Re: [Bloat] dash traffic "chunklets" verses pie and fq_codel

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

On Fri, Sep 8, 2017 at 12:32 AM, Steinar H. Gunderson
<sgunderson@bigfoot.com> wrote:
> On Thu, Sep 07, 2017 at 04:52:54PM -0700, Dave Taht wrote:
>> good read:
>>
>> http://caia.swin.edu.au/cv/jkua/preprint/jkua-icccn2017-chunklets-preprint-10may17.pdf
>
> Aaaaa!
>
> “For example, FQ-CoDel isolates individual traffic flows into
> sub-queues then serves each sub-queue with a Deficit Round
> Robin (DRR) scheduler. The result is relatively even capacity
> sharing, which may actually be detrimental to a DASH flow
> (often a single, persistent TCP connection) that is competing
> with multiple other concurrent TCP flows.”
>
> Isn't this just an AQM sabotage scheme?

Well, first, a paper showing vastly better behavior for dash traffic
for fq_codel over pie and tail drop was a reason to celebrate.

Secondly, dash is kind of special in that you *are* constantly probing
for more bandwidth for a replacement stream, and that does interact
with fq in some difficult ways.

I wouldn't go as far as calling using two flows to do a probe like
this "sabotage", but a practical means of finding the right queue and
getting a bit more bandwidth overall. The multipath mosh work (sadly
still not mainlined when last I looked) was resistant to hash
collisions.

It is unclear from the paper to what extent the aqm kicks in - I would
have liked some packet drop figures and their onset.

I keep hoping to see some resumption of bittorrent experiments...

Lastly, I liked the idea of a (in)stability index.

> /* Steinar */
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Dave Täht
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http://www.teklibre.com
Tel: 1-669-226-2619