Building Blocks: Joining a Wireless LAN

A station that wants to join a WLAN must first determine that a WLAN is present. This is accomplished either passively (by listening for a Beacon, a type of management frame that is sent by the AP), or actively (by transmitting a Probe Request on all available channels, until a Probe Response is received from the AP). The Beacon and Probe are two types of management frames, which along with Control and Data frames define the existing types of WLAN frames. Once it has determined that a WLAN is present, it must use local configuration to decide if it should join this WLAN.

In many WLAN clients, the user is asked to statically specify the SSID of the local WLAN; when a user of a product with such a driver ...

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