Iperf UDP packet drops


Hi Peter,

> >From: "Paddon, Peter" <ppaddon --at-- cisco.com>
> >To: "'iperf-users --at-- dast.nlanr.net'" <iperf-users --at-- dast.nlanr.net>
> >Subject: Unexpected UDP QOS Test Results with IPERF
> >Date: Thu, 5 Feb 2004 16:17:24 +1100
> >
> >Hi Folks
> >
> >
> >I am helping a customer of mine who is using IPERF do so QoS testing but we
> >are getting strange results.
> >
> >They are running QoS on 2 Cisco 7206 routers linked via a GE links over a
> >IMPLS carrier.  We are rate limiting these links to 10Mbps.
> >
> >They are using IPERF to generate a single UDP stream of test effort traffic
> >at between 2M and 8Mbps across the network but they are dropping packets way
> >before they reach line rate (as low as 2.5Mbps),  they are dropping about
> >12% of packets at 8Mbps.

What platform are they running the Iperf tests from, and do you know which 
version of the code they are using?

> >
> >They start dropping packets at different levels depending on the payload
> >size of there UDP stream.
> >Packet Size 1470 -- Start Dropping at approx 2.6Mbps
> >Packet Size 1000 -- Start Dropping at approx 5Mbps
> >Packet Size 100 -- Start Dropping at approx above 10Mbps
> >
> >Yet when we run the same tests with a IXIA test tool we drop no packets at
> >any payload size or speed to near line rate,  also when we run the same
> >tests with IPERF in a there lab we also do not drop any packets.
> >
> >Any idea why this may be happening?

There are some known "issues" with Iperf running off of Win2K or XP, which 
is why we're asking the above.

-Jim




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