Slow T3

Discussion in 'Cisco' started by tghaas@gmail.com, Mar 17, 2008.

  1. Guest

    We have just put in a point to point T3. I have a Cisco 3845 with an
    NM1-T3 card at each end. If I open an FTP connection from one end to
    the other, I only get about 6Mbit of throughput. It doesn't seem to
    matter which combination of machines I use on either end (i.e. windows
    -> linux, linux->linux, etc.) If I open a bunch of connections from
    several machines I can max out the connection at about 45Mbit, thereby
    I don't believe it is being limited by my provider.

    Ping times between sites average around 16ms. I am showing no errors
    on any of the interfaces.

    What are my next steps in troubleshooting this?

    Thanks.
    Travis
     
    , Mar 17, 2008
    #1
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  2. wrote:
    > We have just put in a point to point T3. I have a Cisco 3845 with an
    > NM1-T3 card at each end. If I open an FTP connection from one end to
    > the other, I only get about 6Mbit of throughput. It doesn't seem to
    > matter which combination of machines I use on either end (i.e. windows
    > -> linux, linux->linux, etc.) If I open a bunch of connections from
    > several machines I can max out the connection at about 45Mbit, thereby
    > I don't believe it is being limited by my provider.
    >
    > Ping times between sites average around 16ms. I am showing no errors
    > on any of the interfaces.
    >
    > What are my next steps in troubleshooting this?


    I'd use Iperf and get packet traces. If Iperf will get 45Mbps with
    single TCP connection you can rule out T3 and concentrate on end hosts.
    If not - packet traces can shed some light on why performance is poor.

    Regards,
    Andrey.
     
    Andrey Tarasov, Mar 17, 2008
    #2
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  3. John Agosta Guest

    "Andrey Tarasov" <> wrote in message
    news:frmhhc$2me$...
    > wrote:
    >> We have just put in a point to point T3. I have a Cisco 3845 with an
    >> NM1-T3 card at each end. If I open an FTP connection from one end to
    >> the other, I only get about 6Mbit of throughput. It doesn't seem to
    >> matter which combination of machines I use on either end (i.e. windows
    >> -> linux, linux->linux, etc.) If I open a bunch of connections from
    >> several machines I can max out the connection at about 45Mbit, thereby
    >> I don't believe it is being limited by my provider.
    >>
    >> Ping times between sites average around 16ms. I am showing no errors
    >> on any of the interfaces.
    >>
    >> What are my next steps in troubleshooting this?

    >
    > I'd use Iperf and get packet traces. If Iperf will get 45Mbps with single
    > TCP connection you can rule out T3 and concentrate on end hosts. If not -
    > packet traces can shed some light on why performance is poor.
    >
    > Regards,
    > Andrey.



    Look into / Google tcp "big windows."
    Some hosts can't fill up a T3 with default tcp settings.

    -ja
     
    John Agosta, Mar 17, 2008
    #3
  4. cf_0x2102 Guest

    On 2008-03-17, John Agosta <> wrote:
    >
    > "Andrey Tarasov" <> wrote in message
    > news:frmhhc$2me$...
    >> wrote:
    >>> We have just put in a point to point T3. I have a Cisco 3845 with an
    >>> NM1-T3 card at each end. If I open an FTP connection from one end to
    >>> the other, I only get about 6Mbit of throughput. It doesn't seem to
    >>> matter which combination of machines I use on either end (i.e. windows
    >>> -> linux, linux->linux, etc.) If I open a bunch of connections from
    >>> several machines I can max out the connection at about 45Mbit, thereby
    >>> I don't believe it is being limited by my provider.
    >>>
    >>> Ping times between sites average around 16ms. I am showing no errors
    >>> on any of the interfaces.


    Bandwidth Delay Product

    Short answer "Takes too much time to ACK data, therefore we dont 'fill up the
    pipe' with data in transit. By changing windowing values, you can send more
    un-ACKed data, therefore getting closer to the actual bandwidth with a single
    TCP stream."

    http://en.wikipedia.org/wiki/Bandwidth-delay_product

    Try some of this guide for your OS on each end (ftp client and server) if
    possible and report your results.

    http://www.psc.edu/networking/projects/tcptune/
     
    cf_0x2102, Mar 17, 2008
    #4
  5. Guest

    On Mar 17, 6:32 pm, cf_0x2102 <> wrote:
    > On 2008-03-17, John Agosta <> wrote:
    >
    >
    >
    > > "Andrey Tarasov" <> wrote in message
    > >news:frmhhc$2me$...
    > >> wrote:
    > >>> We have just put in a point to point T3. I have a Cisco 3845 with an
    > >>> NM1-T3 card at each end. If I open an FTP connection from one end to
    > >>> the other, I only get about 6Mbit of throughput. It doesn't seem to
    > >>> matter which combination of machines I use on either end (i.e. windows
    > >>> -> linux, linux->linux, etc.) If I open a bunch of connections from
    > >>> several machines I can max out the connection at about 45Mbit, thereby
    > >>> I don't believe it is being limited by my provider.

    >
    > >>> Ping times between sites average around 16ms. I am showing no errors
    > >>> on any of the interfaces.

    >
    > Bandwidth Delay Product
    >
    > Short answer "Takes too much time to ACK data, therefore we dont 'fill up the
    > pipe' with data in transit. By changing windowing values, you can send more
    > un-ACKed data, therefore getting closer to the actual bandwidth with a single
    > TCP stream."
    >
    > http://en.wikipedia.org/wiki/Bandwidth-delay_product
    >
    > Try some of this guide for your OS on each end (ftp client and server) if
    > possible and report your results.
    >
    > http://www.psc.edu/networking/projects/tcptune/


    Thanks for everyone's help. I now have this sorted out and am able to
    get about 30Mbit, I'll work some more on tweaking this to try to
    squeeze a bit more performance.

    It was the registry settings in windows that fixed this issue.

    Thanks again.
    Travis
     
    , Mar 18, 2008
    #5
  6. Sam Wilson Guest

    In article
    <>,
    "" <> wrote:

    > Thanks for everyone's help. I now have this sorted out and am able to
    > get about 30Mbit, I'll work some more on tweaking this to try to
    > squeeze a bit more performance.
    >
    > It was the registry settings in windows that fixed this issue.


    Here's another good source of info:

    <http://www-didc.lbl.gov/TCP-tuning/>

    Sam
     
    Sam Wilson, Mar 18, 2008
    #6
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