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Is uTorrent disrupting the Net?

Richard Bennett reports that one of the leading BitTorrent clients, uTorrent, has decided to use UDP rather than TCP as the protocol for moving torrents through the Net. Especially since uTorrent is owned by BitTorrent, Inc., and thus is the paradigmatic BitTorrent client, this has stirred up a lively debate about whether this is a good thing for the Net, and whether it is proof that Net neutrality is counterproductive, necessary, or irrelevant.

I am in way over my head here, so please correct me if I get this wrong, but as I understand it, UDP is generally used for data that is time-sensitive and that isn’t rendered useless by some data loss, such as VoIP and online gaming. Unlike TCP, UDP doesn’t have a self-governing mechanism that manages traffic when it gets crowded; UDP lets a server just keep sending bits regardless of the current state of the network. uTorrent (which had previously been using UDP only for lightweight metadata) has started using UDP for the data itself — the files that people are torrenting — to get around the TCP throttling mechanisms some of the ISPs use, raising the fear that all that UDP data will congest the tubes.

Richard Bennett says this shows that Net neutrality will choke the Net. uTorrent talks about it here. I found a forum at BroadbandReports that provided multiple and useful perspectives.

As for me, I don’t know what to think. I am open for instruction.

Later that day: BitTorrent replies that Richard’s article is “utter nonsense.” Explained here. Slashdotted here. BitTorrent says that they’re implementing controls in their client software that will notice congestion and throttle back. Again, I’m in no position to judge.

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7 Responses to “Is uTorrent disrupting the Net?”

  1. hello david long time no talk. hope all is well. off to china. say hello if you wish.


  2. So here’s the deal. UDP is for when you can lose data. Period. It actually has a lower theoretical throughput than a properly-configured TCP connection because each UDP packet must carry address information that TCP takes care of at connection setup time. It is probably easiest to think of UDP as sending emails, where TCP is like IM.

    Having said all that, there are several reasons why UDP could make sense for a BitTorent client at this time.

    1) BT packets are not dependent on order and losses don’t matter – this is *exactly* the kind of service UDP was designed for

    2) TCP and UDP get treated differently by naively-configured (read home user) routers and firewalls

    3) Backbone routers may provide different quality of service to UDP than for TCP

    Both of the last two reasons qualify as “gaming the system” – BT is trying to adapt it’s protocol use to the current practices of the internet to provide people with good download performance. Internet routing practices will change as a result of this, and there will be another round. Net Neutrality (or the absence of it) is another aspect of this game, as is the public mud-slinging. The only real answer is to charge end-users on a data-volumetric basis, but given that there is so much dark fiber in the US (two years ago I was informed by a telecoms regulator that only about 15% of the current fiber capacity was in use) that would seem rather like a major money grab at this point.

    What BitTorrent *really* disrupts is the content-distribution industry. As long as companies like TimeWarner control the networks that are used to distribute their content, they will always have a conflict of interest in regulating traffic. This is what Net Neutrality is meant to address. A network provider needs to behave solely as a network provider, and not favor one customer’s data stream over another (excepting explicit contractual agreements for specific levels of service).

  3. UDP is generally used by applications who don’t want or need TCP’s retransmission strategy. These tend to be real-time applications like VoIP, but don’t have to be. Sun invented a file access protocol called nfs back in the 80s that used UDP, but that’s the only large-scale use of UDP on record for moving files.

    The folks at BT, Inc, seem to be most upset at my suggestion that they’re changing their defaults because of the Canada situation, but that wasn’t my original observation.

    They’ve implemented their own backoff over UDP because they’ve found that TCP backoff doesn’t do much good for BT, which is something I’ve been saying for a long time without BT commenting one way or another.

  4. […] Slyck, DSLreports, TorrentFreak, Ars Technica, Icrontic, Joho the Blog and TMCnet, GigaOM, Industry Standard, […]

  5. […] Is uTorrent disrupting the Net? […]

  6. You might enjoy my follow-up:

    A lot of questions remain about the soundness of the BitTorrent approach.


  7. […] Is uTorrent disrupting the Net? ( […]

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