Re: [Rpm] Alternate definitions of "working condition" - unnecessary?

[Jonathan Morton <chromatix99@gmail.com>]

> On 7 Oct, 2021, at 3:11 am, Christoph Paasch <cpaasch@apple.com> wrote:
> 
>>> On 7 Oct, 2021, at 12:22 am, Dave Taht via Rpm <rpm@lists.bufferbloat.net> wrote:
>>> There are additional cases where, perhaps, the fq component works, and the aqm doesn't.
>> 
>> Such as Apple's version of FQ-Codel?  The source code is public, so we might as well talk about it.
> 
> Let's not just talk about it, but actually read it ;-)
> 
>> There are two deviations I know about in the AQM portion of that.  First is that they do the marking and/or dropping at the tail of the queue, not the head.  Second is that the marking/dropping frequency is fixed, instead of increasing during a continuous period of congestion as real Codel does.
> 
> We don't drop/mark locally generated traffic (which is the use-case we care abhout).
> We signal flow-control straight back to the TCP-stack at which point the queue
> is entirely drained before TCP starts transmitting again.
> 
> So, drop-frequency really doesn't matter because there is no drop.

Hmm, that would be more reasonable behaviour for a machine that never has to forward anything - but that is not at all obvious from the source code I found.  I think I'll need to run tests to see what actually happens in practice.

 - Jonathan Morton