computer networking.pdf

 What is the Internet?
In this book we use the public Internet, a specific computer network (and one which probably most readers have used), as our 
principle vehicle for discussing computer networking protocols. But what is the Internet? We would like to give you a one-senten ce 
definition of the Internet, a definition that you can take home and share with your family and friends. Alas, the Internet is ve ry 
complex, both in terms of its hardware and software components, as well as the services it provides. 
A Nuts and Bolts Description
Instead of giving a one-sentence definition, let's try a more descriptive approach. There are a couple of ways to do this. One w ay is 

to describe the nuts and bolts of the Internet, that is, the basic hardware and software components that make up the Internet. A nother 
way is to describe the Internet in terms of a networking infrastructure that provides services to distributed applications. Let's begin 
with the nuts-and-bolts description, using Figure 1.1-1 to illustrate our discussion.