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Wireless Networking Handbook
(Publisher: Macmillan Computer Publishing)
Author(s): Jim Geier
ISBN: 156205631x
Publication Date: 09/01/96

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Another tip, especially if no frequency management organization exists within your company, is to run some tests to determine the propagation patterns within your building. These tests let you know if existing systems may interfere with, and thus block and cause delay to, your network. You will also discover whether your signal will disturb other systems. See Chapter 8, “Designing a Wireless Network,” for details on ways to perform propagation tests (site survey).

Power Management

If you are using a portable computer in an automobile, performing an inventory in a warehouse, or caring for patients in a hospital, it might be cumbersome or impossible to plug your computer into an electrical outlet. Thus, you will be dependent on the computer’s battery. The extra load of the wireless NIC in this situation can significantly decrease the amount of time you have available to operate the computer before needing to recharge the batteries. Your operating time, therefore, might decrease to less than an hour if you access the network often.

To counter this problem, vendors implement power management techniques in their PCMCIA format wireless NICs. Proxim’s wireless LAN product, RangeLAN2/PCMCIA, for example, maximizes power conservation. RangeLAN2 accommodates advanced power management features found in most portable computers. Without power management, radio-based wireless components normally remain in a receptive state waiting for any information. Proxim incorporates two modes to help conserve power: the Doze Mode and the Sleep Mode. The Doze Mode, which is the default state of the product, keeps the radio off most of the time and wakes up periodically to determine if any messages await in a special mailbox. This mode alone utilizes approximately 50 percent less battery power. The Sleep Mode causes the radio to remain in a transmit-only standby mode. In other words, the radio wakes up and sends information if necessary, but is not capable of receiving any information. Other products offer similar power management features.

System Interoperability

When implementing an ethernet network, network managers and engineers can deploy NICs from a variety of vendors on the same network. Because of the stable IEEE 802.3 standard that specifies the protocols and electrical characteristics that manufacturers must follow for ethernet, these products all speak exactly the same language. This uniformity allows you to select products meeting your requirements at the lowest cost from a variety of manufacturers. Today, this is not possible with most wireless network products, especially wireless LANs and MANs. The selection of these wireless products is predominantly single vendor, sole-source acquisitions. Products from one vendor will not interoperate with those from a different company. This raises a problem when deploying the network. Once you decide to buy a particular brand of wireless network component, you must continue to purchase that brand to ensure that the components can talk the same language as the existing ones. Putting yourself in this situation is risky. What happens if your wireless vendor decides to discontinue the product you chose?

As mentioned earlier, the solution to this problem, at least for wireless LANs, is very near. The IEEE 802.11 Working Group plans to issue final standards for wireless LANs by 1997. Wireless LAN vendors should embrace the standard because they are active in the standard development process. Shifting their products to the standard will be easy for them.

Network Security

Network security refers to the protection of information and resources from loss, corruption, and improper use. Are wireless networks secure? Among businesses considering the implementation of a wireless system, this is a common and very important question. To answer this question, you must consider the functionality a wireless network performs. As described earlier, a wireless network provides a bit pipe, consisting of a medium, synchronization, and error control that supports the flow of data bits from one point to another. This setup corresponds to the lowest levels of the network architecture and does not include other functions such as end-to-end connection establishment or login services. Therefore, the only security issues relevant to wireless networks include those dealing with these lower architectural layers, such as data privacy.

Security Threats

The main security issue with wireless networks, especially radio networks, is that they intentionally propagate data over an area that may exceed the limits of the area the organization physically controls. For instance, radio waves easily penetrate building walls and are receivable from the facility’s parking lot and possibly a few blocks away. Someone can passively retrieve your company’s sensitive information by using the same wireless NIC from this distance without being noticed by network security personnel (see fig. 1.10). This problem also exists with wired ethernet networks, but to a lesser degree. Current flow through the wires emits electromagnetic waves that someone could receive by using sensitive listening equipment. They must be very close to the cable, however, meaning they must first break through physical security.


Figure 1.10  The passive reception of wireless network data.

Another security problem is the potential for electronic sabotage, in which someone maliciously jams the radio-based network and keeps you from using the network. Remember, wireless networks utilize a carrier sense protocol to share the use of the common medium. If one station is transmitting, all others must wait. Someone can easily jam your network by using a wireless product of the same manufacture that you have within your network and setting up a station to continually resend packets. These transmissions block all stations in that area from transmitting, which is most serious if your company stands to experience a great loss if the network becomes inoperable.


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