[Cerowrt-devel] [Bloat] Two d-link products tested for bloat...

Dave Taht dave.taht at gmail.com
Wed Feb 25 23:37:40 EST 2015

On Wed, Feb 25, 2015 at 8:22 PM, Isaac Konikoff
<konikofi at candelatech.com> wrote:
> On 02/25/2015 04:23 PM, Dave Taht wrote:
>> On Wed, Feb 25, 2015 at 4:18 PM, Jonathan Morton <chromatix99 at gmail.com>
>> wrote:
>>>> Here's a comparison plot of box totals:
>>> http://www.candelatech.com/downloads/rtt_fair4be-comparison-box-plot.png
>>> That's a real mess. All of them utterly fail to get download bandwidth
>>> anywhere near the upload (am I right in assuming it should ideally be
>>> about
>>> equal?), and the only ones with even halfway acceptable latency are the
>>> ones
>>> with least throughput in either direction.
>> And I suspect that this was a test at the highest possible MCS rates
>> and txpower. Isaac?
> Yes, highest MCS for each AP and fw defaulted tx power. I can experiment
> with attenuation and lower MCS rates as well.

Be prepared to be horrified in disbelief at your results at the lower
rates... and post them anyway.

I note that rtt_fair4be is a pretty stressful, artificial benchmark,
and to truly stress things out requires more
than one tcp flow per station in each direction, or attempting to also
exercise the 802.11e queues. Or interference. Or multicast.

I do believe, that once these enormous latencies are clobbered via
various techniques in make-wifi-fast that it is possible to get
bandwidth per station over tcp to degrade nearly linearly, and achieve
close to the theoretical rate of the air, and for latencies to remain
(on this 4 station test) typically in the 4-14ms range at all but the
lowest MCS rates.

IMHO an AP that one day does well on these tests will also do much
better on a variety of others. :)

btw, I show a detailed graph of TCP's actual behavior under
circumstances like these
at nearly every talk, with data taken on the actual conference wifi.
It never occurred to me once, to show the bar chart! (out of the 14+
plots available).

It might be helpful on your next test run to also do the simplest
tests to a single station over each AP
for a reference (tcp_upload, tcp_download, and tcp_bidirectional).

>>> - Jonathan Morton

Dave Täht
Let's make wifi fast, less jittery and reliable again!


More information about the Cerowrt-devel mailing list