management frames are lost during high load situations (REPOS T)

Bichot Guillaume Princeton BichotG
Thu Jan 9 05:45:47 PST 2003

I've got the same problem. Jouni answer was this.

> With the laptop:
> The average association time (i.e. the client detects and associates 
> with the AP)is 10 seconds between 256 Kbit/s and 1 Mbit/s. With a 
> 2Mbit/s throughput it becomes impossible to associate with the AP.

Lot of date traffic in the network will result in association problems since
most stations seem to use quite strict limits on how long time receiving of
the auth/assoc reply can take. If you upgrade your AP to use latest CVS
version, you should be able to see whether the station is acknowledging
auth/assoc replies (if not, the delay was probably too long).

At the moment, the driver does not prioritize outgoing frames at all, but I
might need to do this at some point to help association under heavy load. It
should help, if the AP would simply by-pass any outgoing queue of data
frames when sending auth/assoc replies. There can still be some frames
buffered in the wlan card, but at least the host-side queue would not be
adding latency. In addition, number of buffered frames in the wlan card
could be reduced, if needed.

Guillaume Bichot

> -----Original Message-----
> From: Pedro Estrela [mailto:pedro.estrela at] 
> Sent: Thursday, January 09, 2003 3:10 AM
> To: HostAP at
> Subject: management frames are lost during high load 
> situations (REPOST)
> Hi! I've got a problem related to management frames in high 
> load situations.
> This was already sent by me some months ago
> (
tml) and i'm hoping that now someone has any ideia of how i could give
priority to the transmission of management frames:

"Simply put, when the card is put in stress with a major downstream UDP flow
(greater than a flood ping), the AP is unable to process further
associations/reassociations. In this scenario, a station moving from one
unloaded AP to a loaded AP will keep on sending associations until the load

Pedro Estrela

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