asymetric capacity on windows on Linux everything is fine - Networking

This is a discussion on asymetric capacity on windows on Linux everything is fine - Networking ; Hi, Lately I encounter quite interesting problem on my network. I have 512/512 kbit/s link from my isp and everything seems to be fine when I'm uploading I have something about 512kb/s when I'm testing download I have about 512kbit/s ...

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Thread: asymetric capacity on windows on Linux everything is fine

  1. asymetric capacity on windows on Linux everything is fine

    Hi,

    Lately I encounter quite interesting problem on my network.
    I have 512/512 kbit/s link from my isp and everything seems to be fine
    when I'm uploading I have something about 512kb/s when I'm testing
    download I have about 512kbit/s . This works fine both on Windows XP
    and Gentoo. Problem starts when I'm testing up/down simultaneously then I
    have down ~500 and up ~ 200 kbit/s on widnows and ~500/500 on gentoo.
    I wonder where is the difference between Windows and Linux and if there
    is any chance to solve this problem.

    Thanks in Advance

    Pozdrawiam
    Mroofka

  2. Re: asymetric capacity on windows on Linux everything is fine

    On Mon, 18 Aug 2008 12:28:16 +0000 (UTC), Szymon Turkiewicz wrote:
    > Hi,
    >
    > Lately I encounter quite interesting problem on my network.
    > I have 512/512 kbit/s link from my isp and everything seems to be fine
    > when I'm uploading I have something about 512kb/s when I'm testing
    > download I have about 512kbit/s . This works fine both on Windows XP
    > and Gentoo. Problem starts when I'm testing up/down simultaneously then I
    > have down ~500 and up ~ 200 kbit/s on widnows and ~500/500 on gentoo.
    > I wonder where is the difference between Windows and Linux and if there
    > is any chance to solve this problem.


    Sounds like a driver issue. I'd look for a driver update for Windows.

    --
    * John Oliver http://www.john-oliver.net/ *

  3. Re: asymetric capacity on windows on Linux everything is fine

    Dnia Mon, 18 Aug 2008 17:30:30 +0200, John Oliver napisał(a):

    > On Mon, 18 Aug 2008 12:28:16 +0000 (UTC), Szymon Turkiewicz wrote:
    >> Hi,
    >>
    >> Lately I encounter quite interesting problem on my network. I have
    >> 512/512 kbit/s link from my isp and everything seems to be fine when
    >> I'm uploading I have something about 512kb/s when I'm testing download
    >> I have about 512kbit/s . This works fine both on Windows XP and
    >> Gentoo. Problem starts when I'm testing up/down simultaneously then I
    >> have down ~500 and up ~ 200 kbit/s on widnows and ~500/500 on gentoo. I
    >> wonder where is the difference between Windows and Linux and if there
    >> is any chance to solve this problem.

    >
    > Sounds like a driver issue. I'd look for a driver update for Windows.


    I'm almost sure this is not the problem. I've made tests on few different
    notebooks and on WindowsXP and Windows2000.

    Pozdrawiam
    Szymon Turkiewicz

  4. Re: asymetric capacity on windows on Linux everything is fine

    Szymon Turkiewicz wrote:
    > Dnia Mon, 18 Aug 2008 17:30:30 +0200, John Oliver napisał(a):
    >
    >> On Mon, 18 Aug 2008 12:28:16 +0000 (UTC), Szymon Turkiewicz wrote:
    >>> Hi,
    >>>
    >>> Lately I encounter quite interesting problem on my network. I have
    >>> 512/512 kbit/s link from my isp and everything seems to be fine when
    >>> I'm uploading I have something about 512kb/s when I'm testing download
    >>> I have about 512kbit/s . This works fine both on Windows XP and
    >>> Gentoo. Problem starts when I'm testing up/down simultaneously then I
    >>> have down ~500 and up ~ 200 kbit/s on widnows and ~500/500 on gentoo. I
    >>> wonder where is the difference between Windows and Linux and if there
    >>> is any chance to solve this problem.

    >> Sounds like a driver issue. I'd look for a driver update for Windows.

    >
    > I'm almost sure this is not the problem. I've made tests on few different
    > notebooks and on WindowsXP and Windows2000.
    >


    How are you testing the speed? If you are using tcp connections, then
    for every transferred packet there is an acknowledge packet going in the
    opposite direction. There is also normally other traffic in both
    directions - things like DNS lookups and transfer handshakes. If
    windows is badly prioritising the packets so that all the bandwidth in
    one direction is completely filled with data packets, the other
    direction could quickly be stalled because the small but critical
    handshaking packets are delayed. You can read about this sort of thing
    on webpages about bittorrent clients - they normally recommend that you
    limit download and upload bandwidth to slightly lower than your full
    rate to avoid this sort of stalling.

  5. Re: asymetric capacity on windows on Linux everything is fine

    Szymon Turkiewicz wrote:
    > Hi,
    >
    > Lately I encounter quite interesting problem on my network.
    > I have 512/512 kbit/s link from my isp and everything seems to be fine
    > when I'm uploading I have something about 512kb/s when I'm testing
    > download I have about 512kbit/s . This works fine both on Windows XP
    > and Gentoo. Problem starts when I'm testing up/down simultaneously then I
    > have down ~500 and up ~ 200 kbit/s on widnows and ~500/500 on gentoo.
    > I wonder where is the difference between Windows and Linux and if there
    > is any chance to solve this problem.


    As David already said it's generally bad for tcp when you have bulk
    traffic in both directions as the acks get delayed in the queue.

    The main difference between Linux and XP/2K TCP is that by default Linux
    uses window scaling and XP/2K don't. This means that XP/2K won't ever
    have more than 64k unacked data in transit. There are no doubt other
    differences as well and what exactly is happening for you will depend on
    things like buffer sizes in modem/at ISP, how far away the other end of
    the connection is and what settings that server uses.

    Andy.

  6. Re: [solved] asymetric capacity on windows on Linux everything isfine


    >> Hi,
    >>
    >> Lately I encounter quite interesting problem on my network. I have
    >> 512/512 kbit/s link from my isp and everything seems to be fine when
    >> I'm uploading I have something about 512kb/s when I'm testing download
    >> I have about 512kbit/s . This works fine both on Windows XP and
    >> Gentoo. Problem starts when I'm testing up/down simultaneously then I
    >> have down ~500 and up ~ 200 kbit/s on widnows and ~500/500 on gentoo. I
    >> wonder where is the difference between Windows and Linux and if there
    >> is any chance to solve this problem.

    >
    > As David already said it's generally bad for tcp when you have bulk
    > traffic in both directions as the acks get delayed in the queue.
    >
    > The main difference between Linux and XP/2K TCP is that by default Linux
    > uses window scaling and XP/2K don't. This means that XP/2K won't ever
    > have more than 64k unacked data in transit. There are no doubt other
    > differences as well and what exactly is happening for you will depend on
    > things like buffer sizes in modem/at ISP, how far away the other end of
    > the connection is and what settings that server uses.


    Hi,


    I've found problem. I've upgraded kernel from 2.6.19 to 2.6.23 on router
    and there was a change in IMQ.

    2.6.19
    4: imq0: mtu 1500 qdisc hfsc qlen 30
    2.6.23
    4: imq0: mtu 16000 qdisc hfsc qlen 11000

    after setting mtu and qlen like in 2.6.19 kernel problem disappeared. now
    I have 60/60kB in tests.

    Thanks for your time and advices.

    Now I would like to learn which exactly is qlen and how it could be used
    to tune my routers but this is another topic

    Pozdrawiam
    Mroofka

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