Comcast Filtering File-Sharing Traffic

Comcast Filtering File-Sharing Traffic

In a small series of tests, the Associated Press has concluded that U.S. cable operator Comcast is using filtering technology to actively prevent users from uploading files via the popular file-sharing application BitTorrent.

To test claims that Comcast was somehow blocking file-sharing traffic, the Associated Press attempted to download the (uncopyrighted) King James Bible from two computers—one in Philadelphia, and one in San Francisco—both of which were connected to the Internet via Comcast service. The AP reports that in two out of three attempts, the download was blocked altogether, and in the third test the download began only after a ten minute delay. When the AP attempted to upload files requested by other BitTorrent users, the connections were also blocked.

A test with a third computer in the Boston area connected to the Internet via Comcast did not seem to encounter similar problems. The AP encountered no evidence of blocking BitTorrent uploads or downloads on Time Warner cable, Cablevision, and an AT&T business connection in the AP headquarters.

Analysis of the traffic to the Comcast-connected system in San Francisco revealed the failures were due to the receipt of “reset” packets, which tell a receiving BitTorrent computer to cease communications with the sender. However, the reset packets did not originate with either computer in the connection, meaning they were generated by a third system with falsified IP information. The AP concludes the reset packets were most likely generated by Comcast; the AP also claimed to receive reset packets from Comcast addresses when downloading BitTorrent content using the Time Warner connection.

“Comcast does not block access to any applications, including BitTorrent,” Comcast spokesman Charlie Douglas told the AP.

Net users have been speculating for some time how Comcast and other large service providers are working to manage inbound and outbound traffic from BitTorrent (which is trying to remake itself as a platform for distributing protected content), as well as file-sharing services like Gnutella and eDonkey. Net neutrality proponents would be quick to point out that Comcast’s apparent efforts to block BitTorrent uploads are, in this case, interfering with a completely legitimate sharing of an uncopyrighted work; Comcast—which has consistently opposed legislative efforts to define network neutrality—has said only that it tries to manage its network so all users get the best possible broadband experience.

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