Lesson 2

Selecting Data-Link Layer Protocols

1-19

Wireless local area networking is becoming increasingly popular now that the products

are less expensive and more plentiful, but it is still a technology that is recommended

only for installations where a cabled topology is impractical. If you plan on having

computers on your network that are frequently moved to different locations, such as

laptops or mobile kiosks, wireless can be an excellent solution. Wireless is also a good

alternative in locations where running cables would be impractical, such as a lobby or

plaza where cable would clash with the décor.

Before incorporating any wireless networking technology into your network infrastruc-

ture plan, however, it is strongly recommended that you test the proposed technology

thoroughly in the actual locations where it will be used. Wireless transmissions are sub-

ject to interference from a wide range of environmental factors, including the number

and composition of walls between the transceivers, proximity to machinery and other

electrical equipment, and even climatic conditions. The effective transmission range of

a wireless device can vary from location to location and even from minute to minute.

You should always be sure that the medium you propose to use for your network be

viable in the intended location before you invest time and money in the network infra-

structure.

Security Alert

Because of recent developments in the wireless networking standards, the

popularity of wireless LAN technologies is growing quickly. However, the development of a

security infrastructure for these networks has not been growing quite as fast. By definition,

any wireless transceiver that comes into the effective transmission range of another trans-

ceiver of the same type has the potential to join that network. This creates a serious security

hazard because unauthorized users with wireless terminals can conceivably access network

resources from outside the organization. For more information on securing a wireless net-

work, see Chapter 13, “Designing a Security Infrastructure.”

Selecting a Transmission Speed

Another important factor in the selection of a data-link layer protocol for your network

infrastructure is the speed at which the network can transmit data. As with most data-

processing technologies, Ethernet networks have gotten faster over the years, and the

cutting edge of the technology is a trade-off between high transmission speeds and

high equipment prices. Selecting a transmission speed for your network is a matter of

determining your users’ current and future requirements and balancing them against

your budget.

Ethernet offers the most flexibility in terms of transmission speed. The original Ethernet

standard called for a 10 Mbps transmission speed. Fast Ethernet, introduced in the mid-

1990s, increased the maximum transmission speed to 100 Mbps, and Gigabit Ether-

net—the current state of the art—runs at 1,000 Mbps, or 1 gigabit per second (Gbps).