On Sun, 8 Feb 2015, Dave Taht wrote:

On Sun, Feb 8, 2015 at 3:48 PM, David Lang <[email protected]> wrote:
when you say "fairly frequently", is per minute reasonable?

every 10 sec is easier to deal with. note the cat method I showed is
inefficient.

I had been thinking in terms of feeding them to syslog for transport and timestamping (I haven't looked to see how much data is in each file)

unless these files are lengthy, gathering a couple thousand copies every 10 sec sounds reasonable (if they are long, but short lines, we can re-write them to fewer, longer lines to make it reasonable), especially if we allow this to run with no attempt to sync the runs precisely across APs (so that they do end up being pretty spread out across the time)

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.

we have already been running a per-min job to get the count of connected simultaneous users on each ESSID and logging each connection. We haven't done much analysis of the data afterwords yet.

David Lang


also I have found the xmit stat to be useful.




On Sun, Feb 8, 2015 at 3:02 PM, David Lang <[email protected]> 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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