[Cake] COBALT implementation in ns-3 with results under different traffic scenarios

[Dave Taht]

On Fri, Nov 23, 2018 at 8:05 AM Dave Taht <dave at taht.net> wrote:
>
> Jendaipou Palmei <jendaipoupalmei at gmail.com> writes:
>
> > Hi Dave,
> >
> > We have added the results for CoDel and PIE in the same setup.
> >
> > Link:
> > https://github.com/Daipu/COBALT/wiki/Light-Traffic
>
> Wonderful, thank you. One new thing in cobalt is it responds much
> earlier to stuff in slow start, and thus that first spike is much
> smaller than it is with codel or pie. Network researchers spend way too
> much time looking at stuff in congestion avoidance mode, where what we
> see in the real world is most flows never get out of slow start.
>
> As an example, slashdot.org, last I checked, started 78 flows over 2.2
> seconds for a page load.
>
> I'm still puzzled as to why queue utilization spikes and drops so
> much on all three qdiscs in your simulation. In general we use a much
> larger number of packets in our packet limit (1000 or more) and I am
> thinking tail drop is controlling your queue more than any of the qdiscs
> are at 10mbit with a 50ms delay. I haven't had enough coffee yet this
> morning to do the bdp here, but that's another easy param to tweak.

this was definiately pre-coffee, you are showing next to no queue
utilization in the first place and good throughput on pie and codel.

It was the throughput graph I was mis-interpreting.

This is possibly a correct result in your simulation!! - the periodic
throughput drop you are showing in cobalt at this bandwidth and rtt.
I'm happy to see cobalt kick in early on slow start but not happy to
see the periodic drop. Jon, do you have time for a code review?

It also looks like we can setup a simple real-world duplicate of this
test in flent (5 flows) + netem. However (sigh), our tc sampler for
queue depth is broken on modern versions of iproute2.

Also the aqm work that I'd done on cake was eliminated in the rewrite,
and that I'd not gone at looked hard at longer rtts again, lacking
resources.

> Ns3, btw, also has fq_codel. I happen to be fond of what fq can do. if
> you feel like another run, with the packet limit increased and that
> added too?
>
> Care to try 100mbit? 20ms RTT? 80ms? :)
>
> Can you put your test code up somewhere?
>
>
> >
> > Thanks for your help.
> >
> > On Thu, Nov 22, 2018 at 9:02 PM Dave Taht <dave.taht at gmail.com> wrote:
> >
> >     Your light traffic graph is puzzling, with the synchronized drops.
> >     Is
> >     it possible for you to do another test run, same setup, with codel
> >     or
> >     pie?
> >     On Thu, Nov 22, 2018 at 5:57 AM Jendaipou Palmei
> >     <jendaipoupalmei at gmail.com> wrote:
> >     >
> >     > Hello Jonathan and Dave,
> >     >
> >     > Thanks for your timely inputs.
> >     >
> >     > We have implemented COBALT in ns-3. The main C++ file is here:
> >     >
> >     >
> >     https://github.com/Daipu/COBALT/blob/master/src/traffic-control/model/cobalt-queue-disc.cc
> >
> >     >
> >     > We have also added Queue length and Throughput graphs for COBALT
> >     in our wiki:
> >     >
> >     > https://github.com/Daipu/COBALT/wiki
> >     >
> >     > Thanks and Regards,
> >     > Jendaipou Palmei
> >     > Shefali Gupta
> >     > _______________________________________________
> >     > Cake mailing list
> >     > Cake at lists.bufferbloat.net
> >     > https://lists.bufferbloat.net/listinfo/cake
> >
> >
> >
> >     --
> >
> >     Dave Täht
> >     CTO, TekLibre, LLC
> >     http://www.teklibre.com
> >     Tel: 1-831-205-9740



-- 

Dave Täht
CTO, TekLibre, LLC
http://www.teklibre.com
Tel: 1-831-205-9740