Introduction To Computer Networks

Today the world scenario is changing. Data Communication and network have changed the way business and other daily affair works. Now, they rely on computer networks and internetwork. A set of devices often mentioned as nodes connected by media link is called a Network. A node can be a device which is capable of sending or receiving data generated by other nodes on the network like a computer, printer etc. These links connecting the devices are called Communication channels.

Computer network is a telecommunication channel through which we can share our data. It is also called data network. The best example of computer network is Internet. Computer network does not mean a system with control unit and other systems as its slave. It is called a distributed system

A network must be able to meet certain criteria, these are mentioned below:

  1. Performance
  2. Reliability
  3. Scalability


It can be measured in following ways :

  • Transit time : It is the time taken to travel a message from one device to another.
  • Response time : It is defined as the time elapsed between enquiry and response.

Other ways to measure performance are :

  1. Efficiency of software
  2. Number of users
  3. Capability of connected hardware


It decides the frequency at which network failure take place. More the failures are, less is the network’s reliability.


It refers to the protection of data from the unauthorised user or access. While travelling through network, data passes many layers of network, and data can be traced if attempted. Hence security is also a very important characteristic for Networks.

Properties of Good Network

  1. Interpersonal Communication : We can communicate with each other efficiently and easily example emails, chat rooms, video conferencing etc.
  2. Resources can be shared : We can use the resources provided by network such as printers etc.
  3. Sharing files, data : Authorised users are allowed to share the files on the network.

Basic Communication Model

Communication model is used to exchange data between two parties. For example communication between a computer, server and telephone (through modem).

Basic Communication Model


Data to be transmitted is generated by this device, example: telephones, personal computers etc.


The data generated by the source system are not directly transmitted in the form they are generated. The transmitter transforms and encodes the information in such a form to produce electromagnetic waves or signals.

Transmission System

A transmission system can be a single transmission line or a complex network connecting source and destination.


Receiver accepts the signal from the transmission system and converts it to a form which is easily managed by the destination device.


Destination receives the incoming data from the receiver.

Data Communication

The exchange of data between two devices through a transmission medium is Data Communication. The data is exchanged in the form of 0’s and 1’s. The transmission medium used is wire cable. For data communication to occur, the communication device must be part of a communication system. Data Communication has two types Local and Remote which are discussed below :

Local :

Local communication takes place when the communicating devices are in the same geographical area, same building, face-to-face between individuals etc.

Remote :

Remote communication takes place over a distance i.e. the devices are farther. Effectiveness of a Data Communication can be measured through the following features :

  1. Delivery : Delivery should be done to the correct destination.
  2. Timeliness : Delivery should be on time.
  3. Accuracy : Data delivered should be accurate.

Components of Data Communication

  1. Message : It is the information to be delivered.
  2. Sender : Sender is the person who is sending the message.
  3. Receiver : Receiver is the person to him the message is to be delivered.
  4. Medium : It is the medium through which message is to be sent for example modem.
  5. Protocol : These are some set of rules which govern data communication.

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