What is Beacon and who send it

Beacons :

• Used by the WLAN network to advertise its presence. 

• beacons are regularly broadcast by an AP 
• AP sends the probe, authentication, and association frames only during the association and re-association process. 
• Beacon Frame Contains
• SSID 
• BSSID
• Channel Supported 
• Security Type supported
• Typically, APs transmit beacon frames every 100ms.