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

[Bob McMahon]

It's too big because it's oversized so it's in the size domain. It's
basically Little's law's value for the number of items in a queue.

*Number of items in the system = (the rate items enter and leave the
system) x (the average amount of time items spend in the system)*


Which gets driven to the standing queue size when the arrival rate
exceeds the service rate - so the driving factor isn't the service and
arrival rates, but *the queue size *when *any service rate is less than an
arrival rate.*

In other words, one can find and measure bloat regardless of the
enter/leave rates (as long as the leave rate is too slow) and the value of
memory units found will always be the same.

Things like prioritizations to jump the line are somewhat of hacks at
reducing the service time for a specialized class of packets but nobody
really knows which packets should jump.  Also, nobody can define what
working conditions are so that's another problem with this class of tests.

Better maybe just to shrink the queue and eliminate all unneeded queueing
delays. Also, measure the performance per "user conditions" which is going
to be different for almost every environment (and is correlated to time and
space.) So any engineering solution is fundamentally suboptimal. Even
pacing the source doesn't necessarily do the right thing because that's
like waiting in the waitlist while at home vs the restaurant lobby. Few
care about where messages wait (unless the pitch is AQM is the only
solution that drives to a self-fulfilling prophecy - that's why the tests
have to come up with artificial conditions that can't be simply defined.)

Bob

On Mon, Oct 10, 2022 at 3:57 PM David Lang <david at lang.hm> wrote:

> On Mon, 10 Oct 2022, Bob McMahon via Bloat wrote:
>
> > I think conflating bufferbloat with latency misses the subtle point in
> that
> > bufferbloat is a measurement in memory units more than a measurement in
> > time units. The first design flaw is a queue that is too big. This
> youtube
> > video analogy doesn't help one understand this important point.
>
> but the queue is only too big because of the time it takes to empty the
> queue,
> which puts us back into the time domain.
>
> David Lang
>
> > Another subtle point is that the video assumes AQM as the only solution
> and
> > ignores others, i.e. pacing at the source(s) and/or faster service
> rates. A
> > restaurant that let's one call ahead to put their name on the waitlist
> > doesn't change the wait time. Just because a transport layer slowed down
> > and hasn't congested a downstream queue doesn't mean the e2e latency
> > performance will meet the gaming needs as an example. The delay is still
> > there it's just not manifesting itself in a shared queue that may or may
> > not negatively impact others using that shared queue.
> >
> > Bob
> >
> >
> >
> > On Mon, Oct 10, 2022 at 2:40 AM Sebastian Moeller via Make-wifi-fast <
> > make-wifi-fast at lists.bufferbloat.net> wrote:
> >
> >> Hi Erik,
> >>
> >>
> >>> On Oct 10, 2022, at 11:32, Taraldsen Erik <erik.taraldsen at telenor.no>
> >> wrote:
> >>>
> >>> On 10/10/2022, 11:09, "Sebastian Moeller" <moeller0 at gmx.de> wrote:
> >>>
> >>>    Nice!
> >>>
> >>>> On Oct 10, 2022, at 07:52, Taraldsen Erik via Cake <
> >> cake at lists.bufferbloat.net> wrote:
> >>>>
> >>>> It took about 3 hours from the video was release before we got the
> >> first request to have SQM on the CPE's  we manage as a ISP.  Finally
> >> getting some customer response on the issue.
> >>>
> >>>       [SM] Will you be able to bump these requests to higher-ups and at
> >> least change some perception of customer demand for tighter latency
> >> performance?
> >>>
> >>> That would be the hope.
> >>
> >>         [SM} Excellent, hope this plays out as we wish for.
> >>
> >>
> >>>  We actually have fq_codel implemented on the two latest generations of
> >> DSL routers.  Use sync rate as input to set the rate.  Works quite well.
> >>
> >>         [SM] Cool, if I might ask what fraction of the sync are you
> >> setting the traffic shaper for and are you doing fine grained overhead
> >> accounting (or simply fold that into a grand "de-rating"-factor)?
> >>
> >>
> >>> There is also a bit of traction around speedtest.net's inclusion of
> >> latency under load internally.
> >>
> >>         [SM] Yes, although IIUC they are reporting the interquartile
> mean
> >> for the two loaded latency estimates, which is pretty conservative and
> only
> >> really "triggers" for massive consistently elevated latency; so I expect
> >> this to be great for detecting really bad cases, but I fear it is too
> >> conservative and will make a number of problematic links look OK. But
> hey,
> >> even that is leaps and bounds better than the old only idle latency
> report.
> >>
> >>
> >>> My hope is that some publication in Norway will pick up on that score
> >> and do a test and get some mainstream publicity with the results.
> >>
> >>         [SM] Inside the EU the challenge is to get national regulators
> and
> >> the BEREC to start bothering about latency-under-load at all, "some
> >> mainstream publicity" would probably help here as well.
> >>
> >> Regards
> >>         Sebastian
> >>
> >>
> >>>
> >>> -Erik
> >>>
> >>>
> >>>
> >>
> >> _______________________________________________
> >> Make-wifi-fast mailing list
> >> Make-wifi-fast at lists.bufferbloat.net
> >> https://lists.bufferbloat.net/listinfo/make-wifi-fast
> >
> >_______________________________________________
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>

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