What is a network?
A network is a group of computers and computer related equipment that are connected by some form
of communication facility. This can be either a permanent cable connection, a temporary connection
through a modem or some other communication device, or wireless.
These computers can communicate with each other and share programs and data. They can also share
other peripheral components they may have attached to them (printers, modems, hard drives etc.), and
also allow Electronic Mail (Email) to be implemented.
Usually networks are set up so that resources such as printers can be shared by many computers,
programs and data can be shared and maintenance and installation of software is made easier. Also
networks offer a level of security that is usually not present on stand alone systems.
A Local Area Network (LAN) usually means that the interconnected computers are not far from each
other (at most 1km to 2 km), although usually they are in an office or building.
A Wide Area Network (WAN) usually means that some of the components are not in close proximity
and these distant components are connected by phone lines, microwave, radio wave or satellite.
Overall, a network will consist of a set of connections to allow the separate parts to communicate
with each other and share services (such as sending and receiving files and data, printing or any other
thing that you might want to do on a network)
Client/server networks in particular
Novell is a client/server network operating system. This type of network has one main computer
which controls the network which is called the Fileserver (as it serves files to users as requested). It
has the Network operating system on it and has a large hard drive as the programs/applications used
by users on the network are usually stored here. As users need an application, their computer requests
it from the Fileserver and the Fileserver sends the application down to their computer (client station).
The program/application is then run from their computer’s memory (programs and data travel along
the network to the workstation so that they can be run or used).
We will only be concerned with the Ethernet networking scheme in this course. This uses the Carrier
Sense, Multiple Access, Collision Detection scheme (CSMA/CD) to determine who can send data on
the network. All workstations listen to the network cable and only send if there is no signal. If two
workstations send at the same time a ‘collision’ will occur and the data will become jumbled. Each
workstation will sense that there has been a collision (because of the jumbled meaningless data that
results from the collision) and so wait for a random time before trying again. Because of this, you
should limit the number of computers attached to any one Network Interface Card. The more
collisions, the slower the network will operate. | 
