[Cerowrt-devel] [Bloat] Check out www.speedof.me - no Flash
David P. Reed
dpreed at reed.com
Fri Jul 25 11:05:19 EDT 2014
My experiments are a bit dated but if someone wants advice on how please ask. I'm flat out on my day job for the next month.
On Jul 25, 2014, Sebastian Moeller <moeller0 at gmx.de> wrote:
>On Jul 25, 2014, at 14:24 , Neil Davies <Neil.Davies at pnsol.com> wrote:
>> I have a deep worry over this style of single point measurement - and
>hence speed - as an appropriate measure.
> But how do you propose to measure the (bottleneck) link capacity then?
>It turns out for current CPE and CMTS/DSLAM equipment one typically can
>not relay on good QoE out of the box, since typically these devices do
>not use their (largish) buffers wisely. Instead the current remedy is
>to take back control over the bottleneck link by shaping the actually
>sent traffic to stay below the hardware link capacity thereby avoiding
>feeling the consequences of the over-buffering. But to do this is is
>quite helpful to get an educated guess what the bottleneck links
>capacity actually is. And for that purpose a speediest seems useful.
>> We know, and have evidence, that throughput/utilisation is not a good
>proxy for the network delivering suitable quality of experience. We
>work with organisation (Telco’s, large system integrators etc) where we
>spend a lot of time having to “undo” the consequences of “maximising
>speed”. Just like there is more to life than work, there is more to QoE
>> For more specific comments see inline
>> On 25 Jul 2014, at 13:09, Rich Brown <richb.hanover at gmail.com> wrote:
>>> Thanks for the note and the observations. My thoughts:
>>> 1) I note that speedof.me does seem to overstate the speed results.
>At my home, it reports 5.98mbps down, and 638kbps up, while
>betterspeedtest.sh shows 5.49/0.61 mbps. (speedtest.net gives numbers
>similar to the betterspeedtest.net script.)
>>> 2) I think we're in agreement about the peak upload rate that you
>point out is too high. Their measurement code runs in the browser. It
>seems likely that the browser pumps out a few big packets before
>getting flow control information, thus giving the impression that they
>can send at a higher rate. This comports with the obvious decay that
>ramps toward the long-term rate.
>> I think that its simpler than that, it is measuring the rate at which
>it can push packets out the interface - its real time rate is precisely
>that - it can not be the rate being reported by the far end, it can
>never exceed the limiting link. The long term average (if it is like
>other speed testers we’ve had to look into) is being measured at the
>TCP/IP SDU level by measuring the difference in time between the first
>and last timestamps of data stream and dividing that into the total
>data sent. Their “over-estimate” is because there are packets buffered
>in the CPE that have left the machine but not arrived at the far end.
> Testing from an openwrt router located at a high-symmetric-bandwidth
>location shows that speedof.me does not scale higher than ~ 130 Mbps
>server to client and ~15Mbps client to server (on the same connection I
>can get 130Mbps S2C and ~80Mbps C2S, so the asymmetry in the speedof.me
>results is not caused by my local environment).
> @Rich and Dave, this probably means that for the upper end of fiber
>and cable and VDSL connections speed of.me is not going to be a
>reliable speed measure… Side note www.sppedtest.net shows ~100Mbps S2C
>and ~100Mbps C2S, so might be better suited to high-upload links...
>>> 3) But that long-term speed should be at or below the theoretical
>long-term rate, not above it.
>> Agreed, but in this case knowing the sync rate already defines that
> I fully agree, but for ADSL the sync rate also contains a lot of
>encapsulation, so the maximum achievable TCP rate is at best ~90% of
>link rate. Note for cerowrt’s SQM system the link rate is exactly the
>right number to start out with at that system can take the
>encapsulation into account. But even then it is somewhat unintuitive to
>deduce the expected good-put from the link rate.
>>> Two experiments for you to try:
>>> a) What does betterspeedtest.sh show? (It's in the latest CeroWrt,
>in /usr/lib/CeroWrtScripts, or get it from github:
>>> b) What does www.speedtest.net show?
>>> I will add your question (about the inaccuracy) to the note that I
>want to send out to speedof.me this weekend. I will also ask that they
>include min/max latency measurements to their test, and an option to
>send for > 10 seconds to minimize any effect of PowerBoost…
> I think they do already, at least for the download bandwidth; they
>start with 128Kb and keep doubling the file size until a file takes
>longer than 8 seconds to transfer, they only claim to report the
>numbers from that last transferred file, so worst case with a stable
>link and a bandwidth > 16kbps ;), it has taken at least 12 seconds (4
>plus 8) of measuring before the end of the plot, so the bandwidth of at
>least the last half of the download plot should be representative even
>assuming power boost. Caveat, I assume that power boost will not be
>reset by the transient lack of data transfer between the differently
>sized files (but since it should involve the same IPs and port# why
>should power boost reset itself?).
>>> Best regards,
>>> On Jul 25, 2014, at 5:10 AM, Neil Davies <neil.davies at pnsol.com>
>>>> You may want to check how accurate they are to start.
>>>> I just ran a “speed test” on my line (which I have complete control
>and visibility over the various network elements) and it reports an
>average “speed” (in the up direction) that is in excess of the capacity
>of the line, it reports the maximum rate at nearly twice the best
>possible rate of the ADSL connection.
>>>> Doesn’t matter how pretty it is, if its not accurate it is of no
>use. This is rather ironic as the web site claims it is the “smartest
>and most accurate”!
>>>> PS pretty clear to me what mistake they’ve made in the measurement
>process - its to do with incorrect inference and hence missing the
>>>> On 20 Jul 2014, at 14:19, Rich Brown <richb.hanover at gmail.com>
>>>>> Doc Searls
>mentioned in passing that he uses a new speed test website. I checked
>it out, and it was very cool…
>>>>> www.speedof.me is an all-HTML5 website that seems to make accurate
>measurements of the up and download speeds of your internet connection.
>It’s also very attractive, and the real-time plots of the speed show
>interesting info. (screen shot at:
>>>>> Now if we could get them to a) allow longer/bigger tests to
>circumvent PowerBoost, and b) include a latency measurement so people
>could point out their bufferbloated equipment.
>>>>> I'm going to send them a note. Anything else I should add?
>>>>> Bloat mailing list
>>>>> Bloat at lists.bufferbloat.net
>> Bloat mailing list
>> Bloat at lists.bufferbloat.net
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>Cerowrt-devel at lists.bufferbloat.net
-- Sent from my Android device with K-@ Mail. Please excuse my brevity.
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