The Internet andWorld Wide Web

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Objectives• Define the concept of a network• Describe the components of a network• Define Internet• Discuss how the Internet works• Understand ways to access the Internet• Define Domain Name• Describe the components of the URL• Define World Wide Web (WWW)• Describe the components of the WWW

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The InternetWhat is a network?• A collection of

computers and devices connected together via communications devices and media– Modems– Cables– Telephone lines– Satellites

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What Is a Computer Network?

• Two or more connected computers• Major components in simple network

• Client computer

• Server computer

• Network interfaces (NICs)

• Connection medium

• Network operating system

• Hub or switch connecting multiple computers in a network

• Routers• Device used to route packets of data through different

networks, ensuring that data sent gets to the correct address

Components of a Simple Computer Network

Networks in Large Companies

• Components can include:• Hundreds of local area networks (LANs) linked to

firmwide corporate network

• Various powerful servers• Web site

• Corporate intranet, extranet

• Backend systems

• Mobile wireless LANs (Wi-Fi networks)

• Videoconferencing system

• Telephone network

• Wireless cell phones

Corporate Network Infrastructure

Key Digital Networking Technologies

• Client/server computing

• Distributed computing model

• Clients linked through network controlled by network server computer

• Server sets rules of communication for network and provides every client with an address so others can find it on the network

• Has largely replaced centralized mainframe computing

• The Internet: Largest implementation of client/server computing

Key Digital Networking Technologies

• Packet switching

• Method of slicing digital messages into parcels (packets), sending packets along different communication paths as they become available, and then reassembling packets at destination

• Previous circuit-switched networks required assembly of complete point-to-point circuit

• Packet switching more efficient use of network’s communications capacity

Packet-Switched Networks and Packet Communications

Data are grouped into small packets, which are transmitted independently over various Communications channels and reassembled at their final destination.

Key Digital Networking Technologies

• TCP/IP and connectivity• Connectivity between computers enabled by protocols

• Protocols: Rules that govern transmission of information between two points

• Transmission Control Protocol/Internet Protocol (TCP/IP) • Common worldwide standard that is basis for Internet

• Department of Defense reference model for TCP/IP• Four layers

• Application layer

• Transport layer

• Internet layer

• Network interface layer

TCP/IP Reference Model

• Application Layer– Defines the protocol that applications use to exchange data – FTP,

SMTP, HTTP, HTTPS• Transport Layer

– Provides communication session management between host computers.

– Defines the level of service and status of the connection used when transporting data.

– TCP• Internet Layer

– Addressing, routing, and packaging data packets called IP diagrams – IP

• Network Interface– Specifies details of how data is physically sent through the network,

including how bits are electrically signaled by hardware devices that interface directly with a network medium, such as coaxial cable, optical fiber, or twisted-pair copper wire.

The Transmission Control Protocol/Internet Protocol (TCP/IP) Reference Model

Types of Networks

• Signals: analog vs. digital

• Modem: Translates digital signals into analog form

• Local-area networks (LANs)• Campus-area networks (CANs)

• Peer-to-peer

• Topologies: star, bus, ring

• Metropolitan and wide-area networks

• Wide-area networks (WANs)

• Metropolitan-area networks (MANs)

• Spans a city and sometimes major suburs

Network Topologies

• Twisted-pair wire (modems)

• simplest and slowest

• Coaxial cable

• Copper wires surrounded by thick insulation

• Fiber optics and optical networks

• Dense wavelength division multiplexing (DWDM)

• Wireless transmission media and devices• Microwave

• Satellites

• Cellular telephones

• Transmission speed (hertz, bandwidth)

Physical Transmission Media

The Internet What is the Internet?

• Also called the Net• A worldwide collection of

networks that links billions of businesses, government agencies, educational institutions, and individuals

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The InternetWhat are some of the services found on the Internet?

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message board

instant messaging

file transfer

e-mail

Web

chat

History of the InternetHow did the Internet originate?

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History of the InternetWhat is a host node?• Also called a host• Any computer that

directly connects to a network

• Often stores and transfers data and messages

• Provides network connections for other computers

• Four original nodes on ARPANET

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University of California at Los Angeles

University of California at

Santa Barbara

University of Utah

Stanford Research Institute

History of the InternetWhat is NSFnet?• The National Science Foundation’s network• Five supercomputer centers• Connected to ARPANET in 1986

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NSFnetARPANETThe Internet!

History of the InternetHow has this network grown?

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Today

More than 1 Billion users

1984

More than 1,000 host nodes

1969Four host nodes

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From Research Project to Information Infrastructure

Growth In The Number Of Internet Hosts

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The Web and Commercialization of the Internet

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Growth Of The World Wide Web

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New Structure for the Internet

• The Internet is organized around four network access points (NAPs).

• A different company operates each of these NAPs.

• These companies sell access to the Internet through their NAPs to organizations and businesses.

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New Structure for the InternetNetwork Access Points On The Internet Backbone

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How the Internet WorksWhat is an Internet service provider (ISP)?

• A business that has a permanent Internet connection

• Provides temporary connections to individuals and companies for free or for a fee

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History of the InternetWho provides the structure for the Internet today?

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Networks from corporations, commercial

firms, and other companies

Telephone companies

Cable companies

GovernmentSatellite companies

How the Internet WorksWhat are other service providers?

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How the Internet WorksHow can you connect to the Internet?

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High speed connection• Employees• Computers part of a local area network (LAN)• Connect to service provider through a high-speed connection

line leased from local telephone company

Dial-up access• Home or small business

• Computer, modem, regular telephone line

• Dial into an ISP or OSP

Newer high-speed technologies• Home and small business

• Digital subscriber line (DSL) – provides high-speed Internet connections over regular copper telephone line

• Cable modem- provides high-speed Internet connections through cable television network

How the Internet WorksWhat is an Internet protocol (IP) address?• Number that uniquely identifies each computer or device

connected to the Internet• Four groups of numbers, each separated by a period• Number in each group is between 0 and 255

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IP address 199.95.72.10

first part identifies network

last part identifies specific

computer

Tim Berners-Lee

• Created the World Wide Web

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Director of the World Wide Web Consortium (W3C) at MIT

How the Internet WorksWhat is a domain name?• Text version of an IP address• Components are separated by periods• Each domain name represents one or more IP addresses

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IP address 199.95.72.10

Domain name www.scsite.com

How the Internet WorksWhat is a top-level domain (TLD) abbreviation?• Identifies the type of organization associated with the

domain• Sometimes called dot com when TLD is com

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TLD Abbreviation Type of DomainCom Commercial organizations,

businesses, and companies

Edu Educational institutions

Gov Government agencies

Mil Military organizations

Net Network provider

Org Non-profit organizations

The World Wide WebWhat is a Uniform Resource Locator (URL)?

• Unique address for a Web page• Browser retrieves a Web page by using the URL• Also called a Web address• Type the URL into the address text box on the browser and press

the Enter key to display a Web page

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http://www.nationalgeographic.com/travel/index.html

address text box

address text box

The World Wide WebWhat are the parts of a URL?

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protocol domain name path

Click to view Web Linkthen click URLs

http://www.nationalgeographic.com/travel/index.html

History of the InternetWho controls the Internet?• The Internet is a public, cooperative, and independent

network• No single entity controls or owns the Internet• Several organizations advise and define standards

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World Wide Web Consortium (W3C)

• Oversees research and sets standards and guidelines

Internet2 (I2)

• Internet-related research and development project

• Develops and tests advanced Internet technologies

How the Internet WorksWhat systems control domain names?

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Internet Corporation for Assigned Names and Numbers (ICANN)

Group that assigns and controls TLDs

Domain name system (DNS)

System on the Internet that stores the domain names and their corresponding

IP addresses DNS server

Translates the domain name into its associated IP

address

The World Wide WebWhat is the World Wide Web (WWW)?• Also known as the Web• A worldwide collection of electronic documents• Each document on the Web is called a Web page• Can contain text, graphics, sound, and video• Can contain built-in connections to other documents• A Web site is a collection of related Web pages

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The World Wide WebWhat is a Web browser?• Also called a browser

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Software program that allows you to access and view Web pages

Two popular browsers for personal computers• Netscape• Internet

Explorerp. 2.9 Fig. 2-6

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The World Wide WebWhat is downloading?

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The process of receiving information, such as a Web page, onto your computer

from a server on the Internet

Can take from a few seconds to several minutes

You can speed up the display of pages by turning off the graphics and displaying only

text in most Web browsers

The World Wide WebWhat is a hyperlink?

• Also called a link• Built-in connection to

another related Web page or part of a Web page

• Allows you to obtain information in a nonlinear way

The World Wide WebHow can you identify a link?• Link can be a word, phrase, or image• Text links usually are underlined or in a color different

from the rest of the document• A graphical link may change its appearance when you

point to it

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The shape of the pointer on the screen changes to a small hand with a pointing index finger when you position it on a link or point to the link

Click the link to activate it

The World Wide WebHow do you navigate a variety of links?

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pointer

Some links display a different color when you point to them. Click the link to display its associated Web site or Web page.

pointer

Some links are underlined. Click the link to display the associated Web site or Web page.

pointer

Some links are graphical images. Click the link to display its associated Web site or Web page.

The World Wide Web

What is surfing the Web?• Links can point to an item on the same Web page, a

different Web page at the same Web site, or a separate Web page at a different Web site in another city or country

• The activity of jumping from one Web page to another is surfing

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The World Wide WebWhat is a search engine?• A software program you can use to find Web sites,

Web pages and Internet files

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Search text

A word or phrase entered in the search

engine’s text box

Also called keywords

Spider

A program that reads pages on Web sites in

order to find Web pages that contain the

search text

Also called a crawler or bot

The World Wide WebWhat is a hit?

• Any Web page name that lists as the result of a search

• The fewer ‘hits’ the better• Point of searching the web is to narrow

your search

The World Wide WebWhat is a directory?

• An organized set of topics

• Used by a search engine to aid in locating Web sites

• Each major topic has related subtopics

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The World Wide WebWhat are the six basic types of Web pages?

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advocacy Web page

informational Web page

business/marketing Web page

news Web page

personal Web page

portalWeb page

The World Wide WebWhat is an advocacy Web page?• Contains content that describes a

cause, opinion, or idea• Purpose is to convince the reader of

the validity of the cause, opinion, or idea

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The World Wide WebWhat is a business/marketing Web page?• Contains content that promotes or

sells products or services• Often allows you to purchase

products or services online

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The World Wide WebWhat is an informational Web page?

• Contains factual information• Many U.S. government sites provide information

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The World Wide WebWhat is a news Web page?

• Contains newsworthy material• Stories and articles relating to current

events, life, money, sports, and the weather

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The World Wide WebWhat is a personal Web page?

• A Web page maintained by a private individual who normally is not associated with any organization

• Reasons: job hunting and sharing life experience with the world

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The World Wide WebWhat is a portal Web page

• Often called a portal• Offers a variety of Internet services from

a single, convenient location

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The World Wide WebWhat services are often found on a portal?

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maps

stock quotes

reference tools

sports and weather

search engine

local , national, and

worldwide news

free personal

Web pages

e-mail

instant messaging

calendars

shopping malls and auctions

newsgroups or message

boards

chat rooms

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The World Wide WebWhat is a Web community?

• A Web site that joins a specific group of people with similar interests or relationships

• Usually offer special services to facilitate communication among members

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newsgroup or message

board e-mail online photo

albumschat room