Thanks for sending this. Do you have any insights into the reasons for these
differences. We will send you our results as well.
On Sep 2, 2014, at 5:20 PM, Bob (Robert) McMahon <rmcma...@broadcom.com> wrote:
> Ok, I see different values as well. Iperf2 is showing approximately 20 us
> jitter while iperf3 is showing ~150 us. This is using a 200Mbs udp stream on
> 802.11 AC.
>
> Bob
> From: Bob (Robert) McMahon [mailto:rmcma...@broadcom.com]
> Sent: Tuesday, September 02, 2014 1:34 PM
> To: Jon Lederman
> Cc: iperf-users@lists.sourceforge.net
> Subject: Re: [Iperf-users] Difference In Jitter Calculations Between IPerf2
> and IPerf3
>
> Don’t know but comments are ignored by the compiler ;)
>
> Can you share your results? I’d be curious to see the variation and if it
> could be related to things like scheduling.
>
> Also, what os are you using? If you are using linux you may want to set the
> processes to use SCHED_RR
>
> http://www.cyberciti.biz/faq/howto-set-real-time-scheduling-priority-process/
>
> I do that in iperf2
>
> http://sourceforge.net/projects/iperf2/?source=directory
>
> Bob
> From: Jon Lederman [mailto:jonleder...@gmail.com]
> Sent: Tuesday, September 02, 2014 1:29 PM
> To: Bob (Robert) McMahon
> Cc: iperf-users@lists.sourceforge.net
> Subject: Re: [Iperf-users] Difference In Jitter Calculations Between IPerf2
> and IPerf3
>
> Thanks. Look forward to your results. Even though I also noticed that the
> calculation looks similar on the surface, I did notice a comment in iperf3 to
> the effect:
>
> // XXX: This is NOT the way to calculate jitter
> // J = |(R1 - S1) - (R0 - S0)| [/ number of packets, for average]
>
> Any thoughts why that is in there? The calculation in the code appears to
> have come directly out of the RFC 1889/3550.
>
> Also, I want to clarify that this calculation seems to be average jitter not
> instantaneous jitter.
>
> Thanks.
>
> -Jon
> On Sep 2, 2014, at 4:23 PM, Bob (Robert) McMahon <rmcma...@broadcom.com>
> wrote:
>
>
> A quick cursory view of the source suggests the same calculation. Let me run
> both on my test rig and see if I get similar results.
>
> Bob
> -----Original Message-----
> From: Jon Lederman [mailto:jonleder...@gmail.com]
> Sent: Monday, September 01, 2014 5:22 PM
> To: iperf-users@lists.sourceforge.net
> Subject: [Iperf-users] Difference In Jitter Calculations Between IPerf2 and
> IPerf3
>
> Hi,
>
> In measuring jitter using Iperf 2.0.5 and Iperf 3, I have noticed a marked
> difference in the calculations up to an order of magnitude. Could you
> explain the differences in calculation of jitter between 2.0.5 and 3 and the
> accuracy. Which should I rely upon?
>
> Thanks in advance.
>
> Jon
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