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COMMUNICATIONS

AND

NETWORKS

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Communications

The process of sharing data, programs, and information

between two or more computers

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Communications Today

Numerous applications depend on communicationsystemsE-mail , Instant messaging (IM), Internet telephone, and Electronic commerce

C onnectivity uses computer networks to link people

and resources Going w ireless has been the most dramatic change

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Communication Systems

Four basic elements ± Sending and receiving devices

 ± Communication channel

 ± Connection devices

 ± Data transmission specifications

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Connection Device Signals

Types of signals

 ± Analog

 ±

Digital 

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Communication Channels

Channels carry data from one computer to

another

Two categories of communication channels

 ± Physical connection

 ± Wireless connection

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Physical Connections

T elephone lines

C oaxial cable

Fiber-optic cable

Return

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Wireless Connections

Infrared 

Broadcast radio

 ± Wi-FI (wireless

fidelity)/802.11

Microw ave

 ± Stations

 ± Bluetooth

Microwave dish

Infrared, Broadcast Radio, Microwave

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Wireless Connections - Satellites

Satellite

 ± Uplink/Dow nlink 

 ± Global Positioning System

Global positioning

 ± Network of 24 satellites

 ± Owned by the Defense Department

Global positioning system (GP S) ± Devices used to determine location

 ± Provides navigational support

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Connection Device Types

Types of modems

 ± External 

 ± Internal 

 ± P C  C ard 

 ± Wireless

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Multiplexers

Frequency Division Multiplexing

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Time Division Multiplexing Time Division Multiplexing

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Connection Services

Dial-Up services Leased lines T1, T2, T3 and T4

Digital subscriber line (DSL)

 ± Uses existing phone lines

 ± One type widely used is ADSL

C able modems

 ± Uses existing TV cable

 ± P

rovides speeds as fast as DSL at a lower cost Satellite/air connection services

 ± Seven times faster than dial-up

 ± Slower than DSL & cable modem

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Bandwidth

Measurement of the capacity of the channel

Categories

 ±

Low band w idths or Voiceband  ± Medium band 

 ± Broadband 

Used for high capacity transmission

Used by DSL, cable, and satellite

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Protocols

Set of communication rules

Standard for Internet: TC P/IP ( T ransmission

control protocol/Internet protocol  ) ± Identifies devices

 ± Reformats information

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Networks

A computer network is a communication

system

Connects two or more computers Allows information exchange

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Network Types

Local area net w orks

Home net w orks

 ±

W LAN 

Metropolitan area

net w orks

Wide area net w orks

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Network Architecture

Architecture describes how a network is

arranged

Arrangement is called topology  Types of network topology

 ± Star 

 ± Bus

 ± Ring

 ± Hierarchical 

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Star Network

Smaller computers

linked to a central unit

Central unit is called the

network hub

Control is maintained by

 polling

Return

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Bus Network

Each device handles its own communication control

There is no host computer 

Has a common connecting cable called a backbone

Return

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Ring Network

Each device is connected

to two other devices

No central file server or

computer

Useful in a decentralized

environment

Return

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Hierarchical Network

Several computers

linked to a central host

Computers are hosts to

other computers

Useful in centralized

organizations

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Strategies

Strategy is a way of coordinating the sharing

of information and

resources

Common network

strategies

 ± T erminal 

 ± C lient/server 

 ± Peer-to-peer 

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Internets and Extranets Intranets

 ± Private network within an

organization

 ± Provides information to employees

Extranets

 ± Private network that connects

organizations

 ± Used to allow suppliers and others

access

Firew alls

 ± Security system

 ± Protects against external threats

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APPLICATIONS

VoiceCommunication

- Standard Phone

Service

- Voice mail ,

recognition &

conferencing system

- Intercom System

DataCommunication

- Online Transaction &Fund Transfer Systems

- Hardware & Software

sharing

- Files & Database

Transfers

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APPLICATIONS

Text andMessaging

Communication

- E-mail

- Computer conferencing

systems

- Electronic bulletin

boards

Monitoring andControl

- Security surveillance &

monitoring

- Card-key security

systems

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THANKS

ANY QUERIES?..

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PRESENTATION BY:

NUPUR JAIN