Chapter 2: Technology Infrastructure: The Internet and the World Wide Web

1. Chapter 2:Technology Infrastructure: The Internet and the World Wide Web

2. Objectives In this chapter, you will learn about: • The origin, growth, and current structure of the Internet • How packet-switched networks are combined to form the Internet • How Internet protocols and Internet addressing work • The history and use of markup languages on the Web, including SGML, HTML, and XML • How HTML tags and links work on the World Wide Web • The differences among internets, intranets, and extranets • Options for connecting to the Internet, including cost and bandwidth factors • Internet2 and the Semantic Web

3. The Internet and the World Wide Web • Computer network • Any technology that allows people to connect computers to each other • The Internet • A large system of interconnected computer networks spanning the globe • World Wide Web • A subset of computers on the Internet

4. History of the Internet • Wikipedia Internet History • Early 1960s • U.S. Department of Defense funded research to explore creating a worldwide network • In 1969 • Defense Department researchers connected four computers into a network called ARPANET • Throughout the 1970s and 1980s • Academic researchers connected to ARPANET and contributed to its technological developments

5. New Uses for the Internet • 1972 • E-mail was born • Mailing list • E-mail address that forwards any message received to any user who has subscribed to the list • Usenet • Started by a group of students and programmers at Duke University and the University of North Carolina

6. Growth of the Internet • In 1991, the NSF: • Eased restrictions on commercial Internet activity • Began implementing plans to privatize the Internet • Network access points (NAPs) • Basis of the new structure of the Internet • Network access providers • Sell Internet access rights directly to larger customers and indirectly to smaller firms and individuals through ISPs

8. Emergence of the World Wide Web • The Web • Software that runs on computers connected to the Internet • Vannevar Bush speculated that engineers would eventually build a memory extension device (the Memex) • In the 1960s, Ted Nelson described a similar system called hypertext

9. Emergence of the World Wide Web • Tim Berners-Lee developed code for a hypertext server program • Hypertext server: • Stores files written in the hypertext markup language • Lets other computers connect to it and read files • Hypertext Markup Language (HTML) • Includes a set of codes (or tags) attached to text

10. Routing Packets • Routing computers • Computers that decide how best to forward packets • Routing algorithms • Rules contained in programs on router computers that determine the best path on which to send packets • Programs apply their routing algorithms to information they have stored in routing tables

12. Internet Protocols • Protocol • Collection of rules for formatting, ordering, and error-checking data sent across a network • Rules for message handling include: • Independent networks should not require any internal changes to be connected to the network • Packets that do not arrive at their destinations must be retransmitted from their source network • Router computers act as receive-and-forward devices • No global control exists over the network

13. TCP/IP • TCP • Controls disassembly of a message or a file into packets before transmission over the Internet • Controls reassembly of packets into their original formats when they reach their destinations • IP • Specifies addressing details for each packet

14. Domain Names • A domain name is a set of words assigned to a specific IP address • Top-level domain (or TLD) • Rightmost part of a domain name • Internet Corporation for Assigned Names and Numbers (ICANN) • Responsible for managing domain names and coordinating them with IP address registrars

16. Web Page Request and Delivery Protocols • Web client computers • Run software called Web client software or Web browser software • Web server computers • Run software called Web server software • The web uses a thin-client/server architecture • Combination of client computers running Web client software and server computers running Web server software

17. Web Page Request and Delivery Protocols • Hypertext Transfer Protocol (HTTP) • Set of rules for delivering Web page files over the Internet • Uniform Resource Locator (URL) • Combination of the protocol name and domain name • Allows a user to locate a resource (the Web page) on another computer (the Web server)

18. Electronic Mail Protocols • Electronic mail (e-mail) • Must be formatted according to a common set of rules • E-mail server • Computer devoted to handling e-mail • E-mail client software • Used to read and send e-mail • Examples include Microsoft Outlook and Netscape Messenger

19. Electronic Mail Protocols • Simple Mail Transfer Protocol (SMTP) • Specifies the format of a mail message • Post Office Protocol (POP) • POP messages can tell the e-mail server to: • Send mail to a user’s computer and delete it from the e-mail server • Send mail to a user’s computer and not delete it • Simply ask whether new mail has arrived • POP provides support for Multipurpose Internet Mail Extensions (MIME)

20. Markup Languages and the Web • Text markup language • Specifies a set of tags that are inserted into text • Standard Generalized Markup Language (SGML) • Older and more complex text markup language than HTML • A meta language • World Wide Web Consortium (W3C) • Not-for-profit group that maintains standards for the Web

22. Standard Generalized Markup Language • Offers a system of marking up documents that is independent of any software application • Nonproprietary and platform independent • Offers user-defined tags • Costly to set up and maintain

23. Hypertext Markup Language (HTML) • Prevalent markup language used to create documents on the Web today • HTML tags are interpreted by a Web browser and are used by it to format the display of the text • HTML links can be structured as: • Linear hyperlink structures • Hierarchical hyperlink structures

24. Hypertext Markup Language (HTML)) • The most common scripting languages include JavaScript, JScript, Perl, and VBScript • Cascading Style Sheets (CSS) are sets of instructions that give Web developers more control over the format of displayed pages • Style sheet is: • Usually stored in a separate file • Referenced using the HTML style tag

25. Extensible Markup Language (XML) • XML uses paired start and stop tags • It includes data management capabilities that HTML cannot provide • Differences between XML and HTML: • XML is not a markup language with defined tags • XML tags do not specify how text appears on a Web page

27. Intranets and Extranets • Intranet • Interconnected network that does not extend beyond the organization that created it • Extranet • Intranet extended to include entities outside the boundaries of an organization • Connects companies with suppliers, business partners, or other authorized users

28. Public and Private Networks • Public network • Any computer network or telecommunications network available to the public • Private network • A private, leased-line connection between two companies that physically connects their intranets • Leased line • Permanent telephone connection between two points

29. Virtual Private Network (VPN) • VPN • An extranet that uses public networks and their protocols • IP tunneling • Effectively creates a private passageway through the public Internet • Encapsulation • Process used by VPN software

31. Internet Connection Options • Bandwidth • Amount of data that can travel through a communication line per unit of time • Net bandwidth • Actual speed that information travels • Symmetric connections • Provide the same bandwidth in both directions • Asymmetric connections • Provide different bandwidths for each direction

32. Voice-Grade Telephone Connections • POTS, or plain old telephone service • Uses existing telephone lines and an analog modem • Provides bandwidth between 28 and 56 Kbps • Digital Subscriber Line (DSL) • Connection methods that do not use a modem • Integrated Services Digital Network (ISDN) • Bandwidths between 128 Kbps and 256 Kbps

33. Broadband Connections • Broadband connections operate at speeds of greater than 200 Kbps • Asymmetric digital subscriber line (ADSL) • Transmission bandwidth is from 100 to 640 Kbps upstream and from 1.5 to 9 Mbps downstream • Cable modems • Provide transmission speeds between 300 Kbps and 1 Mbps • DSL • Private line with no competing traffic

34. Leased-Line Connections • DS0 (digital signal zero) • Telephone line designed to carry one digital signal • T1 line (also called a DS1) • Carries 24 DS0 lines and operates at 1.544 Mbps • Fractional T1 • Provides service speeds of 128 Kbps and upward in 128-Kbps increments • T3service (also called DS3) • Offers 44.736 Mbps

35. Wireless Connections • Bluetooth • Designed for personal use over short distances • Low-bandwidth technology, with speeds of up to 722 Kbps • Networks are called personal area networks (PANs) or piconets • Consumes very little power • Devices can discover each other and exchange information automatically

36. Wireless Ethernet (Wi-Fi) • Wireless Ethernet (Wi-Fi or 802.11b) is the most common wireless connection technology for use on LANs • Wireless access point (WAP) • Device that transmits network packets between Wi-Fi-equipped computers and other devices • Has a potential bandwidth of 11 Mbps and a range of about 300 feet • Devices are capable of roaming

37. Wireless Ethernet (Wi-Fi) (continued) • 802.11a protocol • Capable of transmitting data at speeds up to 54 Mbps • 802.11g protocol • Has 54 Mbps speed of 802.11a • Compatible with 802.11b devices • 802.11n • Expected to offer speeds up to 320 Mbps

38. Fixed-Point Wireless • One versionof fixed-point wirelessuses a system of repeaters to forward a radio signal from an ISP to customers • Repeaters • Transmitter-receiver devices (transceivers) • Mesh routing • Directly transmits Wi-Fi packets through hundreds, or even thousands, of short-range transceivers

39. Cellular Telephone Networks • Third-generation (3G) cell phones • Combine the latest technologies available today • Short message service (SMS) • Protocol used to send and receive short text messages • Mobile commerce (m-commerce) • Describes the kinds of resources people might want to access using wireless devices

40. Internet2 and the Semantic Web • Internet2 • Experimental test bed for new networking technologies • Includes bandwidths of 10 Gbps and more on parts of its network • Used by universities to conduct large collaborative research projects

41. Internet2 and the Semantic Web (continued) • Semantic Web • Project by Tim Berners-Lee • If successful, it would result in words on Web pages being tagged (using XML) with their meanings • Resource description framework (RDF) • Set of standards for XML syntax • Ontology • Set of standards that defines relationships among RDF standards and specific XML tags

42. Summary • TCP/IP • Protocol suite used to create and transport information packets across the Internet • POP, SMTP, and IMAP • Protocols that help manage e-mail • Languages derived from SGML • Hypertext Markup Language (HTML) • Extensible Markup Language (XML)

43. Summary (continued) • Intranets • Private internal networks • Extranet • Used when companies want to collaborate with suppliers, partners, or customers • Internet2 • Experimental network built by a consortium of research universities and businesses