Chapter Summary

Networks are often complex in design, maintenance, and implementation, and the basics—such as network media—are often forgotten. But network media are a foundation block of a network; as a network administrator, you will be required to understand the characteristics of the media commonly used in networks.

Several key characteristics and considerations determine a media's suitability for a specific network environment. These considerations include crosstalk, attenuation, EMI, bandwidth, installation and repair, and security. You need to understand each of these to determine the appropriate media for a network.

Networks use dialog modes to determine the direction that transmissions flow over the network media. Three dialog modes are used: simplex, half-duplex, and full-duplex. Simplex allows only one-way communication; half-duplex allows two-way communication, but devices cannot send and receive simultaneously; and full-duplex allows devices to simultaneously receive and transmit.

Several different types of cable are used on modern networks, including coaxial, twisted-pair, and fiber-optic cable. Each cable has different strengths and weaknesses, making some types of cable more suitable than others in a given network environment. Part of the role of the network administrator is to be able to identify the characteristics of the various cable types and to know how to troubleshoot them when required.

Each of these different cable types requires the appropriate connector. By far the most commonly used connector type today is the RJ-45 connector, which is used with twisted-pair cable. Other connector types include SC and MIC connectors for fiber-optic cable and BNCs for thin coax cable.

The IEEE 802.3 standard specifies Ethernet networking and uses the various cable media discussed in this chapter. The 802.3 LAN standards include 10Base2, 10Base5, 10BaseT, 100BaseT, and 1000BaseX network standards. Each of these standards specifies numerous networking characteristics, including network speed, cable type, topology, transmission method, and cable distance.

To be able to add clients to an existing network, you need to identify the connectors and cables that are already in use on the network. By using observation techniques—examining the cables and connectors already in use—you can find out what you need to know to correctly add computers to the network.