In the wired world, to connect to the network you would plug in your Ethernet cable into the switch. In the wifi world, you must connect to the access point. The process of connecting to an access point is called the 802.11 State Machine.
How does the station (STA) and access point agree to this connection?
I’m going to attempt to break it down step-by-step on this post.
802.11 State Machine
In my example, I have one STA connecting to an open SSID. The summary of it all is as follows:
- STA is unauthenticated and unassociated
- STA becomes authenticated and unassociated
- STA becomes authenticated and associated
- STA clears security requirements such as 802.1X, if required
The STA begins the process by performing a passive or active scan. In the passive mode, the STA is listening for beacons from an access point. The beacon frame contains the BSSID which is the MAC address of the radio sourcing from the access point.
The beacon frame is a type of management frame defined in 802.11-2007. It includes capability information and parameters.