Re: Assymetric results from iperf across gigabit link (long)

From: Eli Dart (dart_at_nersc.gov)
Date: 01/30/04

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    To: Mike Hunter <mhunter@ack.Berkeley.EDU>
Date: Fri, 30 Jan 2004 14:00:00 -0800

    In reply to Mike Hunter <mhunter@ack.Berkeley.EDU> :

    > On Jan 30, "To freebsd-net@freebsd.org" wrote:
    >
    > > Hi,
    >
    > [snip]
    >
    > I switched the two pieces of hardware, and the photons still prefer going
    > uphill, so maybe there's a problem with the fiber after all. I'd still
    > appreciate any hints on what to ask freebsd to help me figure it out.
    > (Yes, we have real fiber test gear, this is more of an experiment.)

    Have you looked at interface error counts? (netstat -inbd) If you
    have dirty fiber, you could just be missing/corrupting the odd packet
    here and there, which would be enough to impact a high-bandwidth TCP
    flow.

    the other thing to check is if a UDP cannon has the same bandwidth
    asymmetry, since the UDP iperf tests don't have TCP's timidity (if
    memory serves me)....

                    --eli

    >
    > Thanks,
    >
    > Mike
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