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Course : BCA

Semester : IV

Subject Code : BC 0048

Subject Name : Computer Networks

Unit number : 1

Unit Title : Introduction to Computer

networks

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Unit-1 Introduction to Computer networks

Introduction to Computer networks

Objectives

After going through the presentation, you should be able to learn:

• Definitions of Computer network

• Uses of Computer networks

• Classification of Computer networks

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Unit-1 Introduction to Computer networks

Lecture outline

• Introduction

• Definition of Computer Networks

• Uses of Computer Networks

•Classification of Computer Networks

•Summary

Introduction to Computer networks

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Unit-1 Introduction to Computer networks

Introduction

• The 18th century was the time of the great mechanical systems accompanying the industrial revolution. • The 19th century was the age of the steam engine. • During 20th century, the key technology is been gathering, processing, and distribution.

• The old model of a single computer serving all of the organization’s computational needs has been replaced by one in which a large number of separate but interconnected computers do the job.

• These systems are called computer networks. This course deals with the design, organization and application of these networks.

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Unit-1 Introduction to Computer networks

Definition of Computer Networks

A network is a group of various components connected together in such a way that, it is possible to distribute or collect information over the entire group. The term “Computer Network” is used to mean an interconnected collection of autonomous computers.

Two computers are said to be interconnected, if they are able to exchange information.

The connection can be wired or wireless.

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Unit-1 Introduction to Computer networks

Definition of Computer Networks

Components of a computer network :The most essential components of a simple network are listed below:1. Servers: Servers are faster computers that run various software’s, store and process information and also provide a human interface for the users to be able to use the networked computers.2. Nodes: Nodes are the computers on the network, which are provided to the users to carry out their tasks using the network.3. Workstation: A node, which is more powerful, and can handle local information processing or graphics processing is called a workstation.

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Unit-1 Introduction to Computer networks

Definition of Computer Networks

4. Network Operating System (NOS):

The network requires some software to control all the information transfer activity on the network, like the traffic police to control the traffic. The software called NOS handles these tasks. 5. LAN Software: LAN cables connect all the nodes and servers together to form the network. In addition to its local disk operating system, each node requires networking software that enable the nodes to communicate with the servers.

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Unit-1 Introduction to Computer networks

Definition of Computer Networks

6. LAN Cable:

This is the medium or channel over which the information travels from computer to computer.

7. Network Interface Card:

Each computer contains a network interface card. This card is used to connect the cables to the computers.

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Unit-1 Introduction to Computer networks

Uses of Computer Networks

Following are the uses of Computer Networks :

1. Resource sharing: The goal is to make all programs, equipments, especially data available to

anyone on the network without regard to the physical location of the resource and the user.

For example: Printers, scanners which are expensive resources can be shared among many computers.

2.High reliability :A second goal is to have alternative sources of supply. For example: All files

could be replicated on two or three machines, so if one of them is unavailable due to say hardware failures, the other copies could be used.

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Unit-1 Introduction to Computer networks

Uses of Computer Networks

3. Saving money :Small computers have mush better price/performance ratio than larger ones. Main frames are roughly a factor of ten times faster than personnel computers, but their cost is thousand times more than personnel computers. This is the fact that many system designers go for building systems where many personal computers are interconnected with a larger machine. 4. Scalability :It is the ability to increase system performance gradually as the workload grows just by adding processors. With the client server model, new client and new servers can be added as needed without any disturbance to the users. That is the network can be expanded easily.

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Unit-1 Introduction to Computer networks

Uses of Computer Networks

5. Communication medium among employees :A computer networks provides a powerful communication among the

widely separated employees. Using a network it is easy for two or more people who live far apart write a report together.

In addition to these goals we can find following uses of computer network1. Access to remote information 2. Person-to-person communication3. Interactive entertainment 4. Electronic commerce

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Unit-1 Introduction to Computer networks

Classification of Computer Networks

The computer networks are classified depending on transmission technology and scale. Few ways of classification are listed below. •By transmission techniques: Computer networks may be classified as broadcast or point to point networks.•By scale: to the scale or extent of reach of the network, for example as a Personal area network (PAN), Local area network (LAN), Campus area network(CAN), Metropolitan area network(MAN), or Wide area network(WAN). •By connection method: Computer networks may be classified according to the technology that is used to connect the individual devices in the network such as HomePNA, Power line communication, Ethernet, or Wireless LAN.

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Unit-1 Introduction to Computer networks

Classification of Computer Networks• By functional relationship: Computer networks may be classified according to the

functional relationships which exist between the elements of the network, for example Active Networking, Client-server and Peer-to-peer (workgroup) architectures.

• By network topology: Computer networks may be classified according to the network topology upon which the network is based, such as Bus network, Star network, Ring network, Mesh network, Star-bus network, Tree or Hierarchical topology network, etc.

• By services provided: Computer networks may be classified according to the services which they provide, such as Storage area networks, Server farms, Process control networks, Value-added network, Wireless community network, etc.

• By Protocol: Computer networks may be classified according to the communications protocol that is being used on the network.

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Unit-1 Introduction to Computer networks

Classification of Computer Networks

Based on transmission technology :Based of transmission technology we further have two classifications• Broadcast links and • Point-to-point links • Broadcast links :Broadcast networks have a single communication channel that is shared by

all the users on the network. Broadcast system generally allows the possibility of addressing a packet to

all the destinations by using a special code in the address field. When this code is transmitted, it is received and processed by every machine on the network.

This mode of operation is referred to broadcasting

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Unit-1 Introduction to Computer networks

Classification of Computer Networks

• Point-to-point links :

The point-to-point network consists of many connections between individual pairs of machines.

A packet to be sent from source to destination may have to first visit one or more intermediate machines.

Usually different routes of different length are possible.So finding the best path or route is important in point-to-point networks.Geographically localized networks or smaller networks tend to use

broadcasting where as larger networks usually are point-to-point networks.

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Unit-1 Introduction to Computer networks

Classification of Computer Networks

• Classifications Based on their Scale :Beyond the personal area network we have longer-range networks which

are broadly classified networks as 1. LAN 2. MAN 3. WAN

1.LAN :Local Area Networks are generally called LANs. They are privately owned

networks within a single building or campus of up to few kilometers in size. Most of LAN’s use Bus or ring topology for connection.

2. MAN :A Metropolitan Area Networks, referred as MANs covers a city. The best

known example is cable television network available in many cities.

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Unit-1 Introduction to Computer networks

Classification of Computer Networks

3. WAN :

A wide area network is referred as WAN. WAN spans a large geographical area often a continent or country. WAN contains a collection of machines, traditionally called as hosts. These hosts can be on LANs and are connected by a subnet or also called communication subnet.

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Unit-1 Introduction to Computer networks

Summary

This presentation of unit 1 covered the following topics:

• What is computer network ?

• Components of Network

• What are the goals of computer network

• Classification of computer network

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