A beacon message is a periodically transmitted 802.11 management frame that advertises an access point’s basic service set (BSS). Clients can discover nearby APs by listening for beacons, a process called passive scanning. section 19.1.2 section 19.3
Beacon-based discovery has these operational characteristics:
- Passive scanning can conserve client battery life but may take longer than active scanning with probe requests and responses. section 19.1.2
- Discovering an AP does not authorize data transfer; the client must authenticate and associate before sending or receiving wireless traffic. section 19.1.2 section 19.3
Wi-Fi discovery
When a phone displays unfamiliar SSIDs at a café or in a neighboring home, it may have discovered APs by receiving their beacons. section 19.1.2
Figure 19.3 The client association process. The probe request/response exchange allows PC1 to discover AP1. PC1 then authenticates and associates with AP1.
Trace beacon-based discovery alongside probe exchange, authentication, and association in the client association process. section 19.1.2
