The Internet book: everything you need to know about computer networking and how the Internet works

405 Pages·2019·5.46 MB·English

by  Douglas, Comer

The Internet Book

Everything You Need to Know
about Computer Networking
and How the Internet Works

Fifth Edition

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The Internet Book

Everything You Need to Know
about Computer Networking
and How the Internet Works

Fifth Edition

Douglas E. Comer
Departments of Computer Science and ECE
Purdue University
West Lafayette, IN

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CRC Press
Taylor & Francis Group
6000 Broken Sound Parkway NW, Suite 300
Boca Raton, FL 33487-2742

© 2019 by Taylor & Francis Group, LLC
CRC Press is an imprint of Taylor & Francis Group, an Informa business

No claim to original U.S. Government works

Printed on acid-free paper
Version Date: 20180730

International Standard Book Number-13: 978-1-138-33133-4 (Hardback)
International Standard Book Number-13: 978-1-138-33029-0 (Paperback)

This book contains information obtained from authentic and highly regarded sources. Reasonable efforts have been
made to publish reliable data and information, but the author and publisher cannot assume responsibility for the validity
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Library of Congress Cataloging-in-Publication Data

Names: Comer, Douglas, author.
Title: The Internet book : everything you need to know about computer
networking and how the Internet works / Douglas E. Comer.
Description: Fifth edition. | Boca Raton : Taylor & Francis, CRC Press, 2018.
| Includes bibliographical references and index.
Identifiers: LCCN 2018021320 | ISBN 9781138330290
Subjects: LCSH: Internet. | Computer networks. | World Wide Web.
Classification: LCC TK5105.875.I57 C65 2018 | DDC 004.67/8--dc23
LC record available at https://lccn.loc.gov/2018021320

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To Everyone Who
Is Curious

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Contents

xxiii
Preface

3
Chapter 1
The Internet Is Everywhere

1.1
Basic Facts Do Not Tell The Story 5

1.2
Imagine Life Without The Internet 5

1.3
Why You Should Understand Internet Technology 6

1.4
Learning About The Internet 6

1.5
Understanding The Big Picture 7

1.6
Terminology And Technology 7

1.7
Growth And Adaptability 8

1.8
The Impact Of The Internet 8

1.9
Organization Of The Book 8

1.10
A Personal Note 9

PART I
Before The Internet
11

15
Chapter 2
Telephones Everywhere

2.1
Introduction 15

2.2
A Communication Service 15

2.3
Selling Communication 15

2.4
Limited Access 16

2.5
High Cost 17

2.6
The Difficult Transition 17

2.7
Ubiquitous Access 18

2.8
Relevance To The Internet 19

2.9
Summary 19

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viii
Contents

23
Chapter 3
The World Was Once Analog

3.1
Introduction 23

3.2
Sound, Vibrations, And Analog Recording 23

3.3
Analog Electronic Devices 24

3.4
Many Electronic Devices Are Analog 25

3.5
The First Analog Communication 25

3.6
Sending An Analog Signal Across A Wire 26

3.7
Analog Is Simple But Inaccurate 27

3.8
A Definition Of Digital 27

3.9
Digital Music 28

3.10
Recording Sound As Numbers 28

3.11
Converting Between Analog And Digital Forms 31

3.12
Why Did Digital Music Take Over? 32

3.13
Summary 33

37
Chapter 4
The Past And Present Digital Network

4.1
Introduction 37

4.2
The World Was Previously Digital 37

4.3
A Telegraph Was Digital 38

4.4
Morse Code 38

4.5
Letters And Digits In Morse Code 39

4.6
Telegraph Users Did Not Encounter Morse Code 40

4.7
Virtually Instant Communication 40

4.8
Speed Is Relative 40

4.9
The Telephone Eventually Became Digital 41

4.10
Relevance To The Internet 41

4.11
Binary Encoding Of Data On The Internet 42

4.12
Why Use Two Symbols? 42

4.13
Summary 42

45
Chapter 5
Basic Communication

5.1
Introduction 45

5.2
Communication Using Electricity 45

5.3
Sending Signals 46

5.4
Using Signals To Send Information 46

5.5
Modem: A Modulator And A Demodulator Combined 47

5.6
How Modems Allow Two-Way Traffic 48

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Contents
ix

5.7
A Character Code For Digital Information 48

5.8
Bits And Bytes 50

5.9
Detecting Errors 50

5.10
Summary 51

55
Chapter 6
Local Area Networks

6.1
Introduction 55

6.2
The Digital Revolution 55

6.3
The Move To Multiple Computers 56

6.4
Removable Media And Manual Transfer 56

6.5
Early Computers Used Circuit Boards 57

6.6
LANs 58

6.7
The LAN Approach 58

6.8
LAN Hardware 59

6.9
Wireless LAN (WLAN) Connections 60

6.10
Wired And Wireless LAN Technologies 60

6.11
Wireless PAN Technology 61

6.12
Connecting A Device To An Ethernet 61

6.13
Connecting A Device To A Wi-Fi Network 62

6.14
Wi-Fi Security 63

6.15
The Importance Of LAN Technology 63

6.16
Relationship To The Internet 64

PART II
A Brief History Of The Internet
65

69
Chapter 7
Internet: Motivation And Beginnings

7.1
A Proliferation Of LANs 69

7.2
No Technology Solves All Problems 70

7.3
Wide Area Network Technologies 70

7.4
Can We Build A Global WAN? 71

7.5
U.S. Department Of Defense Networking Research 72

7.6
Experimental Research 72

7.7
The Internet Emerges 72

7.8
The ARPANET Backbone 73

7.9
Internet Software 73

7.10
The Name Is TCP/IP 74

7.11
The Surprising Choice Of Open Standards 74

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x
Contents

7.12
Open Communication Systems Win 75

7.13
Placing Internet Technical Documentation Online 75

7.14
The U.S. Military Adopted TCP/IP 76

7.15
Summary 77

81
Chapter 8
The Incredible Growth

8.1
Introduction 81

8.2
Stimulating Adoption 81

8.3
Meanwhile, Back In Computer Science 82

8.4
The Internet Meets Unix 82

8.5
The U.S. Military Makes A Commitment 83

8.6
The Internet Doubled In Size In One Year 83

8.7
Internet For Every Computer Science Department 84

8.8
Graduate Student Volunteers Contribute 85

8.9
Internet Governance: The IAB And IETF 85

8.10
NSF Led Internet Expansion 86
8.11
NSF Target: All Of Science And Engineering 87

8.12
The NSFNET Backbone 87

8.13
On To The ANS Backbone 88

8.14
Commercialization 89

8.15
Exponential Growth 89

8.16
When Will Growth End? 91

PART III
Inside The Internet
93

97
Chapter 9
Packet Switching

9.1
Introduction 97

9.2
Sharing To Reduce Cost 97

9.3
Sharing By Taking Turns 98

9.4
Avoiding Long Delays 98

9.5
Long Messages And Short Packets 99

9.6
Each Packet Contains Extra Information 99

9.7
Devices Have Addresses 100

9.8
Packet Size 100

9.9
To Humans, Packet Transmission Seems Instantaneous 101

9.10
Sharing Occurs On Demand 101

9.11
Relevance To The Internet 102

9.12
Summary 102

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Contents
xi

107
Chapter 10
Internet: A Network Of Networks

10.1
Introduction 107

10.2
Building A Global Network 107

10.3
Two Fundamental Concepts 108

10.4
Using A Specialized Computer To Interconnect Networks 109

10.5
Internet Terminology: Routers And Hosts 110

10.6
Building A Large Virtual Network 111

10.7
The Internet Includes Multiple Types Of Networks 113

10.8
Ownership, ISPs, And Transit Traffic 113

10.9
A Hierarchy Of ISPs 114

10.10 Peering Arrangements At The Center Of The Internet 115
10.11 An Example Trip Through The Internet 116
10.12 The Internet Approach Revolutionized Networking 116
10.13 Summary 117

121
Chapter 11
Internet Access Using Broadband And Wireless

11.1
Introduction 121

11.2
Access Technologies For The Last Mile 121

11.3
Dial-up Internet Access 122

11.4
Narrowband And Broadband Access 122

11.5
Leased Data Circuit Access 123

11.6
Digital Subscriber Line (DSL) Access 123

11.7
Cable Modem Access 124

11.8
Wireless Access Technologies 125

11.9
Cellular Wireless Access (4G and 5G) 126

11.10 Summary 128

131
Chapter 12
Internet Performance

12.1
Introduction 131

12.2
Network Speed 131

12.3
What Does Speed Mean? 132

12.4
Brick Delivery 132

12.5
Transfers Across The Internet 134

12.6
Connecting Heterogeneous Networks 135

12.7
The Effect Of Sharing 137

12.8
Delays In The Internet 139

12.9
Should You Pay for Higher Speed Internet? 140

12.10 Summary 141

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xii
Contents

145
Chapter 13
IP: Software To Create A Virtual Network

13.1
Introduction 145

13.2
Protocol: An Agreement For Communication 145

13.3
Basic Functionality: The Internet Protocol 146

13.4
Packets Arrive Unchanged 146

13.5
Internet Software On Your Device 147

13.6
Internet Packets Are Called Datagrams 147

13.7
Providing The Illusion Of A Giant Network 147

13.8
The Internet’s Internal Structure 148

13.9
Datagrams Travel Inside Network Packets 149

13.10 Internet Addresses 150
13.11 IPv4 And IPv6 150
13.12 Permanent And Temporary IP Addresses 151
13.13 Summary 152

155
Chapter 14
TCP: Software For Reliable Communication

14.1
Introduction 155

14.2
A Packet Switching System Can Be Overrun 155

14.3
Software To Handle Congestion And Datagram Loss 156

14.4
The Magic Of Recovering Lost Datagrams 156

14.5
TCP’s Sophisticated Retransmission Algorithm 157

14.6
Handling Congestion 158

14.7
TCP And IP Work Together 159

14.8
Summary 159

163
Chapter 15
Clients, Servers, And Internet Services

15.1
Introduction 163

15.2
All Services Are Outside The Internet 163

15.3
Software Provides All Services 164

15.4
Services Use Client And Server Apps 165

15.5
A Server Must Always Run 165

15.6
Multiple Clients Can Access A Server Simultaneously 166

15.7
Ambiguous Terminology 167

15.8
Summary 167

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Contents
xiii

171
Chapter 16
Names For Computers

16.1
Introduction 171

16.2
Computer Names 171

16.3
Computer Names Past And Present 172

16.4
A Computer’s Name Must Be Unique 173

16.5
Using Suffixes To Make Each Name Unique 173

16.6
Domain Names With More Than Three Labels 174

16.7
Top-Level Domains Before And After ICANN 174

16.8
Domain Names Outside The US 175

16.9
Translating A Name To An IP Address 176

16.10 Many Domain Name Servers 176
16.11 Looking Up A Domain Name 177
16.12 A Personal Story About A DNS Problem 178
16.13 Summary 178

181
Chapter 17
Sharing An Internet Connection (NAT)

17.1
Introduction 181

17.2
Multiple Devices Sharing A Single IP Address 181

17.3
Wireless Routers And NAT 182

17.4
How A Wireless Router Works 182

17.5
Datagram Modification 183

17.6
Your Device Can Act Like A Wireless Router 184

17.7
You Probably Use NAT Every Day 184

17.8
Why Internet Size Is Difficult To Estimate 185

17.9
Summary 185

189
Chapter 18
Why The Internet Works Well

18.1
Introduction 189

18.2
The Internet Works Extremely Well 189

18.3
Flexibility To Accommodate Arbitrary Networks 190

18.4
Flexibility To Accommodate New Apps Quickly 190

18.5
The Advantage Of Being Open And Vendor Independent 191

18.6
An Extremely Efficient Design 191

18.7
Packet Switching Is A Fundamentally Better Idea 192

18.8
Can The Success Be Replicated? 192

18.9
Summary 194

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xiv
Contents

PART IV
Internet Services
195

199
Chapter 19
Electronic Mail

19.1
Introduction 199

19.2
Functionality And Significance 199

19.3
Mailboxes And Email Addresses 200

19.4
Sending An Email Message Directly 200

19.5
Personal Computers And Email Providers 200

19.6
An Example Email Exchange 201

19.7
Email Delays And Retry Attempts 202

19.8
Providers, Fees, And Access 202

19.9
Mailing Lists 203

19.10 Undisclosed Recipients 203
19.11 Summary 204

207
Chapter 20
The World Wide Web: Browsers And Basics

20.1
Introduction 207

20.2
Browsers And Web Servers 207

20.3
URLs And Their Meaning 208

20.4
Web Pages With Links To Other Pages 208

20.5
Linking Across Web Servers 209

20.6
Hypermedia 210

20.7
A Page With Multimedia Items 211

20.8
Fetching A Page That Contains Multiple Items 212

20.9
Inside A Browser 212

20.10 Plugins And Other Add-on Software Modules 213
20.11 Historical Notes 214
20.12 Summary 214

217
Chapter 21
The World Wide Web: HTML And Web Pages

21.1
Introduction 217

21.2
Accommodating Display Hardware 217

21.3
HTML, A Language Used For Web Documents 218

21.4
Specifying Formatting Guidelines 219

21.5
A Link Embedded In A Web Page 220

21.6
An Image On A Web Page 221

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