I am not tweaking anything.  I need to run in UDP because I am trying to
track packet loss due to collisions.  This brings me to my next question: is
it possible (and can anyone verify that) the link-layer is ack'ing packets,
and therefore resending some.  I know this is in the 802.11 spec.

Randy

On Tue, Apr 27, 2010 at 3:34 PM, Jon Dugan <[email protected]> wrote:

> Excerpts from Randy Buck's message of Tue Apr 27 15:31:58 -0500 2010:
> > I've peaked at around 17 Mbps.
>
> Interesting.  Are you manually tweaking the TCP buffers or letting the
> autotuning stuff do it's magic?  The buffering TCP does might smooth things
> out a bit over the UDP case.
>
> I'm fairly sure the UDP send buffers are fairly small by default on most
> systems.  I'm betting that the UDP send() in Iperf is blocking due to a
> lack
> of buffer space in the kernel which in turn is caused by the inability to
> get
> enough time on the radio.  The UDP sends in Iperf are very bursty and the
> burstyness might aggrevate the problem.
>
> Jon
> --
> Jon M. Dugan <[email protected]>
> ESnet Network Engineering Group
> Lawrence Berkeley National Laboratory
>
>
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