The original IEEE 802.11 standards were fashioned with single access points (APs), but that is not the case in offices, where multiple APs are required. In this new standard, devices are designed to jump from one AP to another very swiftly compared to the earlier standard. 802.11r minimizes handoff delays linked with 802.1X authentication by reducing the time taken to re-establish connectivity after a client moves between 802.11 APs while roaming.
The 802.11r have included typical QoS mechanisms, such as packet prioritization and call admission control (CAC), to enhance the operation of real-time voice applications. Using three MAC-layer enhancements, the standard was able to lower the handoff time, but at the same time maintains high levels of security.
The first of the three enhancements was the elimination of the 802.1X key exchange because it was not required during handoffs between APs within the same “mobility domain.” A mobility domain is a set of APs built to execute fast transitions between them.
The second improvement was the addition of a four-way handshake. This was essential for session key establishment and was also integrated in the previously active 802.11 authentication/association messages. This reduced the delay after re-association pending the completion of the security negotiation and allowed data transmissions to resume faster. The final enhancement packages all call resource requests into new authentication messages exchanged before the re-association.
Until recently, vendors 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 keep the rest of the network protected. Vendors such as Meru and Extricom have built networks with no roaming, as all their APs are placed on the same channel.
The Wi-Fi Alliance released a new VoIP brand known as Wi-Fi Certified Voice-Personal in June but has had limited success. The Alliance is looking forward to coming up with a new Voice-Enterprise brand, which will include the 802.11r standard, in 2009. “[Voice-Personal certification] is for low range stuff and SME equipment,” said Alistair Mutch, who is the development director for Wi-Fi switch vendor, Trapeze. “We have not submitted to the low end one as we felt it was really not worth it.”. IEEE 802.11r could open up a bottle-neck in enterprise Wi-Fi VoIP installations and should allow VoIP certification to move ahead.
TFOT has previously written about the Wi-Fi detector shirt that can help you detect the all-important hotspots while you walk along the street. You can also check out our article about Wi-Fisharing technology developed where a single wireless network is split into two completely separated ones, like a personal hotspot and AutonetCar WIFI where Autonet Mobile, a California based company, claims to be the first company that will allow a 24/7 broadband internet connection in your car.
Additional information on IEEE 802.11r standard can be obtained on the IEEE website.