Wireless Fast BSS Transition
Fast BSS Transition describes mechanisms by which a mobile device can reestablish existing security and QoS parameters prior to reassociating to a new AP when roaming. These mechanisms are referred to as “fast” because they can significantly reduce the length of time that connectivity is interrupted between a mobile device and Wi-Fi infrastructure when that mobile device is connecting to a new AP.
The protocols used by Fast BSS Transitioning apply to wireless client transitions between APs within the same ESS. Since both reassociation and reauthentication are time-consuming processes, removing the associated message exchanges between wireless client and the infrastructure help reduce interruption to time-sensitive services such as VoIP and video when transitioning from one AP to another especially in a highly secure WLAN.
IEEE 802.11r defines these mechanisms to allow for the fast transitioning of wireless clients.