Re: [Starlink] plotting all the data

[Matt Mathis <mattmathis@google.com>]

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Some time recently I read a casual paper (on Medium I think) that made the
point that deep diving into outliers and understanding them has led to a
half dozen Nobel prizes, because they lead to discoveries of phenomena that
nobody else had even noticed.  See for instinance the Holmdel Horn
https://en.wikipedia.org/wiki/Holmdel_Horn_Antenna

To keep sane, I tend to keep outliers and clip them as last as possible,
e.g. by choice of graph axis.  This way I have the opportunity to notice
otherwise hidden patterns.

In mlab data we sometimes see outliers that suggest "out of bounds" data
rates.  e.g. a repeated test that clearly has a max rate of 50 Mb/s or
something, and then every so often a one test at 200 Mb/s or higher.   My
assumption is that these are from software managed shapers that
occasionally fail to properly load their configurations.      (I admit to
not having looked hard enough to prove this hypnosis).

Thanks,
--MM--
The best way to predict the future is to create it.  - Alan Kay

We must not tolerate intolerance;
       however our response must be carefully measured:
            too strong would be hypocritical and risks spiraling out of
control;
            too weak risks being mistaken for tacit approval.


On Thu, Jun 17, 2021 at 7:25 AM Nick Buraglio <buraglio@forwardingplane.net>
wrote:

> This is much more common in the high performance computing and networking
> space (i.e. perfsonar, TWAMP, and OWAMP). I have also been pushing "gather
> and store all the data" for ....since I was an engineer working on the
> Teragrid (which is where I first saw Matt's MTU talk around 2002 or 03,
> BTW).  =)
> High fidelity plots of everything that can be gathered is laborious to
> curate but is invaluable for so many reasons. Now we just need a way to
> make it happen everywhere for everyone in a way that's easy.
>
> nb
>
>
> On Thu, Jun 17, 2021 at 8:57 AM Dave Taht <davet@teklibre.net> wrote:
>
>> Capturing and plotting *all* the data is often revealing.
>>
>> Sometimes plotting the data you are discarding (for what seems like sane
>> reasons) is quite revealing.  Saw this on slashdot this morning, it’s
>> good...
>>
>>
>> https://www.newyorker.com/magazine/2021/06/21/when-graphs-are-a-matter-of-life-and-death
>>
>> In the bufferbloat effort I’ve fought time and time again for folk to
>> stop throwing out data above the 95 percentile, and at the very least plot
>> everything they threw out to find patterns...
>>
>> dslreports’ graphing tools, for example, throws out a ton of “outliers" …
>> and the only reason why there is no data past 4 sec here, is that the test
>> doesn’t run long enough.
>>
>> http://www.dslreports.com/speedtest/results/bufferbloat?up=1
>>
>> (been trying to get ahold of someone over there to buy their raw data for
>> years now. They have the biggest - 8 years worth - collection)
>>
>> mlabs has a similar data reduction issue that they haven’t got around to
>> fixing.
>>
>> And more recently we encountered a smoothing problem in wireshark that
>> made a halt in packet processing look more like a normal tcp cwnd cut….
>>
>> _______________________________________________
>> Starlink mailing list
>> Starlink@lists.bufferbloat.net
>> https://lists.bufferbloat.net/listinfo/starlink
>>
>

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