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The "Thin" Access Point Approach

By Jim Geier

http://www.wi-fiplanet.com/tutorials/article.php/3318401/The-Thin-Access-Point-Approach.htm (Back to article)

The access point (AP), which interfaces wireless client devices to a wired network, is the primary component of a wireless LAN. A company installs multiple access points to provide coverage throughout a facility, enabling users to roam. The radio card in the client device conforms to the 802.11 (Wi-Fi) standard when performing medium access functions, associating with APs, and carrying on the transfer of data packets.

Traditional APs

Most access points, especially those for enterprises, traditionally have intelligence beyond what the 802.11 standard provides. For example, an enterprise grade AP will implement advanced functions that enhance security, management, and performance. For example, an AP incorporates sophisticated access control mechanisms to afford better security than what the 802.11 standard contains.

These "thick" APs (or "fat" or "smart" APs, depending all upon your point of view) tie to conventional Ethernet switches in an enterprise and provide a wireless LAN backbone infrastructure. The switches in this case don't usually have any features that enhance wireless communications -- the kind of thing that is necessary when supporting voice over wireless LANs.

These traditional enterprise grade access points are relatively expensive compared to the "thin" APs that I'll discuss below. As a result, it's costly to scale up the WLAN when installing additional APs to increase coverage or performance.

In addition, a standard AP approach is costly to migrate to newer technologies. In some cases, a company can merely upgrade the firmware of the AP to begin implementing modifications, such as using WPA The deployment of some technologies, such as AES will likely require replacing the APs (AES requires its own encryption chip). Consequently, the thick AP can be expensive to support.

Also in regards to support, APs have lots of configuration parameters that operational support software must interface with. This places a significant amount of over head traffic over the network, which can decrease available throughput for primary applications.

"Thin" Access Point Solutions

Some WLAN equipment manufacturers, such as Legra and Airespace, minimize the intelligence in the AP and centralize the intelligence of the network in the switch instead. With this approach, relatively simple APs can share the features that enhance wireless communications in a cost-effective and efficient manner.

Because the thin APs don't implement much more than the 802.11 standard, they generally cost less. This can reduce the total cost of ownership (TCO) of a WLAN because of less expensive upgrades and migration to future technologies.

Much of the configuration is centralized in the wireless switch, which reduces management functions from operating over the WLAN. An administrator can interface directly with the switch from the more familiar wired side of the network. The central nature of the switch makes it an excellent platform for managing the network.

In addition, the wireless switch optimizes performance. Roaming handoffs are much faster than with conventional switches, which makes it more practical to effectively support voice over wireless solutions.

Final Thoughts

If you're deploying a enterprise-class WLAN, strongly consider the use of the "thin" AP solution that makes use of a wireless switch that enhances operation. Before making a decision, though, compare the total costs of both approaches. Don't forget to factor in changes that will likely need to occur to network in the future. A very high percentage of companies expand their network once requirements are better understood. With that in mind, the "thin" access point solution shines.

Jim Geier provides independent consulting services to companies developing and deploying wireless network solutions. He is the author of the book, Wireless LANs and offers training focusing on wireless LANs.