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Computers in Communication Gordon Brebner
iii
The book “Computers in Communication” by Gordon Brebner was originally published by McGraw-Hill International (UK) Limited in 1997. This edition has been made available in electronic PDF form by the author, following the original version going out of print and the copyright reverting to the author. All identified typographical errors in the original edition have been corrected, but otherwise there has been no updating of the content. In particular, all page numbering is the same as in the original version. c 2002 Gordon Brebner. All rights reserved. You may save a local Copyright copy or print a copy of this book, or parts of this book, for your own personal use, provided that identification of the title and author, and this copyright notice, is not removed. Any commercial exploitation is expressly prohibited.
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CONTENTS
Preface
xiii
1
Introduction
1.1 1.2
1.5 1.6
Background Uses of computer communications 1.2.1 Computer-oriented communication 1.2.2 Telecommunications 1.2.3 Radio and television broadcasting 1.2.4 Summary of uses of computer communications Physical links 1.3.1 Physical media and their properties 1.3.2 Physical communication services How computers communicate 1.4.1 Information, time and space 1.4.2 Agreement and implementation 1.4.3 Human influences Chapter summary Exercises and further reading
1 4 4 8 10 11 12 14 20 26 26 27 29 31 32
2
Information
35
2.1 2.2
Introduction Agreement on information types 2.2.1 Absolute and relative information types 2.2.2 Examples of communicated information types Implementation of required information types 2.3.1 Transformation of information
35 37 38 38 45 45
1.3
1.4
2.3
1
vii
viii CONTENTS
2.4 2.5
2.3.2 Representation of information Chapter summary Exercises and further reading
65 74 75
3
Time
80
3.1 3.2
3.4 3.5
Introduction Agreement on time periods 3.2.1 Absolute and relative time measurement 3.2.2 Examples of communication time periods Implementation of required time periods 3.3.1 Segmentation and concatenation 3.3.2 Flow control 3.3.3 Acknowledgement and error handling Chapter summary Exercises and further reading
80 83 83 85 92 92 97 103 107 108
4
Time Packages
110
4.1 4.2
4.6 4.7
Introduction Unsegmented time package 4.2.1 Connectionless services 4.2.2 Examples of unsegmented time packages Simple handshake time package 4.3.1 Examples of simple handshake time packages Multi-stage handshake time package 4.4.1 Examples of multi-stage handshake services Connection-oriented time package 4.5.1 Connection-oriented services 4.5.2 Examples of connection-oriented time packages Chapter summary Exercises and further reading
110 112 112 114 116 118 120 121 125 126 129 134 135
5
Space
138
5.1 5.2
Introduction Agreement on spaces 5.2.1 Identifier schemes 5.2.2 Absolute and relative spaces 5.2.3 Examples of communication spaces Implementation of required spaces 5.3.1 Filtering and switching 5.3.2 Splitting and multiplexing Chapter summary
138 140 140 147 149 150 150 159 165
3.3
4.3 4.4 4.5
5.3
5.4
CONTENTS ix
5.5
Exercises and further reading
166
6
Message Broadcasting Networks
168
6.1
6.5 6.6 6.7
Introduction 6.1.1 Information basics 6.1.2 Time basics 6.1.3 Space basics Multipeer channel implementation 6.2.1 Common medium 6.2.2 Chain or ring 6.2.3 Star or tree Communication multi