The InternetThe Internet

Chapter 3

IntroductionIntroduction

Internet Stands for ‘International Network’.It is also known as ‘Network of Networks’.It connects LANs, MANs, WAN and

standalone PCs.In the recent years, the term ‘information

superhighway’ has also been applied to the Internet.

Characteristics of InternetCharacteristics of Internet

1. It has no central controlling computer or device, although there are supercomputers that from the backbone of the Net.

2. There is no limit to the number of users that can be added to it.

3. It has no geographical limitations.

Applications of Internet Applications of Internet (Advantages)(Advantages)

1. Search for information2. On-line marketing, on-line banking, on-

line learning3. Promoting business.4. Downloading information, pictures,

music, movie etc.5. E-mail, chat, video conferencing6. News and advertisement.

Basic RequirementsBasic Requirements

1. A multimedia PC with a special communication software Browser

Ex.: Internet Explorer, Netscape Navigator, Opera

2. A Modem

3. A Telephone line or ISDN line

4. An Internet account(TCP/IP) with Internet Service Provider (ISP).

ModemModemStands for Modulator-Demodulator. It is a device that converts digital signals into

analog signals that can be transmitted over a telephone line.

The modem converts an analog signal received over a communication channel back into digital signal.

BrowserBrowser

Browser is an interactive software between the users and the internet.

It accepts request from the user and passes to the web-server and in turn it receives the information and displays it on the user’s computer.Examples: Internet Explorer, Mosaic, Netscape Navigator, Opera etc.

Internet Service Providers (ISPs)Internet Service Providers (ISPs)

These are the organizations that provide the users with an access to the Internet.

Examples: America Online (AOL), Videsh Sanchar Nigam Limited (VSNL) and Satyam Online etc.

ProtocolsProtocols

As defined in the earlier chapter, a protocol is a pre-determined set of rules and procedures that must be followed by the computer connected to the internet.

Protocols are used to define – instructions for activating or terminating a transmission.

Some most popular protocols are: TCP/IP, HTTP, Gopher

1. TCP/IP1. TCP/IP(Transmission Control Protocol / Internet Protocol)(Transmission Control Protocol / Internet Protocol)

This is divided into 2 parts: TCP and IP.

TCP is responsible for transmitting data from node to node in a network.

IP checks whether the data is reaching the appropriate node to which it was directed to or not.

They both work together.

2. HTTP2. HTTP(Hypertext Transfer Protocol)(Hypertext Transfer Protocol)

It monitors the transfer of hypertext over the internet.

Hypertext is the highlighted text that activates a link to another hypertext document or a file. Ex: Slide1, Introduction, Characteristics of Internet etc.

Hypertext document is created using a special computer language called Hypertext Markup Language (HTML). It is known as Web Pages.

… … HTTPHTTP(Hypertext Transfer Protocol)(Hypertext Transfer Protocol)

URL stands for Uniform Resource Locator, which means it is a uniform (same throughout the

world) way to locate a resource (file or document) on the Internet.

The URL specifies the address of a file and every file on the Internet has a unique address.Ex: http://www.google.com, http://www.rediff.com

Web software, such as your browser, use the URL to retrieve a file from the computer on which it resides.

3. Gopher3. GopherThis protocol is designed in a series of hierarchical

menus.It is used to view or download, search and retrieve

documents over the internet.

Search EngineSearch EngineA web search engine is designed to search for

information on the World Wide Web.

The search results are generally presented in a list of results and are often called hits. Some popular search engines are : Google, Lycos, Yahoo, Indiatimes etc.

World Wide Web (WWorld Wide Web (W WW W)W)WWW was developed at CERN, the European

Laboratory for Particle Physics at Geneva in the early 1990s. It helps to distribute information over the internet.

The Web Pages contains text, graphics, forms, animations, video and sounds with links.To allow access to documents that are created using HTML or its successors.

How Data Travels on the Internet ?How Data Travels on the Internet ?The PC is connected to the internet using a

modem and a telephone / ISDN line.A request is made by the PC.

Router is a device that connects the networks, inspects this request and determines the path for the transmission to the appropriate destination computer.

… … How Data Travels on the Internet ?How Data Travels on the Internet ?The data is broken into Packets by a set of protocols.These Packets are monitored by the Repeaters,

Hubs, Bridges and Gateways while they are travel through the network.

Repeaters amplify the data signals and help them to reach remote PCs.

… … How Data Travels on the Internet ?How Data Travels on the Internet ?Hubs links groups of network together thereby

making it possible for all the terminals to communicate with each other.

… … How Data Travels on the Internet ?How Data Travels on the Internet ?

Bridges link LANs together in a WAN or MAN so that data can be properly transmitted.

… … How Data Travels on the Internet ?How Data Travels on the Internet ?Gateways translate data between one type of

network and another.When the request finally reaches its destination, the packets are read by the PC to which they were addressed to.