Understanding Data Communications (Third Edition) Published Online: 05 Oct 2001 Author(s): Gilbert Held ISBN: 0470841486 (Electronic) 0471627453 (Print) Book Description: Now in its third edition, Understanding Data Comunications, provides a comprehensive introduction to the field of data communications for both students and professionals. Assuming no prior knowledge of the field, it presents an overview of the role of communications, their importance, and the fundamental concepts of using the ISO's 7-layer approach to present the various aspects of networking. · Covers the evolving high speed network access via digital subscriber line, cable modems and wireless communication. · Examines the role of regulatory and standardization bodies, the operation of the Internet and the use of a variety of electronic applications. Copyright © 2000 John Wiley & Sons, Ltd · Includes a series of comprehensive questions covering the important concepts from each section. · Describes the digital network used by communications carriers and the methods used to obtain access to the digital highway. · Discusses frequency division multiplexing which forms the foundation for the operation of several types of high speed digital subscriber line. Aimed at the senior level undergraduate and graduate computer science student, it is also essential reading for data processing professionals and those involved in computer science and data communications. Acknowledgements: Many thanks to iota@flyheart, who not only provided the related material but give me some advice and making-tips. Spornsored by: iota Made by: NutZ9 or NutFanZ May 14, 2003 Copyright © 2000 John Wiley & Sons, Ltd Understanding Data Communications: From Fundamentals to Networking. Third Edition Gilbert Held Copyright # 2000 John Wiley & Sons Ltd Print ISBN 0-471-627453 Online ISBN 0-470-84148-6 UNDERSTANDING DATA COMMUNICATIONS Understanding Data Communications: From Fundamentals to Networking. Third Edition Gilbert Held Copyright # 2000 John Wiley & Sons Ltd Print ISBN 0-471-627453 Online ISBN 0-470-84148-6 UNDERSTANDING DATA COMMUNICATIONS From Fundamentals to Networking Third Edition Gilbert Held 4-Degree Consulting Macon, Georgia, USA JOHN WILEY & SONS, LTD Chichester . NewYork . Weinheim . Brisbane . Singapore . Toronto 4 CHAPTER TITLE Copyright # 2000 by John Wiley & Sons, Ltd Baffins Lane, Chichester, West Sussex PO19 1UD, England National 01243 779777 International (þ44) 1243 779777 e-mail (for orders and customer service enquiries): [email protected] Visit our Home Page on http://www.wiley.co.uk or http://www.wiley.com Reprinted with corrections July 2001 All rights reserved. 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Title TK5105 .H429 1997 004.6 — dc20 00-032094 British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library ISBN 0 471627453 1 1 Typeset in 92/112pt Bookman by Aarontype Ltd, Easton, Bristol Printed and bound in Great Britain by Antony Rowe Ltd, Chippenham, Wiltshire. This book is printed on acid-free paper responsibly manufactured from sustainable forestry, in which at least two trees are planted for each one used for paper production. Understanding Data Communications: From Fundamentals to Networking. Third Edition Gilbert Held Copyright # 2000 John Wiley & Sons Ltd Print ISBN 0-471-627453 Online ISBN 0-470-84148-6 CONTENTS Preface xix Acknowledgements xxi 1 Communications in a Modern Society 1 1.1 Applications 1 1.1.1 Data collection 2 1.1.2 Transaction processing 3 1.1.3 Conversational time sharing 5 1.1.4 Remote job entry 7 1.1.5 Message switching 7 1.1.6 Value-added carriers and electronic mail 8 1.1.7 Office automation 12 1.1.8 Electronic commerce 14 1.1.9 Satellite transmission 16 1.2 Constraints 16 1.2.1 Throughput 17 1.2.2 Response time 18 1.2.3 Bandwidth 18 1.2.4 Economics 19 1.3 Emerging Trends 19 1.4 ReviewQuestions 20 2 Basic Telegraph and Telephone Operations 23 2.1 Evolution of Communications 23 2.2 Telegraphy 24 2.2.1 Operation 24 2.2.2 Morse code 26 2.2.3 Morse code limitations 27 2.2.4 Start–stop signaling and the Baudot code 28 2.2.5 Bits and codes 29 2.3 Telephony 32 2.3.1 Principle of operation 32 2.3.2 Sound wave conversion 34 2.3.3 The basic telephone connection 36 2.3.4 Switchboards and central offices 37 2.3.5 Numbering plans 39 2.3.6 Geographic calling areas and network routing 40 2.3.7 The world numbering plan 43 2.4 ReviewQuestions 43 vi CONTENTS 3Basic Circuit Parameters, Measurement Units and Media Overview 47 3.1 Basic Circuit Parameters 47 3.1.1 Frequency and bandwidth 47 3.1.2 The telephone channel passband 49 3.2 Measurement Units 50 3.2.1 Power ratios 50 3.2.2 Signal-to-noise ratio 52 3.2.3 Reference points 54 3.3 Media Overview56 3.3.1 Twisted-pair cable 56 3.3.2 Coaxial cable 61 3.3.3 Microwave 63 3.3.4 Fiber-optic transmission 64 3.4 Channel Capacity 67 3.4.1 Bit versus baud 67 3.4.2 Nyquist relationship 67 3.4.3 Shannon’s law68 3.5 Structured Wiring 69 3.5.1 The wiring closet 69 3.5.2 The EIA/TIA-568 standard 69 3.6 ReviewQuestions 72 4 Fundamental Data Transmission Concepts 75 4.1 Analog Line Connections 75 4.1.1 The analog switched line 76 4.1.2 Analog leased line 79 4.1.3 Dedicated line 82 4.1.4 Switched network vs leased line economics 83 4.2 Types of Service and Transmission Devices 84 4.2.1 Digital repeaters 85 4.2.2 Modems 86 4.2.3 Acoustic couplers 87 4.2.4 Analog facilities 89 4.2.5 Digital facilities 93 4.2.6 Digital signaling 93 4.2.7 Representative AT&T digital offerings 96 4.3 Transmission Mode 98 4.3.1 Simplex transmission 98 4.3.2 Half-duplex transmission 99 4.3.3 Full-duplex transmission 100 4.3.4 Terminal and mainframe computer operating modes 101 4.4 Transmission Techniques 103 4.4.1 Asynchronous transmission 103 4.4.2 Synchronous transmission 105 4.5 Types of Transmission 106 4.6 Wide Area Network Transmission Structures 107 4.6.1 Mainframe computer-based network structure 108 4.6.2 LAN network structure 109 4.6.3 LAN internetworking structure 110 4.7 Line Discipline 111 4.8 Transmission Rate 113 4.8.1 Analog service 113 4.8.2 Digital service 114 CONTENTS vii 4.9 Transmission Codes 115 4.9.1 Morse code 115 4.9.2 Baudot code 116 4.9.3 BCD code 116 4.9.4 Extended binary-coded decimal interchange code (EBCDIC) 116 4.9.5 ASCII code 118 4.10 ReviewQuestions 122 5 Terminals, Workstations and WAN and LAN Networking Overview 125 5.1 Terminals 126 5.1.1 Interactive terminal classification 126 5.1.2 Terminal evolution 127 5.2 Workstations and Other LAN Components 141 5.2.1 Network interface card 141 5.2.2 Hubs 142 5.2.3 File server 143 5.2.4 Print server 145 5.2.5 Other types of servers 146 5.3 Wide Area Networking Overview 146 5.3.1 Multiplexing and data concentration 146 5.3.2 Front-end processor 151 5.3.3 Network configurations 151 5.4 Local Area Networking Overview 152 5.4.1 Repeaters 153 5.4.2 Bridges 153 5.4.3 Routers 154 5.4.4 Gateways 155 5.5 ReviewQuestions 157 6 Representative Standards Organizations: the OSI Reference Model 159 6.1 National Standards Organizations 160 6.1.1 American National Standards Institute (ANSI) 160 6.1.2 Electronic Industries Association (EIA) 161 6.1.3 Federal Information Processing Standards (FIPS) 163 6.1.4 Institute of Electrical and Electronic Engineers (IEEE) 163 6.1.5 British Standards Institution (BSI) 164 6.1.6 Canadian Standards Association (CSA) 164 6.2 International Standards Organizations 164 6.2.1 International Telecommunications Union (ITU) 164 6.2.2