Introduction computer networks and communications

The purpose of a computer communications network is to allow

moving information from one point to another inside the network. The

information could be stored on a device, such as a personal computer in the

network, it could be generated live outside the network, such as speech, or

could be generated by a process on another piece of information, such as

automatic sales transactions at the end of a business day. The device does not necessarily have to be a computer; it could be a hard disk, a camera or even a printer on the network. Due to a large variety of information to be moved, and due to the fact that each type of information has its own conditions for intelligibility, the computer network has evolved into a highly complex system. Specialized knowledge from many areas of science and engineering goes into the design of networks. It is practically impossible for a single area of science or engineering to be entirely responsible for the design of all the components. Therefore, a study of computer networks branches into many areas as we go up from fundamentals to the advanced levels. Advancements in communication of speech have long been matured

in the form of public switched telephone network (PSTN). However, design

of store-and-forward type of networks, such as the internet, is far from

matured - perhaps due to proliferation of the ways in which such networks are

used. The integration of the two types of networks is the culmination of

telecommunications technology. It is not futuristic to imagine

telecommunications networks meeting the needs of live traffic (e.g., phone

calls) as well as store-and-forward data (e.g., email) traffic according to the

desired quality of service.

In this chapter, we look at a computer network as a whole, from both

an application point of view and a design point of view. In fact, the design and

application influence each other so much that a study of the fundamentals is

practically impossible by leaving either one out