Multicast with Linksys PCI WMP11 AP and PCMCIA WPC 11 ver 3

Jouni Malinen jkmaline at cc.hut.fi
Fri Nov 29 11:45:38 EST 2002


On Wed, Nov 27, 2002 at 10:10:14AM -0500, Bichot Guillaume (Princeton) wrote:

> I'm making some measurement in multicast/broadcast mode having one server
> sending some multicast UDP traffic through a Linksys WMP 11 PCI - Hostap -
> AP. The client is either the ipaq 3850 under Familiar 0.5.3 or a laptop
> under Linux redhat 8.0. Both uses a Linksys WPC 11 PCMCIA card (manfid
> 0x274, 0x1613). 
> 
> With the ipaq:
> The hostap driver simply does not work with the linksys card (it supposed to
> work with this card). I got the following error:
> hostap_cs: card initialization timed out
> Hostap_cs: initialization failed

Does the same linksys card work in the laptop? Linksys WPC11 Ver3 should
work fine with Host AP driver, but I have not tested the latest version
of the driver with ARM platform. Do you see any other error messages in
the kernel log ('dmesg')?

> 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.

> I've tried the iwpriv command to decrease the beacon period but I got the
> following: 
> 
> # iwpriv wlan0 prism2_param wlan0 beacon_int 1
> # Interface doesn't accept private ioctl 
> # prism2_param (8BE0): Operation not supported

That command is not correct. It should be either 'iwpriv wlan0
beacon_int #' or 'prism2_param wlan0 beacon_int #' (if
iwpriv/wireless_ext does not support extended iwpriv commands). In
addition, you should note that setting beacon interval to 1 would mean
that the AP would be sending about 1000 beacons per second in addition
to all other traffic and that might already be enough to prevent
association..

-- 
Jouni Malinen                                            PGP id EFC895FA



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