[Bloat] Updated Bufferbloat Test

Thu Feb 25 00:56:55 EST 2021

Thanks for the feedback, Dave!

> 0) "average" jitter is a meaningless number. In the case of a videoconferencing application, what matters most is max jitter, where the app will choose to ride the top edge of that, rather than follow it. I'd prefer using a 98% number, rather than 75% number, to weight where the typical delay in a videoconfernce might end up.

Both DSLReports and Ookla's desktop app report jitter as an average
rather than as a max number, so I'm a little hesitant to go against
the norm - users might find it a bit surprising to see much larger
jitter numbers reported. We're also not taking a whole ton of latency
tests in each phase, so the 98% will often end up being the max
number.

With regards to the videoconferencing, we actually ran some real-world
tests of Zoom with various levels of bufferbloat/jitter/latency, and
calibrated our "real-world results" table on that basis. We used
average jitter in those tests ... I think if we used 98% or even 95%
the allowable number would be quite high.

> 1) The worst case scenario of bloat affecting a users experience is during a simultaneous up and download, and I'd rather you did that rather than test them separately. Also you get a more realistic figure for the actual achievable bandwidth under contention and can expose problems like strict priority queuing in one direction or another locking out further flows.

We did consider this based on another user's feedback, but didn't
implement it. Perhaps we can do this next time we revisit, though!

> This points to any of number of problems (features!) It's certainly my hope that all the cdn makers at this point have installed bufferbloat mitigations. Testing a cdn's tcp IS a great idea, but as a bufferbloated test, maybe not so much.

We chose to use a CDN because it seemed like the only feasible way to
saturate gigabit links at least somewhat consistently for a meaningful
part of the globe, without setting up a whole lot of servers at quite
high cost.

But we weren't aware that bufferbloat could be abated from the CDN's
end. This is a bit surprising to me, as our test results indicate that
bufferbloat is regularly an issue even though we're using a CDN for
the speed and latency tests. For example, these are the results on my
own connection here (Cox, in Southern California), showing meaningful
bufferbloat:

https://www.waveform.com/tools/bufferbloat?test-id=ece467bd-e07a-45ea-9db6-e64d8da2c1d2

I get even larger bufferbloat effects when running the test on a 4G LTE network:

https://www.waveform.com/tools/bufferbloat?test-id=e99ae561-88e0-4e1e-bafd-90fe1de298ac

If the CDN was abating bufferbloat, surely I wouldn't see results like these?

> 3) Are you tracking an ecn statistics at this point (ecnseen)?

We are not, no. I'd definitely be curious to see if we can add this in
the future, though!

Best,

On Wed, Feb 24, 2021 at 2:10 PM Dave Taht <dave.taht at gmail.com> wrote:
>
> So I've taken a tiny amount of time to run a few tests. For starters,
> thank you very much
> for your dedication and time into creating such a usable website, and faq.
>
> I have several issues though I really haven't had time to delve deep
> into the packet captures. (others, please try taking em, and put them
> somewhere?)
>
> 0) "average" jitter is a meaningless number. In the case of a
> videoconferencing application,
> what matters most is max jitter, where the app will choose to ride the
> top edge of that, rather than follow it. I'd prefer using a 98%
> number, rather than 75% number, to weight where the typical delay in a
> videoconfernce might end up.
>
> 1) The worst case scenario of bloat affecting a users experience is
> during a simultaneous up and download, and I'd rather you did that
> rather than test them separately. Also you get
> a more realistic figure for the actual achievable bandwidth under
> contention and can expose problems like strict priority queuing in one
> direction or another locking out further flows.
>
> 2) I get absurdly great results from it with or without sqm on on a
> reasonably modern cablemodem (buffercontrol and pie and a cmts doing
> the right things)
>
> This points to any of number of problems (features!) It's certainly my
> hope that all the cdn makers at this point have installed bufferbloat
> mitigations. Testing a cdn's tcp IS a great idea, but as a
> bufferbloated test, maybe not so much.
>
> The packet capture of the tcp flows DOES show about 60ms jitter... but
> no loss. Your test shows:
>
> https://www.waveform.com/tools/bufferbloat?test-id=6fc7dd95-8bfa-4b76-b141-ed423b6580a9
>
> And is very jittery in the beginning of the test on its estimates. I
> really should be overjoyed at knowing a cdn is doing more of the right
> things, but in terms of a test... and linux also has got a ton of
> mitigations on the client side.
>
> 3) As a side note, ecn actually is negotiated on the upload, if it's
> enabled on your system.
> Are you tracking an ecn statistics at this point (ecnseen)? It is not
> negotiated on the download (which is fine by me).
>
> I regrettable at this precise moment am unable to test a native
> cablemodem at the same speed as a sqm box, hope to get further on this
> tomorrow.
>
> Again, GREAT work so far, and I do think a test tool for all these
> cdns - heck, one that tested all of them at the same time, is very,
> very useful.
>
> On Wed, Feb 24, 2021 at 10:22 AM Sina Khanifar <sina at waveform.com> wrote:
> >
> > Hi all,
> >
> > A couple of months ago my co-founder Sam posted an early beta of the
> > Bufferbloat test that we’ve been working on, and Dave also linked to
> > it a couple of weeks ago.
> >
> > Thank you all so much for your feedback - we almost entirely
> > redesigned the tool and the UI based on the comments we received.
> > We’re almost ready to launch the tool officially today at this URL,
> > but wanted to show it to the list in case anyone finds any last bugs
> > that we might have overlooked:
> >
> > https://www.waveform.com/tools/bufferbloat
> >
> > If you find a bug, please share the "Share Your Results" link with us
> > along with what happened. We capture some debugging information on the
> > backend, and having a share link allows us to diagnose any issues.
> >
> > This is really more of a passion project than anything else for us –
> > we don’t anticipate we’ll try to commercialize it or anything like
> > that. We're very thankful for all the work the folks on this list have
> > done to identify and fix bufferbloat, and hope this is a useful
> > contribution. I’ve personally been very frustrated by bufferbloat on a
> > range of devices, and decided it might be helpful to build another
> > bufferbloat test when the DSLReports test was down at some point last
> > year.
> >
> > Our goals with this project were:
> >   * To build a second solid bufferbloat test in case DSLReports goes down again.
> >   * Build a test where bufferbloat is front and center as the primary
> > purpose of the test, rather than just a feature.
> >   * Try to explain bufferbloat and its effect on a user's connection
> > as clearly as possible for a lay audience.
> >
> > A few notes:
> >   * On the backend, we’re using Cloudflare’s CDN to perform the actual
> > download and upload speed test. I know John Graham-Cunning has posted
> > to this list in the past; if he or anyone from Cloudflare sees this,
> > we’d love some help. Our Cloudflare Workers are being
> > bandwidth-throttled due to having a non-enterprise grade account.
> > We’ve worked around this in a kludgy way, but we’d love to get it
> > resolved.
> >   * We have lots of ideas for improvements, e.g. simultaneous
> > upload/downloads, trying different file size chunks, time-series
> > latency graphs, using WebRTC to test UDP traffic etc, but in the
> > interest of getting things launched we're sticking with the current
> > featureset.
> >   * There are a lot of browser-specific workarounds that we had to
> > implement, and latency itself is measured in different ways on
> > Safari/Webkit vs Chromium/Firefox due to limitations of the
> > PerformanceTiming APIs. You may notice that latency is different on
> > different browsers, however the actual bufferbloat (relative increase
> > in latency) should be pretty consistent.
> >
> > In terms of some of the changes we made based on the feedback we
> > receive on this list:
> >
> > Based on Toke’s feedback:
> > https://lists.bufferbloat.net/pipermail/bloat/2020-November/015960.html
> > https://lists.bufferbloat.net/pipermail/bloat/2020-November/015976.html
> >   * We changed the way the speed tests run to show an instantaneous
> > speed as the test is being run.
> >   * We moved the bufferbloat grade into the main results box.
> >   * We tried really hard to get as close to saturating gigabit
> > connections as possible. We redesigned completely the way we chunk
> > files, added a “warming up” period, and spent quite a bit optimizing
> > our code to minimize CPU usage, as we found that was often the
> > limiting factor to our speed test results.
> >   * We changed the shield grades altogether and went through a few
> > different iterations of how to show the effect of bufferbloat on
> > connectivity, and ended up with a “table view” to try to show the
> > effect that bufferbloat specifically is having on the connection
> > (compared to when the connection is unloaded).
> >   * We now link from the results table view to the FAQ where the
> > conditions for each type of connection are explained.
> >   * We also changed the way we measure latency and now use the faster
> > of either Google’s CDN or Cloudflare at any given location. We’re also
> > using the WebTiming APIs to get a more accurate latency number, though
> > this does not work on some mobile browsers (e.g. iOS Safari) and as a
> > result we show a higher latency on mobile devices. Since our test is
> > less a test of absolute latency and more a test of relative latency
> > with and without load, we felt this was workable.
> >   * Our jitter is now an average (was previously RMS).
> >   * The “before you start” text was rewritten and moved above the start button.
> >   * We now spell out upload and download instead of having arrows.
> >   * We hugely reduced the number of cross-site scripts. I was a bit
> > embarrassed by this if I’m honest - I spent a long time building web
> > tools for the EFF, where we almost never allowed any cross-site
> > scripts. * Our site is hosted on Shopify, and adding any features via
> > their app store ends up adding a whole lot of gunk. But we uninstalled
> > some apps, rewrote our template, and ended up removing a whole lot of
> > the gunk. There’s still plenty of room for improvement, but it should
> > be a lot better than before.
> >
> > Based on Dave Collier-Brown’s feedback:
> > https://lists.bufferbloat.net/pipermail/bloat/2020-November/015966.html
> >   * We replaced the “unloaded” and “loaded” language with “unloaded”
> > and then “download active”  and “upload active.” In the grade box we
> > indicate that, for example, “Your latency increased moderately under
> > load.”
> >   * We tried to generally make it easier for non-techie folks to
> > understand by emphasizing the grade and adding the table showing how
> > bufferbloat affects some commonly-used services.
> >   * We didn’t really change the candle charts too much - they’re
> > mostly just to give a basic visual - we focused more on the actual
> > meat of the results above that.
> >
> > Based on Sebastian Moeller’s feedback:
> > https://lists.bufferbloat.net/pipermail/bloat/2020-November/015963.html
> >   * We considered doing a bidirectional saturating load, but decided
> > to skip on implementing it for now. * It’s definitely something we’d
> > like to experiment with more in the future.
> >   * We added a “warming up” period as well as a “draining” period to
> > help fill and empty the buffer. We haven’t added the option for an
> > extended test, but have this on our list of backlog changes to make in
> > the future.
> >
> > Based on Y’s feedback (link):
> > https://lists.bufferbloat.net/pipermail/bloat/2020-November/015962.html
> >   * We actually ended up removing the grades, but we explained our
> > criteria for the new table in the FAQ.
> >
> > Based on Greg White's feedback (shared privately):
> > * We added an FAQ answer explaining jitter and how we measure it.
> >
> > We’d love for you all to play with the new version of the tool and
> > send over any feedback you might have. We’re going to be in a feature
> > freeze before launch but we'd love to get any bugs sorted out. We'll
> > likely put this project aside after we iron out a last round of bugs
> > and launch, and turn back to working on projects that help us pay the
> > bills, but we definitely hope to revisit and improve the tool over
> > time.
> >
> > Best,
> >
> > Sina, Arshan, and Sam.
> > _______________________________________________
> > Bloat mailing list
> > Bloat at lists.bufferbloat.net
> > https://lists.bufferbloat.net/listinfo/bloat
>
>
>
> --
> "For a successful technology, reality must take precedence over public
> relations, for Mother Nature cannot be fooled" - Richard Feynman
>
> dave at taht.net <Dave Täht> CTO, TekLibre, LLC Tel: 1-831-435-0729