[Make-wifi-fast] Uplink vs downlink latency

[Bob McMahon]

I'm thinking ping may not be ideal for benchmarking OFDMA effects on
latency.  Also, the end/end latency preferred seems to me the socket
write() to final socket read() per that write(). Also, for TCP, there are
the connect times. I realize network stack guys focus on stack related
measurements, e.g. RTT, but the latencies users experience include the
application level and system level os interactions.

Just some food or thought.

Bob


On Wed, Apr 29, 2020 at 5:07 PM Dave Taht <dave.taht at gmail.com> wrote:

> throughput and latency are interrelated, whats the throughput?
>
> On Wed, Apr 29, 2020 at 2:40 PM Tim Higgins <tim at smallnetbuilder.com>
> wrote:
> >
> > Hi all,
> >
> > I finally have my testbed working the way I want and am starting to run
> tests to see if OFDMA does anything useful.
> >
> > This will all be covered in detail in an upcoming SmallNetBuilder
> article. But I wanted to sanity check something with this esteemed group.
> >
> > The tests are basically the flent rtt_fair_var up and down tests ported
> to the octoScope platform I use for WiFi testing.
> > The initial work was done on flent, with a lot of hand-holding from
> Toke. (Thank you, Toke!)
> >
> > Using 4 Intel AX200 STAs on Win10. iperf3 is running traffic using
> TCP/IP with unthrottled bandwidth. I've taken Bjørn's idea and have each
> STA using a different DSCP priority level, but with TCP/IP traffic, not
> UDP. I'm sticking to using CS0-7 equivalents and confirmed that the iperf3
> --dscp values properly translate to the intended WiFi priority levels.
> Each STA has a different priority, either CS0,3,5 or 6 (best effort,
> excellent effort, video and voice).
> >
> > Ping is used to measure latency and always runs from AP to STA. Only
> TCP/IP traffic direction is reversed between the down and uplink tests.
> >
> > One thing that jumps out immediately is that uplink latencies are *much*
> lower than downlink, with either OFDMA on or off. Attached are three
> examples. The CDFs are average latency of the 4 STAs.
> >
> > The NETGEAR R7800 is a 4x4 AC Qualcomm-based. I'm using this as a
> baseline product.
> >
> > The NETGEAR RAX15 is 2x2 AX Broadcom-based. You can see what I mean when
> I say OFDMA doesn't help.
> >
> > Does this much difference between up and downlink latency pass the sniff
> test?
> >
> > ===
> > Tim
> > _______________________________________________
> > Make-wifi-fast mailing list
> > Make-wifi-fast at lists.bufferbloat.net
> > https://lists.bufferbloat.net/listinfo/make-wifi-fast
>
>
>
> --
> Make Music, Not War
>
> Dave Täht
> CTO, TekLibre, LLC
> http://www.teklibre.com
> Tel: 1-831-435-0729
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