Chapter 22

The Internet

MELJUN CORTESMELJUN CORTES

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OverviewIn this chapter, you will learn to

Explain how the Internet works

Connect to the Internet

Use Internet software tools

How the Internet Works

Historical/Conceptual

Internet

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Internet TiersTier 1 (main tier)

Nine companies Own long-distance, high-speed fiber optic networks called

backbonesInterconnect at network access points (NAPs) in major cities

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Internet TiersTier 2

Smaller regional networksLarger ISPs that provide Internet access are often Tier 2

providers Tier 3

Even more regional networksBuilt-in redundancy

DecentralizedCan easily adapt to

failures on network

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TCP/IP: Language of the InternetTCP/IP is the common language of

the InternetSuite of protocols

Hypertext Transport Protocol (HTTP) Most common protocol that provides structure for the World

Wide Web

An Internet browser uses HTTPInternet ExplorerMozilla Firefox

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Internet Service ProvidersInternet service providers (ISPs) gain access to Internet

through backboneLeased from Tier 1 and Tier2 providers

Users gain access to the Internet thru ISPs

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Connection ConceptsConnecting to an ISP requires

Hardware for connectivity Modem and working phone line DSL or cable modem

Software (protocols) Governs the connection and data flow

CompTIA A+Essentials

Essentials

Getting the Right Sound Card

Connecting to the Internet

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Ways of ConnectingDial-up

AnalogISDN

DedicatedDSLCableLAN

Wireless

Satellite

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Dial-up Requires a Modem The term modem is an abbreviation for

modulator/demodulatorEnables 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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ModemsA 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 RateBaud rate is the basic cycle of time that a modem uses as its

carrier frequencyMaximum 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 baud14 bits × 2400 baud = speed of 33.6 Kbps

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Communication StandardsModern 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

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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 ConnectionsModems connect to the PC in one of

two waysInternal 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 NetworkingDial-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 NetworkingCompleting the setup of a dial-up Internet connection

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Dial-up NetworkingUses PPP protocol

Point-to-Point protocol (PPP)Streaming protocol developed especially for dial-up Internet access

Most dial-up errors are user errorsTurn the volume up and verify the connectionListen for a dial toneListen for “modem talk” instead of a person answering the phone

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ISDNIntegrated 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 setupTwo B (total of 128 Kbps) and one D channel

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DSLDigital 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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CableCable

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 fasterBandwidth is shared with other users, which can affect

performance

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Other Internet ConnectionsLANs

Most companies connect their network to the Internet through an ISPUsers connect through the LAN

WirelessWireless connections require access via wired networkIf wired network has access, wireless devices can use this wired network via a

WAP

SatelliteUploads previously done through modemInitial 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 devicesAvailable since Windows 98 SERequires a LAN between

the devices first

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Windows XP FirewallBuilt into Windows XP

Originally named Internet Connection Firewall (ICF)Changed to Windows Firewall in SP2

Internet Software Tools

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World Wide WebThe World Wide Web (WWW) provides a graphical face

for the InternetWeb servers house Web sitesWeb browsers access the files on Web servers

Web browsers are highly configurableA 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 WebSecurity 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. HTTPSHTTP provides no encryption

HTTP over Secure Sockets Layer (HTTPS)Provides encryptionUse 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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E-mailTwo most popular e-mail programs

Microsoft Outlook ExpressMozilla Thunderbird

E-mail protocolsPost 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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E-mail• Configuring e-mail

– Can use name or IP

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NewsgroupsUse 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 EmulationAllows access to other computers as if you were there

University of Cambridge’s VNCFree and totally cross-platformCan run and control

Windows from a Macintosh system

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Terminal EmulationRemote Desktop

Microsoft’s implementationFree and built into system

Remote AssistanceEnd user requests helpHelper can take control

of desktop If permission granted

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Beyond A+

Online gamingWorld of Warcraft (WOW)

ChatInternet

Relay Chat (IRC)

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Beyond A+

File sharingAllows 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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