When I have conversations with network managers about whether they plan to upgrade to 802.11n wireless LAN technology, many say they’re in no hurry. They’re still getting plenty out of their existing 802.11a/b/g infrastructure, they say. And besides, all the legacy clients in their organization would just slow down the 802.11n clients, preventing users from enjoying the benefits of a faster wireless network. Access points are usually shared by multiple clients and clients can only transmit to an access point one at a time. This often means that faster 802.11n clients are stuck in a queue behind slower legacy clients that take much longer to transmit the same amount of data.
Several WLAN vendors, such as Meru Networks and Aruba Networks, have developed technologies to solve this problem. For instance, Aruba’s Adaptive Radio Management software can shift WLAN clients to different radio frequencies and can analyze the 802.11x protocol used by the client. If the client is a faster 802.11n device, the software gives it priority
Aerohive Networks, a start-up known for its controllerless WLAN architecture, has found a new way to tackle this problem. In the latest version of its operating system, HiveOS 3.2, Aerohive has introduced a new feature called Dynamic Airtime Scheduling. Rather than making airtime decisions based on protocol, Aerohive actually examines the airtime of the client’s packets to determine how fast it is. This is relevant because the farther a client is from an access point, the slower its transmission. So an 802.11n client which is much farther away from an access point than 802.11g client is could actually be slower. The Aerohive AP will give priority to the .11g client since its signal is closer and thus faster. With this technology, Aerohive can also give priority to a fast 802.11n client over a slower 802.11n client.
Dynamic Airtime Scheduling also applies policy to the clients as well. For instance, a company can give airtime priority to employee devices over guest devices,
Niall Pariag, senior network administrator at Riverside Health Care Systems Inc., a network of hospitals and clinics based in Yonkers, N.Y., is in the process of replacing legacy Cisco infrastructure in his facilities with Aerohive 802.11n access points. He said Dynamic Airtime Scheduling solves a problem he’s been worried about ever since he decided to upgrade to 801.11n.
“It solves the only quirk we had with the wireless network, that slow clients basically slow down fast clients,” he said. “That’s a concern we kept ignoring, because we knew we were going to cross that bridge when we got to it. We don’t have that many clients connecting now, so it wasn’t a concern.”
Pariag said that in the future his company will be adding more and more clients to the wireless network, and airtime scheduling will become critical to him.