802.11 Simple authentication process

Brief process:

STA send probe FRAME-"AP response probe frame and associated-" STA received a response sent 802.11 low-level Authentication-"AP received authentication Response-" STA selected AP Association-"AP Associated reply-" began transmitting data. If security is set, wpa/wpa2/802.1x authentication may be required to send data.

Detailed process:

1. The user (Sta) sends a probe request to discover a 802.11 network in its vicinity. Probe request broadcast Mobile station supported data rate and 802.11 capabilities, such as 802.11n. Because the probe request is sent from the mobile station to the destination two-tier address and to the bssid of the FF:FF:FF:FF:FF:FF:FF, all APs that receive it will respond.

2. Receive the AP check of the probe request to see if the mobile station has at least one publicly supported data rate. If they have a compatible data rate, send probe responses, advertise the SSID (wireless network name), support the data rate, if required encryption type, and other 802.11 capabilities of the AP. The mobile station chooses a compatible network from the probe response it receives. Compatibility can be based on encryption types. Once a compatible network is found, the mobile station will attempt a low-level 802.11 authentication with a compatible AP. keep in mind that 802.11 authentication differs from the WPA2 or 802.1X authentication mechanism, which occurs after the mobile station is authenticated and associated. The original 802.11 authentication frames were designed for WEP encryption, but this security scheme has proven to be unsafe and therefore not recommended. Since this 802.11 authentication frame is open, almost always succeeds.

3. The mobile station sends a low level 802.11 authentication frame to the AP, opens the authentication and sets the sequence to 0x0001.
4. The AP receives the authentication frame and responds to the mobile station using the authentication frame set to open, indicating the sequence of the 0x0002.
If the AP receives any frame other than an authentication or probe request from an unauthenticated mobile station, it responds with the de-authentication frame and places the mobile station in an unauthenticated, non-associative state. The station will have to start the association process from the low level authentication step. At this point, the mobile station is certified but not yet associated. Some 802.11 capabilities allow a mobile station to perform low-level authentication on multiple APS. This accelerates the association process when moving between APs. A mobile station can be 802.11 authenticated to multiple APs, however it is only actively correlated and transmits data through a single AP at a time.
5. Once the mobile station determines which AP it wants to associate to, it sends an associated request to that AP. The association request contains the encryption type selected (if required) and other compatible 802.11 capabilities.
If the AP receives a frame from a certified but not yet associated mobile station, it responds with a detached frame, placing the mobile station in an authenticated but not associated state.
6. If the element in the associated request matches the ability of the AP, the AP creates an association ID for the mobile station and responds with an associated response that grants a successful message to the network access to the mobile station.
7. The mobile station is now successfully associated to the AP, and the data transfer can begin.
Note: If WPA/WPA2 or 802.1X authentication is required on the wireless network, the mobile station will not be able to send data until the 802.11 association is complete, until dynamic keys and authentication are performed.

802.11 Simple authentication process