WORLD WIDE WEB (WWW)

A Presentation ByKISHORE RAVEENDRAN

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World Wide WebᴥThe World Wide Web is an architectural

framework for accessing linked documents spread out over millions of machines all over the internet. In 10 years , it went from being a way to distribute high-energy physics data to the application that millions of people think of as being “The internet”.

ᴥ Its enormous popularity stems from the fact that it has a colorful graphical interface that is easy for beginners to use, and it provides an enormous wealth of information on almost every conceivable subject, from aardvarks to Zulus

• The World Wide Web began in 1989 at CERN, the European center for nuclear research.

• CERN has several accelerators at which large teams of scientists from the participating European countries carry out research in particle physics.

• The web grew out of the need to have large teams of internationally dispersed researchers collaborate using a constantly changing collection of reports, blueprints, drawings , photos, and other documents.

THE ORGIN

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• The initial proposal for a web of linked documents came from CERN physicist Tim Berners-Lee in March 1989.

• The first (text-based) prototype was operational 18 months later., In December 1991, a public demonstration was given at the Hypertext 91 conference in San Antonio, Texas

Tim Berners Lee

XP• Te demonstration and its attendant publicity caught the attention of other researchers , which led Marc Andreessen at the University of Illinois to start developx\ing the first graphical browser Mosaic. It was released in February in1993.

• In 1994 CERN and M.I.T signed an agreement setting up the World Wide Web Consortium (W3C),

an organization devoted to further developing the web, standardizing protocols, and encouraging interoperability between sites.

• Since then , several hundred universities and companies have joined the consortium. Although there are now more books about the web than you can shake a stick at, the best place to get up-to-date information about the Web is on the web itself.

• The Consortium’s homepage is at www.w3.org.

ARCHITECTURAL OVERVIEW

The web consist of a vast, worldwide collection of documents or Web Pages , often just called Pages for short.

Each page may contain links to other pages anywhere in the world.

The Idea of having one page point to another, now called Hypertext, was invented by a visionary M.I.T professor of Electrical Engineering, Vannevar Bush, in 1945

WWW Structure• Clients use browser application to send URIs via

HTTP to servers requesting a Web page• Web pages constructed using HTML (or other

markup language) and consist of text, graphics, sounds plus embedded files

• Servers (or caches) respond with requested Web page– Or with error message

• Client’s browser renders Web page returned by server– Page is written using Hyper Text Markup

Language (HTML)– Displaying text, graphics and sound in browser– Writing data as well– The entire system runs over standard

networking protocols (TCP/IP, DNS,…)

WEB BROWSERS

• The functionality of the WWW is based on 3 main standards:

–URL (Universal Resource Locator)

–HTML (Hypertext Markup Language)

–HTTP (Hypertext transfer Protocol)

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The Universal Resource Locator (URL)

Each page of information on the web has a unique address called the URL at which it can be found

http://faculty.uscupstate.edu/atzacheva/lecture1.html

The document can be obtained

using the Hypertext

Transfer Protocol (HTTP)

Host Name - The Name

of Web Server

Path to the Web Page

Denotes that the File is Written in

HTMLHyper Text

Markup Language

File Name

1 2 3

Protocol Host Name File Name

HTML Hyper Text Markup Language. HTML is a universal, simple language for

formatting text. It also allows embedding of graphics, and linking of documents via ‘hyperlinks’.

‘Hypertext’ documents allow readers to freely move around the document, following links to subjects of interest.

HTML is a language that is used to specify the structure of documents for retrieval across the Internet using browsers

A portion of the html document from the course web site

<ahref="../SIMS201/Fall2006/ComputerNetworks_Chapter19.ppt">Computer Networks</a>

H T T P↘ The standard Web transfer protocol is HTTP

(Hyper Text Transfer Protocols). It is used for document exchange between servers and clients (typically browsers) in the WWW.

↘ To retrieve a document, the client first sends a request to the web server and waits for a reply

↘ An HTTP daemon/service (a program that waits for http requests) on the server then handles the request and the document is sent to the client (over a connection established using TCP/IP – Transmission Control Protocol / Internet Protocol)

↘ We recall from previous lectures, that a Protocol is “Agreed upon sets of rules that provide order to a system or situation.” In this case, a set of rules/standards for communicating on the Internet.

Web client/ Server / Architecture

WEB SITES

REFERENCE

Computer Networks Andrew S . Tanenbaum INTERNET

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