[Bloat] geoff huston's take on BBR

[Dave Taht]

On Mon, Jun 11, 2018 at 10:58 PM, Kevin Darbyshire-Bryant
<kevin at darbyshire-bryant.me.uk> wrote:
>
>
>> On 11 Jun 2018, at 22:27, Dave Taht <dave.taht at gmail.com> wrote:
>>
>> https://ripe76.ripe.net/presentations/10-2018-05-15-bbr.pdf
>
> Fascinating!
>
> "       • BBR changes all those assumptions, and could potentially push many networks into sustained instability
>
>         • –  We cannot use the conventional network control mechanisms to regulate BBR flows
>
> • Selective packet drop just won’t create back pressure on the flow”
>
> And I keep on seeing questions on whether BBR understands ECN - if not…. well I think we see the results.

I think geoff goofed in his testing of BBR, starting all flows at the
same time, thus syncing up their probing periods. Real traffic is not
correlated this way.
(I made the same mistake on my initial bbr testing)

I do agree that bbr treats aqm drops as "noise", not backpressure. And
bbr scares me.

I look forward very much to bbr one day soon doing some sort of sane,
conservative, response to ecn marks.

PS having fq on the link makes cubic and bbr cohabitate just fine.
fq_codel vs bbr behavior was reasonable, though bbr lost a lot more
packets before finding a decent state.
> Cheers,
>
> Kevin D-B
>
> 012C ACB2 28C6 C53E 9775  9123 B3A2 389B 9DE2 334A
>



-- 

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