October 25, 2007 | By Peter Eckersley

Comcast Needs to Come Clean

Over the last couple of days, Comcast has been telling the press that they're not interfering with their users' traffic, they're just "delaying" it. Let's examine that proposition for a moment. In our previous posts, we discussed Comcast's forging of TCP RST packets to kill users' connections on BitTottent, Gnutella and Lotus Notes. To see just how disingenuous Comcast is being, consider the following analogy:

Alice is trying to telephone Bob. Alice telephones Bob, and hears someone answer the phone in Bob's voice. They say "I'm sorry Alice, I don't want to talk to you", and hang up. Except, it wasn't actually Bob who answered the phone, it was Comcast using a special device to impersonate Bob's voice. Comcast might describe this as "delaying" Alice and Bob's conversation, on the theory that perhaps they'll keep calling each other until some day when Comcast isn't using their special device. They may also invoke the theory that Alice will call other people who are a lot like Bob, but aren't on Comcast's network, so her conversation will only be delayed.

If "delaying" traffic was Comcast's private intent, they were clearly making absurd and frequently incorrect assumptions about the protocols they were jamming. No doubt that is how they wound up blocking Lotus Notes. (On that subject: after the blog and media attention that followed our post pointing out that situation, Comcast may have finally listened to IBM/Lotus and taken steps to stop jamming Notes. We're happy they've done that, but we have little confidence that smaller companies or free/open source software developers would be able to get Comcast's attention when their protocols are broken by Comcast's packet spoofing.)

Another thing that Comcast has started suggesting to reporters — without giving any details — is that for obscure technical reasons, they can't always prevent network congestion by reducing the amount of bandwidth available to P2P protocols, so when the network is busy, they start jamming them instead. This is an interesting argument, but it's very hard to evaluate or refute it without any details! (A nice rhetorical trick, that.)

For now, let's be very generous to Comcast and assume what we think is false: let's assume that some P2P network or other actually triggers a flaw in the way cable modem networks are designed, so that it's hard for Comcast to keep plenty of the channel free for web surfers when there are enough P2P nodes around. In that case, rather than just spoofing packets and offering incredibly disingenuous denials after they've been caught red-handed, Comcast should come clean. They should explain what they're doing, and explain in precise and detailed terms why they're doing it. If they do that, the technical community will be able to evaluate their arguments properly, decide whether they've got any basis at all, and (we're just guessing here) explain to them how to solve their problem correctly and without arbitrarily jamming things.

That way, Comcast might not break the very thing they claim to be selling access to: the Internet.

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