On 18/04/16 07:03 PM, David Collier-Brown wrote:
I haven't internalized this yet, but my instantaneous reaction is:
* a radar screen is something people have been educated to
understand, so that's cool, and
Rat's, it all went on one line. This is more like what I meant
* over time, plotting the time taken for <something> against the
load in <something>s is what capacity planners expect to see: "_/"
--dave
On 18/04/16 06:48 PM, David Lang wrote:
On Mon, 18 Apr 2016, Dave Taht wrote:
I have been sitting here looking at wifi air packet captures off and
on for years now, trying to come up with a representation, over time,
of what the actual airtime usage (and one day, fairness) would look
like. Believe me, looking at the captures is no fun, and (for example)
wireshark tends to misinterpret unreceived retries at different rates
inside a txop as tcp retries (which, while educational, makes it hard
to see actual retries)...
Finally today, I found a conceptual model that "fits" - and it's kind
of my hope that something already out there does this from packet
captures. (?) Certainly there are lots of great pie chart tools out
there...
Basically you start with a pie chart representing a fixed amount of
time - say, 128ms. Then for each device transmitting you assign a
slice of the pie for the amount of airtime used. Then, you can show
the amount of data transmitted in that piece of the pie by increasing
the volume plotted for that slice of the pie. And you sweep around
continually (like a radar scanning or a timepiece's pointer) to show
progress over time, and you show multicast and other traffic as eating
the whole pie for however long it lasts.
conceptually it looks a bit like this:
http://blog.cerowrt.org/images/fairness.png (I borrowed this graph
from
http://www.webdesignerdepot.com/2013/11/easily-create-stunning-animated-charts-with-chart-js/
)
Another way to do it would be to have the pie represent all the
stations on the network, and to have the "sweep hand" jump between
them...
does it really matter how much data is passed during the timeslice as
opposed to just how much airtime is used? (and there will be a large
chunk of airtime unused for various reasons, much of which you will
not be able to attribute to any one station, and if you do get full
transmit data from each station, you can end up with >100% airtime
use attempted)
I would be looking at a stacked area graph to show changes over time
(a particular source will come and go over time)
I would either do two graphs, one showing data successfully
transmitted, the other showing airtime used (keeping colors/order
matching between the two graphs), or if you have few enough stations,
one graph with good lines between the stations and have the color
represent the % of theoretical peak data transmission to show the
relative efficiency of the different stations.
While the radar sweep updating of a pie graph is a neat graphic, it
doesn't really let you see what's happening over time.
David Lang
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--
David Collier-Brown, | Always do right. This will gratify
System Programmer and Author | some people and astonish the rest
[email protected] | -- Mark Twain
--
David Collier-Brown, | Always do right. This will gratify
System Programmer and Author | some people and astonish the rest
[email protected] | -- Mark Twain
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