Re: [Bloat] DSLReports Speed Test has latency measurement built-in

[jb <justin@dslr.net>]

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Hey there is nothing wrong with Megapath ! they were my second  ISP after
Northpoint went bust.
If I had a time machine, and went back to 2001, I'd be very happy with
Megapath.. :)

Anyway Rich has some good ideas for how to display the latency during the
test progress and yes
that is the plan, to do that.

The results page, for the sake of non-confusion by random people, does just
show the smoothed
line and not the instant download speeds. I'm not confident enough that the
instant speeds
relate 1:1 with what is going on at your interface as unfortunately modern
browsers don't
give nearly enough feedback on how uploads are going compared to how they
instrument
downloads - which are almost on a packet by packet level. You would hope
they would pass
back events regularly but unless then line is pretty fast, they don't. They
go quiet and catch up
and meanwhile the actual upload might be steady.

The retransmit stats and congestion window and other things come from the
linux tcp structures
on the server side. Retransmits are not necessarily lost packets, it can
just be TCP getting confused by
a highly variable RTT and re-sending too soon. But on a very good
connection (google fiber) that
column is 0%. On some bad connections, it can be 20%+ Often it is between 1
and 3%.

Yes the speed test is trying to drive the line to capacity but not force
feeding, it is just TCP after
all, and all streams should find their relative place in the available
bandwidth and lost packets
should be rare when the underlying network is good quality. At least, that
is what I've seen. I'm
far from understanding the congestion algorithms etc. However I did find it
somewhat surprising
that whether one stream or 20, it all sort of works out with roughly the
same efficiency.

With more data I think the re-transmits and other indicators can just show
real problems, even
despite that the test tends to (hopefully) find your last mile sync speed
and drive it to capacity.

-justin

On Sun, Apr 19, 2015 at 5:36 PM, David Lang <david@lang.hm> wrote:

> As a start, the ping time during the test that shows up in the results
> page is good, but you should show that on the main screen, not just in the
> results+share tab.
>
> it looked like the main test was showing when the upload was stalled,
> (white under the line instead of color), but this didn't show up in the
> report tab.
>
> I also think that the retransmit stats are probably worth watching and
> doing something with. You are trying to drive the line to full capacity, so
> some drops/retransmts are expected. How many re expected vs how many are
> showing up?
>
> http://www.dslreports.com/speedtest/320230 (and now you see my pathetic
> link)
>
> David Lang
>
>
> On Sun, 19 Apr 2015, jb wrote:
>
>  Date: Sun, 19 Apr 2015 15:26:51 +1000
>> From: jb <justin@dslr.net>
>> To: Dave Taht <dave.taht@gmail.com>, bloat@lists.bufferbloat.net
>> Subject: Re: [Bloat] DSLReports Speed Test has latency measurement
>> built-in
>>
>>
>> The graph below the upload and download is what is new.
>> (unfortunately you do have to be logged into the site to see this)
>> it shows the latency during the upload and download, color coded. (see
>> attached image).
>>
>> In your case during the upload it spiked to ~200ms from ~50ms but it was
>> not so bad. During upload, there were no issues with latency.
>>
>> I don't want to force anyone to sign up, just was making sure not to
>> confuse anonymous users with more information than they knew what to do
>> with. When I'm clear how to present the information, I'll make it
>> available
>> by default, to anyone member or otherwise.
>>
>> Also, regarding your download, it stalled out completely for 5 seconds..
>> Hence the low conclusion as to your actual speed. It picked up to full
>> speed again at the end. It basically went
>> 40 .. 40 .. 40 .. 40 .. 8 .. 8 .. 8 .. 40 .. 40 .. 40
>> which explains why the Latency measurements in blue are not all high.
>> A TCP stall? you may want to re-run or re-run with Chrome or Safari to see
>> if it is reproducible. Normally users on your ISP have flat downloads with
>> no stalls.
>>
>> thanks
>> -Justin
>>
>>
>>
>>  On Sun, Apr 19, 2015 at 2:01 PM, Dave Taht <dave.taht@gmail.com> wrote:
>>>
>>>  What I see here is the same old latency, upload, download series, not
>>>> latency and bandwidth at the same time.
>>>>
>>>> http://www.dslreports.com/speedtest/319616
>>>>
>>>> On Sat, Apr 18, 2015 at 5:57 PM, Rich Brown <richb.hanover@gmail.com>
>>>> wrote:
>>>>
>>>>> Folks,
>>>>>
>>>>> I am delighted to pass along the news that Justin has added latency
>>>>>
>>>> measurements into the Speed Test at DSLReports.com.
>>>>
>>>>>
>>>>> Go to: https://www.dslreports.com/speedtest and click the button for
>>>>>
>>>> your Internet link. This controls the number of simultaneous connections
>>>> that get established between your browser and the speedtest server.
>>>> After
>>>> you run the test, click the green "Results + Share" button to see
>>>> detailed
>>>> info. For the moment, you need to be logged in to see the latency
>>>> results.
>>>> There's a "register" link on each page.
>>>>
>>>>>
>>>>> The speed test measures latency using websocket pings: Justin says that
>>>>>
>>>> a zero-latency link can give 1000 Hz - faster than a full HTTP ping. I
>>>> just
>>>> ran a test and got 48 msec latency from DSLReports, while ping
>>>> gstatic.com gave 38-40 msec, so they're pretty fast.
>>>>
>>>>>
>>>>> You can leave feedback on this page -
>>>>>
>>>>
>>>> http://www.dslreports.com/forum/r29910594-FYI-for-general-feedback-on-the-new-speedtest
>>>> - or wait 'til Justin creates a new Bufferbloat topic on the forums.
>>>>
>>>>>
>>>>> Enjoy!
>>>>>
>>>>> Rich
>>>>> _______________________________________________
>>>>> Bloat mailing list
>>>>> Bloat@lists.bufferbloat.net
>>>>> https://lists.bufferbloat.net/listinfo/bloat
>>>>>
>>>>
>>>>
>>>>
>>>> --
>>>> Dave Täht
>>>> Open Networking needs **Open Source Hardware**
>>>>
>>>> https://plus.google.com/u/0/+EricRaymond/posts/JqxCe2pFr67
>>>> _______________________________________________
>>>> Bloat mailing list
>>>> Bloat@lists.bufferbloat.net
>>>> https://lists.bufferbloat.net/listinfo/bloat
>>>>
>>>>
>>>
>>>

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