While Wikis have been made to track which ISPs throttle BitTorrent traffic, the information has never been all that reliable. The practice of using Wireshark to test your connection is also a little too tricky for some users. So the developers of the BitTorrent client Azureus recently released a client plugin that would test whether an ISP was throttling or disrupting BitTorrent traffic automatically.

Since release of the plugin, Azureus has collected some 1,000,000 hours worth of data from over 8000 users and compiled the data in this report (via Torrent Freak). The data shows that while Comcast is the leader when it comes to forging TCP packets to throttle BitTorrent upstream traffic, they certainly aren't alone (we documented the same practice by Cox last November).

The plug in constantly monitored the rate of network interruptions occurring from RST (“reset”) packets by measuring the total number of attempted network connections and the total number of network connections that were interrupted by a reset message. Comparing the two values, provides the ratio of network connections interrupted by reset messages, some ISPs use less heavy handed network management practices and see are low on the list (Telecom Italia France sits at 2.53%), but here's the top offenders:

Comcast USA 23.72%
Cogeco Canada 19.13%
Emirates Internet UAE 17.86%
Cablevision USA 17.58%
Brasil Telecom Santa Catarina, Brazil 17.43%
TM Net Malaysia 16.80%
BellSouth USA 15.88%
Tedata Egypt 15.33%
Tiscali UK 14.89%
AOL USA 14.88%

"While we cannot conclude definitively that any particular network operator is engaging in artificial or false RST packet behavior, it is possible to compare the median experience of different users operating in different ASNs," says the report. While they admit they need more data, they claim "there is sufficient data to at least raise questions about whether particular network operators are taking steps to artificially interrupt network connections."

Of course with evidence proving Comcast forges TCP reset packets the data is in some way verified, but at the same time the data doesn't differentiate between packet forgery and genuine TCP resets. The inclusion of BellSouth in the list (a carrier that traditionally has dodged this type of heavy handed network management) raises more questions than it answers.

Update:Vuze/Azureus has apparently e-mailed AT&T with their findings, in a quest to find out more. From a letter sent from Vuze CEO Gilles BianRosa to AT&T CEO Randall Stephenson: