THE INTERNET AND INTRANETS

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CHAPTER 7

• THE INTERNETAND INTRANETS

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What is the Internet?

• The Largest computer network in the world (a
  network of networks)
• Exchanges information seamlessly by using the
  same open, non-proprietary standards and
  protocols, within interconnected networks
• Forms a massive electronic communications network
• Provides a true democratic communications forum
  and has produced a democratization of information

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The Evolution of the Internet
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The Infrastructure of the Internet

• Commercial communications carriers provide the
  physical network backbone of the Internet
• Internet Service Providers
• Backbone providers
• Access providers
• Reciprocal agreement

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The Operation of the Internet

• Internet is packet-switched network
• Client-Server architecture
• Internet Protocol
• Internet Model

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Internet Model

• Interface layer defines physical medium and frame
  for flow and error control
• Internet network layer defines the path to
  intended receiver in the network. Uses Internet
  Protocol (IP)
• Internet transport layer provides point-to-point
  reliable transmission of data. Uses TCP and UDP.
• Internet application layer supports network
  application

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OSI Model vs. Internet Model
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Internet Application Layer

• File Transfer Protocol
• Telnet
• Simple Mail Transfer Protocol
• Simple Network Management Protocol
• HyperText Transfer Protocol
• Domain Name System

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Addresses on the Internet

• IP address uniquely identifies each computer in
  the network
• Example 130.63.160.120
• The necessity to keep a master table with IP
  addresses on each router
• Hard to remember for people
• Domain name system (DNS) - derives the names of
  the computers

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Domain name system (DNS)

• Domain a group of networks
• Domains are organized hierarchically
• DNS is based on hierarchical database
• Variable-depth hierarchy
• Distributed database
• Exampleswww.atkinson.yorku.ca
• www.yorku.ca

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Accessing the Internet

• Connect via LAN Server
• Communications stack
• Connect via Serial Line Internet
  Protocol/Point-to-point Protocol (SLIP/PPP)
• Connect via an Online Service

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Internet Services

• Communications services
• Information retrieval services
• World Wide Web
• Web services

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Communications Services Provided by the Internet

• E-mail
• Mail Gateway a computer dedicated to forwarding
  e-mail
• USENET Newsgroups
• Bulletin board
• Discussion threads (moderate vs. unmoderate)
• LISTSERV
• Chatting

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Communications Services Provided by the Internet
(continued)

• Telnet
• Internet telephony
• Voice-over IP
• Sharing digital lines
• Disadvantages
• Low quality of sounds
• Delays in transmission process

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Communications Services Provided by the Internet
(continued)

• Internet Fax
• Content streaming
• Audio
• Video
• Real-time audio and video

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Information Retrieval Services

• FTP service
• File Transfer Protocol can be used to copy an
  arbitrary file from one computer to another
• ClientServer architecture
• A control connection is established to a remote
  computer and remains in place until the user
  closes it.
• Data connection
• File name translation
• Archie searches the file on FTP sites

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Information Retrieval Services (continued)

• Gopher distributed document delivery system
• Based on TCP
• Flow control and sequencing
• Acknowledgment and Retransmission
• Checksums
• Veronica searches text in Gopher menus

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The World Wide Web

• The Internet functions as the transport mechanism
  
• The World Wide Web - a system with universally
  accepted standards for storing, retrieving,
  formatting, and displaying information
• Web Servers support WWW application, are
  scattered all over the world

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Web site

• Web Site
• Home Page - first, introductory page in a web
  site
• Webmaster - the person in charge of a Web site
• Uniform Resource Locator (URL)

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Hypertext Transfer Protocol (HTTP)

• communications standard used to transfer pages
  across the WWW
• Web client establishes connection with server
• Web server receives a request
• Web server sends a message
• The connection is closed, if Web client does not
  use keep alive option

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Browser

• software application that is used to access and
  navigate the Web
• Netscape Communicator
• a multipurpose suite that handles news, e-mail,
  audio- and video conferencing, and more
• Microsoft Internet Explorer
• Internet Explorers tight integration with
  Windows offers users the advantage of one-stop
  computing
• Offline Browser
• enables a user to retrieve pages automatically
  from Web sites at predetermined times

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Search Engines

• Programs that return a list of Web sites or pages
  that match some user-selected criteria
• Ways to select pages for inclusion in the
  database
• Web Crawlers
• Registration
• Methods for information search
• Depth first
• Breadth first
• Metasearch engines

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Push vs. Pull Technology

• Pull Technology users select and retrieve
  information from the Web
• Push Technology automatically supplies
  information to users by means of a process
  running on either the users desktop or a network
  server
• provides timely, prioritized distribution of
  information over a corporate network in the
  workplace
• enhances traditional Web advertising in the
  consumer market

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Web Services

• Information Filters
• Platform for Internet Content Selection
• Intelligent agents
• Clipping Services
• track news topics and retrieve articles from
  database of publications
• Personalized Web Services
• offer the ability to generate Web content that is
  personalized for individual Web site visitors
• Collaborative Filtering

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Web Authoring

• Standard HTML is the common denominator
• Enhancements to HTML
• Dynamic HTML (DHTML)
• Extensible markup language (XML)
• Voice markup language (VoxML)
• Virtual reality modeling language (VRML)
• HTML editors, generators, publishers

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Internet Challenges

• New Technologies
• Vendors are adopting new technologies more
  rapidly than users can implement them
• Internet Regulation
• WWW Consortium, Internet Engineering Task Force
  technical standards
• Content regulation
• Internet Expansion

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Internet Privacy

• Web sites collect information about visitors
• Registration
• Clickstream data
• Cookie is a mechanism that supports restoring
  client states
• small data file placed on users hard drives
  when they first visit a site
• Encrypting

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Intranets

• A private network that uses Internet software and
  TCP/IP protocols
• Process business data and information
  efficiently
• Data and information search
• Urgent information delivery
• Information distribution

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Intranet operation

• Intranet documents HTML pages
• HTTP used to transmit documents
• Browsers allow to view Intranet documents
• Supports applications to solve business problems
• Intranet vs. traditional networks
• HTTP and HTML platform independent
• A single input point a browser

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Intranet software

• Teamware
• used for team building, sharing ideas and
  documents, brainstorming, scheduling, and
  archiving decision to facilitate productivity
• Add-on to groupware

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Security

• Public Key security
• Encryption
• Digital certificates
• Firewalls
• Set of rules placed on the router
• One or more computers
• Assured pipelines

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Extranet

• A network that links business partners to one
  another over the Internet by providing access to
  certain areas of each others corporate intranets

• Components
• Intranets of business partners
• Internet as communications links

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Extranet infrastructure

• Telecommunications systems (VPNs)
• TCP/IP Protocols
• Internet Services
• Intranets infrastructure

Extranet
Company A
Company B
Intranet corporate data, e-mail, orders, customer
data, inventory, documents
Internet
Intranet
Internet
Internet
Internet
Other users customers, suppliers, contractors,
distributors, government
Corporate employees travelling or at home
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Types of Extranet

• A company and its dealers, customers, or
  suppliers
• centered around one company
• An industrys extranet teamed up and created by
  the major players in an industry
• Joint ventures and other business partnerships
• used for communications and collaboration among
  several companies partnering in a joint venture

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Benefits of Extranets

• Reduce the number of help-desk and data-entry
  employees
• Improve quality of data and information exchange
• Accelerate processes and information flows
• Reduce paperwork
• Provide better communications