Wireless LAN

An enterprise wireless local area network infrastructure typically consists of two products. First, the access point anchors radio connections via the IEEE 802.11 wireless LAN standards to clients, such as notebooks, VoIP phones or PDAs. Second, connected via Ethernet cable to the access point is a controller, which combines the functions of a standard LAN switch with an array of services to handle the networking challenges created when the client can move at whim and connect anywhere.

This centralized, controller-based WLAN architecture has become the current dominant model for most medium- to large-scale wireless deployments. The "thin" or "dependant access points require the presence of the controller (unlike the older generation of "autonomous" or "thick" APs). It's the controller that handles mobility tasks, such as assigning or preserving IP addresses for a moving client and maintaining security credentials and authorizations.

But other architectures are possible. Some vendors bundle groups of access points together with the controller, or push some or nearly all of the controller functions to the "edge" of the wireless net to be handled by the access points, or incorporate mesh routing protocols so wireless traffic can hop from AP to AP.

While today's WLANs are mainly independent "overlay" nets, with separate networking hardware, equipment vendors are looking at new chips and software that will let them embed the controller functions into a new generation of access layer Ethernet switches.

The wireless connection itself is based on the IEEE 802.11 standards, a continually evolving group of protocols that cover not only the physical layer - 802.11bg, 11a, and now 11n - but also security (802.11i), and quality of service (802.11e). In the future, standards like 802.11k and 802.11v will give APs more information about and more control over client connections, to optimize overall WLAN performance.

Access points implementing the 802.11n high-throughput standard are just now emerging (in late 2007) for the enterprise, with each radio capable of 300Mbps data rate and throughput up to130-150Mbps. Just as important is the greater reliability and consistency of the 802.11n radio signal. These changes create the possibility that wireless can become the primary means of access to the corporate net.

Additional resources

Definition: Wireless LAN security

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