Fast Transition (FT), also known as IEEE 802.11r, is the key-caching mechanism that must be configured to speed up the reauthentication delays on the wireless infrastructure. FT allows for rapid re-authentication when roaming between access points, reducing the time required for re-establishing security keys and thus speeding up the overall process2.
References: CCNP Enterprise Wireless Design ENWLSD 300-425 and Implementation ENWLSI 300-430 Official Cert Guide Premium Edition and Practice.