[Cake] inbound cake or fq_codel shaping fails on cable on netflix reno

[Dave Taht]

cdfs help. I also try to encourage sending the flent.gz files too. :)

Outbound, to 99% or more of the rate, *with perfect framing* looks great so
far, 'cept on crappy cablemodems.

I am concerned about recommending values as high as 98% for inbound
shaping. We are engineering to
the test here (2? 3 flows? on a very short rtt), and need to leave *some*
headroom for multiple flows to enter in slow start and get kicked out of it.

I'll buy that the old 85% figure made sense in the sub 20Mbit era, and that
we only need enough headroom to allow X flows to enter based on the
characteristics of the link and typical traffic - 15 new flows per second *
per active user/10 ? and cake's response to slow start is more agressive...

try a:

flent -H flent-london.bufferbloat.net -s .02 --te=download_streams=32 -t
'98%' tcp_ndown

with htb+fq_codel and cake to see that spike more clearly.


On Tue, Jul 24, 2018 at 7:54 AM Kevin Darbyshire-Bryant <
kevin at darbyshire-bryant.me.uk> wrote:

>
>
> On 24 Jul 2018, at 14:51, Dave Taht <dave.taht at gmail.com> wrote:
>
> Now that you can join the party, I note there IS a flent server in england
> with irtt on it.
>
> flent-london.bufferbloat.net
>
>
> Ok, well if you’re desperately interested….. :-)
>
> Plot I did running to the london server, one shaped at 99% downstream, the
> other at 98%…. and I’ve decided to stick at 98% as a result - plot is a
> little bit hard to distinguish but I’d say there’s around 8ms avg less
> latency-ish between the two.  And an order of magnitude between using
> london v fremont :-)
>
> The upstream barely registers
>
> # tc -s qdisc show dev ifb4eth0
> qdisc cake 801a: root refcnt 2 bandwidth 78400Kbit diffserv3 dual-dsthost
> nat ingress split-gso rtt 100.0ms ptm overhead 26
>
>
>

-- 

Dave Täht
CEO, TekLibre, LLC
http://www.teklibre.com
Tel: 1-669-226-2619
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