There are three main configurations of wireless local area networks (WLANs): basic service set (BSS), extended service set (ESS), and independent basic service set (IBSS). A BSS uses a single access point, while an ESS connects multiple BSSs for wider coverage. An IBSS does not use an access point and allows devices to connect directly. Authentication is required to join a network, with open system requiring only an ID and shared key using a secret key. 802.1x authentication improves security over 802.11 by adding computer and user identification, dynamic key creation, and centralized authentication.