WEP and orinoco_cs

[David Gibson]

On Sun, May 26, 2002 at 10:40:28AM -0500, Jack wrote:
> Hi,
> 
> I'm having a lot of problems to use WEP with orinoco_cs.  Here's my
> observation:
> 
>   .  0.11b does better than the one comes with 2.4.18
> 
>   .  downloading at peak speed is fine with 0.11b (>500KB/s:)
> 
>   .  uploading at peak speed is not working at all,  it does not last
>      for a second.  Tested with Dlink 650 (fw 1.3.4) and Orinoco Silver
>      (fw 8.10)  The worst part is the failure could bring down the AP
>      and the whole wireless lan.
>        eth1: Error -110 writing Tx descriptor to BAP
> 
>   .  uploading at peak speed is OK when using Orinoco Silver with FW
>      7.52.   
>      There is one improvement,  I doubt,  causes the problem:
>          · Encrypted Frames at 11 Mbit/s are now Fragmented.
> 	   Frames to be transmitted encrypted at 11 Mbit/s are now
> 	   fragmented into fragments of maximum 540 bytes. This is a
> 	   workaround to reduce the performance impact on the AP when
> 	   multiple stations are transmitting encrypted frames at 11
> 	   Mbit/s to the AP.

Ah, ok.  This is a known problem, but we haven't figured out how to
fix it yet.  It appears that Intersil firmware (which is on the
D-Link) and Lucent firmware 8.10 (but not earlier versions) have a
peculiar behaviour when WEP is enabled.  Our theory is that while the
card firmware is encrypting a packet it doesn't respond to further
requests to write packet data to the card.  That means the card
remains busy and unresponsive for longer than we expect, so we time
out (error -110).

-- 
David Gibson			| For every complex problem there is a
david at gibson.dropbear.id.au	| solution which is simple, neat and
				| wrong.  -- H.L. Mencken
http://www.ozlabs.org/people/dgibson