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Technology in ActionTechnology in Action

Chapter 13Chapter 13

Behind the Scenes: Behind the Scenes:

The Internet: How It WorksThe Internet: How It Works

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Chapter TopicsChapter Topics

• Managing the InternetManaging the Internet• Interaction between Internet componentsInteraction between Internet components• Internet data transmission and protocolsInternet data transmission and protocols• IP addresses and domain namesIP addresses and domain names• FTP and TelnetFTP and Telnet• HTML and XLMHTML and XLM• How e-mail and instant messaging work How e-mail and instant messaging work

and how to keep them secureand how to keep them secure

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Management of the InternetManagement of the Internet• Who owns the Who owns the

Internet?Internet?– IndividualsIndividuals– UniversitiesUniversities– Government agenciesGovernment agencies– Private companiesPrivate companies

• Who manages the Who manages the Internet?Internet?– Nonprofit organizationsNonprofit organizations– User groupsUser groups

• Who pays for the Who pays for the Internet?Internet?

– U.S. taxpayersU.S. taxpayers– BusinessesBusinesses– UniversitiesUniversities– Other countriesOther countries

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Connecting Internet Service Connecting Internet Service ProvidersProviders

• Internet backboneInternet backbone– Collection of large national and international networksCollection of large national and international networks– Verizon, AT&T, Sprint Nextel, QwestVerizon, AT&T, Sprint Nextel, Qwest

• T lines – High-speed fiber-optic communications lines designed to provide high throughput– T-1 lines– T-2 lines– T-3 lines– T-4 lines

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Network Access Points (NAPs)Network Access Points (NAPs)

• Points of connection between ISPs Points of connection between ISPs – Once known as network access points (NAPs)Once known as network access points (NAPs)

• Private sector companies make up the Internet Private sector companies make up the Internet system system – Exchange data via Internet Exchange Points (IXPs) Exchange data via Internet Exchange Points (IXPs)

• Switches send data on a specific route through Switches send data on a specific route through the networkthe network

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Points of Presence (POP)Points of Presence (POP)• Bank of modems where individual users Bank of modems where individual users

connect to an ISPconnect to an ISP

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The Network Model of the InternetThe Network Model of the Internet

• Internet communications follows the client/server Internet communications follows the client/server network modelnetwork model

• Clients request servicesClients request services• Servers respond to requestsServers respond to requests

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The Network Model of the InternetThe Network Model of the Internet

• Types of serversTypes of servers– Web serversWeb servers

• Host Web pagesHost Web pages

– Commerce serversCommerce servers• Enable the purchase of goods and services over the InternetEnable the purchase of goods and services over the Internet

– File serversFile servers• Provide remote storage space for files that users Provide remote storage space for files that users

can downloadcan download

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P2P File SharingP2P File Sharing

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Data Transmission and ProtocolsData Transmission and Protocols

• Computer protocols are rules for electronic Computer protocols are rules for electronic information exchangeinformation exchange

• Open system protocolsOpen system protocols– Any computer can communicate with other Any computer can communicate with other

computers using the same protocolscomputers using the same protocols

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Circuit SwitchingCircuit Switching

• Dedicated connection between two pointsDedicated connection between two points

• Remains active until the transmission is Remains active until the transmission is terminatedterminated

• Used in telephone communicationsUsed in telephone communications

• Inefficient for computersInefficient for computers

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Packet SwitchingPacket Switching

• Data is broken into small units called packetsData is broken into small units called packets• Packets are sent over various routes to their Packets are sent over various routes to their

destinationdestination• Packets are reassembled by the receiving Packets are reassembled by the receiving

computercomputer• Packets containPackets contain

– Destination/source addressesDestination/source addresses– Reassembling instructionsReassembling instructions– Data Data

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Packet SwitchingPacket Switching

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TCP/IPTCP/IP

• Transmission Control Protocol (TCP)Transmission Control Protocol (TCP)– Prepares data for transmissionPrepares data for transmission– Provides error-checkingProvides error-checking– Enables resending lost dataEnables resending lost data

• Internet Protocol (IP)Internet Protocol (IP)– Responsible for sending data from one Responsible for sending data from one

computer to anothercomputer to another

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IP AddressesIP Addresses

• Unique number that identifies devices Unique number that identifies devices connected to the Internetconnected to the Internet

• Typical IP addressTypical IP address– 197.24.72.157197.24.72.157

• Static addressStatic address– Address never changesAddress never changes

• Dynamic addressDynamic address– Temporary addressTemporary address

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Having Enough IP AddressesHaving Enough IP Addresses

• IPv4 addressing scheme didn’t foresee IPv4 addressing scheme didn’t foresee explosive growthexplosive growth

• CIDR (Classless Inter-Domain Routing)CIDR (Classless Inter-Domain Routing)– Allows a single IP address to represent Allows a single IP address to represent

several unique addressesseveral unique addresses– Uses a network prefix (slash and number)Uses a network prefix (slash and number)– Identifies how many bits in the IP address are Identifies how many bits in the IP address are

unique identifiersunique identifiers

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Having Enough IP AddressesHaving Enough IP Addresses

• Internet Protocol version 6 (IPv6)Internet Protocol version 6 (IPv6)– Longer IP addressesLonger IP addresses– Easier for non-PC devices to connect to the Easier for non-PC devices to connect to the

InternetInternet

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Domain NamesDomain Names

• Name that takes the place of an IP addressName that takes the place of an IP address• Sample domain nameSample domain name

– www.mywebsite.comwww.mywebsite.com• Top-level domains (TLD)Top-level domains (TLD)

– Portion of the domain name that follows the dotPortion of the domain name that follows the dot– Sample top-level domain namesSample top-level domain names

• .com.com, , .org.org, , .edu.edu, and , and .net.net

• Second-level domainsSecond-level domains– Unique name within a top-level domainUnique name within a top-level domain– Sample second-level domain namesSample second-level domain names

• Yahoo.comYahoo.com, , Google.comGoogle.com, and , and Unesco.orgUnesco.org

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Domain Name ServersDomain Name Servers

• Internet servers that translate domain Internet servers that translate domain names to IP addressesnames to IP addresses

• ISPs go first to a default DNS to resolve a ISPs go first to a default DNS to resolve a namename

• Name queries work up the hierarchy to the Name queries work up the hierarchy to the root DNS servers if requiredroot DNS servers if required

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Other ProtocolsOther Protocols

• File Transfer Protocol (FTP)File Transfer Protocol (FTP)– File-sharing protocolFile-sharing protocol– Files are downloaded and uploaded using Files are downloaded and uploaded using

the Internetthe Internet

• TelnetTelnet– Protocol for connecting to a remote computer Protocol for connecting to a remote computer

and a TCP/IP serviceand a TCP/IP service– Enables a client computer to control a server Enables a client computer to control a server

computercomputer

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HTTP and SSLHTTP and SSL• Hypertext Transfer ProtocolHypertext Transfer Protocol

– Protocol for transferring hypertext documentsProtocol for transferring hypertext documents– Hypertext documents are linked to other Hypertext documents are linked to other

documents (through hyperlinks) documents (through hyperlinks)

• Secure HyperText Transfer Protocol Secure HyperText Transfer Protocol (S-HTTP)(S-HTTP)

• Secure Socket LayerSecure Socket Layer– Security protocols that protect sensitive Security protocols that protect sensitive

informationinformation– Encrypts dataEncrypts data

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HTML/XHTMLHTML/XHTML• Hypertext Markup Language (HTML)Hypertext Markup Language (HTML)

– Format for creating Web pagesFormat for creating Web pages• Extensible Hypertext Markup Language (XHTML)Extensible Hypertext Markup Language (XHTML)

– Successor to HTMLSuccessor to HTML– Has much more stringent rules regarding taggingHas much more stringent rules regarding tagging

• HTML/XHTML HTML/XHTML – Not programming languages but sets of rules for marking up blocks of text so that a browser knows how to display Not programming languages but sets of rules for marking up blocks of text so that a browser knows how to display

them them

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HTML/XHTML ExampleHTML/XHTML Example

<h1>This is the Heading</h1>

<p><font face="Arial">This is text using Arial font.</font></p>

<p><font face="Arial"><i>This text is italicized</i>.</font></p>

<p><font face="Arial"><b>This text is bold</b>.</font></p>

<p><font face="Arial"><font color="#FF0000">This text color is red</font>.</font></p>

<p><font face="Arial">This is a hyperlink <a href="http://vig.prenhall.com/">www.prenhall.com</a></font></p>

HTML/XHTML Web Page Display

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Extensible Markup Language Extensible Markup Language (XML)(XML)

• Designed for information exchangeDesigned for information exchange

• Tools used to create your own markup Tools used to create your own markup languagelanguage

• Used in e-commerce transactionsUsed in e-commerce transactions

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Common Gateway Interface (CGI)Common Gateway Interface (CGI)• Browsers request that a program file executes Browsers request that a program file executes

(runs)(runs)• CGI files often called CGI scriptsCGI files often called CGI scripts• Adds Web page interactionAdds Web page interaction

– Adding names to guest books/mailing listsAdding names to guest books/mailing lists– Completing formsCompleting forms

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Client-Side ApplicationsClient-Side Applications• A program that runs on a client computer A program that runs on a client computer

with no interaction with the serverwith no interaction with the server• Types of client-side applications includeTypes of client-side applications include

– HTML/XHTML document embedded with HTML/XHTML document embedded with JavaScript codeJavaScript code

– Applet: Small program that resides on the Applet: Small program that resides on the serverserver

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Communications Over the InternetCommunications Over the Internet• E-mailE-mail

– Simple Mail Simple Mail Transfer Transfer Protocol (SMTP)Protocol (SMTP)

– Multipurpose Multipurpose Internet Mail Internet Mail Extensions Extensions (MIME)(MIME)

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Communications Over the InternetCommunications Over the Internet

• E-mail securityE-mail security– Encryption Encryption

• Private-key encryptionPrivate-key encryption• Public-key encryptionPublic-key encryption

– Secure data transmission softwareSecure data transmission software• SafeMessage SafeMessage

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Instant Messaging (IM)Instant Messaging (IM)

• Client/server program for real-time, text-Client/server program for real-time, text-based conversationsbased conversations

• Popular IM programsPopular IM programs– AOL Instant MessengerAOL Instant Messenger– ICQICQ– Yahoo! MessengerYahoo! Messenger– MSN MessengerMSN Messenger

• Increasing security threatsIncreasing security threats– Should not be used for sensitive dataShould not be used for sensitive data

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Chapter 13 Summary QuestionsChapter 13 Summary Questions

• Who manages and pays for the Internet? Who manages and pays for the Internet?

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Chapter 13 Summary QuestionsChapter 13 Summary Questions

• How do the Internet’s networking How do the Internet’s networking components interact?components interact?

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Chapter 13 Summary QuestionsChapter 13 Summary Questions

• What data transmissions and protocols What data transmissions and protocols does the Internet use?does the Internet use?

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Chapter 13 Summary QuestionsChapter 13 Summary Questions

• Why are IP addresses and domain names Why are IP addresses and domain names important for Internet communications?important for Internet communications?

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Chapter 13 Summary QuestionsChapter 13 Summary Questions

• What are FTP and Telnet, and how do I What are FTP and Telnet, and how do I use them?use them?

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Chapter 13 Summary QuestionsChapter 13 Summary Questions

• What are HTML and XML used for?What are HTML and XML used for?

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Chapter 13 Summary QuestionsChapter 13 Summary Questions

• How do e-mail and instant messaging How do e-mail and instant messaging work, and how are messages kept work, and how are messages kept secure?secure?