Open authentication means that the AP allows any wireless client to associate. In other words, all clients are in a state of "assoc" if you do a show dot11 assoc in a telnet session to the AP.
If you do not enable WEP encryption, all wireless client can communicate with the AP without problem. (i.e. click on "SECURITY" in GUI, click on "Encryption Manager" and select "None") No one wants to make the AP wide open. Thus, most users enable static WEP. (i.e. In Encryption Manager, make "WEP" as mandatory and configure at least one WEP key) If you do that, all wireless clients are still able to associate. When wireless clients try to transmit frames to the AP, they use the static WEP key CONFIGURED ON THE WIRELESS CLIENT to encrypt the frames. When the AP receive the frames, the AP uses its configured WEP key to decrypt the frames. If the WEP key on the wireless clients and the AP do not match, the AP is unable to decrypt the frames. Thus, the AP drops the frames. Similarly, wireless clients drop the frames from the AP if the static WEP key do not match.
