<div id="geary-body"><div>I'm using Fedora 26 and it also seems like the "rate" option prevents reordering. Exactly what I was looking for.</div><div>Thank you very much,</div><div>Thibaut Ehlinger</div></div><div id="geary-quote"><br>On Fri, May 4, 2018 at 9:33 AM, Christoph.Furer@swisscom.com wrote:<br><blockquote type="cite"><div class="plaintext" style="white-space: pre-wrap;">Since I faced the same problems, here my experiences:
I am also in a situation where I need to produce jitter without packet reordering (in my emulated use case reordering is an extremely exceptional case, only happening in network failure conditions).
I'm using Ubuntu on my netem PC.
I had a very old PC (and Linux) before, where it was easy to avoid reordering with pfifo.
I tried two different Ubuntu versions (14 and 16, i.e. two different iproute2 versions, 3.12.0 and 4.3.0).
With Ubuntu 14 I was able to avoid reordering using the "rate" option of netem (when setting any rate option, there is no reordering, it's like a switch for this).
With Ubuntu 16 I was unable to avoid reordering, the "rate" option didn't work any longer.
With this, I have to use Ubuntu 14 for my netem application.
What I'm missing in netem is an option to switch reordering completely off (as it was the rate option in the older version). I'm aware, that without reordering, the jitter distribution will be no longer as expected.
According to my internet search I did, the pfifo doesn't work, because if you use this command, the pfifo queue is in series with the netem queue -> the netem queue will produce reordering, the pfifo queue will not change anything on this. In very old netem versions, this worked differently.
Christoph Furer
-----Ursprüngliche Nachricht-----
Von: <a href="mailto:netem-bounces@lists.linux-foundation.org">netem-bounces@lists.linux-foundation.org</a> [<a href="mailto:netem-bounces@lists.linux-foundation.org">mailto:netem-bounces@lists.linux-foundation.org</a>] Im Auftrag von Stephen Hemminger
Gesendet: Mittwoch, 2. Mai 2018 17:07
An: thibaut ehlinger <<a href="mailto:thibaut.ehlinger@inria.fr">thibaut.ehlinger@inria.fr</a>>
Cc: <a href="mailto:netem@lists.linux-foundation.org">netem@lists.linux-foundation.org</a>
Betreff: Re: [Netem] Emulate jitter without reordering
On Wed, 02 May 2018 09:41:52 +0200
thibaut ehlinger <<a href="mailto:thibaut.ehlinger@inria.fr">thibaut.ehlinger@inria.fr</a>> wrote:
<blockquote> Hello,
I'm a PhD student in computer networking, and I'm currently doing some
experimentation on Youtube under different network conditions.
I use traffic control, and as such, I wanted to know if it was
possible to emulate jitter without packet reordering? I've been
struggling with this problem a lot. On the netem page they say that
you can, by using the two commands given at the end of this mail, but it doesnt' work.
I've checked this several times.
Would you have any clue on how to do this?
Thank you very much,
Thibaut Ehlinger
# tc qdisc add dev eth0 root handle 1: netem delay 10ms 100ms # tc
qdisc add dev eth0 parent 1:1 pfifo limit 1000
</blockquote>
It should cause packets to go out in the range 90 to 110 ms.
What kind of delays do you see (with ping)?
Copying this email to the netem mailing list since others may have seen similar issues.
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</div></blockquote></div>