around this, make sure you use a BitTorrent client that offers the ability to change what port(s) it uses.
2. Encrypt your BitTorrent traffic.
   Many BitTorrent clients now support encryption between peers. The encryption is meant to confuse traffic shapers by hiding what's actually going on inside the traffic stream. From personal experience, I can tell you that using RC4 encryption effectively bypasses NBAR as of IOS 12.4.

Finally, let me take a moment to point out that I do not condone the trade of pirated software, movies, or music. Although P2P file sharing is often associated with these activities, there are legitimate uses of the technology. For example, Blizzard distributes it's World of Warcraft patches via BitTorrent.

I should also point out that while these methods may be affective, they are in no way foolproof. I've actually heard of some ISPs shutting down customers based on traffic pattern (long periods of high download speed followed by long periods of only uploading).

Photo by Igor Badalassi.