Re: [Bloat] when does the CoDel part of fq_codel help in the real world?

[Dave Taht <dave@taht.net>]

"Bless, Roland (TM)" <roland.bless@kit.edu> writes:

> Hi Luca,
>
> Am 28.11.18 um 11:48 schrieb Luca Muscariello:
>
>> And for BBR, I would say that one thing is the design principles another
>> is the implementations
>> and we better distinguish between them. The key design principles are
>> all valid.
>
> While the goal is certainly right to operate around the optimal point
> where the buffer is nearly empty, BBR's model is only valid from either
> the viewpoint of the bottleneck or that of a single sender.

I think I agree with this, from my own experimental data.

>
> In BBR, one of the key design principle is to observe the
> achieved delivery rate. One assumption in BBRv1 is that if the delivery
> rate can still be increased, then the bottleneck isn't saturated. This
> doesn't necessarily hold if you have multiple BBR flows present at the
> bottleneck.
> Every BBR flow can (nearly always) increase its delivery rate while
> probing: it will simply decrease other flows' shares. This is not
> an _implementation_ issue of BBRv1 and has been explained in section III
> of our BBR evaluation paper.

Haven't re-read it yet.

>
> This section shows also that BBRv1 will (by concept) increase its amount
> of inflight data to the maximum of 2 * estimated_BDP if multiple flows
> are present. A BBR sender could also use packet loss or RTT increase as

Carnage!

> indicators that it is probably operating right from the optimal
> point, but this is not done in BBRv1.
> BBRv2 will be thus an improvement over BBRv1 in several ways.

I really really really want a sane response to ecn in bbr.

>
> Regards,
>  Roland
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