At the wireless edge

AS WIRELESS LANS grow in size and complexity, and IT managers wrestle with the twin burdens of staff time and security when configuring and maintaining wireless APs (access points) across their enterprises, a previously unnecessary category of network management solution has started to proliferate: the central WLAN controller.

At the same time, wireless vendors are exploring the use of XML-based protocols, peer-to-peer communications, and even radio itself to ease WLAN management. The first two of these approaches address current limitations in central controllers, whereas the third takes central control to the extreme.

Control your own

Available from established vendors such as Proxim and Cisco, and from newcomers such as Sputnik, central controllers work with the vendor's proprietary APs to aggregate the configuration, updating, and monitoring of entire WLANs. Providing configuration templates and a Web-based interface for managing groups of APs, these controllers can apply common configurations to hundreds of APs at a time, and they can reduce the time to install new APs by using network discovery to find new devices as they are plugged into the enterprise and instantly passing them a standard configuration. Controllers can also aggregate network statistics into SNMP properties used by management tools such as HP OpenView.

The central controller tries to solve what amounts to a simple problem: how to maintain the complicated authentication and security settings, as well as IP and other network details, without connecting to each AP for each change. The current crop of controllers use templating tools that allow, for instance, an updated set of WEP (Wired Equivalent Privacy) encryption keys -- for firms that use WEP as a first line of defense -- to be pushed to a manager-defined group of 500 access points with a couple of clicks.

As a result, implementing a central controller can be quite cost-effective. A single controller can typically manage as many as several hundred access points at a fixed cost that can drop below $10 per access point for large deployments. To increase reliability, some units even offer automatic failover to redundant hardware that mirrors a master controller.

One vendor taking centralized control to extremes is Holtsville, N.Y.-based Symbol Technologies. The company's recently released Mobius Axon system removes all the intelligence from access points, turning them into dumb radios connected to a central switch.

The closest similar devices from Vernier, Bluesocket, and Reefedge control aspects of network-edge issues for WLANs, but Symbol's approach moves the edge of the network entirely into the server closet by eliminating any network function from the access points.

The Mobius Axon switch manages its "access ports," as Symbol terms them, as a cloud of radio coverage. The first entry point to the network itself becomes the switch. The switch itself concentrates bandwidth.

Symbol bundles authentication and other services into the switch, but the device is limited by two load-balanced 10/100Mbps Ethernet ports even though it can support dozens of access ports. Phil Ballai, director of product marketing, says that future versions would offer Gigabit Ethernet.