net·work n: a group of computers connected to each other and can share the same resources
Networks are able to free up some of the burden on one computer by providing other computers to
take on the jobs. These computers can link to each other with a setup as simple as cables and
cards. They can connect to each other if they're in close proximity — a setup called a
local-area network — or they could connect to each other over the phone lines, most often
via the Internet. There are many different types of networks, in terms of the roles the computers
play, but we will focus on two important types.
Fig. 1: Peer-to-Peer Network
In a peer-to-peer network, two computers share the same resources —
printers, Internet connections, and files, to name a few — and application layers. One
computer may handle all the print jobs, while the other computer may be responsible for storing
and retrieving files.
Fig. 2: Hubs are used to connect more than one computer to each other
Since each computer handles a part of the resources, they are both servers.
And, because the resources are split up between the two, one computer may be running the
presentation layer and application logic of a program, while the other may be running the bottom
layer to fetch a file or print a document. Thus, the application is split up between two computers.
When more than two computers are connected, one simple cable won't suffice.
They connect to each other in the middle using a wiring hub, like that shown in figure 2, with various methods of
communication. These methods are discussed in the Network Communication section.
Fig. 3: A Client/Server Network
The client/server network is the most widely-used type of networking
because of its efficiency. Whereas the computers in a peer-to-peer network can perform multiple
operations, including running applications, displaying documents onscreen, and printing,
computers in a client/server network are more specialized.
A strict client/server network is only composed of two computers: one, the
server; the other, the client. The server provides all of the services and information and handles
printing requests, for example. The server generally controls all the resources and puts them at the
client's disposal. The client is the computer users interact with. If the client needs something it
doesn't have, it can send its request to the server. Similarly, a librarian has many resources at his
disposal, and the patron can request those resources from the librarian.
Networks may also consist of more than one server. Each of these servers has a
different and more specialized job, similar to specialists in a modern automobile assembly line. A
print server handles the print jobs of its clients and servers. A file server stores or sends files. An
application server runs applications and sends the results. Because each computer performs a
limited scope of functions, they are generally faster. You could think of different kinds of
librarians as these servers. One librarian can check out books, while another can handle questions
from patrons at the reference desk. With more people handling different tasks, that one lone
librarian no longer has to shoulder all the burden.