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Lesson 2 Chapter 3 The Internet, Intranets, and Extranets Learning Objectives Define how the Internet works Describe the services associated with the Internet Describe the World Wide Web Define the terms intranet and extranet and discuss how organizations use them

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learning objectives
Learning Objectives
  • Define how the Internet works
  • Describe the services associated with the Internet
  • Describe the World Wide Web
  • Define the terms intranet and extranet and discuss how organizations use them
  • Identify who is using the Web to conduct business
the internet figure 7 1

Internet Networks

Linked networks that work much the same way -- they pass data around in packets, each of which carries the addresses of its sender and receiver.

The Internet (Figure 7.1)

The Internet

transmits data from one computer (called a host) to another.

use and functioning of the internet
Use and Functioning of the Internet
  • Interconnected networks
  • Global though US is the largest user
  • Internet Protocol (IP)
  • Research for a faster Internet
    • Internet2 (I2)
    • Next Generation Internet (NGI)
    • Corporate efforts
how the internet works
How the Internet Works
  • Hosts with Uniform Resource Locator (URL)
  • Routers forward packets to other networks
  • Internet Protocol Stack (TCP/IP)
    • Internet Protocol (IP)
    • Transport Control Protocol (TCP)
  • Backbones
    • One of the Internet’s high-speed, long distance communications links.
how the internet works6
How the Internet Works
  • Uniform Resource Locator (URL)
  • http://www.whitehouse.gov

World Wide Web

Domain category

Hypertext transfer protocol

Host Network Name

the internet is based on the client server model
The Internet is Based on the Client-Server Model
  • In client/server computing, processes are divided between the client and the server. This relationship is based on a series of requests and responses.
    • Client: Requests services or information from another computer (the server computer).
    • Server: Responds to the client's request by sending the results of the request back to the client computer.
the client server model









Send Request

Process Request

Read Results

Send Back Results

The Client-Server Model

This diagram illustrates the relationship between client and server computers. The client requests information; the server processes the request and sends a response back to the client.

examples of client server transactions
Examples of Client Server Transactions
  • FTP (file transfer protocol) - An FTP client program contacts an FTP server and requests the transfer of a file; the FTP server responds by transferring the file to the client.
  • WWW (World Wide Web) - In this case the client program is a browser. A browser requests the contents of a web page and displays the results on the user's computer.
  • E-MAIL - A mail client program enables the user to interact with a server in order to access, read and send electronic mail messages.
packets the internet letter




Instruction Fields:


Packets: The Internet “Letter”
what is a packet
What is a Packet?

A packet is a single unit, or "package", of data that is sent across a network. Data is broken into packets before it is sent across the Internet. Types of data that are sent across the Internet using packets include:

  • E-mail messages
  • Files, via File Transfer Protocol (FTP)
  • Web pages, via the World Wide Web (WWW)
parts of the packet




Instruction Fields:


Parts of the Packet

The HEADER of a packet contains both the originating and destination IP (Internet Protocol) address. The header also contains coding to handle transmission errors and keep packets flowing. Routers use the data in the header to get the packet to the correct address and to reassemble it at the destination.

The DATA portion

of the packet contains the e-mail text, the web page information, or the contents of the


transmission control protocol internet protocol tcp ip
Transmission Control Protocol/Internet Protocol (TCP/IP )
  • TCP/IP is a collection of protocols, or rules, that govern the way data travels from one machine to another across networks.
  • The Internet is based on TCP/IP.


internet protocol
Internet Protocol
  • Determines how much data can fit into a single packet
  • Breaks the data into packets.
  • Places header information into the packet, enabling the packet to be forwarded from router to router until it reaches the final destination..
packet switching example17

Hi Bob!

Hi Bob!

Hi Bob!

Hi Bob!

Hi Bob!

Hi Bob!

Hi Bob!

Hi Bob!

Hi Bob!

Packet Switching Example
packet switching example18

Hi Bob!

Hi Bob!

Hi Bob!

Hi Bob!

Hi Bob!

Packet Switching Example




packet switching example20

Hi Bob!

Hi Bob!

Hi Bob!

Hi Bob!

Hi Bob!

Hi Bob!

Hi Bob!

Hi Bob!

Packet Switching Example
u s top level domain affiliations
U.S. Top-Level Domain Affiliations

Affiliation ID Affiliation

arts cultural and entertainment activities

com business organizations

edu educational sites

firm businesses and firms

gov government sites

info information service providers

mil military sites

nom individuals

net networking organizations

org organizations

rec recreational activities

store businesses offering goods for purchase

web entities related to World Wide Web activities

net networking organizations

internet service providers isps
Internet Service Providers (ISPs)
  • Provide Internet access to account holders
  • Monthly fee varies
  • Some are free
internet service providers
Internet Service Providers

Internet Service Provider Web Address

AT&T WorldNet Service www.att.com

Digex, Inc. www.digex.net

GTE Internetworking www.gte.net

IBM Internet Connection www.ibm.net

MCI Internet www.mci2000.com

NetCom On-Line Communication Services www.netcom.com

PSINet, Inc. www.psinet.com

Sprint Internet Services www.sprint.net

Uunet Technologies, Inc. www.us.uu.net

internet services
Internet Services
  • E-mail (Electronic mail)
    • Can include images, attachments, or HTML
    • Routed by gateways and routers
  • Telnet: remote login
  • FTP: file transfer
internet services26
Internet Services
  • Chat rooms: allow interactive conversations
  • Instant Messaging: online, real-time communication over the Internet
  • Videoconferencing
  • Internet phone
internet services27
Internet Services
  • Content streaming: transfers multimedia files continuously so users can view them in real-time
  • Music, radio & video
  • 3-D Internet sites
the www is just a part of the internet
The WWW is Just a Part of the Internet
  • The World Wide Web, also referred to as the WWW and "the Web," is the universe of information available via hypertext transfer protocol (HTTP).
  • The World Wide Web and HTTP:
    • allow you to create "links" from one piece of information to another;
    • can incorporate references to sounds, graphics, and movies, etc.;
    • "understand" other Internet protocols, such as ftp, gopher, and telnet.
www pages use hyperlinks
WWW Pages use Hyperlinks
  • The Web presents information as a series of "documents," often referred to as web pages, that are prepared using the Hypertext Markup Language (HTML).
  • Using HTML, the document's author can specially code sections of the document to "point" to other information resources. These specially coded sections are referred to as hypertext links. Users viewing the webpage can select the hypertext link and retrieve or connect to the information resource that the link points to.

Library Catalog



Software Repository




gopher site w/ images & sounds


the world wide web31
The World Wide Web
  • A collection of tens of thousands of independently-owned computers that work together as one in an Internet service.
  • Uses a menu-based approach and hyperlink technology in a client/server topology.


Tools that connect the data on Web pages, allowing users to access topics in whatever order they wish.

Home Page

The cover page for a Web site that has graphics, titles, and black and blue text.

uniform resource locators url identify sources of data on the internet
Uniform Resource Locators (URL) Identify Sources of Data on The Internet
  • A URL identifies a particular Internet resource. e.g. a Web page, a gopher server, a library catalog, an image, or a text file.
  • URLs represent a standardized addressing scheme for Internet resources. The basic structure of a URL is hierarchical moving from left to right:

protocol://server-name.domain-name.top-level domain:



    • http://www.healthyway.com:8080/exercise/mtbike.html
    • gopher://gopher.state.edu/
    • ftp://ftp.company.com/
several interesting web sites
Several Interesting Web Sites

Library of Congress http://lcweb.loc.gov

PointCast http://www.pointcast.com

In-Box Direct http://www.netscape.com

Online Career Center http://occ.com

New York Times http://www.nytimes.com

Project Gutenberg http://www.gutenberg.org

Sportsline USA http://www.sportsline.com

White House http://www.whitehouse.gov

MIT CS Lab http://www.lcs.mit.edu

The Wall Street Journal http://www.wsj.com

web terminology
Web Terminology
  • Web Server: Computer that stores web pages.
  • Web Browser
    • Software that creates a unique hypermedia-based menu on your computer screen and provides a graphical interface to the Web.
  • Web Page
    • A screen of information sent to a requesting user and presented through a browser.
  • Applet
    • A small program embedded in Web pages
  • Search engines
    • Programs to find web pages of interest.
internet services35
Internet Services
  • Shopping on the Web
  • Bots: web search tools
  • Web Auctions
  • Office on the web
  • aka Push Technology
  • Consolidates information according to a user’s profile & displays in the browser
intranets and extranets
Intranets and Extranets
  • Intranet
    • An internal corporate network built using Internet and World Wide Web standards and products that allows employees of an organization to gain access to corporate information.
  • Extranet
    • A network based on Web technologies that links selected resources of the intranet of a company with its customers, suppliers, or other business partners.