Industrial IoT Challenges Design

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Ismail Butun
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Ismail Butun Editor

Industrial
IoT
Challenges, Design Principles,
Applications, and Security
Industrial IoT
Ismail Butun
Editor

Industrial IoT
Challenges, Design Principles, Applications,
and Security
Editor
Ismail Butun
Chalmers University of Technology
Göteborg, Sweden

ISBN 978-3-030-42499-2 ISBN 978-3-030-42500-5 (eBook)

https://doi.org/10.1007/978-3-030-42500-5

© Springer Nature Switzerland AG 2020

This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of
the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation,
broadcasting, reproduction on microfilms or in any other physical way, and transmission or information
storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology
now known or hereafter developed.
The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication
does not imply, even in the absence of a specific statement, that such names are exempt from the relevant
protective laws and regulations and therefore free for general use.
The publisher, the authors and the editors are safe to assume that the advice and information in this book
are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or
the editors give a warranty, expressed or implied, with respect to the material contained herein or for any
errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional
claims in published maps and institutional affiliations.

This Springer imprint is published by the registered company Springer Nature Switzerland AG
The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland
In memory of my grandparents
and
my father Orhan Bütün . . .

To my mother Emine Bütün

İsmail Bütün
Foreword

I am honored to write this foreword for the book: “Industrial IoT: Challenges,
Design Principles, Applications, and Security.” The Editor of this book, Dr. Ismail
Butun, is a well-known researcher with impactful contributions in wireless com-
munications, computer networks, and network security for the past several years.
He published more than 35 scientific articles which were noticed by the research
community. His publications have already received more than 1000 citations along
with an H-index of 12. He demonstrates his knowledge in this edited book. I find
this book very useful for academicians and practitioners in the industry.
As the industrial revolution (a.k.a. Industry 4.0) continues at full pace, it is
indispensable to include all the benefits offered by the wireless technology, as it is
also evolving at a very fast pace. Besides, as the autonomous robots are invading
the factory floors at a rapid rate, they constitute another fleet of things in the
IoT to be wirelessly connected to each other and to the control center. Moreover,
after several decades of design and development, the smart grid and micro-grid
technologies have evolved from the traditional electric grid to the point where they
include remote monitoring and control, along with smart meters, sending gigabytes
of information per hour to the control center. Further, using the 4G/5G cellular and
low-power WAN wireless technologies, the Internet of Things (IoT) such as NB-
IoT and LoRaWAN are more flexible, deployable, scalable, and reachable than ever
before.
With all these advances, the Industrial IoT (so-called IIoT) concept is evolving
and comprises the primary focus of this book. It introduces all the recent tech-
nologies devised for the industrial networks, IoT, and IIoT domains, from factory
floor deployments to in-house applications. Therefore, it is not only for experts and
academicians in the field but also for the beginners and practitioners in the industry.

vii
viii Foreword

This book covers a wide range of topics, including but not limited to, the
digital twin, IoT-based industrial indoor/outdoor lighting systems, wireless com-
munications challenges and opportunities, decentralized computing, fog/edge/cloud
computing, data streaming, cyber-security, and intrusion detection.

Georgia Tech Prof. Ian F. Akyildiz

Atlanta, GA, USA
January 2020
Preface

We are all living in a connected world and Cisco predicts 500 Billion things of the
IoT to be further included in this connection; meaning more automation, remote
access and control to be infused in our everyday routines.
This book, “Industrial IoT: Challenges, Design Principles, Applications, and
Security,” aims at presenting the recent developments in the fields of industrial
networks, IoT, and IIoT domains. For this book, 18 chapter proposals were
submitted from the academicians and practitioners in the field. After careful reviews,
six chapters were finally accepted to be included in this book with an acceptance rate
of 33%.
Since readers of this book are likely to come from various backgrounds, being
aware of the implicit structure of this book might be helpful. The contributed chap-
ters in this book cover a broad range of topics related to IIoT networks, including
wired/wireless communication technologies, industrial applications, cyber-security,
and intrusion detection. The book consists of three parts and six chapters, which I
find a convenient way of presenting the overall material:
Part I consists of Chaps. 1 and 2 to introduce preliminaries, design principles, and
challenges of the IIoT. Chapter 1 introduces an overview of most of the networking,
communication, and ICT technologies available in the industrial networks, whereas
Chap. 2 presents wireless communication technologies that apply to IIoT and also
discussed their unique challenges.
Part II consists of Chaps. 3 and 4 to introduce automation trends and applications
of IIoT. Chapter 3 is dedicated to IoT-driven advances in industrial and commercial
smart buildings, especially new advances at IoT-based industrial indoor/outdoor
lighting systems. Chapter 4 introduces the automation trends in industrial networks
and IIoT, including the most famous digital twin concept.

ix
x Preface

Part III consists of Chaps. 5 and 6 to stress on the cyber-security of IIoT.

Chapter 5 presents the security of IIoT networks, especially within the decentralized
cloud computing settings of the IIoT. Finally, Chap. 6 concludes Part III and the
book by stressing on the detection of intrusions with data streaming concept.

Göteborg, Sweden Ismail Butun

January 2020
Acknowledgements

First of all, my special thanks go to Prof. Ian F. Akyildiz (Ken Byers Chair
Professor in Telecommunications, School of Electrical and Computer Engineering,
Georgia Institute of Technology, Atlanta, Georgia, USA) for reviewing my book and
providing his valuable feedback along with the Foreword section he has written.
I would like to express gratitude to my colleagues (especially to Magnus, Marina,
Tomas, and Vincenzo) at Network and Systems Division, Department of Computer
Science and Engineering, Chalmers University of Technology, for their courage and
support.
Generous academicians and practitioners helped in the thorough review process
of the book, including the authors of each chapter of this book. I appreciate each of
them for providing their expertise in this process along with their valuable time.
Especially, I would like to convey my gratitude to the following external
reviewers:
• Daniel dos Santos (Ph.D.), Forescout Technologies Inc. (USA)
• Lakshmikanth Guntupalli (Ph.D.), Ericsson Inc. (Sweden)
Last but not least, I would also like to thank my editor Susan Evans (Springer
Nature, USA) and her team for providing the editorial support needed while
preparing this book.

Goteborg, Sweden Ismail Butun

January 2020

xi
About the Editor

Ismail Butun (Ph.D.) received his B.Sc. and M.Sc. degrees in Electrical
and Electronics Engineering from Hacettepe University. He received his
second M.Sc. degree and Ph.D. degree in Electrical Engineering from the
University of South Florida in 2009 and 2013, respectively. He worked as an
Assistant Professor in years between 2015 and 2017 at Bursa Technical University
and Abdullah Gul University. From 2016 to 2019, he was employed as a post-
doctoral researcher by the University of Delaware and Mid Sweden University,
respectively. Since July 2019, he has been working as a post-doctoral fellow for
Network and Systems Division, Department of Computer Science and Engineering
at Chalmers University of Technology. He has more than 36 publications in
international peer-reviewed scientific journals and conference proceedings, along
with an H-index of 12 and I-index of 14.
Dr. Butun is a well-recognized academic reviewer by IEEE, ACM, and Springer,
who served for 39 various scientific journals and conferences in the review process
of more than 106 articles. He contributed as a track chair and session chair for
numerous international conferences and workshops, and performed as a technical
program committee (TPC) member for several international conferences organized
by IEEE, Springer, and ACM. His research interests include but not limited to
computer networks, wireless communications, WSNs, IoT, IIoT, LPWAN, LoRa,
cyber-physical systems, cryptography, network security, and intrusion detection.

xiii
Contents

Part I Preliminaries, Design Principles and Challenges

1 Industrial Networks and IIoT: Now and Future Trends. . . . . . . . . . . . . . . . . 3
Alparslan Sari, Alexios Lekidis, and Ismail Butun
2 Wireless Communication for the Industrial IoT . . . . . . . . . . . . . . . . . . . . . . . . . 57
Hasan Basri Celebi, Antonios Pitarokoilis, and Mikael Skoglund

Part II Automation Trends and Applications

3 IoT-Driven Advances in Commercial and Industrial Building
Lighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
Daniel Minoli and Benedict Occhiogrosso
4 Automation Trends in Industrial Networks and IIoT. . . . . . . . . . . . . . . . . . . . 161
David Camacho Castillón, Jorge Chavero Martín, Damaso
Perez-Moneo Suarez, Álvaro Raimúndez Martínez,
Victor López Álvarez

Part III Cyber Security

5 Security in Decentralised Computing, IoT and Industrial IoT . . . . . . . . . 191
Monjur Ahmed, Sapna Jaidka, and Nurul I. Sarkar
6 Intrusion Detection in Industrial Networks via Data Streaming . . . . . . . 213
Ismail Butun, Magnus Almgren, Vincenzo Gulisano,
and Marina Papatriantafilou

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239

xv
Contributors

The authors are listed according to the appearances of the chapters they have
written.
Alexios Lekidis Aristotle University of Thessaloniki, Thessaloniki, Greece
Alparslan Sari Cybersecurity Research Group, Department of Electrical and
Computer Engineering, University of Delaware Newark, DE, USA
Hasan Basri Celebi Electrical Engineering and Computer Science Department,
KTH Royal Institute of Technology, Stockholm, Sweden
Antonios Pitarokoilis Electrical Engineering and Computer Science Department,
KTH Royal Institute of Technology, Stockholm, Sweden
Mikael Skoglund Electrical Engineering and Computer Science Department, KTH
Royal Institute of Technology, Stockholm, Sweden
Daniel Minoli DVI Communications, New York, NY, USA
Benedict Occhiogrosso DVI Communications, New York, NY, USA
David Camacho Castillón GEA, Alcobendas, Madrid, Spain
Jorge Chavero Martín GEA, Alcobendas, Madrid, Spain
Damaso Perez-Moneo Suarez GEA, Alcobendas, Madrid, Spain
Álvaro Raimúndez Martínez GEA, Alcobendas, Madrid, Spain
Victor López Álvarez Telefónica I+D, Ronda de la Comunicación S/N Madrid,
Madrid, Spain
Monjur Ahmed Waikato Institute of Technology, Hamilton, New Zealand
Sapna Jaidka Waikato Institute of Technology, Hamilton, New Zealand
Nurul I. Sarkar Auckland University of Technology, Auckland, New Zealand

xvii
xviii Contributors

Ismail Butun Network and Systems Division, Department of Computer Science

and Engineering, Chalmers University of Technology, Göteborg, Sweden
Magnus Almgren Network and Systems Division, Department of Computer
Science and Engineering, Chalmers University of Technology, Göteborg, Sweden
Vincenzo Gulisano Network and Systems Division, Department of Computer
Science and Engineering, Chalmers University of Technology, Göteborg, Sweden
Marina Papatriantafilou Network and Systems Division, Department of Com-
puter Science and Engineering, Chalmers University of Technology, Göteborg,
Sweden
Acronyms

AI Artificial Intelligence
AMI Advanced Metering Infrastructure
AWGN Additive white Gaussian noise
BACnet Building Automation and Control Networks
BAS Building Automation System
BBU Baseband Unit
BCH Bose, Chaudhuri, and Hocquenghem code
Bi-AWGN Binary input AWGN channel
BLE Bluetooth Low Energy
BMS Building Management Systems
BYOD Bring-Your-Own-Device
CBA Component Based Automation
CER Codeword Error Rate
COB Communication Objects
COSEM COmpanion Specification for Energy Metering
COTS Commercial off the shelf
CPS Cyber-Physical Systems
CSF Cybersecurity Framework
CSMS Cyber Security Management System
CSP Cloud Service Provider
CV Computer Vision
DB Database
DBMS Database Management System
DLMS Device Language Message specification
DoS Denial-Of-Service
DDoS Distributed DoS
DIDS Distributed IDS
DNP3 Distributed Network Protocol-3
EDS Electronic Data Sheet
eMBB enhanced Mobile Broadband
EPL Ethernet Power-Link

xix
xx Acronyms

EtherCAT Ethernet for Control Automation Technology

GDPR General Data Protection Regulation by EU
HART Highway Addressable Remote Transducer protocol
HMI Human–Machine Interface
IaaS Infrastructure as a Service
IACS Industrial and Control System
ICT Information and Communications Technology
IDS Intrusion Detection Systems
IEC International Electrotechnical Commission
IIC Industrial Internet Consortium
IIoT Industrial Internet of Things
IoT Internet of Things
IIRA Internet Reference Architecture
IPS Intrusion Prevention System
IRT Isochronous Real Time
ISA International Society of Automation
ISO International Organization for Standardization
IT Information Technology
LAN Local Area Network
LDPC Low Density Parity Check code
LED Light Emitting Diode
LoRa Long-Range
LoRaWAN LoRa Wide Area Network
LPWA Low-Power Wide-Area
LPWAN Low-Power Wide-Area Networks
LTE Long-Term Evolution
MAC Medium Access Control
MITM Man-In-The-Middle
ML Machine Learning
ML Maximum-likelihood
mMTC massive Machine-Type Communication
MOS Metal-Oxide Semiconductor
M2M Machine to Machine
NB-IoT Narrow-Band IoT
NERC North American Electric Reliability
NFC Near Field Communication
NIST National Institute of Standards and Technology
NLP Natural Language Processing
NMT Network Management
OPC-UA Object Linking and Embedding for Process Control Unified
Architecture
OS Ordered Statistics
OSI Open System Interconnect
OT Operational Technology
RH Radio Head
Acronyms xxi

RLC Radio Link Control

PaaS Platform as a Service
PAN Personal Area Network
PDCP Packet Data Convergence Protocol
PDN Packet Data Network
PDO Process Data Object
PERA Purdue Enterprise Reference Architecture
PII Personal Identification Information
PIIoT Private IIoT
PLC Programmable Logic Controller
PLM Product Life-Cycle Management
PoE Power over Ethernet
QoS Quality of Service
RAMI4.0 Reference Architecture Model Industrie 4.0
RAT Remote Access Trojan
ROI Return of Investment
RTU Remote Terminal Unit
SaaS Software as a Service
SCADA Supervisory Control And Data Acquisition
SCNM Slot Communication Network Management
SDN Software-Defined Networking
SDO Service Data Object
SDR Software-Defined Radio
SIS Safety Instrument Systems
SNR Signal-to-Noise Ratio
SPE Stream Processing Engine
SVM Support Vector Machine
TCP Transmission Control Protocol
TMR Triple Modular Redundancy
UAV Unmanned Aerial Vehicles
UDP User Datagram Protocol
UE User Equipment
URLLC Ultra-Reliable Low-Latency Communication
VANET Vehicular Ad-hoc NETworks
VPN Virtual Private Network
WiFi Wireless Fidelity
WirelessHART Wireless version of the wired HART protocol
 Part I
Preliminaries, Design Principles
and Challenges
Chapter 1
Industrial Networks and IIoT: Now
and Future Trends

Alparslan Sari, Alexios Lekidis, and Ismail Butun

1.1 Introduction

Industry 4.0 revolution can be summarized with one word: ‘Connectivity’. Connec-
tivity will enable intelligent production with the proliferation of IIoT, cloud and big
data. Smart devices can collect various data about indoor location, outdoor position,
status information, usage patterns of the clients, etc. They have the ability not only
in gathering information, but also sharing the information amongst intended peers.
This will be beneficial in building an efficient manufacturing process in industrial
environments and also in helping with the planned preventative maintenance on
machinery. The other benefit is in identifying errors in the production pipeline
as quickly as possible since it is an important factor to reduce the production
and maintenance costs. Industry 4.0 is also focusing on optimization problems in
the industry by using smart devices to utilize data-driven services. Industry 4.0
and IIoT are used for complex task sharing, decision making based on collected
data, and remote access to machinery. Massive connectivity of the things and data
collection/sharing capability of those promotes security to be a major requirement
for the IIoT and Industry 4.0 concepts.

A. Sari ()
Cybersecurity Research Group, Department of Electrical and Computer Engineering, University
of Delaware, Newark, DE, USA
e-mail: asari@udel.edu
A. Lekidis
Aristotle University of Thessaloniki, Thessaloniki, Greece
e-mail: alekidis@csd.auth.gr
I. Butun
Network and Systems Division, Department of Computer Science and Engineering, Chalmers
University of Technology, Göteborg, Sweden
e-mail: ismail.butun@chalmers.se

© Springer Nature Switzerland AG 2020 3

I. Butun (ed.), Industrial IoT, https://doi.org/10.1007/978-3-030-42500-5_1
4 A. Sari et al.

Semiconductor transistors are introduced in the late 1940s and led the micropro-
cessor revolution in the 1970s. Intel produced MOS (Metal-Oxide Semiconductor)
based 4 bits 4004 microprocessor in 1971. It had 2250 transistors, 10,000 nm
MOS process and area of 12 mm2 . Figure 1.11 shows the plot of MOS transistor
counts by years. In the plots, the exponential increase of transistor counts validates
Moore’s law—transistors in an integrated circuit doubles every 2 years. Currently,
transistor counts jumped to 9–40 billion with 7–12 nm MOS process and area of
100–1000 mm2 . Figures 1.2 and 1.3 shows the evolution of the flash memory and
RAM with transistor count vs. date plot. Groundbreaking technological advances in
electronics started the information age which triggered major changes in commu-
nication technologies such as the Internet (connectivity), advanced machinery, and
software development, etc. Internet became the global communication hub, enabling
us to exchange information instantly. Advanced electronics produced smart devices
with a smaller size, which constitute today’s ‘things’ of IoT and IIoT.
IoT is the proliferation of smart devices such as tablets, phones, home appliances
such as TVs, and other sensors, etc. The benefit of using smart devices at home
would be reducing electric bills and time savings etc. Managing resource usage
based on sensors or scheduling heavy-duty tasks like running dishwasher, washing
machine or dryer when the electric consumption is the cheapest. IoT devices
are commonly used by the hobbyist or another consumer usage, and even in
industry. However, IIoT is designed for heavy-duty tasks such as manufacturing,
monitoring, etc. So, IIoT uses more precise and durable (heat/cold resistant) devices,
actuators, sensors, etc. Both IoT and IIoT have the same core principles such as
data management, network, security, cloud, etc. The main differences between IoT
and IIoT are scalability and the volume of generated data and how data has been
handled. Since IIoT devices generate massive amount of data, IIoT requires data
streaming, big data, machine learning or artificial intelligence practices. In a home
network, loss of the generated data would be trivial but in IIoT it is vital. The data
in IIoT should be more precise, continuous and sensitive. For instance, considering
a monitoring system in a nuclear power plant or a manufacturing facility should be
precise, continuous and sensitive to prevent hazardous events. The implementation
of IIoT in production lines or other industrial projects, companies are aiming to
reduce production or maintenance costs and improve efficiency, stability, safety, etc.
According to a key note speech2 delivered by Tom Bradicich,3 the seven
principles of the IIoT are provided as follows:
• Big amount of analog data: Many sensors generate analog data and this data
needs to be digitized to be further treated, analyzed and stored.
• Perpetual connectivity: Devices of the IIoT are always connected. There are
three key benefits of this: (1) Real-time monitoring is possible. (2) Continuous

1 Figures 1.1, 1.2, and 1.3 are illustrated based on data from: https://www.wikiwand.com/en/
Transistor_count.
2 Available at: https://www.youtube.com/watch?v=u3IaXvjDiOE.
3 Tom Bradicich, Ph.D., VP and GM, Servers and IoT Systems, Hewlett Packard Enterprise.
1 Industrial Networks and IIoT 5

Fig. 1.1 Figure shows

transistor counts in
microprocessors by date
between (a) 1971–1990 (top),
(b) 1991–2010 (middle), and
(c) 2010–2019 (bottom)
6 A. Sari et al.

Fig. 1.2 FGMOS transistor count in Flash memory over years with capacity increase

Fig. 1.3 Transistor count in RAM over years with capacity increase
1 Industrial Networks and IIoT 7

monitoring can help us to push software-firmware updates and fixes. (3) The
benefit of connected devices motivates individuals and organizations to purchase
products.
• Real-time data streaming: In the industry there are many safety mechanisms are
in use, and they are constantly generating data. Considering a nuclear power
plant, safety is of utmost critical from the operations point of view. Monitoring
requires real-time data streaming since a possible delay in data would cause
disastrous events. Hence, real-time data streaming and its aggregation are really
important.
• Data insights: Data insights (Spectrum of Value) in IoT seeks an answer to the
following question: “What are you trying to achieve?”
• Time-to vs. depth-of -insight trade-off: It is equivalent to the immediacy-of-
knowledge compared to the depth-of-knowledge. For instance, while monitoring
or analyzing a nuclear power plant data, immediate attention is required, whereas
an analysis of a scientific experiment data (data by CERN or NASA) can take
years to uncover scientific problems.
• Visibility from Big Data: Once the data is collected and stored in big data
environment, later on it should be available whenever it is needed for analysis
or other tasks.
• Edge computing: Data center class computing and analytics will be shifted
to edge (latency, bandwidth, cost, security, duplication, reliability, corruption,
compliance, and data sovereignty).
Improvement in big data and data streaming technologies enabled organizations
to use Artificial Intelligence (AI) and Machine Learning (ML) products more widely
in Industry 4.0. AI and ML applications are emerging in health, education, defense,
security, industry, etc. Many technology giants are pouring billions of dollars to
develop AI products such as autonomous cars (self-driving cars). Google, NVIDIA,
and others are developing computer vision-based self-driving algorithms along with
pedestrian detection, collision detection, etc. After the famous Urban Challenge
organized by DARPA, autonomous cars brought to the spotlight once again.
Automobile companies like Ford, General Motors, Nissan, Tesla, Mercedes, etc.
invested billions in R&D. Hundreds of other small companies are building Radars,
cameras, computing and communication systems, other sensors, etc. According to
the NVIDIA developers’ blog, autonomous cars are responsible for the generation of
an enormous amount of data involved with the following equipment: Radar, Sonar,
GPS, Lidar and cameras. A single forward-facing Radar (2800 MBits/s) generates
approximately 1.26 TB of data per hour. A two-megapixel camera (24 bits per
pixel) operating at 30 frames per second generates 1440 Mbits of data per second
(approximately 1TB data per hour [29].
In computer science, the following AI disciplines are utilized for various pur-
poses: Natural Language Processing (NLP), multi-agent systems (coordination and
collaboration—distributed resolution of problems, decision and reasoning, learning,
planning, simulation), human interactions (learning, chat-bots, expert systems),
computer vision, robotics, neuroscience and cognitive science (comprehension
8 A. Sari et al.

Fig. 1.4 IoT connectivity diagram (see footnote 4)

and simulation of the brain and nervous system), decision support (game theory,
uncertainty, explicability). It is assumed that using AI and ML algorithms will con-
tribute efficiency, cost reduction and effective management of industrial networks.
Therefore, following AI-based algorithms are also utilized frequently: heuristics,
logical programming, deduction and proof, reasoning, planning, scheduling, and
search.
The wired/wireless communication technologies that are being used for IIoT
networks are as shown in Figs. 1.44 and 1.5. They are also summarized here as
follows:
BLE Bluetooth Low Energy (BLE) is a wireless network technology of Personal
Area Networking (PAN), which is widely used in smart devices such as phones,
watches, wearable electronics, etc. BLE applications can be found in smart home,
health and sport industry. Many operating systems have native support for this
technology such as Android, BlackBerry, IOS, Linux, macOS, Windows, etc. BLE
uses 2.4 GHz radio frequencies.

Wi-Fi Wireless Fidelity (Wi-Fi) is an IEEE 802.11 based wireless network tech-
nology that is widely used with computers, tablets, smart devices, and vehicles such
as cars, buses, drones, etc.

4 Source: Postscapes and Harbor Research, available at: http://postscapes.com/what-exactly-is-the-

internet-of-things-infographic/.
1 Industrial Networks and IIoT 9

Fig. 1.5 A subset of IoT and IIoT communication technologies and protocols are illustrated

IPv4/IPv6 Internet Protocol versions 4/6 (IPv4/IPv6) can be considered as the

backbone of the Internet and other packet-switched based networks. It is one of
the most widely used technology in real life.
NFC Near Field Communication (NFC) is a communication technology which
devices can do connection approximately within 4 cm distance. NFC devices are
commonly used in electronic payments, key-cards, electronic tickets, etc. Many
smartphones are supporting this technology such as Android, Blackberry, IOS, etc.
Z-Wave/ZigBee Z-Wave is a low energy wireless protocol. ZigBee is also a low
power (low energy consumption) wireless communication protocol based on IEEE
802.15.4 standard to create PAN. Z-Wave/ZigBee are commonly used in home
automation, medical and industrial applications.
4G/LTE/5G 4G (fourth generation), LTE (Long Term Evolution), and 5G (fifth
generation) are dominating broadband cellular network technologies in nowadays
mobile telecommunications.
NB-IoT Recently, NB-IoT (Narrow Band Internet of Things) rapidly deployed by
mobile operators with the proliferation of IoT. NB-IoT is an LPWAN standard that
focuses on specifically low cost, energy-efficient, and indoor coverage.
10 A. Sari et al.

Fig. 1.6 A subset of IoT and IIoT use cases are illustrated

According to one of the leading sector representative5 of industrial investment

companies, IIoT will constitute one of the main pillars of Industry 4.0 and would
be described as follows: “The IIoT is a network of physical objects, systems
platforms and applications that contain embedded technology to communicate and
share intelligence with each other, the external environment and with people.” By
following this definition and the technological trends, economic predictors6 deduct
this conclusion: “The IIoT has the capacity to significantly boost the productivity
and competitiveness of industrial economies, but poor supporting conditions -
especially the lack of digital literacy - will hold many countries back”.
There will be plenty of application areas for IIoT ranging from smart cities to
precision agriculture, smart traffic to smart grid (the future of electric grid), and so
on, as shown in Fig. 1.6.
As discussed thoroughly in [11], IoT networks are vulnerable to various types of
attacks and weaknesses. Due to the absence of a physical line-of-defense, security
of such networks is of a big concern to the scientific community. Besides, as
cyber-attacks on industrial environments happen more frequently and their results

5 More information is available at: https://www.accenture.com/us-en/.

6 More information is available at: http://www.businesswire.com/news/home/20150120005160/en/
\Industrial-Internet-Boost-Economic-Growth-Greater-Government.
1 Industrial Networks and IIoT 11

are elevated to a devastating scale, effective intrusion detection is of the utmost

importance of industrial networks. Hence, research regarding Intrusion Detection
Systems (IDSs) for industrial networks is arising.
Prevention and early detection of intrusions are important, especially for mission-
critical industrial networks, such as smart grid systems.
For instance, data streaming concept provided in later chapters (Chap. 6), might
indeed enhance detection/response time in IDSs of the industrial networks. Hence,
future IIoT implementations can benefit from data streaming not only to reduce up-
streaming data size, but also to improve the security of the network especially by
enhancing the overall IDS response time.
Nowadays, there exist example applications in industrial networks (such as smart
grid systems), where sensors can generate data at rates of ∼3 GB (Gigabyte)’s
per hour [46, 54]. This is way much beyond the Ericsson’s and Bloomberg’s
expectation [38], which was ∼280 PB (Petabyte) of data to be generated by 680
million smart sensors per year (which is equivalent to 1 byte of information
per sensor per year). However, current client/server architecture of the traditional
networks is not capable of transferring, storing, and processing such big volume of
data. Hence, a sampled version of the generated data is used. Secondary benefit of
data streaming would be utilization of the unused portioned of the mentioned big
data from which IDSs would also benefit.

Centralized system architectures that gather all the data in the cloud to
process it cannot scale, both due to communication bandwidth and issues
of scalability of processing accumulated data; e.g. matching patterns of data
streams, on-the-fly, is a lower-latency process compared to searching for
patterns in terabytes/petabytes of stored data. Due to this, only small fractions
of generated data is actually being processed and used in such infrastructures.
With this reasoning, it is possible to see that besides helping resolving
bottleneck situations, stream processing can enable usage of more data for
applications in general and hence for IDSs as well.

So far, a brief overview of industrial networks and IIoT is presented in Sect. 1.1.
The rest of the chapter is structured as follows: Challenges faced by the practitioners
and the researchers while working on industrial networks are presented in Sect. 1.2.
Section 1.3 projects the future of industrial networks, including the technologies that
can be adopted by. Whereas, Sect. 1.4 presents enabling technologies for industrial
networks. Finally, Sect. 1.5 concludes the chapter.
12 A. Sari et al.

1.2 Challenges in Industrial Networks

Industrial networks are subject to many technical challenges that need to be

considered before, during, or after any implementation. These challenges are as
follows but not limited to:

1.2.1 Wireless Coexistence

Wireless coexistence stands for the safe operation of the devices that are
using wireless technology for the purpose of their communication. Especially,
‘signal interference’ is the main problem against coexistence of different
wireless communication standards, which might cause fading of the signals if
they are operating in the same frequency bands. This is on top of the existing
wireless communication problems such as reflection, refraction, diffraction,
scattering and free space path loss of the signals on air.7 Eventually, wireless
signal interference might cause packet drop, data loss, jitter and delay
in transmission, and an asynchronization between the two communicating
parties. Therefore, while designing IIoT, wireless coexistence of the devices
should be maintained, for instance by providing enough physical distance in
between the devices, and or by efficiently dividing and sharing the frequency
spectrum that is being used.

1.2.2 Latency

Latency, sometimes referred to as delay, (for the industrial networks) is the time
passed between the release time of a specific command and the start time of the
execution for that specific command. In some specific cases, it might be also referred
to as the time passed in between the data collection and the output of reaction.
For instance, even with the existence of cloud-end implementation, Ferrari et al.
have shown that, by using inexpensive industrial grade IIoT devices, the round-trip
latency of IIoT applications can be less than 300 ms for inter-continental commu-
nications and less than 50 ms for intra-continental communications [28]. Although,
any figure below 300 ms is considered as sufficient for telephony communication to
avoid undesired “talk-over” in conversations, every ms counts when the industrial
networks are considered. Especially real-time response might be needed for the
installments that are involving high speed machinery with safety requirements.

7 More reading available at: https://www.accoladewireless.com/wlan-wifi-signal-issues/.

1 Industrial Networks and IIoT 13

These important aspects (wireless coexistence and latency) of wireless communi-

cation, which is the enabling technology for IIoT and IoT networks, are thoroughly
discussed in Chap. 2 of this book. Especially, next generation wireless technolo-
gies, such as 5G and the ultra-reliable low-latency communication (URLCC) are
presented including the theoretical limits and the latency. The trade-offs in low-
latency communication for receivers with computational complexity constraints
are carefully discussed. Accordingly, it is stressed that, for mission critical IIoT
deployments such as the factory implementations requiring real-time response, the
latency is utmost important. With very stringent latency requirements and low-
complex IIoT receivers, the time required for the decoding of a packet (should not
constitute a computationally demanding operation) must be also considered while
analyzing the total latency.

1.2.3 Interoperability

Interoperability refers to the essential capability of various computerized merchan-

dises or systems to promptly connect and exchange data with each other, without
facing any restriction. There are two types of interoperability issues defined for
IIoT [31]:
1. The cross-layer interoperability (also known as heterogeneity), which is defined
as the orchestration of the Open System Interconnect (OSI) layers in a seamless
and burden-less way. Recently, this issue is solved by using two emerging vir-
tualization technologies; namely, Software-Defined Radio (SDR) and Software-
Defined Networking (SDN) [5]. On one hand, SDN is a network architecture
based on the separation of the control plane and the data plane which makes it
possible to obtain a directly programmable network. This separation unifies the
control plane over all kinds of network devices, making the network configured
and optimized based on the network status [26]. On the other hand, by providing
a higher degree of flexibility in designing wireless interfaces competent enough
to support multiple communications technologies, SDR [39] can be a solution
for addressing the interoperability problems. Akyildiz et al. [52] mentioned
that a vast number of devices in IoTs constitute a fundamental challenge
to the ubiquitous information transmissions through the backbone networks.
The heterogeneity of IoT devices and the hardware-based, inflexible cellular
architectures possess even greater challenges to enable efficient communication.
Hence, they offered an architecture on wireless SDN and proposed software-
defined gateways that jointly optimize cross-layer communication functionalities
between heterogeneous IoT devices and cellular systems.
2. The cross-system interoperability, which is defined as maintaining the continuous
operation of the networks and the systems within the existence of different
system architectures. E.g., part of an IIoT might consist of LoRa-based end-
devices and the other part might be dominated by Nb-IoT end-devices. This
Another random document with
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"Legion, we'll have to see what's down there," Foster said.
"We could come back later, with ropes and big insurance policies," I
said.
"But we won't," said Foster. "We've found what we were looking for—"
"Sure," I said, "and it serves us right. Are you sure you feel good
enough to make like Alice and the White Rabbit?"
"I'm sure. Let's go."

Foster thrust his legs into the opening, slid over the edge,
disappeared. I followed him. I eased down a few feet, glanced back
for a last look at the night sky, then lost my grip and slid. I hit bottom
hard enough to knock the wind out of me, and found myself lying on a
level floor.
"What is this place?" I dug the flashlight out of the rubble, flashed it
around. We were in a low-ceilinged room ten yards square. I saw
smooth walls, the dark bulks of massive shapes that made me think
of sarcophagi in Egyptian burial vaults—except that these threw back
highlights from dials and levers.
"For a couple of guys who get shy in the company of cops," I said,
"we've got a talent for doing the wrong thing. This is some kind of Top
Secret military installation."
"Impossible," Foster replied. "This couldn't be a modern structure, at
the bottom of a rubble-filled shaft—"
"Let's get out of here, fast," I said. "We've probably set off an alarm
already."
As if in answer, a low chime cut across our talk. Pearly light sprang
up on a square panel. I got to my feet, moved over to stare at it.
Foster came to my side.
"What do you make of it?" he said.
"I'm no expert on stone-age relics," I said. "But if that's not a radar
screen, I'll eat it."
I sat down in the single chair before the dusty control console, and
watched a red blip creep across the screen. Foster stood behind me.
"We owe a debt to that Ancient Sinner," he said. "Who would have
dreamed he'd lead us here?"
"Ancient Sinner, Hell," I said. "This place is as modernistic as next
year's juke box."
"Look at the symbols on the machines," Foster said. "They're identical
with those in the first section of the Journal."
"All pot-hooks look alike to me," I said. "It's this screen that's got me
worried. If I've got it doped out correctly, that blip is either a mighty
slow airplane—or it's at one hell of an altitude."
"Modern aircraft operate at great heights," Foster said.
"Not at this height," I said. "Give me a few more minutes to study
these scales...."
"There are a number of controls here," Foster said. "Obviously
intended to activate mechanisms—"
"Don't touch 'em," I said. "Unless you want to start World War III."
"I hardly think the results would be so drastic," Foster said. "Surely
this installation has a simple purpose, unconnected with modern wars
—but very possibly connected with the mystery of the Journal—and
of my own past."

"The less we know about this, the better," I said. "At least, if we don't
mess with anything, we can always claim we just stepped in here to
get out of the rain—"
"You're forgetting the Hunters," Foster said.
"Some new anti-personnel gimmick," I said.
"They came out of this shaft, Legion. It was opened by the pressure
of the Hunters, bursting out."
"Why did they pick that precise moment—just as we arrived?" I
asked.
"I think they were aroused," Foster said. "I think they sensed the
presence of their ancient foe."
I swung around to look at him.
"I see the way your thoughts are running," I said. "You're their Ancient
Foe, now, huh? Just let me get this straight: that means that umpteen
hundred years ago, you personally, had a fight with the Hunters—
here at Stonehenge. You killed a batch of them and ran. You hired
some kind of Viking ship and crossed the Atlantic. Later on, you lost
your memory, and started being a guy named Foster. A few weeks
ago you lost it again. Is that the picture?"
"More or less."
"And now we're a couple of hundred feet under Stonehenge—after a
brush with a crowd of luminous stinkbombs—and you're telling me
you'll be nine hundred on your next birthday."
"Remember the entry in the journal, Legion? 'I came to the place of
the Hunters, and it was a place I knew of old, and there was no hive,
but a Pit built by men of the Two worlds....'"
"Okay," I said. "So you're pushing a thousand."
I glanced at the screen, got out a scrap of paper, and scribbled a
rapid calculation. "Here's another big number for you. That object on
the screen is at an altitude—give or take a few percent—of thirty
thousand miles."

I tossed the pencil aside, swung around to frown at Foster. "What are
we mixed up in, Foster? Not that I really want to know. I'm ready to go
to a nice clean jail now, and pay my debt to society—"
"Calm down, Legion," Foster said. "You're raving."
"OK," I said, turning back to the screen. "You're the boss. Do what
you like. It's just my reflexes wanting to run. I've got no place to run
to. At least with you I've always got the wild hope that maybe you're
not completely nuts, and that somehow—"
I sat upright, eyes on the screen. "Look at this, Foster," I snapped. A
pattern of dots flashed across the screen, faded, flashed again....
"Some kind of IFF," I said. "A recognition signal. I wonder what we're
supposed to do now."
Foster watched the screen, saying nothing.
"I don't like that thing blinking at us," I said. "It makes me feel
conspicuous." I looked at the big red button beside the screen.
"Maybe if I pushed that...." Without waiting to think it over, I jabbed at
it.
A yellow light blinked on the control panel. On the screen, the pattern
of dots vanished. The red blip separated, a smaller blip moving off at
right angles to the main mass.
"I'm not sure you should have done that," Foster said.
"There is room for doubt," I said in a strained voice. "It looks like I've
launched a bomb from the ship overhead."

The climb back up the tunnel took three hours, and every foot of the
way I was listening to a refrain in my head: This may be it; this may
be it; this may be it....
I crawled out of the tunnel mouth and lay on my back, breathing hard.
Foster groped his way out beside me.
"We'll have to get to the highway," I said, untying the ten-foot rope of
ripped garments that had linked us during the climb. "There's a
telephone at the pub; we'll notify the authorities...." I glanced up.
"Hold it," I said. I grabbed Foster's arm and pointed overhead.
"What's that?"
Foster looked up. A brilliant point of blue light, brighter than a star,
grew perceptibly as we watched.
"Maybe we won't get to notify anybody after all," I said. "I think that's
our bomb—coming home to roost."
"That's illogical," Foster said. "The installation would hardly be
arranged merely to destroy itself in so complex a manner."
"Let's get out of here," I yelled.
"It's approaching us very rapidly," Foster said. "The distance we could
run in the next few minutes would be trivial by comparison with the
killing radius of a modern bomb. We'll be safer sheltered in the cleft
than in the open."
"We could slide back down the tunnel," I said.
"And be buried?"
"You're right; I'd rather fry on the surface."
We crouched, watching the blue glare directly overhead, growing
larger, brighter. I could see Foster's face by its light now.
"That's no bomb," Foster said. "It's not falling; it's coming down slowly
... like a—"
"Like a slowly falling bomb," I said. "And it's coming right down on top
of us. Goodbye, Foster. I can't claim it's been fun knowing you, but it's
been different. We'll feel the heat any second now. I hope it's fast."
The glaring disc was the size of the full moon now, unbearably bright.
It lit the plain like a pale blue sun. There was no sound. As it dropped
lower, the disc fore-shortened and I could see a dark shape above it,
dimly lit by the glare thrown back from the ground.
"The thing is the size of a ferry boat," I said.
"It's going to miss us," Foster said. "It will come to ground to the east
of us."
We watched the slender shape float down with dreamlike slowness,
now five hundred feet above, now three hundred, then hovering just
above the giant stones.
"It's coming down smack on top of Stonehenge," I yelled.

We watched as the vessel settled into place dead center on the

ancient ring of stones. For a moment they were vividly silhouetted
against the flood of blue radiance; then abruptly, the glare faded and
died.
"Foster," I said. "Do you think it's barely possible—"
A slit of yellow light appeared on the side of the hull, widened to a
square. A ladder extended itself, dropping down to touch the ground.
"If somebody with tentacles starts down that ladder," I said, in an
unnaturally shrill voice, "I'm getting out of here."
"No one will emerge," Foster said quietly. "I think we'll find, Legion,
that this ship of space is at our disposal."

"I'm not going aboard that thing," I said. "I'm not sure of much in this
world, but I'm sure of that."
"Legion," Foster said, "this is no twentieth century military vessel. It
obviously homed on the transmitter in the underground station, which
appears to be directly under the old monument—which is several
thousand years old—"
"And I'm supposed to believe the ship has been orbiting the Earth for
the last few thousand years, waiting for someone to push the red
button? You call that logical?"
"Given permanent materials—such as those the notebook is made of
—it's not impossible—or even difficult."
"We got out of the tunnel alive," I said. "Let's settle for that."
"We're on the verge of solving a mystery that goes back through the
centuries," Foster said. "A mystery that I've pursued, if I understand
the Journal, through many lifetimes—"
"One thing about losing your memory," I said. "You don't have any
fixed ideas to get in the way of your theories."
Foster smiled grimly. "The trail has brought us here. I must follow it—
wherever it leads."
I lay on the ground, staring up at the unbelievable shape, and the
beckoning square of light. "This ship—or whatever it is," I said: "It
drops down out of nowhere, and opens its doors—and you want to
walk right into the cosy interior—"
"Listen!" Foster cut in.

I heard a low rumbling then, a sound that rolled ominously, like distant
guns.
"More ships—" I started.
"Jet aircraft," Foster said. "From the bases in East Anglia probably. Of
course, they'll have tracked our ship in—"
"That's all for me!" I yelled, getting to my feet. "The secret's out—"
"Get down, Legion," Foster shouted. The engines were a blanketing
roar now.
"What for? They—"
Two long lines of fire traced themselves across the sky, curving down
—
I hit the dirt behind the stone in the same instant the rockets struck.
The shock wave slammed at the earth like a monster thunderclap,
and I saw the tunnel mouth collapse. I twisted, saw the red interior of
the jet tail-pipe as the fighter hurtled past, rolling into a climbing turn.
"They're crazy," I yelled. "Firing on—"
A second barrage blasted across my indignation. I hugged the muck
and waited while nine salvoes shook the earth. Then the rumble died,
reluctantly. The air reeked of high explosives.
"We'd have been dead now if we'd tried the tunnel," I gasped, spitting
dirt. "It caved at the first rocket. And if the ship was what you thought,
Foster, they've destroyed something—"
The sentence died unnoticed. The dust was settling and through it the
shape of the ship reared up, unchanged except that the square of
light was gone. As I watched, the door opened again and the ladder
ran out once more, invitingly.
"They'll try next time with atomics," I said. "That may be too much for
the ship's defenses—and it will sure as hell be too much for us—"
"Listen," Foster cut in. A deeper rumble was building in the distance.
"To the ship!" Foster called. He was up and running, and I hesitated
just long enough to think about trying for the highway and being
caught in the open—and then I was running, too. Ahead, Foster
stumbled crossing the ground that had been ripped up by the rocket
bursts, made it to the ladder, and went up it fast. The growl of the
approaching bombers grew, a snarl of deadly hatred. I leaped a still-
smoking stone fragment, took the ladder in two jumps, plunged into
the yellow-lit interior. Behind me, the door smacked shut.

I was standing in a luxuriously fitted circular room. There was a

pedestal in the center of the floor, from which a polished bar
projected. The bones of a man lay beside it. While I stared, Foster
sprang forward, seized the bar, and pulled. It slid back easily. The
lights flickered, and I had a moment of vertigo. Nothing else
happened.
"Try it the other way," I yelled. "The bombs will fall any second—" I
went for it, hand outstretched. Foster thrust in front of me. "Look!"
I stared at the glowing panel he was pointing to—a duplicate of the
one in the underground chamber. It showed a curved white line, with
a red point ascending from it.
"We're clear," Foster said. "We've made a successful take-off."
"But we can't be moving—there's no acceleration. There must be
sound-proofing—that's why we can't hear the noise of the bombers."
"No sound-proofing would help if we were at ground zero," Foster
said. "This ship is the product of an advanced science. We've left the
bombers far behind."
"Where are we going? Who's steering this thing?"
"It steers itself, I would judge," Foster said. "I don't know where we're
going, but we're well on the way. There's no doubting that."
I looked at him in amazement. "You like this, don't you, Foster? You're
having the time of your life."
"I can't deny that I'm delighted at this turn of events," Foster said.
"Don't you see? This vessel is a launch, or lifeboat, under automatic
control. And it's taking us to the mother ship."
"Okay, Foster," I said. "I'm with you." I looked at the skeleton on the
floor behind him, and added; "But I sure hope we have better luck
than the last passenger."

CHAPTER VII
It was two hours later, and Foster and I stood silent before a ten-foot
screen that had glowed into life when I touched a silver button beside
it. It showed us a vast emptiness of bottomless black, set thick with
corruscating points of polychrome brilliance that hurt to look at. And
against that backdrop: a ship, vast beyond imagining, blotting out half
the titanic vista with its bulk—
But dead.
Even from the distance of miles, I could sense it. The great black
torpedo shape, dull moonlight glinting along the unbelievable length
of its sleek flank, drifted: a derelict. I wondered for how many
centuries it had waited here—and for what?
"I feel," said Foster, "somehow—I'm coming home."
I tried to say something, croaked, cleared my throat.
"If this is your jitney," I said, "I hope they didn't leave the meter ticking
on you. We're broke."
"We're closing rapidly," said Foster. "Another ten minutes, I'd
guess...."
"How do we go about heaving to, alongside? You didn't come across
a book of instructions, did you?"
"I think I can predict that the approach will be automatic."
"This is your big moment, isn't it?" I said. "I've got to hand it to you,
pal; you've won out by pluck."
The ship appeared to move smoothly closer, looming over us, fine
golden lines of decorative filigree work visible now against the black.
A tiny square of pale light appeared, grew into a huge bay door that
swallowed us.
The screen went dark, there was a gentle jar, then motionlessness.
The port opened, silently.
"We've arrived," Foster said. "Shall we step out and have a look?"
"I wouldn't think of going back without one," I said. I followed him out
and stopped dead, gaping. I had expected an empty hold, bare metal
walls. Instead. I found a vaulted cavern, shadowed, mysterious, rich
with a thousand colors. There was a hint of strange perfume in the
air, and I heard low music that muttered among stalagmite-like
buttresses. There were pools, playing fountains, waterfalls, dim vistas
stretching away, lit by slanting rays of muted sunlight.
"What kind of place is it?" I asked. "It's like a fairyland, or a dream."
"It's not an earthly scheme of decoration," Foster said, "but I find it
strangely pleasing."

"Hey, look over there," I yelped suddenly, pointing. An empty-eyed

skull stared past me from the shadows at the base of a column.
Foster went over to the skull, stood looking down at it.
"There was a disaster here," he said. "That much is plain."
"It's creepy," I said. "Let's go back; I forgot to get film for my Brownie."
"The long-dead pose no threat," said Foster. He was kneeling,
looking at the white bones. He picked up something, stared at it.
"Look, Legion."
I went over. Foster held up a ring.
"We're onto something hot, pal," I said. "It's the twin to yours."
"I wonder ... who he was."
I shook my head. "If we knew that—and who killed him—or what—"
"Let's go on. The answers must be here somewhere." Foster moved
off toward a corridor that reminded me of a sunny avenue lined with
chestnut trees—though there were no trees, and no sun. I followed,
gaping.
For hours we wandered, looking, touching, not saying much but
saturated in wonder, like kids in a toy factory. We came across
another skeleton, lying among towering engines. Finally we paused in
a giant storeroom stacked high with supplies.
"Have you stopped to think, Foster," I said, fingering a length of rose-
violet cloth as thin as woven spider webs. "This boat's a treasure-
house of marketable items. Talk about the wealth of the Indies—"
"I seek only one thing here, my friend," Foster said; "my past."
"Sure," I said. "But just in case you don't find it, you might consider
the business angle. We can set up a regular shuttle run, hauling stuff
down—"
"You Earthmen," sighed Foster. "For you, every new experience is
immediately assessed in terms of its merchandising possibilities.
Well, I leave that to you."
"Okay okay," I said. "You go on ahead and scout around down that
way, if you want—where the technical-looking stuff is. I want to
browse around here for a while."
"As you wish."
"We'll meet at this end of the big hall we passed back there. Okay?"
Foster nodded and went on. I turned to a bin filled with what looked
like unset emeralds the size of walnuts. I picked up a handful, juggled
them lovingly.
"Anyone for marbles?" I murmured to myself.

Hours later I came along a corridor that was like a path through a
garden that was a forest, crossed a ballroom like a meadow floored in
fine-grained rust-red wood and shaded by giant ferns, and went
under an arch into the hall where Foster sat at a long table cut from
yellow marble. A light the color of sunrise gleamed through tall
pseudo-windows.
I dumped an armful of books on the table. "Look at these," I said. "All
made from the same stuff as the Journal. And the pictures...."
I flipped open one of the books, a heavy folio-sized volume, to a
double-page spread in color showing a group of bearded Arabs in
dingy white djellabas staring toward the camera, a flock of thin goats
in the background. It looked like the kind of picture the National
Geographic runs, except that the quality of the color and detail was
equal to the best color transparencies.
"I can't read the print," I said, "but I'm a whiz at looking at pictures.
Most of the books show scenes like I hope I never see in the flesh,
but I found a few that were made on Earth—God knows how long
ago."
"Travel books, perhaps," Foster said.
"Travel books that you could sell to any university on Earth for their
next year's budget. Take a look at this one."
Foster looked across at the panoramic shot of a procession of
shaven-headed men in white sarongs, carrying a miniature golden
boat on their shoulders, descending a long flight of white stone steps
leading from a colonnade of heroic human figures with folded arms
and painted faces. In the background, brick-red cliffs loomed up,
baked in desert heat.
"That's the temple of Hat-Shepsut in its prime," I said. "Which makes
this print close to four thousand years old. Here's another I
recognize." I turned to a smaller, aerial view, showing a gigantic
pyramid, its polished stone facing chipped in places and with a few
panels missing from the lower levels, revealing the cruder structure of
massive blocks beneath.
"That's one of the major pyramids, maybe Khufu's," I said. "It was
already a couple thousand years old, and falling into disrepair. And
look at this—" I opened another volume, showed Foster a vivid
photograph of a great shaggy elephant with a pinkish trunk upraised
between wide-curving yellow tusks.
"A mastodon," I said. "And there's a woolly rhino, and an ugly-looking
critter that must be a sabre-tooth. This book is old...."
"A lifetime of rummaging wouldn't exhaust the treasures aboard this
ship," said Foster.
"How about bones? Did you find any more?"
Foster nodded. "There was a disaster of some sort. Perhaps disease.
None of the bones was broken."

"I can't figure the one in the lifeboat," I said. "Why was he wearing a
necklace of bear's teeth?" I sat down across from Foster. "We've got
plenty of mysteries to solve, all right, but there are some other items
we'd better talk about. For instance: where's the kitchen? I'm getting
hungry."
Foster handed me a black rod from among several that lay on the
table. "I think this may be important," he said.
"What is it? a chop stick?"
"Touch it to your head, above the ear."
"What does it do—give you a massage?" I pressed it to my temple....
I was in a grey-walled room, facing a towering surface of ribbed
metal. I reached out, placed my hands over the proper perforations.
The housings opened. For apparent malfunction in the quaternary
field amplifiers, I knew, auto-inspection circuit override was necessary
before activation—
I blinked, looked around at the rod in my hand.
"I was in some kind of power-house," I said. "There was something
wrong with—with...."
"The Quaternary field amplifiers," Foster said.
"I seemed to be right there," I said. "I understood exactly what it was
all about."
"These are technical manuals," Foster said. "They'll tell us everything
we need to know about the ship."
"I was thinking about what I was getting ready to do," I said, "the way
you do when you're starting into a job; I was trouble-shooting the
Quaternary whatzits—and I knew how...."
Foster got to his feet and moved toward the doorway. "We'll have to
start at one end of the library and work our way through," he said. "It
will take us awhile, but we'll get the facts we need. Then we can
plan."

Foster picked a handful of briefing rods from the racks in the

comfortably furnished library and started in. The first thing we needed
was a clue as to where to look for food and beds, or for operating
instructions for the ship itself. I hoped we might find the equivalent of
a library card-catalog; then we could put our hands on what we
wanted in a hurry.
I went to the far end of the first rack and spotted a short row of red
rods that stood out vividly among the black ones. I took one out,
thought it over, decided it was unlikely that it was any more
dangerous than the others, and put it against my temple....
As the bells rang, I applied neuro-vascular tension, suppressed
cortical areas upsilon, zeta and iota, and stood by for—
I jerked the rod from my head, my ears still ringing with the shrill
alarm. The effect of the rods was like reality itself, but intensified, all
attention focussed single-mindedly on the experience at hand. I
thought of the entertainment potentialities of the idea. You could kill a
tiger, ride an airplane down in flames, face the heavyweight champion
—I wondered about the stronger sensations, like pain and fear.
Would they seem as real as the impulse to check the
whatchamacallits or tighten up your cortical thingamajigs?
I tried another rod.
At the sound of the apex-tone, I racked instruments, walked, not ran,
to the nearest transfer-channel—
Another:
Having assumed duty as Alert Officer, I reported first to coordination
Control via short-line, and confirmed rapport—
These were routine SOP's covering simple situations aboard ship. I
skipped a few, tried again:
Needing a xivometer, I keyed instruction-complex One, followed with
the code—

Three rods further along, I got this:

The situation falling outside my area of primary conditioning, I
reported in corpo to Technical Briefing, Level Nine, Section Four,
Sub-section Twelve, Preliminary. I recalled that it was now necessary
to supply my activity code ... my activity code ... my activity code.... (A
sensation of disorientation grew; confused images flickered like
vague background-noise; then a clear voice cut in:)
YOU HAVE SUFFERED PARTIAL PERSONALITY-FADE. DO NOT
BE ALARMED. SELECT A GENERAL BACKGROUND
ORIENTATION ROD FROM THE NEAREST EMERGENCY RACK.
ITS LOCATION IS ...
I was moving along the stacks, to pause in front of a niche where a U-
shaped plastic strip was clamped to the wall. I removed it, fitted it to
my head—
(Then:) I was moving along the stacks, to pause in front of a niche—
I was leaning against the wall, my head humming. The red stick lay
on the floor at my feet. That last bit had been potent: something about
a general background briefing—
"Hey, Foster!" I called, "I think I've got something...."
"As I see it," I said, "this background briefing should tell us all we
need to know about the ship; then we can plan our next move more
intelligently. We'll know what we're doing." I took the thing from the
wall, just as I had seemed to do in the phantom scene the red rod
had projected for me.
"These things make me dizzy," I said, handing it to Foster. "Anyway,
you're the logical one to try it."
He took the plastic shape, went to the reclining seat at the near end
of the library hall, and settled himself. "I have an idea this one will hit
harder than the others," he said.
He fitted the clamp to his head and ... instantly his eyes glazed; he
slumped back, limp.
"Foster!" I yelled. I jumped forward, started to pull the plastic piece
from his head, then hesitated. Maybe Foster's abrupt reaction was
standard procedure. In any case whatever harm this gadget could do
to Foster's brain had already been done. I might as well let the
process take its course. But I didn't like it much.
I went on reasoning with myself. After all, this was what the red rod
had indicated as normal procedure in a given emergency. Foster was
merely having his faded personality touched up. And his full-blown,
three-dimensional personality was what we needed to give us the
answers to a lot of the questions we'd been asking. Though the ship
and everything in it had lain unused and silent for forgotten millennia,
still the library should be good. The librarian was gone from his post
these thirty centuries, and Foster was lying unconscious, and I was
thirty thousand miles from home—but I shouldn't let trifles like that
worry me....

I got up and prowled the room. There wasn't much to look at except
stacks and more stacks. The knowledge stored here was fantastic,
both in magnitude and character. If I ever got home with a load of
these rods....
I strolled through a door leading to another room. It was small,
functional, dimly lit. The middle of the room was occupied by a large
and elaborate divan with a cap-shaped fitting at one end. Other
curious accoutrements were ranked along the walls. There wasn't
much in them to thrill me. But bone-wise I had hit the jackpot.
Two skeletons lay near the door, in the final slump of death. Another
lay beside the fancy couch. There was a long-bladed dagger beside
it.
I squatted beside the two near the door and examined them closely.
As far as I could tell, they were as human as I was. I wondered what
kind of men they had been, what kind of world they had come from,
that could build a ship like this and stock it as it was stocked.
The dagger that lay near the other bones was interesting: it seemed
to be made of a transparent orange metal, and its hilt was stamped in
a repeated pattern of the Two Worlds motif. It was the first clue as to
what had taken place among these men when they last lived: not a
complete clue, but a start.
I took a closer look at an apparatus like a dentist's chair parked
against the wall. There were spidery-looking metal arms mounted
above it, and a series of colored glass lenses. A row of dull silver
cylinders was racked against the wall. Another projected from a
socket at the side of the machine. I took it out and looked at it. It was
of plain pewter-colored plastic, heavy and smooth. I felt pretty sure it
was a close cousin to the chop sticks stored in the library. I wondered
what brand of information was recorded in it as I dropped it in my
pocket.
I lit a cigarette and went back out to where Foster lay. He was still in
the same position as when I had left him. I sat down on the floor
beside the couch to wait.

It was an hour before he stirred. He reached up, pulled off the plastic
head-piece, dropped it on the floor.
"Are you okay?" I asked.
Foster looked at me, his eyes travelling up to my uncombed hair and
down to my scuffed shoes. His eyes narrowed in a faint frown. Then
he said something—in a language that seemed to be all Z's and Q's.
"Enough surprises, Foster," I said hoarsely. "Talk American."
He stared into my eyes, then glanced around the room.
"This is a ship's library," he said.
I heaved a sigh of relief. Foster was watching my face. "What was it
all about?" I said. "What have you found out?"
"I know you," said Foster slowly. "Your name is Legion."
I nodded. I could feel myself getting tense again. "Sure, you know
me." I put a hand on his shoulder. "You remember: we were—"
He shook my hand off. "That is not the custom in Vallon," he said
coldly.
"Vallon?" I echoed. "What kind of routine is this, Foster?"
"Where are the others?"
"There's a couple of 'others' in the next room," I snapped. "But they've
lost a lot of weight. Outside of them there's only me—"