Business Data Communications and Networking
Thirteenth Edition
Jerry Fi tzGerald Jerry FitzGerald & Associates
Alan Dennis Indiana University
Alexandra Durcikova University of Oklahoma
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To my son Alec, Alan
To all curious minds who want to know how today’s modern world works.
Alexandra
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ABOUT THE AUTHORS
Alan Dennis is a Fellow of the Association for Information Systems and a professor of information systems in the Kelley School of Business at Indiana University. He holds the John T. Chambers Chair in Internet Systems, which was established to honor John Chambers, president and chief executive officer of Cisco Systems, the worldwide leader of networking technologies for the Internet.
Prior to joining Indiana University, Alan spent nine years as a professor at the University of Georgia, where he won the Richard B. Russell Award for Excellence in Undergraduate Teaching. He has a bachelor’s degree in computer science from Acadia University in Nova Scotia, Canada, and an MBA from Queen’s University in Ontario, Canada. His PhD in management of information systems is from the University of Arizona. Prior to entering the Arizona doctoral program, he spent three years on the faculty of the Queen’s School of Business.
Alan has extensive experience in the development and application of groupware and Internet technologies and co-founded Courseload, an electronic textbook company whose goal is to improve learning and reduce the cost of textbooks. He has won many awards for theoretical and applied research and has published more than 150 business and research articles, including those in Management Science, MIS Quarterly, Information Systems Research, Academy of Management Journal, Organization Behavior and Human Decision Making, Journal of Applied Psychology, Communications of the ACM, and IEEE Transactions of Systems, Man, and Cybernetics. His first book was Getting Started with Microcomputers, published in 1986. Alan is also an author of two systems analysis and design books published by Wiley. He is the cochair of the Internet Tech- nologies Track of the Hawaii International Conference on System Sciences. He has served as a consultant to BellSouth, Boeing, IBM, Hughes Missile Systems, the U.S. Department of Defense, and the Australian Army.
Alexandra Durcikova is an Assistant Professor at the Price College of Business, University of Oklahoma. Alexandra has a PhD in management information systems from the University of Pittsburgh. She has earned an MSc degree in solid state physics from Comenius University, Bratislava, worked as an experimental physics researcher in the area of superconductivity and as an instructor of executive MBA students prior to pursuing her PhD. Alexandra’s research interests include knowledge management and knowledge management systems, the role of organizational climate in the use of knowledge management systems, knowledge management system characteristics, governance mechanisms in the use of knowledge management systems, and human compliance with security policy and characteristics of successful phishing attempts within the area of network security. Her research appears in Information Systems Research, MIS Quarterly, Journal of Management Information Systems, Information Systems Journal, Journal of Organizational and End User Computing, International Journal of Human-Computer Studies, International Journal of Human-Computer Studies, and Communications of the ACM.
Alexandra has been teaching business data communications to both undergraduate and grad- uate students for several years. In addition, she has been teaching classes on information technol- ogy strategy and most recently won the Dean’s Award for Undergraduate Teaching Excellence while teaching at the University of Arizona.
Dr. Jerry FitzGerald wrote the early editions of this book in the 1980s. At the time, he was the principal in Jerry FitzGerald & Associates, a firm he started in 1977.
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PREFACE
The field of data communications has grown faster and become more important than computer processing itself. Though they go hand in hand, the ability to communicate and connect with other computers and mobile devices is what makes or breaks a business today. There are three trends that support this notion. First, the wireless LAN and Bring-Your-Own-Device (BYOD) allow us to stay connected not only with the workplace but also with family and friends. Second, computers and networks are becoming an essential part of not only computers but also devices we use for other purpose, such as home appliances. This Internet of things allows you to set the thermostat in your home from your mobile phone, can help you cook a dinner, or eventually can allow you to drive to work without ever touching the steering wheel. Lastly, we see that a lot of life is moving online. At first this started with games, but education, politics, and activism followed swiftly. Therefore, understanding how networks work; how they should be set up to support scalability, mobility, and security; and how to manage them is of utmost importance to any business. This need will call not only for engineers who deeply understand the technical aspects of networks but also for highly social individuals who embrace technology in creative ways to allow business to achieve a competitive edge through utilizing this technology. So the call is for you who are reading this book—you are at the right place at the right time!
PURPOSE OF THIS BOOK Our goal is to combine the fundamental concepts of data communications and networking with practical applications. Although technologies and applications change rapidly, the fundamental concepts evolve much more slowly; they provide the foundation from which new technologies and applications can be understood, evaluated, and compared.
This book has two intended audiences. First and foremost, it is a university textbook. Each chapter introduces, describes, and then summarizes fundamental concepts and applications. Man- agement Focus boxes highlight key issues and describe how networks are actually being used today. Technical Focus boxes highlight key technical issues and provide additional detail. Mini case studies at the end of each chapter provide the opportunity to apply these technical and man- agement concepts. Hands-on exercises help to reinforce the concepts introduced in the chapter. Moreover, the text is accompanied by a detailed Instructor’s Manual that provides additional back- ground information, teaching tips, and sources of material for student exercises, assignments, and exams. Finally, our Web page contains supplements to our book.
Second, this book is intended for the professional who works in data communications and networking. The book has many detailed descriptions of the technical aspects of communica- tions from a business perspective. Moreover, managerial, technical, and sales personnel can use this book to gain a better understanding of fundamental concepts and trade-offs not presented in technical books or product summaries.
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Preface vii
WHAT’S NEW IN THIS EDITION The thirteenth edition maintains the three main themes of the twelfth edition, namely, (1) how networks work (Chapters 1–5); (2) network technologies (Chapters 6–10); and (3) network secu- rity and management (Chapters 11 and 12). In the new edition, we removed older technologies and replaced them with new ones. Accordingly, new hands-on activities and questions have been added at the end of each chapter that guide students in understanding how to select technolo- gies to build a network that would support an organization’s business needs. In addition to this overarching change, the thirteenth edition has three major changes from the twelfth edition:
First, at the end of each chapter, we provide key implications for cyber security that arise from the topics discussed in the chapter. We draw implications that focus on improving the management of networks and information systems as well as implications for cyber security of an individual and an organization.
The second major change is that in Chapter 5 we have revised the way we explain how TCP/IP works to make it clearer and more streamlined.
Third, we have revised the security chapter (Chapter 11) to consider some of the newer threats and responses.
LAB EXERCISES www.wiley.com/college/fitzgerald
This edition includes an online lab manual with many hands-on exercises that can be used in a networking lab. These exercises include configuring servers and other additional practical topics.
ONLINE SUPPLEMENTS FOR INSTRUCTORS www.wiley.com/college/fitzgerald
Instructor’s supplements comprise an Instructor’s Manual that includes teaching tips, war stories, and answers to end-of-chapter questions; a Test Bank that includes true-false, multiple choice, short answer, and essay test questions for each chapter; and Lecture Slides in PowerPoint for classroom presentations. All are available on the instructor’s book companion site.
E-BOOK Wiley E-Text: Powered by VitalSource offers students continuing access to materials for their course. Your students can access content on a mobile device, online from any Internet-connected computer, or by a computer via download. With dynamic features built into this e-text, students can search across content, highlight, and take notes that they can share with teachers and classmates. Readers will also have access to interactive images and embedded podcasts. Visit www.wiley.com/college/fitzgerald for more information.http://www.wiley.com/college/fitzgeraldhttp://www.wiley.com/college/fitzgerald
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viii Preface
ACKNOWLEDGMENTS Our thanks to the many people who helped in preparing this edition. Specifically, we want to thank the staff at John Wiley & Sons for their support.
Alan Dennis Bloomington, Indiana
www.kelley.indiana.edu/ardennis
Alexandra Durcikova Norman, Oklahoma
http://www.ou.edu/price/mis/people/alexandra_durcikova.html
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CONTENTS
About the Authors v Preface vi
PART ONE INTRODUCTION 1 Chapter 1
Introduction to Data Communications 1 1.1 Introduction 1 1.2 Data Communications Networks 4
1.2.1 Components of a Network 4 1.2.2 Types of Networks 5
1.3 Network Models 7 1.3.1 Open Systems Interconnection
Reference Model 7 1.3.2 Internet Model 9 1.3.3 Message Transmission Using
Layers 10 1.4 Network Standards 13
1.4.1 The Importance of Standards 13 1.4.2 The Standards-Making Process 13 1.4.3 Common Standards 15
1.5 Future Trends 16 1.5.1 Wireless LAN and BYOD 16 1.5.2 The Internet of Things 17 1.5.3 Massively Online 17
1.6 Implications for Cyber Security 18
PART TWO FUNDAMENTAL CONCEPTS 25 Chapter 2
Application Layer 25 2.1 Introduction 25 2.2 Application Architectures 26
2.2.1 Host-Based Architectures 27 2.2.2 Client-Based Architectures 28 2.2.3 Client-Server Architectures 28 2.2.4 Cloud Computing Architectures 31 2.2.5 Peer-to-Peer Architectures 33 2.2.6 Choosing Architectures 34
2.3 World Wide Web 35 2.3.1 How the Web Works 35 2.3.2 Inside an HTTP Request 36 2.3.3 Inside an HTTP Response 37
2.4 Electronic Mail 39 2.4.1 How Email Works 39 2.4.2 Inside an SMTP Packet 42 2.4.3 Attachments in Multipurpose Internet
Mail Extension 43 2.5 Other Applications 43
2.5.1 Telnet 44 2.5.2 Instant Messaging 45 2.5.3 Videoconferencing 45
2.6 Implications for Cyber Security 47
Chapter 3
Physical Layer 57 3.1 Introduction 57 3.2 Circuits 59
3.2.1 Circuit Configuration 59 3.2.2 Data Flow 60 3.2.3 Multiplexing 60
3.3 Communication Media 63 3.3.1 Twisted Pair Cable 63 3.3.2 Coaxial Cable 64 3.3.3 Fiber-Optic Cable 64 3.3.4 Radio 65 3.3.5 Microwave 66 3.3.6 Satellite 66 3.3.7 Media Selection 68
3.4 Digital Transmission of Digital Data 69 3.4.1 Coding 69 3.4.2 Transmission Modes 69
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3.4.3 Digital Transmission 71 3.4.4 How Ethernet Transmits Data 72
3.5 Analog Transmission of Digital Data 73 3.5.1 Modulation 73 3.5.2 Capacity of a Circuit 76 3.5.3 How Modems Transmit Data 76
3.6 Digital Transmission of Analog Data 77 3.6.1 Translating from Analog to Digital 77 3.6.2 How Telephones Transmit Voice
Data 77 3.6.3 How Instant Messenger Transmits
Voice Data 79 3.6.4 Voice over Internet Protocol
(VoIP) 80 3.7 Implications for Cyber Security 80
Chapter 4
Data Link Layer 88 4.1 Introduction 88 4.2 Media Access Control 89
4.2.1 Contention 89 4.2.2 Controlled Access 89 4.2.3 Relative Performance 90
4.3 Error Control 91 4.3.1 Sources of Errors 91 4.3.2 Error Prevention 93 4.3.3 Error Detection 94 4.3.4 Error Correction via
Retransmission 95 4.3.5 Forward Error Correction 95 4.3.6 Error Control in Practice 97
4.4 Data Link Protocols 97 4.4.1 Asynchronous Transmission 97 4.4.2 Synchronous Transmission 98
4.5 Transmission Efficiency 101 4.6 Implications for Cyber Security 103
Chapter 5
NETWORK AND TRANSPORT LAYERS 110 5.1 Introduction 110 5.2 Transport and Network Layer Protocols 112
5.2.1 Transmission Control Protocol (TCP) 112
5.2.2 Internet Protocol (IP) 113
5.3 Transport Layer Functions 114 5.3.1 Linking to the Application Layer 114 5.3.2 Segmenting 115 5.3.3 Session Management 116
5.4 Addressing 119 5.4.1 Assigning Addresses 120 5.4.2 Address Resolution 125
5.5 Routing 127 5.5.1 Types of Routing 128 5.5.2 Routing Protocols 130 5.5.3 Multicasting 132 5.5.4 The Anatomy of a Router 133
5.6 TCP/IP Example 134 5.6.1 Known Addresses 136 5.6.2 Unknown Addresses 137 5.6.3 TCP Connections 138 5.6.4 TCP/IP and Network Layers 139
5.7 Implications for Cyber Security 141
PART THREE NETWORK TECHNOLOGIES 159 Chapter 6
Network Design 159 6.1 Introduction 159
6.1.1 Network Architecture Components 159
6.1.2 The Traditional Network Design Process 161
6.1.3 The Building-Block Network Design Process 162
6.2 Needs Analysis 164 6.2.1 Network Architecture
Component 165 6.2.2 Application Systems 166 6.2.3 Network Users 166 6.2.4 Categorizing Network Needs 166 6.2.5 Deliverables 167
6.3 Technology Design 168 6.3.1 Designing Clients and Servers 168 6.3.2 Designing Circuits 168 6.3.3 Network Design Tools 170 6.3.4 Deliverables 171
6.4 Cost Assessment 171 6.4.1 Request for Proposal 171
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Contents xi
6.4.2 Selling the Proposal to Management 173
6.4.3 Deliverables 173 6.5 Implications for Cyber Security 173
Chapter 7
Wired and Wireless Local Area Networks 177 7.1 Introduction 177 7.2 LAN Components 178
7.2.1 Network Interface Cards 179 7.2.2 Network Circuits 179 7.2.3 Network Hubs, Switches, and Access
Points 180 7.2.4 Network Operating Systems 183
7.3 Wired Ethernet 184 7.3.1 Topology 184 7.3.2 Media Access Control 187 7.3.3 Types of Ethernet 188
7.4 Wireless Ethernet 189 7.4.1 Topology 189 7.4.2 Media Access Control 189 7.4.3 Wireless Ethernet Frame Layout 190 7.4.4 Types of Wireless Ethernet 191 7.4.5 Security 192
7.5 The Best Practice LAN Design 193 7.5.1 Designing User Access with Wired
Ethernet 194 7.5.2 Designing User Access with Wireless
Ethernet 195 7.5.3 Designing the Data Center 197 7.5.4 Designing the e-Commerce Edge 199 7.5.5 Designing the SOHO
Environment 200 7.6 Improving LAN Performance 202
7.6.1 Improving Server Performance 203 7.6.2 Improving Circuit Capacity 204 7.6.3 Reducing Network Demand 204
7.7 Implications for Cyber Security 205
Chapter 8
Backbone Networks 214 8.1 Introduction 214 8.2 Switched Backbones 215 8.3 Routed Backbones 218
8.4 Virtual LANs 221 8.4.1 Benefits of VLANs 221 8.4.2 How VLANs Work 223
8.5 The Best Practice Backbone Design 226 8.6 Improving Backbone Performance 227
8.6.1 Improving Device Performance 227 8.6.2 Improving Circuit Capacity 228 8.6.3 Reducing Network Demand 228
8.7 Implications for Cyber Security 228
Chapter 9
Wide Area Networks 237 9.1 Introduction 237 9.2 Dedicated-Circuit Networks 238
9.2.1 Basic Architecture 238 9.2.2 T-Carrier Services 241 9.2.3 SONET Services 243
9.3 Packet-Switched Networks 243 9.3.1 Basic Architecture 243 9.3.2 Frame Relay Services 245 9.3.3 IP Services 246 9.3.4 Ethernet Services 246
9.4 Virtual Private Networks 247 9.4.1 Basic Architecture 247 9.4.2 VPN Types 248 9.4.3 How VPNs Work 248
9.5 The Best Practice WAN Design 251 9.6 Improving WAN Performance 252
9.6.1 Improving Device Performance 252 9.6.2 Improving Circuit Capacity 253 9.6.3 Reducing Network Demand 253
9.7 Implications for Cyber Security 254
Chapter 10
The Internet 265 10.1 Introduction 265 10.2 How the Internet Works 266
10.2.1 Basic Architecture 266 10.2.2 Connecting to an ISP 268 10.2.3 The Internet Today 269
10.3 Internet Access Technologies 270 10.3.1 Digital Subscriber Line 270 10.3.2 Cable Modem 271 10.3.3 Fiber to the Home 273 10.3.4 WiMax 274
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xii Contents
10.4 The Future of the Internet 274 10.4.1 Internet Governance 274 10.4.2 Building the Future 276
10.5 Implications for Cyber Security 277
PART FOUR NETWORK MANAGEMENT 284 Chapter 11
Network Security 284 11.1 Introduction 284
11.1.1 Why Networks Need Security 286 11.1.2 Types of Security Threats 286 11.1.3 Network Controls 287
11.2 Risk Assessment 288 11.2.1 Develop Risk Measurement
Criteria 289 11.2.2 Inventory IT Assets 290 11.2.3 Identify Threats 291 11.2.4 Document Existing Controls 293 11.2.5 Identify Improvements 296
11.3 Ensuring Business Continuity 296 11.3.1 Virus Protection 296 11.3.2 Denial-of-Service Protection 297 11.3.3 Theft Protection 300 11.3.4 Device Failure Protection 301 11.3.5 Disaster Protection 302
11.4 Intrusion Prevention 305 11.4.1 Security Policy 306 11.4.2 Perimeter Security and Firewalls 306 11.4.3 Server and Client Protection 312 11.4.4 Encryption 315 11.4.5 User Authentication 321 11.4.6 Preventing Social Engineering 324
11.4.7 Intrusion Prevention Systems 325 11.4.8 Intrusion Recovery 327
11.5 Best Practice Recommendations 328 11.6 Implications for Your Cyber Security 330
Chapter 12
Network Management 340 12.1 Introduction 340 12.2 Designing for Network Performance 341
12.2.1 Managed Networks 341 12.2.2 Managing Network Traffic 345 12.2.3 Reducing Network Traffic 346
12.3 Configuration Management 349 12.3.1 Configuring the Network and Client
Computers 349 12.3.2 Documenting the Configuration
350 12.4 Performance and Fault Management 351
12.4.1 Network Monitoring 351 12.4.2 Failure Control Function 353 12.4.3 Performance and Failure
Statistics 355 12.4.4 Improving Performance 358
12.5 End User Support 358 12.5.1 Resolving Problems 358 12.5.2 Providing End User Training 360
12.6 Cost Management 360 12.6.1 Sources of Costs 360 12.6.2 Reducing Costs 363
12.7 Implications for Cyber Security 364
Appendices (Online) Glossary (Online) Index 373
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PART ONE INTRODUCTION
C H A P T E R 1
INTRODUCTION TO DATA COMMUNICATIONS
This chapter introduces the basic concepts of data communications. It describes why it is impor- tant to study data communications and introduces you to the three fundamental questions that this book answers. Next, it discusses the basic types and components of a data communications network. Also, it examines the importance of a network model based on layers. Finally, it describes the three key trends in the future of networking.
OBJECTIVES ◾ Be aware of the three fundamental questions this book answers ◾ Be aware of the applications of data communications networks ◾ Be familiar with the major components of and types of networks ◾ Understand the role of network layers ◾ Be familiar with the role of network standards ◾ Be aware of cyber security issues ◾ Be aware of three key trends in communications and networking
OUTLINE 1.1 Introduction 1.2 Data Communications Networks
1.2.1 Components of a Network 1.2.2 Types of Networks
1.3 Network Models 1.3.1 Open Systems Interconnection
Reference Model 1.3.2 Internet Model 1.3.3 Message Transmission Using Layers
1.4 Network Standards
1.4.1 The Importance of Standards 1.4.2 The Standards-Making Process 1.4.3 Common Standards
1.5 Future Trends 1.5.1 Wireless LAN and BYOD 1.5.2 The Internet of Things 1.5.3 Massively Online
1.6 Implications for Cyber Security Summary
1.1 INTRODUCTION What Internet connection should you use? Cable modem or DSL (formally called Digital Sub- scriber Line)? Cable modems are supposedly faster than DSL, providing data speeds of 50 Mbps to DSL’s 1.5–25 Mbps (million bits per second). One cable company used a tortoise to represent DSL in advertisements. So which is faster? We’ll give you a hint. Which won the race in the fable, the tortoise or the hare? By the time you finish this book, you’ll understand which is faster and why, as well as why choosing the right company as your Internet service provider (ISP) is probably more important than choosing the right technology.
Over the past decade or so, it has become clear that the world has changed forever. We con- tinue to forge our way through the Information Age—the second Industrial Revolution, according
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2 Chapter 1 Introduction to Data Communications
to John Chambers, CEO (chief executive officer) of Cisco Systems, Inc., one of the world’s leading networking technology companies. The first Industrial Revolution revolutionized the way people worked by introducing machines and new organizational forms. New companies and industries emerged, and old ones died off.
The second Industrial Revolution is revolutionizing the way people work through network- ing and data communications. The value of a high-speed data communications network is that it brings people together in a way never before possible. In the 1800s, it took several weeks for a message to reach North America by ship from England. By the 1900s, it could be transmitted within an hour. Today, it can be transmitted in seconds. Collapsing the information lag to Internet speeds means that people can communicate and access information anywhere in the world regard- less of their physical location. In fact, today’s problem is that we cannot handle the quantities of information we receive.
Data communications and networking is a truly global area of study, both because the technology enables global communication and because new technologies and applications often emerge from a variety of countries and spread rapidly around the world. The World Wide Web, for example, was born in a Swiss research lab, was nurtured through its first years primarily by European universities, and exploded into mainstream popular culture because of a development at an American research lab.
One of the problems in studying a global phenomenon lies in explaining the different polit- ical and regulatory issues that have evolved and currently exist in different parts of the world. Rather than attempt to explain the different paths taken by different countries, we have chosen simplicity instead. Historically, the majority of readers of previous editions of this book have come from North America. Therefore, although we retain a global focus on technology and its business implications, we focus mostly on North America.
This book answers three fundamental questions. First, how does the Internet work? When you access a website using your computer, laptop,
iPad, or smartphone, what happens so that the page opens in your Web browser? This is the focus in Chapters 1–5. The short answer is that the software on your computer (or any device) creates a message composed in different software languages (HTTP, TCP/IP, and Ethernet are common) that requests the page you clicked. This message is then broken up into a series of smaller parts that we call packets. Each packet is transmitted to the nearest router, which is a special-purpose computer whose primary job is to find the best route for these packets to their final destination. The packets move from router to router over the Internet until they reach the Web server, which puts the packets back together into the same message that your computer created. The Web server reads your request and then sends the page back to you in the same way—by composing a message using HTTP, TCP/IP, and Ethernet and then sending it as a series of smaller packets back through the Internet that the software on your computer puts together into the page you requested. You might have heard a news story that the U.S. or Chinese government can read your email or see what websites you’re visiting. A more shocking truth is that the person sitting next you at a coffee shop might be doing exactly the same thing—reading all the packets that come from or go to your laptop. How is this possible, you ask? After finishing Chapter 5, you will know exactly how this is possible.
Second, how do I design a network? This is the focus of Chapters 6–10. We often think about networks in four layers. The first layer is the Local Area Network, or the LAN (either wired or wireless), which enables users like you and me to access the network. The second is the backbone network that connects the different LANs within a building. The third is the core network that connects different buildings on a company’s campus. The final layer is connections we have to the other campuses within the organization and to the Internet. Each of these layers has slightly different concerns, so the way we design networks for them and the technologies we use are
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Introduction 3
slightly different. Although this describes the standard for building corporate networks, you will have a much better understanding of how your wireless router at home works. Perhaps more importantly, you’ll learn why buying the newest and fastest wireless router for your house or apart- ment is probably not a good way to spend your money.
Finally, how do I manage my network to make sure it is secure, provides good performance, and doesn’t cost too much? This is the focus of Chapters 11 and 12. Would it surprise you to learn that most companies spend between $1,500 and $3,500 per computer per year on network man- agement and security? Yup, we spend way more on network management and security each year than we spend to buy the computer in the first place. And that’s for well-run networks; poorly run networks cost a lot more. Many people think network security …
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