Class-12 Unit 2- Data Communication and Networking

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 Part: 1

Data Communication and Networking       

  Concept of Communication System

The exchange of data and information between sender and receiver through any given medium following a common rule is known as communication. So, telecommunication is the art of communicating at a distance. Telephone, radio and television are the main and popular media of tele-communication. Basic elements of communication 

Note: The exchange of data and information between sender and receiver through any given medium following a common rule is known as communication.

Computer Network
A group of interconnected computer which can share data, software and hardware and also communicate with other people is called computer network.

Advantages of computer network

  • Data sharing
  • Software and hardware sharing
  • Remote accessing facility
  • Communication facility
  • Workgroup computing
  • Backup and recovery

Disadvantages of computer network

  • leakage of private information
  • spreading of computer viruses
  • security problem
  • Needs skilled manpower to operate
  • software piracy

Components / elements of data communication

Message: What it is: The actual information or data to be communicated.
          Example: A text, an email, a picture, a video, or a voice signal.

Sender:What it is: The device that creates and sends the message. Example: A computer, a smartphone, or a server.

Receiver:What it is: The device that receives the message.Example: Another computer, a printer, or your friend's phone.
Communication media:What it is: The physical path or channel through which the message travels from the sender to the receiver.Example: Wires (like Ethernet cables), fiber optics, or wireless signals (like Wi-Fi or Bluetooth)
Protocol: What it is: A set of rules that governs data communication. It is an agreement between the sender and receiver on how the data will be sent and received.Example: TCP/IP - the fundamental protocol that manages how data is sent and received over the internet.

Communication Mode/ Transmission mode 

Communication mode defines the direction of data flow in the communication. 

1. Simplex Communication: In this type of communication data transmission takes place only in one direction. It is also called a unidirectional communication mode.


Radio, Television, Newspaper and keyboard to CPU Communication are some of the most common example of simplex communication.

2. Duplex Communication: 

In duplex communication, mode data transmission is possible from both directions. The receiver can immediately respond to the sender. The duplex communication can be categorized into two groups. a. Half Duplex: 

In this type of communication mode data can be transmitted in both directions, but only in one direction at a time. Both sender and receiver cannot transfer the data at a time. While sending data it cannot receive it and while receiving data it cannot send.

Willkie Talkie used by the police man is the best example of Half duplex communication mode.

2. Duplex Communication: 

In duplex communication, mode data transmission is possible from both directions. The receiver can immediately respond to the sender. The duplex communication can be categorized into two groups. a. Half Duplex: 

In this type of communication mode data can be transmitted in both directions, but only in one direction at a time. Both sender and receiver cannot transfer the data at a time. While sending data it cannot receive it and while receiving data it cannot send.

Willkie Talkie used by the police man is the best example of Half duplex communication mode.


b. Full Duplex

Full Duplex communications allows data to flow the information at the same time. Speaking on telephone of full Duplex communication mode in which both the sender and receiver can speak simultaneously. Bidirectional communication at the same time is called full duplex communication mode. Example, Telephone

 


 

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 Part: 2

Data Communication and Networking

Transmission media / Communication media
It refers to the wires, cable and other means through which data transfer from its source to destination. A transmission media is defined as the means of communication between two networking devices that helps to transfer data from sender to receiver and vice versa.

Transmission media is broadly classified into two groups.

1)      Bound (guided) media

2)      Unbound ( unguided) media 

S.N.

Guided Transmission Medium

S.N.

Unguided Transmission Medium

1

Signal is directed and contained by the physical limits of the medium.

1

It has no physical medium for the transmission of electromagnetic signals.

2

It is called wired communication or bounded transmission media.

2

It is called wireless communication or unbounded transmission media.

3

The signal energy propagates through wires in guided media.

3

The signal energy propagates through air in unguided media.

4

It types are twisted pair cable, coaxial cable and fiber optic cable.

4

It types are radio wave, microwave and infrared.

5

Examples: Twisted pair cable, coaxial cable and fiber optic cables.

5

Examples: Microwave or radio links and infrared light.

1. Wired or Guided Media or Bound Transmission Media: The transmission of data and information from source to destination by using physical medium like wires are called bounded transmission media. Its types are as follows.

     1) Twisted pair cable

      i) Shielded Twisted pair cable (STP)                        ii) Unshielded Twisted pair cable(UTP)

2) Coaxial Cable:

3) Fiber optics 

Twisted pair cable: A pair of copper wires is twisted to each other in a helical path making the same structure as a DNA molecule.



-          The reason for twisting is to reduce electrical interference.

-          It is the cheapest and easily available wire.

-          It is mostly used in telephone systems.

Advantages

1.      It is cheaper than other cables.

2.      It is light and thin. So, it is flexible for LAN.

3.      It can travel data in short distance with higher bandwidth. 

Disadvantage  

1.      It is only used for short distance transmission.

2.      It can be affected by electrical and magnetic field.

3.      It is slower type of transmission media compared to other cables.

STP (Shielded Twisted Pair)

Shielded Twisted Pair cable is identical to UTP but it contains the extra shield covering the each pairs of cables. The installation of STP is comparatively difficult than UTP and they are more expensive than UTP but has high bandwidth.


Features of STP Cable

» Better performance and high data transfer rate.

» Eliminates cross talk

» Faster than UTP

          » More expensive 

UTP (Unshielded Twisted Pair)

UTP is a commonly used cable because it is easy to install and is suitable for data and voice transmission. Unlike STP, UTP cable doesn’t have the extra protection shield.

Features:

§  Less expensive.

§  Easy to install.

§  High speed capacity.

§  Susceptible to external interference.

§  Lower capacity and performance than STP .Short distance transmission

S.N.

UTP

S.N.

STP

1

Electromagnetic interference and noise is more in UTP

1

STP cable reduce electrical noise within the cable and from outside of the cable.

2

It offers speed or throughput of about 10 to 1000 Mbps.

2

It offers speed or throughput of about 10 to 100 Mbps.

3

It offers maximum cable length of about 100 meters.

3

It supports maximum segment of length about 100 meters.

4

UTP is widely used for data transmission within short distance and is very popular for home network connecting.

4

STP is mainly used for connection of enterprises over a long distance.

5

The cost of UTP is less when compared to that of STP.

5

STP is costlier than UTP.

Coaxial Cable: A coaxial cable consists of a thick copper wire in the core, surrounded by an insulating plastic with a net of thin copper wires used as earthling and in the outermost part. Example TV cabling system.

-          It is better.

-          It has higher degree of noise immunity and 

-          High bandwidth but are expensive.


Advantages:

1.      It is faster and reliable than twisted pair cable.

2.      It can transfer data over medium range of distance.

Disadvantages

1.      It is not appropriate for relatively larger distance.

2.      It is expensive than twisted pair cable.

3.      It is rarely used in computer network.

 

Fiber Optics: It is the most advanced media in communication, which uses light rather than electricity to transmit information. Optical fiber is very thin media, which is measured in microns and is very hard to identify with our necked eye.

 


Advantages:

1.      It has higher bandwidth that means it can handle large volume of data.

2.      This medium can be used for long distance transmission.

3.      It is the most secured and error free transmission medium.

Disadvantages

1.      It is one of the expensive type of transmission media.

2.      It is not used for short distance transmission.

3.      Highly qualified and technical manpower are required to operate on fiber optics. 

    

2. Wireless or Unguided Media or Unbound Transmission Media: Unbound transmission is also called wireless or unguided media. If there is no physical connectors (wires) between the two communicating device is called wireless transmission media. Its types are as follows.

1.      Radio Wave

2.      Microwave

3.      Infrared

                     4.   Satellite Communication

Radio wave:

Although radio waves are prevalent and well understood, we are just beginning to realize their enormous potential as a networking medium. Radio waves can operate on single or multiple frequency bands. In this case, the signals are carried over carrier waves which have frequencies in the range of radio frequency spectrum.


 

2.Microwave system: It uses very high frequency radio signals to transmit data through the air. The transmitting and receiving antennas must be placed on tall buildings or towers, hills and mountains peaks.

  •        For long distance transmission, repeaters are used at different intervals.·      
  •    When one repeating tower receives the signal, it amplifies the signal and sends it to the new tower.

4) Satellite communication

  • ·         It is the most common world wide communication system at present.
  • ·         It uses a satellite as a repeater.
  • ·         The satellite is a repeater that orbits in space.
  • ·         It has receivers and transmitters located in the ground station.
  • ·         The satellite amplifies the weak signal and transmits it back to the receiver.
  • ·         Multiple satellite are used for longer distance transmission.

3) Infrared technology

  • It can be used for short distance transmission.
  • It is mainly used in wireless remote control, wireless LAN, wireless mouse and keyboard, bluetooth, etc.
  • They cannot penetrate the wall or any solid objects.
  • It cannot be used outside the buildings because sun rays contains infrared rays that can interfered with communication.


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PART 3

BASIC ELEMENT OF COMMUNICATION SYSTEM

The communication system is a system which describes the information exchange between two points. The process of transmission and reception of information is called communication. The major elements of communication are the Transmitter of information, Channel or medium of communication and the Receiver of information. 

Types of computer Network on the basis of geographical area coverage:

1.      Local Area Network (LAN)
2.       Metropolitan Area Network (MAN)
3.      Wide Area Network (WAN) 
1. Local Area Network (LAN): A LAN is privately owned small size network. It spans only in small geographical area such as within a room, office, buildings or up to few kilometers (2 to 3 Km). it connects the network resources such as computers, faxes, printers and various networking devices. 
LAN is the interconnection of computers in a limited geographical area like in a office, college, building, home.

     







 Advantages of LAN

a. It is cheaper to established.
b. It is easier to manage and operate.
c. Data transmission speed is faster than MAN & WAN.
Disadvantages of LAN
a) It is limited only to a small area
b) It connects a small number of computers. 
c) Lack of backup provision 

1.      Metropolitan Area Network (MAN): A MAN can be either public or privately owned network. Its size is bigger than LAN and smaller than WAN. It spans within one metropolitan city or larger geographical area. It can connect large number of computers and heterogeneous multiple LANs within a city maximum, up to 100Km.



Advantages of the MAN
a) It covers large area than LAN.
b) It can connect dissimilar systems and networks.
c) It connects many numbers of computers than LAN.
Disadvantages of the MAN
a) It is complex to manage and provide security
b) It is expensive to run than LAN. 
c) Transmission speed is usually slower compared to LAN. 

3 Wide Area Network (WAN): A WAN is basically public type heterogeneous network. It is the largest sized network and connects millions of computers, thousands of LANs, hundreds of MANs around the countries, continents and even the whole world. 


Advantages of the WAN

a. It covers very large geographical area.
b. It also connects dissimilar system and networks.
c. It connects larger number of computers than LAN and MAN.
Disadvantages of the WAN
a. It is more complex to establish, manage and operate.
b. It provides less security.
c. Transmission speed is usually slower.
d. It is expensive to establish.

 Differentiate between LAN and WAN

S.N.

Local Area Network (LAN)

S.N.

Wide Area Network (WAN)

1

Area covered within a local site.

1

Distance up to thousands of K.M.

2

Higher data transfer rates (10 Mbps to 1Gbps even more).

2

Data transfer rate is less 

3

It has low error rates.

3

It has higher error rates.

4

It uses simple protocol, low cost devices and low cost installation.

4

It uses complex protocols, expensive devices and high cost installation.

5

It can support limited number of hosts.

5

It can support large number of hosts.

6

Eg. Star, cellular topologies etc.

6

Eg. Internet and intranet

7

Generally, LANs use wireless or digital transmission.

7

WANs use digital or analog signal transmission.

 Types of computer network on the basis of network architecture:

a) Client - server Architecture
In a client - server architecture server always provides its resources to the clients and client always receives resources from the server. In a client - server architecture, there must be at least one dedicated server and client computers.


Advantages 

1.      Centralized administration is possible through this network.

2.      High security can be provided by suing appropriate server.

3.      It is appropriate for large organization.

4.      Data recovery and backup process is easier.

Disadvantages 

1.      If server fails whole network is affected.

2.      It is expensive due to use of dedicated server.

3.      It is complex to establish and manage.

4.      Experienced administrator is required to operate. 

b) peer to peer architecture
In a peer to peer architecture, all computers have equal authority to access data and therefore are known as peers. Each Computer Functions as both client and a server.


Advantages

1.      It is simple cheap and easier to set up.

2.      Since there is no dedicated server, user can manage their own server.

3.      Failure of a computer in a network doesn't affect the other computer in a network.

  Disadvantages

1.      Data security is very poor in this type of architecture.

2.      Data recovery and backup is difficult.

3.      It is not appropriate for large scale organization.

4.      Network administration is difficult it without dedicated Server. 

Difference between Client Server and Peer to Peer  

Client Server

Peer to peer

It is also known as centralized or server based network.

It is also known as distributed network

It has central server computer.

There is no central server computer.

The central server manages, organize, and coordinate all network clients on the network.

Peers are equally privileged and equal participants in the application.

Peer to peer network are more expensive.

Peer to peer network are generally simpler and less expensive.

It has high security.

It is less security.

If server crashes there is a chance of data loss.

Data and information is shared around the network, so less chance of data loss.

Example, Google server, Yahoo server and Bank etc.

Example One to one computer and Bluetooth connectivity etc.


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Types of Network Topology

  1. Bus topology
  2.  Star topology
  3.  Ring topology
  4.  Mesh topology
  5.  Tree topology
  6.  Hybrid topology

Network or LAN topology and its types

Network topology refers to the physical layout of the network. It shows the geographical representation of all the links and linking devices, also called nodes. It is the shaped of Network. The main objectives of the network topology is to find out the most economical and efficient way of transmission channel.

Its types are as:

1. Bus Topology: Computers are connected to a single continuous cable that is called 'bus'. It acts as backbone. It is based on client server network architecture.

Fig. bus topology 

   Advantages

-          It is simple and easy to setup and extend the network.

-          It required less cable.

-          If any computer in the network downs, then it does not affect the whole network.

-          We can easily connect and disconnect any number of computers in the bus.

     Disadvantages.

-          Data traffic is very high in bus.

-          If there is problem in main cable then entire network goes down.

-          It is very difficult to find out the fault in the bus.

 

2. Star Topology:- Computers in the network are connected to each other with the help of central connecting device hub or switch or server. It is based on client server architecture. It is the most popular and widely used topology for LAN.

 

    Advantages

-          It is simple, reliable and easy to set up and re-configuration.

-          It is flexible to connect new computer and remove existing computer in the network.

-          It is very easy to find out fault.

-          If any computer in the network goes down, then other computers can continue their functions.

       Disadvantages

-          It requires very large amount of cables.

-          It is expensive topology.

-          If there is any problem in central device hub or switch then the entire network will be down.

-          The data traffic is high in central device hub.


3. Ring Topology:- Computers are interconnected to each other by making a closed circular structure that means each computer is connected to other two adjacent computer in either network architecture.


Fig. Ring Topology

Advantages

-          It simple and inexpensive topology.

-          There is less chance of data collision because of unidirectional data transmission.

-          There is no server so each computer has equal access facilities to the resources.

-          Its performance is better than bus topology for small size network.

Disadvantages

-          It is not flexible topology so it is difficult for adding and removing new nodes.

-          It is not suitable for large size network.

-          If there is problem in any computer or connection then the entire network goes down.

-          It is very difficult to find out the errors in the network.


4. Mesh Topology:- Every computer in the network has point to point connection to all other computers by using multiport connector. It is also based on peer to peer architecture.  

 

   Advantages

-          It is fastest and most reliable topology.

-          Failure in any computer or transmission media does not affect the rest of the network.

-          There is less amount of data traffic due to multiple paths. 

   Disadvantages

-          It is very much complex and most expensive topology.

-          It is difficult to find an error in the network.

-          It is difficult to add and remove nodes in the network so it is not flexible.

-          It requires maximum amount of cables and multiport connectors.

5.  Tree topology (Hybrid topology): This type of topology is the combination of two or more than two type of topology. In this topology both star and bus topology are connected with each other.


Advantages

-          It is easy to manage network as per our needs.

-          It is very flexible so we can add and remove any number of nodes.

-          It is easier to find the fault nodes or hubs in the network.

Disadvantages

-          The failure of root node will cause the failure of entire network.

-          It is expensive because it needs large number of cable and network device.

-          The data traffic is high at root nodes.



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2.13 Basic Concept of OSI Reference Model

The OSI (Open Systems Interconnection) model is a standard framework that explains how applications send and receive data over a network. It mainly focuses on showing how each communication layer is arranged and how they work together, one on top of another.

The OSI model describes seven layers, and each layer performs specific functions. These functions are carried out by a mix of software and hardware components such as applications, operating systems, device drivers, network interface cards (NICs), networking devices, and communication protocols. Together, they allow a system to transmit data signals across different physical media in a network.

The following figure lists the seven layers of the OSI (open system Interconnection) model:

Remember: "All Presidents Say They Need Data Protection"

1. Application layer

The application layer provides direct access to network services. It serves as the interface between the user and the network by providing services that directly support user applications. 
2. Presentation layer
The presentation layer is responsible for data compression and encryption. Data is compressed by transmission and uncompressed while data is received. An encryption technique is also implemented at this layer.
3. Session layer
The session layer is responsible for establishing, maintaining, and terminating a connection called a 'session'. Managing the session involves synchronization of user tasks and dialogue control (e.g., who transmits and for how long) (login name recognition and security function take place at this layer).
 4. Transport layer
The transport layer is responsible for source to destination [end-to-end] delivery of the entire message on the sending side, messages are packaged to from data packets for efficient transmission at this layer and assigned a tracking number (packet number) so they can be resembled in proper order. On the receiving side, the packets are reassembled, checked for errors, and acknowledged.
5. Network layer
Network layer is responsible for the source to destination delivery of packet possibly across multiple networks. It is of the network layer where the route from the source to the destination computer is determined. Routes are determined based on packet addresses and network conditions.
6. Data link layer
In this layer, the data frame is broken down into individual bits that can be translated into electronic signals and sent over the network. On the receiving side, the bits are reassembled into frames for processing by upper layers. Error detection and correction are also performed at this
7. Physical layer

The physical layer is connected with transmitting raw bits over communication media unit. It also defines the electrical characteristics of the signals used to transmit the data. The physical layer transmits the binary data (bits) as electrical or optical signals depending on the medium.

IP address and its class

An IP (Internet Protocol) address is a 32-bit number which uniquely identifies the devices like computer, printer, router etc. on a TCP/IP (Transmission Control Protocol/Internet Protocol) network. These devices in a network are termed as host. IP addresses are represented by four numbers separated by dot.



For example, let us consider an IP address 192.168.125.137 

The 32-bit notation for above IP address is

1100000010101000111110110001001

For conveniency these 32 bit binary notation is divided into four parts each having 8 bits. Each 8 bits parts are known as octets. The IP address in binary notation is 11000000.10101000.1111101.10001001

Again IP addresses are divided into several classes. Most common are Class A, B and C. Class D and E are not used by end users. Different classes of IP address can simply distinguish by looking at its first octet. All three classes of IP addresses are explained briefly with their range:

Types of IP address

Class A IP address 

Class A IP address has their first octet ranging from 0 to 127. Let us consider, an IP address 82.52.36.11. Since its first octet is 82 which is within the range of 0-127, we can say it is a class A IP address. Its default subnet mask is 255.0.0.0

Class B IP address 

Class B IP address has their first octet ranging from 128 to 191. Let us consider, an IP address 182.36.52.11. Since its first octet is 182 which is within the range of 128-191, we can say it is a class B IP address. Its default subnet mask is 255.255.0.0

Class C IP address 

Class C IP address has their first octet ranging from 192 to 223. Let us consider, an IP address 192.136.42.11. Since its first octet is 192 which is within the range of 192-223, we can say it is a class C IP address. Its default subnet mask is 255.255.255.0

Transmission Impairment:

Transmission impairment means any problem that occurs while sending data. The received signal becomes different from the original due to imperfections in the medium. This reduces communication quality.

1. Jitter:

Jitter is the variation in packet arrival time. In real-time applications, even small delays cause problems.

Example: Video freezes or audio delays during online gaming or video calls.

2. Echo & Singing:

Echo is the reflection of your own voice during a call. It affects clarity and irritates the talker.

Example: Hearing your own “Hello” again on the phone.

3. Cross Talk:

Cross talk occurs when signals from one wire mix with another nearby wire.

Example: Hearing another person's conversation faintly in your phone line.

4. Noise:

Noise is unwanted signal that mixes with the original signal and distorts it.

Example: FM radio producing “shhh…” or crackling sounds.

5. Attenuation:

Attenuation is the weakening of signal strength as it travels through a medium.

Example: Voice becoming faint when someone shouts from far away.

6. Distortion:

Distortion happens when the original signal’s shape or frequency changes during transmission.

Example: Music becoming unclear or stretched after transmission.

Bandwidth:

Bandwidth is the data-carrying capacity of a communication channel. High bandwidth allows faster data transfer.

Example: 100 Mbps internet is much faster than 5 Mbps due to higher bandwidth.

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