Data Communication & Computer Network

Data Communication and Computer Networking is the fastest growing sector in all technologies in today’s internet world. Data Communication is defined as the transfer of data between two or more than two devices from one place to another. Data Communication between these remote devices can be achieved from the process called Networking. Networking is the computer science department that includes the connection of Computers, media, and Computer Networking devices. In this tutorial, we will understand about Data Communication components, types of Data representation, creation of data flow, Networking categories (LAN, WAN, etc.) and their functionality, Protocols, and standards, Network models, etc.

What is Data Communication?

Data Communication refers to the sharing of information between local or remote parties. It can be either local (face to face) or remote (take place over distance).

Data Communication is made up of two words as follows:

  • Data- It refers to the information presented by users in any form.
  • Communication- It refers to the exchange of data between two or more devices.

Data Communication is defined as the exchange of data or information between two or more devices through some transmission channels like wire cable, etc. These communication devices made up of a combination of hardware and software.

Further, the word Telecommunication is made up of a combination of two words, “Tele” and “Communication”. Tele is a Greek word that means far and communication means exchange of data or information. So, the exchange of information between two or more than parties that are placed over a distance.

Ex– Telephone, telegraph, and television, etc.

Important characteristics of Data Communication system:

The effectiveness of Data Communication system depends on four characteristics as follows;

  • Delivery

The Data communication system is completely responsible for delivering the data to the correct device or user.

  • Accuracy

The Data communication system is completely responsible for delivering accurate data to the correct device or user.

  • Time

A Data Communication system must deliver real-time data to the intended device or user. If there is any delay in delivering the data by the system, then this data may be useless. This kind of delivery is known as real-time transmission.

  • Jitter

Jitter is defined as the difference between the packet arrival time or uneven delay in the delivery of audio and video packets.

Components of Data Communication:

A Data Communication system comprises five components as follows:

  • Message

The message refers to the data or information to be communicated in forms of text, numbers, pictures, audio, and video, etc.

  • Sender or source

The sender is the device used to communicate the message. For e.g. a camera, computer, mobile, telephone, etc.

  • Receiver or destination

The receiver is the device used to receive the information message sent by the sender. For e.g. computer, television, mobile, etc.

  • Medium

A medium or transmission medium refers to the physical path by which a message or information travels from source to destination or sender to receiver. For e.g. twisted-pair wire, radio waves, optical fiber, coaxial cable, etc.

  • Protocol

A Protocol is defined as the set of instructions used in the Data Communication system. Communication between two or more devices is not possible without protocol; however, these devices may be connected without it. For e.g. A person speaking Chinese can’t communicate with a person who speaks Hindi.

What is Data Representation?

To represent the information or data in different forms such as text, images, audio, video, numbers, etc is called Data Representation.

  • Text: In the Data Communication system, the text is represented by the sequence of bits (0s or 1s). This sequence of bits is called a bit pattern. These sets of bit patterns used to represent text symbols. The process of symbols representation is called coding and each set is called code. The most popular coding system is called Unicode which uses 32 bits to represent a symbol or character in any language. The American Standard Code for Information Interchange (ASCII) constitutes the first 127 characters in Unicode.
  • Numbers: Numbers are also represented by bit patterns. Representations of numbers are not used in the ASCII coding system. Numbers are directly converted into binary form to simplify the mathematical operations.
  • Images: Images refer to the pictorial form of information to be communicated and also represented by bit patterns. An image composed of a matrix of pixels (small dot). The size of an image depends on the parameter called Resolution. To represent a better image, the resolution should be high and needed more space to store that image.

In Images, each pixel is assigned a bit pattern, and the size or value of this pattern depends on the image. Below is the table representing the pixel with respect to the bit pattern as follows.

Bit patterns



Purely Black


Dark Gray


Light Gray


Purely White

By the above table, you can easily understand that if an image made of only Black and White dots, then the 1-bit pattern is used to represent the pixel solely. Further, if any image comprises the Gray scale in its formation, then the 2-bit pattern is used to represent the pixel.

RGB is the most prevailing method used to represent color images. RGB stands for Red Green Blue, as these three colors are primary colors. Each color is made from the combination of these three primary colors. A bit pattern is assigned to each color followed by measuring its intensity.

Further, there is another method used to represent the color images is YCM. It is made from the combination of Yellow, Cyan, and Magenta.

  • Audio: An Audio refers to the message in the form of sound or music. Audio is continuous in nature not discrete. For e.g. Microphone is used to convert the voice or music into an electrical signal.
  • Video: A Video refers to the message in the form of picture or movie. It can be either continuous or discrete in nature. For e.g. Television, camera, etc.

Data flow-

When two devices communicate with each other through sending and receiving data between them is called data flow. Data flow can be in different ways in these devices as follows:

  1. Simplex
  2. Half Duplex
  3. Full Duplex


In Simplex mode, two or more devices communicate in one direction or one-way or the communication in this mode is unidirectional.

In this mode, only one device transmits the data, and the others receive this data.

Example of Simplex– Keyboards and traditional monitors are the best examples of Simplex mode. A keyboard is used to enter the data as input while the monitors are used to receive the output. This transmission of data is unidirectional or in one way only.


In Half-Duplex mode, both devices can transmit and accept the data signals but not at the same time. In simple words, we can say that when a device sends data, other device receives it and vice-versa. This mode of data flow is used in cases where no need for data communication in both directions at the same time and entire channel capacity can be utilized for each direction.

The Half-Duplex mode of data flow is just like a one-way road where only the traffic is allowed only one direction at a time while others have to wait to clear it.

Examples of Half-Duplex- CB (citizens band) radios and walkie-talkies, etc.


The Full-Duplex mode is also called the Duplex mode in which both devices can transmit and receive the data simultaneously. Unlike the Half-Duplex mode, in Full-Duplex mode, the data or signals transmitting in one direction can utilize the entire capacity of the link with data flowing in another direction. The entire channel capacity must be shared between these two devices at the same time.

This mode of data flow is like a two-way road where the vehicles are allowed to go both directions at the same time.

Example of Full-Duplex/Duplex- Mobile phones are the best common example of Full-Duplex mode where both persons are allowed to talk at the same time over telephone lines.

Computer Networks

A network or sometime called nodes is a set of devices connected through some communication links. These nodes can be a computer, printer or any devices which is capable of transmitting signals at one node and received it at other nodes on the network. Computer networks are used to communicate data between two devices.

Distributed Processing:

In distributed processing a task in divided among multiple systems or nodes. In this, a subset is handled by the personal computer, instead of single large machine that is responsible for all types of process in communication.

A computer network should ensure certain number of criteria like performance, reliability and security.

Performance– The performance of any computer network is based on transit time as well as response time. Performance is calculated by two metrics called as throughput and delay. For better performance of any system we need more throughout and less delay in communication. To send more data over any network, we have to increase throughput and for traffic congestion we have have to increase delay time of network.

Performance of any network depends on some factors as follows:

  • Number of users
  • Transmission medium
  • Hardware and software used in network.
  1. Reliability- Reliability is an attribute of any network which is measured by few parameters such as:
  2. Frequency of failure
  3. Recovery time of a link/network after a failure
  4. Network robustness in a catastrophe
  5. Security- Security of any network includes the prevention of data from viruses and unauthorised access over network. Further we need to implement some policies and procedures to recover lost data from data breaches as well as prevent the data from damage and development.

Physical Structures or Network attributes:

There are some network attributes discussed to understand the networks in a better manner.

Types of connections:-

Connection is the type of any physical or virtual link that is required to connect two or more devices together. This link is a communication pathway which is used to transfer data from one device to others at the same time.

For better understanding we can imagine it mathematically through a line drawn from a point A to another point B. This line is carrying data from A to B and B to A at the same time.

There are two important types of connections are as follows:

  • Point-to-Point connection
  • Multipoint connection

Point-to-Point connection- To establish a dedicated link between two or more devices, a point-to-point connection is used and this link reserves its entire capacity for successful transmission between them. In this type of connections a wire or cable is used to connect both ends. However microwave or satellite links also available for such connections.

Example- Television remote is used to change TV channels by infrared rays and this remote establishes a point-to-point connection between remote and television.

Multipoint Connection- Multipoint connections are use when more than two devices share a common link between them. It is also called Multi-drop connection. In these type of connections the entire capacity of the link is shared spatially or temporally between available devices. If there are lots of devices that are sharing the link together, it called spatially shared connection.


Physical Topology is defined as a method to disburse the network physically or logically. A link is used to connect two or more devices, further two or more than two links are connected through the Topology. Hence, the Physical Topology represents the relationship between the link and devices (nodes) to one another.

Types of Topology-

There are five basic types of Topologies are possible and these are as follows:

  • Mesh Topology
  • Bus Topology
  • Star Topology
  • Ring Topology
  • Tree Topology

Mesh Topology-

  • In Mesh Topology, each device establishes a dedicated point-to-point connection with other devices. Dedicated means the link is carrying data between two devices that are connected together.
  • In Mesh Topology system, a host is connected through single or multiple hosts simultaneously having a dedicated point-to-point connection with one another. These hosts also act as a relay for others which don’t have dedicated point-to-point links.

Example of Mesh Topology- In Telecom industry, each regional office must be connected to every other regional office. This connection is called Mesh Topology.

Types of Mesh Topology:

Mesh Topology has two types and these are as follows-

  • Full Mesh- It provides most reliable network structure in all available topologies, in which all hosts establish a dedicated point-to-point connection with all other hosts.

In Full Mesh Topology, every new host requires n(n-1)/2 connections.

  • Partial Mesh- Unlike full Mesh, it does not require a dedicated point-to-point connection between the hosts. In this topology, hosts are connected in specific arbitrarily design to each other host. This topology provides the reliability some particular hosts, not for all.

How to find number of connection or physical links in Mesh Topology?

To find the number of connections or physical links in a Mesh Topology system, we have to assume that each node must be connected to every other node. If there are n numbers of nodes are available in system.

  • Suppose, node 1 is connected to other nodes,

Then total number of connections= (n-1)

  • Similarly, node 2 is connected to all other nodes,

Then total number of connections= (n-1)

Similarly, node n is connected to all other nodes and having (n-1) connections.

Now mathematically, we need n(n-1) physical links. However in Duplex mode, communication allows in both directions, hence we will divide the number of links by 2.

Total Number of links/connection required= n(n-1)/2

Advantages of Mesh Topology-

  • It is used to eliminate the traffic problems while carrying data from one node to other as it uses dedicated links which is responsible for carrying own data load by all networks.
  • It is robust which means while one link gets inactive, it does not affect the entire system.
  • It provides more secure connection in comparison to other topologies.
  • Fault identification and fault isolation is easy in this topology.

Disadvantages of Mesh Topology-

In Mesh topology, every device needs connection with every other device so, It requires more cabling as well as number of Input and Output (I/O) ports.

Installation and re-connection is difficult in Mesh topology system.