数据通信与网络教程（第二版）

PREFACE

xix

CHAPTER 1 INTRODUCTION TO COMMUNICATIONS, STANDARDS, AND PROTOCOLS

1.1 WHY STUDY COMMUNICATIONS

1

A Brief History 1

Applications 4

Issues 8

1.2 COMPUTER NETWORKS

9

Common Bus Topology 10

Star Topology 11

Ring Topology 12

Fully Connected Topology 13

Combined Topologies 13

1.3 STANDARDS AND STANDARDS ORGANIZATIONS

15

The Need for Standards 15

Standards Organizations 16

1.4 OPEn SYSTEMS AND THE OSI MODEL

18

Overview of the Model 22

Connection Strategies 24

Physical Layer 29

Data Link Layer 30

Network Layer 32

Transport Layer 33

Session Layer 36

Presentation Layer 38

Application Layer 40

Intemet Layers 42

Summary 42

1.5 THE FUTURE OF DATA COMMUNICATIONS

44

REVIEW QUESTIONS 51

EXERCISES 52

REFERENCES 53

CHAPTER 2 TRANSMISSION MEDIA AND CODES

2.1 INTRODUCTION

S4

2.2 CONDUCTIVE METAL

57

Twisted Pair 57

Coaxial Cable 59

2.3 OPTICAL FIBER

61

2.4 WIRELESS COMMUNICATIONS

66

Microwave Transmission 67

Satellite Transmission 70

Geosynchronous Satellites 71

Low Earth Orbit Satellites 77

Wireless LANs 81

Bluetooth 82

Free Space Optics 83

Summary 84

2.5 CODES

87

Early Codes 87

ASCII Code 89

EBCDIC Code 92

Unicode 92

2.6 SUMMARY

93

REVIEW QUESTIONS 94

EXERCISES 95

REFERENCES 96

CHAPTER 3 ANALOG AND DIGITAL SIGNALS

3.1 INTRODUCTION

97

3.2 DIGITAL ENCODING SCHEMES

98

NRZ Encoding 98

Manchester Encoding 100

3.3 ANALOG SIGNALS

101

Fourier''s Results 103

Applications of Fourier''s Results 106

3.4 BIT RATE

107

The Nyquist Theorem and Noiseless Channels 107

Noisy Channels 109

Shannon''s Result 110

3.5 DIGITAL-TO-ANALOG CONVERSION

112

Frequency Modulation 113

Amplitude Modulation 114

Phase Modulation 114

Quadrature Amplitude Modulation 115

3.6 ANALOG-TO-DIGITAL CONVERSION

118

Pulse Amplitude Modulation 119

Pulse Code Modulation 119

3.7 MODEMS

121

Signal Constellation 122

Modem Standards 125

Cable Modems 127

3.8 DSL

131

How It Works 132

Different DSL Technologies , 135

ADSL Lite G. Lite, ITU standard ITU G. 992.2

135

SDSL 136

HDSL and HDSL2 136

SHDSL 137

RADSL 137

IDSL 137

VDSL 137

3.9 SUMMARY

138

REVIEW QUESTIONS 139

EXEROSES 141

REFERENCES 143

CHAPTER 4 MAKING CONNECTIONS

144

4.1 INTRODUCTION

144

4.2 COMMUNICATION CARRIERS AND DEVICES

145

The Telephone System 145

Call Routing 147

Private Branch Exchanges 148

Cellular Phones 149

Fax Machines 151

4.3 TRANSMISSION MODES

153

Serial and Parallel Transmission 153

Asynchronous, Synchronous, and Isochronous Transmission 154

Simplex, Half-Duplex, and Full-Duplex Communications 158

4.4 INTERFACE STANDARDS

159

EIA-232 Interface 160

EIA-232 Subsets 162

Null Modems 163

X.21 Interface 164

USB 166

USB Connections 166

Data Transfer 168

USB Packets 170

FireWire 172

Connections 173

Communications 175

Arbitration 176

4.5 MULTIPLEXING

178

Frequency-Division Multiplexing 180

Time-Division Multiplexing 182

Statistical Multiplexers 183

Wave-Division Multiplexing 185

4.6 DIGITAL CARRIERS

186

Tl 186

SONET 188

Device Types 189

Payloads and Frames 191

4.7 CONTENTION PROTOCOLS

195

Aloha Protocols 196

Cartier Sense Multiple Access 199

Collision Detection 202

Collision Avoidance 205

Token Passing 205

Summary of Protocols 207

4.8 SUMMARY

207

RENEW QUESTIONS 210

EXERCISES 212

REFERENCES 214

CHAPTER 5 DATA COMPRESSION

215

5.1 INTRODUCTION

215

5.2 FREQUENCY-DEPENDENT CODES

217

Huffman Code 217

Arithmetic Compression 220

5.3 RUN-LENGTH ENCODING

225

Runs of the Same Bit 225

Runs with Different Characters 226

Facsimile Compression 226

5.4 RELATIVE ENCODING

229

5.5 LEMPEL~ZIV COMPRESSION

229

5.6 IMAGE COMPRESSION

235

Image Representation 235

JPEG Compression 238

DCT Phase 238

Encoding Phase 244

GIF Files 245

5.7 MULTIMEDIA COMPRESSION

246

MPEG 246

MP3 251

5.8 SUMMARY

254

REVIEW QUESTIONS 254

EXERCISES 255

REFERENCES 257

CHAPTER 6 DATA INTEGRITY

258

6.1 INTRODUCTION

258

6.2 SIMPLE ERROR DETECTION TECHNIQUES

259

Parity Checks 259

Analysis of Parity Checking 260

Checksums 261

6.3 CYCLIC REDUNDANCY CHECKS FOR ERROR DETECTION

261

Polynomial Division 262

How CRC Works 263

Analysis of CRC 265

CRC Implementation Using Circular Shifts 268

6.4 HAMMING CODES: ERROR CORRECTION

270

Single-Bit Error Correction 270

Multiple-Bit Error Correction 273

6.5 SUMMARY

274

RENEW QUESTIONS 275

EXERCISES 276

REFERENCES 277

CHAPTER7 DATA SECURITY

279

7.1 INTRODUCTION

279

7.2 ENCRYPTION ALGORITHMS

281

Caesar Cipher 282

Polyalphabetic Cipher 284

Transposition Cipher 284

Bit-Level Ciphering 285

Data Encryption Standards 287

DES 287

Triple DES 291

AES and the Rijndael Algorithm 292

Clipper Chip and the Skipjack Algorithm 296

7.3 KEY DISTRIBUTION AND PROTECTION

299

Shamir''s Method 300

Diffie-Hellman Key Exchange 300

7.4 PUBLIC KEY ENCRYPTION

302

RSA Algorithm 302

Digital Signatures 305

Authentication and Message Digests 308

Pretty Good Privacy 311

7.5 TRANSPORT LAYER SECURITY AND SERVER AUTHENTICATION

315

Transport Layer Security 316

X.509 Certificate 317

Handshakes 320

7.6 FIREWALLS

323

Packet Filtering 324

Application-Level Gateway 325

Stateful Inspection 327

7.7 VIRUSES

329

Infecting Files 330

Memory-Resident Viruses 332

Virus Evolution 333

Virus Sources 335

7.8 THREATS AND ATTACKS

336

The Intemet Worm 336

Computer Hackers 338

Other Threats 339

7.9 SUMMARY

341

RENEW QUESTIONS 345

EXERCISES 346

REFERENCES 348

CHAPTER 8 FLOW CONTROL

350

8.1 INTRODUCTION

350

8.2 SIGNALING

352

DTE-DCE Flow Control 353

X-ON/X-OFF 353

8.3 FRAME-ORIENTED CONTROL

354

Unrestricted Protocol 355

Stop-and-Wait Protocol 356

Protocol Efficiency 358

8.4 GO-BACK-n: A SLIDING WINDOW PROTOCOL

360

Frame Format 362

Features 363

Algorithm 366

8.5 SELECTIVE REPEAT: A SLIDING WINDOW PROTOCOL

370

Features 370

Algorithm 374

8.6 EFFICIENCY OF SLIDING WINDOW PROTOCOLS

377

8.7 PROTOCOL CORRECTNESS

380

Finite State Machines 380

STD for a Simplified Go-Back-n Protocol 381

State Transition Diagram for a Faulty Go-Back-n Protocol 383

Petri Nets 386

8.8 SUMMARY

390

RENEW QUESTIONS 392

EXERCISES 393

REFERENCES 395

CHAPTER 9 LOCAL AREA NETWORKS

396

9.1 INTRODUCTION

396

9.2 DATA LINK CONTROL

398

High-level Data Link Control Protocol 400

Frame Format 402

HDLC Example 405

Binary Synchronous Communications Protocol 408

9.3 ETHERNET: IEEE STANDARD 802.3

410

Concepts 411

Ethernet Frame Format 413

Physical Implementations of 10 Mbps Ethernet 415

9.4 FAST ETHERNET 100 MBPS

417

100BaseTX 418

100BaseFX 421

100BaseT4 422

Collision Domain 424

9.5 GIGABIT ETHERNET

424

MAC Sublayer 425

1000BaseX 427

1000BaseT 428

Beyond Gigabit Rates 430

9.6 TOKEN RING: IEEE STANDARD 802.5

433

Token and Frame Formats 434

Reserving and Claiming Tokens 436

Ring Maintenance 440

9.7 WIRELESS NETWORKS: IEEE STANDARD 802.11

443

Infrared and Radio Waves 444

Contention 447

Addressing 449

Frame Format 451

Wired Equivalent Privacy 453

Variations of 802.11 454

9.8 SUMMARY

455

REVIEW QUESTIONS 457

EXERCISES 459

REFERENCES 461

CHAPTER 10 CONNECTING NETWORKS

462

10.1 INTRODUCTION

462

10.2 LAYER 1 CONNECTIONS

465

Repeaters and Hubs 465

10.3 LAYER 2 CONNECTIONS

467

Bridges 467

Bridging Different Types of LANs 468

Routing 469

Routing Tables 469

Transparent Bridges 471

Route Learning 471

Frame Propagation 473

Spanning Tree Algorithm 475

Source-Routing Bridges 479

Switches and Switched Ethernet 480

Virtual LANs 484

10.4 LAYER 3 CONNECTIONS

487

Routing Tables 488

Centralized Routing 490

Distributed Routing 491

Static Routing 492

Adaptive Routing 492

10.5 DIJKSTRA''S ALGORITHM

493

10.6 THE BELLMAN-FORD ALGORITHM

496

Problems with the Bellman-Ford Algorithm

500

10.7 ADDITIONAL ROUTING METHODS

502

Link State Routing 502

Hierarchical Routing 503

Routing Information Protocol 506

Open Shortest Path First 509

Border Gateway Protocol 510

Summary of Routing Techniques 512

10.8 CONGESTION AND DEADLOCK

512

Congestion 512

Deadlock 515

10.9 SUMMARY

517

REVIEW QUESTIONS 519

EXERCISES 520

REFERENCES 523

CHAPTER 11 INTERNET PROTOCOLS AND APPLICATIONS

524

11.1 INTRODUCTION

524

11.2 INTERNET PROTOCOL

525

Overview of TCP/IP 526

Internet Addressing 528

Classless Addresses 531

Obtaining an Address 533

Domain Name System 534

IP Packets 537

Fragmentation 540

IP Routing 541

Routers 546

Multicast Routing 549

Resource Reservation Protocol 555

Internet Control Message Protocol 557

11.3 IPv6

559

IP Shortcomings 560

Packet Headers 561

IPSec 564

lPv6 Addressing 566

Compatibility with IPv4 569

Summary 570

11.4 TRANSPORT PROTOCOLS

571

Transmission Control Protocol 573

TCP Segment 574

Connection Management 577

Flow Control 580

Congestion Control 582

User Datagram Protocol 584

Real-Time Transfer Protocol 585

11.5 INTERNET APPLICATIONS

589

Virtual Terminal Protocols 589

Telnet 590

Secure Shell 593

File Transfers 596

FTP 597

Secure Copy 600

Simple Mail Transfer Protocol 600

Simple Network Management Protocol 604

Management Information Base 605

SNMP Commands 606

11.6 SUMMARY

608

REVIEW QUESTIONS 610

EXERCISES 612

REFERENCES 614

CHAPTER 12 INTERNET PROGRAMMING

616

12.1 INTRODUCTION

616

12.2 SOCKET PROGRAMMING

617

Sockets 618

Client/Server Model 619

Socket Data Structures 620

Socket Commands 621

Client/Server Example 621

Client Source Code 624

Server Source Code 631

12.3 WORLD WIDE WEB

633

Web Page Access 634

Hypertext Markup Language 636

Tags 637

HTML Forms 641

Client-Side Programming and JavaScript 644

12.4 COMMON GATEWAY INTERFACE AND SERVER-SIDE PROGRAMMING:

SETTING UP A SEARCH ENGINE

649

Forms 650

Query Strings 651

Example Search Engine 651

12.5 PERL PROGRAMMING: PIZZA ORDERING SYSTEM

654

Customer Interaction 655

Verifying Phone Numbers 658

Updating Customer Information 665

Placing an Order 668

Verifying the Order 669

12.6 SUMMARY

672

REVIEW QUESTIONS 673

EXERCISES 674

REFERENCES 676

CHAPTER 13 CIRCUIT TECHNOLOGIES

677

13.1 INTRODUCTION

677

13.2 INTEGRATED SERVICES DIGITAL NETWORK

678

Services 679

Architecture 681

Protocols 683

Signaling System 7 684

Basic Service Protocols 686

Call Setup 689

Broadband ISDN 691

13.3 VIRTUAL CIRCUIT PROTOCOLS: X.25 AND FRAME RELAY

692

Packet-Switched Network Modes 693

Virtual Circuits 693

Datagram Service 695

X.25 Interface Standard 696

Packet Format 697

Virtual Calls 698

Frame Relay 699

Frame Format 701

Committed Information Rate 702

Congestion Control 703

13.4 ASYNCHRONOUS TRANSFER MODE

705

Benefits of Small Fixed-Size Cells 706

Overview of ATM Network 708

Switching 709

Banyan Switches 710

Reference Model 712

Cell Definition 713

Header Error Control 714

Cell Loss Priority 716

Payload Type 716

Virtual Circuits and Paths 716

Connection Management 717

Connection Parameters 719

Adaptation Layers 720

AAL 1 721

AAL 2 723

AAL 5 724

Service-Specific Connection-Oriented Protocol 725

Gigabit Ethernet versus ATM 726

13.5 SUMMARY

727

RENEW QUESTIONS 727

EXERCISES 729

REFERENCES 730

GLOSSARY

ACRONYMS

INDEX