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The InternetChapter 22
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Overview
• In this chapter, you will learn to
– Explain how the Internet works
– Connect to the Internet
– Use Internet software tools
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How the Internet Works
Historical/Conceptual
InternetInternet
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Internet Tiers
• Tier 1 (main tier)– Nine companies – Own long-distance, high-speed fiber optic networks
called backbones– Interconnect at network access points (NAPs) in
major cities
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Internet Tiers
• Tier 2– Smaller regional networks– Larger ISPs that provide Internet access are often
Tier 2 providers
• Tier 3– Even more regional networks
• Built-in redundancy– Decentralized– Can easily adapt to
failures on network
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TCP/IP: Language of the Internet
• TCP/IP is the common language of the Internet– Suite of protocols
• Hypertext Transport Protocol (HTTP) – Most common protocol that provides structure for
the World Wide Web
• An Internet browser uses HTTP– Internet Explorer– Mozilla Firefox
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Internet Service Providers
• Internet service providers (ISPs) gain access to Internet through backbone– Leased from Tier 1 and Tier2 providers
• Users gain access to the Internet thru ISPs
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• Connecting to an ISP requires– Hardware for connectivity
• Modem and working phone line• DSL or cable modem
– Software (protocols)• Governs the connection and data flow
Connection Concepts
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CompTIA A+Essentials
Essentials
Getting the Right Sound Card
Connecting to the Internet
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Ways of Connecting
• Dial-up– Analog– ISDN
• Dedicated– DSL– Cable– LAN
• Wireless
• Satellite
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Dial-up Requires a Modem
• The term modem is an abbreviation for modulator/demodulator– Enables computers to communicate with each
other via standard telephone lines
– Converts analog signals into digital signals
– Converts digital signalsinto analog signals
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Modems
• A modem uses serial communication– Transmits data as a series of individual 1s and 0s
• Universal asynchronous receiver/transmitter (UART)– Converts serial into
8-bit parallel data
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UARTS on Modems
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• Baud rate is the basic cycle of time that a modem uses as its carrier frequency– Maximum baud rate of a phone line is 2400 baud
• The modem speed is measured in bits per second (bps)– Modems can pack multiple bits into a single baud– 14 bits × 2400 baud = speed of 33.6 Kbps
Baud Rate
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• Modern modem standards are referred to as V standards
– Set by the International Telecommunication Union—Telecommunications Standardization Sector (ITU-T)
– Both standards offer download speeds of just under 56 Kbps
• V.90 upload speeds of up 33.6 Kbps• V.92 upload speeds of up to 48 Kbps
• Rarely get throughput greater than 48 Kbps
Communication Standards
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Flow Control (Handshaking)
• Hardware flow control uses extra wires called ready to send (RTS) and clear to send (CTS)
– Called RTS/CTS
– When in doubt, use hardware flow control
• PCs handle local flow control using hardware or software
• Software flow control uses special characters to signal the beginning and end of data transmission
– Called XON/XOFF
– Slower than hardware flow control and rarely used today
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Modem Connections
• Modems connect to the PC in one of two ways– Internal modems connect to a
PCI or PCI Express expansion slot
– External modems connect through a serial port or USB port
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Dial-up Networking
• Dial-up networking
– Uses information from your ISP • The dial-up phone number, username, password, and other
special configuration parameters
– Configured in Network and Internet Connections applet
• Select Set up or change your Internet connection and use the wizard
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Dial-up Networking
• Completing the setup of a dial-up Internet connection
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Dial-up Networking
• Uses PPP protocol– Point-to-Point protocol (PPP)– Streaming protocol developed especially for dial-up
Internet access
• Most dial-up errors are user errors– Turn the volume up and verify the connection– Listen for a dial tone– Listen for “modem talk” instead of a person
answering the phone
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ISDN
• Integrated Services Digital Network (ISDN)– Phone companies have upgraded their network
infrastructures to all digital lines (except for the line from your phone to the central office)
– ISDN uses channels• B (Bearer) used for data and voice at 64 Kbps• D (Delta) used for setup and configuration information at
16 Kbps
• Basic Rate Interface (BRI)– Most common setup– Two B (total of 128 Kbps) and one D channel
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DSL
• Digital subscriber line (DSL)– Uses a regular phone line but special equipment at
both ends
– Much faster than dial-up:• Upload: 384 Kbps• Download: 2 Mbps or greater
– Installation requires a NIC and DSL receiver (often called a DSL modem)
– Must be within 18,0000 feetfrom the closest main phoneservice switching center
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Cable
• Cable– Uses cable TV connections
• Connect the RG-6 or RG-59 coaxial cable to a cable modem• Connect modem to a NIC in the PC with UTP cable
– Very fast speeds—as fast as DSL or faster– Bandwidth is shared with other users, which can
affect performance
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Other Internet Connections
• LANs– Most companies connect their network to the Internet
through an ISP– Users connect through the LAN
• Wireless– Wireless connections require access via wired network– If wired network has access, wireless devices can use this
wired network via a WAP
• Satellite– Uploads previously done through modem– Initial connections still must be made through a modem
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Internet Connection Sharing
• Internet connection sharing (ICS)– Allows one computer to share single Internet
connection with multiple devices– Available since Windows 98 SE– Requires a LAN between
the devices first
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Windows XP Firewall
• Built into Windows XP– Originally named Internet Connection Firewall (ICF)– Changed to Windows Firewall in SP2
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Internet Software Tools
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World Wide Web
• The World Wide Web (WWW) provides a graphical face for the Internet– Web servers house Web sites– Web browsers access the files on Web servers
• Web browsers are highly configurable– A proxy server enables multiple connections to the
Internet to go through one protected PC• Similar to ICS, but more sophisticated
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World Wide Web
• Security and scripts– Active programs and scripts
such as Java and Active Server Pages
• Can be useful and powerful• Can be malicious
– Internet Explorer has configurable options
• Tools | Internet Options | Security tab lets you set security levels
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HTTP vs. HTTPS
• HTTP provides no encryption
• HTTP over Secure Sockets Layer (HTTPS)– Provides encryption– Use when submitting personal information such as
credit card numbers, phone numbers, etc.– Verify HTTPS is being used two ways
• Lock icon • HTTPS appears in address bar
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• Two most popular e-mail programs– Microsoft Outlook Express– Mozilla Thunderbird
• E-mail protocols– Post Office Protocol version 3 (POP3)
• Used for receiving e-mail
– Internet Message Access Protocol (IMAP)• Used for receiving mail, but with more features than POP3
– Simple Mail Transfer Protocol (SMTP)• Used for sending e-mail
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• Configuring e-mail– Can use name or IP
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Newsgroups
• Use a newsreader program to access newsgroups
– Outlook Express most common newsreader (free)
– News servers run Network News Transfer Protocol (NNTP)
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File Transfer Protocol
• File Transfer Protocol (FTP)– Used to share files
– Requires an FTP server on one end and an FTP client on the other
• WS_FTP is a popular client• Internet Explorer and
other Web browsers also support FTP
– Public FTP servers allow anonymous login
• User Name: Anonymous• Password: e-mail address
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Voice over IP
• Voice over IP (VoIP)– Enables voice calls over the network
– Works with any type of high-speed connection • DSL, cable, satellite, etc.
– VoIP is a collection of protocols• Not a single protocol
– Vendors• Skype• Vonage
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Terminal Emulation
• Allows access to other computers as if you were there
• University of Cambridge’s VNC– Free and totally cross-platform– Can run and control
Windows from a Macintosh system
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Terminal Emulation
• Remote Desktop – Microsoft’s
implementation– Free and built into
system
• Remote Assistance– End user requests help– Helper can take control
of desktop • If permission granted
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Beyond A+
• Online gaming– World of Warcraft (WOW)
• Chat– Internet
Relay Chat (IRC)
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Beyond A+
• File sharing– Allows users to share files with other users
• Users can access any shared files (such as MP3s) on any computer anywhere on the Internet
• Napster and Kazaa are file sharing programs
– Music industry trying to stop file sharing
– BitTorrent protocol to counter music industry
• Also used for Linux distributions
• µTorrent is one program using BitTorrent protocol
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