Prioritizing authentication pkts & resending failed EAPOL pkts?

Jouni Malinen j
Thu Feb 3 16:56:22 PST 2011

On Thu, Feb 03, 2011 at 03:13:11PM -0800, Ben Greear wrote:
> Ok.  I saw those ack=0 messages, and then very shortly after the
> 4-way auth failed because sm->TimeoutCtr > dot11RSNAConfigPairwiseUpdateCount.
> dot11RSNAConfigPairwiseUpdateCount is 4 on my system.  I assumed that
> the lack of ack was directly responsible..but maybe it's just a symptom.

Difficult to say.. The frames should get acknowledgments assuming you
have reasonable connection between the devices and not too much
interference. With the four upper layer retries and maybe seven or so
low-level retries for each of those, there should certainly be large
enough number of attempts. If there were 100 real radios competing for
the chance of sending the frames at the very same moment, I would not be
surprised of issues, but in your test setup, there is not really more
than two radios competing for TX..

> Seems that 80 stations do's only when I get up above 100 that
> I have troubles..and it seems that HT40 cause more problems than
> when I'm using HT20.

What kind of CPU load are you seeing on the station and AP? 100
concurrent 4-way handshakes does not sound too much for a modern CPU,
but you may start hitting some timeouts with too many handshakes being
tried at the same time. There can be pretty tight time limits on the
4-way handshake with some APs. Though, if you are using hostapd on the
AP, it tries to be a bit friendlier in this area. HT40 vs. HT20
differences would point towards a lower level issue (and another mailing
list ;-), though.

> I believe I'm using pretty standard auth/encryption, but could
> be wrong about that:

That doesn't look too bad. It sounds like there is either a major loss
of frames or you are simply running out of a resource of some sort (CPU,
bandwidth, packets per second, etc.).

Jouni Malinen                                            PGP id EFC895FA

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