According to the 802.11 standard, each wireless access point( WAP) sends out management data packets called beacon frames at regular intervals. With such a beacon frame, the access point transmits some configuration and security information and the service set identification( SSID) to the WLAN clients.
The time interval between two consecutive beacon frames is called a beacon interval. Beacon intervals are specified in time units ( TU), where each time interval corresponds to 1,024 microseconds. The beacon period, which is the time between two beacons, normally has 100 time units and thus has 102.4 ms and a data size of 2 bytes. Incorrectly set beacon periods can result in clients being unable to associate the corresponding access point.
In each beacon period, the access point sends a Traffic Indication Message( TIM) to the WLAN stations that are in the idle state. With this TIM message, the access point indicates to the WLAN station in power-save mode that it has cached a message for it.
The Beacon Period can be increased by a multiple of 100 ms and determines how often a beacon frame contains a Delivery Traffic Indication Message( DTIM).