[Cerowrt-devel] what stats do people want from conference wifi?

[David Lang]

On Sat, 7 Feb 2015, Aaron Wood wrote:

> I would love to see this data, especially since insights into dense wifi
> environments is rare.

exactly what I'm trying to provide

> It seems like this might be a fascinating time to get stats from Minstrel,
> for which rates clients are connected at:
>
> Do they connect at high rates at all?
> Do they stay stable at high rates, or do they see all the noise of other
> APs and drop to slower rates accordingly?

I'm not familar with that tool, but I'll try to gather anything. pointers 
please?

Under normal conditions I'm happy to go researching, but since we install this 
in 10 days and are live in 11 (with all prep work having to work around my day 
job), I'm going to need pretty direct pointers on eithre stats to gather, 
patches to apply, or particular software packages to include and at least strong 
hints on any required configs.

David Lang

> -Aaron
>
> On Sat, Feb 7, 2015 at 6:02 PM, David Lang <david at lang.hm> wrote:
>
>> In the next few days I'm going to be building the openwrt images to use at
>> the SCaLE conference. I will have ~50 APs deployed supporting ~3k
>> attendees. This will be running on WNDR3700v2 and WNDR3800 APs. Since I am
>> compiling the firmware myself, I can add in patches to gather and log stats
>> for things that are not normally reported
>>
>> The wireless network architecture is:
>>
>> separate ESSIDs for 2.4 vs 5.
>> each band gets bridged to a different VLAN
>> the APs are configured not to forward broadcast traffic from one wireless
>> client to another on the same AP (although broadcast traffic from one AP
>> probably goes out others after hitting the wire now that I think about it)
>> I have all logs from the APs sent to a central logserver
>> I have use rrdtool to catpture normal bandwith/cpu/etc stats
>> I also have rrdtool capture how many clients are connected to each ESSID
>> every minute.
>>
>>
>> What else can I gather related to the wifi?
>>
>> I think it would be useful if we could gather info along the lines of
>>
>> amount of airtime used
>>
>> how much latency is added to packets while waiting to transmit because
>> it's hearing something else transmit?
>>
>> amount of unused airtime available
>>
>> average effective bit rate
>>
>> percentage of time spent doing broadcasts (things required to operate at
>> the lowest bit rate)
>>
>>
>>
>>
>> Part of the reason that I compile my own firmware images is that I
>> completely disable connection tracking in the kernel (because clients may
>> move from one AP to another in the middle of a connection it's a waste of
>> cpu and memory to track), and as a result of these optimizations, there is
>> actually quite a bit of CPU available. The boxes almost never hit 20% cpu
>> utilization, so there's quite a bit available to gather other stats.
>>
>> some of the stats I gather are in messages spit out by the kernel, others
>> from scrips running on the box querying things in /proc or /sys, and others
>> from watching logs and summarizing them once a minute. I even have a
>> process that goes threough all the connection logs for the duration of the
>> show and graph how many unique MAC addresses we've seen and a breakdown
>> into the different vendor prefixes. If there's a way to get the data, I can
>> support it.
>>
>> If there are fq_codel stats that people would find interesting in this
>> environment, I can gather those as well (both on the APs and on the Debian
>> based firewall/gateway)
>>
>> David Lang
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>