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

[Luca Muscariello]

A buffer in a router is sized once. RTT varies.
So BDP varies. That’s as simple as that.
So you just cannot be always at optimum because you don’t know what RTT you
have at any time.

Lola si not solving that. No protocol could BTW.
BTW I don’t see  any formal proof about queue occupancy in the paper.



On Tue 27 Nov 2018 at 12:53, Bless, Roland (TM) <roland.bless at kit.edu>
wrote:

> Hi Luca,
>
> Am 27.11.18 um 12:01 schrieb Luca Muscariello:
> > A BDP is not a large buffer. I'm not unveiling a secret.
>
> That depends on speed and RTT (note that typically there are
> several flows with different RTTs sharing the same buffer).
> The essential point is not how much buffer capacity is available,
> but how much is actually used, because that adds queueing delay.
>
> > And it is just a rule of thumb to have an idea at which working point
> > the protocol is working.
>
> No, one can actually prove that this is the best size for
> loss-based CC with backoff factor of 0.5 (assuming a single flow).
>
> > In practice the protocol is usually working below or above that value.
>
> That depends on the protocol.
>
> > This is where AQM and ECN help also. So most of the time the protocol is
> > working at way
> > below 100% efficiency.
>
> > My point was that FQ_codel helps to get very close to the optimum w/o
> > adding useless queueing and latency.
> > With a single queue that's almost impossible. No, sorry. Just impossible.
>
> No, it's possible. Please read the TCP LoLa paper.
>
> Regards,
>  Roland
>
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