DATA COMMUNICATIONS AND COMPUTER NETWORKS Second Edition PRAKASH C. GUPTA Formerly Head Department of Information Technology Maharashtra Institute of Technology Pune Delhi-110092 2014
DATA COMMUNICATIONS AND COMPUTER NETWORKS, Second Edition Prakash C. Gupta 2014 by PHI Learning Private Limited, Delhi. All rights reserved. No part of this book may be reproduced in any form, by mimeograph or any other means, without permission in writing from the publisher. ISBN-978-81-203-4864-6 The export rights of this book are vested solely with the publisher. Eighth Printing (Second Edition) January, 2014 Published by Asoke K. Ghosh, PHI Learning Private Limited, Rimjhim House, 111, Patparganj Industrial Estate, Delhi-110092 and Printed by Rajkamal Electric Press, Plot No. 2, Phase IV, HSIDC, Kundli-131028, Sonepat, Haryana.
Contents Preface xxv 1 Data Communication Concepts and Terminology 1 34 1.1 Basic Model of Data Communication System 1 1.2 Data Representation 2 1.2.1 ASCII American Standard Code for Information Interchange 3 1.2.2 Byte 5 1.3 Data Transmission 5 1.3.1 Parallel Transmission 5 1.3.2 Serial Transmission 6 1.3.3 Bit Rate 7 1.3.4 Receiving Data Bits 7 1.4 Modes of Data Transmission 8 1.4.1 Asynchronous Transmission 9 1.4.2 Synchronous Transmission 10 1.5 Digital Signal Encoding 11 1.6 Unipolar and Polar Line Codes 12 1.6.1 Non Return to Zero (NRZ) Codes 12 1.6.2 Return to Zero (RZ) Codes 13 1.7 Bipolar Line Codes 14 1.7.1 Alternate Mark Inversion (AMI) 14 1.7.2 High Density Bipolar-3 Zeroes (HDB3) 14 1.7.3 Bipolar with 8 Zeroes Substitution (B8ZS) Code 15 1.8 Block Codes 15 1.9 Frequency Spectrum 16 1.9.1 Fourier Series 17 1.10 Transmission Channel 19 1.10.1 Bauds 20 1.10.2 Baseband Transmission 21 1.10.3 Modem 21 1.11 Data Compression 21 1.11.1 Information 22 1.11.2 Entropy 23 1.11.3 Redundancy 23 1.11.4 Encoding for Compression 25 1.11.5 Shannon-Fano Code 26 1.11.6 Huffman Code 26 iii
iv CONTENTS 1.12 Data Communication 29 1.12.1 Synchronous Communication 29 1.12.2 Asynchronous Communication 29 1.13 Directional Capabilities of Data Exchange 30 1.14 Line Configurations 30 Summary 31 Exercises 32 2 Transmission Media 35 64 2.1 Transmission Line Characteristics 35 2.1.1 Primary Parameters 35 2.1.2 Secondary Parameters 36 2.1.3 Phase Velocity and Phase Delay 36 2.1.4 Frequency Dependence of Secondary Parameters 37 2.2 Linear Distortions 38 2.2.1 Group Delay 39 2.2.2 Frequency Domain Equalizers 39 2.3 Characteristics of Transmission Line in Time Domain 40 2.4 Crosstalk 41 2.5 Logarithmic Units of Power Level Measurements 42 2.6 Metallic Transmission Media 43 2.6.1 Balanced Pair 43 2.6.2 Balanced Pair Cables 43 2.6.3 Loading of Balanced Pairs 44 2.6.4 Balanced Pair for Data Networks 45 2.6.5 Coaxial Cable 46 2.7 Optical Fibre 47 2.7.1 Multimode Fibres 47 2.7.2 Modal Dispersion 48 2.7.3 Monomode Fibre 49 2.7.4 Graded Index Fibres 49 2.7.5 Chromatic Dispersion 50 2.7.6 Total Dispersion 50 2.7.7 Fibre Attenuation 50 2.7.8 Advantages of Optical Fibre 51 2.8 Radio Media 51 2.8.1 Electromagnetic Spectrum 51 2.9 Baseband Transmission of Data Signals 52 2.9.1 First Nyquist Criterion 52 2.9.2 Second Nyquist Criterion 54 2.9.3 Channel Characteristic for Finite Duration Pulses 56 2.10 Equalization 56 2.10.1 Transversal Filter Equalizer 57 2.10.2 Adaptive Equalization 59
CONTENTS v 2.11 Clocked Regenerative Receiver 60 2.12 Eye Pattern 61 Summary 63 Exercises 63 3 Telephone Network 65 101 3.1 Telephone Network 65 3.1.1 Network Topology 65 3.1.2 Single Exchange Area 66 3.1.3 Multiple Exchanges 67 3.1.4 Trunk Automatic Exchanges 68 3.1.5 International Transit Exchange 69 3.2 Transport Network 69 3.2.1 Hybrids 70 3.2.2 Multiplexing 71 3.2.3 Pulse Code Modulation (PCM) 74 3.2.4 30-Channel PCM Signal 75 3.2.5 Plesiochronous Digital Hierarchy (PDH) 76 3.3 Synchronous Digital Hierarchy (SDH) 77 3.3.1 STM-1 Frame Structure 77 3.3.2 Virtual Container (VC) 79 3.3.3 VC-4 79 3.3.4 VC-12 80 3.3.5 Mapping of Data Signals on STM-1 81 3.3.6 Higher Order SDH Signals 82 3.4 Transmission Systems for Long Distance Network 83 3.5 Echo in Transmission Systems 84 3.6 Noise in Transmission Systems 85 3.6.1 Intermodulation Noise 86 3.6.2 Thermal and Shot Noise 87 3.6.3 Psophometric Weighting 88 3.6.4 Signal to Noise Ratio 88 3.6.5 Companders 89 3.7 Signal Impairments in the Telephone Network 91 3.7.1 Impulse Noise 91 3.7.2 Gain Hits and Dropouts 91 3.7.3 Phase Hits 92 3.7.4 Phase Jitter 92 3.7.5 Single Frequency Interference 92 3.7.6 Frequency Shift 92 3.8 Integrated Services Digital Network (ISDN) 93 3.8.1 ISDN Interface 93 3.8.2 ISDN Devices 94 3.8.3 Reference Interfaces 95
vi CONTENTS 3.8.4 BRA Frame Structure 96 3.8.5 Access Mechanism for D Channel in BRA 97 3.8.6 Data Transmission Mechanisms of ISDN 97 3.9 Data Communications on Telephone Network 97 3.9.1 300 3400 Hz Voice Channel Bandwidth 98 3.9.2 ISDN Services 98 3.9.3 Digital Point-to-Point Links 98 3.9.4 ITU-T Recommendations for Voice Band Leased Circuits 99 Summary 100 Exercises 101 4 Data Line Devices 102 152 4.1 Digital Modulation Methods 102 4.1.1 Amplitude Shift Keying (ASK) 103 4.1.2 Frequency Shift Keying (FSK) 104 4.1.3 Phase Shift Keying (PSK) 105 4.2 Multilevel Modulation 106 4.2.1 Gray Code 106 4.2.2 4 PSK Modulator 107 4.2.3 4 PSK Demodulator 108 4.3 Differential PSK 109 4.3.1 Differential BPSK 109 4.3.2 Differential 4 PSK 111 4.3.3 16 Quadrature Amplitude Modulation (QAM) 112 4.4 Modem 114 4.4.1 Types of Modems 115 4.4.2 Scrambler and Descrambler 117 4.4.3 Block Schematic of a Modem 119 4.4.4 Additional Modem Features 122 4.5 Standard Modems 125 4.5.1 ITU-T V.21 Modem 125 4.5.2 ITU-T V.22 Modem 126 4.5.3 ITU-T V.22bis Modem 126 4.5.4 ITU-T V.23 Modem 128 4.5.5 ITU-T V.26 Modem 128 4.5.6 ITU-T V.26bis Modem 128 4.5.7 ITU-T V.26ter Modem 129 4.5.8 ITU-T V.27 Modem 129 4.5.9 ITU-T V.27bis Modem 130 4.5.10 ITU-T V.27ter Modem 130 4.5.11 ITU-T V.29 Modem 130 4.5.12 ITU-T V.32 Modem 132 4.5.13 ITU-T V.33 Modem 134 4.5.14 ITU-T V.34 Modem 135 4.5.15 ITU-T V.90 Modem 135
CONTENTS vii 4.6 Other Modems and Line Drivers 135 4.6.1 Limited Distance Modems 135 4.6.2 Baseband Modems 136 4.6.3 Line Drivers 136 4.6.4 Group Band Modems 136 4.7 Digital Subscriber Line (DSL) 136 4.7.1 Asymmetric Digital Subscriber Line (ADSL) 137 4.7.2 Modulation 138 4.7.3 Distance Limitations 138 4.7.4 ITU-T Recommendations for ADSL 139 4.7.5 xdsl Technologies 139 4.8 Data Multiplexers 140 4.8.1 Types of Data Multiplexers 141 4.8.2 Frequency Division Multiplexers (FDMs) 142 4.8.3 Time Division Multiplexers (TDMs) 143 4.9 Statistical Time Division Multiplexers 144 4.9.1 Buffer 144 4.9.2 Protocol 145 4.9.3 Bit Map Statistical Multiplexing 145 4.9.4 Multiple-Character Statistical Multiplexing 145 4.9.5 Multiplexed Data Frame for Error Control Capability 146 4.9.6 Line Utilization Efficiency 147 4.9.7 Comparison of Data Multiplexing Techniques 150 Summary 150 Exercises 151 5 Error Control 153 185 5.1 Transmission Errors 153 5.1.1 Content Errors 153 5.1.2 Flow Integrity Errors 154 5.1.3 Methods of Error Control 155 5.2 Coding for Detection and Correction of Content Errors 156 5.2.1 Error Detection 156 5.2.2 Error Correction 157 5.2.3 Perfect Error Correcting Code 158 5.2.4 Systematic Code 159 5.2.5 Bit Error Rate (BER) 159 5.3 Error Detection Methods 159 5.3.1 Parity Checking 160 5.3.2 Checksum Error Detection 161 5.3.3 Cyclic Redundancy Check (CRC) 165 5.4 Forward Error Correction Methods 172 5.4.1 Block Parity 172 5.4.2 Hamming Code 174 5.4.3 Interleaved Codes 176 5.4.4 Convolutional Codes 177
viii CONTENTS 5.5 Reverse Error Correction 181 5.5.1 Stop and Wait 181 5.5.2 Go-Back-N 182 5.5.3 Selective Retransmission 182 Summary 183 Exercises 183 6 Network Architecture 186 212 6.1 Topology of a Computer Network 186 6.2 Elements of Meaningful Communication 187 6.3 Transport-Oriented Functions 189 6.3.1 Interaction with the Subnetwork 189 6.3.2 Quality of Transport Service 189 6.3.3 Conversion of Signals 189 6.3.4 Error Control 189 6.4 Components of a Computer Network 190 6.5 Architecture of a Computer Network 190 6.5.1 Network Architecture Models 190 6.5.2 Partitioning of a System 191 6.5.3 Features of a Partitioned Structure 191 6.6 Layered Architecture of a Computer Network 192 6.6.1 Need for Standardization of Network Architecture 193 6.7 Open System Interconnection 193 6.8 Layered Architecture of the OSI Reference Model 194 6.8.1 Application Layer 195 6.8.2 Presentation Layer 195 6.8.3 Session Layer 196 6.8.4 Transport Layer 196 6.8.5 Network Layer 196 6.8.6 Data Link Layer 197 6.8.7 Physical Layer 197 6.9 Functionality of the Layered Architecture 198 6.9.1 Hierarchical Communication 198 6.9.2 Peer-to-Peer Communication 199 6.10 OSI Terminology 200 6.11 Service Interface 201 6.11.1 Service Interface Primitives and Parameters 202 6.11.2 Types of Services 203 6.12 Data Transfer Modes 204 6.12.1 Connection-Oriented Mode of Data Transfer 204 6.12.2 Connectionless Mode of Data Transfer 205 6.13 Supplementary Functions 206 6.13.1 Multiplexing of Connections 206 6.13.2 Segmenting, Blocking, and Concatenation of Data Units 207
CONTENTS ix 6.14 Other Layered Architectures 208 6.14.1 TCP/IP 209 6.14.2 Systems Network Architecture (SNA) 209 6.14.3 Digital Network Architecture (DNA) 209 6.15 Standards Making Organizations 209 Summary 211 Exercises 211 7 The Physical Layer 213 241 7.1 The Physical Layer 213 7.1.1 Physical Connection 214 7.1.2 Service Provided to the Data Link Layer 214 7.2 Functions within the Physical Layer 215 7.3 Relaying Function in the Physical Layer 216 7.4 Physical Interface 217 7.5 Physical Layer Standards 218 7.6 EIA-232-D Digital Interface 219 7.6.1 DTE/DCE Interface 219 7.6.2 DTE and DCE Ports 220 7.6.3 DCE-DCE Connection 220 7.7 EIA-232-D Interface Specifications 221 7.7.1 Mechanical Specifications 221 7.7.2 Electrical Specifications 222 7.7.3 Functional Specifications 222 7.7.4 Procedural Specifications 226 7.8 Common Configurations of EIA-232-D Interface 229 7.8.1 Three-Wire Interconnection 230 7.8.2 Three-Wire Interconnection with Loopback 230 7.9 Null Modem 231 7.9.1 Null Modem with Loopback and Multiple Crossovers 232 7.10 Limitations of EIA-232-D 233 7.11 EIA-449 Interface 233 7.11.1 Mechanical Specifications 233 7.11.2 Electrical Specifications 235 7.11.3 Functional Specifications 236 7.12 EIA-530 237 7.13 ITU-T X.21 Recommendation 237 7.13.1 Mechanical Specifications 237 7.13.2 Electrical Specifications 237 7.13.3 Functional Specifications 238 7.13.4 Procedural Specifications 239 7.13.5 X.21bis Recommendation 239 Summary 239 Exercises 240
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