Slow Traffic One Way

Discussion in 'Cisco' started by Jason Nash, Jan 21, 2004.

  1. Jason Nash

    Jason Nash Guest

    Network Description:

    Pretty simple network. We have a 4006 as our core with several VLANs.
    Off of the 4006 I have a PIX 515 cluster and on the other side of
    those I have a 2600 router. That router connects to another 2600 at a
    colo facility via two frame relay circuits. We don't own any gear
    beyond that far end router. At the colo we have a collection of Win2K
    and Solaris sytems.

    The Problem:

    If I send a file from the colo to the local network..say via FTP or
    SCP...we get 140KB/sec. That's what I should get on those two frames.
    If I send a file from the local network to any system at the colo we
    get 6KB/sec.

    Well, every system *EXCEPT* a single Linux server. This system gets
    140KB/sec both ways. I've tested this from local clients on the same
    network and switch as the Linux system. These clients were: Win2K, Mac
    OSX, WinXP, and Solaris. They all get 6KB/sec. I tried connecting to
    both Solaris and Win2K FTP servers at the colo. Same result.

    We do absolutely no traffic shaping. None on the 4006 and none on the
    2600s. I've opened a ticket with TAC but they don't see any issue with
    the config. The routers are as basic as you can get and the PIX is
    pretty close. I'm running the latest IOS on the routers and 6.33 on
    the PIX cluster.

    If it wasn't for the Linux system working fine I'd say the colo is
    doing some traffic shaping that they don't realize. But why would the
    Linux system work? The other clients do not that are on the same VLAN
    and physical switch.
    Jason Nash, Jan 21, 2004
    #1
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  2. In article <>,
    Jason Nash <> wrote:
    :pretty simple network. We have a 4006 as our core with several VLANs.

    :If I send a file from the colo to the local network..say via FTP or
    :SCP...we get 140KB/sec. That's what I should get on those two frames.
    :If I send a file from the local network to any system at the colo we
    :get 6KB/sec.

    :Well, every system *EXCEPT* a single Linux server. This system gets
    :140KB/sec both ways. I've tested this from local clients on the same
    :network and switch as the Linux system. These clients were: Win2K, Mac
    :OSX, WinXP, and Solaris. They all get 6KB/sec. I tried connecting to
    :both Solaris and Win2K FTP servers at the colo. Same result.

    6 KB/s suggests duplex problems to me (problems at your end).
    It would be rather odd, though, to have duplex problems on that wide a range
    of equipment, unless you are forcing duplex on the 4006 and leaving
    the other systems to autonegotiate -- in that situation, they are
    going to negotiate half duplex, not full.
    --
    IMT made the sky
    Fall.
    Walter Roberson, Jan 22, 2004
    #2
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  3. Jason Nash

    Hansang Bae Guest

    In article <>,
    says...
    > Network Description:
    > Pretty simple network. We have a 4006 as our core with several VLANs.
    > Off of the 4006 I have a PIX 515 cluster and on the other side of
    > those I have a 2600 router. That router connects to another 2600 at a
    > colo facility via two frame relay circuits. We don't own any gear
    > beyond that far end router. At the colo we have a collection of Win2K
    > and Solaris sytems.
    >
    > The Problem:
    >
    > If I send a file from the colo to the local network..say via FTP or
    > SCP...we get 140KB/sec. That's what I should get on those two frames.
    > If I send a file from the local network to any system at the colo we
    > get 6KB/sec.


    If you have a difference in transfer speed tied to the direction, that
    suggests 1) Someone tuned the TCP stack incorrectly (win/mss etc.) 2)
    There's a duplex mismatch (the acks make it through the the file itself
    does not) or 3) you have a long fat network problem. But since you have
    a low speed FR network, I guess we can rule #3 out.

    >
    > Well, every system *EXCEPT* a single Linux server. This system gets
    > 140KB/sec both ways. I've tested this from local clients on the same
    > network and switch as the Linux system. These clients were: Win2K, Mac
    > OSX, WinXP, and Solaris. They all get 6KB/sec. I tried connecting to
    > both Solaris and Win2K FTP servers at the colo. Same result.


    So within the same switch, you get crappy xfer rate one way? Are the
    switch ports clean? Have you tuned the Linux before (SACK options etc)?


    --

    hsb

    "Somehow I imagined this experience would be more rewarding" Calvin
    *************** USE ROT13 TO SEE MY EMAIL ADDRESS ****************
    ********************************************************************
    Due to the volume of email that I receive, I may not not be able to
    reply to emails sent to my account. Please post a followup instead.
    ********************************************************************
    Hansang Bae, Jan 22, 2004
    #3
  4. Jason Nash

    go go google Guest

    Hansang Bae <> wrote in message news:<>...
    Well, every system *EXCEPT* a single Linux server. This system gets
    > > 140KB/sec both ways.

    Replace the linux server with another one which get 6 KB
    I mean connected in same node same cable the linux is connecting now
    and test the speed if you still get 6 KB
    its problem in client end not the network backbone
    also move the linux server in one node that you 6 kb and see how much you will get
    go go google, Jan 22, 2004
    #4
  5. Jason Nash

    Jason Nash Guest

    Inside the network everything is fine. I can do 10MB/sec with no
    problems. It's only when crossing the frame circuits we see the
    problem.

    Today I worked on tweaking the Windows TCP stack. I'm not getting
    80KB/sec but I can't do any better. The Linux system is a standard
    RedHat 7.3 box with no tweaking. It gets 140KB/sec. I used the
    diagnostic at:

    telnet syntest.psc.edu 7960

    To compare the stacks. The Linux stack is more un-tuned than the
    stock Windows or OSX stacks but still outperforms when testing. I
    can't get OSX to tune at all. Even with matching parameters to
    Windows it's still very, very slow.

    Jason


    Hansang Bae <> wrote in message news:<>...
    > If you have a difference in transfer speed tied to the direction, that
    > suggests 1) Someone tuned the TCP stack incorrectly (win/mss etc.) 2)
    > There's a duplex mismatch (the acks make it through the the file itself
    > does not) or 3) you have a long fat network problem. But since you have
    > a low speed FR network, I guess we can rule #3 out.
    >
    > >
    > > Well, every system *EXCEPT* a single Linux server. This system gets
    > > 140KB/sec both ways. I've tested this from local clients on the same
    > > network and switch as the Linux system. These clients were: Win2K, Mac
    > > OSX, WinXP, and Solaris. They all get 6KB/sec. I tried connecting to
    > > both Solaris and Win2K FTP servers at the colo. Same result.

    >
    > So within the same switch, you get crappy xfer rate one way? Are the
    > switch ports clean? Have you tuned the Linux before (SACK options etc)?
    >
    >
    > --
    >
    > hsb
    >
    > "Somehow I imagined this experience would be more rewarding" Calvin
    > *************** USE ROT13 TO SEE MY EMAIL ADDRESS ****************
    > ********************************************************************
    > Due to the volume of email that I receive, I may not not be able to
    > reply to emails sent to my account. Please post a followup instead.
    > ********************************************************************
    Jason Nash, Jan 22, 2004
    #5
  6. Jason Nash

    Jason Nash Guest

    That should have been "I'm now getting 80KB/sec...".
    Jason Nash, Jan 22, 2004
    #6
  7. In article <>,
    Jason Nash <> wrote:
    :Today I worked on tweaking the Windows TCP stack. I'm not getting
    :80KB/sec but I can't do any better. The Linux system is a standard
    :RedHat 7.3 box with no tweaking. It gets 140KB/sec.

    What's your latency like going across that frame circuit?

    If I correctly recall something I read in passing, then Linux defaults
    to using the extensions that increase the TCP Window size, but those
    extensions have to be specifically turned on in Windows. If your
    latency is more than 20 ms round trip, you might be hitting TCP Window
    size limitations, or receive buffer size limitations.
    --
    Rump-Titty-Titty-Tum-TAH-Tee -- Fritz Lieber
    Walter Roberson, Jan 22, 2004
    #7
  8. Jason Nash

    Jason Nash Guest

    The latency is about 40ms. I tuned and tuned a Windows system today
    and got it up to 80KB/sec. I raised the Window size up a lot until I
    got no more gain and also enabled some other features. The Windows XP
    TCP stack is pretty good stock, but this helped a lot. I still can't
    match the Linux box at 140KB/sec, even when I set the WinXP stack up
    exactly the same way.

    I'm wondering if tweaking these stacks is helping to cover the symptom
    but not solve the problem. I have a point to point T1 going in to the
    same colo tomorrow. I expect that to have less latency than the
    frames and I'll test from there. Thanks for the help!

    Jason

    -cnrc.gc.ca (Walter Roberson) wrote in message news:<bupfum$2fn$>...

    >
    > What's your latency like going across that frame circuit?
    >
    > If I correctly recall something I read in passing, then Linux defaults
    > to using the extensions that increase the TCP Window size, but those
    > extensions have to be specifically turned on in Windows. If your
    > latency is more than 20 ms round trip, you might be hitting TCP Window
    > size limitations, or receive buffer size limitations.
    Jason Nash, Jan 23, 2004
    #8
  9. Jason Nash

    Hansang Bae Guest

    In article <>,
    says...
    > The latency is about 40ms. I tuned and tuned a Windows system today
    > and got it up to 80KB/sec. I raised the Window size up a lot until I
    > got no more gain and also enabled some other features. The Windows XP
    > TCP stack is pretty good stock, but this helped a lot. I still can't
    > match the Linux box at 140KB/sec, even when I set the WinXP stack up
    > exactly the same way.
    >
    > I'm wondering if tweaking these stacks is helping to cover the symptom
    > but not solve the problem. I have a point to point T1 going in to the
    > same colo tomorrow. I expect that to have less latency than the
    > frames and I'll test from there. Thanks for the help!


    Could it be that your FR is a bit dirty and Linux box has SACK enabled?
    Also, when testing FR (or any WAN) ckts, use ping with the following:

    1472 packet size and the following four patterns.

    0x0000
    0x4040
    0xFFFF
    0x8080

    Since you're copying the same files, the above doesn't apply, but it's a
    good way to test (for other readers).

    Have you ruled out port/cable by moving the Linux box?

    --

    hsb

    "Somehow I imagined this experience would be more rewarding" Calvin
    *************** USE ROT13 TO SEE MY EMAIL ADDRESS ****************
    ********************************************************************
    Due to the volume of email that I receive, I may not not be able to
    reply to emails sent to my account. Please post a followup instead.
    ********************************************************************
    Hansang Bae, Jan 23, 2004
    #9
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