Appendix A The Internet and the World Wide Web

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Appendix AThe Internet and the World Wide Web
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Objectives

• Obtain an overview of the information and tools
  that are available on the Internet
• Learn what computer networks and internets are
  and how they work
• Find out how the Internet began and grew
• Understand the addressing scheme used on the
  Internet
• Learn how the World Wide Web began
• Understand how people can connect to the Internet

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Internet and World Wide WebAmazing Developments

• Internet is a large collection of computers all
  over the world connected to one another
• One of the most amazing technological
  developments of the 20th century
• World Wide Web is a subset of computers on the
  Internet that helped make Internet resources
  available to people who are not computer experts

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Exploring Uses for the Internet

• New Ways to Communicate
• E-mail
• Electronic discussions
• Instant messaging
• Information Resources and Software
• Newspapers and magazines
• Government documents
• Research reports and books
• Software download sites

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Exploring Uses for the Internet

• Doing Business Online
• Electronic storefronts
• Coordinate worldwide operations
• Recruit employees
• Entertainment
• Review restaurants, movies, theater, musical
  events and books
• Interactive games
• Follow sports teams

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Computer Networks

• Network Interface Card (NIC) a card used to
  connect a computer to a network of other
  computers
• Server computer that accepts requests and shares
  some or all of its resources with computers it is
  connected to
• NICs connect to cables which connect to servers

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Client/Server Local Area Networks

• The server runs software that coordinates
  information flow among other computers
• Client computers connected to a server
• Network Operating System software that runs on a
  server
• Client/Server Network
• one server computer sharing its resources with
  multiple client computers
• commonly used to connect LANs

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A Client/Server LAN
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Client/Server Local Area Networks

• Node or network node each computer, printer, or
  other device connected to a network
• Most PCs can handle server duties if they are
  equipped with enough memory and large enough disk
  drives

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Connecting Computers to a Network

• Twisted-pair cable oldest type of cable, used by
  telephone companies
• Electrical interference a small flow of unwanted
  electricity in nearby objects, including other
  wires, created when a wire carries an electric
  current and generates an electromagnetic field
  around itself
• Category 1 cable the type of twisted-pair cable
  that telephone companies have used for years to
  transmit voice signals

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Connecting Computers to a Network

• Coaxial cable 20 times faster than Category 1
  cable, more expensive
• Category 5 cable carries signals between 10 and
  100 times faster than coaxial cable, easy to
  install
• Category 5e cable constructed of higher quality
  materials than Category 5 cable and carries more
  signals up to 10 times faster than regular
  Category 5 cable
• Fiber-optic cable most expensive type of cable
  transmits pulsing beams of light through very
  thin strands of glass, fastest transmission rate

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Types of Cable
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Connecting Computers to a Network

• Wireless networks
• Becoming more common as costs continue to drop
• Welcome in organizations that occupy old
  buildings
• Popular with companies whose employees use laptop
  computers
• Used by schools in classrooms, libraries, and
  study lounges
• Used in homes

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A Wireless Home Network
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Origins of the Internet

• Early 1960s by the U.S. Department of Defense
  (DOD)
• Major research project authorized as a part of
  national security
• Explored ways to connect large mainframe
  computers and weapons installations distributed
  all over the world
• Defense Advanced Research Projects Agency (DARPA)
  charged with the task

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Connectivity Circuit Switchingvs. Packet
Switching

• Circuit switching
• Centrally controlled
• Single-connection method
• Used by most local telephone traffic today
• Vulnerable to destruction of signal control point
  or any link in the single path that carries the
  signal

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Connectivity Circuit Switchingvs. Packet
Switching

• Packet-switching files and messages broken down
  into packets and labeled electronically with
  codes for their origin and destination
• Packets travel from computer to computer along
  the network until they reach their destination
• Routers determine the best way for a packet to
  move towards its destination

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Connectivity Circuit Switchingvs. Packet
Switching

• Routers use routing algorithms programs to
  determine best path for packets
• Packet-switched networks more reliable
• Rely on multiple routers instead of central point
  of control
• Each router can send individual packets along
  different paths if parts of the network are not
  operating

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Origins of the Internet

• DARPA researchers connected first computer
  switches in 1969
• ARPANET grew over next three years to include
  over 20 computers
• Computers communicated to other computers on the
  network by using Network Control Protocol (NCP)
• Protocol collection of rules for formatting,
  ordering, and error-checking data sent across a
  network

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Open Architecture Philosophy

• Four Key Points
• Independent networks should not require any
  internal changes to be connected to the Internet
• Packets that do not arrive at their destinations
  must be retransmitted from their source network
• The router computers do not retain information
  about the packets they handle
• No global control will exist over the network

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Open Architecture Philosophy

• New set of protocols developed in 1970 by Vincent
  Cerf and Robert Kahn
• Transmission Control Protocol
• Internet Protocol
• (TCP/IP)
• TCP rules used by computers on a network to
  establish and break connections
• IP rules for routing of individual data packets

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Open Architecture Philosophy

• TCP/IP used today in LANs and on the Internet
• Term Internet first used in a 1974 article about
  the TCP protocol written by Cerf and Kahn
• Many consider Vincent Cerf the father of the
  Internet

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Birth of E-MailA New Use for Networks

• Ray Tomlinson, an ARPANET researcher, wrote a
  program that could send and receive messages over
  the network in 1972
• E-mail was born and rapidly became widely used in
  the computer research community
• ARPANET continued to develop faster and more
  effective network technologies
• Began sending packets by satellite in 1976

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More New Uses for Networks Emerge

• File Transfer Protocol (FTP) transfer files
  between computers
• Telnet users log in to their computer accounts
  from remote sites
• Mailing list an e-mail address that takes any
  message it receives and forwards it to any user
  who has subscribed to the list
• Mailing lists (such as BITNETs LISTSERV),
  information posting areas (such as the Users
  News Network, or Usenet, newsgroups), and
  adventure games were among the new applications
  appearing on the ARPANET

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Internconnecting the Networks

• Joint Academic Network (Janet) established in
  the United Kingdom in the early 1980s to link
  universities
• In 1984, the DoD split the ARPANET into two
  specialized networks
• ARPANET, which would continue its advanced
  research activities
• MILNET (for Military Network) would be reserved
  for military uses that required greater security
• In 1987, a network run by the National Science
  Foundation, (NSFnet) merged with another NSF
  network, called CSNet, and with BITNET to form
  one network that could carry much of the network
  traffic previously carried by ARPANET

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Internconnecting the Networks

• Network backbone includes the long-distance
  lines and supporting technology that transports
  large amounts of data between major network nodes
• NSFnet awarded a contract to Merit Network, Inc.,
  IBM, Sprint, and the state of Michigan to upgrade
  and operate the main NSFnet backbone
• By the late 1980s, many other TCP/IP networks had
  merged or established interconnections

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Networks That Became the Internet
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Commercial Interest Increases

• National Science Foundation (NSF) prohibited
  commercial network traffic on networks it funded
• Businesses turned to commercial e-mail services
• Larger firms built TCP/IP-based WANs that used
  leased telephone lines to connect field offices
  to corporate headquarters
• Intranet LANs or WANs that use the TCP/IP
  protocol but do not connect to sites outside the
  firm
• Extranet An intranet that allows selected
  outside parties to connect

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Commercial Interest Increases

• NSF permitted two commercial e-mail services, MCI
  Mail and CompuServe, to establish limited
  connections to the Internet in 1989
• Internet Engineering Task Force (IETF) a
  self-organized group that makes technical
  contributions to the engineering of the Internet
  and its technologies
• Internet Worm a program that distributed itself
  to more than 6,000 of the 60,000 computers
  connected to the Internet in 1988
• ARPANET grew from 4 computers in 1969 to over
  300,000 by 1990

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Growth of the Internet

• Formal definition of Internet was adopted in 1955
  by the Federal Networking Council (FNC)

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Growth of the Internet

• The process of shutting down the ARPANET and
  privatizing the Internet began in 1991 when the
  NSF eased its restrictions on Internet commercial
  activity
• U.S. Department of Defense finally closed the
  research portion of its network, the ARPANET, in
  1995
• Internet host a computer that connects a LAN or
  a WAN to the Internet

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Growth in the Number of Internet Hosts
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Growth of the Internet

• Number of hosts connected to Internet includes
  only computers directly connected to the Internet
• Internet traffic now carries more files that
  contain graphics, sound, and video, so Internet
  files have become larger
• Some companies and research organizations
  estimate the number of regular users of the
  Internet today to be more than 800 million, but
  no one knows how many individual e-mail messages
  or files travel on the Internet, and no one
  really knows how many people use the Internet
  today

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New Structure for the Internet

• Network access points (NAPs) four
  telecommunications companies around which the
  NSFnet was organized
• The four companies and their successors sell
  access to the Internet through their NAPs to
  organizations and businesses
• The NSFnet still exists for government and
  research use

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New Structure for the Internet

• More than 350 million connected host computers
  and more than 800 million worldwide Internet
  users
• TCP/IP numbering system that identifies users on
  the Internet is running short of numbers

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IP Addressing

• IP (Internet Protocol) address a unique
  identification number for each computer on the
  Internet
• IP version 4 (IPv4)
• current addressing system currently in use on the
  Internet
• 32-bits written in four 8-bit parts
• Byte an 8-bit number in most computer
  applications
• Octet an 8-bit number in networking applications

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IP Addressing

• Each part of a 32-bit IP address is separated
  from the previous part by a period, such as
  106.29.242.17
• This notation is often called dotted decimal
  notation
• The combination of these four parts provides 4.2
  billion possible addresses (256 256 256
  256)
• Because each of the four parts of a dotted
  decimal number can range from 0 to 255, IP
  addresses range from 0.0.0.0 to 255.255.255.255

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IP Addressing

• In the early days of the Internet, the 4 billion
  addresses provided by the IPv4 rules certainly
  seemed to be more addresses than an experimental
  research network would ever need
• About 2 billion of those addresses today are
  either in use or unavailable for use because of
  the way blocks of addresses were assigned to
  organizations
• The addition of new kinds of devices to the
  Internets many networks, such as wireless
  personal digital assistants and mobile phones
  that can access the Web, promises to keep the
  demand for IP addresses high

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IP Addressing

• Subnetting the use of reserved private IP
  addresses within LANs and WANs to provide
  additional address space
• Private IP addresses series of IP numbers that
  have been set aside for subnet use and are not
  permitted on packets that travel on the Internet
• Network address translation (NAT) device a
  computer that converts those private IP addresses
  into normal IP addresses when the packets move
  from the LAN or WAN onto the Internet

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IP Addressing

• IP version 6 (IPv6)
• New protocol to solve the limited addressing
  capacity of IPv4
• Protocol that would replace IPv4
• Approved by the IETF in 1997
• Major advantage of IPv6 is that the number of
  addresses is more than a billion times larger
  than the four billion addresses available in IPv4
• Changes the format of the packet by eliminating
  many of the fields that improvements in
  networking technologies have made unnecessary in
  the IPv4 packet it eliminates those fields and
  adds new fields for security and other optional
  information

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IP Addressing

• The Internet has become one of the most amazing
  technological and social accomplishments of the
  century
• Computers linked to this interconnected network
  are located in almost every country of the world
• Billions of dollars change hands every year over
  the Internet

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World Wide Web

• World Wide Web a way of thinking about
  information storage and retrieval
• Web software that runs on some of the computers
  connected to each other through the Internet
• Two important innovations played key roles
• Hypertext
• Graphical user interfaces (GUIs)

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Origins of Hypertext

• 1945 Vannevar Bush speculated engineers would
  eventually build a machine (Memex) that would
  store a persons books, records, letters, and
  research results on microfilm. Mechanical aids
  would help retrieve
• 1960 Ted Nelson described similar system where
  text on one page links to text on other pages. He
  called it hypertext
• 1960s Douglas Engelbart created first
  experimental hypertext system on one of the large
  computers

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Hypertext and Graphical UserInterfaces Come to
the Internet

• 1989 Tim Berners-Lee and Robert Calliau proposed
  a hypertext development project to improve
  document-handling capabilities
• Over the next two years, Berners-Lee developed
  the code for a hypertext server program and made
  it available on the Internet
• Hypertext server a computer that stores files
  written in the hypertext markup language and lets
  other computers connect to it and read those files

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Hypertext and Graphical UserInterfaces Come to
the Internet

• Hypertext Markup Language (HTML) a language that
  includes a set of codes (or tags) attached to
  text
• Hypertext Link (hyperlink) points to another
  location in the same or another HTML document

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Hypertext and Graphical UserInterfaces Come to
the Internet

• Web Browser software lets users read HTML
  documents and move from one HTML document to
  another through hypertext link tags in each file
• HTML is a subset of Standard Generalized Markup
  Language (SGML), which organizations use to
  manage large document-filing systems
• Heading tags in an HTML document, code that
  surrounds text to indicate that the text should
  be considered a heading
• GUI (graphical user interface) a way of
  presenting program output using pictures, icons,
  and other graphical elements

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Hypertext and Graphical UserInterfaces Come to
the Internet

• Mosaic first GUI program to read HTML an use
  HTML documents hyperlinks to navigate from page
  to page on computers anywhere on the Internet

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Hypertext and Graphical UserInterfaces Come to
the Internet
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The Web and Commercializationof the Internet

• Businesses quickly recognized profit-making
  potential offered by a world-wide network of
  easy-to-use computers
• The Netscape Navigator Web browser, called
  Mozilla, was an instant success
• Internet Explorer Web browser entered the market
  soon after Netscapes success became apparent

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The Web and Commercializationof the Internet

• Netscape Navigator browser became open-source
  software. Open-source software is created and
  maintained by volunteer programmers, often
  hundreds of them, who work together using the
  Internet to build and refine a program
• The current open-source release of this browser
  is called Mozilla, which recalls the name of the
  original Netscape product

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Growth of the World Wide Web
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Business of Providing Internet Access

• NAPs provide Internet access to large
  organizations and businesses
• Internet access providers (IAPs) or Internet
  service providers (ISPs) get Internet access
  from NAPs and provide individuals and other
  businesses with access to the Internet
• Commerce service providers (CSPs) large ISPs
  that sell Internet access along with other
  services to businesses

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Hierarchy of Internet Service Providers
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Connection Bandwidth

• Bandwidth amount of data that can travel through
  a communications circuit in one second
• Bandwidth depends on the type of connection ISP
  has to the Internet and the kind of connection
  you have to the ISP
• Available bandwidth for any type network
  connection between two points is limited to
  narrowest bandwidth that exists in any part of
  the network

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Connection Bandwidth

• Bandwidth measured in bits per second (bps)
• The available bandwidth for any type of network
  connection between two points is limited to the
  narrowest bandwidth that exists in any part of
  the network
• Discussions of bandwidth often use the terms
• Kilobits per second (Kbps), which is 1,024 bps
• Megabits per second (Mbps), which is 1,048,576
  bps
• Gigabits per second (Gbps), which is
  1,073,741,824 bps

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Connection Bandwidth

• POTS (or plain old telephone service) is one way
  to connect computers or networks over longer
  distances
• Modem short for modulator-demodulator
• Modulation converting a digital signal to an
  analog signal
• Demodulation converting that analog signal back
  into digital form
• Digital Subscriber Line (DSL) higher grade of
  service offered by some telephone companies

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Connection Bandwidth

• Integrated Services Digital Network (ISDN) first
  technology developed using a DSL protocol offers
  bandwidths up to 256 Kbps
• Asymmetric Digital Subscriber Line (ADSL) offers
  transmission speeds ranging from 16 Kbps to 9
  Mbps
• T1 or T3 connections often used by businesses
  and large organizations much more expensive than
  POTS or ISDN connections
• NAPs use newer connections that have bandwidths
  of more than 1 Gbpsin some cases exceeding 10
  Gbps

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Connection Bandwidth

• Internet 2 operated by group of research
  universities and the NSF has backbone bandwidths
  greater than 10 Gbps
• Cable connection can deliver up to 10 Mbps to an
  individual user and can accept up to 768 Kbps
  from an individual user
• Satellite connection appeals to users in remote
  areas can download at a bandwidth of
  approximately 400 Kbps
• Broadband general term that describes any
  Internet connection that is faster than POTS
• Fixed-point wireless connections use technology
  similar to wireless LANs available in limited
  areas and prices are variable

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Summary

• The Internet is a truly amazing phenomenon
• Began as a scientific research project
• Grew to its current role as a global
  communications network linking more than a
  billion persons, businesses, organizations, and
  governments
• The Internet has made information available on a
  scale never before imagined

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Summary

• The Internet is composed of interconnected
  client/server networks
• The Internet grew rapidly, especially after the
  Web became available as a new way of using the
  Internet
• There are several choices for bandwidth and
  pricing choices when connecting to the Internet