IEEE standardizes fast Wi-Fi roaming

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 in offices multiple access points are needed. Devices can move from one access point to another, but it takes around 100ms to re-associate, and several seconds to re-establish authenticated connections using 802.1x.

The new standard, 802.11r, known as Fast Basic Service Set Transition, 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.

Till now, vendors have either used lower security options on Wi-Fi VoIP (using WEP encryption for instance) and put VoIP traffic on separate VLANs to protect the rest of the network, or implemented technology close to the eventual 802.11r standard.

Other vendors, including Meru and Extricom, has built networks where there is no roaming because all the access points are on the same channel.

IEEE 802.11r could open up a bottle-neck in enterprise Wi-Fi VoIP installations, and should allow VoIP certification to move ahead. Although the Wi-Fi Alliance, delivered a VoIP brand, known as Wi-Fi Certified Voice-Personal in June, this has had limited success, and the Alliance is expected to follow up with a Voice-Enterprise brand, including 802.11r, in 2009.

Cisco and Meru branded enterprise-grade equipment under the Voice-Personal brand, but other business Wi-Fi companies have shunned it.

"We primarily address the enterprise market, so we would certainly look for voice-enterprise when it comes out," said Roger Hockaday, Aruba's director of marketing EMEA.

"[Voice-Personal certification] is for low range stuff and SME equipment," said Alistair Mutch, worldwide business development director for Wi-Fi switch vendor Trapeze (now being acquired by Belden). "We have not submitted to the low end one as we felt it was really not worth it."

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