TCP Vegas?

Discussion in 'Tomato Firmware' started by az2008, Oct 18, 2008.

  1. az2008

    az2008 Addicted to LI Member

    I've been reading a lot of good things about TCP Vegas. From what I gather it is a congestion reduction algorithm built into the Linux kernal, and enabled by setting some values in proclib (or something?).

    Is this available on Tomato? Are there any plans to make it available?

    Most of the DD-WRT people are raving about it.

    From what I've gathered, the problem with QoS is that you have to specify your max bandwidth. You have to be conservative because if you overstate it, QoS will overflow the WAN's capacity, resulting in worse performance than if you weren't using QoS. But, the more conservative you are, the more bandwidth you don't use. I.e., QoS isn't dynamic.

    TCP Vegas, on the other hand, dynamically adjusts priority of all traffic.

    It seems like the best of both worlds would be to use TCP Vegas for its dynamic pacing of all traffic. And, use QoS (without any limits) to give priority to certain things. I.e., if Tomato allowed the outbound bandwith to be set to 0, and this caused Tomato to only give priority based upon the classification rules (without capping any traffic to a maximum bandwidth), TCP Vegas would handle prioritizing the entire traffic.

    Maybe I misunderstood it. But, it sounds like that's how DD-WRT works. You can set the QoS bandwidth to 0, and then it won't cap anything. It just applies priority. Some people seem to say TCP Vegas is better than QoS. Others seem to say that using DD-WRT's ability to prioritize unlimited (0) bandwidth *and* TCP Vegas is better.

    Does anyone know anything about this?

  2. Maggard

    Maggard LI Guru Member

    See that box above this thread? The one with a Google logo at the front? Try typing "Vegas" into, checking the "" radio button, and taking a look at the results.

    Just a tip. :biggrin:
  3. az2008

    az2008 Addicted to LI Member

    I did that before posting and saw a very long thread where TCP Vegas was mentioned a few times. It seemed to be related to victech's mods. It wasn't conclusive. If I missed something, I'd appreciate a summary.

    I'm just wondering if there are any plans to 1) include TCP Vegas in Tomato. And, 2) change Tomato's QoS to allow "0" for bandwidth so Tomato will prioritize traffic but not cap it.

    BTW: Is there an official Tomato user forum?

  4. humba

    humba Network Guru Member

    There's no need for google.. the forum's built-in search engine is more than good enough for a simple query like that. If you do search for vegas, you come across just a handful of threads, but they do explain why Vegas isn't possible: It's part of the 2.6 kernel whereas Tomato uses the 2.4 kernel. Yeah I know it has been backported to 4.1.27 but tomato uses 4.1.20 (the same Kernel the kernel the official Linksys firmware uses).. so essentially you'd need a kernel developer for a backport and that's a whole different kind of bag than releasing a Tomato mod (many of them just consist of a rebuild of the official sources with some additional software added.. while that does still takes quite a bit of know-how, it's different from actually changing the source code of the kernel).

    And this is the official Tomato forum.
  5. az2008

    az2008 Addicted to LI Member

    Do you know if there are any plans to add TCP Vegas (move Tomato's kernal up just a little)?

    I agree with the argument that Tomato isn't one of the other firmwares, and shouldn't strive to be one. I chose Tomato because it's simple (easy to use). But, I think there's something to be said about keeping up with kernal improvements that improve the underlying system's performance. I don't think that means Tomato is adding features and becoming something different.

  6. humba

    humba Network Guru Member

    Ask Jon (the author) if he intends to change the kernel (email address is in the readme).. but I suspect the response is no - Tomato has used the old Linksys kernel for all this time.
  7. az2008

    az2008 Addicted to LI Member

    Thanks. But, I just downloaded 1.21 again. I couldn't find an email address in the readme.htm file. Did I do something wrong?

  8. basmic

    basmic LI Guru Member

    Tomato FAQ: How do I send a suggestion?
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