This is a setting you’ll want to make sure is checked on newer Cisco controllers in environments where clients may roam during voice/video sessions.  Without it, some clients will drop 2-3 seconds with roaming between APs.  It’s set at the WLAN level.

Wireless Fast Transition Option

This is a very important non-default configuration setting to enable on Cisco Wireless Controllers hosting Mac clients.  Without it, clients may fail to associate when changing to a different wifi network.

Find it in the GUI under Controller -> General.

iPad / iPhone SSID change issue