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

[David Lang]

when you say "fairly frequently", is per minute reasonable?

David Lang

On Sun, 8 Feb 2015, Dave Taht wrote:

> I am very interested in per sta stats - rc_stats - captured fairly
> frequently - timestamped and kept on per mac order..
>
> cat /sys/kernel/debug/ieee80211/phy*/netdev:*/stations/*/rc_stats
>
> you might also get a good grip on simultaneous users and on user
> migration by using this.
>
> also I have found the xmit stat to be useful.
>
>
>
>
> On Sun, Feb 8, 2015 at 3:02 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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