meljun cortes computer organization lecture chapter22

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



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



Ways of Connecting Dial-up

Analog

ISDN

Dedicated DSL

Cable

LAN

Wireless

Satellite



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



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



UARTS on Modems



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



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



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



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



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



Dial-up Networking Completing the setup of a dial-up Internet connection



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



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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E-mail

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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E-mail

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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meljun cortes computer organization lecture chapter22

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