[Bloat] [Make-wifi-fast] graphing airtime fairness in wifi

[David Collier-Brown]

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
> davecb at spamcop.net            |                      -- Mark Twain


-- 
David Collier-Brown,         | Always do right. This will gratify
System Programmer and Author | some people and astonish the rest
davecb at spamcop.net           |                      -- Mark Twain

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