Table Of Content
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
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
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
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
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
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
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
8 The Data Link Layer...........242–280
8.1 Need for Data Link Control...........242
