[Make-wifi-fast] Uplink vs downlink latency

[Dave Taht]

It would be kind of cool if you added a ubnt uap-pro mesh router to
your mix. And (eventually) - reflashed it with our latest openwrt
stuff. that's a 3x3 802.11ac product that I know for sure has most of
our stuff in the default firmware nowadays.

On Thu, Apr 30, 2020 at 7:18 AM Tim Higgins <tim at smallnetbuilder.com> wrote:
>
> I take your point, Bob, and agree single-ended latency measurements like you produce with iperf would be more technically correct.
>
> I write and review for a consumer audience, where ping is the standard for latency aka lag measurement. So that's why I'm using ping.
> That, and the fact that iperf isn't integrated into octoScope's toolset yet. But they're working on it and all their STA instruments are properly time-synced, so the measurements will be accurate.
>
> Thank your for all your work in iperf, BTW. The features you've added are a welcome improvement.
> ===========
> Tim
> On 4/29/2020 8:32 PM, Bob McMahon wrote:
>
> 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
>> > _______________________________________________
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>>
>>
>>
>> --
>> Make Music, Not War
>>
>> Dave Täht
>> CTO, TekLibre, LLC
>> http://www.teklibre.com
>> Tel: 1-831-435-0729
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>
>
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-- 
Make Music, Not War

Dave Täht
CTO, TekLibre, LLC
http://www.teklibre.com
Tel: 1-831-435-0729