Thanks for an interesting discussion.
>From: cisco-nsp [cisco-nsp-boun...@puck.nether.net] on behalf of Saku Ytti
>On 12 August 2017 at 18:21, Raymond Burkholder <r...@oneunified.net> wrote:
>> I have successfully run iperf bidirectionally in tcp as well as udp and hit
>> link limits, even on smaller, lower capacity linux based boxes.
>On what packet sizes? What link speeds? Linux UDP socket performance
>is terrible, even with rescvmmsg sendmmsg which iperf does not
>utilise, the performance is bad. XEON grade server CPU won't congest
>1GE single dir - 1.48Mpps, without loss.
>If you don't care/look at loss, or use low pps, it's different.
>If you use TCP you're measuring the host stacks TCP implementation,
>and you have no visibility on network quality, because packet loss is
>hidden from you.
There is now a version 3 of iperf available. Most noticeable improvement from
this perspective is that in TCP mode it shows the current window size and the
number of re-transmissions at each reporting interval. This makes it much
easier to understand the behaviour of the transfer... You see the
re-transmissions caused by any packet loss in real time, and its immediate
impact on the TCP throughput. I find this very helpful.
The packet loss is no longer hidden like it was with iperf_v2.
iperf3 doesn't interoperate with the old iperf (v2) - you need a version 3 at
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