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8/13/2019 MELJUN CORTES Computer Organization Lecture Chapter22
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Chapter 22
The Internet
MELJUN CORTES
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MELJUN CORTES
2007 The McGraw-Hill Companies, Inc. All rights reserved
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
Internet
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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 ofthe 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 toInternet through backbone
Leased from Tier 1 and Tier2 providers
Users gain access to
the Internet thru ISPs
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Connection Concepts
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
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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 modemis 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
Baud rateis the basic cycle of time that a modemuses as its carrier frequency
Maximum baud rate of a phone line is 2400 baud
The modem speedis measured in bits per
second (bps)
Modems can pack multiple bits into a single baud
14 bits 2400 baud = speed of 33.6 Kbps
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Communication Standards Modern modem standards are referred to asV
standards
Set by the International Telecommunication UnionTelecommunications Standardization Sector (ITU-T)
Both standards offer download speeds of just under56 Kbps V.90 upload speeds of up 33.6 Kbps
V.92 upload speeds of up to 48 Kbps
Rarely get throughput greater than48 Kbps
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Flow Control (Handshaking)
Hardware flow controlusesextra wires called ready to
send(RTS) and clear tosend(CTS)
Called RTS/CTS
When in doubt, usehardware flow control
PCs handle local flow control usinghardware or software
Software flow controluses special
characters to signalthe beginning and endof data transmission
Called XON/XOFF
Slower than hardwareflow control and rarelyused today
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Modem Connections
Modems connect to the PC in one oftwo 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 answeringthe phone
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ISDN Integrated Services Digital Network(ISDN)
Phone companies have upgraded their networkinfrastructures to all digital lines (except for the linefrom 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 feet
from the closest main phone
service 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 speedsas 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 betweenthe 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 agraphical face for the Internet
Web servers house Web sites
Web browsers access the files on Web servers
Web browsersare highly configurable
A proxy serverenables 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 scriptsActive 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
HTTPSappears in address bar
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Two most popular e-mailprograms 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 accessnewsgroups
Outlook Express most common newsreader (free)
News servers run Network
News Transfer Protocol
(NNTP)
Fil T f P l
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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 anonymouslogin
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 werethere
University of Cambridges VNC
Free and totally cross-platform Can run and control
Windows from a
Macintosh system
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Terminal Emulation
Remote Desktop Microsofts 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
InternetRelay
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 anycomputer anywhere on the Internet
Napster and Kazaa are file sharing programs
Music industry trying tostop file sharing
BitTorrent protocol to
counter music industry Also used for Linux
distributions
Torrent is one programusing BitTorrent protocol
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