Class Slides 2 - Network-Internet-Email

8/6/2019 Class Slides 2 - Network-Internet-Email

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ALM AY DeLC, SEUSL1

COMPUTER:COMPUTER:NETWORK &NETWORK &

INTERNETINTERNET


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ALM AY DeLC,SEUSL 2

COMPUTER NETWORK

nel;nthHf; vd;gJ gy fk;g;A+l;lHfis xd;whf ,izf;fTk;. fk;g;A+l;lupd;ntspaPl;Lf; fUtpfisg; gfpuTk; A+rHfisf; fl;Lg;gLj;jp mjpfhuk;toq;fTk; midj;Jf; fk;g;A+l;lHfisAk; xNu ,lj;jpy; ,Ue;J nfhz;L Ml;rp

nra;aTk; Md xU njhopy;El;gkhFk;. ,d;lHnel; vd;gJnel;nthHf;Ffsdhy; mike;j xU nel;nthHf; MFk;. xU fk;g;A+l;liukw;nwhU fk;g;A+l;lNuhL ,izf;fpd;wnghOJ ,U fk;g;A+l;lHfSk;vg;gb njhlHG nfhs;s Ntz;Lk;. vjidj; njhlHG nfhs;s Ntz;Lk;.vd;gijf; $Wfpd;w jfty; njhlHG tpjpfis GNuhl;NlhNfhy;fs;

(Protocol) vd;wiof;fyhk;.


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ALM AY DeLC,SEUSL 3

How Does a

Network Work?

IP Address Postal Address

130.184.237.189 South Eastern University of Sri LankaUniversity Park,

Oluvil,Sri Lanka.


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ALM AY DeLC,SEUSL 4

COMPUTER

NETWORK


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Overall viewof

Networktypes

ALM AY DeLC,SEUSL 5


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Text based

Transaction

ALM AY DeLC,SEUSL 6


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Cabling and LAN

Connection

ALM AY DeLC,SEUSL 7


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Sending Data Overa

Telephone Line

ALM AY DeLC,SEUSL 8


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Networking

Fundamentals

ALM AY DeLC,SEUSL 9

Network consists of: Servers provides services

Clients requests services Peers both requests and provides services

Types of networks

Server-centric networks Peer-to-peernetworks


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Network

Relationships

ALM AY DeLC,SEUSL 10

Peer-to-peer

Client/server


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Television Company

using SatelliteSystem



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Nel;nthh;f; -

,d;lh;nel;

,uz;L my;yJ mjw;F Nkyhd fk;g;A+l;lh;fis ,izg;gijNa nel;nthh;f;vd;gh; fk;g;A+l;lh;fis ,izj;J nel;nthh;f; Vw;gLj;Jtjd; Kf;fpa Nehf;fk;

rhjzq;fspd; (resources) gq;fPL

jfty;fspd; gq;fPL fUj;Jg; ghpkhw;wk;

nel;nthh;f;Ffspd; nel;nthh;f;if ,d;lh;nel; vd;ghh;fs;

nel;nthh;f;fpd; Kf;fpa Fwpf;Nfhs; tpiy cah;e;j guhkhpg;G kpFe;jrhjdq;fis nel;nthh;f;fpy; cs;s vy;NyhUk; gad;gLj;j Ntz;Lk; vd;gNj

Eg: tpiy cah;e;j Nyrh; gphpd;lh; xd;iw nel;nthh;f;fpy; ,izj;J ahh;

Ntz;LkhdhYk; mijg; gad;gLj;Jk;gb nra;ayhk;.


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COMPUTER NETWORK

Modems A modem is a device that converts digital data originating from a computer to

analog signals used by voice communication networks, such as the telephone

system. A modem may also convert analogue data originating from a (say, a

telephone line) to digital data for use by a computer.


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Advantage and

Disadvantage


ADVANTAGES OF COMPUTER NETWORKS

Sharing of expensive resources (e.g., A Laser printer, DVD drive &Software applications)

Sharing of data bases and other software

Communication among different computer systems Transfer of multimedia files

Faster transfer of data

DISADVANTAGES OF COMPUTER NETWORKS

Initial cost Security of information (viruses, hackers, ..)

System failures


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COMPUTER NETWORK

TRANSMISSION MEDIAUnshielded Twisted Pair (UTP) Cable

/Shielded Twisted Pair (STP) Cable


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COMPUTER NETWORK

Coaxial Cable

Fibre Optic Cable


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Internet

,d;lHnel; vd;gJ> cyf mstpYs;s ,d;gHNk\d; i`Nt];(Information Highways) kw;Wk; hpNrhH];fspd;(Recourse) xU FO MFk;.

,d;lh;nel;by; tpj;jpahrkhd fk;g;A+l;lh;fis itj;jpUg;gth;fs;>tpj;jpahrkhd trjpfis (vyf;l;uhdpf; nkapy;> b];f\d; F&g;>Nfk;]; Nghd;wtw;iw) mDgtpf;fyhk;

cynfq;fpYk; cs;s gy ,yl;rf;fdf;fhd fk;gpA+l;lHfspd;xUq;fpidg;Ng ,d;lHndl; vd miof;fg;gLfpd;wJ. Networkfspd; ,izg;G vd;w thHj;ijapy; ,Ue;Jjhd; Internet te;jJ.


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Internet

,d;lHnel; vd;gJ nel;nthHf;Ffsdhy; mike;j xU nel;nthHf;MFk;.


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,d;lh;nel; tuyhW

,d;lHnel; ,d;iwa cyif> jftiyr; rhHe;j r%fkhf khw;wpepw;fpwJ. 1965k; Mz;L MHg;gh nel; (ARPANET) ,-

nkapy; Nritahfg; ghpzkpj;jJ. gpwF 1980 f;fpilapy;

Ne\dy; rapd;]; /gTz;Nl\d; (Notational ScienceFoundation) vd;w mikg;gpd; cjtpahy;> vd;v];v/nel;

(NSFNET) vd;gJ cjakhdJ. ,d;iwf;F ,d;lHnel; ,uz;L

tifahfg; gad;gLj;jg;gl;L tUfp;d;wJ.

vd;v];v/nel; (NSFNET)

fkH\pay; ,d;lHnel; (Commercial Internet)


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Internet & Email

US Government vd;v];v/nel; (NSFNET) il nrhe;jkhf;fpgad;gLj;jp tUfpd;wJ.

fkH\pay; ,d;lHnel;> ,d;lHnel; rHtP]; GiuitlHfisf; (InternetService Provides) nfhz;L ,af;fg;gLfpd;wJ.

1991k; Mz;L rpd;dQ; rpwpa fkH\pay; nel;nthHf;Ffs;

vy;yhk;> Commercial Internet Exchange vd;w mikg;igepWtpd.


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Internet

,d;lHnel; vd;gJ ve;jnthU jdpeghpdhYk; ,af;fg;gLtjpy;iy.,d;lHnel;bDs; xt;nthU epWtdKk;> jd;idj;jhNdIf;fpakhf;fpf; nfhs;fpd;wJ. mt;thW nra;tjd; %yk;>

epWtdj;jpd; eilKiwfs;> cyfj;juk; tha;e;jjhf khwpepw;fpd;;wd. ,d;lHnel;by;> Membership gzk; ,y;iy.ve;jtpj nrd;rhH\pg;gk; (Censorship) ,y;iy.

,d;lHnel; vd;[pdPahpq; lh];f; /NghH]; (InternetEngineering Task Force) vd;w mikg;ghdJ> ,d;lHnel;bd;

Nkyhz;ik (Management), Mg;Nu\d; (Operation) kw;Wk;tsh;r;rpf;F cWJizahf ,Uf;fpd;wJ.


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Internet

,d;lHnel; hpNrHr; lh];f;/NghH]; (Internet Research TaskForce) vd;gJ ePz;l ehisa Muha;r;rp gpur;rpidfisAk;>

njhopy; El;g gpur;rpidfisAk; Muha cjTfpwJ. ,d;lHnel;

MHr;rpnlf;rH NghHl; (Internet Architecture Board) MdJ>,d;lHnel; tbtikg;gpd; tsHr;rpf;F kpfTk; NgUjtpahf cs;sJ.

,d;lHnel; rHtP]; GiuitlH> xt;nthUtUf;Fk;> nel;NthHf;vd;l;hp ghapd;l;fis (Network Entry Point) nfhz;bUf;Fk;.

,d;lh;nel; rHtP]; GiuitlH Jiz nfhz;L> gy NtWgl;l fndf;\d;fis

mikj;Jf;nfhs;s KbAk;.


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Internet & Email

nlypNghd; fndf;\dpd; %yk; kl;Lkh, Internet Connectionid, cUthf;f KbAk;?.

nlbf;Nfl;ll; fndf;\d; (Dedicated Connection) vd;gJ 57kbps my;yJ 128 kbps Ntfj;jpy; cs;s yP];l; iyd; (Leased

Line),

Kbps (Kilo bytes per second) vd;gJ xU tpehbapy; xUfpNyh igl; jftiy mDg;Gk; Ntfj;ij Fwpf;Fk; msthFk;.


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,d;lh;nel;ilg;

gad;gLj;JtJ vg;gb? ,d;lh;nel;bidg; gad;gLj;JtJ vd;gJ cq;fs; fk;g;A+l;lh; Kd; mkh;e;J

GNuhf;fpuhk; xd;iw ,af;fp rpy nray;fisr; nra;tiijf; Fwpf;Fk;

cq;fSf;F VjhtJ vyf;l;uhdpf; nkapy; te;Js;sjh vd;gijf; ftdpAq;fs;te;jpUe;jhy; mtw;iwg; gbj;J tpUg;gkpUe;jhy; gjpy; mspf;fyhk;ahUf;fhtJ Gjpa nkapy; mDg;g tpUk;gpdhy; nkapy; jahhpj;J mijmDg;gyhk;.

Discussion group Nrh;e;J nfhz;L eifr;Ritj; JZf;Ffs;Nghd;wtw;iwg; ghh;itaplyhk; rpdpkh gw;wpa nra;jpfisg;ghh;f;fyhk;> rkay; Fwpg;G Nghd;wtw;iwg; gw;wp tpthjpf;f VjhtJFOtpy; Nruyhk;.

tpisahl;L kUj;Jtk; tpQ;Qhdk; mutpay;> tuyhW> ,ir vd;W

vijg;gw;wpa tpguq;fisj; Njlyhk;.


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,d;lh;nel; ,ytrkh?

,d;lh;nel;by; ahUk; Eioayhk;. Mjpy; cs;sijg; ghh;itapl ve;j fl;lzKk; fpilahJMdhy; ,d;lh;nel;by; Eioa ePq;fs; fl;lzk; fl;l Ntz;Lk;

,d;lh;nel; trjpia toq;Ffpw epWtdq;fs; cz;L ,tw;iw ,d;lh;nel; rh;tp];Gnuhitlh; (Internet Service Provider) vd;gh; RUf;fkhfISP vdyhk;.

,th;fsplk; gzk; fl;b re;jhjhuh; Mf Ntz;Lk;.,d;lh;nel;il ahh; gad;gLj;Jfpwhh;fs;?

,d;lh;nel;il vy;NyhUk; gad;gLj;Jfpwhh;fs; vy;yhj; Jiwiar; Nrh;e;jth;fSk;gad;gLj;Jfpwhh;fs; nghJthf ,d;lh;nel;ilg;gad;gLj;Jgth;fs;.

gy;fiyf; fof kw;Wk; gs;sp Mrphpah;fs;> khzt khztpfs; tpQ;Qhdpfs; kUj;Jtj;Jiw ty;Yeh;fs;

fk;gdp eph;thfpfs; muR mYtyh;fs; E}yff; fz;fhzpg;gth;fs;


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Internet & Email

The Internet - What is on it

Electronic post offices

Online libraries with books and

periodicals Chat rooms

Online shopping

Movie Previews

Radio and TV stations fromaround the world

News And more


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ALM AY FMC,SEUSL 27

Making Connections

There's more than one way to access the World Wide Web.

Many people browse the Web from their desktop computer

with the help of a modem and telephone line

Modems come in different speeds and are measured in BPSor Bits Per Second. A 56 Kbps modem transmits data at

speeds up to 56,000 bits per second.


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ALM AY FMC,SEUSL 28

Making Connections

Contd..

Other Connecting devices -

Modem/Dial-Up connection

Broadband Cable

DSL Satellite Broadband

ISDN and T-Line

Leased lines

WirelessThe next step

Cost Vs Speed andavailability


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ALM AY FMC,SEUSL 29

Making Connections

Contd..

What is an ISP andhow to get one

Connects you to theInternet

Choosing an Internetservice provider


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,d;lh;nel; - njhpe;J nfhs;s Ntz;ba

nlf;dpfy; ;tpguq;fs;

,d;lh;nel;ilj; jpwikahfg; gad;Lj;j> ,d;lh;nel;ilg; gw;wpAk; mJ vt;thW,aq;Ffpd;wJ vd;gijg; gw;wpAk; njhpe;jpUf;f Ntz;Lk;.

Nel;nthh;f; kw;Wk; ,d;lh;nel;

Nyd; mikg;G Client /Server

N`h];l; kw;Wk; nlh;kpdy;

TCP/IP

Upload /Download


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Internet Client & Server


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http://www.domain.com/html2/..

WWW address

(URL)

Hyper Text

Transferprotocol

(ftp://

gopher://)

WorldWide

Webserver

indicator

Internet Service

Provider (server)

Pathsymbol

(forwardslash)

htmlhomepage


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Computers andthe

Internet



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The Microsoft Internet

Explorerwindow



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Internet & Email

A WEB SITE ADDRESS VS. AN E-MAIL ADDRESS

A Web Site address is a location for the information you arelooking for. Ex : http://www.seu.ac.lk , http://www.google.com


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Internet & Email

E-mail addresses are characterized by the @ symbol. For example ayahoo mail e-mail addresses may look like this: [email protected].

ACCESSING THE INTERNET FROM A PC

You can access the internet from the desktop of your computer:

Double-click on the Internet Explorer icon:


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Internet & Email

HOW TO MOVE AROUND THE INTERNET

The World Wide Web (WWW) is most often called the Web.

The Web is a network of computers all over the world.

All the computers in the Web can communicate with each other. All the computers use a communication standard called HTTP.


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Internet & Email

How does the WWW work? Web information is stored in

documents called Web pages.

Web pages are files stored oncomputers called Web servers.

Computers reading the Web pagesare called Web clients.

Web clients view the pages with aprogram called a Web browser.

Popular browsers are InternetExplorer and Netscape Navigator.


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Internet & Email

HOW TO MOVE AROUND THE

INTERNET....

1. Log on to the Internet. We will

first go through the basic

outline of what a web pagelooks like:

When you double click onthe Explorer icon, you

should see something like

this:

This is a webpage displayed

by Internet Explorer.


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Internet & Email

SEARCHING THE INTERNET The best way to access a specific website is entering the URL address

directly into the address box. However, it is often difficult to remember

full long and complex web addresses. An easier way to find sites is by searching for them using a web-based

search engine.

Here we will use the Google search engine.

1. Enterwww.google.com into your web address box:2. Push enter.


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Internet & Email

The Google Search Engine


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Internet & Email

The best way to use the search engine is by entering specific words into thesearch box.

For example, to search for websites containing information about E-commerce, enter E-Commerce:

These are called keywords. Click the Google Search button todisplay a list of sites containing the words E-Commerce.


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Internet & Email


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Internet & Email

Sites are ranked by how many times each word is repeated.

The first sites are not always the best, it is recommended that youread the descriptions provided to get a better idea of what each

site contains. There are often many diverse sites available.

Some clues for managing searches:

Most search engines show you how many websites it found for your keywords.Google displays it on the top right:

At the bottom of the page you can access more search results:


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Searching the Internet

Somecluesfor

managingsearches: Most search enginesshow you how many websites it found for

yourkeywords. Google displays it on the topright:

At thebottom of thepage youcan access moresearch results:

Oryoucan try anothersearch:


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Many search engineswill allow tosearch for imagesas

well as information.

Imagesearchescan beused to find photos, drawings,

clipart, maps,orothernon-text objects.

To find an image in Google,click the images

tabon the main page:

Searching

for Images


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Searching the Internet

When youenterasearch category in aGoogle imagesearch,pages

ofselectionsare displayed:

Clickon an image tosee it

aloneand accessa full sizeimage.

Searching

for Images


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Using

Images When you find apicture you

want, youcan save it to the desktop

by

right-clicking the imageand

pressing saveas. . .A saveboxwill open. Make

sure the Desktop isvisible

in the save inboxand

press save. Now youcan copy and

paste the imageonto

documents.


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,d;lHnel;by; cs;s> epWtd Domain fspy;>

gov - murhq;f VnId;rpfisAk;> mil- kpypl;lhp VnId;rpfisAk;>

edu - fy;tp epWtdq;fisAk;> com - tpahghu epWtdq;fisAk;> net- Administrative jsq;fisAk;> org - ,yhgkpy;yhj epWQtdq;fisAk;> us - Aidl;nll; ];Nll;i]Ak;>

in - ,e;jpahtpidAk; lk - ,yq;ifapidAk;> au - M];jpNuypahtpidAk; Fwpf;fpd;wJ.


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ImpactoftheInternet

Vast network

Source of social and economic revolution of

global proportions Provides a window on the world and access to

wide range of educational, economic and social

information

Essential component of e-commerce



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ImpactoftheInternet...

Makes economic activity more efficient

Extends social interaction

Generates large productivity gains Examples:

- food giant Nestl receives all orders from

supermarkets over the Internet

- by using on-line networks to optimise delivery

routes, shipping company UPS saved 12 million

litres of fuel in 2006 from nearly 100,000 trucks


Class Slides 2 - Network-Internet-Email

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