Re: Stream BW support in Iperf
And the side note here is that tuned hosts on links without packet loss
actually can run iperf single streams at high bandwidths. It is rather
easy to max out a PCI-X bus with a single stream on 10GbE for example.
(Packet loss of as little as 1 in 100Million with high RTT has
significant effect on TCP throughput.)
Paul Hyder
NOAA Earth System Research Laboratory, Global Systems Division
Boulder, CO
Ian McDonald wrote:
>> Does anyone know why we need multiple streams to max out the available
>> Bandwidth?
>>
>> Why can't a single stream support high bandwidths?
>>
> Because TCP can't use all the available bandwidth due to congestion
> control. There have been many attempts to improve TCP but the thing is
> that loss comes in many forms, and RTT has a big impact on algorithms
> too.
>
> Try googling for TCP congestion control. You can also see the effects
> by taking iperf on linux and changing the congestion control and use
> netem or dummynet to do some traffic shaping. If you go to my website
> you can even download versions which allow you to do this without
> altering sysctls.
>
> Ian