Computer Networks
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Computer Networks

This unit introduces computer networking and on completion of the unit it is expected that the student will able to understand the following concepts:

WHY HAVE COMPUTER NETWORKS EVOLVED?

In the early days of computing the interchanging of data between computers meant that, from the first computer, it had to be copied to a common media, such as punch cards, and these would be used to input the data to the second computer. Not only did this involve a lot of work, but it also meant that the data needed to be held on two computers in its entirety and a set of redundant punch cards had been produced.

In order to reduce the work involved, methods were tried which would link computers together so that the data could be transferred directly. One method used was to link the two computers together using serial cables. This worked but would generally only involve two computers. The transmission rate was slow and only over short distances, typically 2400 bits per second (bps) over 100 meters. If it was required to communicate over longer distances modems needed to be used and the communication rate be decreased.

Several factors have affected the evolution of Computer Communication since the early 1960s.

  • Changes in transmission media.
  • The evolution of computers themselves.
  • The Human need to communicate.

CHANGES IN TRANMISSION MEDIA

In the early days coaxial cable was widely used as a transmission media but its expense and its relatively low speeds encouraged other alternatives to be found, such as, twisted pair and fibre optic.

Twisted pair is now being superseded by Fibre optic cable which provides high band wide rates but is still comparatively expensive. Fibre optic cable is mainly used in Wide Area Networks, where it is used as links between one network and another or as a backbone to provide fast communication between other networks. It is generally used when a high speed link is required.

Fibre Optic cable are also used to provide secure Local Area Network environments, as no electrical signals, which can be picked up, radiate from the cable.

THE COMPUTER EXPLOSION

During the late 1900s the computer developed at an astonishing rate. In the 1960s there were Mainframe computers which were held in cabinets consuming lots of power. The users carried out their work at a dumb terminal and the CPU was weak compared to today's microprocessors.

Advances in microelectronics enabled the CPU, which usually spread over several cards, to be compressed into one integrated circuit - The Microprocessor. This had more computing power, operated at a higher clock rate, had lower power consumption and came at a lower price. The same advances made memory smaller and from the computers which typically contained 16KB we now have computers which contain 64MB minimum.

The computers can now carry out more tasks and can carry them out at the same time - Multi-Tasking

The PC has now become an essential item in most workplaces with tasks being carried out which can be as diverse as running Word Processors and Spreadsheets to Network Operating systems to Games.

THE HUMAN NEED TO COMMUNICATE

In the early days users were content to use textual information, have low computation power, and have it displayed as such.

Today the user demands a Workstation which can connect to international communication networks, show Multimedia presentations and always work. Organisations also demand computers which do not need maintaining. A lot of users work at home or at remote locations and need to have the resources of the centre (server, databases, main network etc.) available, just as if they were situated there.

Today, computers and networks have been designed to meet the demands of all users and planning is also going on to provide future developments such as transferring voice data and video which demand more and more bandwidth.

ADVANTAGES AND DISADVANTAGES OF NETWORKING

The main advantage of Networking is the capability to share resources. Files, printers, fax, the Internet, all of these are resources. Each user/computer on the network has the potential to access data stored on other machines. Expensive peripherals such as colour laser printers etc, can also be shared rather than one machine using a printer on it's own. Not only does this make sense from the point of view of cost, it also makes more efficient use of the printer. Another example of sharing on the network could be access to "The Internet", by running a Proxy Server which is connected to the Internet via a permanent link or a modem. Users would connect to the Proxy Server and gain access to The Internet. In this way, many users would have access to the Internet at the same time.

More about Transmission media

Computer History

Download - Packet Tracer 3.2

Lets play match the network pair- all you have to do is match one set of words with an associated pair
for instance you would match- Data, Segment , Packet, Frame, Bits with Encapsulation Steps.
GiVE IT A TRY

Network IVA