The past few years have seen some tremendous advances not only in networking technologies but also in the demands placed on them. In the past 25 years, we have seen the emergence of standards for 10Mb Ethernet, 16Mb Token Ring, 100Mb FDDI (Fiber-Distributed Data Interface), 100Mb Ethernet, 155Mb ATM (Asynchronous Transfer Mode), 655Mb ATM, 1Gb Ethernet, 2.5Gb ATM, and 10Gb Ethernet. Network technology designers are already planning technologies to support data rates of up to 100Gbps.

The average number of nodes on a network segment has decreased dramatically, while the number of applications and the size of the data transferred have increased dramatically. Applications are becoming more complex, and the amount of network bandwidth required by the typical user is increasing. Is the bandwidth provided by some of the new ultra-high-speed network applications (such as 1Gb Ethernet) required today? Maybe not to the desktop, but network backbones already take advantage of them.

Does the fact that software applications and data are putting increasing demands on the network have anything to do with data cabling? You might think that the issue is related more to network interface cards, hubs, switches, and routers but, as data rates increase, the need for higher levels of performance on the cable also increases.

Types of Communications Media
Four major types of communications media (cabling) are available for data networking today: Unshielded Twisted-Pair (UTP), Shielded or Screened Twisted-Pair (STP or ScTP), coaxial, and fiber optic. It is important to distinguish between backbone cables and horizontal cables. Backbone cables connect network equipment such as servers, switches, and routers and connect equipment rooms and telecommunications rooms. Horizontal cables run from the telecommunications rooms to the wall outlets. For new installations, multistrand fiber optic cable is essentially universal as backbone cable. For the horizontal, UTP accounts for 85 percent of the market for typical applications. Newer fiber-optic-based network topologies are providing more and more advantages over UTP.

In the following articles, I will introduce the four major types of communications media in detail.