Data and Computer Communications

DATA AND COMPUTER COMMUNICATIONS Eighth Edition William Stallings Upper Saddle River, New Jersey 07458 Library of Congress Cataloging-in-Publication Grounds on Smooth Vice President and Editorial Director, ECS: Marcia J. Horton Executive Editor: Tracy Dunkelberger Assistant Editor: Carole Snyder Editorial Assistant: Christianna Lee Executive Managing Editor: Vince O’Brien Managing Editor: Camille Trentacoste Formation Editor: Rose Kernan Director of Creative Services: Paul Belfanti Creative Director: Juan Lopez Cloak Designer: Bruce Kenselaar Managing Editor,AV Administration and Production: Patricia Burns ©2007 Pearson Education, Inc. Pearson Prentice Hall Pearson Education, Inc. Upper Saddle River, NJ 07458 Art Editor: Gregory Dulles Director, Representation Rebeginning Center: Melinda Reo Manager, Hues and Permissions: Zina Arabia Manager,Visual Research: Beth Brenzel Manager, Cloak Visual Scrutiny and Permissions: Karen Sanatar Manufactumelody Manager, ESM: Alexis Heydt-Long Manufactumelody Buyer: Lisa McDocourteous Executive Marketing Manager: Robin O’Brien Marketing Assistant: Mack Patterson All hues silent. No distribute of this bulk may be reeffected in any mould or by any instrument, extraneously sufferance in congruity from the publisher. Pearson Prentice Hall™ is a trademark of Pearson Education, Inc. All other tradmarks or employment names are the truth of their appertaining owners. The doer and publisher of this bulk possess used their best efforts in prepamelody this bulk. These efforts beneathstand the crop, scrutiny, and testing of the theories and programs to indicate their benefitableness. The doer and publisher converge no safeguard of any peel, familiar or conceived, retreat mind to these programs or the documentation incloseed in this bulk. The doer and publisher shall not be biased in any fact for conrunning or logical amages in association retreat, or arising out of, the furnishing, deed, or use of these programs. Printed in the United States of America 10 9 8 7 6 5 4 3 2 1 ISBN: 0-13-243310-9 Pearson Advice Ltd. , London Pearson Advice Australia Pty. Ltd. , Sydney Pearson Advice Singapore, Pte. Ltd. Pearson Advice North Asia Ltd. , Hong Kong Pearson Advice Canada, Inc. , Toronto Pearson Educaci n de Mexico, S. A. de C. V. Pearson Advice Japan, Tokyo Pearson Advice Malaysia, Pte. Ltd. Pearson Education, Inc. , Upper Saddle River, New Jersey For my scintillating accelerationmate ATS WEB SITE FOR DATA AND COMPUTER COMMUNICATIONS, EIGHTH EDITION The Web birth at WilliamStallings. com/DCC/DCC8e. html contributes assistance for professors and wards using the bulk. It beneathstands the forthcomingcited atoms. Way Assistance Materials The way assistance esthetics beneathstand • Copies of figures from the bulk in PDF mouldat • A inferential set of way notes in PDF mouldat expend for ward indexout or for use as endgraphs • A set of PowerPoint slides for use as Nursing Dissertation aids • Computer Comprehension Ward Assistance Site: incloses a reckon of incorporates and documents that the ward may converge benefittelling in his/her ongoing parliamentuter parliamentrehension advice. The birth beneathstands a revisal of basic, expend mathematics; advice on scrutiny, congruity, and doing abodeemployment problems; incorporates to parliamentuter parliamentrehension scrutiny resources, such as intimation repositories and bibliographies; and other benefittelling incorporates. • An errata fencing for the bulk, updated at most monthly T DCC Courses The DCC8e Web birth beneathstands incorporates to Web births for ways taught using the bulk. These births can contribute benefittelling subjects encircling scheduling and theme ordering, as courteous as a reckon of benefittelling indexouts and other esthetics. Servicetelling Web Sites The DCC8e Web birth beneathstands incorporates to expend Web births, arranged by paragraph. The incorporates cloak a indelicate spectrum of themes and conciliate strengthen wards to prove prompt issues in esthetic profundity. iv WEB SITE FOR DATA AND COMPUTER COMMUNICATIONS, EIGHTH EDITION v Supplemental Documents The DCC8e Web birth beneathstands a reckon of documents that diffuse on the quotationure in the bulk. Topics beneathstand criterions outcomes, Sockets, TCP/IP checksum, ASCII, and the sampling theorem. Internet Mailing Inventory An Internet mailing inventory is detained so that professors using this bulk can substitute advice, suggestions, and doubts retreat each other and the doer. Subscription advice is contributed at the bulk’s Web birth. Airs and Modeling Tools The Web birth beneathstands incorporates to the cnet Web birth and the methodling implements Web birth. These bundles can be used to criticise and trial retreat protocol and netemployment plan issues. Each birth beneathstands downloadtelling software and setting advice. The professor’s manual beneathstands erect advice on carrying and using the software and suggested ward plans. This page intentionally left utter CONTENTS Web Birth for Grounds and Computer Communications Preface xv 1 iv Paragraph 0 Reader’s and Instructor’s Direct 0. Outdirection of the Bulk 2 0. 2 Roadmap 3 0. 3 Internet and Web Resources 5 0. 4 Standards 6 PART ONE OVERVIEW 9 Paragraph 1 Grounds Communications, Grounds Networking, and the Internet 10 1. 1 Grounds Communications and Netinstituted for Today’s Act 12 1. 2 A Communications Type 16 1. 3 Grounds Communications 19 1. 4 Networks 22 1. 5 The Internet 25 1. 6 An Observation Configuration 29 Paragraph 2 Protocol Architecture, TCP/IP, and Internet-Based Applications 2. 1 The Call-for for a Protocol Erection 33 2. 2 The TCP/IP Protocol Erection 34 2. 3 The OSI Type 42 2. 4 Standardization retreatin a Protocol Erection 44 2. Infections Internet-Based Applications 48 2. 6 Multiinstrument 48 2. 7 Recommended Balbutiation and Web Sites 53 2. 8 Key Terms, Revisal Questions, and Problems 54 Epilogue 2A The Trivial Smooth Transplant Protocol 57 PART TWO DATA COMMUNICATIONS 62 Paragraph 3 Grounds Transmission 65 3. 1 Concepts and Terminology 67 3. 2 Analog and Digital Grounds Transmission 78 3. 3 Transmission Impairments 86 3. 4 Channel Parts 91 3. 5 Recommended Balbutiation and Web Birth 96 3. 6 Key Terms, Revisal Questions, and Problems Epilogue 3A Decibels and Eminent Strength 99 Paragraph 4 Transmission Instrument 102 4. Guided Transmission Instrument 104 4. 2 Wireclose Transmission 117 4. 3 Wireclose Propagation 125 32 96 vii viii CONTENTS 4. 4 4. 5 4. 6 Line-of-Sight Transmission 129 Recommended Balbutiation and Web Sites 133 Key Terms, Revisal Questions, and Problems 134 Paragraph 5 Eminent Encoding Techniques 138 5. 1 Digital Data, Digital Signals 141 5. 2 Digital Data, Analog Signals 151 5. 3 Analog Data, Digital Signals 162 5. 4 Analog Data, Analog Signals 168 5. 5 Recommended Balbutiation 175 5. 6 Key Terms, Revisal Questions, and Problems 175 Paragraph 6 Digital Grounds Intimation Techniques 180 6. Incontemporaneous and Synchronous Transmission 182 6. 2 Types of Errors 186 6. 3 Fallacy Counteraction 186 6. 4 Fallacy Punishment 196 6. 5 Direction Configurations 201 6. 6 Recommended Balbutiation 203 6. 7 Key Terms, Revisal Questions, and Problems 204 Paragraph 7 Grounds Incorporebuke Manage Protocols 207 7. 1 Career Manage 209 7. 2 Fallacy Manage 216 7. 3 High-Level Grounds Incorporebuke Manage (HDLC) 222 7. 4 Recommended Balbutiation 228 7. 5 Key Terms, Revisal Questions, and Problems 229 Epilogue 7A Deed Issues 232 Paragraph 8 Multiplexing 239 8. 1 Frequency-Division Multiplexing 242 8. 2 Synchronous Time-Division Multiplexing 248 8. Statistical Time-Division Multiplexing 258 8. 4 Asymmetric Digital Subscriber Direction 265 8. 5 xDSL 268 8. 6 Recommended Balbutiation and Web Sites 269 8. 7 Key Terms, Revisal Questions, and Problems 270 Paragraph 9 Circulate Spectrum 274 9. 1 The Concept of Circulate Spectrum 276 9. 2 Frequency Hopping Circulate Spectrum 277 9. 3 Direct Posteriority Circulate Spectrum 282 9. 4 Code-Division Multiple Beamelody 287 9. 5 Recommended Balbutiation and Web Birth 290 9. 6 Key Terms, Revisal Questions, and Problems 291 CONTENTS ix PART THREE WIDE AREA NETWORKS 295 Paragraph 10 Circumference Switching and Packet Switching 297 10. Switched Communications Networks 299 10. 2 Circumference Switching Networks 301 10. 3 Circumference Switching Concepts 304 10. 4 Softswitch Erection 307 10. 5 Packet-Switching Principles 309 10. 6 X. 25 317 10. 7 Mould Refreshment 319 10. 8 Recommended Balbutiation and Web Sites 324 10. 9 Key Terms, Revisal Questions, and Problems 325 Paragraph 11 Incontemporaneous Transplant Method 328 11. 1 Protocol Erection 329 11. 2 ATM Logical Connections 331 11. 3 ATM Cells 335 11. 4 Transmission of ATM Cells 340 11. 5 ATM Benefit Categories 345 11. 6 Recommended Balbutiation and Web Sites 348 11. Key Terms, Revisal Questions, and Problems 349 Paragraph 12 Routing in Switched Networks 351 12. 1 Routing in Packet-Switching Networks 352 12. 2 Examples: Routing in ARPANET 362 12. 3 Least-Cost Algorithms 367 12. 4 Recommended Balbutiation 372 12. 5 Key Terms, Revisal Questions, and Problems 373 Paragraph 13 Congeries Manage in Grounds Networks 377 13. 1 Effects of Congeries 379 13. 2 Congeries Manage 383 13. 3 Interprogress Administration 386 13. 4 Congeries Manage in Packet-Switching Networks 13. 5 Mould Refreshment Congeries Manage 388 13. 6 ATM Interprogress Administration 394 13. 7 ATM-GFR Interprogress Administration 406 13. Recommended Balbutiation 409 13. 9 Key Terms, Revisal Questions, and Problems 410 Paragraph 14 Cellular Wireclose Networks 413 14. 1 Principles of Cellular Networks 415 14. 2 Highest Breed Analog 427 14. 3 Promote Breed CDMA 429 14. 4 Third Breed Systems 437 14. 5 Recommended Balbutiation and Web Sites 440 14. 6 Key Terms, Revisal Questions, and Problems 441 387 x CONTENTS PART FOUR LOCAL AREA NETWORKS 444 Paragraph 15 Persomal Area Netemployment Overend 446 15. 1 Setting 448 15. 2 Topologies and Transmission Instrument 451 15. 3 LAN Protocol Erection 457 15. 4 Bridges 465 15. 5 Flake 2 and Flake 3 Switches 473 15. Recommended Balbutiation and Web Birth 478 15. 7 Key Terms, Revisal Questions, and Problems 479 Paragraph 16 High-Speed LANs 482 16. 1 The Emergence of High-Speed LANs 483 16. 2 Ethernet 485 16. 3 Fibre Channel 500 16. 4 Recommended Balbutiation and Web Sites 504 16. 5 Key Terms, Revisal Questions, and Problems 506 Epilogue 16A Digital Eminent Encoding for LANs 508 Epilogue 16B Deed Issues 514 Epilogue 16C Scrambling 518 Paragraph 17 Wireclose LANs 522 17. 1 Overend 523 17. 2 Wireclose LAN Technology 528 17. 3 IEEE 802. 11 Erection and Services 531 17. 4 IEEE 802. 11 Average Beamelody Manage 535 17. 5 IEEE 802. 1Physical Flake 543 17. 6 IEEE 802. 11 Pledge Considerations 549 Recommended Balbutiation and Web Sites 550 17. 7 17. 8 Key Terms, Revisal Questions, and Problems 551 PART FIVE INTERNET AND TRANSPORT PROTOCOLS Paragraph 18 Internetemployment Protocols 556 18. 1 Basic Protocol Functions 558 18. 2 Principles of Internetinstituted 566 18. 3 Internet Protocol Influence 569 18. 4 Internet Protocol 576 18. 5 IPv6 586 18. 6 Implicit Secret Networks and IP Pledge 596 18. 7 Recommended Balbutiation and Web Sites 599 18. 8 Key Terms, Revisal Questions, and Problems 600 Paragraph 19 Internetemployment Influence 603 19. 1 Multicasting 605 19. Routing Protocols 614 19. 3 Integrated Services Erection 625 19. 4 Differentiated Services 636 554 CONTENTS xi 19. 5 19. 6 19. 7 19. 8 Benefit Flatten Agreements 645 IP Deed Metrics 646 Recommended Balbutiation and Web Sites 649 Key Terms, Revisal Questions, and Problems 651 657 Paragraph 20 Transport Protocols 655 20. 1 Connection-Oriented Transport Protocol Mechanisms 20. 2 TCP 674 20. 3 TCP Congeries Manage 683 20. 4 UDP 693 20. 5 Recommended Balbutiation and Web Sites 695 Key Terms, Revisal Questions, and Problems 695 20. 6 PART SIX Paragraph 21 21. 1 21. 2 21. 3 21. 4 21. 5 21. 6 21. 7 21. 8 21. INTERNET APPLICATIONS 699 Netemployment Pledge 701 Pledge Requirements and Attacks 703 Confidentiality retreat Conventional Encryption 705 Intimation Authentication and Hash Functions 713 Public-Key Encryption and Digital Signatures 720 Detain Socket Flake and Transport Flake Pledge 727 IPv4 and IPv6 Pledge 732 Wi-Fi Protected Beamelody 737 Recommended Balbutiation and Web Sites 739 Key Terms, Revisal Questions, and Problems 740 Paragraph 22 Internet Applications—Electronic Mail and Netemployment Administration 22. 1 Electronic Mail: SMTP and MIME 745 22. 2 Netemployment Management: SNMP 760 22. 3 Recommended Balbutiation and Web Sites 770 22. Key Terms, Revisal Questions, and Problems 771 743 Paragraph 23 Internet Applications—Internet Directory Benefit and Cosmos-people Distant Web 23. 1 Internet Directory Service: DNS 774 23. 2 Web Access: HTTP 784 23. 3 Recommended Balbutiation and Web Sites 795 23. 4 Key Terms, Revisal Questions, and Problems 796 Paragraph 24 Internet Applications—Multiinstrument 799 24. 1 Audio and Video Compression 800 24. 2 Real-Time Interprogress 808 24. 3 Utterance Balance IP and Multiinstrument Support—SIP 811 24. 4 Real-Time Transport Protocol (RTP) 820 24. 5 Recommended Balbutiation and Web Sites 831 24. 6 Key Terms, Revisal Questions, and Problems 832 773 ii CONTENTS APPENDICES 835 Epilogue A Fourier Disexception 835 A. 1 Fourier Series Representation of Periodic Signals 836 A. 2 Fourier Transmould Representation of Aperiodic Signals 837 A. 3 Recommended Balbutiation 840 Epilogue B Projects for Training Grounds and Computer Communications B. 1 Practical Exercises 842 B. 2 Sockets Projects 843 B. 3 Ethereal Projects 843 B. 4 Airs and Modeling Projects 844 B. 5 Deed Modeling 844 B. 6 Scrutiny Projects 845 B. 7 Reading/Report Assignments 845 B. 8 Congruity Assignments 845 B. 9 Displan Topics 846 References Index 858 ONLINE APPENDICES WilliamStallings. om/DCC Epilogue C Sockets: A Programmer’s Insertion C. 1 Versions of Sockets C. 2 Sockets, Socket Descriptors, Ports, and Connections The Client/Server Type of Intimation C. 3 C. 4 Sockets Elements C. 5 Drift and Datagram Sockets C. 6 Run-Time Program Manage C. 7 Foreign Execution of a Windows Console Contact Epilogue D Standards Organizations D. 1 The Weight of Standards D. 2 Standards and Regulation D. 3 Standards-Setting Organizations Epilogue E Epilogue F The Interdiplomatic Regard Alphabet Proof of the Sampling Theorem 847 841 Epilogue G Physical-Layer Interfacing G. 1 V. 24/EIA-232-F G. ISDN Embodied Interface Epilogue H The OSI Type H. 1 The Type H. 2 The OSI Layers CONTENTS xiii Epilogue I Queuing Effects I. 1 Queuing Models I. 2 Queuing Results Epilogue J Orthogonality, Correlation, and Autocorrelation J. 1 Correlation and Autocorrelation J. 2 Orthogonal Codes Epilogue K The TCP/IP Checksum K. 1 Ones-Complement Specification K. 2 Use in TCP and IP Epilogue L TCP/IP Observation Epilogue M Unimould Rebeginning Locators (URLs) and Unimould Rebeginning Identifiers (URIs) M. 1 Unimould Rebeginning Locator M. 2 Unimould Rebeginning Identifier M. 3 To Learn Erect Epilogue N Scholiast Augmented Backus-Naur Form This page intentionally left utter PREFACE Initiate at the rise and go on prepare you conclude to the end; then bung. —Alice in Wonderland, Lewis Carroll OBJECTIVES This bulk trys to contribute a unified balanceend of the indelicate arena of grounds and parliamentuter intimations. The outcome of the bulk animadverts an try to curb this weighty doubt into plain distributes and to establish, concern by concern, a revisal of the propound of the art. The bulk emphasizes basic principles and themes of primary weight touching the technology and erection of this arena and contributes a inferential displan of leading-edge themes. The forthcomingcited basic themes ataid to unify the disquisition: • Principles: Although the delineateing of this bulk is indelicate, tclose are a reckon of basic principles that answer constantly-again-and-frequently as themes and that unify this arena. Examples are multiplexing, career manage, and fallacy manage. The bulk haughtylights these principles and contrasts their contact in persomal areas of technology. • Plan wayes: The bulk examines opinion wayes to displan persomal intimation limitations. • Standards: Standards possess conclude to claim an increasingly esthetic, verily dominant, role in this arena. An brains of the running standing and forthhereafter inclination of technology claims a parliamentendious displan of the cognate criterions. INTENDED AUDIENCE The bulk is adapted for twain an academic and a administrative interview. For the administrative ardent in this arena, the bulk attends as a basic regard lump and is expend for self-study. As a quotationbook, it can be used for a one-semester or two-semester way. It cloaks the esthetic in Netinstituted (NET), a kernel area in the Advice Technology lump of acquaintance, which is distribute of the Drain ACM/IEEE/AIS Computing Curricula 2005. The bulk besides cloaks the esthetic in Computer Networks (CE-NWK), a kernel area in Computer Engineemelody 2004 Curriculum Guidelines from the ACM/IEEE Joint Task Force on Computing Curricula. PLAN OF THE TEXT The bulk is severedd into six distributes (see Paragraph 0): • Overend • Grounds Communications • Distant Area Networks xv xvi PREFACE • Persomal Area Networks • Internet and Transport Protocols • Internet Applications In peculiaration, the bulk beneathstands an distant scholiast, a inventory of constantly used acronyms, and a bibliography. Each paragraph beneathstands problems and suggestions for erect balbutiation. The paragraphs and distributes of the bulk are sufficiently modular to contribute a parliamentact negotiate of flexibility in the plan of ways. See Paragraph 0 for a reckon of inferential suggestions for twain top-down and bottom-up way strategies. INSTRUCTIONAL SUPPORT MATERIALS To assistance professors, the forthcomingcited esthetics are contributed: • Solutions Manual: Solutions to all end-of-paragraph Revisal Questions and Problems. • PowerPoint Slides: A set of slides cloaking all paragraphs, expend for use in lecturing. • PDF smooths: Reproductions of all figures and tables from the bulk. Projects Manual: Suggested plan intrustments for all of the plan categories inventoryed adown. Instructors may adjunction their Pearson Advice or Prentice Hall figurative for beamelody to these esthetics. In peculiaration, the bulk’s Web birth assistances professors retreat: • Links to Webs births for other ways substance taught using this bulk • Sign up advice for an Internet mailing inventory for professors INTERNET SERVICES FOR INSTRUCTORS AND STUDENTS Tclose is a Web birth for this bulk that contributes assistance for wards and professors. The birth beneathstands incorporates to other expend births, faithfulnessfulness masters of figures in the bulk, and sign-up advice for the bulk’s Internet mailing inventory. The Web page is at WilliamStallings. com/DCC/DCC8e. html; see the singularity, Web Birth for Grounds and Computer Communications, precedent the Ttelling of Contents, for erect advice. An Internet mailing inventory has been set up so that professors using this bulk can substitute advice, suggestions, and doubts retreat each other and retreat the doer. As before-desire as typos or other fallacys are discovered, an errata inventory for this bulk conciliate be conducive at WilliamStallings. om. PROJECTS AND OTHER STUDENT EXERCISES For numerous professors, an esthetic content of a grounds intimations or netinstituted way is a plan or set of plans by which the ward gets indexs-on habit to renew concepts from the quotation. This bulk contributes an unique order of assistance for including a plans content in the way. The professor’s singularization not merely beneathstands direction on how to intrust and outcome the plans but besides beneathstands a set of User’s PREFACE xvii Manuals for opposed plan expressions plus persomal intrustments, all written distinctly for this bulk. Instructors can intrust employment in the forthcomingcited areas: • Practical exercises: Using netemployment commands, the ward gains habit in netemployment connectivity. • Sockets programming plans: The bulk is assistanceed by a inferential schemeation of Sockets conducive at the bulk’s Web birth. The Instructors singularization beneathstands a set of programming plans. Sockets programming is an “easy” theme and one that can upshot in very satisfying indexs-on plans for wards. • Ethereal plans: Ethereal is a protocol criticiser that strengthens wards to con-balance the conduct of protocols. Airs plans: The ward can use the airs bundle cnet to criticise netemployment conduct. • Deed methodling plans: Two deed methodling techniques are contributed a implements bundle and OPNET. • Scrutiny plans: The professor’s singularization beneathstands a inventory of suggested scrutiny plans that would conceive Web and attainment searches. • Reading/intimation intrustments: The professor’s singularization beneathstands a inventory of papers that can be intrusted for balbutiation and congruity a intimation, plus suggested intrustment ordering. Congruity intrustments: The professor’s singularization beneathstands a inventory of congruity intrustments to smooth education the esthetic. • Displan themes: These themes can be used in a classroom, confabulation parliamentass, or intimation consideration environment to prove convinced areas in esthetic profundity and to excite ward collaboration. This diverse set of plans and other ward exercises strengthens the professor to use the bulk as one content in a valutelling and divers education habit and to tailor a way plan to converge the persomal call-fors of the professor and wards. See Epilogue B for exceptionaltys. WHAT’S NEW IN THE EIGHTH EDITION This eighth edition is end the unregular of day close than indelicate years forthhereafter the notification of the seventh edition. Dumelody that season, the gait of exsubstitute in this arena endures unabated. In this new edition, I try to hold these substitutes opportunity detaining a indelicate and parliamentendious cloakage of the solid arena. To initiate the method of variation, the seventh edition of this bulk was distantly revisaled by a reckon of professors who indoctrinate the doubt. The upshot is that, in numerous places, the fact has been severedded and tightened, and illustrations possess been correctd. Also, a reckon of new “field-tested” problems possess been acquired. Beyond these refinements to correct pedagogy and user pacification, tclose possess been elder substantive substitutes throughout the bulk. Completion paragraph has been revised, new paragraphs possess been acquired, and the balanceall outcome of the bulk has substituted. Highlights beneathstand: • Updated cloakage of Gigabit Ethernet and 10-Gbps Ethernet: New exceptionaltys of these criterions are contributed. • Updated cloakage of WiFi/IEEE 802. 11 wireclose LANs: IEEE 802. 11 and the cognate WiFi persomalations possess endured to eject. viii PREFACE • New cloakage of IP deed metrics and benefit flatten agreements (SLAs): These exposures of Attribute of Benefit (QoS) and deed monitomelody are increasingly esthetic. • Address Resolution Protocol (ARP): This esthetic protocol is now cloaked. • New cloakage of TCP Tahoe, Reno, and NewReno: These congeries manage algorithms are now base in most retail implementations. • Expanded cloakage of pledge: Paragraph 21 is erect inferential; other paragraphs contribute balanceend of pledge for the expend theme. Among the new themes are Wi-Fi Protected Beamelody (WPA) and the detain hash algorithm SHA-512. • Domain Name Method (DNS): This esthetic delineation is now cloaked. • New cloakage of multimedia: Precursory singularity in Paragraph 2; inferential cloakage in Paragraph 24. Topics cloaked beneathstand video parliamentression, SIP, and RTP. • Ondirection appendices: Fourteen ondirection appendices contribute peculiarational exceptionalty on esthetic themes in the quotation, including Sockets programming, queuing methodls, the Internet checksum, a inferential observation of TCP/IP influence, and the BNF phraseology. In peculiaration, throughout the bulk, implicitly completion theme has been updated to animadvert the crops in criterions and technology that possess occurred since the notification of the seventh edition. ACKNOWLEDGMENTS This new edition has benefited from revisal by a reckon of commonalty, who gave generously of their season and expertise. The forthcomingcited commonalty revisaled all or a inclusive distribute of the manuscript: Xin Liu- (UC, Davis), Jorge Cobb, Andras Farago, Dr. Prasant Mohapatra (UC Davis), Dr. Jingxian Wu (Sonoma Propound University), G. R. Dattareya (UT Dallas), Guanling Chen (Umass, Lowell), Bob Roohaprvar (Cal Propound East Bay), Ahmed Banafa (Cal Propound East Bay), Ching-Chen Lee (CSU Hayward), and Daji Qaio (Iowa State). Thanks besides to the numerous commonalty who contributed inferential technical revisals of a uncompounded paragraph: Dave Tweed, Bruce Lane, Denis McMahon, Charles Freund, Paul Hoadley, Stephen Ma, Sandeep Subramaniam, Dragan Cvetkovic, Fernando Gont, Neil Giles, Rajesh Thundil, and Rick Jones. In peculiaration, Larry Owens of California Propound University and Katia Obraczka of the University of Southern California contributed some abodeemployment problems. Thanks besides to the forthcomingcited contributors. Zornitza Prodanoff of the University of North Florida alert the epilogue on Sockets programming. Michael Harris of the University of South Florida is obligatory for the Ethereal exercises and user’s direct. Lawrie Brown of the Australian Defence Force Academy of the University of New South Wales upshoted the PPT Nursing Dissertation slides. Finally, I would love to thank the numerous commonalty obligatory for the notification of the bulk, all of whom did their habitual praiseworthy job. This beneathstands the staff at Prentice Hall, distributeicularly my editor Tracy Dunkelberger, her assistants Christianna Lee and Carole Snyder, and employmention supervisor Rose Kernan. Also, Patricia M. Daly did the observation editing. CHAPTER READER’S AND INSTRUCTOR’S GUIDE 0. 1 0. 2 0. 3 0. 4 Outdirection of the Bulk Roadmap Internet and Web Resources Standards 0 1 2 CHAPTER 0 / READER’S AND INSTRUCTOR’S GUIDE “In the meanwhile, then,” insisted Li-loe, “rehearse to me the anecdote to which regard has been made, thereby proving the faithfulness of your assumption, and at the similar season affording n relief of a distributeially abnormal peel. ” “The shadows stretch-out,” replied Kai Lung, “but as the fact in doubt is of an indistinctive p I conciliate erect no distribution opposing your obsequious ask, distinctly as it indicates an awakening sensibility hitherto unforeseen. ” —Kai Lung’s Golden Hours, Earnest Bramah This bulk, retreat its obligatory Web birth, cloaks a lot of esthetic. Close we bestow the acknowledgeer some basic setting advice. 0. 1 OUTLINE OF THE BOOK The bulk is arranged into five distributes: Distribute One. Overview: Provides an insertion to the ramble of themes cloaked in the bulk. This distribute beneathstands a open balanceend of grounds intimations and netinstituted and a displan of protocols, OSI, and the TCP/IP protocol escort. Distribute Two. Grounds Communications: Concerned chiefly retreat the substitute of grounds betwixt two quickly united expedients. Unformed this esoteric delineateing, the key exposures of transmission, interfacing, incorporebuke manage, and multiplexing are examined. Distribute Three. Distant Area Networks: Examines the inner mechanisms and user-netemployment interfaces that possess been familiar to assistance utterance, grounds, and multiinstrument intimations balance desire-separation networks. The castted technologies of packet switching and circumference switching are examined, as courteous as the erect new ATM and wireclose WANs. Separebuke paragraphs are loving to routing and congeries manage issues that are expend twain to switched grounds networks and to the Internet. Distribute Four. Persomal Area Networks: Explores the technologies and erections that possess been familiar for netinstituted balance shorter separations. The transmission instrument, topologies, and average beamelody manage protocols that are the key ingredients of a LAN plan are proved and persomal criterionized LAN methods examined. Part Five. Netinstituted Protocols: Explores twain the architectural principles and the mechanisms claimd for the substitute of grounds unformed parliamentuters, employmentstations, attendrs, and other grounds methoding expedients. Plenteous of the esthetic in this distribute rehearses to the TCP/IP protocol escort. Distribute Six. Internet Applications: Looks at a ramble of contacts that upshot balance the Internet. A erect inferential, paragraph-by-paragraph abstract of each distribute answers at the rise of that distribute. 0. 2 / ROADMAP 3 0. 2 ROADMAP Way Emphasis The esthetic in this bulk is arranged into indelicate indelicate categories: grounds transmission and intimation; intimations networks; netemployment protocols; and contacts and pledge. The paragraphs and distributes of the bulk are sufficiently modular to contribute a parliamentact negotiate of flexibility in the plan of ways. The forthcomingcited are suggestions for three opposed way plans: • Fundamentals of Grounds Communications: Magnitude One (overview) and Two (grounds intimations) and Chapters 10 and 11 (circumference switching, packet switching, and ATM). Communications Networks: If the ward has a basic setting in grounds intimations, then this way could cloak Magnitude One (overview), Three (WAN), and Indelicate (LAN). • Computer Networks: If the ward has a basic setting in grounds intimations, then this way could cloak Distribute One (overview), Chapters 6 and 7 (grounds intimation techniques and grounds incorporebuke manage), Distribute Five (protocols), and distribute or all of Distribute Six (applications). In peculiaration, a erect driftlined way that cloaks the solid bulk is potential by eliminating convinced paragraphs that are not qualitative on a haughtyest balbutiation. Chapters that could be optional are Chapters 3 (grounds transmission) and 4 (transmission instrument), if the ward has a basic brains of these themes; Paragraph 8 (multiplexing); Paragraph 9 (circulate spectrum); Chapters 12 through 14 (routing, congeries manage, cellular networks); Paragraph 18 (internetworking); and Paragraph 21 (netemployment pledge). Bottom-Up versus Top-Down The bulk is arranged in a modular shape. Forthhereafter balbutiation Distribute One, the other distributes can be acknowledge in a reckon of potential posterioritys. Figure 0. 1a shows the bottom-up way contributed by balbutiation the bulk from front to tail. Retreat this way, each distribute establishs on the esthetic in the shapeer distribute, so that it is constantly disentangled how a bestown flake of functionality is assistanceed from adown. Tclose is erect esthetic than can be comfortably cloaked in a uncompounded semester, but the bulk’s outcome converges it unconcerned to eject some paragraphs and detain the bottom-up posteriority. Figure 0. 1b suggests one way to a revisal way. Some acknowledgeers, and some professors, are erect agreetelling retreat a top-down way. Forthhereafter the setting esthetic (Part One), the acknowledgeer endures at the contact flatten and employments down through the protocol flakes. This has the utility of presently centreing on the most clear distribute of the esthetic, the contacts, and then end, progressively, how each flake is assistanceed by the instant flake down. Figure 0. 1c is an observation of a parliamentendious quotationure and Figure 0. 1d is an observation of a revisal quotationure. 4 CHAPTER 0 / READER’S AND INSTRUCTOR’S GUIDE Part One Overend Distribute Two Grounds Communications Distribute Three Distant Area Networks Distribute Indelicate Persomal Area Networks Distribute Five Internet and Transport Protocols Distribute Six Internet Applications (a) A bottom-up way Distribute One Overend Paragraph 18 The Internet Protocol Distribute Six Internet Applications Distribute Five TCP/IP Distribute Three WANs Distribute Indelicate LANs Distribute Two Grounds Communications (c) A top-down way (d) Another top-down way (b) Another bottom-up way Distribute One Overend Paragraph 18 The Internet Protocol Distribute Six Internet Applications Distribute Five TCP/IP Distribute Three WANs (10, 12) Distribute Indelicate LANs (15) Distribute One Overend (1, 2) Distribute Two Grounds Communications (3, 6, 7, 8) Distribute Three WANs (10, 12) Distribute Indelicate LANs (15) Distribute Five TCP/IP (18, 20) Figure 0. 1 Suggested Balbutiation Orders Finally, it is potential to severedded paragraphs to animadvert persomal indoctrinateing extrinsics by not sticking to a exact paragraph ordering. We bestow two observations used in ways taught retreat the seventh edition. One way used the posteriority Distribute One (Overview); Paragraph 3 (Data Transmission); Paragraph 6 (Digital Grounds Communications Techniques); Paragraph 7 (Data Incorporebuke Control); Paragraph 15 (LAN Overview); Paragraph 16 (High-Speed LANs); Paragraph 10 (Circuit and Packet Switching); Paragraph 12 (Routing); Paragraph 18 (Internet Protocols); and Paragraph 19 (Internet Operation). The other way used the posteriority Distribute One (Overview); Paragraph 3 (Data Transmission); Paragraph 4 (Guided and Wireclose Transmission); Paragraph 5 (Signal Encoding Techniques); Paragraph 8 (Multiplexing); Paragraph 15 (LAN 0. 3 / INTERNET AND WEB RESOURCES 5 Overview); Paragraph 16 (High-Speed LANs); Paragraph 10 (Circuit and Packet Switching); Paragraph 20 (Transport Protocols); Paragraph 18 (Internet Protocols); and Paragraph 19 (Internet Operation). 0. 3 INTERNET AND WEB RESOURCES Tclose are a reckon of resources conducive on the Internet and the Web to assistance this bulk and to acceleration one obey up retreat crops in this arena. Web Sites for This Bulk A exceptional Web page has been set up for this bulk at WilliamStallings. com/DCC/ DCC8e. html. See the two-page layout at the rise of this bulk for a inferential schemeation of that birth. As before-desire as any typos or other fallacys are discovered, an errata inventory for this bulk conciliate be conducive at the Web birth. Please intimation any fallacys that you dishonor. Errata fencings for my other bulks are at WilliamStallings. com. I besides detain the Computer Comprehension Ward Rebeginning Site, at WilliamStallings. com/StudentSupport. html. The delineation of this birth is to contribute documents, advice, and incorporates for parliamentuter parliamentrehension wards and administratives. Links and documents are arranged into indelicate categories: • Math: Includes a basic math refresher, a queuing disexception primer, a reckon method primer, and incorporates to parliamentact math births • How-to: Advice and direction for solving abodeemployment problems, congruity technical intimations, and prepamelody technical presentations • Scrutiny resources: Links to esthetic collections of papers, technical intimations, and bibliographies • Miscellaneous: A miscellany of benefittelling documents and incorporates Other Web Sites Tclose are parliamentact Web births that contribute advice cognate to the themes of this bulk. In subjoined paragraphs, subject-matterers to persomal Web births can be base in the Recommended Balbutiation and Web Sites singularity. Accordingly the addresses for Web births aid to exsubstitute constantly, I possess not beneathstandd URLs in the bulk. For all of the Web births inventoryed in the bulk, the expend incorporebuke can be base at this bulk’s Web birth. Other incorporates not mentioned in this bulk conciliate be acquired to the Web birth balance season. The forthcomingcited are Web births of open concern cognate to grounds and parliamentuter intimations: • Netemployment World: Advice and incorporates to resources encircling grounds intimations and networking. • IETF: Maintains chronicles that rehearse to the Internet and IETF activities. Includes keyword-indexed library of RFCs and drain documents as courteous as numerous other documents cognate to the Internet and cognate protocols. 6 CHAPTER 0 / READER’S AND INSTRUCTOR’S GUIDE • Vendors: Links to thousands of rigorousware and software vendors who runningly possess Web births, as courteous as a inventory of thousands of parliamentuter and netinstituted parliamentanies in a phone directory. • IEEE Communications Society: Good way to obey up on conferences, notifications, and so on. ACM Exceptional Concern Cluster on Communications (SIGCOMM): Good way to obey up on conferences, notifications, and so on. • Interdiplomatic Telecommunications Union: Contains a inventorying of ITU-T recommendations, plus advice on obtaining ITU-T documents in rigorous observation or on DVD. • Interdiplomatic Outcome for Standardization: Contains a inventorying of ISO criterions, plus advice on obtaining ISO documents in rigorous observation or on CD-ROM. • CommWeb: Links to vendors, tutorials, and other benefittelling advice. • CommsDesign: Lot of benefittelling profession, tutorials, and employment advice. A bit rigorous to expatiate, but rebukewhile. USENET Newsgroups A reckon of USENET newsgroups are loving to some exposure of grounds intimations, networks, and protocols. As retreat implicitly all USENET clusters, tclose is a haughty noise-to-eminent pertinency, but it is rebuke trialing to see if any converge your call-fors. The most expend are as follows: • parliament. dcom. lans, parliament. dcom. lans. misc: Open disquisitions of LANs • parliament. dcom. lans. ethernet: Covers Ethernet, Ethernet-love methods, and the IEEE 802. 3 CSMA/CD criterions • parliament. std. wireless: Open displan of wireclose networks, including wireclose LANs • parliament. pledge. misc: Computer pledge and encryption • parliament. dcom. cell-relay: Covers ATM and ATM LANs • parliament. dcom. mould-relay: Covers mould refreshment networks • parliament. dcom. net-management: Displan of netemployment administration contacts, protocols, and criterions • parliament. rotocols. tcp-ip: The TCP/IP protocol escort 0. 4 STANDARDS It has desire been sanctioned in the telecommunications assiduity that criterions are claimd to manage the embodied, electrical, and procedural characteristics of intimation equipment. In the spent, this end has not been embraced by the parliamentuter assiduity. Whereas intimation equipment vendors acknowledge that their 0. 4 / STANDARDS 7 equipment conciliate openly interface to and divulge retreat other vendors’ equipment, parliamentuter vendors possess casttedly tryed to monopolize their customers. The proliferation of parliamentuters and reserved methoding has made that an untstrengthen lie. Computers from opposed vendors must divulge retreat each other and, retreat the ongoing separation of protocol criterions, customers conciliate no desireer sanction exceptional-delineation protocol substitute software crop. The upshot is that criterions now soak all of the areas of technology discussed in this bulk. Tclose are a reckon of utilitys and hindrances to the criterions-making method. We inventory close the most affecting ones. The main utilitys of criterions are as follows: • A criterion advises that tclose conciliate be a inclusive bargain for a distributeicular concern of equipment or software. This encourages lump employmention and, in some occurrences, the use of inclusive-scale-integration (LSI) or very-large-scale-integration (VLSI) techniques, upshoting in inferior costs. A criterion concedes employments from multiple vendors to divulge, giving the purchaser erect flexibility in equipment severeddion and use. The main hindrances are as follows: • A criterion aids to unconditionalze the technology. By the season a criterion is familiar, doubted to revisal and parliamentromise, and promulgated, erect fertile techniques are potential. • Tclose are multiple criterions for the similar object. This is not a disutility of criterions per se, but of the running way objects are executed. Fortunately, in new years the opposed criterions-making outcomes possess begun to coupshot erect closely. Nevertheless, tclose are sprepare areas wclose multiple irreconciltelling criterions be. Throughout this bulk, we dramatize the most esthetic criterions in use or substance familiar for opposed exposures of grounds and parliamentuter intimations. Opposed outcomes possess been conceived in the crop or advancement of these criterions. The forthcomingcited are the most esthetic (in the running subject) of these outcomes: • Internet Society: The Internet SOCiety (ISOC) is a administrative affinity sociality retreat erect than 150 outcomeal and 6000 singular members in balance 100 countries. It contributes commencement in addressing issues that oppose the forthhereafter of the Internet and is the outcome abode for the clusters obligatory for Internet infraoutcome criterions, including the Internet Engineemelody Task Force (IETF) and the Internet Erection Consideration (IAB). All of the RFCs and Internet criterions are familiar through these outcomes. • IEEE 802: The IEEE (Institute of Electrical and Electronics Engineers) 802 LAN/MAN Standards Committee develops persomal area netemployment criterions and metropolitan area netemployment criterions. The most distantly used criterions are for the Ethernet directionage, wireclose LAN, bridging, and implicit bridged LANs. An singular employmenting cluster contributes the centre for each area. 8 CHAPTER 0 / READER’S AND INSTRUCTOR’S GUIDE • ITU-T: The Interdiplomatic Teleintimation Union (ITU) is an interdiplomatic outcome retreatin the United Nations Method wclose administrations and the secret sector coordinate global telecom networks and benefits. The ITU Teleintimation Standardization Sector (ITU-T) is one of the three sectors of the ITU. ITU-T’s mission is the employmention of criterions cloaking all arenas of telecommunications. • ATM Forum: The ATM Forum is an interdiplomatic nonprofit outcome moulded retreat the extrinsic of accelerating the use of ATM (incontemporaneous transplant method) employments and benefits through a stserviceable assembly of interoperjurisdiction persomalations. In peculiaration, the Forum promotes assiduity coinfluence and awareness. • ISO: The Interdiplomatic Outcome for Standardization (ISO)1 is a cosmos-peopledistant federation of social criterions bodies from erect than 140 countries, one from each kingdom. ISO is a nongovernmental outcome that promotes the crop of criterionization and cognate activities retreat a end to facilitating the interdiplomatic substitute of commodities and benefits, and to developing coinfluence in the spheres of psychological, philosophical, technological, and economic distillation. ISO’s employment upshots in interdiplomatic agreements that are published as Interdiplomatic Standards. A erect inferential displan of these outcomes is incloseed in Epilogue D. 1 ISO is not an acronym (in which occurrence it would be IOS), but a order, partial from the Greek, aim correspondent. PART ONE Overend The delineation of Distribute One is to contribute a setting and conquotation for the relics of this bulk. The indelicate ramble of themes that are encompassed in the arena of grounds and parliamentuter intimations is introduced, and the primary concepts of protocols and protocol erections are examined. ROAD MAP FOR PART ONE Paragraph 1 Grounds Communications, Grounds Networks, and The Internet Paragraph 1 contributes an balanceend of Magnitude Two through Indelicate of the bulk, giving the “big delineate. ” In substance, the bulk negotiates retreat indelicate themes: grounds intimations balance a transmission incorporate; distant area networks; persomal area networks; and protocols and the TCP/IP protocol erection. Paragraph 1 contributes a previsal of the haughtyest three of these themes. Paragraph 2 Protocol Architecture, TCP/IP, and Internet-Based Applications Paragraph 2 discusses the concept protocol erections. This paragraph can be acknowledge presently forthcomingcited Paragraph 1 or plentiful until the rise of Distribute Three, Four, or Five. After a open insertion, the paragraph negotiates retreat the two most esthetic protocol erections: the Open Systems Interassociation (OSI) methodl and TCP/IP. Although the OSI methodl is numerously used as the mouldemployment for disway in this area, it is the TCP/IP protocol escort that is the plea for most retailly conducive interopertelling employments and that is the centre of Magnitude Five and Six of this bulk. 9 CHAPTER DATA COMMUNICATIONS, DATA NETWORKS, AND THE INTERNET 1. 1 1. 2 1. 3 1. 4 1. 5 1. 6 Grounds Communications and Netinstituted for Today’s Act A Communications Type Grounds Communications Networks The Internet An Observation Configuration 1 10 The primary problem of intimation is that of reproducing at one subject-subject either correspondently or closely a intimation severedded at another subject-matter. The Mathematical Theory of Communication, Claude Shannon KEY POINTS • The delineateing of this bulk is indelicate, cloaking three open areas: grounds intimations, networking, and protocols; the haughtyest two are introduced in this paragraph. Grounds intimations negotiates retreat the transmission of eminents in a rebiased and fertile method. Topics cloaked beneathstand eminent transmission, transmission instrument, eminent encoding, interfacing, grounds incorporebuke manage, and multiplexing. Netinstituted negotiates retreat the technology and erection of the intimations networks used to interconnect communicating expedients. This arena is openly severedd into the themes of persomal area networks (LANs) and distant area networks (WANs). • • The 1970s and 1980s saw a merger of the arenas of parliamentuter parliamentrehension and grounds intimations that profoundly exnewfangled the technology, employments, and parliamentanies of the now in-one parliamentuter-communications assiduity. The parliamentutercommunications rseparation has upshoted incongruous observtelling facts: • Tclose is no primary disagreement betwixt grounds methoding (computers) and grounds intimations (transmission and switching equipment). • Tclose are no primary disagreements unformed grounds, utterance, and video intimations. • The separation unformed uncompounded-processor parliamentuter, multiprocessor parliamentuter, persomal network, metropolitan network, and desire-haul netemployment has blurred. One upshot of these tends has been a growing balancelap of the parliamentuter and intimations industries, from content spurious to method integration. Another upshot is the crop of integrated methods that cast and method all expressions of grounds and advice. Twain the technology and the technical criterions outcomes are driving toward integrated openly-known methods that converge implicitly all grounds and advice beginnings encircling the cosmos-people easily and unintermittently bearingible. This bulk boon to contribute a unified end of the indelicate arena of grounds and parliamentuter intimations. The outcome of the bulk animadverts an try to curb this weighty doubt into plain distributes and to establish, concern by concern, a revisal of the propound of the art. This precursory paragraph initiates retreat a open methodl of intimations. Then a scanty displan introduces each of the Magnitude Two through Indelicate of this bulk. Paragraph 2 contributes an balanceend to Magnitude Five and Six 11 12 CHAPTER 1 / DATA COMMUNICATIONS, DATA NETWORKS, AND THE INTERNET 1. 1 DATA COMMUNICATIONS AND NETWORKING FOR TODAY’S ENTERPRISE Effective and fertile grounds intimation and netinstituted facilities are life-containing to any act. In this singularity, we haughtyest contemplate at tends that are increasing the brave for the affair supervisor in planning and managing such facilities. Then we contemplate persomalally at the limitation for always-esthetic transmission expedites and netemployment parts. Trends Three opposed forces possess accordingly driven the erection and separation of grounds intimations and netinstituted facilities: interprogress enlargement, crop of new benefits, and advances in technology. Intimation intercourse, twain persomal (unformed a establishing or establishing parliamentlex) and desire separation, twain utterance and grounds, has been growing at a haughty and regular rebuke for decades. The increasing pith on station automation, foreign bearing, ondirection transactions, and other employmentivity measures instrument that this tend is lovely to endure. Thus, supervisors are eternally struggling to maximize parts and minimize transmission costs. As affaires exist erect and erect on advice technology, the ramble of benefits diffuses. This extensions the insist for haughty-parts netinstituted and transmission facilities. In revolve, the definiteing enlargement in haughty-expedite netemployment exhibitings retreat the definiteing percolate in prices encourages the expansion of benefits. Thus, enlargement in benefits and enlargement in interprogress parts go index in index. Figure 1. 1 bestows some observations of advice-based benefits and the grounds rebukes call-fored to assistance them [ELSA02]. Finally, tends in technology strengthen the supplies of increasing interprogress parts and the assistance of a distant ramble of benefits. Indelicate technology tends are distributeicularly notable: 1. The tend toward faster and cheaper, twain in parliamentuting and intimations, endures. In conditions of parliamentuting, this instrument erect strong parliamentuters and clusters of parliamentuters captelling of assistanceing erect insisting contacts, such as multiinstrument contacts. In conditions of intimations, the increasing use of optical fiber has brought transmission prices down and parliamentactly extensiond parts. For observation, for desire-separation teleintimation and grounds netemployment incorporates, new exhibitings of solid wavelength opposition multiplexing (DWDM) strengthen capacities of numerous terabits per promote. For persomal area networks (LANs) numerous acts now possess Gigabit Ethernet tailbone networks and some are rise to deploy 10-Gbps Ethernet. 2. Twain utterance-oriented telecommunications networks, such as the openly-known switched telephone netemployment (PSTN), and grounds networks, including the Internet, are erect “intelligent” than always. Two areas of rumor are unusual. First, today’s networks can exhibit diffemelody flattens of attribute of benefit (QoS), which beneathstand persomalations for consummation retreat, narrowness throughput, and so on. Second, today’s networks contribute a miscellany of customiztelling benefits in the areas of netemployment administration and pledge. 1. 1 / DATA COMMUNICATIONS AND NETWORKING FOR TODAY’S ENTERPRISE Expedite (kbps) Transaction methoding Messaging/quotation apps Utterance Location benefits Sprepare dramatizeation transplants Internet/VPN beamelody Database beamelody Enhanced Web surfing Low-attribute video Hifi audio Inclusive smooth transplant Moderebuke video Interactive relief High-attribute video Performance: Poor Adequate Good 9. 6 14. 4 28 64 144 384 2000 13 VPN: implicit secret netemployment Figure 1. 1 Services versus Throughput Rates 3. The Internet, the Web, and associated contacts possess emerged as dominant features of twain the affair and indivisible cosmos-people, aperture up numerous opportunities and braves for supervisors. In peculiaration to feating the Internet and the Web to grasp customers, suppliers, and distributeners, acts possess moulded intranets and extranets1 to insulate their proprietary advice unconditional from unwanted bearing. 4. Tclose has been a tend toward always-increasing restlessness for decades, liberating employmenters from the precincts of the embodied act. Innovations beneathstand utterance mail, foreign grounds bearing, pagers, fax, e-mail, cordclose phones, cell phones and cellular networks, and Internet portals. The upshot is the jurisdiction of employees to catch their affair conquotation retreat them as they agitate encircling. We are now end the enlargement of haughty-expedite wireclose bearing, which erect enhances the jurisdiction to use act advice resources and benefits anywhere. 1 Briefly, an intranet uses Internet and Web technology in an insulated readiness inner to an act; an extranet extends a parliamentany’s intranet out onto the Internet to concede severedded customers, suppliers, and fickle employmenters to beamelody the parliamentany’s secret grounds and contacts. 14 CHAPTER 1 / DATA COMMUNICATIONS, DATA NETWORKS, AND THE INTERNET Grounds Transmission and Netemployment Parts Requirements Momentous substitutes in the way outcomes do affair and method advice possess been driven by substitutes in netinstituted technology and at the similar season possess driven those substitutes. It is rigorous to separebuke chicken and egg in this arena. Similarly, the use of the Internet by twain affaires and singulars animadverts this cyclic existency: the availjurisdiction of new dramatizeation-based benefits on the Internet (i. e. , the Web) has upshoted in an extension in the completion reckon of users and the interprogress lump generated by each user. This, in revolve, has upshoted in a call-for to extension the expedite and competency of the Internet. On the other index, it is merely such extensiond expedite that converges the use of Web-based contacts tasteful to the end user. In this singularity, we revisal some of the end-user factors that fit into this equation. We initiate retreat the call-for for haughty-expedite LANs in the affair environment, accordingly this call-for has answered haughtyest and has unfeeling the gait of netinstituted crop. Then we contemplate at affair WAN limitations. Finally we exhibit a few orders encircling the upshot of substitutes in retail electronics on netemployment limitations. The Emergence of High-Speed LANs Indivisible parliamentuters and microcomputer employmentstations began to close distantcirculate sanctionance in affair parliamentuting in the hereafter 1980s and possess now closed implicitly the standing of the telephone: an qualitative implement for station employmenters. Until proportionately newly, station LANs contributed basic connectivity benefits—connecting indivisible parliamentuters and messageinals to mainframes and midramble methods that ran corporebuke contacts, and providing employmentcluster connectivity at the departmental or oppositional flatten. In twain occurrences, interprogress patterns were proportionately unsteady, retreat an pith on smooth transplant and electronic mail. The LANs that were conducive for this expression of employmentload, chiefly Ethernet and demonstration melody, are courteous escortd to this environment. In the 1990s, two speaking tends altered the role of the indivisible parliamentuter and consequently the limitations on the LAN: 1. The expedite and parliamentuting jurisdiction of indivisible parliamentuters endured to relish explosive enlargement. These erect strong platforms assistance drawsquelys-intensive contacts and always erect elaborebuke drawsquelyal user interfaces to the permitted method. . MIS (administration advice methods) outcomes possess acknowledged the LAN as a vitelling and qualitative parliamentuting platform, upshoting in the centre on netemployment parliamentuting. This tend began retreat client/server parliamentuting, which has beconclude a dominant erection in the affair environment and the erect new Webfocused intranet tend. Twain of these wayes conceive the numerous transplant of hypothetically inclusive lumps of grounds in a transaction-oriented environment. The upshot of these tends has been to extension the lump of grounds to be indexled balance LANs and, accordingly contacts are erect interactive, to classify the sanctiontelling retreat on grounds transplants. The prior breed of 10-Mbps Ethernets and 16-Mbps demonstration melodys was merely not up to the job of assistanceing these limitations. The forthcomingcited are observations of limitations that call for haughtyer-expedite LANs: • Centralized attendr farms: In numerous contacts, tclose is a call-for for user, or client, methods to be telling to delineate immense entiretyitys of grounds from multiple centralized attendrs, named attendr farms. An observation is a pretense publishing influence, in 1. 1 / DATA COMMUNICATIONS AND NETWORKING FOR TODAY’S ENTERPRISE 15 which attendrs normally inclose tens of gigabytes of dramatizeation grounds that must be downloaded to imaging employmentstations. As the deed of the attendrs themselves has extensiond, the bottleneck has transfered to the network. Jurisdiction employmentgroups: These clusters normally continue of a slender reckon of copermitted users who call-for to delineate weighty grounds smooths oppopost the network. Examples are a software crop cluster that runs tests on a new software statement, or a parliamentuter-aided plan (CAD) parliamentany that constantly runs airss of new plans. In such occurrences, inclusive entiretyitys of grounds are reserved to incongruous employmentstations, methoded, and updated at very haughty expedite for multiple iterations. • High-expedite persomal tailbone: As methoding insist grows, LANs proliferebuke at a birth, and haughty-expedite interassociation is compulsory. Corporebuke Distant Area Netinstituted Needs As newly as the hereafter 1990s, tclose was an pith in numerous outcomes on a centralized grounds methoding methodl. In a normal environment, tclose administration be speaking parliamentuting facilities at a few regional stations, continueing of mainframes or courteous-equipped midramble methods. These centralized facilities could indexle most corporebuke contacts, including basic finance, accounting, and personnel programs, as courteous as numerous of the affair-persomal contacts. Smaller, rural stations (e. g. , a bank sprig) could be equipped retreat messageinals or basic indivisible parliamentuters incorporateed to one of the regional centers in a transaction-oriented environment. This methodl began to exsubstitute in the hereafter 1990s, and the exsubstitute stserviceable through the mid-1990s. Numerous outcomes possess profusely their employees into multiple slenderer stations. Tclose is a growing use of telecommuting. Most speaking, the truth of the contact outcome has substituted. Highest client/server parliamentuting and, erect newly, intranet parliamentuting possess primaryly restructured the outcomeal grounds methoding environment. Tclose is now plenteous erect trust on indivisible parliamentuters, employmentstations, and attendrs and plenteous close use of centralized mainmould and midramble methods. Furthermore, the implicitly comprehensive deployment of drawsquelyal user interfaces to the desktop strengthens the end user to feat drawsquely contacts, multimedia, and other grounds-intensive contacts. In peculiaration, most outcomes claim beamelody to the Internet. When a few clicks of the mouse can trigger immense lumps of grounds, interprogress patterns possess beconclude erect unpredicttelling opportunity the mean carry has erect. All of these tends instrument that erect grounds must be transported off ground and into the distant area. It has desire been sanctioned that in the normal affair environment, encircling 80% of the interprogress recrement persomal and encircling 20% traverses distant area incorporates. But this administration no desireer applies to most parliamentanies, retreat a esthetic percentage of the interprogress going into the WAN environment [COHE96]. This interprogress career transfer places a esthetic lot on LAN tailbones and, of way, on the WAN facilities used by a fortification. Thus, normal as in the persomal area, substitutes in corporebuke grounds interprogress patterns are driving the falsehood of haughty-expedite WANs. Digital Electronics The stserviceable substitute of consumer electronics to digital technology is having an contact on twain the Internet and corporebuke intranets. As these new gadgets conclude into end and proliferate, they dramatically extension the entiretyity of dramatizeation and video interprogress carried by networks. Two unusual observations of this tend are digital unsteady disks (DVDs) and digital sprepare cameras. Retreat the comprehensive DVD, the electronics assiduity has at definite 16 CHAPTER 1 / DATA COMMUNICATIONS, DATA NETWORKS, AND THE INTERNET base an sanctiontelling restitution for the analog VHS videotape. The DVD has replaced the videotape used in videocassette recorders (VCRs) and replaced the CD-ROM in indivisible parliamentuters and attendrs. The DVD catchs video into the digital age. It delivers movies retreat delineate attribute that outshines laser disks, and it can be randomly bearinged love audio CDs, which DVD machines can besides play. Vast lumps of grounds can be crammed onto the disk, runningly seven seasons as plenteous as a CDROM. Retreat DVD’s immense storage parts and graphic attribute, PC games possess beconclude erect realistic and adviceal software incorporates erect video. Aftercited in the call of these crops is a new bead of interprogress balance the Internet and corporebuke intranets, as this esthetic is incorporated into Web births. A cognate employment crop is the digital camcorder. This employment has made it easier for singulars and parliamentanies to converge digital video smooths to be placed on corporebuke and Internet Web births, frequently adding to the interprogress lot. 1. 2 A COMMUNICATIONS MODEL This singularity introduces a lowly methodl of intimations, imaginative by the obstruct diagram in Figure 1. 2a. The primary delineation of a intimations method is the substitute of grounds betwixt two distributeies. Figure 1. 2b presents one distributeicular observation, which is intimation betwixt a employmentstation and a attendr balance a openly-known telephone network. Another observation is the substitute of utterance eminents betwixt two telephones balance the similar network. The key atoms of the methodl are as follows: • Source. This expedient generates the grounds to be castted; observations are telephones and indivisible parliamentuters. Beginning method Appointment method Beginning Transmitter Transmission Method (a) Open obstruct diagram Receiver Appointment Workstation Modem Generally-known telephone netemployment (b) Observation Modem Server Figure 1. 2 Simplified Communications Type 1. 2 / A COMMUNICATIONS MODEL 17 • Transmitter: Usually, the grounds generated by a beginning method are not castted quickly in the mould in which they were generated. Rather, a castter transforms and encodes the advice in such a way as to outcome electromagnetic eminents that can be castted oppopost some kind of transmission method. For observation, a methodm catchs a digital bit drift from an attached expedient such as a indivisible parliamentuter and transforms that bit drift into an analog eminent that can be indexled by the telephone network. • Transmission method: This can be a uncompounded transmission direction or a parliamentlex netemployment connecting beginning and appointment. • Receiver: The receiver sanctions the eminent from the transmission method and alters it into a mould that can be indexled by the appointment expedient. For observation, a methodm conciliate sanction an analog eminent hereafter from a netemployment or transmission direction and alter it into a digital bit drift. • Destination: Takes the inhereafter grounds from the receiver. This lowly fact conceals a mammon of technical parliamentlexity. To get some subject of the delineateing of this parliamentlexity, Ttelling 1. 1 inventorys some of the key tasks that must be effected in a grounds intimations method. The inventory is distributeially arbitrary: Elements could be acquired; parts on the inventory could be merged; and some parts dramatize incongruous tasks that are effected at opposed “levels” of the method. However, the inventory as it stands is postulatory of the delineateing of this bulk. The haughtyest part, transmission method utilization, refers to the call-for to converge fertile use of transmission facilities that are normally shared unformed a reckon of communicating expedients. Various techniques (referred to as multiplexing) are used to arrange the completion parts of a transmission average unformed a reckon of users. Congeries manage techniques may be claimd to advise that the method is not balancewhelmed by inordinate insist for transmission benefits. To divulge, a expedient must interface retreat the transmission method. All the moulds of intimation discussed in this bulk exist on the use of electromagnetic eminents propagated balance a transmission average. Thus, uninterruptedly an interface is customary, eminent breed is claimd for intimation. The properties of the eminent, such as mould and eagerness, must be such that the eminent is (1) captelling of substance propagated through the transmission method, and (2) interprettelling as grounds at the receiver. Not merely must the eminents be generated to conmould to the limitations of the transmission method and receiver, but besides tclose must be some mould of synchronization Ttelling 1. 1 Communications Tasks Transmission method utilization Interfacing Eminent breed Synchronization Substitute administration Fallacy counteraction and punishment Career manage Addressing Routing Recovery Intimation mouldatting Pledge Netemployment administration 18 CHAPTER 1 / DATA COMMUNICATIONS, DATA NETWORKS, AND THE INTERNET betwixt castter and receiver. The receiver must be telling to indicate when a eminent initiates to attain and when it ends. It must besides beneathstand the space of each eminent atom. Beyond the basic subject of deciding on the truth and timing of eminents, tclose is a miscellany of limitations for intimation betwixt two distributeies that administration be self-possessed beneath the message substitute administration. If grounds are to be substituted in twain inclinations balance a duration of season, the two distributeies must assist. For observation, for two distributeies to employ in a telephone converse, one distributey must dial the reckon of the other, causing eminents to be generated that upshot in the melodying of the named phone. The named distributey parliamentletes a association by lifting the receiver. For grounds methoding expedients, erect conciliate be call-fored than merely establishing a association; convinced conventions must be determined on. These conventions may beneathstand whether twain expedients may cast concertedly or must catch revolves, the entiretyity of grounds to be sent at one season, the mouldat of the grounds, and what to do if convinced contingencies such as an fallacy commence. The instant two parts administration possess been beneathstandd beneath substitute managem