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

[Dave Taht <dave.taht@gmail.com>]

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Thank you for doing this. I'm now unconvinced the BQL emulation in NS3 is
accurate.

Loved the combined graphs! While it is important to capture that initial
load spike and indeed, draw it out in the paper, being able to see a bit
more detail in steady state would be good. So showing T-0 -> T-3 and T-3
forward would let you use different scales for each.

I'd kind of like to take a step back and try to construct a paper out of
this that could be published at
usenix or acm next year. It's getting towards the holidays but would y'all
(and your advisor(s)) be available to meet via videoconference sometime
next week? I'm in california, jonathon - somewhere in europe - so that
might be hard.




On Sat, Dec 15, 2018 at 11:06 AM Shefali Gupta <shefaligups11@gmail.com>
wrote:

> Hello Jonathan,
>
> Thanks for your feedback.
>
> As suggested, we have produced CoDel and PIE graphs with small NIC buffer
> and uploaded the corresponding graphs.
>
> Link:
> https://github.com/Daipu/COBALT/wiki/Link-Utilization-Graphs-with-Different-NetDeviceQueue-size
>
> We have also uploaded one way end-to-end dela*y* graphs in Light traffic
> scenario for CoDel, COBALT and PIE.
> Link: https://github.com/Daipu/COBALT/wiki/End-To-End-Delay-Graphs
>
> Thanks a lot for your help. We really appreciate it.
>
> Regards,
> Shefali Gupta
> Jendaipou Palme
>
> On Mon, Dec 10, 2018 at 8:45 PM Jonathan Morton <chromatix99@gmail.com>
> wrote:
>
>> > On 10 Dec, 2018, at 2:30 pm, Jendaipou Palmei <
>> jendaipoupalmei@gmail.com> wrote:
>> >
>> > As suggested, we changed the NIC buffer size to 1 packet for the
>> simulation and also tried these different buffer sizes: 10, 50 and 75.
>> >
>> > The default NIC buffer size in ns-3 is 100 packets.
>> >
>> > Additionally, we also enabled BQL and tried.
>> >
>> > We see that the link utilization gets significantly affected when we
>> keep the NIC buffer size small.
>>
>> Yes, that's what I'd expect to see from Reno-type congestion control, and
>> is one good reason why alternatives to Reno were developed (eg. Compound,
>> CUBIC, BBR).  You may wish to explore what happens with Compound and CUBIC,
>> once your basic measurement methodology has matured.
>>
>> I would suggest using BQL, since it's available and represents a
>> realistic deployment.
>>
>> If you were to add TCP (or parallel UDP/ICMP) RTT measurements, you'd see
>> that the peak latency was correspondingly improved by removing the dumb
>> FIFO hidden within the NIC.  I estimate that a 100-packet buffer accounts
>> for about 120ms of latency at 10Mbps, which should definitely be visible on
>> such a graph (being almost 250% of your baseline 50ms latency).
>>
>> Since latency is the main point of adding AQM, I'm a little surprised
>> that you haven't already produced graphs of that sort.  They would have
>> identified this problem much earlier.
>>
>> At present you only have COBALT graphs with the small NIC buffer.  For a
>> fair comparison, Codel and PIE graphs should be (re-)produced with the same
>> conditions.  The older graphs made with the large NIC buffer are
>> potentially misleading, especially with respect to throughput.
>>
>>  - Jonathan Morton
>>
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-- 

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

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