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Internet

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Internet

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  1. Internet Inside the Internet and the Web

  2. Topics “It’s a bit like climbing a mountain. You don’t know how far you’ve come until you stop and look back.” Vint Cerf The Internet: A Network of Networks Internet Applications: Communication and Connection Inside the World Wide Web The Evolving Internet

  3. The Internet: A Network of Networks The Internet is an interconnected network of thousands of networks linking academic, research, government, and commercial institutions.

  4. Internet Services The Internet provides scientists, engineers, educators, students, business people, and others with a variety of services such as: • Electronic mail (send/receive mail messages) • Remote login(Telnet - access to other computers)

  5. Internet Services • Transferring files(FTP - accessing archives of data) • Newsgroups(Usenet - on-line public discussions) • World Wide Web(a collection of multimedia documents)

  6. Counting Connections Today, the Internet connects computers to about every country in the world. However, the Internet is: • growing too fast to measure its growth • too decentralized to quantify • a network with no hard boundaries

  7. Internet Protocols The language at the heart of the Internet is TCP/IP… • Transmission Control Protocol/Internet Protocol • Allows cross-network communication

  8. Internet Protocols TCP breaks messages into packets • Each packet has all the information needed to travel from network to network • Host systems called Routers determine how to route transmissions

  9. Internet Protocols IP is the address for the packets • Each Internet host computer has a unique IP Address • Each address is comprised of four sets of numbers separated by periods, such as 123.23.168.22

  10. Internet Access Options Direct (dedicated) Connection • Computer has its own IP address and is attached to a LAN • No need to dial up • Files are stored on your computer • Response time is quick

  11. Internet Access Options • Dialup Connections • limited connection using a modem • Full access dial up uses SLIP or PPP via modem • Broadband Connections • DSL service is newer, faster, and cheaper than ISDN • Can share phone line with voice traffic

  12. Internet Access Options • Cable Modem Connection • allow Internet connections using shared TV cables • can exceed DSL speeds • Carry increased privacy and security risks • Satellite Connections • provides connections using DirecTV satellite dishes

  13. Internet Access Options • Internet Service Providers (ISPs) • local ISPs provide connections through local telephone lines • national ISPs offer connections on a nationwide scale

  14. Intranets and Extranets • Intranets - self-contained intra-organizational networks designed using the same technology as the Internet • Firewalls - used to prevent unauthorized communication and secure sensitive internal data

  15. Intranets and Extranets A typical Intranets include: • E-mail • Newsgroups • File transfer • Web publishing • Other services

  16. Intranets and Extranets • Extranets: designed for outside use by customers, clients, and business partners • Electronic Commerce:business transactions through electronic networks

  17. Intranets and Extranets • Electronic data interchange (EDI):a decade-old set of specifications for ordering, billing, and paying for parts and services over private networks. • Virtual private networks:not subject to the traffic and security problems.

  18. Internet Applications:Communication and Connection • The user interface varies depending on which client/server application is being used. • UNIX- developed by Bell Labs, allows a timesharing computer to communicate with several other computers or terminals at once.

  19. Internet Addresses • E-mail addresses are made upof two parts separated by an at(@) sign: • User name@host name • Example: johnsmith@mindspring.com • The host is named using DNS (domain name system), which translates IP addresses into a string of names. “Each person on the “Internet” has a unique e-mail “address” created by having a squirrel run across a computer keyboard.” Dave Barry

  20. Internet Addresses An Internet address includes: username@hostname.sub.dom • username is the person’s “mailbox” • hostname is the name of the host computer and is followed by one or more domains separated by periods: • host.subdomain.domain • host.domain • host.subdomain.subdomain.domain

  21. Internet Addresses Top level domains include: • .edu - educational sites • .com - commercial sites • .gov - government sites • .mil - military sites • .net - network administration sites • .org - nonprofit organizations

  22. president@whitehouse.gov Internet Addresses Examples: User President whose mail is stored on the host whitehouse in the government domain User hazel_filbert at the server for Lane County, Oregon, k-12 school district hazel_filbert@lane.k12.or.us

  23. E-mail on the Internet What appears on the screen depends on the type of Internet connection and mail program you use Eudora is an easy to use Email software. Outlook and Netscape Communicator are popular e-mail software

  24. E-mail on the Internet • Why are free email accounts made available? • often offered to attract Web site visitors • available for users of public computers • sensible for those wanting multiple e-mail addresses not associated with a workplace

  25. E-mail on the Internet • EEmail Formats include: • ASCII text so they can be viewed with any client program • MIMEthat can be used to send and receive text with enriched text or HTML (displays text formatting, graphics, and links to Web pages)

  26. Mailing Lists and Network News • Mailing lists allow you to participate in email discussion groups on special-interest topics. • Network News are public discussions that you can go in and out as you please. • Messages are posted on virtual bulletin boards (for everyone to read).

  27. Real-Time Communication • Internet relay chat (IRC)allows several users to chat simultaneously • Internet Telephonyturns the Internet into a toll-free long-distance telephone service • Video teleconferences allow multi-person videoconferences via the Web

  28. Real-Time Communication See… …Type Hear…

  29. Telnet and FTP • Information gathering • Telnet - makes remote login possible • FTP (file transfer protocol) - allows files to be uploaded and downloaded from remote computers

  30. Telnet and FTP • Web browsers locate and transfer files without typing commands • When you click a Web link to download a file, you’re probably usingFTP

  31. Inside the World Wide Web • WWW is a distributed browsing and searching system developed at CERN • System was designed to give Internet documents unique addresses • HTML language was created for encoding and displaying documents • Browser software was built for viewing documents from remote locations

  32. Browsing the Web Web site Jargon: • Web pages are made up of text and images • A Web site is a collection of web pages • A Home page is the main entry to a Web site • A Web browser like Netscape Communicator or Internet Explorer allows you to explore the Web by clicking links

  33. Browsing the Web Hyperlinks (links)are words or pictures that act as buttons, allowing you to go to another Web page Links are typically underlined or displayed in a different color

  34. More on Browsing the Web More Web site Jargon Links allow you to locate information without knowing its exact location (it may move from time to time) Back and Forward buttons let you retrace your steps Bookmarks and Favorites can be set up to mark your favorite Web locations

  35. Web Addresses Pronounced Earl…like the name A typical URL looks like this: http://www.prenhall.com.beekman

  36. Path to the host http:// help/database.html www.vote-smart.org/ Web Addresses Protocol for Web pages Dissecting Web Page address: Resource Page

  37. Searching the Web • Search engines • produce a list of pages that match a keyword • they are built around a database that catalogs Web locations based on content • Directory or Subject Tree • A hierarchical catalog of Web sites • Natural Language Search Engines • Allows users to ask for what they want “The ability to ask the right question is more than half the battle of finding the answer.” Thomas J. Watson

  38. Search Engines • Search engines help find information when you type a query using keywords.

  39. Search Engines • Directory/subject tree engines offer a menu of subject choices

  40. Search Engines • Ask questions in a Natural Language Search Engine

  41. Portals • Portals offer quick and easy access to a variety of services such as e-mail, chat,maps, news, shopping, etc. • Examples of consumer portals include • Yahoo!, Excite, Lycos, Alta Vista, Netscape Netcenter, Snap • Specialized portals target specific industries and economic sectors

  42. Tables Frames Forms Downloadable audio and video Streaming audio and video Real-time live audio or video 3-D environments From Hypertext to Multimedia Typical Web pages can contain:

  43. Plug-Ins are software extensions that add new features. Examples include… QuickTime Shockwave/Flash RealPlayer Acrobat From Hypertext to Multimedia

  44. Webcasting: Push Technology • Client computers pull information • Browsers initiate a request for information • Push technology delivers information automatically to the client computer • Up to the minute weather reports • News headlines

  45. An HTML document includes codes that determines the format, layout, and structure of a Web document Publishing on the Web HTML (Hypertext Markup Language) HTML is not WYSIWYG

  46. Publishing on the Web This text coded as HTML … • <H1>Welcome to Computer Confluence</H1><b>Publishing on the Web</b> Appears like this on the screen …

  47. Publishing on the Web • Alternatives to HTML… • Programs that convert document format features into HTML codes • Microsoft Word, FileMaker • Web authoring programs • HomePage, GoLive, FrontPage

  48. Beyond HTML Dynamic HTML: adds more programming power to HTML by allowing code to automatically modify itself under certain circumstances JavaScript:a simple language for enhancing HTML Web pages

  49. Beyond HTML • WML • Wireless Markup Language helps create Web documents containing stock quotes, phone numbers, and other small nuggets of information XML • Will replace HTML plus provide additional features and extensions VRML • Virtual Reality Modeling Language creates 3-D virtual worlds

  50. Beyond HTML Java • A full-featured, cross platform, object-oriented programming language Java applets • Small Java programs that can be automatically downloaded onto your client computer and can run on any platform