[Cake] lan keyword affects host fairness

[Toke Høiland-Jørgensen]

Dave Taht <dave at taht.net> writes:

> Pete Heist <peteheist at gmail.com> writes:
>
>>     On Nov 23, 2017, at 10:44 AM, Jonathan Morton <chromatix99 at gmail.com> wrote:
>>     
>>     This is most likely an interaction of the AQM with Linux' scheduling
>>     latency.
>>
>>     At the 'lan' setting, the time comstants are similar in magnitude to the
>>     delays induced by Linux itself, so congestion might be signalled
>>     prematurely. The flows will then become sparse and total throughput reduced,
>>     leaving little or no back-pressure for the fairness logic to work against.
>
> Agreed. 
>
> man page add:
>
> At the 'lan' setting(1ms), the time constants are similar in magnitude
> to the jitter in the Linux kernel itself, so congestion might be
> signalled prematurely. The flows will then become sparse and total
> throughput reduced, leaving little or no back-pressure for the fairness
> logic to work against. Use the "metro" setting for local lans unless you
> have a custom kernel.

Erm, doesn't this make the 'lan' keyword pretty much useless? So why not
just remove it? Or redefine it to something that actually works? 3ms?

-Toke