It's been a long time coming, but industry support for standards-based fast roaming is finally starting to emerge! See my previous posts:
Apple iOS now officially supports IEEE 802.11r and 802.11k, which form the underpinnings of the Wi-Fi Alliance Voice Enterprise certification for fast roaming. (Don't be confused by the word voice in the certification. This is applicable to any WiFi client that needs fast roaming capability at the driver level for any application.)
This will help Apple mobile devices perform better in enterprise environments, especially when multimedia and collaboration tools are used with BYOD.
From Apple's website:
"iOS 6 introduces support for optimized client roaming on enterprise Wi-Fi networks. The 802.11 Working Group standards k and r were conceived to give wireless clients the ability to more seamlessly roam from access point (AP) to access point within the same network.
802.11k allows an iOS 6 device to quickly identify nearby APs that are available for roaming. When the signal strength of the current AP weakens and the iOS device needs to roam to a new AP, it will already know the best candidate AP with which to connect.
When an iOS 6 device roams from one AP to another on the same network, 802.11r streamlines the authentication process using a feature called Fast Basic Service Set Transition (FT). FT allows iOS 6 devices to associate with APs more quickly. Depending on your Wi-Fi hardware vendor, FT can work with both preshared key (PSK) and 802.1X authentication methods.
Coupled with 802.11k's ability to quickly identify the target AP, FT's faster association method may enhance application performance and aims to provide a better Wi-Fi experience in iOS.
Not every Wi-Fi network hardware vendor currently supports 802.11k and 802.11r. Check with the manufacturer of your Wi-Fi hardware (controllers and APs) to determine if support is available. Once support for both standards is verified, 802.11k and FT functionality must be enabled. Setup methods vary; please consult the current configuration documentation for your Wi-Fi hardware for details."