Session 2


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Session 2

  1. 1. AGENDA: StarHub case debrief Infrastructure for e-commerce In-class exercise: Blog analysis HTML lab Session 2: Technology Infrastructure: The Internet and the Web
  2. 2. Objectives <ul><li>In this chapter, you will learn about: </li></ul><ul><li>The origin, growth, and current structure of the Internet </li></ul><ul><li>How packet-switched networks are combined to form the Internet </li></ul><ul><li>How Internet protocols and Internet addressing work </li></ul><ul><li>The history and use of markup languages on the Web, including SGML, HTML, and XML </li></ul>
  3. 3. Objectives <ul><li>How HTML tags and links work on the World Wide Web </li></ul><ul><li>The differences among internets, intranets, and extranets </li></ul><ul><li>Options for connecting to the Internet, including cost and bandwidth factors </li></ul><ul><li>About Internet2 and the Semantic Web </li></ul>
  4. 4. The Internet and the World Wide Web <ul><li>Computer network </li></ul><ul><ul><li>Any technology that allows people to connect computers to each other </li></ul></ul><ul><li>The Internet </li></ul><ul><ul><li>A large system of interconnected computer networks spanning the globe </li></ul></ul><ul><li>World Wide Web </li></ul><ul><ul><li>A subset of computers on the Internet </li></ul></ul>
  5. 5. Origins of the Internet <ul><li>Early 1960s </li></ul><ul><ul><li>U.S. Department of Defense funded research to explore creating a worldwide network </li></ul></ul><ul><li>In1969, Defense Department researchers </li></ul><ul><ul><li>Connected four computers into network called ARPANET </li></ul></ul><ul><li>Throughout 1970s and 1980s </li></ul><ul><ul><li>Academic researchers connected to ARPANET and contributed to its technological developments </li></ul></ul>
  6. 6. New Uses for the Internet <ul><li>1972 </li></ul><ul><ul><li>E-mail born </li></ul></ul><ul><li>Mailing list (listserve) </li></ul><ul><ul><li>E-mail address that forwards all messages received to any user who subscribed to the list </li></ul></ul><ul><li>Usenet </li></ul><ul><ul><li>Started by group of students and programmers at Duke University and University of North Carolina </li></ul></ul><ul><li>External returns to use </li></ul>
  7. 7. Growth of the Internet <ul><li>In 1991, NSF </li></ul><ul><ul><li>Eased restrictions on commercial Internet activity </li></ul></ul><ul><ul><li>Began implementing plans to privatize the Internet </li></ul></ul><ul><li>Network access points (NAPs) </li></ul><ul><ul><li>Basis of new structure Internet </li></ul></ul><ul><li>Network access providers </li></ul><ul><ul><li>Sell Internet access rights directly to larger customers and indirectly to smaller firms and individuals through ISPs </li></ul></ul>
  8. 8. Growth of the Internet
  9. 9. World Wide Web <ul><li>The Web </li></ul><ul><ul><li>Software that runs on computers connected to the Internet </li></ul></ul><ul><li>Vannevar Bush </li></ul><ul><ul><li>Speculated that engineers would eventually build a memory extension device (the Memex) </li></ul></ul><ul><li>In the 1960s </li></ul><ul><ul><li>Ted Nelson described a similar system called hypertext </li></ul></ul>
  10. 10. Emergence of the World Wide Web (Continued) <ul><li>Tim Berners-Lee </li></ul><ul><ul><li>Developed code for hypertext server program </li></ul></ul><ul><li>Hypertext server </li></ul><ul><ul><li>Stores files written in hypertext markup language </li></ul></ul><ul><ul><li>Lets other computers connect to it and read files </li></ul></ul><ul><li>Hypertext Markup Language (HTML) </li></ul><ul><ul><li>Includes set of codes (or tags) attached to text </li></ul></ul><ul><ul><li>Browser displays text and images on client (1994) </li></ul></ul>
  11. 11. Packet-Switched Networks <ul><li>Local area network (LAN) </li></ul><ul><ul><li>Network of computers located close together </li></ul></ul><ul><li>Wide area networks (WANs) </li></ul><ul><ul><li>Networks of computers connected over greater distances </li></ul></ul><ul><li>Circuit </li></ul><ul><ul><li>Combination of telephone lines and closed switches that connect them to each other </li></ul></ul>
  12. 12. Packet-Switched Networks (Continued) <ul><li>Circuit switching </li></ul><ul><ul><li>Centrally controlled, single-connection model </li></ul></ul><ul><li>Packets </li></ul><ul><ul><li>Files and e-mail messages on a packet-switched network that are broken down into small pieces </li></ul></ul><ul><ul><li>Travel from computer to computer along the interconnected networks until they reach their destinations </li></ul></ul>
  13. 13. Routing Packets <ul><li>Routing computers </li></ul><ul><ul><li>Computers that decide how best to forward packets </li></ul></ul><ul><li>Routing algorithms </li></ul><ul><ul><li>Rules contained in programs on router computers that determine the best path on which to send packet </li></ul></ul><ul><ul><li>Programs apply their routing algorithms to information they have stored in routing tables </li></ul></ul>
  14. 14. Router-based Architecture of the Internet
  15. 15. Internet Protocols <ul><li>Protocol </li></ul><ul><ul><li>Collection of rules for formatting, ordering, and error-checking data sent across a network </li></ul></ul><ul><li>Rules contributing to success of Internet </li></ul><ul><ul><li>Independent networks should not require any internal changes to be connected to the network </li></ul></ul><ul><ul><li>Packets that do not arrive at their destinations must be retransmitted from their source network </li></ul></ul><ul><ul><li>Router computers act as receive-and-forward devices </li></ul></ul><ul><ul><li>No global control exists over the network </li></ul></ul>
  16. 16. TCP/IP <ul><li>TCP </li></ul><ul><ul><li>Controls disassembly of a message or a file into packets before transmission over Internet </li></ul></ul><ul><ul><li>Controls reassembly of packets into their original formats when they reach their destinations </li></ul></ul><ul><li>IP </li></ul><ul><ul><li>Specifies addressing details for each packet </li></ul></ul>
  17. 17. The Heart of the Internet? “It’s the TCP/IP Protocol Stack” <ul><li>Applications </li></ul><ul><ul><li>Web </li></ul></ul><ul><ul><li>Email </li></ul></ul><ul><ul><li>Video/Audio </li></ul></ul><ul><li>TCP/IP </li></ul><ul><li>Access Technologies </li></ul><ul><ul><li>Ethernet (LAN) </li></ul></ul><ul><ul><li>Wireless (LMDS, WiFi, Cellular) </li></ul></ul><ul><ul><li>Cable </li></ul></ul><ul><ul><li>DSL </li></ul></ul><ul><ul><li>Satellite </li></ul></ul>TCP/IP Applications Access Technologies “ Choke Point” Middleware Services Network Technology Substrate Supply
  18. 18. IP Addressing <ul><li>Internet Protocol version 4 (IPv4) </li></ul><ul><ul><li>Uses a 32-bit number to identify computers connected to the Internet </li></ul></ul><ul><li>Base 2 (binary) number system </li></ul><ul><ul><li>Used by computers to perform internal calculations </li></ul></ul><ul><li>Subnetting </li></ul><ul><ul><li>Use of reserved private IP addresses within LANs and WANs to provide additional address space </li></ul></ul><ul><li>IP V6 extends addressing, control functionality </li></ul>
  19. 19. IP Addressing (Continued) <ul><li>Private IP addresses </li></ul><ul><ul><li>Series of IP numbers not permitted on packets that travel on the Internet </li></ul></ul><ul><li>Network Address Translation (NAT) device </li></ul><ul><ul><li>Used in subnetting to convert private IP addresses into normal IP addresses </li></ul></ul><ul><li>Internet Protocol version 6 (IPv6) </li></ul><ul><ul><li>Protocol that will replace IPv4 </li></ul></ul><ul><ul><li>Uses a 128-bit number for addresses </li></ul></ul>
  20. 20. Domain Names <ul><li>Sets of words assigned to specific IP addresses </li></ul><ul><li>Top-level domain (or TLD) </li></ul><ul><ul><li>Rightmost part of a domain name </li></ul></ul><ul><li>Internet Corporation for Assigned Names and Numbers (ICANN) </li></ul><ul><ul><li>Responsible for managing domain names and coordinating them with IP address registrars </li></ul></ul>
  21. 21. Top-level Domain Names
  22. 22. Web Page Request and Delivery Protocols <ul><li>Web client computers </li></ul><ul><ul><li>Run software called Web client software or Web browser software </li></ul></ul><ul><li>Web server computer </li></ul><ul><ul><li>Runs software called Web server software </li></ul></ul><ul><li>Client/server architecture </li></ul><ul><ul><li>Combination of client computers running Web client software and server computers running Web server software </li></ul></ul>
  23. 23. Web Page Request and Delivery Protocols (Continued) <ul><li>Hypertext Transfer Protocol (HTTP) </li></ul><ul><ul><li>Set of rules for delivering Web page files over the Internet </li></ul></ul><ul><li>Uniform Resource Locator (URL) </li></ul><ul><ul><li>Combination of the protocol name and domain name </li></ul></ul><ul><ul><li>Allows user to locate a resource (the Web page) on another computer (the Web server) </li></ul></ul>
  24. 24. Electronic Mail Protocols <ul><li>Electronic mail (e-mail) </li></ul><ul><ul><li>Must also be formatted according to common set of rules </li></ul></ul><ul><li>E-mail server </li></ul><ul><ul><li>Computer devoted to handling e-mail </li></ul></ul><ul><li>E-mail client software </li></ul><ul><ul><li>Used to read and send e-mail </li></ul></ul><ul><ul><li>Example: Microsoft Outlook, Netscape Messenger </li></ul></ul>
  25. 25. Electronic Mail Protocols (Continued) <ul><li>Simple Mail Transfer Protocol (SMTP) </li></ul><ul><ul><li>Specifies format of a mail message </li></ul></ul><ul><li>Post Office Protocol (POP) </li></ul><ul><ul><li>POP message can tell the e-mail server to </li></ul></ul><ul><ul><ul><li>Send mail to user’s computer and delete it from e-mail server </li></ul></ul></ul><ul><ul><ul><li>Send mail to user’s computer and not delete it </li></ul></ul></ul><ul><ul><ul><li>Simply ask whether new mail has arrived </li></ul></ul></ul><ul><ul><li>Provides support for Multipurpose Internet Mail Extensions (MIME) </li></ul></ul>
  26. 26. Intranets and Extranets <ul><li>Intranet </li></ul><ul><ul><li>Interconnected network that does not extend beyond organization that created it </li></ul></ul><ul><li>Extranet </li></ul><ul><ul><li>Intranet extended to include entities outside boundaries of organization </li></ul></ul><ul><ul><li>Connects companies with suppliers, business partners, or other authorized users </li></ul></ul>
  27. 27. Public and Private Networks <ul><li>Public network </li></ul><ul><ul><li>Any computer network or telecommunications network available to the public </li></ul></ul><ul><li>Private network </li></ul><ul><ul><li>A private, leased-line connection between two companies that physically connects their intranets </li></ul></ul><ul><li>Leased line </li></ul><ul><ul><li>A permanent telephone connection between two points </li></ul></ul>
  28. 28. Virtual Private Network (VPN) <ul><li>Extranet that uses public networks and their protocols </li></ul><ul><li>IP tunneling </li></ul><ul><ul><li>Effectively creates a private passageway through the public Internet </li></ul></ul><ul><li>Encapsulation </li></ul><ul><ul><li>Process used by VPN software </li></ul></ul><ul><li>VPN software </li></ul><ul><ul><li>Must be installed on the computers at both ends of the transmission </li></ul></ul>
  29. 29. Internet Connection Options <ul><li>Bandwidth </li></ul><ul><ul><li>Amount of data that can travel through a communication line per unit of time </li></ul></ul><ul><li>Net bandwidth </li></ul><ul><ul><li>Actual speed that information travels </li></ul></ul><ul><li>Symmetric connections </li></ul><ul><ul><li>Provide same bandwidth in both directions </li></ul></ul><ul><li>Asymmetric connections </li></ul><ul><ul><li>Provide different bandwidths for each direction </li></ul></ul>
  30. 30. Voice-Grade Telephone Connections <ul><li>POTS, or plain old telephone service </li></ul><ul><ul><li>Uses existing telephone lines and analog modem </li></ul></ul><ul><ul><li>Provide bandwidth between 28 and 56 Kbps </li></ul></ul><ul><li>Digital Subscriber Line (DSL) </li></ul><ul><ul><li>Connection methods do not use modem </li></ul></ul><ul><li>Integrated Services Digital Network (ISDN) </li></ul><ul><ul><li>Offers bandwidths between 128 Kbps and 256 Kbps </li></ul></ul>
  31. 31. Broadband Connections <ul><li>Operate at speeds of greater than 200 Kbps </li></ul><ul><li>Asymmetric digital subscriber (ADSL) </li></ul><ul><ul><li>Transmission bandwidth is from 100 to 640 Kbps upstream and from 1.5 to 9 Mbps downstream </li></ul></ul><ul><li>Cable modems </li></ul><ul><ul><li>Provide transmission speeds between 300 Kbps and 1 Mbps </li></ul></ul><ul><li>DSL </li></ul><ul><ul><li>Private line with no competing traffic </li></ul></ul>
  32. 32. Leased-Line Connections <ul><li>DS0 (digital signal zero) </li></ul><ul><ul><li>Telephone line designed to carry 1 digital signal </li></ul></ul><ul><li>T1 line (also called a DS1) </li></ul><ul><ul><li>Carries 24 DS0 lines and operates at 1.544 Mbps </li></ul></ul><ul><li>Fractional T1 </li></ul><ul><ul><li>Provides service speeds of 128 Kbps and upward in 128-Kbps increments </li></ul></ul><ul><li>T3 service (also called DS3) </li></ul><ul><ul><li>Offers 44.736 Mbps </li></ul></ul>
  33. 33. Wireless Connections <ul><li>Bluetooth </li></ul><ul><ul><li>Designed for personal use over short distances </li></ul></ul><ul><ul><li>Low-bandwidth technology, with speeds of up to 722 Kbps </li></ul></ul><ul><ul><li>Networks are called personal area networks (PANs) or piconets </li></ul></ul><ul><ul><li>Consumes very little power </li></ul></ul><ul><ul><li>Devices can discover each other and exchange information automatically </li></ul></ul>
  34. 34. Wireless Ethernet (Wi-Fi or 802.11b/g/n) <ul><li>Most common wireless connection technology for use on LANs </li></ul><ul><li>Wireless access point (WAP) </li></ul><ul><ul><li>Device that transmits network packets between Wi-Fi-equipped computers and other devices </li></ul></ul><ul><li>Has potential bandwidth of 11-54 Mbps and range of about 300 feet (n >100 Mbps) </li></ul><ul><li>Devices capable of roaming </li></ul>
  35. 35. Wireless Ethernet (Wi-Fi or 802.11a/b/g/n) <ul><li>802.11a protocol </li></ul><ul><ul><li>Capable of transmitting data at speeds up to 54 Mbps, on different frequencies to 802.11b </li></ul></ul><ul><li>802.11g protocol </li></ul><ul><ul><li>Has 54 Mbps speed of 802.11a </li></ul></ul><ul><ul><li>Compatible with 802.11b devices </li></ul></ul><ul><li>802.11n emerging standard </li></ul><ul><ul><li>Expected to offer speeds up to 320 Mbps </li></ul></ul>
  36. 36. Fixed-Point Wireless <ul><li>One version uses system of repeaters to forward radio signal from ISP to customers </li></ul><ul><li>Repeaters </li></ul><ul><ul><li>Transmitter-receiver devices (transceivers) </li></ul></ul><ul><li>Mesh Routing </li></ul><ul><ul><li>Directly transmits Wi-Fi packets through hundreds, or even thousands, of short-range transceivers acting as routers </li></ul></ul>
  37. 37. Cellular Telephone Networks <ul><li>Third-generation (3G) cell phones </li></ul><ul><ul><li>Combine latest technologies available today </li></ul></ul><ul><li>Short message service (SMS) </li></ul><ul><ul><li>Protocol used to send and receive short text messages </li></ul></ul><ul><li>Mobile commerce (m-commerce) </li></ul><ul><ul><li>Describes the kinds of resources people might want to access using wireless devices </li></ul></ul>
  38. 38. Internet2 and the Semantic Web <ul><li>Internet2 </li></ul><ul><ul><li>Experimental test bed for new networking technologies </li></ul></ul><ul><ul><li>Has achieved bandwidths of 10 Gbps and more on parts of its network </li></ul></ul><ul><ul><li>Used by universities to conduct large collaborative research projects </li></ul></ul>
  39. 39. Internet2 and the Semantic Web (Continued) <ul><li>Semantic Web </li></ul><ul><ul><li>Project by Tim Berners-Lee </li></ul></ul><ul><ul><li>If successful </li></ul></ul><ul><ul><ul><li>Would result in words on Web pages being tagged (using XML) with their meanings </li></ul></ul></ul><ul><li>Resource description framework (RDF) </li></ul><ul><ul><li>Set of standards for XML syntax </li></ul></ul><ul><li>Ontology </li></ul><ul><ul><li>Set of standards that defines relationships among RDF standards and specific XML tags </li></ul></ul>
  40. 40. Markup Languages and the Web <ul><li>Text markup language </li></ul><ul><ul><li>Specifies set of tags that are inserted into text </li></ul></ul><ul><li>Standard Generalized Markup Language (SGML) </li></ul><ul><ul><li>Older and complex text markup language </li></ul></ul><ul><ul><li>A meta language </li></ul></ul><ul><li>World Wide Web Consortium (W3C) </li></ul><ul><ul><li>Not-for-profit group that maintains standards for the Web </li></ul></ul>
  41. 41. Development of Markup Languages
  42. 42. Standard Generalized Markup Language <ul><li>Offers a system of marking up documents that is independent of any software application </li></ul><ul><li>Nonproprietary and platform independent </li></ul><ul><li>Offers user-defined tags </li></ul><ul><li>Costly to set up and maintain </li></ul>
  43. 43. Hypertext Markup Language (HTML) <ul><li>Prevalent markup language used to create documents on the Web today </li></ul><ul><li>HTML tags </li></ul><ul><ul><li>Interpreted by Web browser and used by it to format the display of the text </li></ul></ul><ul><li>HTML Links </li></ul><ul><ul><li>Linear hyperlink structure </li></ul></ul><ul><ul><li>Hierarchical hyperlink structure </li></ul></ul>
  44. 44. Hypertext Markup Language (HTML) (Continued) <ul><li>Scripting languages and style sheets </li></ul><ul><ul><li>Most common scripting languages </li></ul></ul><ul><ul><ul><li>JavaScript, JScript, Perl, and VBScript </li></ul></ul></ul><ul><ul><li>Cascading Style Sheets (CSS) </li></ul></ul><ul><ul><ul><li>Sets of instructions that give Web developers more control over the format of displayed pages </li></ul></ul></ul><ul><ul><ul><li>Style sheet </li></ul></ul></ul><ul><ul><ul><ul><li>Usually stored in a separate file </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Referenced using the HTML style tag </li></ul></ul></ul></ul>
  45. 45. Extensible Markup Language (XML) <ul><li>Uses paired start and stop tags </li></ul><ul><li>Includes data management capabilities that HTML cannot provide </li></ul><ul><li>Differences between XML and HTML </li></ul><ul><ul><li>XML is not a markup language with defined tags </li></ul></ul><ul><ul><li>XML tags do not specify how text appears on a Web page </li></ul></ul>
  46. 46. Processing a Request for an XML Page
  47. 47. Summary <ul><li>TCP/IP </li></ul><ul><ul><li>Protocol suite used to create and transport information packets across the Internet </li></ul></ul><ul><li>POP, SMTP, and IMAP </li></ul><ul><ul><li>Protocols that help manage e-mail </li></ul></ul><ul><li>Languages derived from SGML </li></ul><ul><ul><li>Hypertext Markup Language (HTML) </li></ul></ul><ul><ul><li>Extensible Markup Language (XML) </li></ul></ul>
  48. 48. Summary <ul><li>Intranets </li></ul><ul><ul><li>Private internal networks </li></ul></ul><ul><li>Extranet </li></ul><ul><ul><li>Used when companies want to collaborate with suppliers, partners, or customers </li></ul></ul><ul><li>Internet2 </li></ul><ul><ul><li>Experimental network built by a consortium of research universities and businesses </li></ul></ul>