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CHAPTER 7

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  1. CHAPTER 7 THE INTERNETAND INTRANETS

  2. 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 Marina G. Erechtchoukova

  3. The Evolution of the Internet Marina G. Erechtchoukova

  4. 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 Marina G. Erechtchoukova

  5. The Operation of the Internet • Internet is packet-switched network • Client-Server architecture • Internet Protocol • Internet Model Marina G. Erechtchoukova

  6. Internet Model • Interface layerdefines 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 Marina G. Erechtchoukova

  7. OSI Model vs. Internet Model Marina G. Erechtchoukova

  8. Internet Application Layer • File Transfer Protocol • Telnet • Simple Mail Transfer Protocol • Simple Network Management Protocol • HyperText Transfer Protocol • Domain Name System Marina G. Erechtchoukova

  9. 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 Marina G. Erechtchoukova

  10. Domain name system (DNS) • Domain – a group of networks • Domains are organized hierarchically • DNS is based on hierarchical database: • Variable-depth hierarchy • Distributed database • Examples:www.atkinson.yorku.ca www.yorku.ca Marina G. Erechtchoukova

  11. 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 Marina G. Erechtchoukova

  12. Internet Services • Communications services • Information retrieval services • World Wide Web • Web services Marina G. Erechtchoukova

  13. 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 Marina G. Erechtchoukova

  14. 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 Marina G. Erechtchoukova

  15. Communications Services Provided by the Internet (continued…) • Internet Fax • Content streaming: • Audio • Video • Real-time audio and video Marina G. Erechtchoukova

  16. Information Retrieval Services • FTP service • File Transfer Protocol can be used to copy an arbitrary file from one computer to another • Client–Server architecture • A control connection is established to a remote computerand remains in place until the user closes it. • Data connection • File name translation • Archie searches the file on FTP sites Marina G. Erechtchoukova

  17. 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 Marina G. Erechtchoukova

  18. 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 Marina G. Erechtchoukova

  19. 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) Marina G. Erechtchoukova

  20. 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 Marina G. Erechtchoukova

  21. 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 Explorer’s 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 Marina G. Erechtchoukova

  22. 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 Marina G. Erechtchoukova

  23. 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 user’s 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 Marina G. Erechtchoukova

  24. 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 Marina G. Erechtchoukova

  25. 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 Marina G. Erechtchoukova

  26. 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 Marina G. Erechtchoukova

  27. 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 Marina G. Erechtchoukova

  28. 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 Marina G. Erechtchoukova

  29. 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. traditionalnetworks: • HTTP and HTML platform independent • A single input point – a browser Marina G. Erechtchoukova

  30. Intranet software • Teamware • used for team building, sharing ideas and documents, brainstorming, scheduling, and archiving decision to facilitate productivity • Add-on to groupware Marina G. Erechtchoukova

  31. Security • Public Key security • Encryption • Digital certificates • Firewalls • Set of rules placed on the router • One or more computers • Assured pipelines Marina G. Erechtchoukova

  32. Extranet • A network that links business partners to one another over the Internet by providing access to certain areas of each other’s corporate intranets • Components • Intranets of business partners • Internet as communications links Marina G. Erechtchoukova

  33. 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 Marina G. Erechtchoukova

  34. Types of Extranet • A company and its dealers, customers, or suppliers • centered around one company • An industry’s 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 Marina G. Erechtchoukova

  35. 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 Marina G. Erechtchoukova