A network connects two or more computers, allowing them to communicate with each other and share resources. Computers and other devices (like printers) connected to the network are called nodes. Nodes on the network can be connected by cables (twisted-pair, coaxial, or fiber optic) or through wireless technologies (infrared, satellite, or microwave transmission).
Some networks include a hub which is the piece of hardware where all the nodes connect to one another. Networks can be connected to other networks through a gateway or bridge. (These devices serve the same purpose, but gateways connect networks of the different types; bridges connect networks of the same type.) A router manages data traffic within the network and to other networks (in connection with a gateway or bridge).
Networks come in all sizes, generally described in these terms:
Local Area Networks (LAN) connect nodes that are in close physical proximity to each other — in the same office or building for example. Most of the examples we use throughout this lesson refer to LANs.
Metropolitan Area Networks (MAN) have a larger geographical range, connecting nodes in separate buildings within a few miles of each other. Cellular phone systems are good examples of MANs. In order to have national coverage, the cellular company connects all of its MANs into a larger network, known as a WAN.
Wide Area Networks (WAN) have a national or global reach. With satellite technology, WANs can connect nodes that have no physical connection to one another. The Internet is the best example of a WAN — a global network of networks.