To the N Standard — And Beyond

The Institute of Electrical and Electronics Engineers recently published the future Wi-Fi standard, 802.11r. Four years in development, this standard unravels performance challenges related to Voice over IP over Wi-Fi implemented in large-scale networks. It will let Wi-Fi devices roam rapidly among access points (APs), enhancing the operation of VoIP on enterprise LANs.

The original IEEE 802.11 standards were fashioned for single APs, but office environments require multiple APs. Devices that meet the new standard will jump from one AP to another very swiftly compared with earlier designs. 802.11r minimizes hand-off delays linked to 802.1X authentication by reducing the time it takes to re-establish connectivity when a client roams among 802.11 APs. 

The 802.11r standard includes typical quality of service (QoS) mechanisms, such as packet prioritization and call admission control (CAC), to enhance the operation of real-time voice applications. Using three Media Access Control layer enhancements, the standard is able to reduce the hand-off time while maintaining a high level of security.

The first of the three MAC-layer enhancements is elimination of the 802.1X key exchange. This is no longer required during hand-offs among APs within the same “mobility domain,” which is a set of APs built to execute fast transitions among them.

The second improvement is the addition of a four-way handshake. This is essential for session key establishment and was integrated in previously active 802.11 authentication/association messages. This reduces the delay after re-association, pending the completion of the security negotiation, and allows data transmissions to resume more quickly.

The third enhancement packages all call resource requests into new authentication messages exchanged before the re-association.

Until recently, manufacturers have implemented lower security alternatives such as Wired Equivalent Privacy (WEP) encryption on their Wi-Fi VoIP networks. They have also placed VoIP traffic on different Virtual LANs (VLANs) to protect the rest of the network. Manufacturers such as Meru and Extricom have built networks with no roaming by placing all their APs on the same channel.

Smooth Transition?

802.11r approval was much smoother than for previous standards, such as the 802.11n, which is expected to be finalized in November 2009, but many “Draft N” products are already on the market. 802.11r can potentially reach many markets, including medical and manufacturing facilities and universities, where people have to move through a large area while maintaining an online connection.

Many believe that the new standard’s true strength lies in its support for 802.1X security. Although companies such as Polycom believe that 802.11r enhanced security could lead the way to an all-wireless office in the future, implementing the new standard won’t happen overnight. It isn’t clear when we’ll see the first devices that support the new standard, but some experts have estimated it could take a full year; by that time, the 802.11n might be approved.

It remains to be seen whether the QoS and security advantages that the 802.11r protocol brings will be enough to lure manufacturers, or whether industry will wait for the next new thing.