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Saturday, October 20, 2007

Comcast really does block BitTorrent traffic after all :Comcast Screws with File-Sharing Traffic

For a few months Comcast has been the subject of scattered reports that say it throttles BitTorrent traffic.

TorrentFreak said in August that Comcast was surreptitiously interfering with file transfers by posing as one party and then, essentially, hanging up the phone. But when we contacted Comcast at the time, it flatly denied doing it.

Thanks to tests reported Friday by the Associated Press, however, it's clear that Comcast is actively interfering with peer-to-peer networks even if relatively small files are being transferred.

The tests involved transferring a copy of the King James Bible through the BitTorrent network on Time Warner Cable, Cablevison, AT&T and two Comcast connections (in Philadelphia, Boston and San Francisco). Only the Comcast-connected computers were affected.

This is significant. The Gutenberg version of the King James Bible is only 4.24MB, which is relatively tiny and indicates that Comcast was singling out even small files.

Now, even though there's been some musing that Comcast can't do this, I'd be surprised if a court would say that it was somehow unlawful. Comcast's Terms of Service says: "You further agree to comply with all Comcast network, bandwidth, and data storage and usage limitations. You shall ensure that your bandwidth consumption using the Service does not exceed the limitations that are now in effect or may be established in the future. If your use of the Service results in the consumption of bandwidth in excess of the applicable limitations, that is a violation of this Policy...if the Service is used in a way that Comcast or its suppliers, in their sole discretion, believe violate this AUP, Comcast or its suppliers may take any responsive actions they deem appropriate.

Which is pretty broad.

The danger for Comcast is twofold. First, its hyperactive filtering may zap perfectly legitimate file transfers, which seems to have happened in one case involving a customer using Lotus Notes.

Second, it encourages countermeasures such as obfuscating BitTorrent traffic or encrypting it. That means that future efforts by Comcast to manage its traffic may be far more difficult. (If Comcast had merely slowed down BitTorrent transfers instead of cutting them off completely, users wouldn't be escalating this arms race as quickly.)

Probably the best result would be tiered pricing. BitTorrent users who are heavy users of bandwidth would pay more, while average home users would pay less. It's not perfect, and lots of Internet users may not like a tiered pricing model, but it's probably better than escalating a technological arms race, or not being able to use BitTorrent at all.

Comcast Screws with File-Sharing Traffic

Tests reveal Comcast meddles with P2P network connections

Independent testing performed by the AP has revealed that Comcast actively interferes with peer-to-peer traffic going to and from its high-speed internet subscribers, by impersonating users' machines and sending fake disconnect signals.

While traffic shaping - the act of throttling a given piece of Internet traffic based on its type, like BitTorrent or VOIP - is becoming increasingly common amongst ISPs interested in preserving quality of service, it seems that Comcast is one of the first companies that actively impersonate individual connections. Most providers will simply slow down some traffic in favor of others, or block a protocol's port number to prevent it from functioning.

According to the report, Comcast's technology affects users across many different networks, including e-Donkey, Gnutella, and BitTorrent. Robb Topolski, a former software quality engineer at Intel and Comcast subscriber, began to notice unexplainable performance problems with his P2P software. Posting to the popular forum, he collected similar reports from other Comcast users around the country.

In the case of BitTorrent, Comcast's technology only kicks in when a user's client has a complete copy of the file and is uploading it to other users, and not while downloading.

Comcast spokesman Charlie Douglas would not comment directly on the matter, instead only saying, "Comcast does not block access to any applications, including BitTorrent."

There are currently very few regulations regarding traffic shaping, and none that specifically cover Comcast's particular use. The FCC says that while consumers are entitled to run the applications and services of their choice, they are subject to measures of "reasonable network management" by their ISPs. The closest directive governing Comcast's behavior - which still doesn't directly apply - would be found in AT&T's conditions for acquiring BellSouth, where it had to agree not to manipulate traffic in any way based on its origin - not service type.

Comcast's "traffic discrimination" has important ramifications for the growing number of services that are leveraging P2P as a means to distribute large files quickly and cheaply. A company like Blizzard Entertainment, who relies on BitTorrent for distributing World of Warcraft updates that often measure hundreds of megabytes in size, may have trouble reaching its players if it or they are behind a Comcast internet connection. This problem will only worsen if other ISPs decide on a similar course of action.

Ashwin Navin, co-founder and president of BitTorrent Inc. confirmed the AP's findings, and noted that he has seen similar practices from several Canadian ISPs.

"They're using sophisticated technology to degrade service, which probably costs them a lot of money. It would be better to see them use that money to improve service,

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