Preauthentication

Stations must authenticate with an access point before associating with it, but nothing in 802.11 requires that authentication take place immediately before association. Stations can authenticate with several access points during the scanning process so that when association is required, the station is already authenticated. This is called preauthentication. As a result of preauthentication, stations can reassociate with access points immediately upon moving into their coverage area, rather than having to wait for the authentication exchange. In both parts of Figure 7-6, there is an extended service set composed of two access points. Only one mobile station is shown for simplicity. Assume the mobile station starts off associated with AP1 at the left side of the diagram because it was powered on in AP1's coverage area. As the mobile station moves towards the right, it must eventually associate with AP2 as it leaves AP1's coverage area