The "enterprise" in "enterprise Wi-Fi scalability" implies a larger system than a handful of access points, each supporting a few clients. Accordingly, we asked each participating vendor to supply 25 access points, at least two controllers and/or switches with enough ports for all the access points, plus power over Ethernet for the access points.

We assessed enterprise Wi-Fi scalability using five sets of tests: throughput, latency, VoIP call capacity, and single- and multiclient roaming. The test instrument for this project was the VeriWave WT-90, a new chassis-based system that can concurrently emulate hundreds of clients associated with dozens of access points. VeriWave custom-developed a new suite of tests especially for this project.

Click to see: Aruba 6000

For the test bed, we used three WT-90 chassis, collectively equipped with one Gigabit Ethernet port and 25 802.11b/g test ports (the WT-90s also support 802.11a, which we did not use in this test).

To reduce interference and ensure greater repeatability, we placed each of the 25 access points in its own RF-shielded enclosure to reduce interference and also connected access points to the test instruments using cable instead of sending signals over the air. We also used attenuators to keep signal levels in the 30- to 40-dBm range.

To measure throughput, a VeriWave script emulated 20 clients associating with one access point, authenticating using 802.1X from a RADIUS server; and obtaining IP addresses from a DHCP server. The script then offered test traffic from the Gigabit Ethernet port destined for all 20 clients. Using a binary search algorithm, the script determined the highest offered load with no more than 0.1% frame loss. (To understand why we used 0.1% acceptable loss instead of the standard 0% loss, see "Breaking the standards.") The script determined the throughput rate for 88-, 512- and 1,518-byte frames (as measured on the Ethernet side).