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The Internet and the World Wide Web

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    The Internet and the World Wide Web The Internet and the World Wide Web Presentation Transcript

    • Appendix A The Internet and the World Wide Web
    • 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
    • Internet and World Wide Web: Amazing 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 20 th 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
    • 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
    • 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
    • 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
    • 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
    • A Client/Server LAN
    • 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
    • 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
    • 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
    • Types of Cable TWISTED-PAIR COAXIAL FIBER-OPTIC
    • 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
    • A Wireless Home Network
    • 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
    • Connectivity: Circuit Switching vs. 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
    • Connectivity: Circuit Switching vs. 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
    • Connectivity: Circuit Switching vs. 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
    • 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
    • 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
    • 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
    • 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
    • Birth of E-Mail: A 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
    • 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 BITNET’s LISTSERV ), information posting areas (such as the User’s News Network , or Usenet , newsgroups ), and adventure games were among the new applications appearing on the ARPANET
    • 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
    • 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
    • Networks That Became the Internet
    • 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
      • 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
      Commercial Interest Increases
    • Growth of the Internet
      • Formal definition of Internet was adopted in 1955 by the Federal Networking Council (FNC)
    • 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
    • Growth in the Number of Internet Hosts
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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 Internet’s 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
    • 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
    • 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
    • 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
    • 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)
    • Origins of Hypertext
      • 1945: Vannevar Bush speculated engineers would eventually build a machine ( Memex ) that would store a person’s 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
    • Hypertext and Graphical User Interfaces 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
    • Hypertext and Graphical User Interfaces 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
    • Hypertext and Graphical User Interfaces 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
    • Hypertext and Graphical User Interfaces 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
    • Hypertext and Graphical User Interfaces Come to the Internet
    • The Web and Commercialization of 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 Netscape’s success became apparent
    • The Web and Commercialization of 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
    • Growth of the World Wide Web
    • 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
    • Hierarchy of Internet Service Providers
    • 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
    • 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
    • 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
    • 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 Gbps—in some cases exceeding 10 Gbps
    • 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
    • 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
    • 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