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

[Simon Barber]

If you set the window only a little bit larger than the actual BDP of the 
link then there will only be a little bit of data to fill buffer, so given 
large buffers it will take many connections to overflow the buffer.

Simon

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On April 21, 2015 4:18:10 PM jb <justin at dslr.net> wrote:

> Regarding the low TCP RWIN max setting, and smoothness.
>
> One remark up-thread still bothers me. It was pointed out (and it makes
> sense to me) that if you set a low TCP max rwin it is per stream, but if
> you do multiple streams you are still going to rush the soho buffer.
>
> However my observation with a low server rwin max was that the smooth
> upload graph was the same whether I did 1 upload stream or 6 upload
> streams, or apparently any number.
> I would have thought that with 6 streams, the PC is going to try to flood
> 6x as much data as 1 stream, and this would put you back to square one.
> However this was not what happened. It was puzzling that no matter what,
> one setting server side got rid of the chop.
> Anyone got any plausible explanations for this ?
>
> if not, I'll run some more tests with 1, 6 and 12, to a low rwin server,
> and post the graphs to the list. I might also have to start to graph the
> interface traffic on a sub-second level, rather than the browser traffic,
> to make sure the browser isn't lying about the stalls and chop.
>
> This 7800N has setting for priority of traffic, and utilisation (as a
> percentage). Utilisation % didn't help, but priority helped. Making web low
> priority and SSH high priority smoothed things out a lot without changing
> the speed. Perhaps "low" priority means it isn't so eager to fill its
> buffers..
>
> thanks
>
>
> On Wed, Apr 22, 2015 at 8:13 AM, jb <justin at dslr.net> wrote:
>
> > Today I've switched it back to large receive window max.
> >
> > The customer base is everything from GPRS to gigabit. But I know from
> > experience that if a test doesn't flatten someones gigabit connection they
> > will immediately assume "oh congested servers, insufficient capacity" and
> > the early adopters of fiber to the home and faster cable products are the
> > most visible in tech forums and so on.
> >
> > It would be interesting to set one or a few servers with a small receive
> > window, take them from the pool, and allow an option to select those,
> > otherwise they would not participate in any default run. Then as you point
> > out, the test can suggest trying those as an option for results with
> > chaotic upload speeds and probable bloat. The person would notice the
> > beauty of the more intimate connection between their kernel and a server,
> > and work harder to eliminate the problematic equipment. Or. They'd stop
> > telling me the test was bugged.
> >
> > thanks
> >
> >
> > On Wed, Apr 22, 2015 at 12:28 AM, David Lang <david at lang.hm> wrote:
> >
> >> On Tue, 21 Apr 2015, David Lang wrote:
> >>
> >>  On Tue, 21 Apr 2015, David Lang wrote:
> >>>
> >>>  I suspect you guys are going to say the server should be left with a
> >>>>> large
> >>>>> max receive window.. and let people complain to find out what their
> >>>>> issue
> >>>>> is.
> >>>>>
> >>>>
> >>>> what is your customer base? how important is it to provide faster
> >>>> service to teh fiber users? Are they transferring ISO images so the
> >>>> difference is significant to them? or are they downloading web pages where
> >>>> it's the difference between a half second and a quarter second? remember
> >>>> that you are seeing this on the upload side.
> >>>>
> >>>> in the long run, fixing the problem at the client side is the best
> >>>> thing to do, but in the meantime, you sometimes have to work around broken
> >>>> customer stuff.
> >>>>
> >>>
> >>> for the speedtest servers, it should be set large, the purpose is to
> >>> test the quality of the customer stuff, so you don't want to do anything on
> >>> your end that papers over the problem, only to have the customer think
> >>> things are good and experience problems when connecting to another server
> >>> that doesn't implement work-arounds.
> >>>
> >>
> >> Just after hitting send it occured to me that it may be the right thing
> >> to have the server that's being hit by the test play with these settings.
> >> If the user works well at lower settings, but has problems at higher
> >> settings, the point where they start having problems may be useful to know.
> >>
> >> David Lang
> >> _______________________________________________
> >> Bloat mailing list
> >> Bloat at lists.bufferbloat.net
> >> https://lists.bufferbloat.net/listinfo/bloat
> >>
> >>
> >
>
>
>
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