Computer Studies

Computer StudiesComputer Studies

Computer Communication and Networking

Table of contentsTable of contents

CConcept of computer communicationoncept of computer communication

TThe need for networkinghe need for networking

TTypes of networksypes of networks

NNetwork topologyetwork topology

MMeans of communicationeans of communication

UUse of world wide web (W W W)se of world wide web (W W W)

Concept of computer Concept of computer communicationcommunication

Concept of computer Concept of computer communicationcommunication

Telephone Line

Stage of Stage of communicationcommunication

• Encoding

• Transmission

• Decoding

m odem m odem

by telephone line

Where do each stage take

place ?

Sending device Receiving device

EncodingEncoding

• Information (e.g. data, text, voice or video) from the sending device is converted into signals which the communication medium can carry

Receiving device receive analog signal

Sending device send digital signal

010110

TransmissionTransmission

• The signals are transmitted through the medium to the receiving device

m odem m odem

by telephone line

Sending device Receiving device

Signal transmitted by telephone line

DecodingDecoding

• The signals are converted back into the information in its original form in the receiving device

Sending device send analog signal

Receiving device receive digital signal

010110

Computer NetworkComputer Network

ServerServer

ScannerScannerPrinterPrinter

WorkstationWorkstation

WorkstationWorkstation

WorkstationWorkstation

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Concept of Computer CommunicationConcept of Computer Communication

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The need for The need for networkingnetworking

Sharing of resourcesSharing of resources

Can I use the Laser Printer ? How ?

Sharing of resourcesSharing of resources

Connected

Connected

Sharing of resourcesSharing of resources

• Sharing : data, programs and hardware

• Data and software can be centrally stored in a computer acting as the file server and accessed by any computer in the network

• An expensive laser printer can be connected to a computer which serves as a print server and processing printing jobs from other computers

Communicate with one Communicate with one anotheranother

MacMac IBM PS/2IBM PS/2

Communicate with one Communicate with one anotheranother

• Different types of computers store data files using different internal representation methods

• A network operation system can automatically convert the files into the required representations before they are transferred

Centralized control and Centralized control and Better securityBetter security

The network supervisorThe network supervisor

centralized control over allfacilities and resources

better security measures

Centralized control and Centralized control and Better securityBetter security

• The network supervisor can have a centralized control over the use of all facilities and resources

• including all data, programs, disk spaces and other hardware

• better security measures can be applied

Easier software Easier software managementmanagement

Installnew

software

Use newUse newsoftwaresoftware Use new Use new

softwaresoftware

Use new softwareUse new software

ServerServer

Easier software Easier software managementmanagement

• When a new applications is developed and installed in the server, workstation can immediately use it from any computer

• upgrading or changing software is simpler because it is now stored in the single file server but not distributed among different computers

Flexibility of locationFlexibility of location

ServerServer

New ScannerNew Scanner

New PrinterNew Printer

New WorkstationNew Workstation

WorkstationWorkstation

WorkstationWorkstation

Flexibility of locationFlexibility of location

• Any computer on the network can be used to access the centralized database or the software and data in the file server

• it is fairly easy to add a workstation anywhere, relocate a computer to another site, to add a new printer or any other resources

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The Need for NetworkingThe Need for Networking

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Types of networksTypes of networks

Local Area NetworkLocal Area NetworkNNAALL NNAALL NNAALL NNAALL - Within a room, floor or building

FAST!

FAST!

Metropolitan Area NetworkMetropolitan Area NetworkNNAAMM NNAAMM NNAAMM NNAAMM - Within a large city

- Optical fibers as media

LANLAN

LANLAN

LANLAN

I Love U !I Love U too !

Wide Area NetworkWide Area NetworkNNAAWW NNAAWW NNAAWW NNAAWW - link small networks in different geographic area

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Types of NetworksTypes of Networks

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Network topologyNetwork topology

It refers to the way by which the network hardware (called nodes) are arranged and the means if data flow.

Star architectureStar architecture

HostHost

NodeNodeHello?

Transferring

Yes, I can hear you

Star architectureStar architecture

HostHost

NodeNodeHello?Hello?

I can’t work!

????

Star architectureStar architecture

HostHost

NodeNodeHello?

Transferring

Yes, I can hear you

Star architectureStar architecture

• Host fails,– whole network breaks down

• Node fails,– network not affected

• Configuration is simple

Ring architectureRing architecture

All Computer are nodes

PC1, I love U!

Oh, not for me, I will pass the message

I know u love me, but I hate u !

Ring architectureRing architecture

PC1, I love U!

????

Oh, I can’t transfer your message!!

Ring architectureRing architecture

• All computers are All computers are – NodesNodes

• If any node fails,If any node fails,– whole network break downwhole network break down

Bus architectureBus architecture

BUSBUS

NodeNode

You have to handin your homework

today!

Not my message,I won’t pick up

Not my message,I won’t pick up

Not my message,I won’t pick up

What! The deadlinehas changed??It’s my message,

I will pick it up

Bus architectureBus architecture

BUSBUS

NodeNode

You have to handin your homework

today!

Not my message,I won’t pick up

Not my message,I won’t pick up

What! The deadlinehas changed??It’s my message,

I will pick it up

What will happen?

What will happen?

Bus architectureBus architecture

• All Nodes connected to All Nodes connected to – BUSBUS

• If any node fails,If any node fails,– network not affectednetwork not affected

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Network TopologyNetwork Topology

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Means of Means of communicationcommunication

1.Direct mode transmission

Signals are transmitted to a

particular receiver

Two ways of transmission data:Two ways of transmission data:

2. Broadcast mode transmission

Signals are transmitted

to all directions

Direct mode Direct mode transmissiontransmission

1.Twisted pair wires

Cheapest transmission medium

Susceptible to local electrical noises

Usually used for short distance

connections such as telephone line

2. Coaxial cable

Fairly cheap transmission

medium

An insulating material protect the copper wire

Used for connecting a TV

set to public antennaMore reliable as

it is better insulated

3. Optical fibre

- Light passes along the coated fine cylindrical glass tubing by reflection

• Very expensive transmission medium

• Not subject to electrical disturbance

• Suited for long distances communication in high data rate

Broadcast mode transmissionBroadcast mode transmission

Ground station receive the data and beam to the satellite by microwave

Satellite will re-transmit data to another ground station

Satellite transmission

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Means of CommunicationMeans of Communication

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Use of world wide Use of world wide web(WWW)web(WWW)

The InternetThe Internet

A global network A global network link many link many networksnetworks

Can communicate Can communicate with other people or with other people or access information access information

worldwideworldwide

Use Web Browser to Use Web Browser to browse through browse through

InternetInternet

What is Web Browser ?What is Web Browser ?

Web Browser is a software to:

1. Traverse the links in the Web2. Communicate with servers3. Retrieve data

Two popular Web Two popular Web BrowsersBrowsers

1. Netscape

2. Internet Explorer

Use of Web BrowserUse of Web Browser

• You can see some shortcut key on the browser like this

• Address of Web Site is called URL(Uniform Resource Locator)

e.g. http://www.singtao.com

http://www.singtao.com

Type in the address and press enter

• After that, you can browse the home page that you wanted.

Suggestions of Interesting Suggestions of Interesting Web SitesWeb Sites

• Newspapers

– Singtao Daily News

http://www.singtao.com/

– Apple Daily News

http://apple.daily.com.hk/

• Christmas Card Web Site

http://www.comp.hkbu.edu.hk/~c6000171/xmas

http://www.casema.net/~pico/kerst/

• Meteor showerhttp://www.glink.net.hk/~sohk/leonid/enter.htm

• Games– Cow boy http://www.shinenet.com.tw

/fashion/game92/index.html

– Matching Gameshttp://personal.cityu.edu.hk/~96013494/matching/

– Gamehttp://personal.cityu.edu.hk/~96013494/fool/fool.htm

• Comics–叮噹網頁

http://home.hkstar.com/~fucp/fujiko/doraemon/dora.htm

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Use of World Wide WebUse of World Wide Web

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