Lecture 1 Internet and Web Basics

7/25/2019 Lecture 1 Internet and Web Basics

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IT104N

WEB DESIGNING

Lecture 1:

Internet and Web Basics


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Overview

Internet - global network of interconnected networks

Figure 1.1The internet is a global

internetwork, a huge collection of

computer and network

interconnected so they can

exchange information.

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Understanding the Net

Network - a group of computers that are wired together so

that they can communicate with one another

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The client/server Model Web Server

stores information accessed through the Internet

Continually connected to the Internet.

Uses HTTP

Receives a request for the web page

Ie : web server, where Web pages are stored

Client a particular computer program that knows how to communicate with a

particular type of server

Connected to the Internet when needed.

Ie : web browser, or web client, such as Internet Explorer, that gives

a computer the capability to communicate with Web servers anddisplay the information stored there

Uses HTTP

Request web pages from a web server.

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Figure 1.2From your computer, you use a set of client program, each

of which accesses a different type of server computer on the net.

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HISTORY OF INTERNET


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The Birth Of ARPAnet

1957, Soviets launched a satellite called Sputnik.

It caused panic among the US military.

Nuclear attack on American cities seem possible

So, US President, Dwight D. Eisenhower put together an

organization, run by the Department of Defense calledAdvanced Research Projects Agency (ARPA)

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One of ARPAs missions was to create the network link

comps which stored security data & could be accessed by

Defense Personnel from different locations.

So, if theres a nuclear strike, the network would still be

able to function even if some of the comps were

damaged.

The network is called ARPAnet

Everything is possible with TCP/IP

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How TCP/IP work Transmission Control Protocol / Internet Protocol Large comp data are break up into smaller pieces called

packets.

They are sent out through a network of telephone lines,

connecting numerous comps. Then the pieces would be reassemble into the original

transmission after all have reached their destination.

So, if the first destination node was destroyed, the packetwould continue on to another node on the network.

The packet idea forms the basis of TCP/IP

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WEB BROWSERS ANDWEB SERVERS


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The History of Browsers In internets earlier days, users have to type in commands

from an onscreen command prompt & the info appeared in

text form only.

But WWW made it easier & much more interactive.

Instead of typing the command, users could click ahyperlink to jump from page to page.

Web browser is used to display the info in colors, pictures

and sounds.

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Tim Berners-Lee at CERN European Laboratory for

Particle Physics created the 1stweb browser, which had a

plain background & a box to type text.

1993, a new browser called Mosaic introduced by NCSA

(National Center for Supercomputing Applications) at

University of Illinois.

The co-inventor was a 22 year old student named Mark

Andreessen.

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HyperMedia browser/editor by Tim Berners-Lee

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The original Mosaic browser

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Unlike the old CERN browser, Mosaic featured a

graphical user interface, with buttons to which userscould point & click to move around.

Mark Andreessen left NCSA & started Netscape

Communications Corporation.

Netscape introduced a lot of new features, including

added support for displaying graphic images, advanced

security for web based business transactions, the abilityto open more than one web site at a time, mail & news

client programs along with its web browser

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Then, Microsoft Corporation got into the browser market

and introduced Internet Explorer.

The 1stversion had only basic features & caused errors

on many computers.

However, over a very short time, Microsoft introducedupgrades to the original Internet Explorer program that

made it almost as powerful as Netscape

1997, Netscape introduced Netscape Communicator &Microsoft introduced IE 4

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Netscape 1.0

Netscape 2.0

Netscape 4.0

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Internet Explorer 10

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INTERNET PROTOCOLS

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Protocols

Protocols are rules that describe how clients and servers

communicate with each other over a network.

Protocols with specific functions are needed:

E-mail protocolsthere are two servers involved in its smooth

functioningan incoming mail server and an outgoing mail server.

Send e-mail, Simple Mail Transfer Protocol (SMTP)

Receive e-mail, Post Office Protocol (POP, currently POP3), Internet

Message Access Protocol(IMAP).

Hypertext Transfer Protocol (HTTP)set of rules for exchanging

files such as text, graphic images, sound, video and other

multimedia files on web.

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File Transfer Protocol(FTP) a set of rules that allow files to be

exchanged between computers on the Internet.

Transmission Control Protocol/Internet Protocol (TCP/IP) TCP

and IP have different functions that work together to ensure reliablecommunication over the Internet. TCP is used together with IP to

transmit files efficiently over the Internet.

IP Address each device connected to the Internet has a unique IP

address such as IPv4 and IPv6.

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DOMAIN NAME AND URL

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DNS

is an abbreviation for Domain Name System

a system for naming computers and network services

to locate computers and services through user-friendly

names

When a user enters a DNS name, it will resolve the nameto other information associated with the name, such as an

IP address

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you must have a unique IP address that identifies your

computer on the network

takes the form of a long string of numbers separated by

dots (for example, 172.16.255.255)

Because a numeric address is difficult for people to

remember, text names or "friendly names" are used to

provide visitors with an easy-to-remember address, such

as www.microsoft.com

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URL

Uniform Resource Locator Is the web site address.

A URL is broken up by periods, called dots and can contain

letters, slashes and other punctuation.

When typing a URL, its important to type it with every dot,slash and colon correctly.

If one of the characters is typed incorrectly, youll see the

wrong page or even an error message instead of the page

you expected

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example :

http://www.mcp.com The http://portion is called theprotocol typeand

identifies the document as a Web site

Other protocol types include ftp://and telnet://

Thewww, mcp andcom portions combine to form a

fully qualified domain name

The dot (.) character joins each element of the address.

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Domain Name

The comportion of the name is called the top-leveldomain

It indicates that the page is registered to a

commercial user or that the Web host that storesthe page is a commercial institution

Name What it means

com The site or the host of the site is a commercial enterprise

net Most .netsites are a part of a network. ISP may use a .netdomain name.gov The site is owned by a governmental agency

edu Educational institutions use .eduas their domain name

mil .milis a tip that the site is owned by the military

org The site is owned by a non-profit organization

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The three letters of the domain name can be followed by

another dot and then a two-letter country code

Example,www.google.com.my

mystands for Malaysia

Other popular country codes include .uk (United Kingdom),

.jp (Japan), .au (Australia), .cn (China), .ca (Canada) and

many more

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Subdomain

A subdomain is the part of the website address before thedomain name

example, the address for WebsiteGear forum is

http://forum.websitegear.com forum is a subdomain

Subdomains are also known as the third level domains

The most commonly used subdomain is www

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Why are subdomains used?

to categorize portions of the website

Ie: poll.websitegear.com or rating.websitegear.com

used by free webhosting providers to resell web space

under their own domain name

Each member will have their subdomain, however, they all will still

share the domain name of the hosting provider

to load balance the web servers for a high traffic website

Multiple web servers are assigned different subdomains like

www.sitename.com, www2.sitename.com etc When the request comes from the browser, the load balancing

software redirects it to one of these servers

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Documents

Lecture 1 Internet and Web Basics