Computer Networks Introduction

A computer network can be two computers connected:
 
A computer network can also consist of, and is usually made for, more than two computers:

Characteristics of a Computer Network

The primary purpose of a computer network is to share resources:
  • You can play a CD music from one computer while sitting on another computer
  • You may have a computer that doesn’t have a DVD or BluRay (BD) player. In this case, you can place a movie disc (DVD or BD) on the computer that has the player, and then view the movie on a computer that lacks the player
  • You may have a computer with a CD/DVD/BD writer or a backup system but the other computer doesn’t have it. In this case, you can burn discs or make backups on a computer that has one of these but using data from a computer that doesn’t have a disc writer or a backup system
  • You can connect a printer (or a scanner, or a fax machine) to one computer and let other computers of the network print (or scan, or fax) to that printer (or scanner, or fax machine)
  • You can place a disc with pictures on one computer and let other computers access those pictures
  • You can create files and store them in one computer, then access those files from the other computer(s) connected to it
Peer-to-Peer Networking

Based on their layout (not the physical but the imagined layout, also referred to as topology), there are two types of networks. A network is referred to as peer-to-peer if most computers are similar and run workstation operating systems:
It typically has a mix of Microsoft Windows 9X, Me, Windows XP Home Edition, or Windows XP Professional (you can also connect a Novell SUSE Linux as part of a Microsoft Windows-based network; the current release of the operating system is really easily to install and made part of the network).
In a peer-to-peer network, each computer holds its files and resources. Other computers can access these resources but a computer that has a particular resource must be turned on for other computers to access the resource it has. For example, if a printer is connected to computer A and computer B wants to printer to that printer, computer A must be turned On.

Client/Server Networking

A computer network is referred to as client/server if (at least) one of the computers is used to "serve" other computers referred to as "clients". Besides the computers, other types of devices can be part of the network:

In a client/server environment, each computer still holds (or can still hold) its (or some) resources and files. Other computers can also access the resources stored in a computer, as in a peer-to-peer scenario. One of the particularities of a client/server network is that the files and resources are centralized. This means that a computer, the server, can hold them and other computers can access them. Since the server is always On, the client machines can access the files and resources without caring whether a certain computer is On.
Another big advantage of a client/server network is that security is created, managed, and can highly get enforced. To access the network, a person, called a user must provide some credentials, including a username and a password. If the credentials are not valid, the user can be prevented from accessing the network.
The client/server type of network also provides many other advantages such as centralized backup, Intranet capability, Internet monitoring, etc.
In these series of lessons, the network we will build is based on Microsoft Windows operating systems (I have been able to fully connect some versions of Linux, such as Novell SUSE Linux, into a Microsoft Windows-based network but at the time of this writing, I will not be able to address that).
In our lessons, we will mention the names of companies or provide links. These are only indications and not advertisements. Any other company or link that provides the mentioned service is suitable.