Chapter%202:%20Technology%20Infrastructure:%20The%20Internet%20and%20the%20World%20Wide%20Web

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Chapter 2Technology Infrastructure The
Internet and the World Wide Web

• Electronic Commerce, Sixth Edition

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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

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Objectives (continued)

• 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

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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

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Origins of the Internet

• Early 1960s
• U.S. Department of Defense funded research to
  explore creating a worldwide network
• In1969, 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

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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

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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

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Growth of the Internet
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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

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Emergence of the World Wide Web (continued)

• 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

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Packet-Switched Networks

• Local area network (LAN)
• Network of computers located close together
• Wide area networks (WANs)
• Networks of computers connected over greater
  distances
• Circuit
• Combination of telephone lines and closed
  switches that connect them to each other

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Packet-Switched Networks (continued)

• Circuit switching
• Centrally controlled, single-connection model
• Packets
• Files and e-mail messages on a packet-switched
  network that are broken down into small pieces
• Travel from computer to computer along the
  interconnected networks until they reach their
  destinations

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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

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Router-based Architecture of the Internet
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Internet Protocols

• Protocol
• Collection of rules for formatting, ordering, and
  error-checking data sent across a network
• Rules for message handling
• 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

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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

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IP Addressing

• Internet Protocol version 4 (IPv4)
• Uses a 32-bit number to identify computers
  connected to the Internet
• Base 2 (binary) number system
• Used by computers to perform internal
  calculations
• Subnetting
• Use of reserved private IP addresses within LANs
  and WANs to provide additional address space

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IP Addressing (continued)

• Private IP addresses
• Series of IP numbers not permitted on packets
  that travel on the Internet
• Network Address Translation (NAT) device
• Used in subnetting to convert private IP
  addresses into normal IP addresses
• Internet Protocol version 6 (IPv6)
• Protocol that will replace IPv4
• Uses a 128-bit number for addresses

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Domain Names

• Sets of words assigned to specific IP addresses
• 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

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Top-Level Domain Names
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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
• Client/server architecture
• Combination of client computers running Web
  client software and server computers running Web
  server software

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Web Page Request and Delivery Protocols
(continued)

• 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 user to locate a resource (the Web page)
  on another computer (the Web server)

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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

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Electronic Mail Protocols (continued)

• Simple Mail Transfer Protocol (SMTP)
• Specifies format of a mail message
• Post Office Protocol (POP)
• POP message can tell the e-mail server to
• Send mail to a users computer and delete it from
  the e-mail server
• Send mail to a users computer and not delete it
• Simply ask whether new mail has arrived
• Provides support for Multipurpose Internet Mail
  Extensions (MIME)

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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 complex text markup language
• A meta language
• World Wide Web Consortium (W3C)
• Not-for-profit group that maintains standards for
  the Web

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Development of Markup Languages

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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

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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
• Linear hyperlink structures
• Hierarchical hyperlink structures

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Hypertext Markup Language (HTML) (continued)

• Scripting languages and style sheets
• Most common scripting languages
• JavaScript, JScript, Perl, and VBScript
• Cascading Style Sheets (CSS)
• Sets of instructions that give Web developers
  more control over the format of displayed pages
• Style sheet
• Usually stored in a separate file
• Referenced using the HTML style tag

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Extensible Markup Language (XML)

• Uses paired start and stop tags
• 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

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Processing a Request for an XML Page
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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

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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

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Virtual Private Network (VPN)

• 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
• VPN software
• Must be installed on the computers at both ends
  of the transmission

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VPN Architecture Example
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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

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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 do not use a modem
• Integrated Services Digital Network (ISDN)
• Bandwidths between 128 Kbps and 256 Kbps

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Broadband Connections

• Operate at speeds of greater than 200 Kbps
• Asymmetric digital subscriber (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

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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
• T3 service (also called DS3)
• Offers 44.736 Mbps

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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

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Wireless Ethernet (Wi-Fi or 802.11b)

• 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 potential bandwidth of 11 Mbps and a range of
  about 300 feet
• Devices are capable of roaming

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Wireless Ethernet (Wi-Fi or 802.11b) (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

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Fixed-Point Wireless

• One version uses 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

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Cellular Telephone Networks

• Third-generation (3G) cell phones
• Combine 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

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Internet2 and the Semantic Web

• Internet2
• Experimental test bed for new networking
  technologies
• Has achieved bandwidths of 10 Gbps and more on
  parts of its network
• Used by universities to conduct large
  collaborative research projects

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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

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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)

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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