the internet intranets and extranets l.
Skip this Video
Loading SlideShow in 5 Seconds..
The Internet, Intranets, and Extranets PowerPoint Presentation
Download Presentation
The Internet, Intranets, and Extranets

Loading in 2 Seconds...

play fullscreen
1 / 86

The Internet, Intranets, and Extranets - PowerPoint PPT Presentation

  • Uploaded on

The Internet, Intranets, and Extranets Chapter 7 Ch. 7 The Internet, Intranets, and Extranets The Internet History of the Internet How the Internet works Internet services The World Wide Web Web publishing Intranet and extranet several issues associated with the use of networks Internet

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

The Internet, Intranets, and Extranets

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
ch 7 the internet intranets and extranets
Ch. 7 The Internet, Intranets, and Extranets
  • The Internet
  • History of the Internet
  • How the Internet works
  • Internet services
  • The World Wide Web
  • Web publishing
  • Intranet and extranet
  • several issues associated with the use of networks
  • Also called the Net
  • A worldwide collection of networks
  • These networks are connected together using routers
  • Internet Protocol(IP)
  • No single point of registration and control for the network
history of the internet
History of the Internet
    • Networking project by Pentagon’s Advanced Research Projects Agency (ARPA)
    • Goal:
      • To allow scientists at different locations to share information and work together on military and scientific projects
      • To function even if part of the network were disabled or destroyed
  • Became functional in September 1969
  • Four original nodes on ARPANET
    • University of California at LA, the Stanford Research Institute, the University of California at Santa Barbara, and the University of Utah
  • NSFnet:
    • The National Science Foundation’s network
    • Connected to ARPANET in 1986
  • Today more than 100 million host nodes
how the internet works7
How the Internet Works
  • Hosts
  • Routers forward packets to other networks
  • Internet Protocol Stack (TCP/IP)
    • Internet Protocol (IP)
    • Transport Control Protocol (TCP)
  • Backbones
    • Inner structure of the Internet
    • Communications lines that carry the heaviest amount of traffic
the operation of the internet
The Operation of the Internet
  • Packets of information flow between machines governed by common rules (protocols):
    • Internet protocol (IP)
    • Transport control protocol (TCP)
  • Internet is a packet-switching network
    • Messages are decomposed into packets, containing part of the message, plus information on the sending and receiving machines and how the packet relates to the other packets
    • Packets travel independently and possibly on different routes through the Internet
    • Packets are reassembled into the message at the receiving machine.
how the internet works9
What 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

last part identifies specific computer

first part identifies network

How the Internet Works

IP address

how the internet works10
What is a domain name?

Text version of an IP address

Components are separated by periods

Each domain name represents one or more IP addresses

How the Internet Works

IP address

Domain name

how the internet works11
How the Internet Works
  • Uniform Resource Locator (URL)
    • An assigned address for each computer on the Internet

Domain category

World Wide Web



Hypertext transfer protocol

Host Network Name

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

Regional ISP: Provides access to the Internet through one or more telephone numbers local to a specific geographic location

National ISP: Provides local telephone numbers in most major cities and towns nationwide. May also provide a toll-free number

how might data travel the internet using a telephone line connection
How might data travel the Internet using a telephone line connection?

1:You initiate an action to request data from the Internet.

2: A modem converts the digital signals from the computer into analog signals, which are understood by telephone lines.

3: Data (request) travels through telephone lines to a local ISP.

4: Data may pass through one or more routers before reaching its final destination.

5: The regional ISP uses lines, leased from a telephone company, to send data to a national ISP.

6: The national ISP routes data across the country to another national ISP.

7: Data moves from a national ISP to a local ISP and then to a destination server.

8: The server retrieves the requested data and sends it back through the Internet backbone to your computer.

internet connection methods
Internet connection methods
  • LAN whose server is an Internet host
  • SLIP or PPP via dial-up access
    • SLIP or PPP- communications protocols enable packets to move across telephone lines
  • On-line service such as AOL, MSN, or Prodigy
internet services communications
E-mail – electronic messaging

USENET newsgroups – forums that collect groups of messages from users based on common themes

LISTSERV – distributes email messages to all subscribers

Chatting – live, interactive, written conversations based on topic groups

Instant messaging – instant text messaging between Internet users

Telnet – user on one computer doing work on another computer

Internet telephony – conducting voice conversations over the Internet

Internet fax – real time document transmittal

Streaming audio and video

Internet Services - Communications
internet services information retrieval
File Transfer Protocol (FTP) – electronic transfer of files from one computer to another

Archie – tools to enable searching for files at FTP sites

Gophers – menu-driven information search tool

Veronica – text search through Gopher sites

Wide Area Information Servers (WAIS) – database search tool

Internet Services – Information Retrieval
how does an e mail message travel
How does an e-mail message travel?
  • Using e-mail software, you create and send a message.
  • Your software contacts software on your service provider’s mail server.
  • Software on the mail server determines the best route for the data and sends the message, which travels along Internet routers to the recipient’s mail server.
  • The mail server transfers the message to a POP3 server.

5 When the recipient uses e-mail software to checkfor e-mail messages, the message transfers from the POP3 server to the recipient’s computer.

What is a POP server?

Post office protocol server

  • When a message arrives at the recipient’s mail server, the message transfers to a POP server
  • POP server holds an e-mail message until the recipient retrieves it with his or her e-mail software
  • POP3 is the newest version
the world wide web21
The World Wide Web
  • An application that uses the Internet transport functions
  • A system with universally accepted standards for storing, retrieving, formatting, and displaying information via a client/server architecture
  • Based on HTML -standard hypertext language used in Web
  • Handles text, hypermedia, graphics, and sound
brief history of the web
Brief History of the Web

1945 Vannevar Bush (1945) -“The Memex”

  • A desk containing a micro-film reader and stores of film that would serve as the equivalent of an entire research library.
  • It would allow different items in the microfilm collection to be linked together and annotated by the reader
  • Bush, Vannevar. "As We May Think." Atlantic Monthly (July, 1945)


  • Ted Nelson coins the word Hypertext
  • Doug Engelbart prototypes an “oNLine System”(NLS) which does hypertext browsing editing, email, and so on. He invents the mouse for this purpose.


  • Tim Berners-Lee writes a notebook program which allows links to be made between arbitrary nodes.


  • The WWW was freely usable by anyone
  • Personal library with links
    • Links to information
    • Links to own thoughts
  • Operated by association (and buttons)
  • Trails
    • Associations of thoughts
    • Dynamic
    • Shareable
    • Intricacy of trails
    • Web of trails

Picture from

the world wide web25
The World Wide Web
  • Home Page - a text and graphical screen display; first, introductory page in a web site
  • Web Site - all the pages of a company or individual
  • Hyperlinks - ways to link and navigate around the pages on a web site
  • Webmaster - the person in charge of a Web site
  • Browsers - graphical software that enables WWW users to request and view web documents
  • Uniform Resource Locator (URL) - points to the address of a specific resource on the Web
  • Hypertext Transport Protocol (HTTP) - communications standard used to transfer pages across the WWW portion of the Internet
Web browser

Also called a browser

  • Software program that allows you to access and view Web pages
  • Two popular browsers for personal computers
    • Netscape
    • Internet Explorer
web site navigation
Web Site Navigation
  • Web site organization and navigation design is up to the developers
  • Navigation allows users to
    • Know where they are
    • Know where they can go
  • Approaches
    • TOC/Index model
    • Site Map
  • Navigation Rules
    • Consistency
    • Ease of use
    • Indicate current location
    • Always be able to go home
Uniform Resource Locator (URL)



hypertext transfer protocol, the communications standard used to transfer pages on the Web

Unique address for a Web page

Browser retrieves a Web page by using the URL

Also called a Web address

domain name system
Domain Name System







Domain Name Server















domain name server
Domain Name Server



Server 932.562.85.9 976.899.86.5





web server
A computer that delivers (serves) Web pages you request

Computer running web server software

Contains WWW directories

Web Server







finding information on the web
Finding Information on the Web
  • Understanding Information Discovery Tools
  • Subject Guides
  • Search Engines
    • A software program you can use to find Web sites, Web pages and Internet files
    • A Web search tool that helps you find relevant web pages
search tools
Search Tools
  • Type a phrase into a search box on a “web form”
  • Possibly restrict search using
    • Search operators
      • Inclusion operators
      • Exclusion operators
    • Wildcards
    • Boolean
  • Submit the form
  • Get candidate web pages
typical crawler based search engine architecture
Typical crawler-based search engine architecture



Query Engine




Web servers

search technology

Search form

Search Engine

Cat http://djfidj

Dog http://dkjdjf




Search Technology



Index of words, phrases

Metadata, and URLs





Result list

of URLs

types of search engines
Types of Search Engines
  • Directories
    • hierarchically organized indexes that allow you to browse through lists of web sites by category or subject
  • search engines
    • create a database of sites using robots or spiders
  • meta-search engines
    • query multiple search engines simultaneously and return a complete set of hits
  • Specialized search engines
    • Create a database of sites on a specific topic using robots or spiders
What 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

  • Yahoo

  • Librarians’ Index to the Internet

search engines
Search Engines
  • Hotbot

  • AltaVista

  • Northern Light

  • Google

search engine components
Search Engine Components
  • Spider (called as crawler or bot)
    • A program that reads pages on Web sites in order to find Web pages that contain the search text
    • The spider visits a web page, reads it, and then follows links to other pages within the site.
    • The spider returns to the site on a regular basis, such as every month or two, to look for changes.
  • Index/Database
    • Everything the spider finds goes into the index. The index, called the catalog, is like a giant book containing a copy of every web page that the spider finds
  • Search engine software
    • The program that sifts through the millions of pages recorded in the index to find matches to a search and rank them in order of what it believes is most relevant.
meta search engines
Meta-Search Engines
  • MetaCrawler

  • ProFusion

  • Mamma

when to use what
Subject Directories

üHave a broad topic

üLook for a collection of sites recommended by experts

üDon’t want a list of low-content documents

Search Engines

üHave a narrow or unique topic or idea to research

üLook for a specific site

üSearch for particular types of documents, file types, source locations, languages, date last modified, etc.

When to use what?
specialized search engines
Specialized Search Engines
  • Career Mosaic

  • Diseases, Disorders and related topics

  • The Day in History


search engine comparison
Search Engine Comparison
  • Search engine comparison chart

  • Search features chart

examining a search engine
Examining a Search Engine
  • Before you use a search engine, you need consciously examine following aspects:
    • The size and content of the database
    • How the search engine index web pages: what elements of a web page are searched
    • Its Retrieval Algorithms: what exactly are the matching principles that the search engine is operated on
    • Its Ranking System: in what order are the retrieved documents arranged
    • Its display format: what are the display elements and how display is arranged
search features
Search Features
  • A search engine may support all or some of the following features:
    • Boolean search
    • Proximity
    • Truncation
    • Case Sensitive
    • Phrase Search
    • Field Searching
    • Limits
    • Sorting
type of searches
Type of Searches

Typically, a search engine contains two forms of search:

1.Basic or Simple Search: used for general searches, oriented to general public, emphasizing high recall

2.Advanced or Power Search: Used for more precise searches, allow the user to specify date range, conducting field search and modify display format, etc. Focusing on high precision

Note: not all search engines support advanced search techniques. Search engines with subject directory sites normally do not offer advanced search techniques.

your own home page
Your own home page
  • Your own site on the web
  • Must have a service provider
  • Must have some software with which to write it
  • Manual exercise
  • Some editors and programming aids: such as Microsoft Frontpage
making web pages
Making Web Pages
  • Create text files
    • Plain text
    • .htm or .html extensions
  • Content includes HTML and text
  • Place it on a web server
  • HyperText Markup Language
    • Hypertext: Documents distributed in files and connected by hyperlinks
  • The markup language used by the World Wide Web
  • HTML uses markup tags to tell the Web browser how to display the text.
    • Formatting commands are intermixed with text in a file
    • Interpreted from start to finish
  • It was invented by Tim Berners-Lee
html tags
HTML tags
  • ‹html›...‹/html›

These tags tell the Web browser that your document can be displayed and they also mark the beginning and end of the entire document.

  •  ‹head›...‹/head›

These tags create a header for your Web document. This lets you title your document.

  •  ‹title›...‹/title›

These tags create a title for your Web document so people will know your Web document's name. This title does not appear on the page but usually shows up at the top of the browser window.

<title>Introduction to HTML</title>

  •  ‹body›...‹/body›
html tags52
  • The minimal HTML document:






for example




A Dog’s Life





A Dog’s Life


Dog 1: Bow wow wow


Dog 2: Bow wow wow wow


<img src=“http://”>



For Example

Netscape: A Dog’s Life


A Dog’s Life

Dog 1: Bow wow wow

Dog 2: Bow wow wow wow

Checkout: VIEW Source

html s problems
HTML’s Problems
  • HTML is a presentation technology only
    • HTML tag names don’t describe what content is. They only imply how content appears
  • HTML has a fixed tag set
  • In HTML, both the tag semantics and the tag set are fixed.
extensible markup language xml
Extensible Markup language (XML)
  • Markup language for structured documents
  • XML specifies neither semantics nor a tag set.
  • XML was created so that richly structured documents could be used over the web.

<?xml version="1.0" encoding="utf-8" ?>

<book isbn="0836217462">

<title>Being a Dog Is a Full-Time Job</title>

<author>Charles M. Schulz</author>



<friend-of>Peppermint Patty</friend-of>


<qualification>extroverted beagle</qualification>



<name>Peppermint Patty</name>


<qualification>bold, brash and tomboyish</qualification>



  • Java is an object-oriented programming language that allows small programs – called applets – to be included in HTML documents.
  • Applets are small programs that are downloaded to, and run on, the user’s computer, the client computer. Java-enabled web pages can include input forms, rotating images, fireworks, interactive animation and real-time updates.
  • Pull Technology - requires web user to actively request information; traditional web mechanism
  • Push Technology - automatically supplies desirable information to users
    • provides timely, prioritized distribution of information over a corporate network in the workplace
    • enhances traditional Web advertising in the consumer market
    • used for software delivery and updates
push technology

Server automatically downloads content to your computer at regular intervals

Consolidates information according to a user’s profile & displays in the browser

ticker tape pushed to desktop from Microsoft Investor Web site

push technology
  • A private network that uses Internet software and TCP/IP protocols
    • Provide employees with easy access to corporate information
    • Used to deploy corporate applications
      • Examples – policies and procedures manuals; human resource forms; product catalogs
    • Security is a concern
      • Security measures include – public key security, encryption, digital certificates, firewalls
  • An extension of an intranet to selected outside business partners, such as suppliers, distributors, and key customers
    • Provide business partners with easy access to corporate information and easy collaboration
  • Security
    • Critical to prevent unwanted entry into internal systems
    • Virtual private networks (VPNs) are often used to add security to Internet communication
extranets continued
Extranets (continued)
  • Extranet configurations
    • One company sets up a Extranet for its dealers, customers, or suppliers
    • Companies within an industry set up a collaborative Extranet for mutual benefit
    • Several companies collaborate over an Extranet for joint venture
  • Benefits include –
    • Lower communication costs; better communication; improved order entry and customer service; improvement in business effectiveness
security in intranet and extranet
Security in intranet and extranet
  • Virtual private network (VPN)
    • A secure connection between two points across the Internet
    • messages are encoded when they are sent across the virtual private network and decoded upon receipt.
    • Virtual private networks are often available from Internet service providers.
  • Tunneling
    • The process by which VPNs transfer information by encapsulating traffic in IP packets over the Internet
  • Firewall
a firewall

A security system consisting of hardware and/or software that prevents unauthorized access to data and information on a network

Many large companies route all communications through a proxy server to implement a firewall

Proxy server

A server outside the company’s network that controls which communications pass into the company’s network

Firewalls use a variety of screening techniques

Check domain name or IP address

Require digital signatures

a personal firewall

A software program that detects and protects your personal computer and its data from unauthorized intrusions

Constantly monitors all transmissions to and from your computer

Informs you of any attempted intrusions

internet challenges
Internet Challenges
  • New Technologies
    • Adopted by vendors more rapidly than users and customers can implement them
    • Web developers cannot assume that users can run their innovations successfully
  • Internet Regulation
    • Technical organizations (e.g., World Wide Web Consortium) develop standards governing the Internet’s functionality
    • These organizations are not formally charged in any legal or operational sense with responsibility for the Internet
    • How to control controversial content on the Web?
internet challenges continued
Internet Challenges (continued)
  • Internet Expansion
    • Tremendous Internet traffic growth has strained some elements of the network
      • Slower retrieval times
      • Unreliable data transmission
      • Denial of service by overloaded servers
    • Approaches to overcoming this congestion include
      • Improved hardware technology
      • Improved Web management software
internet challenges continued72
Internet Challenges(continued)
  • Internet Privacy - Web sites collect information with and without consumers’ knowledge
    • Cookie - small data file placed on users’ hard drives when a site is first visited. Collects data on pages visited and content viewed.
    • Three potential approaches to the privacy issue
      • Government lets groups develop voluntary privacy standards; does not take any action now unless real problems arise
      • Government recommends privacy standards for the Internet; does not pass laws at this time
      • Government passes laws now for how personal information can be collected and used on the Internet
    • Financial transaction security also a concern
What is an electronic profile?

A collection of data about an individual

Includes very personal details such as your age, address, telephone number, spending habits, marital status, number of dependents and so on

Data is collected every time you fill out a form or click an advertisement on the Web

Merchants sell the contents of their databases to national marketing firms and Internet advertising firms

Data is combined with information from public sources

Marketing firms sell your electronic profile to any company that requests it

What is a cookie?

A small file that a Web server stores on your computer

Typically contains data about you

A Web site can read data only from its own cookie file

Some Web sites sell or trade information stored in your cookie to advertisers

Track user preferences

Track how regularly you visit a site and the Web pages you visit when at the site

Target advertisements to your interests and browsing habits

How can cookies track user preferences?

The personal information you enter in the form is converted to codes, which are stored in a cookie on your hard disk

Cookie for MSNBC saved in Cookies folder on hard disk

How can you set your browser to control cookies?

You can set your browser to accept cookies automatically, prompt you if you wish to accept a cookie, or disable cookie use

Many Web sites do not allow you to access features if you disable cookie use

What is a cookie manager?

A software program that selectively blocks cookies

What is spyware?

A program placed on a computer without the user's knowledge that secretly collects information about the user

Can enter your computer as a virus or as a result of installing a new program

Communicates information it collects to some outside source while you are online

Adware: Spyware used by Internet advertising firms to collect information about a user’s Web browsing habits

To remove spyware, you need to purchase a special program that can detect and delete it


Unencrypted, readable data


The encrypted (scrambled) data


The process of converting readable data into unreadable characters to prevent unauthorized access

Encrypted data can be stored or sent as an e-mail message

To read the data, the recipient must decrypt it

An encryption key is the formula that the recipient of the data uses to decrypt ciphertext

encryption software

encryption key

What are some data encryption methods?

An encryption key (formula) often uses more than one of these methods

How do organizations encrypt data?

Most organizations use available software packages for encryption

Others develop their own encryption programs

A sample encrypted file

what are two basic types of encryption
Private key encryption

Also called a symmetric key encryption

Both the originator and recipient use the same secret key to encrypt and decrypt the data

The most popular private encryption system is the data encryption standard (DES). The U.S. government is a primary user of DES.

Public key encryption

Also called asymmetric key encryption

Uses two encryption keys: a public key and a private key

Public key encryption software generates both your private key and public key

Public keys are made known to those with which you communicate

The private key is kept confidential

What are two basic types of encryption?
How does public key encryption work?

Step 4: Receiver can read or print the decrypted message.

Step 3: Receiver uses his or her private key to decrypt the message.

Step 1: Sender creates document to be e-mailed to receiver.

Step 2: Sender uses receiver’s public key to encrypt a message.

public key

public key

public key

private key

private key

decrypted message

message to be sent

message to be sent

message to be sent

message to be sent

encrypted message

encrypted message

encrypted message

Receiver (Mohammed)

Sender (Joan)

Sender (Joan)

Sender (Joan)

Sender (Joan)

what are some public key encryption technologies
RSA encryption

Invented by Rivest, Shamir, and Adleman

A powerful public key encryption technology used to encrypt data transmitted over the Internet


Stores the user’s private key and other information on a PC Card

What are some public key encryption technologies?
Pretty Good Privacy (PGP)

One of the most popular e-mail digital encryption programs

Freeware for personal, non-commercial users

Uses a public-key encryption scheme

What is a digital signature?

Also called a digital ID

An encrypted code that a person, Web site, or company attaches to an electronic message to verify the identity of the message sender

The code usually consists of the user's name and a hash of all or part of the message

Helps to prevent e-mail forgery and verify that the contents of a message has not changed

Hash :A mathematical formula that generates a code from the contents of the message