计算机通信与网络技术PDF电子书下载

Ⅰ COMPUTER COMMUNICATIONS AND NETWORK BASICS 1

1 Overview of Computer Communications and Networking 2

1.1 What Does Computer Communications and Networking Technologies Mean? 3

1.2 What Is a Computer Network？ 4

Network Members:Devices,Nodes,and Hosts 4

Network Media and Communication Protocols 5

1.3 Types of Computer Networks 7

Classifying Networks by the Area They Encompass 7

Classifying Networks by Their Topology 9

Switched Networks 14

1.4 Network Addressing,Routing,Reliability,Interoperability,and Security 16

Addressing 16

Routing 17

Reliability 17

Interoperability 18

Security 18

1.5 Network Standards 19

De Jure Standards 20

De Facto Standards 20

Proprietary Standards 21

Consortia Standards 21

Internet Standards Development 22

1.6 The Telephone System and Data Communications 23

The Invention of the Telephone 23

The Evolution of the Telephone Industry and AT&T 24

The AT&T Breakup of 1984 25

The Telecommunications Act of 1996 26

Data Communications versus Telecommunications 27

1.7 Organization of the Book 28

End-of-Chapter Commentary 29

Chapter Review Moterials 30

2 Essential Terms and Concepts 33

2.1 Network Applications and Application Protocols 34

2.2 Computer Communications and Networking Models 37

Decentralized Systems 37

CentralizedSystems 38

Distributed Systems 38

Client/Server Model 40

Peer-to-Peer Model 41

Web-Based Model 43

Emerging File-Sharing Model Servant 44

2.3 Communication Service Methods and Data Transmission Modes 45

Serial and Parallel Communications 45

Synchronous,Asynchronous,and Isochronous Communications 46

Simplex and Duplex Communications 48

2.4 Analog and Digital Communications 49

Analog Communications 49

Digital Communications 51

2.5 Speed and Capacity of a Communications Channel 54

Bandwidth andData Rate 54

Throughput 55

Noise 55

2.6 Multiplexing and Switching 59

Multiplexing 59

Switching 62

2.7 Network Architecture and the OSI Reference Model 65

The OSI Model 65

OSI Service Types 67

OSI Today 70

End-of-Chapter Commentary 71

Chapter Review Materials 72

3 Analog and Digital Communications Concepts 76

3.1 Representing Data as Analog Signals 77

Converting Analog Data to Analog Signals 77

Converting Digital Data to Analog Signals 79

3.2 Representing Data as Digital Signals 87

Converting Analog Data to Digital Signals 87

Converting Digital Data to Digital Signals 90

3.3 Data Rate and Baud Rate Redux 92

3.4 Digital Carrier Systems 93

T1 and DS Circuits 93

Fractional T1 95

SONET and OC Circuits 98

End-of-Chapter Commentary 100

Chapter Review Materials 100

Ⅱ Physical,Data Link,and Network Layer Concepts 107

4 Physical Layer Concepts 108

4.1 What Is the Physical Layer? 109

4.2 The Physical and Electrical Characteristics of Wire 110

Physical Characteristics 111

Electrical Characteristics 114

4.3 Copper Media 116

Unshielded and Shielded Twisted-Pair Cable 116

IBM Cable 118

Coaxial Cable 119

Twin Axial Cable 120

4.4 Fiber-Optic Media 120

4.5 Wireless Communications 124

Radio Transmission 124

Infrared Transmission 127

Wireless LAN Standards 128

4.6 Satellite Communications 129

4.7 Structured Cabling Systems 133

End-of-Chapter Commentary 135

Chapter Review Materials 135

5 Data Link Layer Concepts and IEEE LAN Standards 139

5.1 What Is the Data Link Layer? 140

Overview 140

The IEEE and the Data Link Layer 141

5.2 The Logical Link Control(LLC)Sublayer 142

Framing 142

Flow Control 146

Error Control 152

5.3 The Media Access Control(MAC)Sublayer 158

Random Access Protocols 158

Token Passing Protocols 161

Random Access versus Token Passing Protocols 162

5.4 Data Prioritization and Quality of Service 163

End-of-Chapter Commentary 166

Chapter Review Materials 166

6 Network Hardware Components(Layers 1 and 2) 170

6.1 What Are Connectors? 171

Overview 171

UTP Cable Connectors 171

Coaxial Cable Connectors 172

Fiber-Optic Cable Connectors 173

Other Connectors 173

6.2 Transceivers and Media Converters 174

Transceivers 174

Media Converters 176

6.3 Repeaters 177

Repeaters versus Hubs 177

6.4 Network Interface Cards and PC Cards 179

Network Interface Cards 179

PC Cards 181

6.5 Bridges 182

Overview 182

Bridge Standards 183

Bridges versus Repeaters 187

6.6 Switches 188

Store-and-Forward Switch 188

Cut-Through Switch 189

Hybrid Switch 190

Switch Performance 190

End-of-Chapter Commentary 192

Chapter Review Materials 192

7 Internetworking and Network Layer Concepts and Components 195

7.1 Internetworking Concepts 196

7.2 The Network Layer and Routing Concepts 200

Network Layer Overview 200

Routing Protocol Concepts 202

Routing Algorithms 205

7.3 Sample Routing Protocols 208

Autonomous Systems and Interior and Border Gateway Protocols 208

RIP 208

RIP-2 211

OSPF 212

Other Routing Protocols 214

Classless Interdomain Routing 215

7.4 Routers and Switches 215

Overview(Review)of Switches and Switching 215

Layer-2 and Layer-3 Switches versus Routers 216

Layer-4 Switching 217

IP Switching 217

Brouter versus Router 218

7.5 Virtual Private Networks(VPNs) 218

VPN Strategies 218

VPN Benefits 221

End-of-Chapter Commentary 223

Chapter Review Materials 223

8 The Internet and TCP/IP 229

8.1 What Is the Internet? 230

8.2 Internet History 231

ARPANET 231

BITNET,CSNET,and UUCP 231

NSFNET 233

A Commercial Internet 236

The Current Public Internet 237

Other Internet Backbone Initiatives 238

8.3 Internet Administration 240

Governance and Organization 240

Standards Development 241

Internet Security 242

8.4 What Is TCP/IP? 243

A Brief History 243

The TCP/IP Model versus the OSI Model 245

8.5 TCP/IP's Transport and Network Layer Protocols 248

Overview of Internet-Based Communications and the Role of UDP,TCP,IP,and Port Numbers 248

The User Datagram Protocol(UDP) 249

The Transport Control Protocol(TCP) 252

The Internet Protocol(IP) 260

8.6 IP Addresses 263

IPv4 263

Subnetting IPv4 Addresses 265

IP Address Resolutions:DNS 270

IP Address and Name Assignment 273

8.7 IPv6 274

The Need for IPv6 274

I Pv6 versus IPv4 275

I Pv6 Addresses 278

I Pv6 Migration 280

8.8 TCP/IP Application Level Protocols 281

Electronic Mail:SMTP,MIME,and POP 281

The TELNET Protocol 291

The File Transfer Protocol(FTP) 293

The Hypertext Transfer Protocol(HTTP) 295

End-of-Chapter Commentary 304

Chapter Review Materials 304

Ⅲ Local and Wide Area Networking Technologies 311

9 Ethernet and IEEE 802.3 Networks 312

9.1 The History of Ethernet 313

In the Beginning 313

Ethernet versus IEEE 802.3 314

9.2 10-MBPS Ethernet/802.3 LANS 316

Physical and Data Link LayerInformation 316

The Concept of Network Diameter and Collision Domain 321

The 5-4-3 Repeater Placement Rule 324

Workarounds to the 5-4-3 Repeater Placement Rule 325

Performance Issues 326

9.3 Switched Ethernet,Full-Duplex Ethernet,and Virtual LANs 328

The Concept of Segmentation 328

Switched Ethernet 330

Full-Duplex Ethernet 335

Virtual Local Area Networks(VLANs) 336

9.4 100-MBPS Ethernet LANs 337

Fast Ethernet 338

100VG-AnyLAN 342

9.5 Gigabit Ethernet 346

Overview 346

IEEE 802.3z:Gigabit Ethernet over Fiber 348

IEEE 802.3ab:Gigabit Ethernet over Copper 350

Gigabit Ethernet versus Asynchronous TransferMode (ATM) 351

Gigabit Ethernet's Bottom Line 352

Is Faster Better? 353

Ethernet as a WAN Protocol:IEEE 802.3ae—10-Gigabit Ethernet 353

9.6 Other Ethernet-Related Projects 354

End-of-Chapter Commentary 355

Chapter Review Materials 355

10 Token Ring 361

10.1 What Is Token Ring? 362

10.2 Physical Layer Specifications 364

10.3 Frame Formats 365

The Token Frame 365

The Data Frame 366

10.4 Priority and Reservation 368

10.5 Monitor Stations 369

10.6 Second-Generation Token Ring 370

Switched Token Ring 370

Dedicated Token Ring 372

Full-Duplex Token Ring 373

High-Speed Token Ring 373

10.7 Token Ring versus Token Bus 374

End-of-Chapter Commentary 375

Chapter Review Materials 375

11 Fiber Distributed Data Interface(FDDI) 378

11.1 What Is FDDI? 379

11.2 Physical Layer Specifications 381

11.3 Frame Formats and Medium Access Specifications 382

Frame Formats 382

MAC Sublayer:FDDI versus Token Ring 384

Operation 385

11.4 Configuration and Design Issues 386

11.5 Interconnecting FDDI with Ethernet/802.3 or ATM Networks 388

11.6 The Future of FDDI 390

End-of-Chapter Commentary 390

Chapter Review Materials 391

12 Integrated Services Digital Network(ISDN) 393

12.1 What Is ISDN? 394

History 394

Standards 396

12.2 ISDN Components 398

Modules,Equipment,and Adapters 398

Interfaces 399

12.3 ISDN Channel Types 400

B Channel 401

D Channel 401

H Channel 402

12.4 Basic and Primary Rate Interfaces 402

Basic Rate Interface(BRI) 402

Primary Rate Interface(PRI) 403

12.5 ISDN Protocols 404

Overview 404

Link Access Protocol-D Channel(LAP-D) 405

12.6 ISDN Features,Services,and Applications 406

Service Profile Identification(SPID)Numbers 406

Line and Feature Sets 406

Teleservices 407

ISDN versus Regular Phone Service 407

ISDN and the Internet 408

LAN-to-LAN Connections 409

12.7 Other ISDN Initiatives 410

Always On/Dynamic ISDN 410

Broadband ISDN 411

End-of-Chapter Commentary 411

Chapter Review Materials 412

13 Frame Relay 416

13.1 What Is Frame Relay? 417

13.2 Frame Relay Circuits 420

Permanent Virtual Circuit(PVC) 420

Committed Information Rate(CIR) 422

CIR and Oversubscription 423

Switched Virtual Circuit(SVC) 426

13.3 Technical Overview and Data Link Layer Issues 427

Basic Operation 427

Frame Relay Frames 428

Data Link Connection Identifier(DLCI) 430

Congestion Control and Management 432

Link Management 434

13.4 Additional Frame Relay Information 434

Voice Over Frame Relay 434

Frame Relay versus Other LAN-to-LAN Technologies 436

Frame Relay in the News 436

End-of-Chapter Commentary 437

Chapter Review Materials 437

14 Switched Multimegabit Data Service(SMDS) 441

14.1 What Is SMDS? 442

Overview 442

History 443

Development Rationale 443

14.2 SMDS Technical Overview 444

Physical Layer Specifications 444

Data Link Layer Specifications:DQDB 446

14.3 The SMDS Interface Protocol(SIP) 447

14.4 SMDS Addressing 451

14.5 SMDS versus Other LAN-to-LAN Technologies 452

SMDS versus Frame Relay and ATM 452

14.6 Status of SMDS Today 453

End-of-Chapter Commentary 455

Chapter Review Materials 455

15 Asynchronous Transfer Mode(ATM) 458

15.1 What Is ATM? 459

Overview 459

History 459

15.2 General Concepts and Operation 461

General Concepts 461

Operation 461

15.3 ATM Interface Standards 463

15.4 ATM Cells,Virtual Connections,and Addressing 465

ATM Cells 465

Virtual Connections 467

Addressing 469

15.5 ATM Adaptation Layer(AAL) 470

15.6 ATM and Convergence Technology 472

15.7 ATM versus Other Technologies and Services 473

ATM versus Fast and Gigabit Ethernet 473

ATM versus Frame Relay 474

ATM versus SONET 475

ATM as an Emulated LAN Technology 475

End-of-Chapter Commentary 477

Chapter Review Materials 477

Ⅳ Related Networking Concepts,Applications,and Technologies 477

16 Dialup and Home Networking 482

16.1 What Is Dialup Networking? 483

Terminal Dialup Connection 483

Network Dialup Connection 485

16.2 Analog Modem Concepts 485

Overview 485

Modem Standards 486

DCE,DTE,Compression,and Error Control 486

56K Modems 489

16.3 DSL Service 490

Overview 490

DSL Transmission Rates and Circuit Quality 492

Types of DSL Service 494

16.4 Cable Modems 498

16.5 Home Networking Concepts and Issues 501

Connecting to the Internet 502

Interconnecting More Than One Home Computer 504

The Home Network Infrastructure 505

Home Network Security 505

Potential Problems When Configuring a Home Network 506

End-of-Chapter Commentary 507

Chapter Review Materials 508

17 Network Security Issues 512

17.1 What Is Network Security? 513

17.2 Threat Assessment 513

Identifying Critical Assets 514

Who Covets Your Assets? 516

Risk Analysis 517

War Games 518

Documentation 518

17.3 Network Attacks and Security Measures Considerations 518

Examples of Network Attacks 518

Denial of Service(DoS)Attacks 519

Obstacles to Implementing Network Security 521

Security Measures Considerations 521

17.4 Firewalls 524

Overview 524

Type of Firewalls 524

Firewalls and Multiprotocol Environments 526

Firewall Implementation Considerations 527

17.5 Encryption Methods 528

Overview 528

Public Key Infrastructure(PKI) 530

Data Encryption Standard(DES) 530

Pretty Good Privacy(PGP) 531

RSA 532

17.6 Authentication and Access Control Measures 537

Digital Certificates 538

SmartCards 538

Kerberos 539

17.7 Virtual Private Networks and Internet Security 539

VPN Security Protocols 540

The IP Security Protocol(IPSec) 541

Protecting VPN Connections 544

End-of-Chapter Commentary 545

Chapter Review Materials 545

18 Network Convergence 549

18.1 What Is Network Convergence? 550

Overview 550

Convergence Is More Than Combining Voice and Data 552

18.2 Networking Issues and Convergence 554

Network Media and Convergence 554

Network Applications and Convergence 556

Convergence and Multimedia Networking 557

18.3 Effects of Network Convergence on Businesses 559

Convergence Effects on Legacy Networks and Systems 559

Convergence Effects on Computing and Networking Styles 560

Convergence Effects on Network Performance and Growth Rate 561

Organizational Changes and Convergence 562

Network Management and Convergence 563

Convergence and the Internet with Corporate Network Applications 564

18.4 Convergence at Home 565

End-of-Chapter Commentary 566

Chapter Review Materials 567

A Vendor Ethernet/802.3 Prefixes 570

B Using Parity for Single-Bit Error Correction 571

C Guidelines for Installing UTP Cable 574

D Network Design and Analysis Guidelines;Network Politics 576

E X.25 582

Glossary 587

Index 617