A network connection between machines allows them to transmit information to one another. Networks are often referred to as being local area networks (LANs), which range over small areas, generally less than a few thousand feet; wide area networks (WANs), which can span thousands of miles; or campus area networks (CANs), which are intermediate in size.
A network comprised of a linked group of networks is called an internetwork. For example, your machine may be part of a network within your building and part of an internetwork that connects your local network to similar networks across the country. Since the difference between a network and an internetwork is generally invisible to the user, the term "network" is used in this manual to refer to both networks and internetworks.
Machines attached to a network communicate using a network protocol, or common network language, to ensure that information is transmitted to the appropriate locations. An internetwork protocol, sometimes referred to as a relay, links networks together.