What Is a Network?

Before we plunge headlong into a discussion of how networks actually operate and what it takes to get them up and running (a discussion that will lead you through the other chapters of this book), we should probably first define what a network is and then discuss why you would want to connect computers into a network. A network can be anything from a simple collection of computers (two connected computers qualify as a network) at one location that have been tied together using a particular connectivity medium (such as network cabling or wireless technology) to a giant global network, such as the Internet, that uses a number of different connectivity media, including microwave and satellite technology. The network can then be used to transmit data, voice, and even video between users on the network.

Networks consist of the computers, the connectivity medium (such as copper wire or fiber optic cables), and other devices, such as hubs, switches, and routers (which are all discussed later in the book), that make up the network infrastructure. Some devices, such as network interface cards, serve as the computer's connection to the network. Devices such as switches and routers provide traffic-control strategies for the network. All sorts of different technologies can actually be employed to move data from one place to another, including network cabling (copper or fiber optics), radio waves, and even microwave technology.

Note

Networks are not networks just because they contain highly complex connectivity strategies. Two computers running the Windows Me operating system can be joined together by their COM ports (also known as serial ports ) by a single serial cable. Is this a network? Sure, it allows you to share resources between the two computers and therefore meets the basic definition of what a network is.

In our discussion of computer networks, we will be looking at two distinct entities: LANs and WANs. A local area network (LAN) is a collection of personal computers and other peripheral devices connected at one location. A wide area network (WAN) is a collection of LANs at different locations connected together using various WAN technologies (discussed in Chapter 13, "Expanding a LAN with WAN Technology").