[Bloat] Some updates on hacking on AQMS

Eric Dumazet eric.dumazet at gmail.com
Fri Jun 24 01:01:00 EDT 2011

Le jeudi 23 juin 2011 à 17:10 -0600, Dave Taht a écrit :
> On Thu, Jun 23, 2011 at 4:45 PM, Juliusz Chroboczek <jch at pps.jussieu.fr> wrote:
> >> It really seems that ECN support could be added generically for all
> >> qdiscs that currently do packet drop. Creating a generic mark_or_drop
> >> function is easy.
> >
> > As hinted in a previous message -- please don't.  Every qdisc must be
> > examined individually to check if it is suitable for ECN.
> >
> > Consider also the following.  If the administrator specifies a maximum
> > rate of 100 Mbit/s, he probably doesn't expect the outgoing traffic to
> > exceed that rate under any circumstances.  If you start marking instead
> > of dropping, you must make sure that the resulting traffic is still
> > under 100 Mbit/s, including the marked packets.
> In designing this particular concept I made sure that was an option,
> in the mildly recorrected:
> http://www.bufferbloat.net/projects/bloat/wiki/Save_the_Ants
> Try harder to not shoot the ants, but make ecn marking a first class
> option throughout the qdiscs...
> if possible..

I believe it was done.

qdisc implementations are not random, but follow extensive research

Before doing a change like that, you must redo all the experiments and
show the pro/cons ;)

Once qdisc queue is _full_, its too late, you have to drop packets
anyway. And its not because at least one flow is not responsive :
It might be because one thousand flows began their life at the very same
moment :(

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