The degree of traffic shaping varies a lot between different ISPs. Some only limit BitTorrent traffic during some times of the day or throttle in specific regions, others take a more aggressive approach and prevent their customers from seeding or even downloading .torrent files. The fact is, all the ISPs listed here have been caught – one way or another – messing with BitTorrent transfers.
BitTorrent throttling is not a new phenomenon, ISPs have been doing it for years. When the first ISPs started to throttle BitTorrent traffic most BitTorrent clients introduced a countermeasure, namely, protocol header encryption. This was the beginning of an ongoing cat and mouse game between ISPs and BitTorrent client developers.
Some people might wonder why ISPs throttle their connection. The argument most often used is that all the BitTorrent traffic on their network slows down other customers’ connections. An argument that makes sense (if it is true), but the real problem is that ISPs tend to be secretive about their throttling efforts. My advice to them, if you decide to limit BitTorrent traffic, be open about it and don’t advertise unlimited bandwidth.
So who are these ISPs? Here’s a brief overview of some of the bad guys, take a look at the Azureus wiki for an regularly updated list of throttling ISPs (worldwide).
The Canadian ISPs Shaw and Rogers were the early adopters of BitTorrent traffic shapers. The first reports date back to 2005, and earlier this year Rogers even decided to block all encrypted traffic, just to make sure that BitTorrent protocol encryption didn’t work.
Other Canadian ISPs that are known to throttle or limit BitTorrent traffic are Bell Sympatico, Cogeco, Eastlink and Explornet. Rogers and Cogeco are the only ISPs that actively prevent people from seeding files on BitTorrent, similar to Comcast.
There haven’t been a lot of reports on British ISPs that mess with BitTorrent traffic, but this doesn’t mean that they don’t. Pipex, one of the largest ISPs in the UK, is notorious for it’s war against BitTorrent. They throttle BitTorrent traffic, especially during peak times, and they also throttle all encrypted traffic. Other UK ISPs that throttle BitTorrent traffic are BT Broadband, Freedom2Surf and TalkTalk. Virgin Media does not specifically target BitTorrent traffic, they simply throttle all traffic during peak times.
Hundreds of sites have reported on the Comcast throttling/interference issues, but Qwest and Atlantic Broadband do just the same thing. RCN/Starpower, Adelphia Cable Communications and Cablevision’s Optimum Online have found to prevent seeding, but do not throttle BitTorrent traffic.
As mentioned before, The developers of uTorrent, Bitcomet and Azureus added support for protocol header encryption to their clients. Encryption seemed to work for well in most cases, more details can be found here. If encryption isn’t working you might want to try one of the alternatives described in this article.