Luke Pensworth
The IEEE has completed 802.11r, a standard that lets Wi-Fi devices roam quickly between access points, improving the performance of VoIP on enterprise LANs.
The IEEE 802.11 standards were originally defined with single access points in mind. But when devices move from one access point to another, it takes around 100ms to re-associate, and several seconds to re-establish authenticated connections using 802.1x. That will drop a voice call.
The new standard, IEEE 802.11r (Wikipedia), is also known as Fast Basic Service Set Transition. It allows the network to establish a security and QoS state for the device at the new access point, before it roams between the two, so the transition can take place in less than 50ms – the standard required for voice roaming.
The IEEE has been working on 802.11r for four years, and the concept has been solid since 2005, but the standard was formally approved and published by the IEEE this summer. The 802.11r standard will govern the way roaming mobile clients communicate with access points, establish security associations and reserve QoS resources. Under 802.11r, clients can use the current access point as a conduit to other access points, allowing clients to minimize disruptions caused by changing channels.
