TABLE OF CONTENTS The word network has a variety of meanings, for example, in electrical circuits a network is an interconnection of two or more circuit elements such as resistors, inductors, capacitors, amplifiers and oscillators. If the network contains at least one closed path it is called a circuit (Hayt et al., 1978). In telecommunications work, a network is a connection of devices such as telephones, computers, switches, and printers. (And of course people can network together, which gives yet another meaning to the word).
Of particular interest to this chapter are broadband networks. The word broadband in the context of telecommunication networks means that the network is designed to carry voice, data, video, and image type signals. The Internet is a broadband network. This mixture of signals can also be carried by a method known as asynchronous transfer mode (ATM). In this chapter the word network will mean a broadband network.
A key feature of broadband networks is the way in which information is assembled into packets which can be transmitted on an as needed basis. This differs from previous methods where information was (and still is in many cases) transmitted as a continuous signal. Packet transmission as originally designed for data (such as computer output and email) was found to be unsuited for voice transmission, the packets being too large. With mixed packets of voice and data, the large data packets could introduce unacceptable delays in the reassembly of the voice packets.
