Re: Effective bandwidth reduction over WAN

From: Kai Howells (kai.howells_at_icorp.com.au)
Date: 08/02/05

  • Next message: Robert Hajime Lanning: "Re: Effective bandwidth reduction over WAN"
    Date: Tue, 2 Aug 2005 08:06:46 +1000
    To: <e.meijer@verizon.net>
    
    
    

    These people:
    http://www.psc.edu/networking/projects/hpn-ssh/

    have been working on a High Performance Enabled SSH/SCP

     From their page:
    "SCP and the underlying SSH2 protocol implementation in OpenSSH is
    network performance limited by statically defined internal flow
    control buffers. These buffers often end up acting as a bottleneck
    for network throughput of SCP, especially on long and high bandwith
    network links. Modifying the ssh code to allow the buffers to be
    defined at run time eliminates this bottleneck. We have created a
    patch that will remove the bottlenecks in OpenSSH and is fully
    interoperable with other servers and clients. In addition HPN clients
    will be able to download faster from non HPN servers, and HPN servers
    will be able to receive uploads faster from non HPN clients. However,
    the host receiving the data must have a properly tuned TCP/IP stack."

    It may help you out here...

    Cheers,
    Kai

    On 30/07/2005, at 1:40 PM, Eric Meijer wrote:

    > To SSH mailing list:
    >
    >
    >
    >
    >
    > I have a somewhat unusual question. I do not know if this issue is
    > truly a bug or just a feature of the protocol.
    >
    >
    >
    > I have two sites that are distantly connected to each other via a
    > DS3 WAN. When we tried to replace FTP with SCP or SFTP we ran into
    > throughput problems. We then set up a test in our lab to see if we
    > could isolate the factor that was impacting throughput. This test
    > setup was composed of two nodes hooked up through a WAN emulator.
    > They were connected using Gigabit Ethernet, but the rate was
    > throttled back to 45 mbps (DS3 rate). All of the testing used an
    > MTU of 1500 and files sizes of 10 MB, 100Mb, 1 GB, and 5 GB. We
    > ran FTP tests with the same setup for a baseline. For SCP and SFTP
    > we tried each of the three encryption algorithms (3-des, arcfour, &
    > blowfish). We then varied the WAN latency. We are using the
    > latest version of the Portable SSP for Solaris. The OS is Solaris 8.
    >
    >
    >
    > The results were
    >
    >
    >
    > 0 latency FTP Ave. 39.5 mbps SCP Ave. 39.4 mbps
    > SFTP Ave. 38.8 mbps
    >
    > 60 millisec FTP Ave. 37.7 mbps SCP Ave. 2.9 mbps
    > SFTP Ave. 2.9 mbps
    >
    > 100 millisec FTP Ave. 33.0 mbps SCP Ave. 2.0 mbps
    > SFTP Ave. 1.8 mbps
    >
    >
    >
    > Can anyone tell me why the throughput of SCP and SFTP drop so
    > drastically when we try to use SSP protocols over a WAN?
    >
    >
    >
    > Eric Meijer
    >
    >

    
    



  • Next message: Robert Hajime Lanning: "Re: Effective bandwidth reduction over WAN"

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