![]() |
![]() |
![]() |
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
![]() |
![]() |
To access the contents, click the chapter and section titles.
Wireless Networking Handbook
Security SafeguardsWireless network vendors solve most security problems by restricting access to the data. Most products require you to establish a network access code and set the code within each workstation. A wireless station will not process the data unless its code is set to the same number as the network. Proxims RangeLAN, for example, can utilize over two billion possible network IDs. If the code is kept secret, it becomes much more difficult for someone to receive and process your data. Some vendors also offer encryption as an option. Lucents WaveLAN, for example, has two options for encryption. One version encrypts according to the Data Encryption Standard (DES) as defined by the U.S. Department of Commerce, National Institute of Standards and Technology (NIST), formerly called the National Bureau of Standards (NBS). The other version implements a proprietary method called Advanced Encryption Scheme (AES). The DES and AES algorithms use a 16-digit hexadecimal key for encryption, as shown in figure 1.11. The key is loaded into the security chip when the adapter is configured at installation. When a message is received or sent, the security chip uses the key to encrypt or decrypt the message. Only those workstations in the network with the same security chip and key will be able to understand the messages. Other users of WaveLAN who do not have the key will be unable to decrypt any messages. Both DES and AES perform the encryption in one continuous stream of bits that pass through the systems modulator without affecting performance.
The Department of Commerce limits export of DES devices outside the U.S. The purpose of the AES is to provide an alternative for DES to those users of WaveLAN needing a secure air interface, but who are not allowed to use DES due to export limitations. AES implements a proprietary algorithm that has been approved for export. Installation IssuesWith wired networks, planning the installation of cabling is fairly straightforward. You can survey the site and look for routes where installers can run the cable. You can measure the distances and quickly determine whether cable runs are possible. If some users are too far away from the network, you can design a remote networking solution or extend the length of the cable by using repeaters. Once the design is complete, installers can run the cables, and the cable plant will most likely support the transmission of data as planned. A radio-based wireless LAN installation is not as predictable. It is difficult, if not impossible, to design the wireless system by merely inspecting the facility. Predicting the way in which the contour of the building will affect the propagation of radio waves is difficult. Omnidirectional antennas propagate radio waves in all directions if nothing gets in the way. Walls, ceilings, and other obstacles attenuate the signals more in one direction than the other, and even cause some waves to change their paths of transmission. Even the opening of a bathroom door can change the propagation pattern. These events cause the actual radiation pattern to distort, taking on a jagged appearance, as shown in figure 1.12. Wireless MANs are also difficult to plan. What looks like a clear line-of-site path between two buildings separated by 1,500 feet might be cluttered with other radio transmitting devices.
To avoid installation problems, an organization should perform propagation tests to assess the coverage of the network. Neglecting to do so may leave some of the users outside of the propagation area of wireless servers and bridges. Propagation tests give you the information necessary to plan wired connections between access points, allowing coverage over applicable areas. Refer to Chapter 8 for identifying the location of access points. Health RisksAnother common concern is whether wireless networks pose any form of health risk. So far, there has been no conclusive answer. Radio-based networks, however, appear to be just as safe or safer than cellular phones. Many studies have shown little or no risk in using cellular phones, which operate in frequency bands immediately below wireless networks. Wireless network components should be even safer than cellular phones because they operate at lower power levels, typically between 50 and 100 milliwatts, compared to the 600 milliwatts to 3 watt range of cellular phones. In addition, wireless network components usually transmit for shorter periods of time. Laser-based products, found in both wireless LANs and MANs, offer very little or no health risks. In the U.S., the Center for Devices and Radiological Health (CDRH), a department of the U.S. Food and Drug Administration, evaluates and certifies laser products for public use. The CDRH categorizes lasers into four classes, depending on the amount of harm they can cause to humans. Supermarket scanners and most diffused infrared wireless LANs satisfy Class I requirements, where there is no hazard under any circumstance. Class IV specifies devices, such as laser-scalpels, which can cause grave danger if the operator handles them improperly. Most laser-based wireless MANs rate as Class III devices, whereby someone could damage their eyes if looking directly at the laser beam. Thus, care should be taken when orienting lasers between buildings. The Wireless Network MarketWireless networking is applicable to all industries with a need for mobile computer usage or when the installation of physical media is not feasible. Such networking is especially useful when employees must process information on the spot, directly in front of customers. Wireless networking makes it possible to place portable computers in the hands of mobile front line workers, such as doctors, nurses, warehouse clerks, inspectors, claims adjusters, real estate agents, and insurance salespeople. The coupling of portable devices with wireless connectivity to a common database and specific applications, as figure 1.13 illustrates, meets mobility needs, eliminates paperwork, decreases errors, and improves efficiency. The alternative to this, which many companies still employ today, is utilizing paperwork to update records, process inventories, and file claims. This manual method processes information slowly, produces redundant data, and is subject to errors caused by illegible handwriting. The wireless computer approach using a centralized database is clearly superior.
|
![]() |
Products | Contact Us | About Us | Privacy | Ad Info | Home
Use of this site is subject to certain Terms & Conditions, Copyright © 1996-2000 EarthWeb Inc. All rights reserved. Reproduction whole or in part in any form or medium without express written permission of EarthWeb is prohibited. Read EarthWeb's privacy statement. |