Summary: The beacon frame is used by access points, and stations in an IBSS, to communicate their characteristics for connection. A beacon frame is sent periodically, called the target beacon transmission time (TBTT). Default time is 102,400 microseconds (102 ms). 100 time units (TUs) is 1,024 microseconds.<br> APs also contend for airtime while sending beacon frames. If the network is busy when an AP wants to send a beacon frame, then the AP will delay the beacon transmission.<br> Stations use access point beacons as a time reference for each beacon has a time stamp and an indication of when the next beacon will be sent. A station will use use the time stamp to make sure their clock uses the same tempo as the access point. This is called the timing synchronization function (TSF).<br> In an IBSS, the first station to create the ad hoc network defines the beacon interval and all stations joining the IBSS learn this interval.<br> To see an example beacon frame, <a href="https://drive.google.com/open?id=0Byy5C2VG_aFdWVJ1Rmt4UXY5RFk">download my pcap</a> file captured from my laptop.<br> Links and Resources<br> <br> * <a href="http://www.cleartosend.net/28">CTS 028: Management Frames</a><br> * Wireshark Display Filters via <a href="http://www.semfionetworks.com/blog/wireshark-most-common-80211-filters">SemfioNetworks</a><br> <br>
