hub.totalsem

Mike Meyers’

CompTIA Network+® Guide to Managing and

Troubleshooting Networks

Third Edition

(Exam N10-005)

This page intentionally left blank

Mike Meyers’

CompTIA Network+® Guide to Managing and

Troubleshooting Networks

Third Edition

(Exam N10-005)

Mike Meyers

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BaseTech

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About the Author■■ Michael Meyers is the industry’s leading authority on CompTIA Network+ certifica- tion. He is the president and founder of Total Seminars, LLC, a major provider of PC and network repair seminars for thousands of organizations throughout the world, and a member of CompTIA.

Mike has written numerous popular textbooks, including the best-selling Mike Meyers’ CompTIA A+® Guide to Managing & Troubleshooting PCs, Mike Meyers’ CompTIA A+® Guide to Essentials, and Mike Meyers’ CompTIA A+® Guide to Operating Systems.

About the Contributor Scott Jernigan wields a mighty red pen as Editor in Chief for Total Seminars. With a Master of Arts degree in Medieval History, Scott feels as much at home in the musty archives of London as he does in the warm CRT glow of Total Seminars’ Houston head- quarters. After fleeing a purely academic life, he dove headfirst into IT, working as an instructor, editor, and writer.

Scott has written, edited, and contributed to dozens of books on computer liter- acy, hardware, operating systems, networking, and certification, including Computer Literacy—Your Ticket to IC3 Certification, and co-authoring with Mike Meyers the All-in- One CompTIA Strata® IT Fundamentals Exam Guide.

Scott has taught computer classes all over the United States, including stints at the United Nations in New York and the FBI Academy in Quantico. Practicing what he preaches, Scott is a CompTIA A+ and CompTIA Network+ certified technician, a Microsoft Certified Professional, a Microsoft Office User Specialist, and Certiport Inter- net and Computing Core Certified.

About the Technical Editor Jonathan S. Weissman earned his master’s degree in Computer and Information Science from Brooklyn College (CUNY), and holds nineteen industry certifications, including Cisco CCNA, CompTIA Security+, CompTIA i-Net+, CompTIA Network+, CompTIA A+, CompTIA Linux+, Novell CNE, Novell CNA, Microsoft Office Master, Microsoft MCAS Word, Microsoft MCAS PowerPoint, Microsoft MCAS Excel, Microsoft MCAS Access, Microsoft MCAS Outlook, and Microsoft MCAS Vista.

Jonathan is a tenured Assistant Professor of Computing Sciences at Finger Lakes Community College, in Canandaigua, NY, and also teaches graduate and under- graduate computer science courses at nearby Rochester Institute of Technology. In addi- tion, Jonathan does computer, network, and security consulting for area businesses and individuals.

Between FLCC and RIT, Jonathan has taught nearly two dozen different computer science courses, including networking, security, administration, forensics, program- ming, operating systems, hardware, and software.

Students evaluating his teaching emphasize that he simplifies their understanding of difficult topics, while at the same time makes the class interesting and entertaining.

Jonathan completely designed and configured FLCC’s newest Networking & Secu- rity Lab. Serving as IT Program Coordinator, he rewrote FLCC’s Information Technol- ogy course requirements for the degree, keeping it current with the changes in industry over the years.

This textbook is just one of the many that Jonathan has edited for thoroughness and accuracy.

BaseTech

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vii

Acknowledgments■■ I’d like to acknowledge the many people who contributed their talents to make this book possible:

To Tim Green, my acquisitions editor at McGraw-Hill: Didn’t think I’d get the book out this quickly, did you? Thanks for your superb support and encouragement, as always.

To my in-house Editor-in-Chief, Scott Jernigan: Didn’t think we’d get the book out that fast, did you? How many 85s do you have now? Pelape still smokes them all in DPS.

To Jonathan Weissman, technical editor: Holy crap, you kicked my butt. Thanks for making my book dramatically better than it has ever been.

To LeeAnn Pickrell, copy editor: u made me write good, thx. To Michael Smyer, Total Seminars’ resident tech guru and photogra-

pher: Glad to see you staying focused. And your photos rocked as always! To Ford Pierson, graphics maven and editor: Superb conceptual art?

Check! Great editing? Check! Beating the boss in Unreal Tournament over and over again? Check, unfortunately.

To Aaron Verber, editor extraordinaire: Your quiet toils in the dark cor- ner of the office have once again paid outstanding dividends!

To Dudley Lehmer, my partner at Total Seminars: As always, thanks for keeping the ship afloat while I got to play on this book!

To Stephanie Evans, acquisitions coordinator at McGraw-Hill: You are my favorite South African ambassador since the Springboks. Thanks for keeping track of everything and (gently) smacking Scott when he forgot things.

To Molly Sharp and Jody McKenzie, project editors: It was a joy to work with you, Molly, and again with you, Jody. I couldn’t have asked for a better team! (Didn’t think I could resist making the pun, did you?)

To Andrea Fox, proofreader: You did a super job, thank you To Tom and Molly Sharp, compositors: The layout was excellent,

thanks!

To Staci Lynne ■■ Davis, vegan chef and

punk rocker: Thanks for showing me your world

and, in the process, expanding mine.

BaseTech

Key Terms, identified in red, point out important vocabulary and definitions that you need to know.

Tech Tip sidebars provide inside information from experienced IT professionals.

Cross Check questions develop reasoning skills: ask, compare, contrast, and explain.

Engaging and Motivational— Using a conversational style and proven instructional approach, the author explains technical concepts in a clear, interesting way using real-world examples.

Makes Learning Fun!— Rich, colorful text and enhanced illustrations bring technical subjects to life.

10BaseT also introduced the networking world to the RJ-45 connector (Figure 4.9). Each pin on the RJ-45 connects to a single wire inside the cable; this enables de- vices to put voltage on the indi- vidual wires within the cable. The pins on the RJ-45 are numbered from 1 to 8, as shown in Figure 4.10.

The 10BaseT standard designates some of these numbered wires for specific purposes. As mentioned earlier, although the cable has four pairs, 10BaseT uses only two of the pairs. 10BaseT devices use pins 1 and 2 to send data, and pins 3 and 6 to receive data. Even though one pair of wires sends data and another receives data, a 10BaseT device cannot send and receive simul- taneously. The rules of CSMA/CD still apply: only one device can use the segment contained in the hub without causing a collision. Later versions of Ethernet will change this rule.

An RJ-45 connector is usually called a crimp, and the act (some folks call it an art) of installing a crimp onto the end of a piece of UTP cable is called crimping. The tool used to secure a crimp onto the end of a cable is a crimper. Each wire inside a UTP cable must connect to the proper pin inside the crimp. Manufacturers color-code each wire within a piece of four-pair UTP to assist in properly matching the ends. Each pair of wires consists of a solid- colored wire and a striped wire: blue/blue-white, orange/orange-white, brown/brown-white, and green/green-white (Figure 4.11).

The Telecommunications Industry Association/Electronics Industries Alliance (TIA/EIA) defines the industry standard for correct crimping of four-pair UTP for 10BaseT networks. Two standards currently exist: TIA/ EIA 568A and TIA/EIA 568B. Figure 4.12 shows the TIA/EIA 568A and TIA/ EIA 568B color-code standards. Note that the wire pairs used by 10BaseT (1 and 2; 3 and 6) come from the same color pairs (green/green-white and orange/orange-white). Following an established color-code scheme, such as TIA/EIA 568A, ensures that the wires match up correctly at each end of the cable.

66 Mike Meyers’ CompTIA Network+ Guide to Managing and Troubleshooting Networks

Cross Check Check Your CATs!

You’ve already seen CAT levels in Chapter 3, “Cabling and Topology,” so check your memory and review the different speeds of the various CAT levels. Could 10BaseT use CAT 2? Could it use CAT 6? What types of devices can use CAT 1?

• Figure 4.9 Two views of an RJ-45 connector

• Figure 4.10 The pins on an RJ-45 connector are numbered 1 through 8.

• Figure 4.11 Color-coded pairs

The real name for RJ-45 is “8 Position 8 Contact (8P8C) modular plug.” The name RJ-45 is so dominant, however, that nobody but the nerdiest of nerds calls it by its real name. Stick to RJ-45.

AbouT ThIs book

Proven Learning Method Keeps You on Track Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks is structured to give you comprehensive knowledge of computer skills and technologies. The textbook’s active learning methodology guides you beyond mere recall and—through thought-provoking activities, labs, and sidebars—helps you develop critical-thinking, diagnostic, and communication skills.

Information technology (IT) offers many career paths, leading to occupations in such fields as PC repair, network administration, telecommunications, Web development, graphic design, and desktop support. To become competent in any IT field, however, you need

certain basic computer skills. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks builds a foundation for success in the IT field by introducing you to fundamental technology concepts and giving you essential computer skills.

Important Technology skills ■

10BaseT also introduced the networking world to the RJ-45 connector (Figure 4.9). Each pin on the RJ-45 connects to a single wire inside the cable; this enables de- vices to put voltage on the indi- vidual wires within the cable. The pins on the RJ-45 are numbered from 1 to 8, as shown in Figure 4.10.

The 10BaseT standard designates some of these numbered wires for specific purposes. As mentioned earlier, although the cable has four pairs, 10BaseT uses only two of the pairs. 10BaseT devices use pins 1 and 2 to send data, and pins 3 and 6 to receive data. Even though one pair of wires sends data and another receives data, a 10BaseT device cannot send and receive simul- taneously. The rules of CSMA/CD still apply: only one device can use the segment contained in the hub without causing a collision. Later versions of Ethernet will change this rule.

An RJ-45 connector is usually called a crimp, and the act (some folks call it an art) of installing a crimp onto the end of a piece of UTP cable is called crimping. The tool used to secure a crimp onto the end of a cable is a crimper. Each wire inside a UTP cable must connect to the proper pin inside the crimp. Manufacturers color-code each wire within a piece of four-pair UTP to assist in properly matching the ends. Each pair of wires consists of a solid- colored wire and a striped wire: blue/blue-white, orange/orange-white, brown/brown-white, and green/green-white (Figure 4.11).

The Telecommunications Industry Association/Electronics Industries Alliance (TIA/EIA) defines the industry standard for correct crimping of four-pair UTP for 10BaseT networks. Two standards currently exist: TIA/ EIA 568A and TIA/EIA 568B. Figure 4.12 shows the TIA/EIA 568A and TIA/ EIA 568B color-code standards. Note that the wire pairs used by 10BaseT (1 and 2; 3 and 6) come from the same color pairs (green/green-white and orange/orange-white). Following an established color-code scheme, such as TIA/EIA 568A, ensures that the wires match up correctly at each end of the cable.

66 Mike Meyers’ CompTIA Network+ Guide to Managing and Troubleshooting Networks

Cross Check Check Your CATs!

You’ve already seen CAT levels in Chapter 3, “Cabling and Topology,” so check your memory and review the different speeds of the various CAT levels. Could 10BaseT use CAT 2? Could it use CAT 6? What types of devices can use CAT 1?

• Figure 4.9 Two views of an RJ-45 connector

• Figure 4.10 The pins on an RJ-45 connector are numbered 1 through 8.

• Figure 4.11 Color-coded pairs

The real name for RJ-45 is “8 Position 8 Contact (8P8C) modular plug.” The name RJ-45 is so dominant, however, that nobody but the nerdiest of nerds calls it by its real name. Stick to RJ-45.

10BaseT also introduced the networking world to the RJ-45 connector (Figure 4.9). Each pin on the RJ-45 connects to a single wire inside the cable; this enables de- vices to put voltage on the indi- vidual wires within the cable. The pins on the RJ-45 are numbered from 1 to 8, as shown in Figure 4.10.

The 10BaseT standard designates some of these numbered wires for specific purposes. As mentioned earlier, although the cable has four pairs, 10BaseT uses only two of the pairs. 10BaseT devices use pins 1 and 2 to send data, and pins 3 and 6 to receive data. Even though one pair of wires sends data and another receives data, a 10BaseT device cannot send and receive simul- taneously. The rules of CSMA/CD still apply: only one device can use the segment contained in the hub without causing a collision. Later versions of Ethernet will change this rule.

An RJ-45 connector is usually called a crimp, and the act (some folks call it an art) of installing a crimp onto the end of a piece of UTP cable is called crimping. The tool used to secure a crimp onto the end of a cable is a crimper. Each wire inside a UTP cable must connect to the proper pin inside the crimp. Manufacturers color-code each wire within a piece of four-pair UTP to assist in properly matching the ends. Each pair of wires consists of a solid- colored wire and a striped wire: blue/blue-white, orange/orange-white, brown/brown-white, and green/green-white (Figure 4.11).

The Telecommunications Industry Association/Electronics Industries Alliance (TIA/EIA) defines the industry standard for correct crimping of four-pair UTP for 10BaseT networks. Two standards currently exist: TIA/ EIA 568A and TIA/EIA 568B. Figure 4.12 shows the TIA/EIA 568A and TIA/ EIA 568B color-code standards. Note that the wire pairs used by 10BaseT (1 and 2; 3 and 6) come from the same color pairs (green/green-white and orange/orange-white). Following an established color-code scheme, such as TIA/EIA 568A, ensures that the wires match up correctly at each end of the cable.

66 Mike Meyers’ CompTIA Network+ Guide to Managing and Troubleshooting Networks

Cross Check Check Your CATs!

You’ve already seen CAT levels in Chapter 3, “Cabling and Topology,” so check your memory and review the different speeds of the various CAT levels. Could 10BaseT use CAT 2? Could it use CAT 6? What types of devices can use CAT 1?

• Figure 4.9 Two views of an RJ-45 connector

• Figure 4.10 The pins on an RJ-45 connector are numbered 1 through 8.

• Figure 4.11 Color-coded pairs

The real name for RJ-45 is “8 Position 8 Contact (8P8C) modular plug.” The name RJ-45 is so dominant, however, that nobody but the nerdiest of nerds calls it by its real name. Stick to RJ-45.

/ Mike Meyers’ CompTIA Network+ Guide to Managing and Troubleshooting Networks, Third Edition / Meyers / 911-1 / fm blind folio ix

consider that type of NIC. The spe- cific process by which a NIC uses electricity to send and receive data is exceedingly complicated, but luck- ily for you, not necessary to under- stand. Instead, just think of a charge on the wire as a one, and no charge as a zero. A chunk of data moving in pulses across a wire might look something like Figure 2.13.

If you put an oscilloscope on the wire to measure voltage, you’d see something like Figure 2.14. An oscilloscope is a powerful micro- scope that enables you to see elec- trical pulses.

Now, remembering that the pulses represent bi- nary data, visualize instead a string of ones and zeroes moving across the wire (Figure 2.15).

Once you understand how data moves along the wire, the next question becomes this: how does the net- work get the right data to the right system? All networks transmit data by breaking whatever is moving across the physical layer (files, print jobs, Web pages, and so forth) into discrete chunks called frames. A frame is basically a container for a chunk of data moving across a network. The NIC creates and sends, as well as receives and reads, these frames.

I like to visualize an imaginary table inside every NIC that acts as a frame creation and reading station. I see frames as those pneumatic canis- ters you see when you go to a drive-in teller at a bank. A little guy inside the network card—named Nick, naturally!—builds these pneumatic canisters (the frames) on the table, and then shoots them out on the wire to the hub (Figure 2.16).

Chapter 2: Building a Network with the OSI Model 15

Try This! What’s Your MAC Address?

You can readily determine your MAC address on a Windows computer from the command line. This works in all modern versions of Windows.

1. In Windows 2000/XP, click Start | Run. Enter the command CMD and press the ENTER key to get to a command prompt.

2. In Windows Vista, click Start, enter CMD in the Start Search text box, and press the ENTER key to get to a command prompt.

3. At the command prompt, type the command IPCONFIG /ALL and press the ENTER key.

• Figure 2.13 Data moving along a wire

• Figure 2.14 Oscilloscope of data

• Figure 2.15 Data as ones and zeroes

• Figure 2.16 Inside the NIC

A number of different frame types are used in different net- works. All NICs on the same net- work must use the same frame type or they will not be able to communicate with other NICs.

Each chapter includes Learning Objectives ■ that set measurable goals for chapter-by-chapter progress

Illustrations ■ that give you a clear picture of the technologies

Tutorials ■ that teach you to perform essential tasks and procedures hands-on

Try This!, Cross Check ■ , and Tech Tip sidebars that encourage you to practice and apply concepts in real-world settings

Notes, Tips ■ , and Warnings that guide you through difficult areas

Chapter Summaries ■ and Key Terms Lists that provide you with an easy way to review important concepts and vocabulary

Challenging End-of-Chapter Tests ■ that include vocabulary-building exercises, multiple-choice questions, essay questions, and on-the-job lab projects

This pedagogically rich book is designed to make learning easy and enjoyable and to help you develop the skills and critical-thinking abilities that will enable you to adapt to different job situations and troubleshoot problems.

Mike Meyers’ proven ability to explain concepts in a clear, direct, even humorous way makes this book interesting, motivational, and fun.

Effective Learning Tools ■

Proven Learning Method Keeps You on Track Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks is structured to give you comprehensive knowledge of computer skills and technologies. The textbook’s active learning methodology guides you beyond mere recall and—through thought-provoking activities, labs, and sidebars—helps you develop critical-thinking, diagnostic, and communication skills.

Try This! exercises apply core skills in a new setting.

Chapter Review sections provide concept summaries, key terms lists, and lots of questions and projects.

Key Terms Lists presents the important terms identified in the chapter.

Offers Practical Experience— Tutorials and lab assignments develop essential hands-on skills and put concepts in real-world contexts.

Robust Learning Tools— Summaries, key terms lists, quizzes, essay questions, and lab projects help you practice skills and measure progress.

Notes,Tips, and Warnings create a road map for success.

consider that type of NIC. The spe- cific process by which a NIC uses electricity to send and receive data is exceedingly complicated, but luck- ily for you, not necessary to under- stand. Instead, just think of a charge on the wire as a one, and no charge as a zero. A chunk of data moving in pulses across a wire might look something like Figure 2.13.

If you put an oscilloscope on the wire to measure voltage, you’d see something like Figure 2.14. An oscilloscope is a powerful micro- scope that enables you to see elec- trical pulses.

Now, remembering that the pulses represent bi- nary data, visualize instead a string of ones and zeroes moving across the wire (Figure 2.15).

Once you understand how data moves along the wire, the next question becomes this: how does the net- work get the right data to the right system? All networks transmit data by breaking whatever is moving across the physical layer (files, print jobs, Web pages, and so forth) into discrete chunks called frames. A frame is basically a container for a chunk of data moving across a network. The NIC creates and sends, as well as receives and reads, these frames.

I like to visualize an imaginary table inside every NIC that acts as a frame creation and reading station. I see frames as those pneumatic canis- ters you see when you go to a drive-in teller at a bank. A little guy inside the network card—named Nick, naturally!—builds these pneumatic canisters (the frames) on the table, and then shoots them out on the wire to the hub (Figure 2.16).

Chapter 2: Building a Network with the OSI Model 15

Try This! What’s Your MAC Address?

You can readily determine your MAC address on a Windows computer from the command line. This works in all modern versions of Windows.

1. In Windows 2000/XP, click Start | Run. Enter the command CMD and press the ENTER key to get to a command prompt.

2. In Windows Vista, click Start, enter CMD in the Start Search text box, and press the ENTER key to get to a command prompt.

3. At the command prompt, type the command IPCONFIG /ALL and press the ENTER key.

• Figure 2.13 Data moving along a wire

• Figure 2.14 Oscilloscope of data

• Figure 2.15 Data as ones and zeroes

• Figure 2.16 Inside the NIC

A number of different frame types are used in different net- works. All NICs on the same net- work must use the same frame type or they will not be able to communicate with other NICs.

consider that type of NIC. The spe- cific process by which a NIC uses electricity to send and receive data is exceedingly complicated, but luck- ily for you, not necessary to under- stand. Instead, just think of a charge on the wire as a one, and no charge as a zero. A chunk of data moving in pulses across a wire might look something like Figure 2.13.

If you put an oscilloscope on the wire to measure voltage, you’d see something like Figure 2.14. An oscilloscope is a powerful micro- scope that enables you to see elec- trical pulses.

Now, remembering that the pulses represent bi- nary data, visualize instead a string of ones and zeroes moving across the wire (Figure 2.15).

Once you understand how data moves along the wire, the next question becomes this: how does the net- work get the right data to the right system? All networks transmit data by breaking whatever is moving across the physical layer (files, print jobs, Web pages, and so forth) into discrete chunks called frames. A frame is basically a container for a chunk of data moving across a network. The NIC creates and sends, as well as receives and reads, these frames.

I like to visualize an imaginary table inside every NIC that acts as a frame creation and reading station. I see frames as those pneumatic canis- ters you see when you go to a drive-in teller at a bank. A little guy inside the network card—named Nick, naturally!—builds these pneumatic canisters (the frames) on the table, and then shoots them out on the wire to the hub (Figure 2.16).

Chapter 2: Building a Network with the OSI Model 15

Try This! What’s Your MAC Address?

You can readily determine your MAC address on a Windows computer from the command line. This works in all modern versions of Windows.

1. In Windows 2000/XP, click Start | Run. Enter the command CMD and press the ENTER key to get to a command prompt.

2. In Windows Vista, click Start, enter CMD in the Start Search text box, and press the ENTER key to get to a command prompt.

3. At the command prompt, type the command IPCONFIG /ALL and press the ENTER key.

• Figure 2.13 Data moving along a wire

• Figure 2.14 Oscilloscope of data

• Figure 2.15 Data as ones and zeroes

• Figure 2.16 Inside the NIC

A number of different frame types are used in different net- works. All NICs on the same net- work must use the same frame type or they will not be able to communicate with other NICs.

BaseTech

x

/ Mike Meyers’ CompTIA Network+ Guide to Managing and Troubleshooting Networks, Third Edition / Meyers / 911-1 / Front Matter

Contents at a Glance

CoNTENTs AT A GLANCE

Chapter 1 ■ CompTIA Network+ in a Nutshell 1

Chapter 2 ■ Network Models 8

Chapter 3 ■ Cabling and Topology 44

Chapter 4 ■ Ethernet Basics 66

Chapter 5 ■ Modern Ethernet 90

Chapter 6 ■ Installing a Physical Network 106

Chapter 7 ■ TCP/IP Basics 144

Chapter 8 ■ The Wonderful World of Routing 182

Chapter 9 ■ TCP/IP Applications 224

Chapter 10 ■ Network Naming 258

Chapter 11 ■ Securing TCP/IP 294

Chapter 12 ■ Advanced Networking Devices 330

Chapter 13 ■ IPv6 356

Chapter 14 ■ Remote Connectivity 380

Chapter 15 ■ Wireless Networking 424

BaseTech

xi Contents at a Glance

Chapter 16 ■ Protecting Your Network 458

Chapter 17 ■ Virtualization 484

Chapter 18 ■ Network Management 504

Chapter 19 ■ Building a SOHO Network 534

Chapter 20 ■ Network Troubleshooting 554

Appendix A ■ Objectives Map: CompTIA Network+ 580

Appendix b ■ About the Download 592

■ Glossary 596

■ Index 632

xii

/ Mike Meyers’ CompTIA Network+ Guide to Managing and Troubleshooting Networks, Third Edition / Meyers / 911-1 / Front Matter

Contents

About the Author . . . . . . . . . . . . . . . . . . v Acknowledgments . . . . . . . . . . . . . . . . . .vii Preface. . . . . . . . . . . . . . . . . . . . . . . . xvii CompTIA Approved Quality Curriculum. . . . xix Instructor and Student Website. . . . . . . . . . xxv

Chapter 1 ■■CompTIA Network+ in a Nutshell 1 Who Needs CompTIA Network+?

I Just Want to Learn about Networks! . . . . . 1 What Is CompTIA Network+ Certification? . . . 1

What Is CompTIA? . . . . . . . . . . . . . . . 2 The Current CompTIA Network+

Certification Exam Release. . . . . . . . . . 2 How Do I Become CompTIA

Network+ Certified? . . . . . . . . . . . . . 2 What Is the Exam Like? . . . . . . . . . . . . . . . 3

How Do I Take the Test?. . . . . . . . . . . . . 4 How Much Does the Test Cost? . . . . . . . . . 4

How to Pass the CompTIA Network+ Exam . . . 5 Obligate Yourself . . . . . . . . . . . . . . . . 5 Set Aside the Right Amount of Study Time . . 5 Study for the Test . . . . . . . . . . . . . . . . 6

Chapter 2 ■■Network Models 8 Historical/Conceptual . . . . . . . . . . . . . . . 10 Working with Models . . . . . . . . . . . . . . . . 10

Biography of a Model . . . . . . . . . . . . . . 10 Network Models . . . . . . . . . . . . . . . . . 11

The OSI Seven-Layer Model in Action. . . . . . . 11 Welcome to MHTechEd!. . . . . . . . . . . . . 12

Test Specific. . . . . . . . . . . . . . . . . . . . . . 13 Let’s Get Physical—Network Hardware

and Layers 1–2 . . . . . . . . . . . . . . . . . . 13 The NIC . . . . . . . . . . . . . . . . . . . . . 15 The Two Aspects of NICs . . . . . . . . . . . . 21

Beyond the Single Wire—Network Software and Layers 3–7 . . . . . . . . . . . . . . . . . . 22

IP—Playing on Layer 3, the Network Layer . . . 24 Packets Within Frames . . . . . . . . . . . . . 25 Assembly and Disassembly—Layer 4,

the Transport Layer . . . . . . . . . . . . . 27

Talking on a Network—Layer 5, the Session Layer . . . . . . . . . . . . . . . 28

Standardized Formats, or Why Layer 6, Presentation, Has No Friends . . . . . . . . 30

Network Applications—Layer 7, the Application Layer . . . . . . . . . . . . . . 31

The TCP/IP Model. . . . . . . . . . . . . . . . . . 32 The Link Layer . . . . . . . . . . . . . . . . . 33 The Internet Layer. . . . . . . . . . . . . . . . 34 The Transport Layer . . . . . . . . . . . . . . . 34 The Application Layer . . . . . . . . . . . . . . 36 Frames, Packets, and Segments, Oh My! . . . . 37 The Tech’s Troubleshooting Tool . . . . . . . . . 38

Chapter 2 Review . . . . . . . . . . . . . . . . . . 39

Chapter 3 ■■Cabling and Topology 44 Test Specific. . . . . . . . . . . . . . . . . . . . . . 45 Topology . . . . . . . . . . . . . . . . . . . . . . . 45

Bus and Ring . . . . . . . . . . . . . . . . . . 45 Star . . . . . . . . . . . . . . . . . . . . . . . 46 Hybrids . . . . . . . . . . . . . . . . . . . . . 47 Mesh and Point-to-Multipoint . . . . . . . . . 47 Point-to-Point . . . . . . . . . . . . . . . . . . 50 Parameters of a Topology . . . . . . . . . . . . 50

Cabling . . . . . . . . . . . . . . . . . . . . . . . . 50 Coaxial Cable . . . . . . . . . . . . . . . . . . 50 Twisted Pair . . . . . . . . . . . . . . . . . . . 53 Fiber-Optic . . . . . . . . . . . . . . . . . . . 55 Other Cables . . . . . . . . . . . . . . . . . . . 56 Fire Ratings . . . . . . . . . . . . . . . . . . . 58

Networking Industry Standards—IEEE . . . . . . 58 Chapter 3 Review . . . . . . . . . . . . . . . . . . 60

Chapter 4 ■■Ethernet Basics 66 Historical/Conceptual . . . . . . . . . . . . . . . 67 Ethernet . . . . . . . . . . . . . . . . . . . . . . . . 67

Topology . . . . . . . . . . . . . . . . . . . . . 67 Test Specific. . . . . . . . . . . . . . . . . . . . . . 68 Organizing the Data: Ethernet Frames . . . . . . 68

CSMA/CD . . . . . . . . . . . . . . . . . . . 71

CoNTENTs

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Early Ethernet Networks . . . . . . . . . . . . . . 73 10BaseT . . . . . . . . . . . . . . . . . . . . . 73 10BaseFL . . . . . . . . . . . . . . . . . . . . 76

Extending and Enhancing Ethernet Networks . . 78 Connecting Ethernet Segments . . . . . . . . . 78 Switched Ethernet . . . . . . . . . . . . . . . . 80 Troubleshooting Hubs and Switches . . . . . . 84

Chapter 4 Review . . . . . . . . . . . . . . . . . . 85

Chapter 5 ■■Modern Ethernet 90 Test Specific. . . . . . . . . . . . . . . . . . . . . . 91 100-Megabit Ethernet . . . . . . . . . . . . . . . . 91

100BaseT . . . . . . . . . . . . . . . . . . . . 91 100BaseFX . . . . . . . . . . . . . . . . . . . 93

Gigabit Ethernet . . . . . . . . . . . . . . . . . . . 94 1000BaseCX . . . . . . . . . . . . . . . . . . . 95 1000BaseSX . . . . . . . . . . . . . . . . . . . 95 1000BaseLX . . . . . . . . . . . . . . . . . . . 95 New Fiber Connectors. . . . . . . . . . . . . . 95 Implementing Multiple Types of Gigabit

Ethernet . . . . . . . . . . . . . . . . . . . 96 10 Gigabit Ethernet . . . . . . . . . . . . . . . . . 97

Fiber-based 10 GbE . . . . . . . . . . . . . . . 97 Copper-based 10 GbE . . . . . . . . . . . . . . 98 10 GbE Physical Connections . . . . . . . . . . 99 Backbones . . . . . . . . . . . . . . . . . . . . 99 Know Your Ethernets!. . . . . . . . . . . . . 100

Chapter 5 Review . . . . . . . . . . . . . . . . . 101

Chapter 6 ■■Installing a Physical Network 106 Historical/Conceptual . . . . . . . . . . . . . . 107 Understanding Structured Cabling . . . . . . . 107

Cable Basics—A Star Is Born . . . . . . . . . 108 Test Specific. . . . . . . . . . . . . . . . . . . . . 109

Structured Cable Network Components . . . 109 Structured Cable—Beyond the Star. . . . . . 116

Installing Structured Cabling . . . . . . . . . . . 119 Getting a Floor Plan. . . . . . . . . . . . . . 119 Mapping the Runs . . . . . . . . . . . . . . 119 Determining the Location of the

Telecommunications Room . . . . . . . . . 120 Pulling Cable . . . . . . . . . . . . . . . . . 121 Making Connections . . . . . . . . . . . . . 123 Testing the Cable Runs . . . . . . . . . . . . 126

NICs . . . . . . . . . . . . . . . . . . . . . . . . . 130 Buying NICs . . . . . . . . . . . . . . . . . 131 Link Lights . . . . . . . . . . . . . . . . . . 133

Diagnostics and Repair of Physical Cabling . . 134 Diagnosing Physical Problems . . . . . . . . 134 Check Your Lights . . . . . . . . . . . . . . . 135 Check the NIC . . . . . . . . . . . . . . . . . 135 Cable Testing . . . . . . . . . . . . . . . . . 136 Problems in the Telecommunications Room . . 136 Toners . . . . . . . . . . . . . . . . . . . . . 137

Chapter 6 Review . . . . . . . . . . . . . . . . . 139

Chapter 7 ■■TCP/IP Basics 144 Historical/Conceptual . . . . . . . . . . . . . . 145 Standardizing Networking Technology . . . . . 145 Test Specific. . . . . . . . . . . . . . . . . . . . . 146 The TCP/IP Protocol Suite . . . . . . . . . . . . 146

Internet Layer Protocols. . . . . . . . . . . . 146 Transport Layer Protocols . . . . . . . . . . . 147 Application Layer Protocols . . . . . . . . . . 149

IP in Depth . . . . . . . . . . . . . . . . . . . . . 150 IP Addresses . . . . . . . . . . . . . . . . . . 151 IP Addresses in Action . . . . . . . . . . . . 155 Class IDs . . . . . . . . . . . . . . . . . . . 162

CIDR and Subnetting . . . . . . . . . . . . . . . 163 Subnetting . . . . . . . . . . . . . . . . . . . 164 CIDR: Subnetting in the Real World . . . . . 169

Using IP Addresses . . . . . . . . . . . . . . . . 170 Static IP Addressing . . . . . . . . . . . . . 170 Dynamic IP Addressing. . . . . . . . . . . . 173 Special IP Addresses. . . . . . . . . . . . . . 176

Chapter 7 Review . . . . . . . . . . . . . . . . . 177

Chapter 8 ■■The Wonderful World of Routing 182 Historical/Conceptual . . . . . . . . . . . . . . 183 How Routers Work . . . . . . . . . . . . . . . . 183 Test Specific. . . . . . . . . . . . . . . . . . . . . 184

Routing Tables. . . . . . . . . . . . . . . . . 184 Freedom from Layer 2 . . . . . . . . . . . . . 191 Network Address Translation . . . . . . . . . 191

Dynamic Routing . . . . . . . . . . . . . . . . . 196 Routing Metrics . . . . . . . . . . . . . . . . 198 Distance Vector . . . . . . . . . . . . . . . . 199 Link State . . . . . . . . . . . . . . . . . . . 204 EIGRP—the Lone Hybrid . . . . . . . . . . . 208 Dynamic Routing Makes the Internet . . . . 209

Working with Routers . . . . . . . . . . . . . . . 209 Connecting to Routers . . . . . . . . . . . . 210 Basic Router Configuration . . . . . . . . . . 215 Router Problems . . . . . . . . . . . . . . . . 216

Chapter 8 Review . . . . . . . . . . . . . . . . . 219

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Chapter 9 ■■TCP/IP Applications 224 Historical/Conceptual . . . . . . . . . . . . . . 225 Transport Layer and Network Layer

Protocols . . . . . . . . . . . . . . . . . . . . . 225 How People Communicate . . . . . . . . . . 225

Test Specific. . . . . . . . . . . . . . . . . . . . . 225 TCP . . . . . . . . . . . . . . . . . . . . . . 225 UDP . . . . . . . . . . . . . . . . . . . . . . 226 ICMP . . . . . . . . . . . . . . . . . . . . . 227 IGMP . . . . . . . . . . . . . . . . . . . . . 227

The Power of Port Numbers . . . . . . . . . . . 228 Registered Ports . . . . . . . . . . . . . . . . 230 Connection Status . . . . . . . . . . . . . . . 232 Rules for Determining Good vs.

Bad Communications . . . . . . . . . . . 236 Common TCP/IP Applications. . . . . . . . . . 236

The World Wide Web . . . . . . . . . . . . . 236 Telnet . . . . . . . . . . . . . . . . . . . . . 242 E-mail . . . . . . . . . . . . . . . . . . . . . 246 FTP . . . . . . . . . . . . . . . . . . . . . . 249 Internet Applications . . . . . . . . . . . . . 252

Chapter 9 Review . . . . . . . . . . . . . . . . . 253

Chapter 10 ■■Network Naming 258 Historical/Conceptual . . . . . . . . . . . . . . 259 DNS . . . . . . . . . . . . . . . . . . . . . . . . . 259 Test Specific. . . . . . . . . . . . . . . . . . . . . 260

How DNS Works . . . . . . . . . . . . . . . 260 Name Spaces. . . . . . . . . . . . . . . . . . 262 DNS Servers . . . . . . . . . . . . . . . . . 272 Troubleshooting DNS . . . . . . . . . . . . . 279

WINS . . . . . . . . . . . . . . . . . . . . . . . . 282 Configuring WINS Clients . . . . . . . . . . 283 Troubleshooting WINS . . . . . . . . . . . . 284

Diagnosing TCP/IP Networks . . . . . . . . . . 284 Chapter 10 Review. . . . . . . . . . . . . . . . . 288

Chapter 11 ■■Securing TCP/IP 294 Test Specific. . . . . . . . . . . . . . . . . . . . . 295 Making TCP/IP Secure . . . . . . . . . . . . . . 295

Encryption. . . . . . . . . . . . . . . . . . . 295 Nonrepudiation . . . . . . . . . . . . . . . . 302 Authentication . . . . . . . . . . . . . . . . 307 Authorization . . . . . . . . . . . . . . . . . 307

TCP/IP Security Standards . . . . . . . . . . . . 308 Authentication Standards . . . . . . . . . . . 308 Encryption Standards . . . . . . . . . . . . . 316 Combining Authentication and Encryption . . 319

Secure TCP/IP Applications . . . . . . . . . . . 320 HTTPS . . . . . . . . . . . . . . . . . . . . 321 SCP . . . . . . . . . . . . . . . . . . . . . . 321 SFTP. . . . . . . . . . . . . . . . . . . . . . 322 SNMP . . . . . . . . . . . . . . . . . . . . . 322 LDAP . . . . . . . . . . . . . . . . . . . . . 323 NTP . . . . . . . . . . . . . . . . . . . . . . 323

Chapter 11 Review . . . . . . . . . . . . . . . . . 324

Chapter 12 ■■Advanced Networking Devices 330 Client/Server and Peer-to-Peer Topologies . . . 331 Historical/Conceptual . . . . . . . . . . . . . . 331

Client/Server . . . . . . . . . . . . . . . . . 331 Peer-to-Peer . . . . . . . . . . . . . . . . . . 332

Test Specific. . . . . . . . . . . . . . . . . . . . . 333 Client/Server and Peer-to-Peer Today. . . . . 333

Virtual Private Networks . . . . . . . . . . . . . 334 PPTP VPNs . . . . . . . . . . . . . . . . . . 335 L2TP VPNs . . . . . . . . . . . . . . . . . . 336 SSL VPNs . . . . . . . . . . . . . . . . . . . 337

Virtual LANs . . . . . . . . . . . . . . . . . . . . 337 Trunking. . . . . . . . . . . . . . . . . . . . 338 Configuring a VLAN-capable Switch. . . . . 339 Virtual Trunk Protocol . . . . . . . . . . . . 341 InterVLAN Routing . . . . . . . . . . . . . 341

Multilayer Switches . . . . . . . . . . . . . . . . 342 Load Balancing . . . . . . . . . . . . . . . . 343 QoS and Traffic Shaping . . . . . . . . . . . 345 Network Protection . . . . . . . . . . . . . . 346

Chapter 12 Review. . . . . . . . . . . . . . . . . 351

Chapter 13 ■■IPv6 356 Test Specific. . . . . . . . . . . . . . . . . . . . . 357 IPv6 Basics . . . . . . . . . . . . . . . . . . . . . 357

IPv6 Address Notation . . . . . . . . . . . . 357 Link-Local Address . . . . . . . . . . . . . . 359 IPv6 Subnet Masks . . . . . . . . . . . . . . 360 The End of Broadcast . . . . . . . . . . . . . 361 Global Address . . . . . . . . . . . . . . . . 363 Aggregation . . . . . . . . . . . . . . . . . . 364

Using IPv6 . . . . . . . . . . . . . . . . . . . . . 366 Enabling IPv6 . . . . . . . . . . . . . . . . . 367 NAT in IPv6. . . . . . . . . . . . . . . . . . 368 DHCP in IPv6 . . . . . . . . . . . . . . . . 369 DNS in IPv6 . . . . . . . . . . . . . . . . . 370

Moving to IPv6 . . . . . . . . . . . . . . . . . . . 371 IPv4 and IPv6 . . . . . . . . . . . . . . . . . 372 Tunnels . . . . . . . . . . . . . . . . . . . . 372 IPv6 Is Here, Really! . . . . . . . . . . . . . 375

Chapter 13 Review. . . . . . . . . . . . . . . . . 376

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Chapter 14 ■■Remote Connectivity 380 Historical/Conceptual . . . . . . . . . . . . . . 381 Telephony and Beyond . . . . . . . . . . . . . . 381

The Dawn of Long Distance. . . . . . . . . . 382 Test Specific. . . . . . . . . . . . . . . . . . . . . 386

Digital Telephony . . . . . . . . . . . . . . . 386 Copper Carriers: T1 and T3 . . . . . . . . . . 387 Fiber Carriers: SONET/SDH and OC . . . . 391 Packet Switching . . . . . . . . . . . . . . . 392 Real-World WAN . . . . . . . . . . . . . . . 395 Alternative to Telephony WAN . . . . . . . . 396

The Last Mile . . . . . . . . . . . . . . . . . . . . 397 Dial-Up . . . . . . . . . . . . . . . . . . . . 397 DSL . . . . . . . . . . . . . . . . . . . . . . 401 Cable Modems . . . . . . . . . . . . . . . . . 404 Satellite . . . . . . . . . . . . . . . . . . . . 406 Cellular WAN . . . . . . . . . . . . . . . . . 406 Fiber . . . . . . . . . . . . . . . . . . . . . . 407 BPL . . . . . . . . . . . . . . . . . . . . . . 407 Which Connection? . . . . . . . . . . . . . . 408

Using Remote Access . . . . . . . . . . . . . . . 408 Dial-Up to the Internet . . . . . . . . . . . . 409 Private Dial-Up . . . . . . . . . . . . . . . . 410 VPNs . . . . . . . . . . . . . . . . . . . . . 411 Dedicated Connection . . . . . . . . . . . . . 411 Remote Terminal . . . . . . . . . . . . . . . 413

Chapter 14 Review. . . . . . . . . . . . . . . . . 417

Chapter 15 ■■Wireless Networking 424 Historical/Conceptual . . . . . . . . . . . . . . 425 Test Specific. . . . . . . . . . . . . . . . . . . . . 425 Wi-Fi Standards . . . . . . . . . . . . . . . . . . 425

802.11 . . . . . . . . . . . . . . . . . . . . . 425 802.11b . . . . . . . . . . . . . . . . . . . . 432 802.11a . . . . . . . . . . . . . . . . . . . . 432 802.11g . . . . . . . . . . . . . . . . . . . . 433 802.11n . . . . . . . . . . . . . . . . . . . . 433 Wireless Networking Security . . . . . . . . 434 Power over Ethernet. . . . . . . . . . . . . . 437

Implementing Wi-Fi . . . . . . . . . . . . . . . . 437 Performing a Site Survey . . . . . . . . . . . 438 Installing the Client . . . . . . . . . . . . . . 439 Setting Up an Ad Hoc Network. . . . . . . . 439 Setting Up an Infrastructure Network . . . . 439 Extending the Network . . . . . . . . . . . . 446 Verify the Installation . . . . . . . . . . . . . 448

Troubleshooting Wi-Fi . . . . . . . . . . . . . . . 448 Hardware Troubleshooting . . . . . . . . . . 448 Software Troubleshooting . . . . . . . . . . . 449

Connectivity Troubleshooting . . . . . . . . . 449 Configuration Troubleshooting . . . . . . . . 450

Chapter 15 Review. . . . . . . . . . . . . . . . . 452

Chapter 16 ■■Protecting Your Network 458 Test Specific. . . . . . . . . . . . . . . . . . . . . 459 Common Threats. . . . . . . . . . . . . . . . . . 459

System Crash/Hardware Failure . . . . . . . 459 Administrative Access Control . . . . . . . . 459 Malware . . . . . . . . . . . . . . . . . . . . 460 Social Engineering . . . . . . . . . . . . . . 462 Man in the Middle . . . . . . . . . . . . . . 463 Denial of Service. . . . . . . . . . . . . . . . 463 Physical Intrusion . . . . . . . . . . . . . . . 464 Attacks on Wireless Connections . . . . . . . 465

Securing User Accounts . . . . . . . . . . . . . . 466 Authentication . . . . . . . . . . . . . . . . 466 Passwords . . . . . . . . . . . . . . . . . . . 467 Controlling User Accounts . . . . . . . . . . 468

Firewalls . . . . . . . . . . . . . . . . . . . . . . 470 Hiding the IPs . . . . . . . . . . . . . . . . . 471 Port Filtering . . . . . . . . . . . . . . . . . 471 Packet Filtering . . . . . . . . . . . . . . . . 473 MAC Filtering . . . . . . . . . . . . . . . . 474 Personal Firewalls . . . . . . . . . . . . . . . 474 Network Zones . . . . . . . . . . . . . . . . 476 Vulnerability Scanners . . . . . . . . . . . . 477

Chapter 16 Review. . . . . . . . . . . . . . . . . 478

Chapter 17 ■■Virtualization 484 Historical/Conceptual . . . . . . . . . . . . . . 485 What Is Virtualization? . . . . . . . . . . . . . . 485

Meet the Hypervisor. . . . . . . . . . . . . . 486 Emulation vs. Virtualization . . . . . . . . . 486 Sample Virtualization . . . . . . . . . . . . . 488

Test Specific. . . . . . . . . . . . . . . . . . . . . 492 Why Do We Virtualize? . . . . . . . . . . . . . . 492

Power Saving . . . . . . . . . . . . . . . . . 492 Hardware Consolidation . . . . . . . . . . . 493 System Recovery . . . . . . . . . . . . . . . 493 System Duplication . . . . . . . . . . . . . . 494 Research . . . . . . . . . . . . . . . . . . . . 494

Virtualization in Modern Networks . . . . . . . 494 Virtual Machine Managers . . . . . . . . . . 496 Hypervisors . . . . . . . . . . . . . . . . . . 497 Virtual Switches . . . . . . . . . . . . . . . 498 Virtual PBX . . . . . . . . . . . . . . . . . . 499 Network as a Service . . . . . . . . . . . . . 499

Chapter 17 Review. . . . . . . . . . . . . . . . . 500

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Chapter 18 ■■Network Management 504 Test Specific. . . . . . . . . . . . . . . . . . . . . 505 Network Configuration Management . . . . . . 505

Configuration Management Documentation . . 505 Change Management Documentation . . . . 511

Monitoring Performance and Connectivity . . . 512 Performance Monitor . . . . . . . . . . . . . 512 Logs and Network Traffic . . . . . . . . . . . 518

Network Performance Optimization . . . . . . 519 Caching . . . . . . . . . . . . . . . . . . . . 520 Controlling Data Throughput. . . . . . . . . 520 Keeping Resources Available . . . . . . . . . 522

Chapter 18 Review. . . . . . . . . . . . . . . . . 528

Chapter 19 ■■Building a SOHO Network 534 Historical/Conceptual . . . . . . . . . . . . . . 535 Test Specific. . . . . . . . . . . . . . . . . . . . . 535 Designing a SOHO Network . . . . . . . . . . . 535 Building the Network . . . . . . . . . . . . . . . 536

Define the Network Needs. . . . . . . . . . . 536 Network Design . . . . . . . . . . . . . . . . 537 Compatibility Issues . . . . . . . . . . . . . . 539 Internal Connections . . . . . . . . . . . . . 540 External Connections . . . . . . . . . . . . . 544 ISPs and MTUs . . . . . . . . . . . . . . . . 546 Peripherals. . . . . . . . . . . . . . . . . . . 548

Security . . . . . . . . . . . . . . . . . . . . . . . 549 Chapter 19 Review. . . . . . . . . . . . . . . . . 550

Chapter 20 ■■Network Troubleshooting 554 Test Specific. . . . . . . . . . . . . . . . . . . . . 555 Troubleshooting Tools . . . . . . . . . . . . . . . 555

Hardware Tools . . . . . . . . . . . . . . . . 555 Software Tools . . . . . . . . . . . . . . . . . 558

The Troubleshooting Process . . . . . . . . . . . 564 Identify the Problem . . . . . . . . . . . . . . 565 Establish a Theory of Probable Cause . . . . . 567

Test the Theory to Determine Cause . . . . . 567 Establish a Plan of Action and Identify

Potential Effects . . . . . . . . . . . . . . 568 Implement and Test the Solution or

Escalate as Necessary . . . . . . . . . . . 568 Verify Full System Functionality and

Implement Preventative Measures . . . . . 569 Document Findings, Actions, and

Outcomes . . . . . . . . . . . . . . . . . . 569 Troubleshooting Scenarios . . . . . . . . . . . . 569

“I Can’t Log In!” . . . . . . . . . . . . . . . 570 “I Can’t Get to This Web Site!” . . . . . . . . 570 “Our Web Server Is Sluggish!” . . . . . . . . 571 “I Can’t See Anything on the Network!” . . . 571 “It’s Time to Escalate!” . . . . . . . . . . . . 572 Troubleshooting Is Fun! . . . . . . . . . . . . 574

Chapter 20 Review. . . . . . . . . . . . . . . . . 575

Appendix A ■■Objectives Map: CompTIA

Network+ 580

Appendix B ■■About the Download 592

System Requirements . . . . . . . . . . . . . . . 592 Installing and Running Total Tester . . . . . . . 592 About Total Tester 593

Mike Meyers’ Video Training 593 Mike’s Cool Tools . . . . . . . . . . . . . . . . . 594

Boson’s NetSim Network Simulator . . . . . . . 594 Technical Support . . . . . . . . . . . . . . . . . 595

Boson Technical Support . . . . . . . . . . . 595

■■Glossary 596

■■Index 632

. . . . . . . . . . . . . . . . . Playing Mike Meyers’ Videos 593 . . . . . . . . . .

. . . . . . . . . .

BaseTech

xvii Preface

I was a teacher long before I was ever an author. I started writing computer books for the simple reason that no one wrote the kind of books I wanted to read. The books were either too simple (Chapter 1, “Using Your Mouse”) or too complex (Chapter 1, “TTL Logic and Transistors”) and none of them provided a motivation for me to learn the information. I guessed that there were geeky readers just like me who wanted to know why they needed to know the information in a computer book.

Good books motivate the reader to learn what he or she is reading. If a book discusses binary arithmetic but doesn’t explain why I need to learn it, for example, that’s not a good book. Tell me that understanding binary makes it easier to understand how an IP address works or why we’re about to run out of IP addresses and how IPv6 can help, then I get excited, no mat- ter how geeky the topic. If I don’t have a good reason, a good motivation to do something, then I’m simply not going to do it (which explains why I haven’t jumped out of an airplane!).

In this book, I teach you why you need to understand the wide world of networking. You’ll learn everything you need to start building, configuring, and supporting networks. In the process, you’ll gain the knowledge you need to pass the CompTIA Network+ certification exam.

Enjoy, my fellow geek.

PrEfACE

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xix CompTIA Approved Quality Curriculum

CompTIA APProvEd QuALITy CurrICuLuM

CompTIA Network+■■ The CompTIA Network+ certification ensures that the successful candidate has the important knowledge and skills necessary to manage, maintain, troubleshoot, install, operate, and configure basic network infrastructure; describe networking technologies; basic design principles; and adhere to wiring standards and use testing tools.

It Pays to Get Certified■■ In a digital world, digital literacy is an essential survival skill. Certification proves you have the knowledge and skill to solve business problems in virtually any business environment. Certifications are highly valued cre- dentials that qualify you for jobs, increased compensation, and promotion.

CompTIA Network+ certification is held by many IT staffers across many organizations. 21% of IT staff within a random sampling of U.S. orga- nizations within a cross section of industry verticals hold CompTIA Net- work+ certification.

The CompTIA Network+ credential—proves knowledge of ■ networking features and functions and is the leading vendor-neutral certification for networking professionals.

Starting salary—the average starting salary of network engineers can ■ be up to $70,000.

Career pathway—CompTIA Network+ is the first step in starting a ■ networking career, and is recognized by Microsoft as part of their MS program. Other corporations, such as Novell, Cisco, and HP also recognize CompTIA Network+ as part of their certification tracks.

More than 325,000 individuals worldwide are CompTIA Network+ ■ certified.

Mandated/recommended by organizations worldwide—Apple, ■ Cisco, HP, Ricoh, the U.S. State Department, and U.S. government contractors such as EDS, General Dynamics, and Northrop Grumman recommend or mandate CompTIA Network+.

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CompTIA Approved Quality Curriculum

How Certification Helps Your Career

CompTIA Career Pathway CompTIA offers a number of credentials that form a foundation for your career in technology and that allow you to pursue specific areas of concentration. Depend- ing on the path you choose, CompTIA certifications help you build upon your skills and knowledge, supporting learning throughout your career.

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xxi CompTIA Approved Quality Curriculum

Steps to Getting Certified and ■■ Staying Certified

Review exam objectives.1. Review the certification objectives to make sure you know what is covered in the exam: www.comptia.org/certifications/testprep/examobjectives.aspx

Practice for the exam.2. After you have studied for the certification, take a free assessment and sample test to get an idea what type of questions might be on the exam: www.comptia.org/certifications/testprep/practicetests.aspx

Purchase an exam voucher.3. Purchase exam vouchers on the CompTIA Marketplace, which is located at: www.comptiastore.com

Take the test!4. Select a certification exam provider, and schedule a time to take your exam. You can find exam providers at the following link: www.comptia.org/certifications/testprep/testingcenters.aspx

Stay certified!5. Continuing education is required. Effective January 1, 2011, CompTIA Network+ certifications are valid for three years from the date of certification. There are a number of ways the certification can be renewed. For more information go to: http:// certification.comptia.org/getCertified/steps_to_certification/ stayCertified.aspx

Join the Professional Community■■ The free online IT Pro Community provides valuable content to students and professionals. Join the IT Pro Community:

http://itpro.comptia.org

Career IT job resources include:

Where to start in IT ■

Career assessments ■

Salary trends ■

U.S. job board ■

Join the IT Pro Community and get access to:

Forums on networking, security, computing, and cutting-edge ■ technologies

Access to blogs written by industry experts ■www.comptia.org/certifications/testprep/examobjectives.aspxwww.comptia.org/certifications/testprep/practicetests.aspxwww.comptiastore.comwww.comptia.org/certifications/testprep/testingcenters.aspxhttp://certification.comptia.org/getCertified/steps_to_certification/stayCertified.aspxhttp://certification.comptia.org/getCertified/steps_to_certification/stayCertified.aspxhttp://certification.comptia.org/getCertified/steps_to_certification/stayCertified.aspxhttp://itpro.comptia.org

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CompTIA Approved Quality Curriculum

Current information on cutting edge technologies ■

Access to various industry resource links and articles related to IT ■ and IT careers

APPRO V E D Q U A L I T Y C O

N T EN

T Content Seal of Quality■■

This courseware bears the seal of CompTIA Approved Quality Content. This seal signifies this content covers 100 percent of the exam objectives and implements important instructional design principles. CompTIA rec- ommends multiple learning tools to help increase coverage of the learning objectives.

Why CompTIA?■■ Global recognition ■ CompTIA is recognized globally as the leading IT nonprofit trade association and has enormous credibility. Plus, CompTIA’s certifications are vendor-neutral and offer proof of foundational knowledge that translates across technologies.

Valued by hiring managers ■ Hiring managers value CompTIA certification because it is vendor- and technology-independent validation of your technical skills.

Recommended or required by government and businesses ■ Many government organizations and corporations (for example, Dell, Sharp, Ricoh, the U.S. Department of Defense, and many more) either recommend or require technical staff to be CompTIA certified.

Three CompTIA certifications ranked in the top 10 ■ In a study by DICE of 17,000 technology professionals, certifications helped command higher salaries at all experience levels.

BaseTech

CompTIA Approved Quality Curriculum

How to Obtain More Information■■ Visit CompTIA online ■ Go to www.comptia.org to learn more about getting CompTIA certified.

Contact CompTIA ■ Please call 866-835-8020, ext. 5 or e-mail questions@comptia.org.

Join the IT Pro Community ■ Go to http://itpro.comptia.org to join the IT community to get relevant career information.

Connect with CompTIA ■ Find us on Facebook, LinkedIn, Twitter, and YouTube.

CAQC Disclaimer■■ The logo of the CompTIA Approved Quality Curriculum (CAQC) program and the status of this or other training material as “Approved” under the CompTIA Approved Quality Curriculum program signifies that, in Comp- TIA’s opinion, such training material covers the content of CompTIA’s related certification exam.

The contents of this training material were created for the CompTIA Network+ exam covering CompTIA certification objectives that were cur- rent as of the date of publication.

CompTIA has not reviewed or approved the accuracy of the contents of this training material and specifically disclaims any warranties of mer- chantability or fitness for a particular purpose. CompTIA makes no guaran- tee concerning the success of persons using any such “Approved” or other training material in order to prepare for any CompTIA certification exam.

xxiiiwww.comptia.orghttp://itpro.comptia.org

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Instructor and Student Web Site

INsTruCTor ANd sTudENT WEb sITE

For instructor and student resources, please visit:

www.meyersnetplus.com

Students will find chapter quizzes that will help them learn more about troubleshooting and fixing networks, and teachers can access the support materials outlined below.

Additional Resources for Teachers■■ McGraw-Hill Connect, a Web-based learning platform, connects instructors with their support materials and students with chapter assessments. The Connect Online Learning Center provides resources for teachers in a format that follows the organization of the textbook.

This site includes the following:

Answer keys to the end-of-chapter activities in the textbook ■

Instructor’s Manual that contains learning objectives, classroom ■ preparation notes, instructor tips, and a lecture outline for each chapter

Answer keys to the Mike Meyers’ Lab Manual activities (available ■ separately)

Access to test bank files and software that allow you to generate ■ a wide array of paper- or network-based tests, and that feature automatic grading. The test bank includes:

Hundreds of practice questions and a wide variety of question ■ types categorized by exam objective, enabling you to customize each test to maximize student progress

Test bank files available on EZ Test Online and as downloads ■ from the Online Learning Center in these formats: Blackboard, Web CT, EZ Test, and Word

Engaging PowerPoint slides on the lecture topics that include full- ■ color artwork from the book

Please contact your McGraw-Hill sales representative for details.

xxv

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1 chapter

/ Mike Meyers’ CompTIA Network+ Guide to Managing and Troubleshooting Networks, Third Edition / Meyers / 911-1 / Chapter 1

“Networking is an essential part

of building wealth.”

—Armstrong WilliAms

CompTIA Network+ in a Nutshell

In this chapter, you will learn how to

Describe the importance of ■■ CompTIA Network+ certification

Illustrate the structure and ■■ contents of the CompTIA Network+ certification exam

Plan a strategy to prepare for ■■ the exam

By picking up this book, you’ve shown an interest in learning about networking. But be forewarned. The term networking describes a vast field of study, far too large for any single certification, book, or training course to

cover. Do you want to configure routers and switches for a living? Do you want

to administer a large Windows network at a company? Do you want to install

wide area network connections? Do you want to set up Web servers? Do you

want to secure networks against attacks?

If you’re considering a CompTIA Network+ certification, you probably don’t

yet know exactly what aspect of networking you want to pursue, and that’s

okay! You’re going to love preparing for the CompTIA Network+ certification.

Attaining CompTIA Network+ certification provides you with three

fantastic benefits. First, you get a superb overview of networking that helps

you decide what part of the industry you’d like to pursue. Second, it acts as

a prerequisite toward other, more advanced certifications. Third, the amount

of eye-opening information you’ll gain just makes getting CompTIA Network+

certified plain old fun.

1 chapter

BaseTech / Mike Meyers’ CompTIA Network+ Guide to Managing and Troubleshooting Networks, Third Edition / Meyers / 911-1 / Chapter 1

Chapter 1: CompTIA Network+ in a Nutshell 1

CompTIA Network+ in a Nutshell

Nothing comes close to providing a better overview of networking than CompTIA Network+. The certification covers local area networks (LANs), wide area networks (WANs), the Internet, security, cabling, and applica- tions in a wide-but-not-too-deep fashion that showcases the many different parts of a network and hopefully tempts you to investigate the aspects that intrigue you by looking into follow-up certifications.

The process of attaining CompTIA Network+ certification will give you a solid foundation in the whole field of networking. Mastering the compe- tencies will help fill in gaps in your knowledge and provide an ongoing series of “a-ha!” moments of grasping the big picture that make being a tech so much fun.

Ready to learn a lot, grab a great certification, and have fun doing it? Then welcome to CompTIA Network+ certification!

Who Needs CompTIA Network+? ■■ I Just Want to Learn about Networks!

Whoa up there, amigo! Are you one of those folks who either has never heard of the CompTIA Network+ exam or just doesn’t have any real inter- est in certification? Is your goal only to get a solid handle on the idea of networking and a jump start on the basics? Are you looking for that “magic bullet” book that you can read from beginning to end and then start install- ing and troubleshooting a network? Do you want to know what’s involved with running network cabling in your walls or getting your new wireless network working? Are you tired of not knowing enough about what TCP/ IP is and how it works? If these types of questions are running through your mind, then rest easy—you have the right book. Like every book with the Mike Meyers name, you’ll get solid concepts without pedantic details or broad, meaningless overviews. You’ll look at real-world networking as performed by real techs. This is a book that understands your needs and goes well beyond the scope of a single certification.

If the CompTIA Network+ exam isn’t for you, you can skip the rest of this chapter, shift your brain into learn mode, and dive into Chapter 2. But then, if you’re going to have the knowledge, why not get the certification?

What Is CompTIA Network+ ■■ Certification?

CompTIA Network+ certification is an industry-wide, vendor-neutral certi- fication program developed and sponsored by the Computing Technology Industry Association (CompTIA). The CompTIA Network+ certification shows that you have a basic competency in the physical support of net- working systems and knowledge of the conceptual aspects of networking.

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To date, many hundreds of thousands of technicians have become CompTIA Network+ certified.

CompTIA Network+ certification enjoys wide recognition throughout the IT industry. At first, it rode in on the coattails of the successful CompTIA A+ certification program, but it now stands on its own in the network- ing industry and is considered the obvious next step after CompTIA A+ certification.

What Is CompTIA? CompTIA is a nonprofit, industry trade association based in Oakbrook Ter- race, Illinois, on the outskirts of Chicago. Tens of thousands of computer resellers, value-added resellers, distributors, manufacturers, and training companies from all over the world are members of CompTIA.

CompTIA was founded in 1982. The following year, CompTIA began offering the CompTIA A+ certification exam. CompTIA A+ certification is now widely recognized as a de facto requirement for entrance into the PC industry. Because the CompTIA A+ exam covers networking only lightly, CompTIA decided to establish a vendor-neutral test covering basic net- working skills. So, in April 1999, CompTIA unveiled the CompTIA Net- work+ certification exam.

CompTIA provides certifications for a variety of areas in the computer industry, offers opportunities for its members to interact, and represents its members’ interests to government bodies. CompTIA certifications include CompTIA A+, CompTIA Network+, and CompTIA Security+, to name a few. Check out the CompTIA Web site at www.comptia.org for details on other certifications.

CompTIA is huge. Virtually every company of consequence in the IT industry is a member of CompTIA: Microsoft, Dell, Cisco… Name an IT company and it’s probably a member of CompTIA.

The Current CompTIA Network+ Certification Exam Release CompTIA constantly works to provide exams that cover the latest technolo- gies and, as part of that effort, periodically updates its certification objec- tives, domains, and exam questions. This book covers all you need to know to pass the N10-005 CompTIA Network+ exam released in 2011.

How Do I Become CompTIA Network+ Certified? To become CompTIA Network+ certified, you simply pass one computer- based, multiple-choice exam. There are no prerequisites for taking the CompTIA Network+ exam, and no networking experience is needed. You’re not required to take a training course or buy any training materials. The only requirements are that you pay a testing fee to an authorized test- ing facility and then sit for the exam. Upon completion of the exam, you will immediately know whether you passed or failed.www.comptia.org

BaseTech / Mike Meyers’ CompTIA Network+ Guide to Managing and Troubleshooting Networks, Third Edition / Meyers / 911-1 / Chapter 1

Chapter 1: CompTIA Network+ in a Nutshell 3

Once you pass, you become CompTIA Network+ certified for three years. After three years, you’ll need to renew your certification by retaking the current exam or completing approved Continuing Education activities. By completing these activities, you earn credits that (along with an annual fee) allow you to keep your CompTIA Network+ certification. For a full list of approved activities, check out CompTIA’s Web site (www.comptia.org) and search for CompTIA Continuing Education Program.

Now for the details: CompTIA recommends that you have at least nine to twelve months of networking experience and CompTIA A+ knowl- edge, but this is not a requirement. Note the word “recommend.” You may not need experience or CompTIA A+ knowledge, but they help! The CompTIA A+ certification competencies have a degree of overlap with the CompTIA Network+ competencies, such as types of connectors and how networks work.

As for experience, keep in mind that CompTIA Network+ is mostly a practical exam. Those who have been out there supporting real networks will find many of the questions reminiscent of the types of problems they have seen on LANs. The bottom line is that you’ll probably have a much easier time on the CompTIA Network+ exam if you have some CompTIA A+ experience under your belt.

What Is the Exam Like?■■ The CompTIA Network+ exam contains 100 questions, and you have 90 minutes to complete the exam. To pass, you must score at least 720 on a scale of 100–900, at the time of this writing. Check the CompTIA Web site when you get close to testing to determine the current scale: http://certification.comptia.org/getCertified/certifications/network.aspx

The exam questions are divided into five areas that CompTIA calls domains. This table lists the CompTIA Network+ domains and the percent- age of the exam that each represents.

CompTIA Network+ Domain Percentage

1.0 Network Technologies 21%

2.0 Network Installation and Configuration 23%

3.0 Network Media and Topologies 17%

4.0 Network Management 20%

5.0 Network Security 19%

The CompTIA Network+ exam is extremely practical. Questions often present real-life scenarios and ask you to determine the best solution. The CompTIA Network+ exam loves troubleshooting. Let me repeat: many of the test objectives deal with direct, real-world troubleshooting. Be prepared to troubleshoot both hardware and software failures and to answer both “What do you do next?” and “What is most likely the problem?” types of questions.

A qualified CompTIA Network+ certification candidate can install and configure a PC to connect to a network. This includes installing andwww.comptia.orghttp://certification.comptia.org/getCertified/certifications/network.aspx

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testing a network card, configuring drivers, and loading all network soft- ware. The exam will test you on the different topologies, standards, and cabling.

Expect conceptual questions about the Open Systems Interconnec- tion (OSI) seven-layer model. If you’ve never heard of the OSI seven-layer model, don’t worry! This book will teach you all you need to know. While this model rarely comes into play during the daily grind of supporting a network, you need to know the functions and protocols for each layer to pass the CompTIA Network+ exam. You can also expect questions on most of the protocol suites, with heavy emphasis on the TCP/IP suite.

How Do I Take the Test? To take the test, you must go to an authorized testing center. You cannot take the test over the Internet. Prometric and Pearson VUE administer the actual CompTIA Network+ exam. You’ll find thousands of Prometric and Pearson VUE testing centers scattered across the United States and Canada, as well as in over 75 other countries around the world. You may take the exam at any testing center. To locate a testing center and schedule an exam, call Prometric at 888-895-6116 or Pearson VUE at 877-551-7587. You can also visit their Web sites at www.prometric.com and www.vue.com.

How Much Does the Test Cost? CompTIA fixes the price, no matter what testing center you use. The cost of the exam depends on whether you work for a CompTIA member. At press time, the cost for non-CompTIA members is US$246.

If your employer is a CompTIA member, you can save money by obtain- ing an exam voucher. In fact, even if you don’t work for a CompTIA member, you can purchase a voucher from member companies and take advantage of significant member savings. You simply buy the voucher and then use the voucher to pay for the exam. Vouchers are delivered to you on paper and electronically via e-mail. The voucher number is the important thing. That number is your exam payment, so protect it from fellow students until you’re ready to schedule your exam.

If you’re in the United States or Canada, you can visit www.totalsem .com or call 800-446-6004 to purchase vouchers. As I always say, “You don’t have to buy your voucher from us, but for goodness’ sake, get one from somebody!” Why pay full price when you have a discount alternative?

You must pay for the exam when you schedule, whether online or by phone. If you’re scheduling by phone, be prepared to hold for a while. Have your Social Security number (or the international equivalent) ready and either a credit card or a voucher number when you call or begin the online scheduling process. If you require any special accommodations, both Pro- metric and Pearson VUE will be able to assist you, although your selection of testing locations may be a bit more limited.

International prices vary; see the CompTIA Web site for international pricing. Of course, prices are subject to change without notice, so always check the CompTIA Web site for current pricing!

CompTIA occasionally makes changes to the content of the exam, as well as the score necessary to pass it. Always check the Web site of my company, Total Seminars (www.totalsem.com), before scheduling your exam.

Although you can’t take the exam over the Internet, both Prometric and Pearson VUE provide easy online registration. Go to www.prometric.com or www.vue.com to register online.www.totalsem.comwww.prometric.comwww.vue.comwww.prometric.comwww.vue.comwww.totalsem.comwww.totalsem.com

BaseTech / Mike Meyers’ CompTIA Network+ Guide to Managing and Troubleshooting Networks, Third Edition / Meyers / 911-1 / Chapter 1

Chapter 1: CompTIA Network+ in a Nutshell 5

How to Pass the CompTIA ■■ Network+ Exam

The single most important thing to remember about the CompTIA Net- work+ certification exam is that CompTIA designed it to test the knowl- edge of a technician with as little as nine months of experience—so keep it simple! Think in terms of practical knowledge. Read this book, answer the questions at the end of each chapter, take the practice exams on the media accompanying this book, review any topics you missed, and you’ll pass with flying colors.

Is it safe to assume that it’s probably been a while since you’ve taken an exam? Consequently, has it been a while since you’ve had to study for an exam? If you’re nodding your head yes, you’ll probably want to read the next sections. They lay out a proven strategy to help you study for the CompTIA Network+ exam and pass it. Try it. It works.

Obligate Yourself The first step you should take is to schedule the exam. Ever heard the old adage that heat and pressure make diamonds? Well, if you don’t give your- self a little “heat,” you might procrastinate and unnecessarily delay taking the exam. Even worse, you may end up not taking the exam at all. Do your- self a favor. Determine how much time you need to study (see the next sec- tion), and then call Prometric or Pearson VUE and schedule the exam, giving yourself the time you need to study—and adding a few extra days for safety. Afterward, sit back and let your anxieties wash over you. Suddenly, turning off the television and cracking open the book will become a lot easier! Keep in mind that Prometric and Pearson VUE let you schedule an exam only a few weeks in advance, at most. If you schedule an exam and can’t make it, you must reschedule at least a day in advance or lose your money.

Set Aside the Right Amount of Study Time After helping thousands of techs get their CompTIA Network+ certifica- tion, we at Total Seminars have developed a pretty good feel for the amount of study time needed to pass the CompTIA Network+ exam. Table 1.1 will help you plan how much study time you must devote to the exam. Keep in mind that these are averages. If you’re not a great student or if you’re a little on the nervous side, add another 10 percent. Equally, if you’re the type who can learn an entire semester of geometry in one night, reduce the numbers by 10 percent. To use this table, just circle the values that are most accurate for you and add them up to get the number of study hours.

A complete neophyte will need at least 120 hours of study time. An experienced network technician already CompTIA A+ certified should only need about 24 hours.

Study habits also come into play here. A person with solid study habits (you know who you are) can reduce the number by 15 percent. People with poor study habits should increase that number by 20 percent.

The total hours of study time you need is __________________.

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/ Mike Meyers’ CompTIA Network+ Guide to Managing and Troubleshooting Networks, Third Edition / Meyers / 911-1 / Chapter 1

Table 1.1 Determining How Much Study Time You Need Amount of Experience

Type of Experience None Once or Twice

On Occasion

Quite a Bit

Installing a SOHO wireless network 4 2 1 1

Installing an advanced wireless network (802.1X, RADIUS, etc.) 2 2 1 1

Installing structured cabling 3 2 1 1

Configuring a home router 5 3 2 1

Configuring a Cisco router 4 2 1 1

Configuring a software firewall 3 2 1 1

Configuring a hardware firewall 2 2 1 1

Configuring an IPv4 client 8 4 2 1

Configuring an IPv6 client 3 3 2 1

Working with a SOHO WAN connection (DSL, cable) 2 2 1 0

Working with an advanced WAN connection (Tx, OCx, ATM) 3 3 2 2

Configuring a DNS server 2 2 2 1

Configuring a DHCP server 2 1 1 0

Configuring a Web application server (HTTP, FTP, SSH, etc.) 4 4 2 1

Configuring a VLAN 3 3 2 1

Configuring a VPN 3 3 2 1 Configuring a dynamic routing protocol (RIP, EIGRP, OSPF) 2 2 1 1

Study for the Test Now that you have a feel for how long it’s going to take to study for the exam, you need a strategy for studying. The following has proven to be an excellent game plan for cramming the knowledge from the study materials into your head.

This strategy has two alternate paths. The first path is designed for highly experienced technicians who have a strong knowledge of PCs and networking and want to concentrate on just what’s on the exam. Let’s call this group the Fast Track group. The second path, and the one I’d strongly recommend, is geared toward people like me: the ones who want to know why things work, those who want to wrap their arms completely around a concept, as opposed to regurgitating answers just to pass the CompTIA Network+ exam. Let’s call this group the Brainiacs.

To provide for both types of learners, I have broken down most of the chapters into two parts:

Historical/Conceptual ■ Although not on the CompTIA Network+ exam, this knowledge will help you understand more clearly what is on the CompTIA Network+ exam.

Test Specific ■ These topics clearly fit under the CompTIA Network+ certification domains.

The beginning of each of these areas is clearly marked with a large ban- ner that looks like the following.

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Chapter 1: CompTIA Network+ in a Nutshell 7

Historical/Conceptual If you consider yourself a Fast Tracker, skip everything but the Test Spe- cific section in each chapter. After reading the Test Specific sections, jump immediately to the Chapter Review questions, which concentrate on infor- mation in the Test Specific sections. If you run into problems, review the Historical/Conceptual sections in that chapter. After going through every chapter as described, take the free practice exams on the media that accom- panies the book. First, take them in practice mode, and then switch to final mode. Once you start scoring in the 80–85 percent range, go take the test!

Brainiacs should first read the book—the whole book. Read it as though you’re reading a novel, starting on Page 1 and going all the way through. Don’t skip around on the first read-through, even if you are a highly expe- rienced tech. Because there are terms and concepts that build on each other, skipping around might confuse you, and you’ll just end up closing the book and firing up your favorite PC game. Your goal on this first read is to under- stand concepts—to understand the whys, not just the hows.

Having a network available while you read through the book helps a lot. This gives you a chance to see various concepts, hardware, and configu- ration screens in action as you read about them in the book. Nothing beats doing it yourself to reinforce a concept or piece of knowledge!

You will notice a lot of historical information—the Historical/ Conceptual sections—that you may be tempted to skip. Don’t! Understanding how some of the older stuff worked or how something works conceptually will help you appreciate the reason behind current networking features and equipment, as well as how they function.

After you have completed the first read-through, cozy up for a second. This time, try to knock out one chapter per sitting. Concentrate on the Test Specific sections. Get a highlighter and mark the phrases and sentences that make major points. Take a hard look at the pictures and tables, noting how they illustrate the concepts. Then, answer the end of chapter questions. Repeat this process until you not only get all the questions right, but also understand why they are correct!

Once you have read and studied the material in the book, check your knowledge by taking the practice exams included on the media accompa- nying the book. The exams can be taken in practice mode or final mode. In practice mode, you are allowed to check references in the book (if you want) before you answer each question, and each question is graded immediately. In final mode, you must answer all the questions before you are given a test score. In each case, you can review a results summary that tells you which questions you missed, what the right answer is, and where to study further.

Use the results of the exams to see where you need to bone up, and then study some more and try them again. Continue retaking the exams and reviewing the topics you missed until you are consistently scoring in the 80–85 percent range. When you’ve reached that point, you are ready to pass the CompTIA Network+ exam!

If you have any problems or questions, or if you just want to argue about something, feel free to send an e-mail to me atmichaelm@totalsem.com or to my editor, Scott Jernigan, at scottj@totalsem.com.

For additional information about the CompTIA Network+ exam, con- tact CompTIA directly at its Web site: www.comptia.org.

Good luck! —Mike Meyers

We have active and helpful discussion groups at www .totalsem.com/forums. You need to register to participate (though not to read posts), but that’s only to keep the spammers at bay. The forums provide an excellent resource for answers, suggestions, and just socializing with other folks studying for the exam.

Be aware that you may need to return to previous chapters to get the Historical/Conceptual information you need for a later chapter.www.totalsem.com/forumswww.totalsem.com/forumswww.comptia.org

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/ Mike Meyers’ CompTIA Network+ Guide to Managing and Troubleshooting Networks, Third Edition / Meyers / 911-1 / Chapter 2

Network Models

“First we thought the PC was a

calculator. Then we found out how

to turn numbers into letters with

ASCII—and we thought it was

a typewriter. Then we discovered

graphics, and we thought it was

a television. With the World

Wide Web, we’ve realized it’s a

brochure.”

—Douglas aDams

In this chapter, you will learn how to

Describe how models such as the ■■ OSI seven-layer model and the TCP/IP model help technicians understand and troubleshoot networks

Explain the major functions of ■■ networks with the OSI seven-layer model

Describe the major functions of ■■ networks with the TCP/IP model

The CompTIA Network+ certification challenges you to understand virtually every aspect of networking—not a small task. Luckily for you, we use two methods to conceptualize the many parts of a network: the Open Systems

Interconnection (OSI) seven-layer model and the Transmission Control

Protocol/Internet Protocol (TCP/IP) model.

These models act as guidelines and break down how a network functions

into discrete parts called layers. If you want to get into networking—and

if you want to pass the CompTIA Network+ certification exam—you must

understand both the OSI seven-layer model and the TCP/IP model in great

detail.

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Chapter 2: Network Models 9

These models provide two tools that make them critical for networking techs. First, the OSI and TCP/IP models provide powerful mental tools for diag- nosing problems. Understand- ing the models enables a tech to determine quickly at what layer a problem can occur and helps him or her zero in on a solution with- out wasting a lot of time on false leads. Second, these models also provide a common language to describe networks—a way for us to communicate with each other about the functions of a network. Figure 2.1 shows a sample Cisco Systems Web page about configuring routing—a topic this book covers in detail later. A router operates at Layer 3 of the OSI seven-layer model, for example, so you’ll hear techs (and Web sites) refer to it as a “Layer 3 switch.”

This chapter looks first at models in general and how models help conceptualize and troubleshoot networks. We’ll then go into both the OSI seven-layer model and the TCP/IP model to see how they help clarify net- work architecture for techs.

Figure 2.1 • Using the OSI terminology—Layer 3—in a typical setup screen

The term “Layer 3 switch” has evolved over time and refers today to a variety of complex network boxes that I’ll cover later in the book.

Cross Check Cisco and Certifications

Cisco Systems, Inc. is famous for making many of the “boxes” that interconnect networks all over the world. It’s not too far of a stretch to say that Cisco helps power a huge portion of the Internet. These boxes are complicated to configure, requiring a high degree of techni- cal knowledge.

To address this need, Cisco offers a series of certifications. One of the entry-level certifications, for example, is the Cisco Certified Net- work Associate (CCNA). Go to Cisco’s certification Web site and com- pare their objectives with what you learned about CompTIA Network+ in Chapter 1. Ask yourself this question: could you study for CCNA and CompTIA Network+ simultaneously?

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Historical/Conceptual

Working with Models■■ Networking is hard. It takes a lot of pieces, both hardware and software, to get anything done. Just making Google appear in your Web browser requires millions of hours in research, development, and manufacturing. Whenever we encounter highly complex technologies, we need to sim- plify the overall process (making Google show up in your browser) by breaking it into discrete, simple, individual processes. We do this using models.

Modeling is critical to the networking world. We use models to under- stand and communicate with other techs about networks. Most beginning network techs, however, might have a very different idea of what model- ing means.

Biography of a Model What does the word “model” mean to you? Does the word make you think of a beautiful woman walking down a catwalk at a fashion show or

some hunky guy showing off the latest style of blue jeans on a huge billboard? Maybe it makes you think of a plastic model airplane? What about those com- puter models that try to predict weather? We use the term “model” in a number of ways, but each use shares certain common themes.

All models are a sim- plified representation of the real thing. The human

model ignores the many different types of body shapes, using only a single “optimal” figure. The model airplane lacks functional engines or the internal framework, and the computerized weather model might disregard subtle differences in wind temperatures or geology (Figure 2.2).

Additionally, a model must have at least all the major functions of the real item, but what constitutes a major rather than a minor function is open to opinion. Figure 2.3 shows a different level of detail for a model. Does it contain all the major components of an airplane? There’s room for argument that perhaps the model should have landing gear to go along with the propeller, wings, and tail.

Figure 2.2 • Types of models (images from left to right courtesy of NOAA, Mike Schinkel, and Michael Smyer)

Figure 2.3 • Simple model airplane

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Network Models Network models face similar challenges. What functions define all net- works? What details can you omit without rendering the model inaccurate? Does the model retain its usefulness when describing a network that does not employ all the layers?

In the early days of networking, different manufacturers made unique types of networks that functioned fairly well. But each network had its own cabling, hardware, drivers, naming conventions, applications, and many other unique features. Back then, a single manufacturer provided every- thing for a customer whenever you purchased a network solution: cabling, NICs, hubs, drivers, and all the software in one complete and expensive package. Although these networks worked fine as stand-alone networks, the proprietary nature of the hardware and software made it difficult—to put it mildly—to connect networks of multiple manufacturers. To intercon- nect networks and improve networking as a whole, someone needed to create a guide, a model that described the functions of a network, so that people who made hardware and software could work together to make networks that worked together well.

The granddaddy of network models came from the International Orga- nization for Standardization, known as ISO. Their model, known as the OSI seven-layer model, works for almost every type of network, even extremely old and long-obsolete ones. On the other hand, the TCP/IP model only works for networks that use the now-dominant TCP/IP protocol suite. (Don’t worry about what TCP/IP means yet—most of this book’s job is to explain that in great detail.) Since most of the world uses TCP/IP, the TCP/ IP model supplanted the OSI model in many cases, though most discussion that involves the word “Layers” refers to the OSI model. A good tech can talk the talk of both models, and they are objectives on the CompTIA Net- work+ exam, so let’s learn both.

The best way to learn the OSI and TCP/IP models is to see them in action. For this reason, I’ll introduce you to a small network that needs to copy a file from one computer to another. This example goes through each of the OSI and TCP/IP layers needed to copy that file, and I explain each step and why it is necessary. By the end of the chapter, you should have a definite handle on using either of these models as a tool to conceptualize networks. You’ll continue to build on this knowledge throughout the book and turn your OSI and TCP/IP model knowledge into a powerful troubleshooting tool.

I’ll begin by discussing the OSI seven-layer model. After seeing this small network through the lens of the OSI seven-layer model, we’ll repeat the process with the TCP/IP model.

The OSI Seven-Layer Model ■■ in Action

Each layer in the OSI seven-layer model defines an important function in computer networking, and the protocols that operate at that layer offer solutions to those functions. Protocols are sets of clearly defined rules,

ISO may look like a misspelled acronym, but it’s actually a word, derived from the Greek word isos, which means “equal.” The International Organization for Standardization sets standards that promote equality among network designers and manufacturers, thus ISO.

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regulations, standards, and procedures that enable hardware and software developers to make devices and applications that function properly at a particular level. The OSI seven-layer model encourages modular design in networking, meaning that each layer has as little to do with the opera- tion of other layers as possible. Think of it as an automobile assembly line. The guy painting the car doesn’t care about the gal putting doors on the car—he expects the assembly line process to make sure the cars he paints have doors. Each layer on the model trusts that the other layers on the model do their jobs.

The OSI seven layers are:

Layer 7 ■ Application

Layer 6 ■ Presentation

Layer 5 ■ Session

Layer 4 ■ Transport

Layer 3 ■ Network

Layer 2 ■ Data Link

Layer 1 ■ Physical

The OSI seven layers are not laws of physics—anybody who wants to design a network can do it any way he or she wants. Although many protocols fit neatly into one of the seven layers, others do not.

Now that you know the names of the layers, let’s see what each layer does. The best way to understand the OSI layers is to see them in action. Let’s see them at work at the fictional company of MHTechEd, Inc.

Welcome to MHTechEd! Mike’s High-Tech Educational Supply Store and Post Office, or MHTechEd for short, has a small network of PCs running Windows, a situation typi- cal of many small businesses today. Windows runs just fine on a PC uncon- nected to a network, but it also comes with all the network software it needs to connect to a network. All the computers in the MHTechEd net- work are connected by special network cabling.

As in most offices, virtually everyone at MHTechEd has his or her own PC. Figure 2.4 shows two workers, Janelle and Dana, who han- dle all the administrative functions at MHTechEd. Because of the kinds of work they do, these two often need to exchange data between their two PCs. At the moment, Janelle has just completed a new employee handbook in Microsoft Word, and she wants Dana to check it for accuracy. Janelle could transfer a copy of the file to Dana’s com- puter by the tried-and-true Sneakernet method— saving the file on a thumb drive and walking it over to her—but thanks to the wonders of com- puter networking, she doesn’t even have to turn around in her chair. Let’s watch in detail each

Be sure to memorize both the name and the number of each OSI layer. Network techs use OSI terms such as “Layer 4” and “Transport layer” synonymously. Students have long used mnemonics for memorizing such lists. One of my favorites for the OSI seven-layer model is “Please Do Not Throw Sausage Pizza Away.” Yum!

This section is a conceptual overview of the hardware and software functions of a network. Your network may have different hardware or software, but it will share the same functions!

Figure 2.4 • Janelle and Dana, hard at work

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piece of the process that gives Dana direct access to Janelle’s computer, so she can copy the Word document from Janelle’s system to her own.

Long before Janelle ever saved the Word document on her system— when the systems were first installed—someone who knew what they were doing set up and configured all the systems at MHTechEd to be part of a common network. All this setup activity resulted in multiple layers of hardware and software that can work together behind the scenes to get that Word document from Janelle’s system to Dana’s. Let’s examine the differ- ent pieces of the network, and then return to the process of Dana grabbing that Word document.

Test Specific

Let’s Get Physical—Network ■■ Hardware and Layers 1–2

Clearly the network needs a physical channel through which it can move bits of data between systems. Most networks use a cable like the one shown in Figure 2.5. This cable, known in the networking industry as unshielded twisted pair (UTP), usually contains four pairs of wires that can transmit and receive data.

Another key piece of hardware the network uses is a special box-like device called a hub (Figure 2.6), often tucked away in a closet or an equip- ment room. Each system on the network has its own cable that runs to the hub. Think of the hub as being like one of those old-time telephone switch- boards, where operators created connections between persons who called in wanting to reach other telephone users.

Readers with some networking experience know that hubs don’t exist in modern networks, having been replaced with much better devices called switches. But the CompTIA Network+ exam expects you to know what hubs are; plus hubs make this modeling discussion simpler. I’ll get to switches soon enough.

Figure 2.6 • Typical hubFigure 2.5 • UTP cabling

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Layer 1 of the OSI model defines the method of moving data between computers, so the cabling and hubs are part of the Physical layer (Layer 1). Anything that moves data from one system to another, such as copper cabling, fiber optics, even radio waves, is part of the OSI Physical layer. Layer 1 doesn’t care what data goes through; it just moves the data from one system to another sys- tem. Figure 2.7 shows the MHTechEd network in the OSI seven-layer model thus far. Note that each system has the full range of layers, so data from Janelle’s computer can flow to Dana’s computer.

The real magic of a network starts with the net- work interface card, or NIC (pronounced “nick”), which serves as the interface between the PC and the network. While NICs come in a wide array of shapes and sizes, the ones at MHTechEd look like Figure 2.8.

On older systems, a NIC truly was a separate card that snapped into a handy expansion slot, which is why they were called network interface cards. Even though they’re now built into the motherboard, they are still called NICs.

When installed in a PC, the NIC looks like Figure 2.9. Note the cable running from the back of the NIC into the wall; inside that wall is another cable running all the way back to the hub.

Cabling and hubs define the Physical layer of the network, and NICs provide the interface to the PC. Figure 2.10 shows a diagram of the network cabling system. I’ll build on this diagram as I delve deeper into the network process.

You might be tempted to categorize the NIC as part of the Physical layer at this point, and you’d have a valid argument. The NIC clearly is necessary for the physical connection to take place. The CompTIA Network+ exam and many authors put the NIC in OSI Layer 2, the Data Link layer, though, so clearly something else is happening inside the NIC. Let’s take a closer look.

Figure 2.8 • Typical NIC

Figure 2.9 • NIC with cable connecting the PC to the wall jack Figure 2.10 • The MHTechEd network

Dana

Figure 2.7 • The network so far, with the Physical layer hardware installed

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The NIC To understand networks, you must understand how NICs work. The net- work must provide a mechanism that gives each system a unique identi- fier—like a telephone number—so data is delivered to the right system. That’s one of the NIC’s most important jobs. Inside every NIC, burned onto some type of ROM chip, is special firmware containing a unique identifier with a 48-bit value called the media access control address, or MAC address.

No two NICs ever share the same MAC address—ever. Any com- pany that makes NICs must contact the Institute of Electrical and Electronics Engineers (IEEE) and request a block of MAC addresses, which the company then burns into the ROMs on its NICs. Many NIC makers also print the MAC address on the surface of each NIC, as shown in Figure 2.11. Note that the NIC shown here displays the MAC address in hexadecimal notation. Count the number of hex characters—because each hex character represents 4 bits, it takes 12 hex characters to represent 48 bits.

The MAC address in Figure 2.11 is 004005-607D49, although in print, we represent the MAC address as 00–40–05–60–7D–49. The first six digits, in this example 00–40–05, represent the number of the NIC manufacturer. Once the IEEE issues those six hex digits to a manu- facturer—often referred to as the organizationally unique identifier (OUI)—no other manufacturer may use them. The last six digits, in this example 60–7D–49, are the manufacturer’s unique serial number for that NIC; this portion of the MAC is often referred to as the device ID.

Would you like to see the MAC address for your NIC? If you have a Windows system, type ipconfig /all from a command prompt to display the MAC address (Figure 2.12). Note that ipconfig calls the MAC address the physical address, which is an important distinction, as you’ll see a bit later in the chapter.

Figure 2.12 • Output from ipconfig /all

Figure 2.11 • MAC address

MAC-48 and EUI-48 The Institute of Electrical and Electronics Engineers (IEEE) forms MAC addresses from a numbering name space originally called MAC-48, which simply means that the MAC address will be 48 bits, with the first 24 bits defining the OUI, just as described here. The current term for this numbering name space is EUI-48. EUI stands for Extended Unique Identifier. (IEEE apparently went with the new term because they could trademark it.)

Most techs just call them MAC addresses, as you should, but you might see MAC-48 or EUI-48 on the CompTIA Network+ exam.

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Okay, so every NIC in the world has a unique MAC address, but how is it used? Ah, that’s where the fun begins! Recall that computer data is binary, which means it’s made up of streams of ones and zeroes. NICs send and receive this binary data as pulses of electricity, light, or radio waves. The NICs that use electricity to send and receive data are the most common, so let’s consider that type of NIC. The specific process by which a NIC uses electricity to send and receive data is exceedingly complicated but, luckily for you, not necessary to understand. Instead, just think of a charge on the wire as a one and no charge as a zero. A chunk of data moving in pulses across a wire might look something like Figure 2.13.

If you put an oscilloscope on the wire to measure voltage, you’d see something like Figure 2.14. An oscilloscope is a powerful tool that enables you to see electrical pulses.

Now, remembering that the pulses represent binary data, visualize instead a string of ones and zeroes moving across the wire (Figure 2.15).

Once you understand how data moves along the wire, the next question is how does the network get the right data to the right system? All networks transmit data by breaking whatever is moving across

the Physical layer (files, print jobs, Web pages, and so forth) into discrete chunks called frames. A frame is basically a container for a chunk of data moving across a network. The NIC creates and sends, as well as receives and reads, these frames.

I like to visualize an imaginary table inside every NIC that acts as a frame creation and reading station. I see frames as those pneumatic canis- ters you see when you go to a drive-in teller at a bank. A little guy inside the network card—named Nic, naturally!—builds these pneumatic canis- ters (the frames) on the table and then shoots them out on the wire to the hub (Figure 2.16).

Figure 2.16 • Inside the NIC

Figure 2.13 • Data moving along a wire

Figure 2.14 • Oscilloscope of data

Figure 2.15 • Data as ones and zeroes

A number of different frame types are used in different networks. All NICs on the same network must use the same frame type, or they will not be able to communicate with other NICs.

Try This! What’s Your MAC Address?

You can readily determine your MAC address on a Windows computer from the command line. This works in all modern versions of Windows.

In Windows 2000/XP, click Start | Run. Enter 1. the command cmd and press the enter key to get to a command prompt.

In Windows Vista/7, click Start, enter2. cmd in the Start Search text box, and press the enter key to get to a command prompt.

At the command prompt, type the command3. ipconfig /all and press the enter key.

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Here’s where the MAC address becomes important. Figure 2.17 shows a representation of a generic frame. Even though a frame is a string of ones and zeroes, we often draw frames as a series of rectangles, each rectangle representing a part of the string of ones and zeroes. You will see this type of frame repre- sentation used quite often, so you should become comfortable with it (even though I still prefer to see frames as pneumatic canisters). Note that the frame begins with the MAC address of the NIC to which the data is to be sent, followed by the MAC address of the sending NIC. Then comes the data, fol- lowed by a special bit of checking information called the frame check sequence (FCS). The FCS uses a type of binary math called a cyclic redundancy check (CRC) that the receiving NIC uses to verify that the data arrived intact.

So, what’s inside the data part of the frame? You neither know nor care. The data may be a part of a file, a piece of a print job, or part of a Web page. NICs aren’t concerned with content! The NIC simply takes whatever data is passed to it via its device driver and addresses it for the correct system. Special software will take care of what data gets sent and what happens to that data when it arrives. This is the beauty of imagining frames as little pneumatic canisters (Figure 2.18). A canister can carry anything from dirt to diamonds—the NIC doesn’t care one bit (pardon the pun).

Like a canister, a frame can hold only a certain amount of data. Different networks use different sizes of frames, but a single frame holds about 1500 bytes of data.

This raises a new question: what happens when the data to be sent is larger than the frame size? Well, the sending system’s software must chop the data up into nice, frame-sized chunks, which it then hands to the NIC for sending. As the receiving system begins to accept the incoming frames, the receiving system’s software recombines the data chunks as they come in from the network. I’ll show how this disassembling and reassembling is done in a moment—first, let’s see how the frames get to the right system!

When a system sends a frame out on the network, the frame goes into the hub. The hub, in turn, makes an exact copy of that frame, sending a copy of the original frame to every other system on the network. The inter- esting part of this process is when the copy of the frame comes into all the other systems. I like to visualize a frame sliding onto the receiving NIC’s “frame assembly table,” where the electronics of the NIC inspect it. Here’s where the magic takes place: only the NIC to which the frame is addressed will process that frame—the other NICs sim- ply erase it when they see that it is not addressed to their MAC address. This is important to appreciate: every frame sent on a network is received by every NIC, but only the NIC with the match- ing MAC address will process that particular frame (Figure 2.19).

Figure 2.18 • Frame as a canister

Tech Tip

FCS in Depth Most FCSs are only 4 bytes long, yet the average frame carries around 1500 bytes of data. How can 4 bytes tell you if all 1500 bytes in the data are correct? That’s the magic of the math of the CRC. Without going into the grinding details, think of the CRC as just the remainder of a division problem. (Remember learning remainders from division back in elementary school?) The NIC sending the frame does a little math to make the CRC. Using binary arithmetic, it works a division problem on the data using a divisor called a key. The result of this division is the CRC. When the frame gets to the receiving NIC, it divides the data by the same key. If the receiving NIC’s answer is the same as the CRC, it knows the data is good.

Data Sender’s

MAC address Recipient’s

MAC address FCS

Figure 2.17 • Generic frame

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Figure 2.19 • Incoming frame!

Getting the Data on the Line The process of getting data onto the wire and then picking that data off the wire is amazingly complicated. For instance, what happens to keep two NICs from speaking at the same time? Because all the data sent by one NIC is read by every other NIC on the network, only one system may speak at a time. Networks use frames to restrict the amount of data a NIC can send at once, giving all NICs a chance to send data over the network in a reasonable span of time. Dealing with this and many other issues requires sophisti- cated electronics, but the NICs handle these issues completely on their own without our help. Thankfully, the folks who design NICs worry about all these details, so we don’t have to!

Getting to Know You Using the MAC address is a great way to move data around, but this pro- cess raises an important question. How does a sending NIC know the MAC address of the NIC to which it’s sending the data? In most cases, the send- ing system already knows the destination MAC address because the NICs had probably communicated earlier, and each system stores that data. If it doesn’t already know the MAC address, a NIC may send a broadcast onto the network to ask for it. The MAC address of FF-FF-FF-FF-FF-FF is the broadcast address—if a NIC sends a frame using the broadcast address, every single NIC on the network will process that frame. That broadcast frame’s data will contain a request for a system’s MAC address. Without knowing the MAC address to begin with, the requesting computer will use an IP address or host name to pick the target computer out of the crowd. The system with the MAC address your system is seeking will read the request in the broadcast packet and respond with its MAC address.

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The Complete Frame Movement Now that you’ve seen all the pieces used to send and receive frames, let’s put these pieces together and see how a frame gets from one system to another. The basic send/receive process is as follows.

First, the sending system’s network operating system (NOS) software— such as Windows 7—hands some data to its NIC. The NIC builds a frame to transport that data to the receiving NIC (Figure 2.20).

Figure 2.20 • Building the frame

After the NIC creates the frame, it adds the FCS, and then dumps it and the data into the frame (Figure 2.21).

FC S

Figure 2.21 • Adding the data and FCS to the frame

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Next, the NIC puts both the destination MAC address and its own MAC address onto the frame. It waits until no other NIC is using the cable, and then sends the frame through the cable to the network (Figure 2.22).

Figure 2.22 • Sending the frame

The frame propagates down the wire into the hub, which creates copies of the frame and sends it to every other system on the network. Every NIC receives the frame and checks the MAC address. If a NIC finds that a frame is addressed to it, it processes the frame (Figure 2.23); if the frame is not addressed to it, the NIC erases it.

Figure 2.23 • Reading an incoming frame

So, what happens to the data when it gets to the correct NIC? First, the receiving NIC uses the FCS to verify that the data is valid. If it is, the

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receiving NIC strips off all the framing information and sends the data to the software—the network operating system—for processing. The receiv- ing NIC doesn’t care what the software does with the data; its job stops the moment it passes on the data to the software.

Any device that deals with a MAC address is part of the OSI Data Link layer, or Layer 2 of the OSI model. Let’s update the OSI model to include details about the Data Link layer (Figure 2.24).

Figure 2.24 • Layer 1 and Layer 2 are now properly applied to the network.

Note that the cabling and the hub are located in the Physical layer. The NIC is in the Data Link layer, but spans two sublayers.

The Two Aspects of NICs Consider how data moves in and out of a NIC. On one end, frames move into and out of the NIC’s network cable connection. On the other end, data moves back and forth between the NIC and the network operating system software. The many steps a NIC performs to keep this data moving—send- ing and receiving frames over the wire, creating outgoing frames, reading incoming frames, and attaching MAC addresses—are classically broken down into two distinct jobs.

The first job is called the Logical Link Control (LLC). The LLC is the aspect of the NIC that talks to the operating system, places data coming from the software into frames, and creates the CRC on each frame. The LLC is also responsible for dealing with incoming frames: processing those that are addressed to this NIC and erasing frames addressed to other machines on the network.

The second job is called the Media Access Control (MAC), and I bet you can guess what it does! That’s right—it remembers the NIC’s own MAC address and attaches MAC addresses to the frames. Recall that each frame the LLC creates must include both the sender’s and recipient’s MAC addresses. The MAC also ensures that the frames, now complete with their MAC addresses, are then sent along the network cabling. Figure 2.25 shows the Data Link layer in detail.

The CompTIA Network+ exam tests you on the details of the OSI seven-layer model, so remember that the Data Link layer is the only layer that has any sublayers.

The Data Link layer provides a service called Data Link Control (DLC). The only reason to mention this is there’s an ancient printing protocol with the same name. DLC might show up as an incorrect answer on the exam.

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Figure 2.25 • LLC and MAC, the two parts of the Data Link layer

Tech Tip

NIC and Layers Most networking materials that describe the OSI seven-layer model put NICs squarely into the Data Link layer of the model. It’s at the MAC sublayer, after all, that data gets encapsulated into a frame, destination and source MAC addresses get added to that frame, and error checking occurs. What bothers most students with placing NICs solely in the Data Link layer is the obvious other duty of the NIC—putting the ones and zeroes on the network cable. How much more physical can you get?

Many teachers will finesse this issue by defining the Physical layer in its logical sense—that it defines the rules for the ones and zeroes—and then ignore the fact that the data sent on the cable has to come from something. The first question when you hear a statement like that—at least to me—is, “What component does the sending?” It’s the NIC, of course, the only device capable of sending and receiving the physical signal.

Network cards, therefore, operate at both Layer 2 and Layer 1 of the OSI seven-layer model. If cornered to answer one or the other, however, go with the more common answer, Layer 2.

Beyond the Single Wire—Network ■■ Software and Layers 3–7

Getting data from one system to another in a simple network (defined as one in which all the computers connect to one hub) takes relatively little effort on the part of the NICs. But one problem with simple networks is that computers need to broadcast to get MAC addresses. It works for small networks, but what happens when the network gets big, like the size of the

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entire Internet? Can you imagine millions of computers all broadcasting? No data could get through.

Equally important, data flows over the Internet using many technolo- gies, not just Ethernet. These technologies, such as SONET, ATM, and oth- ers, don’t know what to do with Ethernet MAC addresses. When networks get large, you can’t use the MAC addresses anymore.

Large networks need a logical addressing method, like a postal code or telephone numbering scheme, that ignores the hardware and enables you to break up the entire large network into smaller networks called subnets. Figure 2.26 shows two ways to set up a network. On the left, all the com- puters connect to a single hub. On the right, however, the LAN is separated into two five-computer subnets.

Figure 2.26 • Large LAN complete (left) and broken up into two subnets (right)

To move past the physical MAC addresses and start using logical addressing requires some special software called a network protocol. Net- work protocols exist in every operating system. A network protocol not only has to create unique identifiers for each system, but also must create a set of communication rules for issues like how to handle data chopped up into multiple packets and how to ensure those packets get from one subnet to another. Let’s take a moment to learn a bit about the most famous network protocol—TCP/IP—and its unique universal addressing system.

To be accurate, TCP/IP is really several network protocols designed to work together—but two protocols, TCP and IP, do so much work that the folks who invented all these protocols named the whole thing TCP/IP. TCP stands for Transmission Control Protocol, and IP stands for Internet Protocol. IP is the network protocol I need to discuss first; rest assured, however, I’ll cover TCP in plenty of detail later.

MAC addresses are also known as physical addresses.

TCP/IP dominates the networking universe. Almost every network in existence uses TCP/IP. Because it is more specific, a simpler model called the TCP/IP model was created to describe it. You’ll learn all about this model later in the chapter.

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IP—Playing on Layer 3, the Network Layer At the Network layer, Layer 3, packets get created and addressed so they can go from one network to another. The Internet Protocol is the primary logical addressing protocol for TCP/IP. IP makes sure that a piece of data gets to where it needs to go on the network. It does this by giving each device on the network a unique numeric identifier called an IP address. An IP address is known as a logical address to distinguish it from the physical address, the MAC address of the NIC.

Every network protocol uses some type of naming convention, but no two protocols use the same convention. IP uses a rather unique dotted decimal notation (sometimes referred to as a dotted-octet numbering sys- tem) based on four 8-bit numbers. Each 8-bit number ranges from 0 to 255, and the four numbers are separated by periods. (If you don’t see how 8-bit numbers can range from 0 to 255, don’t worry—by the end of this book, you’ll understand these naming conventions in more detail than you ever believed possible!) A typical IP address might look like this:

192.168.4.232

No two systems on the same network share the same IP address; if two machines accidentally receive the same address, they won’t be able to send or receive data. These IP addresses don’t just magically appear—they must be configured by the end user (or the network administrator).

Take a look at Figure 2.26. What makes logical addressing powerful is the magic box—called a router—that connects each of the subnets. Routers use the IP address, not the MAC address, to forward data. This enables networks to connect across data lines that don’t use Ethernet, like the tele- phone network. Each network type (such as Ethernet, SONET, ATM, and others that we’ll discuss later in the book) uses a unique frame. Figure 2.27 shows a typical router.

Figure 2.27 • Typical small router

Try to avoid using redundant expressions. Even though many techs will say “IP protocol,” for example, you know that “IP” stands for “Internet Protocol.” It wouldn’t be right to say “Internet Protocol protocol” in English, so it doesn’t work in network speak either.

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What’s important here is for you to appreciate that in a TCP/IP net- work, each system has two unique identifiers: the MAC address and the IP address. The MAC address (the physical address) is literally burned into the chips on the NIC, whereas the IP address (the logical address) is simply stored in the system’s software. MAC addresses come with the NIC, so you don’t configure MAC addresses, whereas you must configure IP addresses using software. Figure 2.28 shows the MHTechEd network diagram again; this time with the MAC and IP addresses displayed for each system.

Figure 2.28 • MHTechEd addressing

Packets Within Frames For a TCP/IP network to send data successfully, the data must be wrapped up in two distinct containers. A frame of some type enables the data to move from one device to another. Inside that frame is both an IP-specific container that enables routers to determine where to send data—regardless of the physical connection type—and the data itself. In TCP/IP, that inner container is called a packet.

Figure 2.29 shows a typical IP packet; notice the similarity to the frames you saw earlier.

Destination IP address

Source IP address

Data

Figure 2.29 • IP packet

This is a highly simplified IP packet. I am not including lots of little parts of the IP packet in this diagram because they are not important to what you need to understand right now—but don’t worry, you’ll see them later in the book!

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But IP packets don’t leave their PC home without any clothes on! Each IP packet is handed to the NIC, which then encloses the IP packet in a regular frame, creating, in essence, a packet within a frame. I like to visualize the packet as an envelope, with the envelope in the pneu- matic canister frame (Figure 2.30). A more conventional drawing would look like Figure 2.31.

When you send data from one com- puter to another on a TCP/IP network such as the Internet, that data can go through many routers before it reaches its destination. Each router strips off the incoming frame, determines where to send the data according to the IP address in the packet, creates a new frame, and then sends the packet within a frame on its merry way. The new frame type will be the appropriate technology for what- ever connection technology connects to the next router. That could be a cable or DSL network connection, for example (Figure 2.32). The IP packet, on the other hand, remains unchanged.

Once the packet reaches the destination subnet’s router, that router will strip off the incoming frame—no matter what type—look at the destination IP address, and then add a frame with the appropriate destination MAC address that matches the destination IP address.

Frame Header

Packet Header FCS

Data

Packet

Frame

Figure 2.31 • IP packet in a frame

Keep in mind that not all networks are Ethernet networks. Ethernet may dominate, but IP packets fit in all sorts of other connectivity options. For example, cable modems use a type of frame called DOCSIS. T1 lines use a frame called DS1. The beauty of IP packets is that they can travel unchanged in each of these and many others. For more about these technologies, check out Chapter 14.

Figure 2.30 • IP packet in a frame (as a canister)

Frame stripped

Incoming frame

New frame added

New frame out

Figure 2.32 • Router removing network frame and adding one for the outgoing connection

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The receiving NIC strips away the Ethernet frame and passes the remaining packet off to the software. The networking software built into your operating system handles all the rest of the work. The NIC’s driver software is the interconnection between the hardware and the software. The NIC driver knows how to communicate with the NIC to send and receive frames, but it can’t do anything with the packet. Instead, the NIC driver hands the packet off to other programs that know how to deal with all the separate packets and turn them into Web pages, e-mail messages, files, and so forth.

The Network layer (Layer 3) is the last layer that deals directly with hardware. All the other layers of the OSI seven-layer model work strictly within software.

Assembly and Disassembly—Layer 4, the Transport Layer Because most chunks of data are much larger than a single packet, they must be chopped up before they can be sent across a network. When a serv- ing computer receives a request for some data, it must be able to chop the requested data into chunks that will fit into a packet (and eventually into the NIC’s frame), organize the packets for the benefit of the receiving sys- tem, and hand them to the NIC for sending. The receiving system must be able to recognize a series of incoming packets as one data transmission, reassemble the packets correctly based on information included in the packets by the sending system, and verify that all the packets for that piece of data arrived in good shape.

This part is relatively simple—the transport protocol breaks up the data into packets and gives each packet some type of sequence number. I like to compare this process to the one that my favorite international shipping company uses. I receive boxes from UPS almost every day; in fact, some days I receive many, many boxes from UPS. To make sure I get all the boxes for one shipment, UPS puts a numbering system, like the one shown in Figure 2.33, on the label of each box. A computer sending data on a network does the same thing. Embedded into the data of each packet is a sequencing number. By reading the sequencing numbers, the receiving system knows both the total number of packets and how to put them back together.

Figure 2.33 • Labeling the boxes

I’m using the term “packets” here to refer to a generic container. Because the OSI model can be applied to many different network protocols, the terminology for this container changes. Almost all protocols split up data at the Transport layer and add sequencing numbers so the receiving computer can put them together in logical order. What happens at that point depends on the protocol suite. In TCP/IP, for example, the precisely named IP packet is created at the Network layer and other container types are created at the Transport layer.

I’ll go into a lot more detail on this in the TCP/IP model section later in this book. That model, rather than the OSI model, makes more sense for TCP/IP network descriptions.

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The MHTechEd network just keeps getting more and more complex, doesn’t it? And the Word document still hasn’t been copied, has it? Don’t worry; you’re almost there—just a few more pieces to go!

Layer 4, the Transport layer of the OSI seven-layer model, has a big job: it’s the assembler/disassembler software. As part of its job, the Transport layer also initializes requests for packets that weren’t received in good order (Figure 2.34).

Figure 2.34 • OSI updated

Talking on a Network—Layer 5, the Session Layer

Now that you understand that the system uses software to assemble and disassemble data packets, what’s next? In a network, any one system may be talking to many other systems at any given moment. For example, Janelle’s PC has a printer used by all the MHTechEd systems, so there’s a better than average chance that, as Dana tries to access the Word document, another sys- tem will be sending a print job to Janelle’s PC (Figure 2.35).

Janelle’s system must direct these incoming files, print jobs, Web pages, and so on, to the right pro- grams (Figure 2.36). Additionally, the operating system must enable one system to make a connection to another system to verify that the other system can handle whatever

A lot of things happen on a TCP/IP network at the Transport layer. I’m simplifying here because the TCP/IP model does a way better job explaining each thing than does the OSI model.

Figure 2.35 • Handling multiple inputs

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operation the initiating system wants to perform. If Bill’s system wants to send a print job to Janelle’s printer, it first contacts Janelle’s system to ensure that it is ready to handle the print job. The session software handles this part of networking, connecting applications to applications.

Figure 2.36 • Each request becomes a session.

Layer 5, the Session layer of the OSI seven-layer model, handles all the sessions for a system (Figure 2.37). The Session layer initiates sessions, accepts incoming sessions, and opens and closes existing sessions. The Session layer also keeps track of computer naming conventions, such as calling your computer SYSTEM01 or some other type of name that makes more sense than an IP or MAC address.

Figure 2.37 • OSI updated

Try This! See Your Sessions

How many sessions does a typical system have run- ning at one time? Well, if you have a TCP/IP network (and who doesn’t these days), you can run the netstat program from a command prompt to see all of them. Open a com- mand prompt and type the following:

netstat -a

Then press the enter key to see your sessions. Don’t worry about trying to inter- pret what you see—Chapter 9 covers netstat in detail. For now, simply appreciate that each line in the netstat output is a session. Count them!

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Standardized Formats, or Why Layer 6, Presentation, Has No Friends One of the most powerful aspects of a network lies in the fact that it works with (almost) any operating system. Today’s networks easily connect, for

example, a Macintosh system to a Windows PC, despite the fact that these different operating sys- tems use different formats for many types of data. Different data formats used to drive us crazy back in the days before word processors (like Micro- soft Word) could import or export a thousand other word processor formats (Figure 2.38).

This issue motivated folks to create stan- dardized formats that anyone—at least with the right program—could read from any type of computer. Specialized file formats, such as Adobe’s popular Portable Document Format (PDF) for documents and PostScript for print- ing, provide standard formats that any system, regardless of operating system, can read, write, and edit ( Figure 2.39).

Figure 2.39 • Everyone recognizes PDF files!

Layer 6, the Presentation layer of the OSI seven-layer model, handles the conversion of data into formats that are readable by the system. Of all the OSI layers, the high level of file format standardization has made the Presentation layer the least important and least used (Figure 2.40).

Figure 2.38 • Different data formats were often unreadable between systems.

Tech Tip

Acrobat as Open Standard Adobe released the PDF standard to ISO in 2007 and PDF became the ISO 32000 open standard. Adobe Reader remains the premier application for reading PDF documents. Note that Adobe seems to be phasing out the Acrobat branding of PDF documents, but many techs still call PDF “Adobe Acrobat format.”

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Figure 2.40 • OSI updated

Network Applications—Layer 7, the Application Layer The last and most visible part of any network is the software applications that use it. If you want to copy a file residing on another system in your net- work, you need an application like Network in Windows 7 (or My Network Places in earlier versions of Windows) that enables you to access files on remote systems. If you want to view Web pages, you need a Web browser like Internet Explorer or Mozilla Firefox. The people who use a network experience it through an application. A user who knows nothing about all the other parts of a network may still know how to open an e-mail applica- tion to retrieve mail (Figure 2.41).

Figure 2.41 • Network applications at work

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Applications may include a number of additional functions, such as encryption, user authentication, and tools to control the look of the data. But these functions are specific to the given applications. In other words, if you want to put a password on your Word document, you must use the password functions in Word to do so.

The Application layer is Layer 7 in the OSI seven-layer model. Keep in mind that the Application layer doesn’t refer to the applications themselves. It refers to the code built into all operating systems that enables network- aware applications. All operating systems have Application Programming Interfaces (APIs) that programmers can use to make their programs network aware (Figure 2.42). An API, in general, provides a standard way for pro- grammers to enhance or extend an application’s capabilities.

Figure 2.42 • OSI updated

The TCP/IP Model■■ The OSI model was developed as a reaction to a world of hundreds, if not thousands, of different protocols made by different manufacturers that needed to play together. The ISO declared the OSI seven-layer model as the tool for manufacturers of networking equipment to find common ground between multiple protocols, enabling them to create standards for interop- erability of networking software and hardware.

The OSI model is extremely popular and very well-known to all net- working techs. Today’s world, however, is a TCP/IP world. The complexity of the OSI model doesn’t make sense in a world with one protocol suite. Given its dominance, the aptly named TCP/IP model shares equal popular- ity with the venerable OSI model.

The TCP/IP model consists of four layers:

Application ■

Transport ■

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Chapter 2: Network Models 33

Internet ■

Link/Network Interface ■

It’s important to appreciate that the TCP/IP model doesn’t have a standards body to define the layers. Because of this, there are a surprising number of variations on the TCP/IP model.

A great example of this lack of standardization is the Link layer. Without a standardizing body, we can’t even agree on the name. While “Link layer” is extremely common, the term “Network Interface layer” is equally popular. A good tech knows both of these terms and understands that they are interchangeable. Notice also that, unlike the OSI model, the TCP/IP model does not identify each layer with a number.

CompTIA has chosen one popular version of the TCP/IP model for the CompTIA Network+ competencies and exam. That’s the version you’ll learn right here. It’s concise, having only four layers, and many important companies, like Cisco and Microsoft, use it, although with a few varia- tions in names as just described. The TCP/IP model gives each protocol in the TCP/IP protocol suite a clear home in one of the four layers.

The clarity of the TCP/IP model shows the flaws in the OSI model. The OSI model couldn’t perfectly describe all the TCP/IP protocols. In fact, the OSI model couldn’t perfectly describe any of the now defunct alternative protocols, such as IPX/SPX and NetBIOS/NetBEUI. Network nerds have gotten into fistfights over a particular protocol’s exact location in the OSI model.

The TCP/IP model fixes this ambiguity, at least for TCP/IP. Because of its tight protocol-to-layer integration, the TCP/IP model is a descriptive model, whereas the OSI seven-layer model is a prescriptive model.

The Link Layer The TCP/IP model lumps together the OSI model’s Layer 1 and Layer 2 into a single layer called the Link layer (or Network Interface layer), as seen in Figure 2.43. It’s not that the Physical and Data Link layers are unimportant to TCP/IP, but the TCP/ IP protocol suite really begins at Layer 3 of the OSI model. In essence, TCP/IP techs count on other techs to handle the physical connections in their networks. All of the pieces that you learned in the OSI model (cabling, hubs, physical addresses, and NICs) sit squarely in the Link layer.

A nice way to separate layers in the TCP/IP model is to think about packets and frames. Any part of the network that deals with complete frames is in the Link layer. The moment the frame information is stripped away from an IP packet, we move out of the Link layer and into the Internet layer.

Transport

Internet

Link

Transport

Session

Presentation Application

Application

Network

Data Link

Physical

Figure 2.43 • TCP/IP Link layer compared to OSI Layers 1 and 2

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The Internet Layer The Internet layer should really be called the “IP packet” layer (Figure 2.44). Any device or protocol that deals with pure IP packets—getting an IP packet to its destination—sits in the Internet layer. IP addressing itself is also part of the Internet layer, as are routers and the magic they perform to get IP packets to the next router. IP packets are created at this layer.

The Internet layer doesn’t care about the type of data an IP packet carries, nor does it care whether the data gets there in good order or not. Those jobs are for the next layer: the Transport layer.

The Transport Layer The Transport layer combines features of the OSI Transport and Session layers with a dash of Appli- cation layer just for flavor (Figure 2.45). While the TCP/IP model is certainly involved with the assem- bly and disassembly of data, it also defines other functions, such as connection-oriented and connec- tionless communication.

Connection-Oriented vs. Connectionless Communication Some protocols, like the popular Post Office Protocol (POP) used for sending e-mail messages, require that the e-mail client and server verify that they have a good connection before a message is sent (Figure 2.46). This makes sense because you don’t want your e-mail message to be a corrupted mess when it arrives.

Figure 2.46 • Connection between e-mail client and server

Application

Transport

Link

Internet

Session

Transport

Application

Presentation

Data Link

Physical

Network

Figure 2.44 • TCP/IP Internet layer compared to OSI Layer 3

Transport

Session

Application

Link

Transport

Application

Presentation

Data Link

Physical

Network Internet

Figure 2.45 • TCP/IP Transport layer compared to OSI Layers 4, 5, and part of 7

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Alternatively, a number of TCP/IP protocols simply send data without first waiting to verify that the receiving system is ready (Figure 2.47). When using Voice over IP (VoIP), for example, the call is made without verifying first whether another device is there.

Figure 2.47 • Connectionless communication

The connection-oriented protocol is called Transmission Control Protocol (TCP). The connectionless protocol is called User Datagram Protocol (UDP).

Everything you can do on the Internet, from Web browsing to Skype phone calls to playing World of Warcraft, is predetermined to be either connection-oriented or connectionless. It’s simply a matter of knowing your applications.

Segments Within Packets To see the Transport layer in action, strip away the IP addresses from an IP packet. What’s left is a chunk of data in yet another container called a TCP segment. TCP segments have many other fields that ensure the data gets to its destination in good order. These fields have names such as Checksum, Flags, and Acknowledgement. Chapter 7 goes into more detail on TCP seg- ments, but, for now, just know that TCP segments have fields that ensure the connection-oriented communication works properly. Figure 2.48 shows a typical (although simplified) TCP segment.

Destination port

Source port

Sequence number

Checksum Flags Acknowledgement Data

Figure 2.48 • TCP segment

Data comes from the Application layer applications. The Transport layer breaks that data into chunks, adding port numbers and sequence numbers, creating the TCP segment. The Transport layer then hands the TCP segment to the Internet layer that, in turn, creates the IP packet.

Most traffic on a TCP/IP network uses TCP at the Transport layer, but like Yoda said, “There is another,” and that’s UDP. UDP also gets data from

Chapter 7 covers TCP, UDP, and all sorts of other protocols in detail.

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the Application layer programs and adds port and sequencing numbers to create a container called a UDP datagram. A UDP datagram lacks most of the extra fields found in TCP segments, simply because UDP doesn’t care if the receiving computer gets its data. Figure 2.49 shows a UDP datagram.

Destination port

Source port

Sequence number

Checksum Data

Figure 2.49 • UDP datagram

The Application Layer The TCP/IP Application layer combines features of the top three layers of the OSI model (Figure 2.50). Every application, especially connection- oriented applications, must know how to initiate, control, and disconnect from a remote system. No single method exists for doing this. Each TCP/IP application uses its own method.

Transport

Internet

Link

Transport

Session

Presentation Application

Application

Network

Data Link

Physical

Figure 2.50 • TCP/IP Application layer compared to OSI layers 5–7

TCP/IP uses a unique port numbering system that gives each applica- tion a unique number between 1 and 65535. Some of these port numbers are very famous. The protocol that makes Web pages work, HTTP, uses port 80, for example.

Although we can say that the OSI model’s Presentation layer fits inside the TCP/IP model’s Application layer, no application requires any particu- lar form of presentation as seen in the OSI model. Standard formats are part and parcel with TCP/IP protocols. For example, all e-mail messages use an extremely strict format called MIME. All e-mail servers and clients read MIME without exception.

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In the OSI model, we describe the API—the smarts that make applica- tions network-aware—as being part of the Application layer. While this is still true for the TCP/IP model, all applications designed for TCP/IP are, by definition, network-aware. There is no such thing as a “TCP/IP word pro- cessor” or a “TCP/IP image editor” that requires the added ability to know how to talk to a network—all TCP/IP applications can talk to the network, as long as they are part of a network. And every TCP/IP application must be a part of a network to function: Web browsers, e-mail clients, multiplayer games, and so on.

Don’t think that the TCP/IP model is any simpler than the OSI model just because it only uses four layers. With the arguable exception of the Pre- sentation layer, everything you saw in the OSI model is also found in the TCP/IP model (Figure 2.51).

Transport

Internet

Link

Transport

Session

Presentation Application

Application

Network

Data Link

Physical

I work at the Application layer.

And, not surprisingly, the other Application

layer.

I work on both of the Transport layers.

Figure 2.51 • OSI model and TCP/IP model side by side

Frames, Packets, and Segments, Oh My! The TCP/IP model shows its power in its ability to describe what happens at each layer to the data that goes from one computer to another. The Application layer programs create the data. The Transport layer breaks the data into chunks, putting those chunks into TCP segments or UDP datagrams. The Internet layer adds the IP addressing and creates the IP packets. The Link layer wraps the IP packet into a frame, with the MAC address information and a frame check sequence (FCS). Now the data is ready to hit the wire (or airwaves, if you’re in a café). Figure 2-52 shows all this encapsulating goodness relative to the TCP/IP model.

Application data

Segment/ datagram

Packet

FrameIP Packet

Segment

Header Data

Data

Header

Header

Figure 2.52 • Data encapsulation in TCP/IP

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For the exam, remember at what layer each encapsulation happens. Table 2.1 shows the layers and the corresponding data structure.

Table 2.1 TCP/IP Model Layers and Corresponding Data Structures TCP/IP Model Layer Data Structure

Link Frame

Internet IP packet

Transport TCP segment/UDP datagram Application (The data starts and ends here)

The Tech’s Troubleshooting Tool The OSI seven-layer model and TCP/IP model provide you with a way to conceptualize a network to determine what could cause a specific prob- lem when the inevitable problems occur. Good techs always use a model to troubleshoot their networks.

If Jane can’t print to the networked printer, for example, a model can help solve the problem. If her NIC shows activity, then, using the OSI model, you can set aside both the Physical layer (Layer 1) and Data Link layer (Layer 2). If you’re a TCP/IP model tech, you can look at the same symptoms and eliminate the Link layer. In either case, you’ll find yourself moving up the layer ladder to the OSI model’s Network layer (Layer 3) or the TCP/IP model’s Internet layer. If her computer has a proper IP address, then you can set that layer aside too, and you can move on up to check other layers to solve the problem.

Understanding both the OSI and TCP/IP models is important. Sure, they’re on the CompTIA Network+ exam, but more importantly, they are your primary diagnostic tool for troubleshooting networks and a commu- nication tool for talking to your fellow techs.

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Chapter 2 Review■■

Chapter Summary ■

After reading this chapter and completing the exercises, you should understand the following about networking.

Describe how models such as the OSI seven-layer model and the TCP/IP model help technicians understand and troubleshoot networks

Modeling is critical to the networking world. You ■ use models to understand and communicate with other techs about networks.

All models are a simplified representation of the ■ real thing. The human model ignores the many different types of body shapes, using only a single “optimal” figure. The model airplane lacks functional engines or the internal framework, and the computerized weather model might disregard subtle differences in wind temperatures or geology.

In the early days of networking, different ■ manufacturers made unique types of networks that functioned fairly well. But each network had its own cabling, hardware, drivers, naming conventions, applications, and many other unique features. To interconnect networks and improve networking as a whole, someone needed to create a guide—a model that described the functions of a network—so people who made hardware and software could work together to make networks that worked together well.

The OSI seven-layer model defines the role played ■ by each protocol. The OSI model also provides a common jargon that network techs can use to describe the function of any network protocol.

The TCP/IP four-layer model applies only to ■ networks that use the TCP/IP protocol suite, such as the Internet.

Explain the major functions of networks with the OSI seven-layer model.

OSI Layer 1, the Physical layer, includes anything ■ that moves data from one system to another, such as cabling or radio waves.

OSI Layer 2, the Data Link layer, defines the rules ■ for accessing and using the Physical layer. The

Data Link layer is divided into two sublayers: Media Access Control (MAC) and Logical Link Control (LLC).

The MAC sublayer controls access to the Physical ■ layer, or shared media. It encapsulates (creates the frames for) data sent from the system, adding source and destination MAC addresses and error-checking information; it also decapsulates (removes the MAC addresses and CRC from) data received by the system.

The LLC sublayer provides an interface with ■ the Network layer protocols. It is responsible for the ordered delivery of frames, including retransmission of missing or corrupt packets, and for flow control (moderating data flow so one system doesn’t overwhelm the other). Any device that deals with a MAC address is part of the Data Link layer.

OSI Layer 3, the Network layer, is the last layer to ■ work directly with hardware. It adds the unique identifiers (such as IP addresses) to the packets that enable routers to make sure the packets get to the correct system without worrying about the type of hardware used for transmission. Anything having to do with logical addressing works at the Network layer.

A network protocol creates unique identifiers ■ for each system and also creates a set of communication rules for issues such as how to handle data chopped up into multiple packets and how to make sure those packets get from one subnet to another.

OSI Layer 4, the Transport layer, breaks up data ■ received from the upper layers into smaller pieces for transport and adds sequencing numbers to make sure the receiving computer can reassemble the data properly.

Session software at OSI Layer 5 handles the ■ process of differentiating between various types of connections on a PC. The Session layer initiates sessions, accepts incoming sessions, and opens and closes existing sessions. You can use the netstat program to view existing sessions.

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OSI Layer 6, the Presentation layer, presents ■ data from the sending system in a form that the applications on the receiving system can understand. Standardized data formats, such as PDF, enable computers running on different platforms to share data across a network; the result is that the Presentation layer is the least important and least used of the seven layers.

OSI Layer 7, the Application layer, defines a set of ■ tools that programs can use to access the network. Application layer programs provide services to the programs that the users see.

Describe the major functions of networks with the TCP/IP model

The TCP/IP Link layer (or Network Interface ■ layer) covers the first two layers of the OSI model—the physical components like hubs and cables as well as network frames.

The TCP/IP Internet layer works just like the OSI ■ model’s Network layer. Anything involved with IP, including packets, addressing, and routing, happens at this layer.

The TCP/IP Transport layer is similar to the OSI ■ model’s Transport layer, except that the TCP/ IP version differentiates between connection- oriented communication and connectionless communication.

In TCP/IP, the Transport layer takes data from ■ the applications, splits the data into chunks called TCP segments or UDP datagrams, depending on the protocol used, and adds port and sequence numbers. The segments and datagrams get handed down to the Internet layer for IP to further encapsulate the data.

The TCP/IP Application layer combines the top ■ three layers of the OSI model into one super layer. The session component works similarly to the OSI model’s Session layer. There is no presentation component that compares to the OSI model’s Presentation layer, however. The TCP/IP Application layer is like the OSI model’s version, except that TCP/IP connectivity is implied and not a separate program or function.

Key Terms ■

Application layer (32) broadcast address (18) cyclic redundancy check (CRC) (17) Data Link layer (21) device ID (15) frame (16) frame check sequence (FCS) (17) hub (13) Internet layer (34) Internet Protocol (23, 24) IP address (24) Link layer (33) logical address (24) Logical Link Control (LLC) (21) MAC address (15) Media Access Control (MAC) (21) network interface card (14) Network Interface layer (33) Network layer, Layer 3 (24) network protocol (23)

NIC (14) Open Systems Interconnection (OSI) seven-layer

model (8) organizationally unique identifier (OUI) (15) packet (25) physical address (15) Physical layer (14) Presentation layer (30) protocols (11) router (24) Session layer (29) session software (29) subnets (23) TCP segment (35) Transmission Control Protocol (TCP) (23) Transmission Control Protocol/Internet Protocol

(TCP/IP) model (8) Transport layer (28) UDP datagram (36) unshielded twisted pair (UTP) (13) User Datagram Protocol (UDP) (35)

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41 Chapter 2: Network Models

Key Term Quiz ■

Use the Key Terms list to complete the sentences that follow. Not all terms will be used.

The _______________ is an example of software 1. that creates packets for moving data across networks.

Most often, the _______________ provides the 2. physical connection between the PC and the network.

Using the _______________ enables a computer 3. to send a packet that every other PC on the network will process.

You can connect two very different networks by 4. using a(n) _______________.

Every NIC has a hard-coded identifier called a(n) 5. _______________.

The _______________ provides an excellent tool 6. for conceptualizing how a TCP/IP network works. (Select the best answer.)

On a sending machine, data gets broken up 7. at the _______________ of the OSI seven-layer model.

NICs encapsulate data into a(n) _______________ 8. for sending that data over a network.

A(n) _______________ enables multiple machines 9. to connect over a network.

The _______________ provides the key interface 10. between the Physical and Network layers.

Multiple-Choice Quiz ■

Which of the following OSI layers converts the 1. ones and zeroes to electrical signals and places these signals on the cable?

Physical layerA.

Transport layerB.

Network layerC.

Data Link layerD.

The term “unshielded twisted pair” describes 2. which of the following network components?

CableA.

HubB.

RouterC.

NICD.

From the options that follow, select the one 3. that best describes the contents of a typical (simplified) network frame.

Sender’s MAC address, recipient’s MAC A. address, data, FCS

Recipient’s MAC address, sender’s MAC B. address, data, FCS

Recipient’s IP address, sender’s IP address, C. data, FCS

Recipient’s e-mail address, sender’s e-mail D. address, data, FCS

Which of the following is most likely to be a 4. MAC address assigned to a NIC?

192.168.1.121A.

24.17.232.7BB.

23.4F.17.8A.4C.10C.

713.555.1212D.

Which layer of the TCP/IP model involves 5. routing?

Link layerA.

Transport layerB.

Internet layerC.

Application layerD.

How much data can a typical frame contain?6.

500 bytesA.

1500 bytesB.

1500 kilobytesC.

1 megabyteD.

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Which of the following best describes an IP 7. address?

A unique dotted decimal notation burned A. into every NIC

A unique 48-bit identifying number burned B. into every NIC

A dotted decimal notation assigned to a NIC C. by software

A 48-bit identifying number assigned to a D. NIC by software

Which layer of the OSI model makes sure the 8. data is in a readable format for the Application layer?

Application layerA.

Presentation layerB.

Session layerC.

Transport layerD.

At which layer of the TCP/IP model are UDP 9. datagrams created?

Link/Network InterfaceA.

InternetB.

TransportC.

ApplicationD.

Which protocol creates the final IP packet?10.

NICA.

IPB.

TCPC.

UDPD.

Which TCP/IP layer includes Layers 5–7 from 11. the OSI seven-layer model?

Application layerA.

Transport layerB.

Internet layerC.

Link layerD.

What component of Layer 2 of the OSI seven-12. layer model is responsible for the ordered delivery of frames, including retransmission of missing or corrupt packets?

MAC sublayerA.

LLC sublayerB.

CRC sublayerC.

Data Link sublayerD.

Which components work at Layer 1 of the OSI 13. seven-layer model? (Select two.)

CablesA.

HubB.

Network protocolC.

Session softwareD.

Andalyn says complete 48-bit MAC addresses 14. are allocated to NIC manufacturers from the IEEE. Buster says the IEEE only assigns the first 24 bits to manufacturers. Carlos says the IEEE assigns only the last 24 bits to manufacturers. Who is correct?

Only Andalyn is correct.A.

Only Buster is correct.B.

Only Carlos is correct.C.

No one is correct.D.

If a sending system does not know the MAC 15. address of the intended recipient system, it sends a broadcast frame with what MAC address?

192.168.0.0A.

FF-FF-FF-FF-FF-FFB.

11-11-11-11-11-11C.

00-00-00-00-00-00D.

Essay Quiz ■ Some new techs at your office are confused by 1. the differences between a NIC’s frame and an IP packet. Write a short essay describing the two encapsulations, including the components that do the encapsulating.

Your boss has received a set of files with the file 2. extension .WP and is worried because he’s never seen that extension before. He wants people to have access to the information in those files from anywhere in the network. Write a short memo describing how Microsoft Word can handle these files, including a discussion of how that fits with the OSI seven-layer model.

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43 Chapter 2: Network Models

Lab Projects

Lab Project 2.1 •

Examine your classroom network. What components does it have? How would you classify those components according to the OSI seven-layer model?

Lab Projects

Lab Project 2.2 •

Create a mnemonic phrase to help you remember the OSI seven-layer model. With two layers beginning with the letter P, how will you differentiate in your mnemonic between Presentation and Physical? How will you incorporate the two sublayers of the Data Link layer?

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3 chapter Cabling and Topology

“It’s from someone who says

she’s a fan of my work on low-

dimensional topology. And she’s

a fan of my . . . hair.”

—Charlie eppes, Numb3rs

In this chapter, you will learn how to

Explain the different types of ■■ network topologies

Describe the different types of ■■ network cabling

Describe the IEEE networking ■■ standards

Every network must provide some method to get data from one system to another. In most cases, this method consists of some type of cabling (usually copper or fiber-optic) running between systems, although many

networks skip wires and use wireless methods to move data. Stringing those

cables brings up a number of critical issues you need to understand to work on a

network. How do all these cables connect the computers? Does every computer

on the network run a cable to a central point? Does a single cable snake through

the ceiling, with all the computers on the network connected to it? These

questions need answering! Furthermore, manufacturers need standards so they

can make networking equipment that works well together. While we’re talking

about standards, what about the cabling itself? What type of cable? What

quality of copper? How thick should it be? Who defines the standards for cables

so they all work in the network?

This chapter answers these questions in three parts. First, you will learn

about network topology—the way that cables and other pieces of hardware

connect to one another. Second, you will tour the most common standardized

cable types used in networking. Third, you will discover the IEEE committees

that create network technology standards.

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Chapter 3: Cabling and Topology 45

Test Specific

Topology■■ Computer networks employ many different topologies, or ways of connect- ing computers together. This section looks at both the historical topologies— bus, ring, and star—and the modern topologies—hybrid, mesh, point-to- multipoint, and point-to-point.

Bus and Ring The first generation of wired networks used one of two topologies, both shown in Figure 3.1. A bus topology uses a single cable that con- nects all of the computers in a line. A ring topology connects all computers on the network with a ring of cable.

Note that topologies are diagrams, much like an electrical circuit diagram. Real network cabling doesn’t go in perfect circles or perfect straight lines. Figure 3.2 shows a bus topology network that illustrates how the cable might appear in the real world.

Data flows differently between bus and ring networks, creating different problems and solutions. In bus topol- ogy networks, data from each computer simply goes out on the whole bus. A network using a bus topology needs termination at each end of the cable to prevent a signal sent from one com- puter from reflecting at the ends of the cable, quickly bringing the network down (Figure 3.3).

Figure 3.1 • Bus and ring topologies

Figure 3.2 • Real-world bus topology

Figure 3.3 • Terminated bus topology

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In a ring topology network, in contrast, data traffic moves in a circle from one computer to the next in the same direction (Figure 3.4). With no end to the cable, ring networks require no termination.

Bus and ring topology networks work well but suffer from the same problem: the entire network stops working if the cable breaks at any point. The broken ends on a bus topology network aren’t terminated, causing reflection between computers that are still connected. A break in a ring topology network simply breaks the circuit, stopping the data flow ( Figure 3.5).

Figure 3.4 • Ring topology moving in a certain direction Figure 3.5 • Nobody is talking!

Star The star topology uses a central connection box for all the computers on the network (Figure 3.6). Star topol- ogy has a huge benefit over ring and bus topologies by offering fault tolerance—if one of the cables breaks, all of the other computers can still communicate. Bus and ring topology networks were popular and inex- pensive to implement, however, so the old-style star topology networks weren’t very successful. Network hardware designers couldn’t easily redesign their existing networks to use a star topology.

Figure 3.6 • Star topology

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Hybrids Even though network designers couldn’t easily use a star topology, the benefits of star topologies were overwhelming, motivating smart people to come up with a way to use star topologies without requiring a major redesign—and the way they did so was ingenious. The ring topology net- work designers struck first by taking the entire ring and shrinking it into a small box, as shown in Figure 3.7.

This was quickly followed by the bus topology folks who, in turn, shrunk their bus (better known as the segment) into their own box ( Figure 3.8).

Figure 3.7 • Shrinking the ring

The most successful of the star ring topology networks was called Token Ring, manufactured by IBM.

Figure 3.8 • Shrinking the segment

Physically, they looked like a star, but if you examined it as an electronic schematic, the signals acted like a ring or a bus. Clearly the old definition of topology needed a little clarification. When we talk about topology today, we separate how the cables physically look (the physical topology) from how the signals travel electronically (the signaling topology or logical topology).

Any form of networking technology that combines a physical topology with a signaling topology is called a hybrid topology. Hybrid topologies have come and gone since the earliest days of networking. Only two hybrid topologies, star-ring topology and star-bus topology, ever saw any amount of popularity. Eventually star-ring lost market share, and star-bus reigned as the undisputed king of topologies.

Mesh and Point-to-Multipoint Topologies aren’t just for wired networks. Wireless networks also need topologies to get data from one machine to another, but using radio waves instead of cables involves somewhat different topologies. Almost all wire- less networks use one of two different topologies: a mesh topology or a point-to-multipoint topology (Figure 3.9).

Most techs refer to the signaling topology as the logical topology today. That’s how you’ll see it on the CompTIA Network+ exam as well.

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Figure 3.9 • Mesh and point-to-multipoint topologies

Mesh In a mesh topology network, every computer connects to every other com- puter via two or more routes. Some of the routes between two computers may require traversing through another member of the mesh network.

There are two types of meshed topologies: partially meshed and fully meshed (Figure 3.10). In a partially meshed topology network, at least two machines have redundant connections. Every machine doesn’t have to con- nect to every other machine. In a fully meshed topology network, every com- puter connects directly to every other computer.

Figure 3.10 • Partially and fully meshed topologies

If you’re looking at Figure 3.10 and thinking that a mesh topology looks amazingly resilient and robust, it is—at least on paper. Because every

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Chapter 3: Cabling and Topology 49

computer connects to every other computer on the fully meshed network, even if half the PCs crash, the network still functions as well as ever (for the survivors). In a practical sense, however, implementing a fully meshed topology for a wired network would be an expensive mess. Even a tiny fully meshed network with 10 PCs, for example, would need 45 separate and distinct pieces of cable to connect every PC to every other PC. What a mesh mess! Because of this, mesh topologies have never been practical for a wired network.

Make sure you know the formula to calculate the number of connec- tions needed to create a fully meshed network, given a certain number of computers. Here’s the formula:

y = number of computers

Number of connections = y(y – 1)/2

So, if you have six computers, you need 6(6 – 1)/2 = 30/2 = 15 connections to create a fully meshed network.

Point-to-Multipoint In a point-to-multipoint topology, a single system acts as a common source through which all members of the point-to-multipoint network converse. If you compare a star topology to a slightly rearranged point-to-multipoint topology, you might be tempted to say they’re the same thing. Granted, they’re similar, but look at Figure 3.11. See what’s in the middle? The subtle but important difference is that a point-to-multipoint topology requires an intelligent device in the center, whereas the device in the center of a star topology has little more to do than send or provide a path for a signal down all the connections.

Figure 3.11 • Comparing star and point-to-multipoint topologies

You’ll sometimes find mesh or point-to-multipoint topology used in wired networks, but they’re rare. These two topologies are far more com- monly seen in wireless networks.

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Point-to-Point In a point-to-point topology network, two computers connect directly together with no need for a central device of any kind. You’ll find point-to-point topologies implemented in both wired and wireless networks (Figure 3.12).

Parameters of a Topology Although a topology describes the method by which systems in a network connect, the topology alone doesn’t describe all of the features necessary to enable those networks. The term bus topology, for example, describes a net- work that consists of some number of machines connected to the network via a single linear piece of cable. Notice that this definition leaves a lot of questions unanswered. What is the cable made of? How long can it be? How do the machines decide which machine should send data at a specific moment? A network based on a bus topology can answer these questions in a number of different ways—but it’s not the job of the topology to define issues like these. A functioning network needs a more detailed standard.

Over the years, particular manufacturers and standards bodies have created several specific network technologies based on different topologies. A network technology is a practical application of a topology and other criti- cal technologies that provides a method to get data from one computer to another on a network. These network technologies have names like 10BaseT, 1000BaseF, and 10GBaseLX. You will learn all about these in the next two chapters.

Cabling■■ The majority of networked systems link together using some type of cabling. Different types of networks over the years have used a number of different types of cables—and you need to learn about all these cables to succeed on the CompTIA Network+ exam! This section explores both the cabling types used in older networks and those found in today’s networks.

All cables used in the networking industry can be categorized in three distinct groups: coaxial (coax), twisted pair, and fiber-optic. Let’s look at all three.

Coaxial Cable Coaxial cable contains a central conductor wire surrounded by an insulating material, which, in turn, is surrounded by a braided metal shield. The cable is referred to as coaxial (coax for short) because the center wire and the braided metal shield share a common axis or centerline (Figure 3.13).

Coaxial cable shields data transmissions from electromag- netic interference (EMI). Many devices in the typical office environment generate magnetic fields, including lights, fans,

Figure 3.12 • Point-to-point topology

Make sure you know all your topologies: bus, ring, star, hybrid, mesh, point-to- multipoint, and point-to-point.

Figure 3.13 • Cutaway view of coaxial cable

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Chapter 3: Cabling and Topology 51

copy machines, and refrigerators. When a metal wire encounters these magnetic fields, electrical current is generated along the wire. This extra current—EMI—can shut down a network because it is easily misinterpreted as a signal by devices like NICs. To prevent EMI from affecting the network, the outer mesh layer of a coaxial cable shields the center wire (on which the data is transmitted) from interference (Figure 3.14).

Early bus topology networks used coaxial cable to connect computers together. Back in the day, the most popular cable used special bayonet-style connectors called BNC connectors (Figure 3.15). Even earlier bus networks used thick cable that required vampire connections—sometimes called vampire taps—that literally pierced the cable.

Figure 3.14 • Coaxial cable showing braided metal shielding

Figure 3.15 • BNC connector on coaxial cable

You’ll find coaxial cable used today primarily to enable a cable modem to connect to an Internet service provider (ISP). Connecting a computer to the cable modem enables that computer to access the Internet. This cable is the same type used to connect televisions to cable boxes or to satellite receivers. These cables use an F-connector that screws on, making for a secure connec- tion (Figure 3.16).

Figure 3.16 • F-type connector on coaxial cable

Coaxial cabling is also very popular with satellite, over-the- air antennas, and even some home video devices. This book covers cable and other Internet connectivity options in great detail in Chapter 14.

Tech Tip

What’s in a Name? Techs all around the globe argue over the meaning of BNC. A solid percentage says with authority that it stands for “British Naval Connector.” An opposing percentage says with equal authority that it stands for “Bayonet Neill-Concelman,” after the stick-and-twist style of connecting and the purported inventors of the connector. The jury is still out, though this week I’m leaning toward Neill and Concelman and their bayonet- style connector.

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Cable modems connect using either RG-6 or, rarely, RG-59. RG-59 was used primarily for cable television rather than networking. Its thinness and the introduction of digital cable motivated the move to the more robust RG-6, the predominant cabling used today (Figure 3.17).

All coax cables have a Radio Grade (RG) rating. The U.S. military devel- oped these ratings to provide a quick reference for the different types of coax. The only important measure of coax cabling is its Ohm rating, a relative measure of the resistance (or more precisely, characteristic impedance) on the cable. You may run across other coax cables that don’t have acceptable Ohm ratings, although they look just like network-rated coax. Fortunately, most coax cable types display their Ohm ratings on the cables themselves (see Figure 3.18). Both RG-6 and RG-59 cables are rated at 75 Ohms.

The Ohm rating of a particular piece of cable describes the impedance of that cable. Impedance describes a set of characteristics that define how much a cable resists the flow of electricity. This isn’t simple resistance, though. Impedance also factors in things like how long it takes the wire to get a full charge—the wire’s capacitance—and more.

Figure 3.17 • RG-6 cable Figure 3.18 • Ohm rating (on an older, RG-58 cable used for networking)

Given the popularity of cable for television and Internet in homes today, you’ll run into situations where people need to take a single coaxial cable and split it. Coaxial handles this quite nicely with coaxial splitters like the one shown in Figure 3.19. You can also connect two coaxial cables together easily using a barrel connector when you need to add some distance to a connection (Figure 3.20).

Figure 3.19 • Coaxial splitter Figure 3.20 • Barrel connector

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Twisted Pair The most common type of cabling used in networks consists of twisted pairs of cables, bundled together into a common jacket. Twisted-pair cabling for networks is composed of multiple pairs of wires, twisted around each other at specific intervals. The twists reduce interference, called crosstalk: the more twists, the less crosstalk. Networks use two types of twisted-pair cabling: shielded twisted pair and unshielded twisted pair.

Shielded Twisted Pair Shielded twisted pair (STP), as its name implies, consists of twisted pairs of wires surrounded by shielding to protect them from EMI. STP is pretty rare, primarily because there’s so little need for STP’s shielding. The shielding only really matters in locations with excessive electronic noise, such as a shop floor with lots of lights, electric motors, or other machin- ery that could cause problems for other cables. Figure 3.21 shows the most common STP type: the venerable IBM Type 1 cable used in Token Ring network technology.

Unshielded Twisted Pair Unshielded twisted pair (UTP) is by far the most common type of network cabling used today. UTP consists of twisted pairs of wires surrounded by a plastic jacket (Figure 3.22). This jacket does not provide any protection from EMI, so when install- ing UTP cabling, you must be careful to avoid interference from fluorescent lights, motors, and so forth. UTP costs much less than STP but, in most cases, performs just as well.

Although more sensitive to interference than coaxial or STP cable, UTP cabling provides an inexpensive and flexible means to cable networks. UTP cable isn’t exclusive to networks. Many other technologies (such as telephone systems) employ the same cabling. This makes working with UTP a bit of a challenge. Imagine going up into a ceil- ing and seeing two sets of UTP cables: how would you determine which is for the telephones and which is for the network? Not to worry—a number of installation standards and tools exist to help those who work with UTP answer these types of questions.

Have you ever picked up a telephone and heard a distinct crackling noise? That’s an example of crosstalk.

Figure 3.21 • Shielded twisted pair

Figure 3.22 • Unshielded twisted pair

Cross Check OSI Seven-Layer and TCP/IP Model

You’ve seen UTP cabling before when Dana accessed documents on Janelle’s PC at MHTechEd. Refer to Chapter 2, and cross-check your memory. At what layer of the OSI seven-layer model would you put UTP cabling? For that matter, at what layer would you put network topology? How about on the TCP/IP model?

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Not all UTP cables are the same! UTP cabling has a number of varia- tions, such as the number of twists per foot. To help network installers get the right cable for the right network technology, the cabling industry has developed a variety of grades called category (CAT) ratings. CAT ratings are officially rated in megahertz (MHz), indicating the highest frequency the cable can handle. Table 3.1 shows the most common categories along with their status with the TIA/EIA (see the Tech Tip for more information).

Table 3.1 CAT Ratings for UTP CAT Rating Max Frequency Max Bandwidth Status with TIA/EIA

CAT 1 < 1 MHz Analog phone lines only

No longer recognized

CAT 2 4 MHz 4 Mbps No longer recognized

CAT 3 16 MHz 16 Mbps Recognized

CAT 4 20 MHz 20 Mbps No longer recognized

CAT 5 100 MHz 100 Mbps No longer recognized

CAT 5e 100 MHz 1000 Mbps Recognized CAT 6 250 MHz 10000 Mbps Recognized

UTP cables are rated to handle a certain frequency or cycles per second, such as 100 MHz or 1000 MHz. You could take the frequency number in the early days of networking and translate that into the maximum throughput for a cable. Each cycle per second (or hertz) basically accounted for one bit of data per second. A 10 million cycle per second (10 MHz) cable, for example, could handle 10 million bits per second (10 Mbps). The maximum amount of data that goes through the cable per second is called the bandwidth.

For current networks, developers have implemented bandwidth-efficient encoding schemes, which means they can squeeze more bits into the same signal as long as the cable can handle it. Thus, the CAT 5e cable can handle a throughput of up to 1000 Mbps, even though it’s rated to handle a fre- quency of only up to 100 MHz.

Because most networks can run at speeds of up to 1000 MHz, most new cabling installations use Category 5e (CAT 5e) cabling, although a large number of installations use CAT 6 to future-proof the network. CAT 5e cabling currently costs much less than CAT 6, although as CAT 6 gains

in popularity, it’s slowly drop- ping in price.

Make sure you can look at UTP and know its CAT rating. There are two places to look. First, UTP is typically sold in boxed reels, and the manufacturer will clearly mark the CAT level on the box (Figure 3.23). Second, look on the cable itself. The category level of a piece of cable is usually printed on the cable (Figure 3.24).

The CompTIA Network+ exam is only interested in CAT 3, CAT 5, CAT 5e, and CAT 6 cables.

Tech Tip

Industry Standards Bodies Several international groups set the standards for cabling and networking in general. Ready for alphabet soup? At or near the top is the International Organization for Standardization (ISO). The American National Standards Institute (ANSI) is both the official U.S. representative to the ISO and a major international player. ANSI checks the standards and accredits other groups, such as the Telecommunications Industry Association (TIA) and the Electronic Industries Alliance (EIA). The TIA and EIA together set the standards for UTP cabling, among many other things.

Try This! Shopping Spree!

Just how common has CAT 6 become in your neighborhood? Take a run down to your local hardware store or office supply store and shop for UTP cabling. Do they carry CAT 6? CAT 5? CAT 7? What’s the dif- ference in price? If it’s not much more expensive to go with the better cable, the expected shift in networking standards has occurred and you might want to upgrade your network.

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Anyone who’s plugged in a telephone has probably already dealt with the registered jack (RJ) connectors used with UTP cable. Telephones use RJ-11 connectors, designed to support up to two pairs of wires. Networks use the four-pair RJ-45 connectors (Figure 3.25).

Fiber-Optic Fiber-optic cable transmits light rather than electricity, making it attractive for both high-EMI areas and long-distance transmissions. Whereas a sin- gle copper cable cannot carry data more than a few hundred meters at best, a single piece of fiber-optic cabling will operate, depending on the implementation, for distances of up to tens of kilometers. A fiber-optic cable has four components: the glass fiber itself (the core); the cladding, which is the part that makes the light reflect down the fiber; buffer material to give strength, and the insulating jacket (Figure 3.26).

Fiber-optic cabling is manufactured with many different diameters of core and cladding. In a convenient bit of standardization, cable manufacturers use a two- number designator to define fiber-optic cables according to their core and cladding measurements. The most common fiber-optic cable size is 62.5/125 µm. Almost all network technologies that use fiber-optic cable require

Figure 3.23 • CAT level marked on box of UTP

Figure 3.24 • CAT level on UTP

Figure 3.25 • RJ-11 (left) and RJ-45 (right) connectors

Figure 3.26 • Cross section of fiber-optic cabling

Tech Tip

CAT 6a If you have a need for speed, the latest finalized update to the venerable UTP cable is Category 6a. This update doubles the bandwidth of CAT 6 to 500 MHz to accommodate 10-Gbps speeds up to 100 meters. Take that, fiber! (The 100-meter limitation, by the way, refers to the Ethernet standard, the major implementation of UTP in the networking world. Chapter 4 covers Ethernet in great detail.)

Other standards are in the works, however, so by the time you read this paragraph, CAT 6a might be old news. CAT 7 (600 MHz), CAT 7a (1000 MHz), and CAT 8 (1200 MHz) are just around the corner.

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pairs of fibers. One fiber is used for sending, the other for receiving. In response to the demand for two-pair cabling, manufacturers often con- nect two fibers together like a lamp cord to create the popular duplex fiber-optic cabling (Figure 3.27).

Fiber cables are pretty tiny! Light can be sent down a fiber-optic cable as regular light or as laser light. The two types of light require totally different fiber-optic cables. Most network technologies that use fiber optics use LEDs (light emitting diodes) to send light signals. A fiber-optic cable that uses LEDs is known as multimode fiber (MMF).

A fiber-optic cable that uses lasers is known as single- mode fiber (SMF). Using laser light and single-mode fiber- optic cables prevents a problem unique to multimode fiber optics called modal distortion (signals sent at the same time don’t arrive at the same time because the paths differ slightly in length) and enables a network to achieve phenomenally high transfer rates over incredibly long distances.

Fiber optics also define the wavelength of light used, measured in nanometers (nm). Almost all multimode cables transmit 850-nm wavelengths, whereas single-mode trans- mits either 1310 or 1550 nm, depending on the laser.

Fiber-optic cables come in a broad choice of connector types. There are over one hundred different connectors, but the three you need to know for the CompTIA Net- work+ exam are ST, SC, and LC (Figure 3.28). LC is unique because it is a duplex connector, designed to accept two fiber cables.

Figure 3.28 • From left to right: ST, SC, and LC fiber-optic connectors

Other Cables Fiber-optic and UTP make up almost all network cabling, but a few other types of cabling may serve from time to time as alternatives to these two: the ancient serial and parallel cables from the earliest days of PCs and the modern high-speed serial connection, better known as FireWire. These cables are only used with quick-and-dirty temporary connections, but they do work, so they bear at least a quick mention.

For those of you unfamiliar with it, the odd little u-shaped symbol describing fiber cable size (µ) stands for micro, or 1/1,000,000.

Figure 3.27 • Duplex fiber-optic cable

Tech Tip

What’s in a Name? Most technicians call common fiber-optic connectors by their initials—such as ST, SC, or LC—perhaps because there’s no consensus about what words go with those initials. ST probably stands for straight tip, although some call it snap twist. But SC and LC? How about subscriber connector, standard connector, or Siemon connector for the former, and local connector or Lucent connector for the latter?

If you want to remember the connectors for the exam, try these: stick and twist for the bayonet- style ST connectors; stick and click for the straight push-in SC connectors; and little connector for the . . . little . . . LC connector.

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Chapter 3: Cabling and Topology 57

Classic Serial Serial cabling predates both networking and the personal com- puter. RS-232, the recommended standard (RS) upon which all serial communication takes place on your PC, dates from 1969 and hasn’t substantially changed in around 40 years. When IBM invented the PC way back in 1980, serial connections were just about the only standard input/output technology available, so IBM included two serial ports on every PC. The most common serial port is a 9-pin, male D-subminiature (or DB-9) connector, as shown in Figure 3.29.

Serial ports offer a poor option for networking, with very slow data rates—only about 56,000 bps—and only point-to-point con- nections. In all probability, copying something on a flash drive and just walking over to the other system is faster, but serial network- ing does work if needed. Serial ports are quickly fading away, however, and you no longer see them on new PCs.

Parallel Parallel connections are as ancient as serial ports. Parallel can run up to around 2 Mbps, although when used for networking, they tend to be much slower. Parallel is also limited to point-to-point topology but uses a 25-pin female—rather than male—DB type connector (Figure 3.30). The IEEE 1284 committee sets the standards for parallel communication. (See the section “Networking Industry Standards—IEEE,” later in this chapter.)

FireWire FireWire (based on the IEEE 1394 standard) is the only viable alternative cabling option to fiber-optic or UTP. FireWire is also restricted to point-to- point connections, but it’s very fast (currently the standard is up to 800 Mbps). FireWire has its own unique connector (Figure 3.31).

Figure 3.31 • FireWire connector

Figure 3.29 • Serial port

Figure 3.30 • Parallel connector

Concentrate on UTP—that’s where the hardest CompTIA Network+ exam questions come into play. Don’t forget to give coax, STP, and fiber-optic a quick pass, and make sure you understand the reasons for picking one type of cabling over another. Even though the CompTIA Network+ exam does not test too hard on cabling, this is important information that you will use in the real networking world.

You cannot network computers using FireWire in Windows Vista or Windows 7.

Mike Meyers’ CompTIA Network+ Guide to Managing and Troubleshooting Networks 58

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Fire Ratings Did you ever see the movie The Towering Inferno? Don’t worry if you missed it—The Towering Inferno was one of the better disaster movies of the 1970s, although it was no Airplane! Anyway, Steve McQueen stars as the fireman who saves the day when a skyscraper goes up in flames because of poor-quality electrical cabling. The burning insulation on the wires ultimately spreads the fire to every part of the building. Although no cables made today contain truly flammable insulation, the insulation is made from plastic, and if you get any plastic hot enough, it will create smoke and noxious fumes. The risk of burning insulation isn’t fire—it’s smoke and fumes.

To reduce the risk of your network cables burning and creating nox- ious fumes and smoke, Underwriters Laboratories and the National Elec- trical Code (NEC) joined forces to develop cabling fire ratings. The two most common fire ratings are PVC and plenum. Cable with a polyvinyl chloride (PVC) rating has no significant fire protection. If you burn a PVC cable, it creates lots of smoke and noxious fumes. Burning plenum-rated cable creates much less smoke and fumes, but plenum-rated cable—often referred to simply as “plenum”—costs about three to five times as much as PVC-rated cable. Most city ordinances require the use of plenum cable for network installations. The bottom line? Get plenum!

The space between the acoustical tile ceiling in an office building and the actual concrete ceiling above is called the plenum—hence the name for the proper fire rating of cabling to use in that space. A third type of fire rating, known as riser, designates the proper cabling to use for vertical runs between floors of a building. Riser-rated cable provides less protec- tion than plenum cable, though, so most installations today use plenum for runs between floors.

Networking Industry ■■ Standards—IEEE

The Institute of Electrical and Electronics Engineers (IEEE) defines industry- wide standards that promote the use and implementation of technol- ogy. In February 1980, a new committee called the 802 Working Group took over from the private sector the job of defining network standards. The IEEE 802 committee defines frames, speeds, distances, and types of cabling to use in a network environment. Concentrating on cables, the IEEE recognizes that no single cabling solution can work in all situations and, therefore, provides a variety of cabling standards.

IEEE committees define standards for a wide variety of electronics. The names of these committees are often used to refer to the standards they publish. The IEEE 1284 committee, for example, sets standards for parallel communication. Have you ever seen a printer cable marked “IEEE

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Chapter 3: Cabling and Topology 59

1284–compliant,” as in Figure 3.32? This means the manufacturer followed the rules set by the IEEE 1284 committee. Another committee you may have heard of is the IEEE 1394 committee, which controls the FireWire standard.

The IEEE 802 committee sets the standards for net- working. Although the original plan was to define a single, universal standard for networking, it quickly became apparent that no single solution would work for all needs. The 802 committee split into smaller subcommittees, with names such as IEEE 802.3 and IEEE 802.5. Table 3.2 shows the currently recog- nized IEEE 802 subcommittees and their areas of jurisdiction. I’ve included the inactive subcommittees for reference. The missing numbers, such as 802.4 and 802.12, were used for committees long-ago disbanded. Each sub- committee is officially called a Working Group, except the few listed as a Technical Advisory Group (TAG) in the table.

Some of these committees deal with technologies that didn’t quite make it, and the committees associated with those standards, such as IEEE 802.4, Token Bus, have become dormant. When preparing for the CompTIA Network+ exam, concentrate on the IEEE 802.3 and 802.11 stan- dards. You will see these again in later chapters.

Table 3.2 IEEE 802 Subcommittees IEEE 802 LAN/MAN Overview & Architecture

IEEE 802.1 Higher Layer LAN Protocols

802.1s Multiple Spanning Trees

802.1 Rapid Reconfiguration of Spanning Tree

802.1x Port Based Network Access Control

IEEE 802.2 Logical Link Control (LLC); now inactive

IEEE 802.3 Ethernet

802.3ae 10 Gigabit Ethernet

IEEE 802.5 Token Ring; now inactive

IEEE 802.11 Wireless LAN (WLAN); specifications, such as Wi-Fi

IEEE 802.15 Wireless Personal Area Network (WPAN)

IEEE 802.16 Broadband Wireless Access (BWA); specifications for implementing Wireless Metropolitan Area Networks (Wireless MANs); referred to also as WiMAX

IEEE 802.17 Resilient Packet Ring (RPR)

IEEE 802.18 Radio Regulatory Technical Advisory Group

IEEE 802.19 Coexistence Technical Advisory Group

IEEE 802.20 Mobile Broadband Wireless Access (MBWA)

IEEE 802.21 Media Independent Handover IEEE 802.22 Wireless Regional Area Networks

Memorize the 802.3 and 802.11 standards. Ignore the rest.

Fire Ratings Did you ever see the movie The Towering Inferno? Don’t worry if you missed it—The Towering Inferno was one of the better disaster movies of the 1970s, although it was no Airplane! Anyway, Steve McQueen stars as the fireman who saves the day when a skyscraper goes up in flames because of poor-quality electrical cabling. The burning insulation on the wires ultimately spreads the fire to every part of the building. Although no cables made today contain truly flammable insulation, the insulation is made from plastic, and if you get any plastic hot enough, it will create smoke and noxious fumes. The risk of burning insulation isn’t fire—it’s smoke and fumes.

To reduce the risk of your network cables burning and creating nox- ious fumes and smoke, Underwriters Laboratories and the National Elec- trical Code (NEC) joined forces to develop cabling fire ratings. The two most common fire ratings are PVC and plenum. Cable with a polyvinyl chloride (PVC) rating has no significant fire protection. If you burn a PVC cable, it creates lots of smoke and noxious fumes. Burning plenum-rated cable creates much less smoke and fumes, but plenum-rated cable—often referred to simply as “plenum”—costs about three to five times as much as PVC-rated cable. Most city ordinances require the use of plenum cable for network installations. The bottom line? Get plenum!

The space between the acoustical tile ceiling in an office building and the actual concrete ceiling above is called the plenum—hence the name for the proper fire rating of cabling to use in that space. A third type of fire rating, known as riser, designates the proper cabling to use for vertical runs between floors of a building. Riser-rated cable provides less protec- tion than plenum cable, though, so most installations today use plenum for runs between floors.

Networking Industry ■■ Standards—IEEE

The Institute of Electrical and Electronics Engineers (IEEE) defines industry- wide standards that promote the use and implementation of technol- ogy. In February 1980, a new committee called the 802 Working Group took over from the private sector the job of defining network standards. The IEEE 802 committee defines frames, speeds, distances, and types of cabling to use in a network environment. Concentrating on cables, the IEEE recognizes that no single cabling solution can work in all situations and, therefore, provides a variety of cabling standards.

IEEE committees define standards for a wide variety of electronics. The names of these committees are often used to refer to the standards they publish. The IEEE 1284 committee, for example, sets standards for parallel communication. Have you ever seen a printer cable marked “IEEE

Figure 3.32 • Parallel cable marked IEEE 1284–compliant

60 Mike Meyers’ CompTIA Network+ Guide to Managing and Troubleshooting Networks

/ Mike Meyers’ CompTIA Network+ Guide to Managing and Troubleshooting Networks, Third Edition / Meyers / 911-1 / Chapter 3

Chapter 3 Review■■

Chapter Summary ■

After reading this chapter and completing the exer- cises, you should understand the following about cabling and topology.

Explain the different types of network topologies

A network’s ■ topology describes how computers connect to each other in that network. The most common network topologies are called bus, ring, star, and mesh.

In a bus topology, all computers connect to ■ the network via a main line. The cable must be terminated at both ends to prevent signal reflections.

In a ring topology, all computers on the network ■ attach to a ring of cable. A single break in the cable stops the flow of data through the entire network.

In a star topology, the computers on the network ■ connect to a central wiring point, which provides fault tolerance.

Modern networks use one of two hybrid ■ topologies: star-bus or star-ring. Star-bus is overwhelmingly the most common topology used today.

In a mesh topology, each computer has a ■ dedicated line to every other computer. Mesh networks can be further categorized as partially meshed or fully meshed, both of which require a significant amount of physical cable. Network techs are able to determine the amount of cable segments needed with a mathematical formula.

In a point-to-multipoint topology, a single ■ system acts as a common source through which all members of the network converse.

Mesh and point-to-multipoint topologies are ■ common among wireless networks.

In a point-to-point topology, two computers ■ connect directly together.

Describe the different types of network cabling

Coaxial cable, or coax, shields data transmissions ■ from EMI. Coax was widely used in early bus networks and used BNC connectors. Today, coax is used mainly to connect a cable modem to an ISP.

Coax cables have an RG rating, with RG-6 being ■ the predominant coax today.

Twisted pair, which comes shielded or ■ unshielded, is the most common type of networking cable today. UTP is less expensive and more popular than STP, though it doesn’t offer any protection from EMI.

UTP is categorized by its CAT rating, with ■ CAT 5, CAT 5e, and CAT 6 being the most commonly used today.

Telephones use RJ-11 connectors, whereas UTP ■ uses RJ-45 connectors.

Fiber-optic cabling transmits light instead of the ■ electricity used in CAT cable or coax. It is thin and more expensive, yet less flexible and more delicate, than other types of network cabling.

There are two types of fiber-optic cable based ■ on what type of light is used. LEDs require multimode cable, whereas lasers generally require single-mode cable.

All fiber-optic cable has three parts: the fiber ■ itself; the cladding, which covers the fiber and helps it reflect down the fiber; and the outer insulating jacket. Additionally, there are over one hundred types of connectors for fiber-optic cable, but ST, SC, and LC are the most common for computer networking.

Plenum-rated UTP is required by most cities for ■ network installations.

Serial cables adhering to the RS-232 standard ■ and parallel cables adhering to the IEEE-1284 standard may be used to network two computers

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61 Chapter 3: Cabling and Topology

directly together. You can also use IEEE 1394 (FireWire) connections for direct connection, although not with Windows Vista or Windows 7.

Describe the IEEE networking standards

Networking standards are established and ■ promoted by the Institute of Electrical and Electronics Engineers (IEEE).

The IEEE 802 committee defines frames, ■ speeds, distances, and types of cabling to use in networks. IEEE 802 is split into several subcommittees, including IEEE 802.3 and IEEE 802.11.

The IEEE 1284 committee defines the standards ■ for parallel communications, whereas the IEEE 1394 committee defines the standards for FireWire High-Performance Serial Bus.

Key Terms ■

bandwidth (54) BNC connectors (51) bus topology (45) category (CAT) ratings (54) cladding (55) coaxial cable (50) core (55) crosstalk (53) electromagnetic interference (EMI) (50) fault tolerance (46) fiber-optic cable (55) fully meshed topology (48) hybrid topology (47) IEEE 1284 (57) IEEE 1394 (57) Institute of Electrical and Electronics Engineers

(IEEE) (58) insulating jacket (55) logical topology (47) mesh topology (48) modal distortion (56) multimode fiber (MMF) (56)

network topology (44) Ohm rating (52) partially meshed topology (48) physical topology (47) plenum (58) point-to-multipoint topology (49) point-to-point topology (50) polyvinyl chloride (PVC) (58) Radio Grade (RG) rating (52) ring topology (45) riser (58) RJ-11 (55) RJ-45 (55) RS-232 (57) segment (47) shielded twisted pair (STP) (53) signaling topology (47) single-mode fiber (SMF) (56) star-bus topology (47) star-ring topology (47) star topology (46) unshielded twisted pair (UTP) (53)

Key Term Quiz ■ Use the Key Terms list to complete the sentences that follow. Not all terms will be used.

The _______________ is a network topology that 1. relies on a main line of network coaxial cabling.

The _______________ of a cable will determine 2. its speed.

A(n) _______________ provides more fault 3. tolerance than any other basic network topology.

When your network has all computers connected 4. to a centrally located wiring closet, you have a physical _______________ network.

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_______________ networks use more than one 5. type of basic network topology.

CAT 5e cable is a type of _______________ 6. wiring.

Coaxial cable uses a braided metal shield to 7. protect data from _______________.

Network cabling can use either light or electricity 8. to transmit data. The faster of these types uses light along _______________.

_______________-grade UTP must be installed 9. in ceilings, whereas _______________-grade UTP is often used to connect one floor to another vertically in a building.

The twisting of the cables in UTP and STP 10. reduces _______________.

Multiple-Choice Quiz ■

Which of the following are standard network 1. topologies? (Select three.)

BusA.

StarB.

RingC.

Dual-ringD.

John was carrying on at the water cooler the 2. other day, trying to show off his knowledge of networking. He claimed that the company had installed special cabling to handle the problems of crosstalk on the network. What kind of cabling did the company install?

CoaxialA.

Shielded coaxialB.

Unshielded twisted pairC.

Fiber-opticD.

Jill needs to run some UTP cable from one 3. office to another. She found a box of cable in the closet and wants to make sure it’s CAT 5 or better. How can she tell the CAT level of the cable? (Select two.)

Check the box.A.

Scan for markings on the cable.B.

Check the color of the cable—gray means C. CAT 5, yellow means CAT 6e, and so on.

Check the ends of the cable.D.

What topology provides the most fault 4. tolerance?

BusA.

RingB.

Star-busC.

MeshD.

What organization is responsible for 5. establishing and promoting networking standards?

Institute of Electrical and Electronics A. Engineers (IEEE)

International Networking Standards B. Organization (INSO)

Federal Communications Commission C. (FCC)

International Telecommunications D. Association (ITA)

What aspects of network cabling do the IEEE 6. committees establish? (Select three.)

Frame sizeA.

SpeedB.

Color of sheathingC.

Cable typesD.

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63 Chapter 3: Cabling and Topology

What types of coax cabling have been used in 7. computer networking? (Select three.)

RG-8A.

RG-45B.

RG-58C.

RG-62D.

What applications are best suited for fiber-8. optic cabling? (Select two.)

Short distancesA.

Wireless networksB.

High-EMI areasC.

Long distancesD.

What are the main components of fiber-optic 9. cabling? (Select three.)

CladdingA.

Insulating jacketB.

Copper coreC.

FiberD.

What is the most popular size fiber-optic 10. cabling?

62.5/125 µmA.

125/62.5 µmB.

50/125 µmC.

125/50 µmD.

Most fiber-optic installations use LEDs to send 11. light signals and are known as what?

Single-modeA.

MultimodeB.

Complex modeC.

Duplex modeD.

Why must the main cable in a bus topology be 12. terminated at both ends?

To allow the signal to be amplified so it can A. reach both ends of the network

To prevent the signal from dropping off the B. network before reaching all computers

To prevent the signal from bouncing back C. and forth

To convert the signal to the proper format D. for a bus network

Where are you most likely to encounter a mesh 13. network?

On any network using fiber-optic cableA.

On any network using plenum cableB.

On wireless networksC.

On wired networksD.

You are asked by your boss to research 14. upgrading all the network cable in your office building. The building manager requires the safest possible cabling type in case of fire, and your boss wants to future- proof the network so cabling doesn’t need to be replaced when network technologies faster than 1 Gbps are available. You decide to use CAT 5e plenum cabling throughout the building. Which objective have you satisfied?

Neither the building manager’s nor your A. boss’s requirements have been met.

Only the building manager’s requirement B. has been met.

Only your boss’s requirement has C. been met.

Both the building manager’s and your D. boss’s requirements have been met.

Which committee is responsible for wireless 15. networking standards?

IEEE 802.2A.

IEEE 802.3B.

IEEE 802.5C.

IEEE 802.11D.

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Lab Project 3.1 •

Lab ProjectsLab Projects

This lab project requires you to demonstrate knowledge of the four basic network topologies. Obtain four blank pieces of paper. Proceed to draw six boxes on each page to represent six computers—neatness counts!

At the top of each sheet, write one of the following: bus topology, mesh topology, ring topology, or star topology. Then draw lines to represent the physical network cabling required by each network topology.

Lab Project 3.2 •

In your studies of network cabling for the CompTIA Network+ certification exam, you realize you could use a simplified chart to study from and memorize. Build a reference study chart that describes the features of

network cabling. Create your completed chart using a spreadsheet program, or simply a sheet of paper, with the column headings and names shown in the following table. If you wish, you can start by writing your notes here.

Essay Quiz ■ You work in the computer training department 1. at your company. A newly developed mobile training program is being planned. The plan requires setting up five training computers in a particular department you use to train on weekly. Write a short essay that describes which network topology would be quickest to set up and tear down for this type of onsite training.

Your boss has decided to have cable run to 2. every computer in the office, but doesn’t know which type to use. In an effort to help bring the company into the 21st century, write a short

essay comparing the merits of UTP and fiber- optic cabling.

The NICs on your company’s computers all 3. have dual 10-Mbps and 100-Mbps capability, yet users complain that the network is slow. Write a brief essay that explains what could be the cause of the problem.

Your company has hired a group of new 4. network techs, and you’ve been tasked to do their training session on networking standards organizations. Write a brief essay detailing the IEEE and its various committees.

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65 Chapter 3: Cabling and Topology

Cable Type Description Benefits Drawbacks

CAT 5

CAT 5e

CAT 6

Fiber-optic

Lab Project 3.3 •

In this lab project, you will demonstrate knowledge of the different IEEE committees that are most prevalent today. Use the Internet to research each of these subcommittees:

IEEE 802.3, IEEE 802.5, and IEEE 802.11. Give an example of where each type of technology might best be used.

4 chapter

66

/ Mike Meyers’ CompTIA Network+ Guide to Managing and Troubleshooting Networks, Third Edition / Meyers / 911-1 / Chapter 4

Ethernet Basics

“In theory there is no difference

between theory and practice. In

practice there is.”

—Yogi Berra

In this chapter, you will learn how to

Define and describe Ethernet■■

Explain early Ethernet ■■ implementations

Describe ways to extend and ■■ enhance Ethernet networks

In the beginning, there were no networks. Computers were isolated, solitary islands of information in a teeming sea of proto-geeks who used clubs and wore fur pocket protectors. Okay, maybe it wasn’t that bad, but if you wanted to

move a file from one machine to another—and proto-geeks were as much into

that as modern geeks—you had to use Sneakernet, which meant you saved the

file on a disk, laced up your tennis shoes, and hiked over to the other system.

All that walking no doubt produced lots of health benefits, but frankly, proto-

geeks weren’t all that into health benefits—they were into speed, power, and

technological coolness in general. (Sound familiar?) It’s no wonder, then, that

geeks everywhere agreed on the need to replace Sneakernet with a faster and

more efficient method of sharing data. The method they came up with is the

subject of this chapter.

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