Re: [ippm] Preliminary measurement comparison of "Working Latency" metrics

["MORTON JR., AL" <[e-mail]>]

(astute readers may have guessed that I pressed "send" too soon on previous message...)

I also conducted upstream tests this time, here are the results:
(capacity in Mbps, delays in ms, h and m are RPM categories, High and Medium)

Net Qual                           UDPST (RFC9097)              Ookla
UpCap     RPM    DelLD  DelMin     UpCap    RTTmin   RTTrange   UpCap    Ping(no load)
34        1821 h 33ms   11ms       23 (42)  28       0-252      22       8
22         281 m 214ms  8ms        27 (52)  25       5-248      22       8
22         290 m 207ms  8ms        27 (55)  28       0-253      22       9
21         330 m 182ms  11ms       23 (44)  28       0-255      22       7
22         334 m 180ms  9ms        33 (56)  25       0-255      22       9

The Upstream capacity measurements reflect an interesting feature that we can reliably and repeatably measure with UDPST. The first ~3 seconds of upstream data experience a "turbo mode" of ~50Mbps. UDPST displays this behavior in its 1 second sub-interval measurements and has a bimodal reporting option that divides the complete measurement interval in two time intervals to report an initial (turbo) max capacity and a steady-state max capacity for the later intervals. The UDPST capacity results present both measurements: steady-state first.

The capacity processing in networkQuality and Ookla appear to report the steady-state result. I watched the upstream capacity measurements on the Ookla app, and could easily see the initial rise to 40-50Mbps, then the drop to ~22Mbps for most of the test which determined the final result.

The working latency is about 200ms in networkQuality and about 280ms as measured by UDPST (RFC9097). Note that the networkQuality minimum delay is ~20ms lower than the UDPST RTTmin, so this accounts for some of the difference in working latency.  Also, we used the very dynamic Type C load adjustment/search algorithm in UDPST during all of this testing, which could explain the higher working latency to some degree. 

So, it's worth noting that the measurements needed for assessing working latency/responsiveness are available in the UDPST utility, and that the UDPST measurements are conducted on UDP transport (used by a growing fraction of Internet traffic).

comments welcome of course,
Al

> -----Original Message-----
> From: ippm <[e-mail]> On Behalf Of MORTON JR., AL
> Sent: Sunday, October 30, 2022 8:09 PM
> To: [e-mail]
> Subject: Re: [ippm] Preliminary measurement comparison of "Working Latency"
> metrics
> 
> 
> Hi again RPM friends and IPPM'ers,
> 
> As promised, I repeated the tests shared last week, this time using both the
> verbose (-v) and sequential (-s) dwn/up test options of networkQuality. I
> followed Sebastian's calculations as well.
> 
> Working Latency & Capacity Summary
> 
> Net Qual                           UDPST                        Ookla
> DnCap     RPM    DelLD  DelMin     DnCap    RTTmin   RTTrange   DnCap
> Ping(no load)
> 885       916 m  66ms   8ms        970      28       0-20       940      8
> 888      1355 h  44ms   8ms        966      28       0-23       940      8
> 891      1109 h  54ms   8ms        968      27       0-19       940      9
> 887      1141 h  53ms   11ms       966      27       0-18       937      7
> 884      1151 h  52ms   9ms        968      28       0-20       937      9
> 
> With the sequential test option, I noticed that networkQuality achieved nearly
> the maximum capacity reported almost immediately at the start of a test.
> However, the reported capacities are low by about 60Mbps, especially when
> compared to the Ookla TCP measurements.
> 
> The loaded delay (DelLD) is similar to the UDPST RTTmin + (the high end of the
> RTTrange), for example 54ms compared to (27+19=46). Most of the networkQuality
> RPM measurements were categorized as "High". There doesn't seem to be much
> buffering in the downstream direction.
> 
> 
> 
> > -----Original Message-----
> > From: ippm <[e-mail]> On Behalf Of MORTON JR., AL
> > Sent: Monday, October 24, 2022 6:36 PM
> > To: [e-mail]
> > Subject: [ippm] Preliminary measurement comparison of "Working Latency"
> > metrics
> >
> >
> > Hi RPM friends and IPPM'ers,
> >
> > I was wondering what a comparison of some of the "working latency" metrics
> > would look like, so I ran some tests using a service on DOCSIS 3.1, with the
> > downlink provisioned for 1Gbps.
> >
> > I intended to run apple's networkQuality, UDPST (RFC9097), and Ookla
> Speedtest
> > with as similar connectivity as possible (but we know that the traffic will
> > diverge to different servers and we can't change that aspect).
> >
> > Here's a quick summary of yesterday's results:
> >
> > Working Latency & Capacity Summary
> >
> > Net Qual                UDPST                        Ookla
> > DnCap     RPM           DnCap    RTTmin   RTTVarRnge DnCap    Ping(no load)
> > 878       62            970      28       0-19       941      6
> > 891       92            970      27       0-20       940      7
> > 891       120           966      28       0-22       937      9
> > 890       112           970      28       0-21       940      8
> > 903       70            970      28       0-16       935      9
> >
> > Note: all RPM values were categorized as Low.
> >
> > networkQuality downstream capacities are always on the low side compared to
> > others. We would expect about 940Mbps for TCP, and that's mostly what Ookla
> > achieved. I think that a longer test duration might be needed to achieve the
> > actual 1Gbps capacity with networkQuality; intermediate values observed were
> > certainly headed in the right direction. (I recently upgraded to Monterey
> 12.6
> > on my MacBook, so should have the latest version.)
> >
> > Also, as Sebastian Moeller's message to the list reminded me, I should have
> > run the tests with the -v option to help with comparisons. I'll repeat this
> > test when I can make time.
> >
> > The UDPST measurements of RTTmin (minimum RTT observed during the test) and
> > the range of variation above the minimum (RTTVarRnge) add-up to very
> > reasonable responsiveness IMO, so I'm not clear why RPM graded this access
> and
> > path as "Low". The UDPST server I'm using is in NJ, and I'm in Chicago
> > conducting tests, so the minimum 28ms is typical. UDPST measurements were
> run
> > on an Ubuntu VM in my MacBook.
> >
> > The big disappointment was that the Ookla desktop app I updated over the
> > weekend did not include the new responsiveness metric! I included the ping
> > results anyway, and it was clearly using a server in the nearby area.
> >
> > So, I have some more work to do, but I hope this is interesting-enough to
> > start some comparison discussions, and bring-out some suggestions.
> >
> > happy testing all,
> > Al
> >
> >
> >
> >
> > _______________________________________________
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> > [e-mail]
> >
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