xp new perspectives on the internet, 4e tutorial 1 1 introduction to the internet and the world wide...

New Perspectives on the Internet, 4e

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Introduction to the Internet and the World Wide Web

History, Structure, and Getting Connected


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XPObjectives

• 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 and the World Wide Web began and grew

• Compare different methods for connecting to the Internet


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XPInternet and World Wide Web:Amazing Developments

• Large collection of computers all over the world connected to one another.

• One of the most amazing technological developments of the 20th century.


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XPTools and Resources

• Information Resources

• Electronic Mail (E-Mail)

• Software Downloads

• Discussions


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XPTools and Resources

• Entertainment

• Retail Business

• Business-to Business Communication


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XPComputer 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 resources with computers it is connected to.


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XPClient/Server Local Area Networks

• 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 Networks: used to connect computers that are located close together.

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Client/Server Network


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XPConnecting Computers to a Network – Types of Cable

• Twisted Pair: oldest type, used by telephone companies, usually Category 1.

• Coaxial Cable: 20 times faster than Category 1, more expensive

• Category 5: carries signals between 10 & 100 times faster than coaxial cable, easy to install.

• Fiber-optic cable: most expensive, transmits pulsing beams of light through very thin strands of glass, fastest transmission rate.

Types of Cable


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TWISTED-PAIR

COAXIAL

FIBER-OPTIC


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XPConnecting Computers to a Network – Wireless Networks

• Becoming more common as costs continue to drop.

• Wireless LANs are welcome in organizations that occupy old buildings.

• Popular with companies whose employees use laptop computers.


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XPWide Area Networks

• WAN: a network of networks or an internet.

• Internet: a worldwide collection of interconnected networks; owners have voluntarily agreed to share resources and network connections.


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XPOrigins 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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XPConnectivity: Circuit Switchingvs Packet Switching

• Circuit switching: centrally controlled single-connection method used by most local telephone traffic today

• All data travels along that single connection.


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• 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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• 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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XPOrigins 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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XPOpen 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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• 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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• 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.

• Vincent Cerf considered to be the father of the Internet by many.


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XPBirth 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.


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XPMore 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 lists (LISTSERV), information posting areas (Usenet), and adventure games among new applications appearing on the ARPANET.

Interconnecting the Networks


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XPCommercial 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.

• NSF permitted two commercial e-mail services, MCI Mail and CompuServe, to establish limited connections to the Internet in 1989.


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XP

• Intranet: LANs or WANs that use TCP/IP protocol but do not connect to sites outside the firm.

• Extranet: an intranet that allows selected outside parties to connect.

• Internet Engineering Task Force (IETF): a self-organized group that makes technical contributions to the engineering of the Internet and its technologies.


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XPGrowth of the Internet

• ARPANET grew from 4 computers in 1969 to over 300,000 by 1990.

• Greatest growth in the Internet was yet to come.

• Formal definition of Internet was adopted in 1995 by the Federal Networking Council (FNC).

From Research Project to Information Infrastructure

Source: Internet Software Consortium (http://www.isc.org/)

Year


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180160140120100 80 60 40 20 0

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

Growth in the Number of Internet Hosts


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XPGrowth 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.


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XPNew Structure for the Internet

• Organized around four network access points (NAPs), operated by four different tele-communications companies.

• 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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• More than 170 million connected host computers and more than 700 million worldwide Internet users.

• TCP/IP numbering system that identifies users on the Internet is running short of numbers. IP version 4 provides a maximum of about 4 billion

addresses. IP version 6 approved in 1997 by the IETF allows existing

users to continue accessing the Internet while new system is being implemented.


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• 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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XPWorld Wide Web

• World Wide Web: a way of thinking about information storage and retrieval.

• Two important innovations played key roles: hypertext graphical user interfaces (GUIs)


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XPOrigins of Hypertext

• 1945: Vannevar Bush speculated engineers would eventually build a machine 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.

• 1960’s: Douglas Engelbart created first experimental hypertext system on one of the large computers.


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XPHypertext 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 Server: a computer that stores files written in HTML; other computers connect to it and read files.

• Hypertext Link (hyperlink): points to another location in the same or another HTML document.


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XPHypertext and Graphical UserInterfaces Come to the Internet

• Web Browser: software that lets users read HTML documents and move from one HTML document to another through hypertext link tags in each file.

• HTML: a subset of Standard Generalized Markup Language (SGML).

• SGML: has been used by organizations for many years to manage large document-filing systems.

• GUI (graphical user interface): a way of presenting program output using pictures, icons, and other graphical elements.


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XPThe 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 was an instant success.

• Internet Explorer Web browser entered the market soon after Netscape’s success became apparent.

Growth of the World Wide Web

Source: Adapted from Netcraft Web Survey (http://www.netcraft.com/survey/Reports)

Year


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4540353025201510

50

1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

Estimated number of Web sites (in millions)


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XPConnection Options

• NAPs (network access points) offer connections to large organizations and businesses.

• Those businesses provide Internet access to other business and individuals as ISPs.

• Internet service providers (ISPs) provide customers with software to connect to the ISP, browse the Web, send and receive e-mail messages, and perform other Internet-related functions.

Hierarchy of Internet Service Providers


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XPConnection 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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• Bandwidth measured in bits per second (bps).

• When you extend your network beyond a local area, the speed of the connection depends on type of connection used.

• POTS (or plain old telephone service) is one way to connect computers or networks over longer distances.


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• Digital Subscriber Line (DSL): higher grade of service offered by some telephone companies.

• 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.


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• Internet 2: operated by group of research universities and the NSF; has backbone bandwidths greater than 10 Gbps.

• Cable connection: increasingly available in the U.S.; can deliver up to 10 Mbps to an individual user.

• Satellite: appealing to users in remote areas; can download at a bandwidth of approximately 400 Kbps.

• Fixed-point wireless connections: offered by some companies technology similar to wireless LANs limited and more expensive.


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XPConnecting Through YourSchool or Employer

• Many universities and community colleges offer Internet access to their students, faculty members, and other employees.

• Your employer might offer you a connection to the Internet through the computer you use in your job.

• Most schools and employers have an acceptable use policy (AUP) that specifies the conditions under which you can use their Internet connections. possibly least expensive option should carefully consider if limitations placed on use of the

Internet are greater than the benefits


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XPConnecting Through anInternet Service Provider

• ISP may be the best way for you to connect to the Internet.

• ISPs offer modem connections to individuals and higher speed connections to businesses.

• May also offer DSL connections to individual and business customers.

• Fewer ISPs in smaller towns and rural areas lessen competition.


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XPConnecting Through anInternet Service Provider

• Reliable connectivity at a reasonable price.

• Terms of AUPs often less restrictive than those imposed by schools and employers.

• Quality of service may deteriorate significantly over time if ISP adds many new customers without expanding bandwidth.


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XPConnecting Through YourCable Television Company

• Cable modem converts digital signals into radio-frequency analog signals similar to television transmission signals.

• Signals travel over the same lines that carry cable television signals.

• Cable connection can provide very fast downloads to your computer from the Internet (up to 170 times faster than a telephone line connection).

• Greatest disadvantage for most people is that cable connection is not available in all areas.


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XPConnecting Through a DSL Provider

• Connections increasingly available in the U.S. and a few other countries.

• Speeds similar to cable modems.

• Subscription rates similar.

• Sometimes long delays in installation and repair services.


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XPConnecting by Satellite

• Satellite Internet connections may be only option available in rural areas.

• Speeds and monthly fees similar to those of cable and DSL providers.

• Installation fee usually considerably higher because the dish must be installed and aimed at the satellite.


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XPSummary

• The Internet and the Web began in the military and research communities.

• The Internet and the Web have become an important worldwide infrastructure.

• The Internet and the Web support many resources through one of the most powerful communication tools the world has ever known.

• There are a number of options for connecting your computer and the computers of businesses and other organizations to the Internet.

xp new perspectives on the internet, 4e tutorial 1 1 introduction to the internet and the world wide...

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