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GLOBAL NETWORKS
ENGINEERING, OPERATIONS AND
DESIGN
G. Keith Cambron
Former President and CEO, AT&T Labs (Retired), Texas, USA
A John Wiley & Sons, Ltd., Publication

This edition first published 2013
© 2013 John Wiley and Sons Ltd
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John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, United Kingdom
For details of our global editorial offices, for customer services and for information about how to apply for
permission to reuse the copyright material in this book please see our website at www.wiley.com.
The right of the author to be identified as the author of this work has been asserted in accordance with the
Copyright, Designs and Patents Act 1988.
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in
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Library of Congress Cataloging-in-Publication Data
Cambron, G. Keith.
Global networks : engineering, operations and design / G. Keith Cambron.
pages cm
Includes bibliographical references and index.
ISBN 978-1-119-94340-2 (hardback)
1. Wireless communication systems. 2. Telecommunication. 3. Globalization. I. Title.
TK5103.C36 2012
384.5–dc23
2012022584
A catalogue record for this book is available from the British Library.
ISBN: 9781119943402
Typeset in 10/12pt Times by Laserwords Private Limited, Chennai, India.

Dedicated to Amos E. Joel, Jr
and the Members of the Technical Staff
at AT&T Labs and SBC Labs

Contents
List of Figures xv
About the Author xix
Foreword xxi
Preface xxiii
Acknowledgments xxv
List of Acronyms xxvii
Part I NETWORKS
1 Carrier Networks 3
1.1 Operating Global Networks 3
1.1.1 The Power of Redundancy 4
1.1.2 The Virtuous Cycle 6
1.1.3 Measurement and Accountability 7
1.2 Engineering Global Networks 8
1.2.1 Architecture 8
1.2.2 Systems Engineering 8
1.2.3 Capacity Management 8
1.3 Network Taxonomy 10
1.3.1 Voice Systems 10
1.3.2 Data Systems 12
1.3.3 Networks 13
1.3.4 Network Systems 13
1.4 Summary 14
References 14
2 Network Systems Hardware 15
2.1 Models 15
2.2 Telco Systems Model 16
2.2.1 Form and Function 16

viii Contents
2.2.2 Frames and Shelves 20
2.2.3 Chassis 20
2.2.4 Line I/O 21
2.2.5 Power Supply Cards 25
2.2.6 Network Fabric Cards 25
2.2.7 Application Processing 28
2.3 Modular Computing – Advanced Telecommunications Computing Architecture
(AdvancedTCA™) 29
2.3.1 Chassis 29
2.4 Blade Center Model 30
2.4.1 Midplane Design 31
2.4.2 Flexible High Speed Interconnection 32
2.4.3 Management Controller 32
2.4.4 Power and Fans 33
2.5 Summary 33
References 33
3 Network Systems Software 35
3.1 Carrier Grade Software 35
3.1.1 Real-Time 35
3.1.2 Reliable 36
3.1.3 Scalable 36
3.1.4 Upgradable and Manageable 38
3.2 Defensive Programming 38
3.2.1 Are You Really Sure? 38
3.2.2 Default Parameters 39
3.2.3 Heap Management 39
3.2.4 Exception Handling and Phased Recovery 39
3.2.5 Last Gasp Forensics 40
3.2.6 Buffer Discards and Dumps 40
3.3 Managed Objects 40
3.3.1 Administrative States 42
3.3.2 Service States 42
3.4 Operational Tests and Fault Conditions 43
3.4.1 Service Turn Up 43
3.4.2 Interrupt or Fault Induced 43
3.4.3 Out of Service Retries 43
3.4.4 On Demand 44
3.5 Alarms 44
3.5.1 Notiﬁcations 44
3.5.2 Severity 44
3.5.3 Scope 45
3.5.4 Creation and Persistence 46
3.5.5 Ethernet NIC Example 46
3.6 Network System Data Management 49
3.6.1 Management Information Bases (MIBs) 51

Contents ix
3.6.2 Syslog 52
3.6.3 Audits 53
3.7 Summary 54
References 54
4 Service and Network Objectives 55
4.1 Consumer Wireline Voice 55
4.1.1 Service Request 55
4.1.2 Address Signaling 56
4.1.3 Call Setup 56
4.1.4 Alerting 56
4.1.5 Call Completion 56
4.1.6 Disconnect 56
4.1.7 Network Service Objectives 57
4.1.8 Consumer Wireline Voice Network Model 57
4.1.9 Local Loops 58
4.1.10 Originating Office A 58
4.1.11 Toll Connect Group A–C 59
4.1.12 Tandem Office C 60
4.1.13 Toll Completing Group C–B 60
4.1.14 Terminating Office B 60
4.1.15 Long Term Downtime 60
4.1.16 Measurement Summary 60
4.2 Enterprise Voice over IP Service 61
4.2.1 Five 9’s 61
4.2.2 Meaningful and Measurable Objectives 61
4.3 Technology Transitions 65
4.4 Summary 66
References 66
5 Access and Aggregation Networks 69
5.1 Wireline Networks 70
5.1.1 Voice Services 70
5.1.2 Broadband Services 74
5.1.3 DSL 74
5.1.4 DSL Design and Engineering 76
5.1.5 DSL Operations 79
5.1.6 DSL Objectives, Metrics, and Line Management 80
5.1.7 ADSL Aggregation Networks 82
5.1.8 ADSL2+ and VDSL Aggregation Networks 82
5.1.9 Fiber to the Home (FTTH) 83
5.1.10 Fiber to the Curb (FTTC) 87
5.1.11 Fiber to the Node (FTTN) 87
5.1.12 FTTH Design and Engineering 87
5.1.13 FTTH Operations 90
5.1.14 FTTH Aggregation Networks 91

x Contents
5.2 Hybrid Fiber Coax (HFC) Networks 92
5.2.1 Node Design 93
5.2.2 Digital TV 93
5.2.3 DOCSIS 94
5.2.4 HFC Design and Engineering 94
5.2.5 HFC Operations 95
5.3 Wireless Mobile Networks 96
5.3.1 GSM 97
5.3.2 Universal Mobile Telecommunications Systems (UMTS) 106
5.3.3 Long Term Evolution (LTE) 111
5.4 Wireless Design and Engineering 118
5.4.1 Air Interface 118
5.4.2 Mobility 121
5.4.3 Inter-Radio Access Technology (IRAT) 122
5.4.4 Device Behavior 122
5.5 Summary 123
References 123
6 Backbone Networks 125
6.1 Transport 127
6.1.1 Transport Services 127
6.1.2 Transport Resiliency and Protection 130
6.2 IP Core 135
6.2.1 Regional IP Backbones 136
6.2.2 Points of Presence (POPs) 137
6.2.3 Multiprotocol Label Switching (MPLS) 137
6.2.4 Route Reflectors 143
6.3 Backbone Design and Engineering 143
6.3.1 Location and Size of POPs 144
6.3.2 Fault Recovery 144
6.3.3 Quality of Service QoS 145
6.3.4 Traffic Demand 146
6.3.5 Control Plane 146
6.4 Summary 147
References 147
7 Cloud Services 149
7.1 Competition 149
7.2 Defining the Cloud 150
7.2.1 Architecture 150
7.2.2 Infrastructure 151
7.2.3 Intelligent Networks and Intelligent Clouds 152
7.2.4 Internet Protocol Multimedia Subsystem (IMS) 156
7.2.5 Application Servers and Enablers 162
7.2.6 IMS Design and Engineering 164

Contents xi
7.3 Cloud Services 166
7.3.1 Network-Based Security 166
7.3.2 Voice over IP (VoIP) Services 167
7.3.3 Conferencing 170
7.3.4 Compute and Storage 170
7.3.5 The Mobile Cloud 170
7.4 Summary 171
References 171
8 Network Peering and Interconnection 173
8.1 Wireline Voice 173
8.1.1 Interexchange Carriers (IXCs) 174
8.1.2 Competitive Local Exchange Carriers (CLECs) 177
8.2 SS7 Interconnection 178
8.2.1 Services 178
8.3 IP Interconnection 180
8.3.1 VPN Peering 180
8.3.2 Internet Peering 180
8.3.3 Public Peering 183
8.3.4 Mobility Peering 185
8.4 Summary 187
References 188
Part II TEAMS AND SYSTEMS
9 Engineering and Operations 191
9.1 Engineering 192
9.1.1 Systems Engineers 192
9.1.2 Network Planning 196
9.1.3 Network and Central Ofﬁce Engineers 196
9.1.4 Outside Plant Engineers 197
9.1.5 Common Systems Engineers 197
9.2 Operations 197
9.2.1 Network Operations Center (NOCs) 198
9.2.2 Tiered Maintenance 202
9.3 Summary 204
References 205
10 Customer Marketing, Sales, and Care 207
10.1 Industry Markets 207
10.1.1 Competitive Local Exchange Carriers (CLECs) 207
10.1.2 Interexchange Carriers (IXCs) 210
10.2 Consumer Markets 211
10.2.1 Product Marketing 212
10.2.2 Consumer Care 214

xii Contents
10.3 Enterprise Markets 218
10.3.1 Pre-Sales Support 219
10.3.2 Sales Support 220
10.3.3 Engineering and Implementation 220
10.4 Summary 220
References 221
11 Fault Management 223
11.1 Network Management Work Groups 223
11.2 Systems Planes 224
11.2.1 Bearer Planes 224
11.2.2 Control Planes 225
11.2.3 Management Planes 226
11.3 Management Systems 227
11.3.1 Network Management Systems 227
11.3.2 Element Management Systems 230
11.3.3 Network Elements 231
11.3.4 Management Interfaces 231
11.3.5 Specialized Management Systems 240
11.4 Management Domains 244
11.4.1 Optical Networks 245
11.4.2 IP/MPLS Networks 246
11.4.3 Other Domains 247
11.5 Network Management and the Virtuous Cycle 247
11.5.1 Notiﬁcations 247
11.5.2 Sectionalization 249
11.5.3 Fault Isolation 249
11.6 Summary 250
References 251
12 Support Systems 253
12.1 Support Systems Standards and Design 253
12.2 Capacity Management Systems 255
12.2.1 Work Groups 256
12.2.2 Data Collection 257
12.2.3 Engineering Rules 259
12.2.4 Capacity Management Applications 260
12.2.5 Supply Chain Management 261
12.3 Service Fulﬁllment 261
12.3.1 Offers and Proposals 262
12.3.2 Service Ordering 264
12.3.3 Service Activation 267
12.4 Design and Engineering 268
12.5 Summary 268
References 268

Contents xiii
Part III TRANSFORMATION
13 Integration and Innovation 271
13.1 Technology Integration 271
13.1.1 Technology Scanning 272
13.1.2 Technology Selection 273
13.1.3 Network System Testing and Veriﬁcation 277
13.1.4 Support Systems Integration 287
13.2 Lifecycle Support 288
13.3 Invention and Innovation 290
13.3.1 The Role of Research 291
13.3.2 The Bridge to Research 292
13.4 Summary 295
References 296
14 Disasters and Outages 297
14.1 Disasters 297
14.1.1 Carrier Teams 298
14.1.2 Disaster Response 300
14.1.3 Engineering and Design 300
14.2 Outages 302
14.2.1 Anatomy of an Outage 302
14.2.2 Congestion Onset 307
14.2.3 Congestion Propagation 307
14.2.4 Root Cause 308
14.2.5 Contributing Cause 309
14.2.6 Triggering Events 309
14.2.7 Teams in an Outage 309
14.2.8 Press and External Affairs 311
14.3 The Vicious Cycle 313
14.3.1 Engineering and Operational Defense 314
14.4 Summary 316
References 316
15 Technologies that Matter 317
15.1 Convergence or Conspiracy? 317
15.1.1 Enter the World Wide Web 318
15.1.2 Silicon Valley – A Silent Partner 318
15.1.3 US Telecommunication Policy 318
15.1.4 The Conspiracy – A Conﬂuence of Events 319
15.1.5 Local Phone Service in Jeopardy 320
15.1.6 Technologies in Response 322
15.2 Technologies Beyond 2012 324
15.2.1 IPv6 324
15.2.2 Invisible Computing 332

xiv Contents
15.2.3 Beyond 400G 334
15.3 HTML5 and WEBRTC 335
15.3.1 Video Evolution 337
15.3.2 High Deﬁnition Voice 338
15.4 Summary 340
References 341
16 Carriers Transformed 343
16.1 Historical Transformations 343
16.1.1 Stored Program Control Switching 1965–1985 343
16.1.2 Digital Wireline Communications 1975–2000 344
16.1.3 Digital Wireless Communication 1990–Onwards 345
16.2 Regulation and Investment 346
16.2.1 Regulation 346
16.2.2 Investment 347
16.3 Consumer Wireline Networks and Services 347
16.3.1 Market Trends 347
16.3.2 Technology 348
16.4 Wireless Networks and Services 351
16.4.1 Market Trends 351
16.4.2 Technology 352
16.5 Backbone Networks 352
16.6 Science and Technology Matter 353
References 353
Appendix A: IPv6 Technologies 355
Appendix B: The Next Generation Network and Why We’ll Never See It 361
Index 367

List of Figures
Figure 1.1 Simplex operation 4
Figure 1.2 Duplex model 5
Figure 1.3 Virtuous Cycle 6
Figure 1.4 Network and management systems 10
Figure 2.1 Telco system model 19
Figure 2.2 Full backplane chassis 21
Figure 2.3 Midplane chassis 21
Figure 2.4 T1 line card 22
Figure 2.5 System controller 26
Figure 2.6 ATCA chassis 30
Figure 2.7 Blade center chassis 31
Figure 2.8 Functional blade center diagram 32
Figure 3.1 Poorly behaved systems 37
Figure 3.2 Four port Ethernet NIC 41
Figure 3.3 Managed object hierarchy 41
Figure 3.4 Network element alarm processes 45
Figure 3.5 Link out of service example 47
Figure 3.6 Provisioning a new port 48
Figure 3.7 Data management hierarchy 49
Figure 4.1 Network impairment allocations 58
Figure 4.2 Enterprise VoIP network 63
Figure 5.1 Carrier functional model 70
Figure 5.2 Local access transport area 71
Figure 5.3 Local exchange SS7 network 72
Figure 5.4 Distribution area concept 74
Figure 5.5 SAI cross connect and serving terminal 76
Figure 5.6 Power spectral density for digital services 77
Figure 5.7 ADSL – VDSL cable sharing 77
Figure 5.8 Bridge tap 79
Figure 5.9 ADSL aggregation network 82
Figure 5.10 ADSL2+ and VDSL aggregation network 83
Figure 5.11 Passive Optical Network (PON) 84
Figure 5.12 Single Family Unit (SFU) Optical Network Terminal (ONT) 86

xvi List of Figures
Figure 5.13 Multiple Dwelling Unit (MDU) Optical Network Unit (ONU) 87
Figure 5.14 Pre-engineered optical distribution 88
Figure 5.15 FTTH aggregation network 91
Figure 5.16 HFC ﬁber node design 93
Figure 5.17 Mobile network architecture 97
Figure 5.18 GSM voice mobility management 99
Figure 5.19 SMS architecture 101
Figure 5.20 GPRS data mobility management 104
Figure 5.21 UMTS data mobility management 109
Figure 5.22 LTE and UMTS interworking 114
Figure 5.23 Adaptive modulation example 120
Figure 6.1 Backbone network regional view 126
Figure 6.2 Transport and routing 128
Figure 6.3 Architect’s network view 131
Figure 6.4 Topological network view 131
Figure 6.5 SONET nodes 132
Figure 6.6 SONET ring 133
Figure 6.7 IP routing core 138
Figure 6.8 Core routing protocols 141
Figure 7.1 Carrier three layer model 150
Figure 7.2 Intelligent DNS 153
Figure 7.3 Intelligent Route Service Control Point (IRSCP) 155
Figure 7.4 IMS architecture 158
Figure 8.1 IXC call completion via LNP 175
Figure 8.2 Internet peering arrangements 181
Figure 8.3 Interdomain routing 184
Figure 8.4 SMS interworking architecture 187
Figure 9.1 Tiered operations support 198
Figure 9.2 AT&T Global Network Operations Center (NOC) 199
Figure 10.1 Historical chart of consumer data rates 213
Figure 11.1 Network and support system roles 225
Figure 11.2 Hierarchy of management systems 226
Figure 11.3 Model NMS 229
Figure 11.4 TL1 management example 233
Figure 11.5 SNMP management example 236
Figure 11.6 CORBA example 239
Figure 11.7 Darkstar 241
Figure 11.8 Watch7 SS7 network monitor 243
Figure 11.9 Network management domains 245
Figure 11.10 Network management and the Virtuous Cycle 248
Figure 12.1 TMN functional layer model 254
Figure 12.2 TMN operations process model 255
Figure 12.3 Capacity management system design 257
Figure 12.4 High usage engineering 259
Figure 12.5 Demand and capacity chart 260
Figure 12.6 Service fulﬁllment 262

List of Figures xvii
Figure 13.1 Fully developed test facility 279
Figure 14.1 SS7 networks circa 1991 303
Figure 14.2 DSC STP logical model 306
Figure 14.3 Trafﬁc discard in a well-behaved system 308
Figure 14.4 The Vicious Cycle 314

About the Author
Keith Cambron has a broad range of knowledge in telecommunications networks, technology
and design and R&D management. His experience ranges from circuit board and software
design to the implementation of large public networks.
Keith served as the President and CEO of AT&T Labs, Inc. AT&T Labs designs AT&T’s
global IP, voice, mobile, and video networks. Network technology evaluation, certification,
integration, and operational support are part of the Lab’s responsibilities. During his tenure
AT&T Labs had over 2000 employees, including 1400 engineers and scientists. Technologies
produced by Labs ranged from core research to optical transport, IP routing, voice, and video
systems.
2003 to 2006 – Cambron served as the President and CEO of SBC Laboratories, Inc. The
organization, which set the strategic technology objectives of SBC, was structured into four
technology areas; Broadband, Wireless, Network Services, and Enterprise IT. SBC Labs led
the industry in the introduction of VDSL and IPTV technologies.
1998 to 2003 – Cambron was principal of Cambron Consulting, where he provided net-
work and software design consulting services to the telecommunications industry. Working
with clients such as SBC, Vodafone Wireless, Coastcom and various enterprise networks,
Cambron designed and developed network management systems, a wireless Short Messag-
ing Service (SMS) server, a Service Switching Point (SSP), and an ADSL transmission
performance optimization system.
1987 to 1997 – Cambron held leadership positions at Pacific Bell Broadband, acting
as the chief architect of a network engineering team that developed a 750 MHz hybrid
fiber/coax-based network. For this project, Cambron received Telephony’s “Fiber in the
Loop” design award.
His career started at Bell Telephone Laboratories in 1977, where he began as a member of
the technical staff. He advanced to Director of Local Switching Systems Engineering and led
a team to design automated verification test tools for local digital switch testing. Cambron
went on to become Director of Network Systems Verification Testing at Bell Communications
Research, heading field verification teams in all seven Regional Bell Operating Companies
to test “first in nation” technologies, including the first local digital switching systems.
Cambron has been profiled in Telephony and America’s Network, and has published in
IEEE Communications and Proceedings of the IEEE. He taught Object Oriented Design
at Golden Gate University in San Francisco and is a Senior Member of the Institute of
Electrical and Electronics Engineers (IEEE).

xx About the Author
In 2010, Cambron was named by CRN Magazine as one of the Top 25 Technology
Thought-Leaders in the world. Keith received IEEE Communications Society’s Chairman’s
Communication Quality and Reliability Award in 2007. He holds ten patents for telecom-
munications software and systems he designed and deployed.
Cambron received his BS in Electrical Engineering from the University of Missouri, an
MS in Systems Management from the University of Southern California, and a Programming
Certiﬁcation from the University of California at Berkeley. He is a retired Commander in
the United States Naval Reserve.

Foreword
Networks today are like the air we breathe, so ubiquitous we often take them for granted and
in fact don’t even realize they’re there. Whether we are working, studying, communicating
or being entertained, we rely on networks to make whatever we need to happen, happen.
This trend is increasing as networks become more and more powerful and reach more deeply
into the fabric of our lives.
This reach is not limited to just the wealthy or to developed nations, however, as lower
costs and higher capacity extend the power of networks to citizens all around the globe.
That’s what makes this book so relevant and so timely. A clear understanding of these
networks is essential for those that would design, construct, operate and maintain them. As
Keith points out early in this volume, the growing gap between the academic description
of networks and the real world design and operation of these networks, is a key divide that
needs bridging. And Keith is in a unique position to do this.
I’ve known Keith for over 15 years, and have always found him to be a fascinating and
indeed remarkable man. His curiosity and intelligence, coupled with a career so deeply
involved in network design at AT&T has given him the tremendous insight that he shares in
this book. Keith has never been afraid to step outside the accepted norm, if he felt the need,
for pursuit of a new area of excellence. This is what makes his knowledge and understanding
so valuable and drives the core of this work.
Looking forward, Moore’s Law will continue to enable the exponential growth of the value
of the underlying technologies, namely processing, memory and optical communications
speed, that make these networks tick. The resultant capabilities of the next generations of
networks, ﬁve years or a decade out, are virtually indescribable today! That in the end
is what makes this book so valuable – a thorough understanding of the design principles
described herein will allow those that shape our networks in the future to “get it right,”
enhancing our lives in ways we cannot begin to imagine.
Robert C. McIntyre
Chief Technical Ofﬁcer, Service Provider Group
Cisco Systems

Preface
When I began my career in telecommunications in 1977 at Bell Telephone Laboratories
two texts were required reading, Engineering and Operations in the Bell System [1] and
Principles of Engineering Economics [2]. Members of Technical Staff (MTS) had Masters or
PhDs in engineering or science but needed grounding in how large networks were designed
and operated, and how to choose designs that were not only technically sound, but econom-
ically viable. As the designers of the equipment, systems and networks, engineers at Bell
Labs were at the front end of a vertically integrated company that operated the US voice
and data networks. Operational and high availability design were well developed disciplines
within Bell Labs, and network systems designs were scrutinized and evaluated by engineers
practicing in those fields. So ingrained in the culture was the operational perspective, that
engineers and scientists were strongly encouraged to rotate through the Operating Company
Assignment Program (OCAP) within the first two years of employment. During that eight
week program engineers left their Bell Labs jobs and rotated through departments in a Bell
Telephone Operating Company, serving as operators, switchmen, installers and equipment
engineers. OCAP was not restricted to engineers working on network equipment; members
of Bell Labs Research participated in the program. AT&T was not alone in recognizing
the value of operational and reliability analysis in a vertically integrated public telephone
company, Nippon Telephone and Telegraph, British Telecom, France Telecom and other
public telephone companies joined together in technical forums and standards organizations
to codify operational and high availability design practices.
After 1982 regulatory, technology and market forces dramatically changed the way net-
works and systems were designed and deployed. Gone are vertically integrated franchise
operators, replaced by interconnected and competing networks of carriers, equipment and
systems suppliers, and integrators. Innovation, competition and applications are the engines
of change; carriers and system suppliers respond to meet the service and traffic demands of
global networks growing at double and even triple digit rates, carrying far more video con-
tent than voice traffic. Consumer and enterprise customers are quick to adopt new devices,
applications and network services; however, when legacy carriers deliver the service the
customers’ expectations for quality and reliability are based on their long experience with
the voice network. The industry has largely delivered on those expectations because an
experienced cadre of engineers from Bell Labs and other carrier laboratories joined startups
and their spun off suppliers like Lucent and Nortel. But as time passes, the operational skill
reservoir recedes not only because the engineers are retiring, but because of the growing
separation between engineers that design and operate networks, and those that design equip-
ment, systems and applications that enter the network. The clearest example of the change
is the influx of IT trained software engineers into the fields of network applications and

xxiv Preface
systems design. Experience in the design of stateless web applications or financial systems
are insufficient for the non-stop communication systems in the network that continue to
operate under a range of hardware faults, software faults and traffic congestion.
My own journey gave me a front row seat through the transformation from a regulated
voice network to a competitive global IP network. As a systems engineer in the 1970s I
worked on call processing requirements and design for the No. 1 ESS. In the 1980s I led
teams of test and verification engineers in the certification of the DMS-10, DMS-100, No.
5ESS, No. 2 STP, DMS STP and Telcordia SCP. I also led design teams building integrated
test systems for Signaling System No. 7 and worked for startup companies designing a
DS0/1/3 cross connect system and a special purpose tandem switching system. During the
last eight years I headed SBC Labs and then AT&T Labs as President and CEO. Working
with engineers across network and systems, and spending time with faculty and students
at universities I became aware of the growing gap in operational design skills. Universities
acknowledge and reward students and faculty for research into theoretical arenas of network
optimization and algorithm design. Their research is seldom based on empirical data gathered
from networks, and rarer still is the paper that actually changes the way network or systems
operate. I chose to write this book to try and fill some of that void. My goal is to help:
• those students and faculty interested in understanding how operational design practices can
improve system and network design, and how networks are actually designed, managed
and operated;
• hardware and software engineers designing network and support systems;
• systems engineers developing requirements for, or certifying network equipment;
• systems and integration engineers working to build or certify interfaces between network
elements and systems;
• operations support systems developers designing software for the management of network
systems; and
• managers working to advance the skills of their engineering and operating teams.
The book is organized into three parts; Networks, Teams and Systems, and Transfor-
mation. It is descriptive, not prescriptive; the goal is not to tell engineers how to design
networks but rather describe how they are designed, engineered and operated; the emphasis
is on engineering and design practices that support the work groups that have to install,
engineer and run the networks. Areas that are not addressed in the book are network opti-
mization, engineering economics, regulatory compliance and security. Security as a service
is described in the chapter on cloud services but there are several texts that better describe
the threats to networks and strategies for defense [3, 4].
References
1. Engineering and Operations in the Bell System, 1st edn, AT&T Bell Laboratories (1977).
2. Grant, E.L. and Ireson, W.G. (1960) Principles of Engineering Economy, Ronald Press Co., New York.
3. Cheswick, W.R. Bellovin, S.M. and Rubin, A.D. (2003) Firewalls and Internet Security, 2nd edn, Repelling the
Wily Hacker, Addison Wesley.
4. Amoroso, E. (2010) Cyber Attacks: Protecting National Infrastructure, Butterworth-Heinemann, November.

Acknowledgments
The technical breadth of this text could not have been spanned without the help of engineers
I have had the privilege of working with over the years. While I researched and wrote the
entire text, these contributors were kind enough to review my material. I am grateful for
the contributions of John Erickson, Mike Pepe, Chuck Kalmanek, Anthony Longhitano,
Raj Savoor, and Irene Shannon. Each reviewed speciﬁc chapters that cover technology
within their area of expertise and corrected my technical errors and omissions. They are not
responsible for the opinions and projections of future technology trends, and any remaining
errors are mine.
I also want to thank the team at John Wiley & Sons, Ltd for guiding me through the
writing and publishing process. They made the experience enjoyable and their professional
guidance kept me on a sure track.

List of Acronyms
10G 10 Gigabit
100G 100 Gigabit
10GEPON 10 Gigabit Ethernet Passive Optical Network
21CN 21st Century Network
3G Third Generation Mobile Technology
3GPP Third Generation Partnership Project
4G Fourth Generation Mobile Technology
40G 40 Gigabit
400G 400 Gigabit
6rd IPv6 Rapid Deployment
AAAA Quad A DNS Record
ABR Available Bit Rate
ACD Automatic Call Distributor
ACM Address Complete Message (ISUP)
ADL Advanced Development Lab
ADM Add-Drop Multiplexer
ADPCM Adaptive Differential Pulse Code Modulation
ADSL Asymmetric Digital Subscriber Line
ADSL1 Asymmetric Digital Subscriber Line G.992.1 standard
ADSL2+ Asymmetric Digital Subscriber Line G.992.5 standard
AIN Advanced Intelligent Network
AINS Automatic In-Service
AIS Alarm Indication Signal
ALG Application Level Gateway
ALI Automatic Line Identiﬁcation
AMI Alternate Mark Inversion
AMPS Advanced Mobile Phone Service
AMR Adaptive Multi-Rate
API Application Programming Interface
APN Access Point Name
APS Automatic Protection Switching
ARGN Another Really Good Network
ARP Address Resolution Protocol
AS Autonomous System

xxviii List of Acronyms
AS Application Server
ASON Automatic Switched Optical Network
ASP Application Service Provider
AT Access Tandem
ATA Analog Terminal Adapter
ATCA Advanced Telecommunications Computing Architecture
ATM Asynchronous Transfer Mode
ATSC Advanced Television Systems Committee
AUMA Automatic and Manual Service State
AWG American Wire Gauge
AWS Advanced Wireless Services
BCP Business Continuity Plan
BCPL Basic Combined Programming Language
BGCF Breakout Gateway Control Function
BGF Border Gateway Function
BGP Border Gateway Protocol
BITS Building Integrated Timing Supply
BLSR Bi-directional Line Switched Ring
BORSCHT Battery, Over-voltage, Ringing, Supervision, Codec, Hybrid, Testing
BPON Broadband Passive Optical Network
BRAS Broadband Remote Access Server
BRI Basic Rate Interface (ISDN)
BSC Base Station Controller
BSD Berkeley Software Distribution
BSS Business Support System
BSSMAP Base Station Subsystem Mobile Application Part
BT British Telecom
BTL Bell Telephone Laboratories
BTS Base Transceiver Station
CALEA Communications Assistance for Law Enforcement Act
CAMEL Customized Applications for Mobile network Enhanced Logic
CAS Channel Associated Signaling
CAT3 Category 3, refers to a grade of twisted pair cable
CATV Community Antenna Television
CBR Constant Bit Rate
CCAP Converged Cable Access Platform
CCIS Common Channel Interofﬁce Signaling
CCS Common Channel Signaling
CDB Centralized Database
CDF Charging Data Function
CDMA Code Division Multiple Access
CDN Content Delivery Network
CDR Call Detail Record
CE Customer Edge
CES Circuit Emulation Service
CGN Carrier Grade NAT

List of Acronyms xxix
CGN64 Carrier Grade NAT IPv6/IPv4
CIC Carrier Identification Code
CIC Circuit Identification Code
CLASS Custom Local Area Signaling Services
CLEC Competitive Local Exchange Carrier
CLI Command Line Interface
CLLI Common Language Location Identifier
CM Cable Modem
CM Capacity Management
CMS Customer Management System
CMTS Cable Modem Termination System
CNAM Calling Name Service
CO Central Office
CONF Conference Services
CORBA Common Object Request Broker Architecture
CoS Class of Service
CPE Customer Premises Equipment
CPU Central Processing Unit
CR Constrained Routing
CRC Cyclic Redundancy Check
CRS Carrier Routing System
CSCF Call Session Control Function
CSFB Circuit Switched Fallback
CSS3 Cascading Style Sheet 3
CTAG Command Tag
CURNMR Current Noise Margin
DA Distribution Area
DAML Digitally Added Main Line
DARPA Defense Advanced Research Projects Agency
DAS Directed Antenna System
DBMS Database Management System
DBOR Database of Record
DCC Data Communications Channel
DCS Digital Cross Connection System
DHCP Dynamic Host Control Protocol
DHCP6 Dynamic Host Control Protocol for IPv6
DLC Digital Loop Carrier
DLNA Digital Living Network Alliance
DMS Digital Multiplex System
DMT Discrete Multitone
DMTS Distinguished Member of Technical Staff
DNS Domain Name System
DNS64 Domain Name System for IPv4 and IPv6
DOCSIS Data Over Cable Service Interface Specification
DoS Denial Of Service
DPM Defects Per Million

xxx List of Acronyms
DSBLD Disabled Service State
DSL Digital Subscriber Line
DSLAM Digital Subscriber Line Access Multiplexer
DSM Dynamic Spectrum Management
DSP Digital Signal Processor
DSTM Dual Stack IPv6 Transition Mechanism
DSX Digital Cross Connect
DTAP Direct Transfer Application Part (SS7)
DTV Digital Television
DVB Digital Video Broadcast
DVD Digital Video Disc
DVR Digital Video Recorder
DWDM Dense Wave Division Multiplexing
E911 Enhanced 911
EADAS Engineering Admin Data Acquisition System
EDFA Erbium Doped Fiber Ampliﬁer
EDGE Enhanced Data Rates for Global Evolution
EFM Ethernet in the First Mile
EGP External Gateway Protocol
EIGRP Enhanced Interior Gateway Routing Protocol
EMEA Europe, the Middle East and Africa
EMS Element Management System
ENUM E.164 Number Mapping
EOC Embedded Operations Channel
EPON Ethernet Passive Optical Network
ESAC Electronic Systems Assurance Center
ESME External Short Messaging Entity
ESS Electronic Switching System
eTOM Enhanced Telecom Operations Map
ETS Electronic Translator System
FCAPS Fault, Conﬁguration, Accounting, Performance, Security
FCC Federal Communications Commission
FDD Frequency Division Duplex
FDMA Frequency Division Multiple Access
FEC Forwarding Equivalent Class
FEXT Far End Crosstalk
FOU Field of Use
FRR Fast Reroute
FRU Field Replaceable Unit
FSAN Full Service Access Network
FTP File Transfer Protocol
FTTB Fiber To The Building
FTTC Fiber To The Curb
FTTH Fiber To The Home
FTTN Fiber To The Node

List of Acronyms xxxi
GEM GPON Encapsulation Method
GERAN GSM EDGE Radio Access Network
GGSN Gateway General Packet Radio Services Support Node
GMPLS Generalized Multi-protocol Label Switching
GMSC Gateway Mobile Switching Center
GMSK Gaussian Minimum Shift Keying
GNOC Global Network Operations Center
GPON Gigabit Passive Optical Network
GPS Global Positioning System
GRE Generic Routing Encapsulation
GRX GPRS Routing Exchange
GSM Global System for Mobile Communications
GTP GPRS Tunneling Protocol
GTT Global Title Translation
HD High Definition
HDSL High Bitrate Digital Subscriber Line
HDTV High Definition Television
HFC Hybrid Fiber Coax
HLR Home Location Register
HPNA Home Phone line Networking Alliance
HR Human Resources
HSDPA High Speed Downlink Packet Access
HSPA High Speed Packet Access
HSS Home Subscriber Server
HSUPA High Speed Uplink Packet Access
HTML Hyper Text Markup Language
HTTP Hyper Text Transfer Protocol
HVAC Heating, Ventilation and Air Conditioning
IAM Initial Address Message (SS7)
IAS Internet Access Service
IBCF Interconnection Border Control Function
ICMP Internet Control Message Protocol
IDL Interface Definition Language
IGMP Internet Group Management Protocol
IGP Interior Gateway Protocol
ILEC Incumbent Local Exchange Carrier
IM Instant Messaging
IMS IP Multimedia Subsystem
IMSI International Mobile Subscriber Identifier
IN Intelligent Network
IOT Interoperability Testing
IP Internet Protocol
IPMI Intelligent Platform Management Interface
IPTV Internet Protocol Television
IPX Internet Protocol Packet Exchange

xxxii List of Acronyms
IRAT Inter-Radio Access Technology
IRSCP Intelligent Route Service Control Point
IS In-Service
ISATAP Intra-Site Automatic Tunnel Addressing Protocol
ISDN Integrated Services Digital Network
ISP Internet Services Provider
ISUP ISDN User Part
IT Information Technology
ITP IP Transfer Point
IVR Interactive Voice Response
IXC Interexchange Carrier
IXP Internet Exchange Point
KPI Key Performance Indicator
LAN Local Area Network
LATA Local Access Transport Area
LCP Local Convergence Point
LD Long Distance
LDP Label Distribution Protocol
LEC Local Exchange Carrier
LEN Line Equipment Number
LER Label Edge Router
LERG Local Exchange Routing Guide
LFIB Label Forwarding Information Base
LFO Line Field Organization
LIDB Line Information Database
LLDP Local Loop Demarcation Point
LMTS Lead Member of Technical Staff
LNP Local Number Portability
LOF Loss of Frame
LOL Loss of Link
LOS Loss of Signal
LP Link Processor
LPBK Loop Back
LPR Loss of Power
LRF Location Retrieval Function
LRN Local Routing Number
LSA Link State Advertisement
LSDB Link State Database
LSN Large Scale NAT
LSP Label Switched Path
LSR Label Switch Router
LSSGR LATA Switching System Generic Requirements
LTE Long Term Evolution
MA Manual Service State
MAP Mobile Application Part

List of Acronyms xxxiii
MDF Main Distribution Frame
MDR Message Detail Record
MDU Multiple Dwelling Unit
MED Multi-Exit Discriminator
MF Multi-Frequency
MFJ Modified Final Judgment
MGCF Media Gateway Control Function
MGW Media Gateway
MIB Management Information Base
MIME Multipurpose Internet Mail Extension
MIMO Multiple In Multiple Out
MOB Mobility and Location Services
MME Mobile Management Entity
MML Man Machine Language
MMS Multimedia Message Service
MNO Mobile Network Operator
MOP Method of Procedure
MPEG Motion Pictures Expert Group
MPLS Multiprotocol Label Switching
MPOE Minimum Point of Entry
MRFC Media Resource Function Controller
MRFP Media Resource Function Processor
MS Mobile Station
MSC Mobile Switching Center
MSIN Mobile Subscriber Identification Number
MSISDN Mobile Subscriber Integrated Services Digital Subscriber Number
MSO Multiple System Operator
MSPP Multiservice Provisioning Platform
MSR Multi-standard Radio
MSRN Mobile Station Routing Number
MT Maintenance Service State
MTS Member of Technical Staff
MTSO Mobile Telephone Switching Office
NAP Network Access Point
NAT Network Address Translation
NB Narrowband
NCL Network Certification Lab
NCP Network Control Point
NDC Network Data Center
NE Network Element
NEBS Network Equipment Building Standards
NEXT Near End Crosstalk
NGN Next Generation Network
NIC Network Interface Card
NICE Network-Wide Information Correlation and Exploration

xxxiv List of Acronyms
NID Network Interface Device
NLRI Network Layer Reachability Information
NMC Network Management Center
NMP Network Management Plan
NMS Network Management System
NNI Network to Network Interface
NOC Network Operations Center
NORS Network Outage Reporting System
NPA Numbering Plan Area
NPOE Network Point of Entry
NPRM Notice of Proposed Rule Making
NR Normal Service State
NSE Network Systems Engineering
NSTS Network Services Test System
NTSC National Television Systems Committee
NTT Nippon Telephone and Telegraph
OA&M Operations, Administration & Maintenance
OEM Original Equipment Manufacturer
OFDM Orthogonal Frequency Division Multiplexing
OFDMA Orthogonal Frequency Division Multiple Access
OID Object Identiﬁer
OLT Optical Line Terminal
OMA Open Mobile Alliance
ONT Optical Network Terminal
ONU Optical Network Unit
OOS Out of Service
ORB Object Request Broker
ORT Operational Readiness Test
OS Operating System
OSA Open Services Architecture
OSI Open Systems Interconnection
OSP Outside Plant
OSPF Open Shortest Path First
OSS Operations Support System
OTA Over the Air
OTDR Optical Time Domain Reﬂectometer
OTN Optical Transport Network
OTT Over The Top
PAL Phase Alternating Line video standard
PAT Port Address Translation
PBX Private Branch Exchange
PC Personal Computer
PCEF Policy Charging Enforcement Function
PCM Pulse Code Modulation
PCRF Policy Charging Rules Function

List of Acronyms xxxv
PCS Personal Communication Service
PCU Packet Control Unit
PDN Packet Data Network
PDP Packet Data Protocol
PDU Packet Data Unit
PE Provider Edge
PEG Public Education and Government
PERF Policy Enforcement Rules Function
PIC Polyethylene Insulated Cable
PIC Primary Inter-LATA Carrier
PIM Protocol Independent Multicast
PLMN Public Land Mobile Network
PM Performance Management
PMTS Principal Member of Technical Staff
PON Passive Optical Network
POP Point of Presence
POTS Plain Old Telephone Service
PPP Point to Point Protocol
PRI Primary Rate Interface (ISDN)
PSAP Public Service Answering Point
PSL Production Support Lab
PSTN Public Switched Telephone Network
PTE Path Terminating Equipment
PUC Public Utility Commission
PVC Private Virtual Circuit
RAB Radio Access Bearer
RADIUS Remote Authentication Dial In User Service
RAN Radio Access Network
RBOC Regional Bell Operating Company
RCA Root Cause Analysis
RDC Regional Data Center
RF Radio Frequency
RFC Request for Comment
RFP Request for Proposal
RIR Regional Internet Registry
RNC Radio Network Controller
ROADM Reconﬁgurable Optical Add Drop Multiplexer
RP Route Processor
RRC Radio Resource Control
RSS Remote Switching System
RSVP Resource Reservation Protocol
RTM Rear Transition Module
RTP Real-time Transport Protocol
RTT Round Trip Time
SAI Serving Area Interface

xxxvi List of Acronyms
SAN Storage Area Network
SBC Session Border Controller
SCC Switching Control Center
SCCS Switching Control Center System
SCE CAMEL Service Environment
SCP Service Control Point
SCTE Society of Cable and Television Engineers
SDH Synchronous Digital Hierarchy
SDSL Symmetric Digital Subscriber Line
SDV Switched Digital Video
SECAM Sequential Color with Memory (FR)
SEG Security Gateway
SELT Single Ended Line Test
SFTP Secure File Transfer Protocol
SFU Single Family Unit
SGSN Serving General Packet Radio Services Node
SGW Signaling Gateway
SIL Systems Integration Lab
SIM Subscriber Identity Module
SIP Session Initiation Protocol
SLA Service Level Agreement
SLF Subscription Locator Function
SMI SNMP Structure of Management Information
SMIL Synchronized Multimedia Integration Language
SMPP Short Messaging Peer to Peer Protocol
SMPTE Society of Motion Picture and Television Engineers
SMS Short Message Service
SMSC Short Message Service Center
SMTP Simple Mail Transfer Protocol
SNMP Simple Network Management Protocol
SNR Signal to Noise Ratio
SOA Service Oriented Architecture
SOAP Simple Object Access Protocol
SONET Synchronous Optical Network
SP Signaling Point
SPC Stored Program Control
SPF Shortest Path First
SPOI Signalng Point of Interface
SQL Standard Query Langauge
SS6 Signaling System No. 6
SS7 Signaling System No. 7
SSF Service Switching Function
SSH Secure Shell
SSP Service Switching Point
STB Settop Box
STE Section Terminating Equipment

List of Acronyms xxxvii
STM Synchronous Transport Module
STP Signaling Transfer Point
STS Synchronous Transport Signal
SUT System Under Test
TAC Technical Assistance Center
TAS Telephony Application Server
TCAP Transaction Capabilities Part
TCP Transmission Control Protocol
TDM Time Division Multiplex
TDMA Time Division Multiple Access
TE Traffic Engineering
TID Target Identifier
TL1 Transaction Language 1
TMF Telecommunications Management Forum
TMN Telecommunications Management Network
TNMR Target Noise Margin
TOD Time of Day
TRAU Transcoding and Rate Adaption Unit
TrGW Transition Gateway
TSD Technical Service Description
TSI Time Slot Interchange
TTL Time to Live
UAS Unassigned service state
UAT User Acceptance Test
UBR Undefined Bit Rate
UDP User Datagram Protocol
UE User Equipment
UEQ Unequipped service state
UHDTV Ultra-High Definition TV
ULH Ultra Long Haul
UML Uniform Modeling Language
UMTS Universal Mobile Telecommunications System
UNE Unbundled Network Element
UNI User to Network Interface
UPSR Unidirectional Path Switched Rings
URI Uniform Resource Identifier
URL Uniform Resource Locator
UTC Universal Coordinated Time
UTRAN UMTS Radio Access Network
VBR Variable Bit Rate
VC Virtual Circuit
VDSL Very High Bit Rate Digital Subscriber Line
VHO Video Home Office
VLAN Virtual Local Area Network
VLR Visiting Local Register
VOD Video On Demand

xxxviii List of Acronyms
VP Virtual Path
VPLS Virtual Private LAN Service
VPN Virtual Private Network
VRF Virtual Routing and Forwarding
WAN Wide Area Network
WAP Wireless Application Protocol
WB Wideband
WLAN Wireless Local Area Network
WSDL Web Services Description Language
XML Extensible Markup Language
YAMS Yet Another Management System

1
Carrier Networks
We have come a long way in a short time. Instant communication arrived relatively recently
in the history of man, with the invention of the telegraph at the beginning of the nineteenth
century. It took three quarters of a century before we saw the ﬁrst major improvement in
mass communication, with the arrival of the telephone in 1874, and another half century
before a national network and transcontinental communication became common in the US.
But what was a middle class convenience years ago is now a common necessity. Today,
our worldwide communication Network is a model of egalitarian success, reaching into the
enclaves of the wealthy and the street vendors in villages of the developing world with equal
ease. Remarkably it remains largely in the hands of the private sector, and is held together
and prospers through forces of cooperation and competition that have served society well.
The Network is made up of literally millions of nodes and billions of connections, yet
when we choose to make a call across continents or browse a web site in cyberspace
we just expect it to work. I use the proper noun Network when referring to the global
highway of all interconnection carrier networks, such as Nippon Telephone and Telegraph
(NTT), British Telecom (BT), China Telecom, AT&T, Verizon, Deutsche Telekom, Orange,
Hurricane Electric, and many others, just as we use the proper noun Internet to refer to
the global public Internet Protocol (IP) network. The Internet rides on the Network. If
the Network were to fail, even within a city, that city would come to a halt. Instead of
purchasing fuel at the pump with a credit card, drivers would line up at the register while
the attendant tried to remember how to make change instead of waiting for the Network
to verify a credit card. Large discount retail outlets would have their rows of registers stop
and for all practical purposes the retailers would close their doors. Alarm systems and 911
emergency services would cease to function. Streets would become congested because trafﬁc
lights would no longer be synchronized. So what are the mechanisms that keep the Network
functioning 24 hours a day with virtually no failures?
1.1 Operating Global Networks
The global nature of networks is a seismic change in the history of modern man. In the
regulated world of the past franchise carriers completely dominated their national networks.
Global Networks: Engineering, Operations and Design, First Edition. G. Keith Cambron.
© 2013 John Wiley & Sons, Ltd. Published 2013 by John Wiley & Sons, Ltd.

4 Global Networks: Engineering, Operations and Design
Interconnection among networks existed for decades, but carriers did not over build each
other in franchise areas. That all changed in the latter decades of the twentieth century
as regulation encouraged competition and data services emerged. International commerce
and the rise of multinational companies created a demand for global networks operated by
individual carriers. Multinational companies wanted a single operator to be held accountable
for service worldwide. Many of them simply did not want to be in the global communications
business and wanted a global carrier to sort through interconnection and operations issues
inherent in far reaching networks.
In parallel with globalization was the move to the IP. The lower layers of the Open
System Interconnection (OSI) protocol stack grew because of global scale, and upper layer
complexity; the complexity increased with new services such as mobility, video, and the
electronic market, largely spurred by Internet services and technology. Operators were
forced to reexamine engineering and operating models to meet global growth and expand-
ing service demand. Before deregulation reliability and predictability were achieved through
international standards organizations, large operating forces, and highly structured and pro-
cess centric management regimes. Deregulation, competition, global growth, and service
expansion meant that model was no longer economic and could not respond to the rapid
introduction of new services and dramatic growths in traffic.
Operating models changed by applying the very advances in technology which drove
demand. Reliable networks were realized by reducing the number of failures, by shortening
the time for repair, or both. In the old model central offices were staffed with technicians
that could respond on short notice to failures, keeping restoral times low. In the new model
networks are highly redundant, well instrumented, constantly monitored, and serviced by a
mobile work force.
1.1.1 The Power of Redundancy
This section introduces the foundation of global network reliability, redundancy using a
simple systems model.
1.1.1.1 Simplex Systems
In the model following, a subscriber at A sends information i0 to a subscriber at B. The
information arrives at B via a communications system S0 as i1 after a delay of t (see
Figure 1.1).
Subscribers care about two things, the fidelity of the information transfer and transmission
time. Fidelity means that the information received, i1, should be as indistinguishable from
the information sent, i0, as possible. If we assume for simplicity that our communication
depends on a single system, S0, that fails on average once every year, and it takes 4 h to
S0
A B
i0 i1
t
Figure 1.1 Simplex operation.

Carrier Networks 5
get a technician on site and restore service, the service will be down for 4 h each year on
average, yielding a probability of failure of 4.6 × 10−5, or an availability of 99.954%. That
means we expect to fail about once for every 2000 attempts. For most communications
services that is a satisfactory success rate.
But real world connections are composed of a string of systems working in line, possibly
in the hundreds, any one of which can fail and impede the transfer. For a linear connection
of 100 such systems, our failure probability grows to 4.5 × 10−3
and availability drops to
95.5%. Approximately 1 in 20 attempts to use the system will fail.
1.1.1.2 Redundant Systems
The chances of success can be dramatically improved by using a redundant or duplex system
design, shown in Figure 1.2.
In the design two identical systems, S0 and S1 are each capable of performing the transfer.
One is active and the other is on standby. Since only one system affects the transfer, some
communication is needed between the systems and a higher authority is needed to decide
which path is taken.
In the duplex system design the probability of failure drops to 2.1 × 10−5 for 100 systems
in line, an improvement of more than 100× for an investment of 2×. Availability rises to
99.998%. We expect to fail only once in each 50 000 attempts.
Implicit in the model are some key assumptions.
• Failures are random and non-correlated. That is the probability of a failure in S1 is
unrelated to any failure experienced by S0. Since it’s likely the designs of the two systems
are identical, that assumption may be suspect.
• The intelligence needed to switch reliably and timely between the two systems is fail-safe.
• When S0 fails, Operations will recognize it and take action to repair the system within
our 4 h timeframe.
1.1.1.3 Redundant Networks
Redundancy works within network systems; their designs have two of everything essential
to system health: power supplies, processors, memory, and network fabric. Adopting reliable
network systems doesn’t necessarily mean networks are reliable. Network systems have to
be connected with each other over geographical expanses bridged by physical facilities to
build serviceable networks. Physical facilities, optical ﬁber, telephone cable, and coaxial
cable are exposed to the mischiefs of man and of nature. Dual geographically diverse routes
A B
t
S0
S1
i0 i1
Figure 1.2 Duplex model.

to identical network systems preserve service if the end nodes recognize that one route has
failed and the other is viable. Global networks rely on redundant systems within redundant
networks. The combination is resilient and robust, providing any failure is recognized early
and maintenance is timely and thorough.
The next sections explore this foundational model in more depth in an attempt to under-
stand how it works, and how it can break down in real networks.
1.1.2 The Virtuous Cycle
In the 1956 film Forbidden Planet, an advanced civilization called the Krell invents a factory
that maintains and repairs itself automatically. In the movie, although the Krell are long
extinct, the factory lives on, perpetually restoring and repairing itself. Some academics and
equipment suppliers promote this idea today using the moniker “self-healing network.” An
Internet search with that exact phrase yields 96 000 entries in the result; it is a popular idea
indeed. Academic papers stress mathematics, graphs, and simulations in search of elegant
proofs of the concept. Yet real networks that perform at the top of their class do so because
of the way people design, operate, and manage the technology. It is the blend of systems,
operations, and engineering that determine success or failure. Systems and people make
the difference. Figure 1.3 illustrates the Virtuous Cycle of equipment failure, identification,
and restoral.
The cycle begins at the top, or 12 o’clock, where the Network is operating in duplex
that is full redundancy with primary and alternate paths and processes. Moving in a clock-
wise direction, a failure occurs signified by the X, and the Network moves from duplex to
Notification
Sectionalization
Return to
Service
Test &
Verification
Fault
Mitigation
Duplex
Operation
Simplex
Operation
Fault
Isolation
Figure 1.3 Virtuous Cycle.

Carrier Networks 7
simplex operation, although no traffic is affected. While the Network is operating in simplex
it is vulnerable to a second failure. But before operators can fix the problem they need to
recognize it. Notification is the process whereby network elements send alarm notifications
to surveillance systems that alert network operators to the situation. Notifications seldom
contain sufficient information to resolve the problem, and in many situations multiple noti-
fications are generated from a single fault. Operators must sort out the relevant notifications
and sectionalize the fault to a specific network element in a specific location. The failed
element can then be put in a test status, enabling operators to run diagnostics and find the
root cause of the failure. Hardware faults are mitigated by replacing failed circuit packs.
Software faults may require a change of configuration or parameters, or restarting processes.
Systems can then be tested and operation verified before the system is restored to service,
and the network returns to duplex operation. Later chapters explore these steps in detail.
1.1.3 Measurement and Accountability
The Virtuous Cycle enables highly trained people to work with network systems to restore
complex networks quickly and reliably when they fail. But it does nothing to insure the
network has sufficient capacity to handle demands placed upon it. It does not by itself
give us any assurance the service the customer is receiving meets a reasonable standard.
We can’t even be sure network technicians are following the Virtuous Cycle diligently and
restoring networks promptly. To meet these goals a broader system of measurements and
accountability are needed. Carrier networks are only as good as the measurement systems
and the direct line of measurements to accountable individuals. This is not true in smaller
networks; when I speak with Information Technology (IT) and network engineers in smaller
organizations they view carriers as having unwarranted overhead, rules, and systems. In
small networks a few individuals have many roles and are in contact with the network daily.
They see relationships and causality among systems quickly; they recognize bottlenecks and
errors because of their daily touches on the network systems. Such a model does not scale.
Carrier networks have hundreds of types of systems and tens of thousands of network
elements. Carrier networks are more akin to Henry Ford’s production lines than they are
to Orville’s and Wilbur’s bicycle shop. Quality and reliability are achieved by scaling
measurement and accountability in the following ways.
• End service objectives – identify measurable properties of each service; commit to ser-
vice standards, communicate them, and put them into practice.
• Network systems measurement – using service objectives analyze each network and
network element and set measurable objectives that are consistent with the end to end
service standard.
• Assign work group responsibility – identify which work group is responsible for meet-
ing each of the objectives and work with them to understand how they are organized,
what skills they have and what groups they depend upon and communicate with regularly.
• Design engineering and management systems – systems should support people, not the
other way round. Find out what systems the teams already use and build on those if at
all possible. Don’t grow YAMS (yet another management system).

1.2 Engineering Global Networks
Changes in operations as dramatic as they have been are greater yet for the design and
engineering of global networks. Carriers in the US prior to 1982 were part of a vertically
integrated company, AT&T® or as it was commonly known, the Bell System. AT&T General
Departments operated the complete supply and operations chain for the US telecommunica-
tions industry. Wholly owned subsidiaries planned, designed, manufactured, installed, and
operated the network. AT&T’s integrated business included the operations support, billing,
and business systems as well. Carriers (the operating companies) had no responsibility for
equipment design or selection, and limited responsibility for network design. Today carriers
have full responsibility for planning, designing, installing, and operating their networks.
They also have a direct hand in determining the functionality and high level design of
network systems, and operations and business systems. The sections that follow summarize
responsibilities of carrier engineering departments.
1.2.1 Architecture
High level technology choices are the responsibility of Engineering. Engineering architects
analyze competing technologies, topologies, and functional delegation to determine the mer-
its and high level cost of each. Standards organizations such as ITU, IETF, and IEEE are
forums serving to advance ideas and alternatives. Suppliers naturally promote new ideas and
initiatives as well, but from their point of view. Long range plans generally describe the
evolution of networks but may not address practical and necessary design and operational
transition issues.
1.2.2 Systems Engineering
A wide range of responsibilities rest with systems engineers. They begin with high level
architectural plans and translate them into detailed speciﬁcations for networks and for the
individual network elements. Equipment recommendations, testing, certiﬁcation, and integra-
tion are all performed by these engineers. Operational support, IT integration, and network
design are performed by systems engineers as well.
1.2.3 Capacity Management
There are four general ways in which network capacity is expanded. Each is described in
the following.
1.2.3.1 Infrastructure Projects
Periodically major network augmentation is undertaken for a variety of reasons.
• Expansion into a new geography is a common trigger. A country adopts competitive rules
that enable over building the incumbent.

Carrier Networks 9
• Technology obsolescence, such as the shift from Frame Relay to IP networks leads to a
phased introduction of new technology. The new networks often must interwork with the
legacy technology making the transition more challenging.
• Carrier mergers or acquisitions are followed by network rationalization and integra-
tion. The numbers and types of network elements are winnowed out to ease operational
demands.
• New lines of business, such as Internet Protocol Television (IPTV) or content distribu-
tion, place new demands on the network requiring specialized technology design and
deployment.
1.2.3.2 Customer Wins
Major customer contract wins significantly increase demand at large customer locations, ren-
dering the existing capacity inadequate. Sometimes outsourcing of a Fortune 500 company
network can be accompanied by an agreement to transfer their entire network, employees,
and systems to the winning carrier. If they are of sufficient scope, the accompanying net-
work augmentations are treated as separate projects with dedicated engineering, operations,
and finance teams.
1.2.3.3 Capacity Augmentation
By far the most common reason for adding equipment and facilities to a network is the
continuous growth in demand of existing services and transport. For decades voice traffic
grew at a rate of about 4% each year. Data traffic and IP traffic specifically, have grown
at an annual rate of 30–50% for over three decades. With tens of thousands of network
systems and millions of facilities, automating demand tracking and capacity management is
one of the most resource intensive jobs in engineering.
1.2.3.4 Network Redesign
This is the most neglected, and often the most valuable tool available to network engineers.
The demand mechanisms cited above are all triggered by events. Capacity augmentation,
the most common engineering activity, is triggered when a facility or network element
falls below a performance threshold, such as packet discards or blocked calls. Network
engineers generally look at those links exceeding the accepted levels and order augmentation
or resizing. If a node nears exhaust, either because of port exhaust or throughput limits,
engineers order a new node and rearrange the traffic between that node and adjacent ones.
In effect they limit the problem and the solution space to a very narrow area, the particular
link or node that exceeded a threshold.
Network redesign broadens the scope to an entire region or community. It is performed
by systems engineers, not network engineers. It begins with A-Z (A to Z) traffic demand and
uses existing topology, link, and element traffic loads as an informational starting point, not
as a constraint. In voice networks Call Detail Records (CDRs) are a starting point since they
have the calling party (A) and the called party (Z). In IP networks netflow data, coupled

with routing information yield the necessary A-Z matrices. Redesigns are performed far
too infrequently and the results often reveal dramatic changes in traffic patterns that no
one recognized. Express routes, bypassing overloaded network elements, elimination of
elements, and rehoming often result in dramatic savings and performance improvements.
1.3 Network Taxonomy
To better understand network operations and engineering some grounding in networks and
systems is needed. Networks are best described as communications pathways that have both
horizontal and vertical dimensions. The horizontal dimension encompasses the different
types of networks which, when operated in collaboration deliver end to end services. The
vertical dimension is two tiered. Network elements, which carry user information and critical
signaling information, are loosely organized around the OSI seven-layer model, one of the
most successful design models in the last 50 years. As a word of warning, I use the terms
network system and network element interchangeably. Network system was in wide use
when I joined Bell Telephone Laboratories in the 1970s. Network element evolved in the
1990s and is institutionalized in the 1996 Telecommunications Act.
Above the network tier is a set of management systems that look after the health, perfor-
mance, and engineering of the network tier.
The distinction between network and management systems is almost universally a clear
line, as shown in Figure 1.4. Tests used to distinguish between the two systems types are
based on how transactions are carried.
1.3.1 Voice Systems
In the first half of the twentieth century transactions meant one thing, a wireline phone call.
A wireline call has six distinct stages.
1. The first stage is the service request. For a manual station set, that simply means taking
the receiver off the switch hook and listening for dial tone.
2. The second stage is the signaling stage in which the originator dials the called party’s
number.
Management Systems
Network Systems
End User (CPE) Access
Aggregation Backbone
Figure 1.4 Network and management systems.

Carrier Networks 11
3. In the third stage, call setup, a signaling connection is established between the originator
and the called party and a talking path is reserved.
4. Alerting or ringing the two parties takes place in the fourth stage. Audible ringing, some-
times called ringback, is applied to inform the calling party that the call has progressed.
Power ringing causes the called station to emit an audible ringing sound alerting the
called party.
5. For successful calls, where the called party answers, the fifth stage is the completion of
the final leg of a stable two way talking path.
6. In the sixth and last stage, the two parties conclude the call and hang up, after which the
end to end path is freed for other users.
These six stages are the same whether a call is originated or terminated by a human or a
machine. A wide range of technologies has been used over the years in each stage, but the
stages are more or less constant.
For voice services we can then distinguish among systems by applying the following tests:
• Does the system perform a critical function in one of the six stages of call processing?
• If the system is out of service, can existing subscribers continue to place and receive
calls?
Network systems when tested yield a yes to the first test and a no to the second. The time
frame for applying the tests is important; a reasonable boundary for applying these tests is
an hour. A local switching system is the one that gives dial tone and rings wireline phones.
If it fails, the effects are immediate. At a minimum no new originations or completions
occur because dial tone and ringing are not provided. In severe cases, calls in progress are
cut off.
A provisioning system is a counter example. That system is responsible for adding new
customers, removing customers, and making changes to existing customers’ services. It
does not perform a critical function in any of the six stages of call processing. If the
provisioning system fails, we simply can’t modify a customer’s service attributes until the
provisioning system returns to service. Existing calls, new originations, and terminations
are not affected, so the provisioning system is a management system, not a network system.
A second example is billing systems. If a billing system fails on a voice switching system,
calls are completed without charge. Unfortunately no one sounds a siren or sends a tweet to
let users know the billing system has failed and you can make free calls. The design choice
to let calls go free during billing system failure is a calculated economic decision. It is
cheaper to let them go free than it is to design billing systems to network system standards.
Occasionally losing some revenue is cheaper than building redundant fault tolerant recording
everywhere.
But what about the power systems in buildings where communications systems are
located? In general network systems operate directly off of DC batteries which are in turn
charged by a combination of AC systems and rectifiers. These hybrid power systems are
engineered to survive 4–8 hours when commercial AC power is lost. Most central offices
have back up diesel generators as well, enabling continuous operation indefinitely, assum-
ing the fuel supply is replenished. Cooling systems fall into the same category. These are
systems that do not affect the six stages of voice network systems if they remain failed for

an hour. So here is a class of systems that if failed, don’t affect calls within our hour time
frame, but can affect them after a few hours or possibly days, depending on the season.
These systems are in a third category, common systems. This is an eclectic group, covering
power, cooling, humidity, door alarms, and other systems that if failed, can imperil the
network systems within hours under the wrong circumstances.
1.3.2 Data Systems
The original tiered distinction and design for network and management systems came from
the wireline voice network, but it applies to data and mobile networks as well. Consider
two common data services upon which we can form our definitions, Internet browsing and
mobile texting, or Short Messaging Service (SMS). Browsing is generally performed by a
subscriber accessing content on the Internet by sending requests to a set of servers at a web
site. The subscriber unconsciously judges the service by the response time, measured from
the time the return key is stroked until the screen paints with the response. In the case of
SMS, the subscriber has no clear way of knowing when the message is delivered, or if it
is delivered at all. However, if a dialog between two SMS subscribers is underway, a slow
response or dropped message is likely to be noticed.
For mobile subscribers, many of the network systems that carry Internet service and SMS
are common. Our criterion for distinguishing between network and management systems
is set by the most demanding data service. Before the introduction of 4G mobile services
under the banner of LTE, Long Term Evolution, Internet access was the most demanding
service. But LTE, unlike prior mobile technologies, uses Voice over Internet Protocol (VoIP)
for voice service. With LTE data (VoIP data) delay tolerances become more unforgiving.
For data systems we can use our voice tests to distinguish among systems by applying
the same tests, with minor modifications:
• Does the system perform a critical function in the timely delivery of subscriber data?
• If the system is out of service, can existing subscribers continue to send and receive data?
The modifier timely was added to the first test. While it was not included in the comparable
test for voice service, it was implied. Recalling the six steps of call processing, untimely
delivery of any of the functions is tantamount to failure. If you pick up a wireline receiver
and have to wait over 10 seconds for dial tone, it’s likely one of two things will occur. If
you’re listening for a dial tone you may grow impatient and just hang up and try again.
If you don’t listen and just begin dialing, believing the network is ready, you’ll either be
routed to a recording telling you the call has failed, or you’ll get a wrong number. Consider
the case of not listening for dial tone before dialing your friend whose number is 679–1148.
You could be in for a surprise. Suppose you fail to listen for dial tone and begin dialing. If
dial tone is delivered after the 7, the first three digits the switching system records are 911.
Now you will have an unplanned conversation with the Public Service Answering Point
(PSAP) dispatcher. When Trimline®1
phones were first introduced by AT&T they caused
a rise in these wrong number events. Trimline was among the first station sets to place
the dial in the handset and people did not immediately become accustomed to putting the
1 Trimline is a registered trademark of AT&T.

Carrier Networks 13
phone to their ear, listening to dial tone, and then pulling the phone down to dial. Many
just picked up the phone and began to dial. Eventually they learned. Users can be trained.
1.3.3 Networks
Our communication infrastructure is actually a network of networks. I mean that in two
senses. Networks are different in kind, and different by serving area.
To say networks differ in kind is an economic and technical distinction. Networks evolve
to perform specific roles and the economics, topology, and service demands determine the
technologies used and the associated designs. So, local distribution networks that deliver
broadband and phone service to homes look far different than backbone networks carrying
Internet traffic between major peering points.
Residential distribution networks, whether they are designed by cable providers or telcos
tend to be asymmetrical, delivering more bandwidth toward the home, and they are very
sensitive economically. If you have to deliver that service to 30 million homes, a $10 saving
for each home matters.
Core IP networks carrying petabytes of traffic are at the other end of the technology
and economic spectra. They are symmetrical networks that are fully redundant and possess
sophisticated mechanisms for rerouting traffic in less than a second in the event of failure.
A failure in the core affects all customers and has severe economic impact. Spending more
in the core makes sense.
While the first distinction is according to kind, the second is by provider serving area. Each
service provider designs, builds, and operates their network, generally under a franchise of
the local communications regulator. The goal of universal service was established as U.S.
Policy in the Communications Act of 1934 [1]. Two cornerstones of the act were that
service should be extended to everyone, and that competing carriers should interconnect,
enabling a national network of independent carriers. Prior to regulation in the twentieth
century competing carriers often refused to interconnect. After 1934 interconnection and
cooperation became common practice in the industry. It naturally extended to the Internet,
although the U.S. Communications Act of 1934 does not directly apply to that network.
International cooperation and carrier interconnection are remarkable and beneficial prac-
tices that emerged from our twentieth century industrial society. Railroads in that era by
comparison are a different story. Different gauges continued well into the twentieth century
in Europe [2], inhibiting travel and commerce. When travelers reached an international bor-
der they often disembarked from one train and loaded aboard a different train because of
the differences in railroad gauges. We take for granted our ability to place a call anywhere
in the world, access any Internet site, and send e-mail and text messages to anyone any-
where. Interconnection only becomes news when it is taken away, as some Middle Eastern
countries experienced in the Arab Spring uprisings. We’ll explore network interconnection
in depth in a later chapter.
1.3.4 Network Systems
Network systems support the Virtuous Cycle in the following ways.
• Duplex operation – achieving non-stop processing in the face of internal and external
failures is founded upon redundant operation, and it requires the following functionality.

– Field replaceable units (FRUs) – failures occur on components with active electronics
and components with software. Active electronic components are housed in circuit
packs on assemblies that can be replaced in the field by technicians.
– Hot swappable cards – this takes FRUs one step further. Critical cards, such as system
controllers and network fabric cards must be able to be removed and inserted while the
system is in service, without affecting system performance. This is far more difficult
to design than one might think. We will explore the necessary design steps.
– Fault detection and spare switching – systems must detect faults and re-route traffic
to functioning cards, once the card is ready to process the load. Craft should also be
able to return traffic to the primary card once it has been verified as restored.
• Notification and sectionalization – effective implementation is contingent upon trouble
identification, correlation, and communication. Identification is achieved through hardware
and software monitoring of internal hardware and software systems, and external circuits.
Off-normal conditions must be resolved in a hierarchical structure that reports the most
likely cause to the upper layers. Sectionalization resolves off-normal conditions as local
or far-end related.
• Fault isolation and mitigation – fault detection and re-routing must happen automati-
cally in milliseconds under the control of the system. However isolation and mitigation
are performed by craft and rely on the software management of boards and ports. Object
management is closely tied to the notification process and the implementation of admin-
istrative and operational state management.
• Test, verification, and return to service – object management again plays a key role,
coupled with on board diagnostics.
The following chapters describe how network hardware, software, management systems,
and work group standards and practices make this cycle successful.
1.4 Summary
Networks expanded across the entire globe from humble beginnings 100 years ago. Today’s
networks interconnect billions of people with highly reliable voice, Internet, and video ser-
vices around the clock. Redundancy, fault tolerant systems, and operators and management
systems working together in the Virtuous Cycle detect and resolve failures before they
affect customer service. Network engineers monitor network elements and links, adding
capacity, and augmenting the networks on a daily basis. Systems engineers extend networks
with new technology and certify technology for seamless introduction into live networks.
Network systems can be upgraded and repaired in the field without service interruptions.
Hardware and software designs are defensive, meant to continue to operate in the face of
failures and traffic overload. As we’ll see in the next chapter, network systems are designed
to very different standards than support systems.
References
1. United States Federal Law Enacted as Public Law Number 416, Act of June 19 (1993).
2. Siddall, W.R. (1969) Railroad gauges and spatial interaction. Geographical Review, 59 (1), 29–57.

2
Network Systems Hardware
The history of communications systems is rich and storied [1] but not broadly known in
today’s engineering community. When I meet with university students I find they know
the origins of the Internet [2] but know little of the history of fiber optic communications.
Certainly taking nothing away from Vint Cerf or Robert Kahn, I can safely say that without
the laser, optic cable, and the Erbium Doped Fiber Amplifier (EDFA) the Internet would not
exist in anything approaching its current form. The laser and fiber optic cable were invented
at Bell Telephone Laboratories (BTL) and the EDFA was invented by Dr David N. Payne
and Dr Emmanuel Desurvire. While the EDFA was not invented at BTL, they were quick
to adopt it [3].
The global communications industry continues to spur invention and innovation with sup-
pliers, universities, and carriers around the globe. Just as the global communications network
provided the foundation for the Internet, we are now seeing computing and communication
technology merging to the point that the hardware systems are indistinguishable.
2.1 Models
There are three common models for network systems hardware.
1. The telco systems model is the oldest and most common one found in carrier networks.
It evolved from designs by the major carriers and equipment suppliers of the mid-
twentieth century. It is purpose built for each specific application. Physical characteristics
such as rack width, height, and operating temperature range were standardized early on.
Later specifications were expanded to include earthquake survivability, electromagnetic
susceptibility, and heat generation [4].
2. Open modular computing efforts began in the early 1990s. The goal was to develop a
standardized chassis that conforms to telco requirements but is flexible enough to support
a wide range of network systems and applications. The first widely adopted standard was
CompactPCI®; today the AdvancedTCA® or ATCA chassis is more widely used. These
systems promote innovation by solving the difficult hardware engineering problems,
laying a ready built foundation for software developers to focus their talents on new
services and systems.
Global Networks: Engineering, Operations and Design, First Edition. G. Keith Cambron.
© 2013 John Wiley & Sons, Ltd. Published 2013 by John Wiley & Sons, Ltd.

3. The blade center model is used for all-IP applications where general purpose servers, or
hosts, implement all facets of a service. Network systems built around this model can
use servers that meet the Network Equipment Building System (NEBS) standards [5],
or they can be built using data center standard servers. The latter are less expensive,
but require a more expensive common systems design to maintain narrower data center
environmental standards.
Table 2.1 is a summary of the attributes and applications of the three models. I’ve chosen
attributes that I believe represent the mainstream development and deployment of these sys-
tems. It’s quite possible that someone has developed an Integrated Services Digital Network
(ISDN) card for a modular computing system or even a general purpose host machine, but
that is an outlier and I haven’t represented those here (see Table 2.1).
These three models are discussed in the following sections.
2.2 Telco Systems Model
Network systems came of age in the second half of the twentieth century as voice switching
systems. Electromechanical systems, such as step-by-step and panel switches, adopted and
standardized in 1919 [6], were largely designed with distributed control. In the period
1950–1980 stored program control, or computer driven systems became the reference design
for network systems and we have never looked back [7]. Figure 2.1 is a reference diagram
of a stored program control network system. The diagram can be used as a reference for
the Western Electric No. 1 ESS [8], a voice switching system introduced in 1963, or for
Cisco’s carrier grade router, the CRS-3 [9], introduced in 2010.
2.2.1 Form and Function
Hardware form follows function in these systems. In the following sections distinctions
are drawn between telco systems and more general packet systems. While much of the
functionality is common for carrier grade systems, differences emerge for these two general
types of systems. Other differences are driven by the scope of deployment or the operations
and engineering model of the carrier.
2.2.1.1 Concentrators and Aggregators
Switches can be concentrators or aggregators; in both cases the fabrics are designed to gather
lower speed traffic and combine it onto higher speed links. A fine distinction can be made
between concentrators and aggregators. Aggregators are non-blocking; there are an equal
number of incoming channels and outgoing channels. An example is an M13 multiplexer. It
accepts 28 incoming DS1s and aggregates them onto a single DS3 carrying the 28 DS1s in a
different format. Concentrators have fewer outgoing channels than incoming channels, or at
least the potential to have fewer. Fabrics for both are often M x N switches, where M lower
speed ports are connected to N higher speed ports. The ratio of M to N varies from 2 : 1 to
500 : 1. A typical voice switch uses three stages of concentration. The first stage connects
M line input output (I/O) ports via concentration to the second stage. Some concentration
is achieved between the first and second stage, and then the rest of the concentration is
achieved between the second and third stages.

Network Systems Hardware 17
Table 2.1 Network systems models
Attribute Telco system Modular computing Blade center
Connectivity TDM, ATM, Ethernet,
Analog, SONET/SDH,
Frame Relay, ISDN,
FTTH, xDSL, DOCSIS,
and SS7
TDM, ATM, Ethernet,
Analog,
SONET/SDH, SS7,
Fiber Channel, and
InfiniBand
Ethernet, Fiber Channel,
and InfiniBand
Applications Multiplexers, TDM voice
systems, DWDM systems,
ROADMs, radio systems,
Network terminating
equipment (NTE), edge IP
routers, core P routers,
media gateways, and
mobility systems
Multiplexers, TDM
voice systems,
DWDM systems,
ROADMs, media
gateways, radio
systems, mobility
systems, voice
response systems,
and conferencing
systems
All management system:
EMS, NMS, OSS, BSS,
and billing systems. All
IP applications: VoIP
soft switches, feature
servers, and media
servers. Network
databases: SCP/NCPs,
HLRs, HSS, DNS,
LDAP, and ENUM.
Content delivery and
web services
applications. Data center
optimized routers.
Hardware Generally single sourced
from the supplier since it
is purpose built. There are
some exceptions, such as
D4 channel bank cards
which have multiple
sources. Often ASICs are
developed specifically for
these systems, and so the
hardware is not easily
replicated.
Chassis and circuit
cards are generally
available from a
range of suppliers
who comply with the
ATCA/PCI
standards.
Specialized cards
may be developed
for a small
specialized market.
There is greater use
of FPGA technology
and less use of
ASICs to build on
common hardware.
Generally hardware is
specific to each supplier,
but because these are
general purpose host
machines, supplier
interchangeable
hardware matters less.
Some effort has been
made to standardize and
support multi-vendor
designsa
Economics are
driven by the server
market, not the
telecommunications
market.
Software The admin or management
processor may use a small
version of Unix such as
BSD, or Linux. All the
other cards are likely to be
embedded systems without
an operating system, or
with a real-time OS such
as QNX or VxWorks to
achieve a more
deterministic work
schedule.
A wide range of
software is available.
Operating systems,
middleware, protocol
stacks, I/O boards
with embedded
system APIs, and
applications suite for
management are all
available. Integration
is the challenge.
Software ranges from
complete system
solutions for OSS/BSS
systems to extensive
middleware for web
services, databases,
messaging busses,
adaptors, and protocol
stacks.
(continued overleaf )

Table 2.1 (continued)
Attribute Telco system Modular computing Blade center
Key
advantages
Ideal for high volume single
purpose systems, such as
subscriber multiplexers
(DSLAMS and CMTS).
Also well suited to very
high capacity systems such
as 100G/Terabit routers
where proprietary ASICs
are critical to scale. Full
supplier support for these
systems is an advantage.
The flexible backplane
design with both
TDM and Ethernet
pathways make it
well suited for low
and mid volume time
to market solutions
and for
multi-purpose
platforms. Systems
are more likely to
ride Moore’s law
than telco systems.
Best suited for all IP
stateless applications,
such as web services and
databases. Economics
and availability are
superior if the solution
can be completely
software based. These
systems ride Moore’s
curve, and so you can
count on performance
and economic
improvement over time.
Disadvantages Time to market can be long
if you are the first
customer. The economics
for anything other than
high volume markets are
difficult. There is no
re-use of these systems
and performance
improvements come
slowly, if at all.
Software integration
can take longer than
planned and
achieving the desired
performance may
take time. Lifecycle
support can also be
challenging if
multiple parties are
providing different
parts of the solution
and the integrator is
not committed and
capable.
Stateless systems work
well in general, but
stateful systems can be
problematic, particularly
at scale. This approach
can lead to poor
functional distribution
and that in turn causes
availability and
performance
shortcomings that are
difficult to resolve.
a
See www.blade.org
EMS: Element Management System; NMS: Network Management System; OSS: Operations Support
System; BSS: Business Support System; SCP: Service Control Point; NCP: Network Control Point;
HLR: Home Location Register; HSS: Home Subscriber Server; DNS: Domain Name System; DWDM:
Dense Wave Division Multiplexing; ENUM: E.164 Number Mapping; OS: Operating System; API:
Application Programming Interface; CMTS: Cable Modem Termination System; FTTH: Fiber To The
Home; BSD: Berkeley Software Distribution.
Examples of Time Division Multiplex (TDM) concentrators are class 5 switching sys-
tems, digital cross connect (DSX) systems such as the Tellabs® Titan® series and TDM
multiplexers, such as the Alcatel DMX-3003.
In packet networks concentrators and aggregators generally serve as a point of traffic or
service management as well as aggregation. Load balancers can be included in this general
category, as well as layer 3/2 switches, session border controllers (SBCs) and broadband
remote access servers (BRASs).

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DEAN’s
Illustrated Farthing Books.
THE
TWO KINDS OF FEAR.
LONDON: DEAN & SON,
11, Ludgate Hill. 44

THE TWO KINDS OF FEAR.
What keeps back some wicked people from many evil things they would
wish to do? They are afraid of being punished.
What keeps good children, the children of God, from doing what they
know is sinful? They are afraid of sin.
There is a great difference, my dear children, between these two kinds of
fear—the fear of punishment, and the fear of sin. The first will only keep a
child from some sins, at some times; and if he often escapes being found
out, he will lose it almost altogether. But the fear of sin itself, because God
forbids it, will keep a child from any sin, and will be felt more powerfully
as he grows up in grace.
I will tell you a little story on this subject, which happened a good many
years ago, and may help you to understand what I mean.

Robert Wright was the son of a rich gentleman. He was a clever boy,
quick at his lessons, had been well taught, and knew well what was right
and wrong; but he had not learned to love and fear God. One morning, his
mother said, “Robert, to-morrow will be the first Sunday of the month. Here
is a shilling for you to put into the missionary box.” Robert put it into his
pocket, and often looked at it through the day and felt if it were safe. On his
way home to dinner, he passed a
shop where a variety of tarts and cakes were in the window. He stopped to
look, and then thought how he would like to have some. He felt if he had a
penny to buy one tart. No; but there was the shilling, and the thought came
into his mind, how much that would buy! “But would it be right to use it?
No; and if papa found it out, I should be severely punished?” He was just
going to turn away, when he thought again, “Why be afraid of being
punished? How can papa and mamma ever know?” He stayed and looked a

little longer, then ran into the shop, filled his pockets with good things, gave
the shilling, and went away.
I cannot say that he had much pleasure in eating them, after all; for his
conscience told him that he had done a great sin; and next day, when he saw
the missionary-box, he felt unhappy.
The same evening, when it was dark and cold, another little boy left his
home. It was no nice cheerful home, like Robert’s, with warm fires, and
bright lights. It was one small room, and in the grate only a few cinders. On
a bed of straw in a corner his mother lay very ill. As he went out, he said,
“Mother, try to sleep; I will not be late coming back.” He worked in a
factory not far off, and it being Saturday night, he knew he would not be
kept late. As he was coming home, weary and cold, thinking of his poor
mother, and how he would like to take something that would do her good,
his eye rested on some beautiful fruit at a shop-door outside the shop. He
saw that no one was near; he could touch them in passing. The temptation
was too great—the little fellow quickly put three lovely apples into his
pocket, and ran down the street. When he got to the lamp-post at the corner,
he took out the apples and looked at them. “They will make my mother
well, perhaps; but then, are they mine to give her? I could easily make her
think a lady gave them to me; but God would know.” Then, looking at them
again, he said aloud, “Thou God seest me! That is my Sabbath-school ticket
for to-morrow. No, mother must not have them. I cannot sin against God.”
He then ran back, and had just returned the apples into the basket, when
the shopman seeing him, thought he was stealing, seized him by the arm,
and dragged him in. The poor child, with tears, told the whole story, and
asked pardon for what he had done. The man had a feeling heart, and
children of his own; he was just at a loss to know whether to believe him or
not, when a kind old gentleman, who had seen all that passed, had followed
the boy, and heard what he said at the lamp-post, came in, and told him that
the story was true. He then bought the apples, and many other nice things,
and gave them to Harry, to take home to his mother, saying as he did so,
“Never forget what has happened this evening; and let your ticket for to-
morrow be your motto through life—‘Thou God seest me!’ and you are sure
to prosper.”
These two boys both lived to become men. Harry Brown grew up a
decided and consistent Christian. He was trusted and respected by all who

knew him; he got into good employment, married a pious wife, and saw his
poor mother end her days in his happy home. Robert Wright became a
prosperous man. He had a fine house, a carriage, and servants, and all that
money could buy. And yet often he did not look happy after all. And at last,
one morning, the town rang with the news of a dreadful event: Mr. Wright,
the rich merchant, had been found dead in his bed, with a bottle of poison
beside him. On looking at his papers, it was discovered that his business
was going wrong—that he had forged bills to a great amount; and now,
seeing he must be found out, the fear of punishment was more than he could
stand, and, by his own hands, he rushed into an eternal world.
Try to remember the lessons taught by this story? Pray to the Holy Spirit
to put the true fear of God and fear of sin into your hearts, for Jesus’ sake?
And remember, when temptation comes, “Thou God seest me!”

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