Time to make Wi-Fi deterministic

One of last week's newsletters talked about a way to benchmark, at scale, what sort of real-world user experience your 802.11n Wi-Fi implementations will deliver before you make huge infrastructure investments. Also important is to then continuously monitor each device's actual performance so you can deliver consistent, deterministic user experiences that are reminiscent of Ethernet.

Wi-Fi start-up Aerohive Networks says it has upgraded its AP operating system and management software to do just that: to establish, monitor and deliver service-level agreements (SLAs) for throughput on a per-client basis.

With Performance Sentinel and Airtime Boost features in HiveOS 3.4 and HiveManager 3.4 software, the company says, IT administrators can assign a minimum throughput guarantee to each 802.11n client. The system then monitors client compliance with these throughput levels and, if it falls below its minimum, takes action to remedy the situation with the boost feature.

"The SLA feature should allow us to know how the network is actually performing," says Norman Elton, a network engineer in the IT group at the College of William & Mary, an Aerohive shop in Williamsburg, Va.

"Once we have some baseline data, we hope to be able to better guarantee services by enabling the 'boost' functionality. For instance, faculty in a classroom … may need higher availability than students, while a slow client in a dorm still deserves network services. The same could be said for wireless ticket scanners at an athletic event. If they are overwhelmed by Web surfers, tickets could not be processed."

Elton draws a distinction between the SLA solution and general quality of service (QoS) capabilities supported in the 802.11e standard and enhanced by a number of vendors, including Aerohive. Traditional QoS is largely about prioritizing voice packets, which is helpful, "but its effectiveness can be hard to judge," he says. By contrast, the Aerohive system will provide feedback on how every client is performing, he says, and take automatic action to keep it at its guaranteed throughput levels.

One challenge in making shared Wi-Fi LANs deterministic, in part, has been in figuring out whether a client is operating at a low throughput rate because it only has a small amount of data to send or because it's encountering congestion and is out of bandwidth, explains Adam Conway, Aerohive vice president of product management. This is where Aerohive's "secret sauce" comes in, he says.

For now, the company's Wi-Fi SLA compliance solution focuses on per-client throughput only, unlike traditional wire-line traffic management systems that control packet flows and their resources on a per-application basis. However, Stephen Philip, Aerohive VP of corporate and product marketing, hints that the company will do more with the SLA framework "to make it more intelligent with regard to traffic flows in the future."

Joanie Wexler is an independent networking technology writer/editor in Silicon Valley.