hostapd-1-rc3: Wireless lags and unstable connection

Valeriy Kucherenko darkside_ua at ukr.net
Thu Apr 26 08:58:53 EDT 2012


> 2012/4/26 Valeriy Kucherenko <darkside_ua at ukr.net>:
> >
> >
> > Hi.
> >
> > I'm currently using hostapd-1-rc3 and have noticed periodic connection lags that causes problems when, for example, playing online games or listening to streaming music.
> > Here is a part of ping output (from AP to wireless client) when the lag appears:
> >
> > 64 bytes from 192.168.0.5: icmp_req=869 ttl=128 time=2.38 ms
> > 64 bytes from 192.168.0.5: icmp_req=870 ttl=128 time=6.79 ms
> > 64 bytes from 192.168.0.5: icmp_req=871 ttl=128 time=3059 ms  <-- here it is
> > 64 bytes from 192.168.0.5: icmp_req=872 ttl=128 time=2053 ms
> > 64 bytes from 192.168.0.5: icmp_req=873 ttl=128 time=1046 ms
> > 64 bytes from 192.168.0.5: icmp_req=874 ttl=128 time=38.9 ms
> > 64 bytes from 192.168.0.5: icmp_req=875 ttl=128 time=4.51 ms
> > 64 bytes from 192.168.0.5: icmp_req=876 ttl=128 time=5.90 ms
> >
> > These lags occurs approximately each 10 minutes and I'm guess that the problem in WPA group rekeing routine (I have set wpa_group_rekey=600 in my config).
> 
> Could you try and play around with that setting (like setting it to
> 150 and 300, and see if the problem happens with 2,5 and 5 minute
> intervals?

Changed to 60 - first huge ping spikes (6 seconds in sum) appeared on 12 minute after that ~15 minutes work with little spikes. Stopped.
Changed to 150 - checked 30 minutes - little ping spikes each 1 min 10 sec. Stopped.
Changed to 300 - checked 30 minutes - little ping spikes each 1 min 10 sec. Stopped.
Changed again to 600 - checking now - little ping spikes each 1 min 10 sec.

I have made some observation on those ping spikes:

Time: 15:26:45
64 bytes from 192.168.0.5: icmp_req=2249 ttl=128 time=3.78 ms
64 bytes from 192.168.0.5: icmp_req=2250 ttl=128 time=112 ms
64 bytes from 192.168.0.5: icmp_req=2251 ttl=128 time=95.5 ms
64 bytes from 192.168.0.5: icmp_req=2252 ttl=128 time=597 ms
64 bytes from 192.168.0.5: icmp_req=2253 ttl=128 time=3.27 ms

Time: 15:27:55
64 bytes from 192.168.0.5: icmp_req=2319 ttl=128 time=57.1 ms
64 bytes from 192.168.0.5: icmp_req=2320 ttl=128 time=40.6 ms
64 bytes from 192.168.0.5: icmp_req=2321 ttl=128 time=24.5 ms
64 bytes from 192.168.0.5: icmp_req=2322 ttl=128 time=118 ms
64 bytes from 192.168.0.5: icmp_req=2323 ttl=128 time=4.37 ms

Time: 15:29:05
64 bytes from 192.168.0.5: icmp_req=8 ttl=128 time=4.54 ms
64 bytes from 192.168.0.5: icmp_req=9 ttl=128 time=44.2 ms
64 bytes from 192.168.0.5: icmp_req=10 ttl=128 time=26.6 ms
64 bytes from 192.168.0.5: icmp_req=11 ttl=128 time=11.7 ms
64 bytes from 192.168.0.5: icmp_req=12 ttl=128 time=3.71 ms

Time: 15:30:15
64 bytes from 192.168.0.5: icmp_req=75 ttl=128 time=4.12 ms
64 bytes from 192.168.0.5: icmp_req=76 ttl=128 time=127 ms
64 bytes from 192.168.0.5: icmp_req=77 ttl=128 time=5.41 ms
64 bytes from 192.168.0.5: icmp_req=78 ttl=128 time=4.54 ms

Time: 15:31:25
64 bytes from 192.168.0.5: icmp_req=146 ttl=128 time=3.59 ms
64 bytes from 192.168.0.5: icmp_req=147 ttl=128 time=94.9 ms
64 bytes from 192.168.0.5: icmp_req=148 ttl=128 time=82.3 ms
64 bytes from 192.168.0.5: icmp_req=149 ttl=128 time=62.9 ms
64 bytes from 192.168.0.5: icmp_req=150 ttl=128 time=4.11 ms

Time: 15:32:35
64 bytes from 192.168.0.5: icmp_req=217 ttl=128 time=4.16 ms
64 bytes from 192.168.0.5: icmp_req=218 ttl=128 time=38.5 ms
64 bytes from 192.168.0.5: icmp_req=219 ttl=128 time=21.5 ms
64 bytes from 192.168.0.5: icmp_req=220 ttl=128 time=119 ms
64 bytes from 192.168.0.5: icmp_req=221 ttl=128 time=92.8 ms
64 bytes from 192.168.0.5: icmp_req=222 ttl=128 time=4.00 ms

So, as you can see spikes appears each 1 minute 10 seconds and not depends on wpa_group_rekey param. My average normal ping is 3-4ms. Debug output does not contains anything unusual but annoying "mgmt::action cb".
What else I can investigate to localize this issue?

> 
> Would help pinpoint what is causing it.
> 
> Also, did it happen in rc2?

I have noticed this a long time ago, when hostapd-1 branch even was not exist, but did not make any importance to this.

> 
> /Bjarke
> 


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