IEEE 802.11r-2008 or fast BSS transition (FT), is an amendment to the IEEE 802.11 standard to permit continuous connectivity aboard wireless devices in motion, with fast and secure client transitions from one Basic Service Set (abbreviated BSS, and also known as a base station or more colloquially, an access point) to another performed in a nearly seamless manner.
However, as additional features were added to the standard, including 802.11i with 802.1X authentication and 802.11e (QoS) or Wireless Multimedia Extensions (WMM) with admission control requests, the number of messages required went up dramatically.
During the time these additional messages are being exchanged, the mobile device's traffic, including that from voice calls, cannot proceed, and the loss experienced by the user could amount to several seconds.
A fast BSS transition performs the same operations except for the 802.1X negotiation, but piggybacks the PTK and QoS admission control exchanges with the 802.11 Authentication and Reassociation messages.
On August 4, 2018, researcher Jens Steube (of Hashcat) described a new technique [3] to crack WPA2 and WPA PSK (pre-shared key) passwords that he states will likely work against all 802.11i/p/r networks with transition functions enabled.