Chapter 18: The Access Point

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Overview

The deployment of a wireless local area network (WLAN) requires very little hardware. An ad hoc network only needs two computing devices, each equipped with a wireless network interface card (NIC). Add an access point (AP), and a bit of cabling, and you have a simple wireless infrastructure setup. Even a corporate WLAN, which may need sophisticated antenna equipment or an additional "box" here and there, still has the access point as its centerpiece.

However, as with many things in life, when the needs are few, sometimes making the right choice can be difficult. Only the WLAN deployment team knows which of the following components (including their various permutations) are necessary in order for the users of a specific WLAN to obtain an optimal wireless networking experience.

Selecting access points for deployment within a corporate WLAN system is complex. These devices, which are about the size of the typical office telephone, provide a wireless interface to the client devices and a wireline to the LAN. Up until the year 2002 or so, the technical differences between various vendors' access point products were minor. That's all changed. Today, access points run the gamut, including the following:

• Simple RF receivers.

• Sophisticated devices that provide RF excellence.

• Intelligent instruments that not only offer great RF transmission and reception, but also can connect two network segments and keep traffic local by filtering traffic based on MAC addresses—allowing access when necessary to other parts of the network (akin to a Layer 2 bridge).

• Smart tools that can perform, in addition to bridging between wired and wireless networks, higher functions that are normally reserved for routers or switches in wired networks. For example, in 802.11 (a, b or g) networks, some of these intelligent devices can function as network access servers.

Note that the latter two types of access points may lock you into a specific vendor solution, because these devices offer functions that fall outside the province of the 802.11 series. For instance, products that offer functionalities, such as special security or management features, are provided via proprietary solutions.

Access points that function only as RF receivers are sometimes referred to as "thin" or "dumb" APs, especially if they are offered along with some kind of "intelligent box" that feeds these APs with any "smarts" they might need. Access points that perform more exhaustive tasks, e.g. user authentication, are referred to as "fit," "fat," "smart," or "intelligent" APs. These devices may or may not work in tandem with some kind of intelligent box.

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