Comcast admits it can do the impossible

'We will stop busting BitTorrents'

The Cover-up

Martin has also said there's another matter that deserves a bit more scrutiny. For many months, Comcast denied it was busting BitTorrents, and even now, the company stops somewhere short of telling the whole story.

In late 2006 and early 2007, an independent researcher named Robb Topolski first noticed that Comcast was clipping at least some of his peer-to-peer uploads. By May 2007, his tests showed that the ISP was preventing users from "seeding" BitTorrents and other P2P files. When one machine downloads a file and promptly attempts to upload that file to another machine, in certain cases, Comcast sends out a duped "reset flag" that breaks this peer-to-peer connection.

"I retested this every few weeks," Topolski says. "Each time, Gnutella was totally blocked. eDonkey was 75 per cent blocked. And BitTorrent was 40 per cent blocked." In other words, Comcast was sending reset flags to 40 per cent of his established BitTorrent connections.

Several months later, in August, Topolski's tests were trumpeted by the P2P-obsessed blog TorrentFreak, and when The Register phoned Comcast, the company flatly denied the practice.

Then, in November, The Associated Press published tests that confirmed Toploski's findings. At this point, Comcast told us that it was "managing" BitTorrent traffic rather than "blocking" it. But in clipping BitTorrent connections with reset flags, the company is indeed blocking BitTorrent traffic.

After The AP's story hit, several members of the SaveTheInternet coalition formally asked the FCC to investigate Comcast's behavior and the FCC said OK. By January, with a letter to the FCC, Comcast told the world a bit more about its "management" techniques. But it appears the company was still hiding at least a portion of the truth.

Comcast says it only "manages" BitTorrent uploads "during periods of heavy network traffic" and "when the customer is not simultaneously downloading." But independent tests tell a different story.

Topolski says that Comcast is blocking 40 per cent of his uploads at all times of the day. "Middle of the day. Late at night. Weekends. Weekdays. The results are always the same," he says.

His tests also show that uploads are blocked while he's still downloading. "Comcast starts interfering as soon as any of your downloads switches to an upload mode," he explains. "It doesn't wait until all your downloads are done." So if you've just finished downloading File A, Comcast may prevent it from being uploaded - even if File B is still downloading.

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