Re: UDP on FreeBSD



On 3/30/11 2:32 PM, Michael Proto wrote:
On Wed, Mar 30, 2011 at 3:43 PM, Kyungsoo Lee<ulsanrub@xxxxxxxxx> wrote:
Hi All,

I want to check UDP on FreeBSD.

I am using IPERF on FreeBSD for wireless testing with Proxim 8470 FC PCMCIA
card on IBM T42 and T61.

When I'm transmitting data from FreeBSD to FreeBSD or CentOS using Iperf
with -u -b 100M on iperf, they had lost lots of packets. Sniffer near the
two nodes shows the sender could not send all packets. Iperf sender said
that they try to send 85469 packets but they lost 68824 packets. I think
that the UDP buffer on the sender could not handle all packets.

But if I'm trying to send data from CentOS to FreeBSD using Iperf with -u -b
100M option on iperf, the sender tries 18636 packets so they lost few
packets like 1 or 2 packets.As a result, they have similar bandwidth result
on the report. I think that it happens from different implement between
FreeBSD and Linux.

But I want to double check that this is normal for FreeBSD or not. If I have
some missing points, let me know please.

Thank you!
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Just a guess, but have you tried adjusting the net.inet.udp.maxdgram
sysctl? I believe the default is somewhat low for UDP transmit. I
don't know what size packets iperf is using but increasing the
maxdgram value might help your testing.

this is many years out of date but a decade or so ago freebsd would return ENOBUFS
and linux would block when the outgoing queues filled up.
the answer then was that teh programs are all written for Linux and didn't check for ENOBUFS
but that may be out of date now in many different ways.

-Proto
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