[Cake] Upstream submission of dual-mode fairness patch

[Ryan Mounce]

On Mon, 4 Mar 2019 at 13:47, Jonathan Morton <chromatix99 at gmail.com> wrote:
>
> > On 4 Mar, 2019, at 4:55 am, Georgios Amanakis <gamanakis at gmail.com> wrote:
> >
> > …the fairness logic wouldn't account for that "ingress traffic" and would yield fairer results.
>
> Well there we have a quandary, since presently it enforces fairness of *load* on the bottleneck link, but the change would alter that to fairness of *delivered* traffic.  The current setup is arguably more robust against adversarial traffic, don't you think?

And it provides an incentive to use ECN so that congestion signals can
be sent "for free" without dropping packets that have traversed the
bottleneck. I'm firmly in favour of the current setup.

This is analogous to the WiFi airtime fairness problem that Toke knows
all too much about :)
We want fairness of time on the bottleneck medium. Aiming for fairness
of goodput to each host allows less efficient hosts to use more than
their fair share of the medium - reducing the efficiency of the whole
network and weakening incentives to be more efficient.