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

David Lang david at lang.hm
Sat Feb 7 22:08:21 EST 2015

I will have a handful of 'extra' 3700 APs that I could use (and on 2.4G I could 
look into bringing up some older dir-615 2.4G only APs if needed)

storage would be the issue. I can have a couple just stream over the network, 
but very many and I'll have people panicing over the thought of it possibly 
interfering with the video.

There are some privacy concerns about capturing everything, but I think we can 
get agreement given that starting last year we switched all the wifi to 
encrypted-only (metadata is still visible, so the encryption doesn't completely 
eliminate the privacy concerns, but I'm sure we can deal with the remainder on a 
case-by-case basis, possibly with some written agreement)

I hope you recover well. I want though that about a month ago.

David Lang

On Sun, 8 Feb 2015, Dave Taht wrote:

> as for more detailed info, doing a few boxes doing aircaps in monitor
> mode would be useful. I could contribute a spare laptop IF I get back
> from nz next week (I am currently flat on my back with a crippling
> attack of bronchitis and not looking forward to flying), and a few
> spare TB drives. or maybe a chrome book or three could be leveraged.
> On Sun, Feb 8, 2015 at 3:35 PM, Dave Taht <dave.taht at gmail.com> 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
>>> _______________________________________________
>>> Cerowrt-devel mailing list
>>> Cerowrt-devel at lists.bufferbloat.net
>>> https://lists.bufferbloat.net/listinfo/cerowrt-devel
>> --
>> Dave Täht
>> thttp://www.bufferbloat.net/projects/bloat/wiki/Upcoming_Talks

More information about the Cerowrt-devel mailing list