Re: [Bloat] [Make-wifi-fast] The most wonderful video ever about bufferbloat

[Bob McMahon <bob.mcmahon@broadcom.com>]

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I agree with Stuart that there is no reason for shared lines in the first
place. It seems like a design flaw to have a common queue that congests in
a way that impacts the one transmit unit as the atomic forwarding plane
unit.  The goal of virtual output queueing
<https://en.wikipedia.org/wiki/Virtual_output_queueing> is to eliminate
head of line blocking, every egress transmit unit gets its own cashier with
no competition.  The VOQ queue depths should support one transmit unit and
any jitter through the switching subsystem - jitter for the case of
non-bloat and where a faster VOQ service rate can drain the VOQ.  If the
VOQ can't be drained per a faster service rate, then it's just one
transmit unit as the queue is now just a standing queue w/delay and no
benefit.

Many network engineers typically, though incorrectly, perceive a transmit
unit as one ethernet packet. With WiFi it's one Mu transmission or one Su
transmission, with aggregation(s), which is a lot more than one ethernet
packet but it depends on things like MCS, spatial stream powers, Mu peers,
etc. and is variable. Some data center designs have optimized the
forwarding plane for flow completion times so their equivalent transmit
unit is a mouse flow.

I perceive applying AQM to shared queue congestion as a mitigation
technique to a poorly designed forwarding plane. The hope is that
transistor engineers don't do this and "design out the lines" from the
beginning. Better switching engineering vs queue management applied
afterwards as a mitigation technique.

Bob

On Mon, Oct 17, 2022 at 7:58 PM David Lang via Make-wifi-fast <
make-wifi-fast@lists.bufferbloat.net> wrote:

> On Mon, 17 Oct 2022, Dave Taht via Bloat wrote:
>
> > On Mon, Oct 17, 2022 at 5:02 PM Stuart Cheshire <cheshire@apple.com>
> wrote:
> >>
> >> On 9 Oct 2022, at 06:14, Dave Taht via Make-wifi-fast <
> make-wifi-fast@lists.bufferbloat.net> wrote:
> >>
> >> > This was so massively well done, I cried. Does anyone know how to get
> in touch with the ifxit folk?
> >> >
> >> > https://www.youtube.com/watch?v=UICh3ScfNWI
> >>
> >> I’m surprised that you liked this video. It seems to me that it repeats
> all the standard misinformation. The analogy they use is the standard
> terrible example of waiting in a long line at a grocery store, and the
> “solution” is letting certain traffic “jump the line, angering everyone
> behind them”.
> >
> > Accuracy be damned. The analogy to common experience resonates more.
>
> actually, fair queueing is more like the '15 items or less' lanes to speed
> through the people doing simple things rather than having them wait behind
> the
> mother of 7 doing their monthly shopping.
>
> David Lang_______________________________________________
> Make-wifi-fast mailing list
> Make-wifi-fast@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/make-wifi-fast

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