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The Internet

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  1. The Internet

  2. Networks - Overview • Internet – a network of networks • Overview of networks • A network consists of two or more computers connected together • Common components include: • Client computers • Server computers • Shared devices • Cables, hubs, and routers that provide the network connections

  3. Networks – Overview (con’t) • One way to describe networks is by their size: • LAN (Local Area Network) – single building, relatively short distance • WAN (Wide Area Network) – spans a large geographic area; Internet can be considered a large WAN • Also: • MAN (Metropolitan Area Network) – spans a distance larger than a LAN but smaller than a WAN • WLAN (Wireless Local Area Network) – uses WiFi wireless network technology • PAN (Personal Area Network) – organized around an individual; can involve cell phone, PDA, mobile computer, etc. • CAN (Campus Area Network) – spans multiple LANs but smaller than a MAN; used on a college campus

  4. Networks – Benefits • Benefits of networks • Convenience • Resource sharing • Facilitates communication • Saves money • Reliability • Scalability

  5. Internet Growth • 433+ million computers linked as of 01/2007 (http://www.isc.org/index.pl) • Reasons for success: • Decisions not politically based • Internet is distributed operation • Homogeneity of language and outlook • Inherently interested people • Free (or inexpensive) software

  6. Internet Protocols • Protocols – rules that describe how computers communicate; some common protocols: • FTP (File Transfer Protocol) • Email protocols – SMTP, POP, IMAP • HTTP (HyperText Transfer Protocol) • TCP/IP (Transmission Control Protocol/Internet Protocol)

  7. TCP/IP • TCP/IP (Transmission Control Protocol/Internet Protocol): • How computers connect, send, and receive information • TCP permits communication between computers • IP specifies how data is routed to and from computers • TCP and IP are primary protocols but TCP/IP refers to a whole suite of protocols • Called “language of the Internet” • Mandated in 1983 for all ARPANET hosts

  8. TCP/IP (con’t) • Example 1: Sending an e-mail message • Formatted according to Simple Mail Transfer Protocol (SMTP) • Example 2: Requesting a Web page • Formatted according to Hyper Text Transfer Protocol (HTTP)

  9. TCP/IP (con’t) • TCP is responsible for splitting the message into IP packets; each packet contains: • Piece of message • Information about sender • Information about receiver • Sequence number • Error checking information

  10. TCP/IP (con’t) • IP is responsible for routing the packets to the correct destination address • At destination (receiving) computer TCP is responsible for: • Reassembling message • Sending requests for corrupt packets to be resent • Advantages of packets: • Error recovery • Load distribution • Flexibility

  11. Physical Components • Servers • Answer service requests • Routers • Direct data packets • Networks • Transport packets • Copper wires, fiber-optic cables, radio waves, microwaves, infrared light, and visible light

  12. Types of Internet Connections • Analog – regular dial-up - up to 56 Kbps • ISDN (Integrated Services Digital Network) –up to 128 Kbps • Broadband connections – faster than analog and ISDN: • xDSL (Digital Subscriber Line) – permanent connection that uses phone line but does not tie up your connection; 128 Kbps to 8 Mbps • Cable – permanent connection that operates over cable TV lines; 512 Kbps to 20 Mbps

  13. Types of Internet Connections (con’t) • Other types of connections: • Wireless Internet connections – uses radio frequency bands instead of telephone or cable networks (newer technology) • T-1 lines – leased line option; used by businesses connecting to Internet and by ISPs connecting to the Internet backbone. Dedicated phone connection that supports data rates of 1.544 Mbps • T-3 lines – used to connect to backbone and for the backbone itself. 43 to 45 Mbps • IoS – Internet over Satellite; access via satellite

  14. ISPs, NSPs • Internet Service Provider (ISP) • Network Service Provider (NSP) • Local ISPs can connect to NSPs • Leased-lines from local telephone companies provide part of the network • Transmit data at 1.54 megabits (Mbps) • Backbone Provider – organization that supplies access to high-speed transmission lines used to connect to the Internet; some providers include: MCI, Sprint, UUNET, AGIS, BBN

  15. IP Address • Unique numerical name identifying each computer on Internet • vs. Domain Name • People-oriented unique name using symbols; e.g., www.amazon.com • 32 bits (four bytes) – 1 byte can represent the numbers 0 thru 255 • Four natural numbers separated by dots (i.e., 72.21.203.1) • Network component and host component

  16. IP Address (con’t) • Vital in packet switching • Internet Assigned Numbers Authority (IANA) • Operating unit of Internet Corporation for Assigned Names and Numbers (ICANN) – http://www.icann.org/index.html • Assigns and manages IP addresses • IP address to domain names • Resolver converts symbolic name to IP address • Programs convert IP addresses to symbolic names (vice versa) • nslookup (UNIX-based systems)

  17. IP Address (con’t) • Static IP address • Permanent • Connection through router • Dynamic IP address • Changes with each Internet connection • Connection through ISP

  18. IP Address (con’t) • IPv6 or IPng - latest version of Internet Protocol (IP or IPv4) • Major changes: • More addresses • IP address size from 32 bits to 128 bits • IPv4 supports 232 addresses; IPv6 supports 2128 addresses • Simplified IP headers • Reduction of header fields in IP packet • Added security features

  19. Web Page Retrieval Enter a URL (how://where/what) (1)Browser determines URL using “how” part (2)Browser queries the DNS for IP address using “where” part (3)DNS responds with IP address (e.g. - 172.132.173.2) (4) Browser establishes TCP connection to above (5) Browser sends a request for “what” portion

  20. Web Page Retrieval (con’t) Enter a URL (con’t) (6) Server services request by sending back the “what” part (7) TCP connection closed (8) Browser renders text portion of HTML (9) Browser repeats steps for in-line image files (10)Browser displays images as retrieved

  21. World Wide Wait • Congestion issues and delays caused frustration • Resulted from popularity • Reasons: • Increase in Internet users - why? • Elaborate Web pages contain images, sounds, video clips

  22. World Wide Wait (con’t) • World Wide Web Consortium (W3C) issues: • “Save the Internet from the Web” • Improving process of connecting • New techniques to expedite Web page requests • Refining how URL resolved • Web page design suggestions: • Avoid unnecessary graphics • Cascading Style Sheets (CSS) • PNG instead of GIF

  23. Issues and Predictions • Intranets • Isolated, private network with an internal Web • Cost • Inexpensive – time to charge more? • Internet2 - http://www.internet2.edu • Networking consortium that facilitates the development, deployment and use of revolutionary Internet technologies. • For schools, libraries, universities, researchers • Much higher speeds – Abilene network backbone supports transfer rates 100 to 1000 times faster than typical broadband connections

  24. Internet Culture • Critical Evaluation of Information • Freedom of Expression • Communication Mechanisms • Advertising • Societal Impact

  25. Freedom of Expression • Lack of regulation • Blue ribbon graphic • Obscene or offensive material • Censorship • Platform for Internet Content Selection (PICS) • Set of technical specifications for designating labels • Works with vendor-supplied filtering software

  26. Communication Mechanisms • E-mail and mailing lists • Internet Relay Chat (IRC) • Instant Messaging (AOL’s IM and ICQ) • Blogs • Newsgroups • Videoconferencing • Emoticons and shorthand • Flaming and SHOUTING

  27. Societal Impact • Advertising • Clickable images • Revolving advertisements • Spam • Internet related jobs • Information and communication • Weather, news, stock prices, travel information • How we shop / bank / invest (spend $)

  28. On-line Businesses • Types: Advertising, marketing, partnership, retail, service, software, subscription • On-line business hurdles: • Privacy and security • Cookies - http://www.cookiecentral.com • File (on your disk) containing data about you • Created while on-line • Filling out a form/registering • Encrypted • Setting a cookie • Persistent cookie

  29. Business and Safety/Security • Secure payment (credit cards); Secure Electronic Transactions (SET); Electronic money • Legal Environment • New and uncharted territory • Taxes and tariffs • President Clinton (July 1997) - Framework for the Global Electronic Commerce • Policy on Global Information Infrastructure (GII) • Principles: • Encourage self-regulation of Internet • Should not restrict e-commerce • Provide legal environment • Acknowledge uniqueness • Promote globally

  30. Collaborative Computing • Applications that allow sharing of information and resources between people • World Wide Web • Collaborative computing platform supporting HTML • Groupware • Collaborative computing platform software on networked computer system • E-mail • Intelligent form • Version control • Videoconferencing