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

From: Mike Hunter (mhunter_at_ack.Berkeley.EDU)
Date: 01/31/04

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    Date: Fri, 30 Jan 2004 15:43:40 -0800
To: Eli Dart <dart@nersc.gov>

    On Jan 30, "Eli Dart" wrote:

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

    > > 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.

    % netstat -inbd bge0
    Name Mtu Network Address Ipkts Ierrs Ibytes Opkts Oerrs Obytes Coll Drop
    bge0 1500 <Link#2> 00:30:1b:b1:08:b6 1321030 0 153151700 1971658 0 2929764081 0 0
    bge0 1500 fe80:2::230:1 fe80:2::230:1bff: 0 - 0 3 - 216 - -
    bge0 1500 169.229.254.1 169.229.254.140 1320970 - 134650330 1971653 - 2902160837 - -
    [snip]

    > 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)....

    I'll give that a shot...thanks. Although my flood pings should have served the
    same purpose (given that I fixed the icmplimit problem), right?

    Thanks,

    Mike
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