Simple APs

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Simple APs aren't crammed with user and network configuration data, instead they are designed to concentrate on the radio functions. These devices rely on all of the necessary controlling intelligence to be provided elsewhere on the network, e.g. by an access controller, a wired switch, or even a router. These APs are usually described as being "thin," "dumb," or "lite." Whatever they are called, they range from devices that merely satisfy the 802.11 (a, b, or g) specification to sophisticated gear that offers RF excellence. Either way these simple devices cost less and need less management than their more complex counterparts—their basic radio functions are unlikely to need attention, and the security and other features that need regular attention are in the traditional location—some type of central control device, i.e. an intelligent box.

Furthermore, since these APs aren't loaded with network and user configuration data, they are of little or no interest to hackers. And if one of these simple devices is stolen, it's rendered inoperable as soon as it's unplugged.

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SOFT ACCESS POINTS

Some vendors offer software that, when loaded onto a computing device that is connected to a wired LAN, enables the computing device to act as a hardware access point. These software products are reminiscent of the old Winmodem software, in that they use the computing device's CPU to process the data flow. For example, a laptop can be easily configured to function as an AP with commonly available software, such as the freeware tool Host AP for Linux systems, or PCTEL, Inc.'s Segue SAM, a soft access point that permits Wi-Fi-enabled computing devices to function as APs.

The large vendors are also getting in on the act. Intel plans to integrate "soft access points" for wireless access into PCs. This extra software will let home laptop users connect to the Internet by using a wired home PC as a bridge. And Microsoft is supposedly hard at work on what it calls a "Soft Wi-Fi," which, according to Microsoft's press relations services, is a new driver model. The Soft Wi-Fi will allow processing currently done by the 25 MHz chip used by hardware-based access points to be performed within Windows. Thus, according to Microsoft, any Windows-based PC can function as an access point.

Beware, though, that when soft APs are used within a corporate networking system, it is difficult for the IT department to keep track of them because the soft AP appears as an authorized station to all wire-side network scans.

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Vendors such as Aruba, Proxim, and Symbol advocate the simple AP/intelligent box approach. There is some logic to using one of their solutions:

  • In many enterprise-sized networks, APs are deployed in volume, so per-access point savings add up as the wireless network size increases.

  • Bundling software intelligence into an access controller or switch device (instead of distributing it out to the access points) enables the IT department to make upgrades and changes to only one device—the smart one—rather than on a per-access point basis.

  • It is perfect for campus environments, which require a lot of access points, because it can inexpensively increase wireless coverage.

But the downside to designing a WLAN around the AP/intelligent box approach is that the APs must be able to contact the intelligent box. Oft-times that box is located somewhere within the wired network environment, thus packets of data are required to go through twice as many plug devices before they get to the end-user. As illustration, data is transferred from the LAN switch, to the WLAN intelligent box, to the LAN switch, and then to the simple access point. Whereas, in a WLAN designed around smart APs, the data is transferred directly from LAN switch to AP.

Richard Bravman, CEO of Symbol Technologies, believes that the use of catchall switching in combination with simple access points will dominate the next generation of WLAN technology. "We have put all the essential capabilities into one system," says Bravman, "so that organizations no longer need to buy separate pieces from multiple vendors, or costly pieces from one vendor, to achieve secure application-specific wireless networking."

Symbol's Mobius Axon Wireless switch offers Layer 2 and 3 WLAN functions (e.g. IP inspection and load balancing), and certain Layer 4 features (e.g. HTTP, instant messaging, and security solutions such as Kerberos authentication). The layers are managed by an XML or command line interface. The switch is paired with Mobius' "thin" APs. The MAC software layer has been taken out of these APs and put into the wireless switch, leaving only the Physical Layer for the AP. This arrangement allows the Mobius APs to act simply like an Ethernet port—a wireless socket through which data packets are passed.

Let's now look at what a smart AP has to offer. (There is more on intelligent boxes later in this chapter.)



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Going Wi-Fi. A Practical Guide to Planning and Building an 802.11 Network
Going Wi-Fi: A Practical Guide to Planning and Building an 802.11 Network
ISBN: 1578203015
EAN: 2147483647
Year: 2003
Pages: 273

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