the industrial communication technology handbook (industrial information technology)

T H E

H A N D B O O K

INDUSTR IA LCOMMUNICATIONTECHNOLOGY

2005 by CRC Press

For thcoming BooksEmbedded Systems Handbook

Edited by Richard Zurawski

Electronic Design Automation for Integrated Circuits HandbookLuciano Lavagno, Grant Martin, and Lou Scheffer

Ser ies Ed i to rRICHARD ZURAWSKI

I N D U S T R I A L I N F O R M AT I O N T E C H N O L O G Y S E R I E S

2005 by CRC Press

T H E

H A N D B O O K

INDUSTR IA LCOMMUNICATIONTECHNOLOGYE d i t e d b y

R I C H A R D Z U R A W S K I

2005 by CRC Press

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Foreword

A handbook on industrial communication technology! What a challenge! When we know the complexityof industrial applications, the number of possible solutions, the number of standards, the variety ofapplications, of contexts, and of products!

The challenge can be expressed with just a few words: applications diversity, need for networking,integration of functions, and technologies.

Applications diversity: The applications concerned with industrial communications are known underthe following terms: process control, manufacturing and flexible systems, building automation, transportmanagement, utilities, and embedded systems, in trains, aircraft, cars, etc. All these applications needsimilar services, but in very different environments and also with very different qualities of service.

Need for networking: The need for networking is not new. Since the MAP and TOP projects, in thefield of automation, it is clear that the future of automation is really in distributed systems supportedby distributed (heterogeneous) communication systems. The sharing of information, the necessity ofinteroperability, and the necessity of abstraction levels are just some of the reasons why industrialcommunication has always been considered a major challenge.

Integration: In all the domains, integration is a key word meaning that all the functions in an enterpriseneed to be interconnected, in real time, as much as possible. This is only feasible through the use ofrobust communication systems, real-time features, and coherent design of the applications. With thedevelopment of ubiquitous computing and ambient intelligence, industrial communication applicationswill become the next challenge.

Technologies: Numerous technologies are available for use at different levels of control and commandand in all the services provided by a company; in addition, they exist for maintenance, supervision andmonitoring, diagnosis, spare parts management, and so on. Specific solutions are frequently dictated byspecific problems. The importance of standards cannot be overemphasized.

Wireless systems, fieldbuses and cell or plant networks, building automation, device buses and appli-cations, embedded systems, Internet technologies and related applications, security and safety, MACprotocols, and representative application domains are just some of the topics treated in this handbook.Methodology considerations for choosing and developing systems are also presented.

This handbook will become the major reference source for this domain. Setting aside some techno-logical details, the methods and principles presented will be relevant for years to come. Putting togethersuch a book would not be possible without the cooperation of a great number of authors, all specialistsin their fields and involved in the development of communication systems and applications, as well asmembers of the International Advisory Board. The Industrial Communication Technology Handbook is amust for industrial communication professionals.

Jean-Pierre ThomesseInstitute National Polytechnique de Lorraine

Nancy, France

2005 by CRC Press

vi

International Advisory Board

Jean-Pierre Thomesse, LORIA-INPL, France, Chair

Salvatore Cavalieri, University of Catania, Italy

Dietmar Dietrich, Vienna University of Technology, Austria

Jean-Dominique Decotignie, CSEM, Switzerland

Josep M. Fuertes, Universitat Politecnico de Catalunia, Spain

Jrgen Jasperneite, Phoenix Contact, Germany

Chris Jenkins, Proces-Data, U.K.

Ed Koch, Akua Control, U.S.

Thilo Sauter, Austrian Academy of Sciences, Austria

Viktor Schiffer, Rockwell Automation, Germany

Wolfgang Stripf, Siemens AG, Germany

2005 by CRC Press

vii

Preface

Introduction

Aim

The purpose of The Industrial Communication Technology Handbook is to provide a reference useful fora broad range of professionals and researchers from industry and academia interested in or involved inthe use of industrial communication technology and systems. This is the first publication to cover thisfield in a cohesive and comprehensive way. The focus of this book is on existing technologies used bythe industry, and newly emerging technologies and trends, the evolution of which is driven by the actualneeds and by the industry-led consortia and organizations.

The book offers a mix of basics and advanced material, as well as overviews of recent significantresearch and implementation/technology developments. The book is aimed at novices as well as experi-enced professionals from industry and academia. It is also suitable for graduate students. The book coversextensively the areas of fieldbus technology, industrial Ethernet and real-time extensions, wireless andmobile technologies in industrial applications, linking the factory floor with the Internet and wirelessfieldbuses, industrial networks security and safety, automotive applications, industrial automation appli-cations, building automation applications, energy systems applications, and others.

It is an indispensable companion for those who seek to learn more on industrial communicationtechnology and systems and for those who want to stay up to date with recent technical developmentsin the field. It is also a rich source of material for any university or professional development course onindustrial networks and related technologies.

Contributors

The book contains 42 contributions, written by leading experts from industry and academia directlyinvolved in the creation and evolution of the ideas and technologies treated in the book.

Over half of the contributions are from industry and industrial research establishments at the forefrontof the developments shaping the field of industrial communication technology, for example, ABB, BoschRexroth Corporation, CSEM, Decomsys, Frequentis, Phoenix Contact, PROCES-DATA, PSA Peugeot-Cit-roen, PROFIBUS International, Rockwell Automation, SERCOS North America, Siemens, and Volcano. Mostof the mentioned contributors play a leading role in the formulation of long-term policies for technologydevelopment and are key members of the industryacademe consortia implementing those policies.

The contributions from academia and governmental research organizations are represented by someof the most renowned institutions, such as Cornell University, Fraunhofer, LORIA-INPL, National Insti-tute of Standards (U.S.), Politecnico di Torino (Italy), Singapore Institute of Manufacturing Technology,Technical University of Berlin, and Vienna University of Technology.

Format

The presented material is in the form of tutorials, surveys, and technology overviews, combining funda-mentals with advanced issues, making this publication relevant to beginners as well as seasoned profes-

2005 by CRC Press

viii

sionals from industry and academia. Particular emphasis is on the industrial perspective, illustrated byactual implementations and technology deployments. The contributions are grouped in sections forcohesive and comprehensive presentation of the treated areas. The reports on recent technology devel-opments, deployments, and trends frequently cover material released to the profession for the first time.

Audience

The handbook is designed to cover a wide range of topics that comprise the field of industrial commu-nication technology and systems. The material covered in this volume will be of interest to a widespectrum of professionals and researchers from industry and academia, as well as graduate students,from the fields of electrical and computer engineering, industrial and mechatronic engineering, mechan-ical engineering, computer science, and information technology.

Organization

material to cover in a nutshell basics of data communication and IP networks. This material is intendedas a handy reference for those who may not be familiar with or wish to refresh their knowledge of some

is the main focus of the book and presents a comprehensive overview of the field of industrial commu-nication technologies and systems. Some of topics presented in this part have received limited coveragein other publications due to either the fast evolution of the technologies involved, material confidentiality,or limited circulation in case of industry-driven developments.

it is intended as supplementary reading for those who would like to refresh and update their knowledgewithout resorting to voluminous publications. This background is essential to understand the material

The section on fieldbus technology provides a comprehensive overview of selected fieldbuses. The focus ison the most widely used in industry and the most widely known. The presentation is not exhaustive, however.One of the limiting factors was the availability of qualified authors to write authoritatively on the topics.

tion to the fieldbus technology, comparison and critical evaluation of the existing technologies, and theevolution and emerging trends. This chapter is a must for anyone with an interest in the origins of thecurrent fieldbus technology landscape. It is also compulsory reading for novices to understand theconcepts behind fieldbuses.

the fieldbus technology. WorldFIP is one of the first fieldbuses, developed in France at the beginning

2005 by CRC Press

ing, A Perspective on Internet Routing: IP Routing Protocols and Addressing Issues, Fundamentals

and Internet Security.

Layer Protocols for Data Communications in Industrial Communication Networks, IP Internetwork-

in Quality of Service and Real-Time Transmission, Survey of Network Management Frameworks,

This section begins with Fieldbus Systems: History and Evolution, presenting an extensive introduc-

The The WorldFIP Fieldbus chapter was written by Jean-Pierre Thomesse, one of the pioneers of

The book is organized into two parts. Part 1, Basics of Data Communication and IP Networks, presents

of the concepts used extensively in Part 2. Part 2, Industrial Communication Technology and Systems,

presented in the chapters in Part 2. This part includes the following chapters: Principles of Lower-

Part 1 includes six chapters that present in a concise way the vast area of IP networks. As mentioned,

Part 2 includes five major sections: Field Area and Control Networks, Ethernet and Wireless Network

Field Area and Control Networks

Technologies, Linking Factory Floor with the Internet and Wireless Fieldbuses, Security and SafetyTechnologies in Industrial Networks, and Applications of Networks and Other Technologies.

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of the 1980s and widely used nowadays, particularly in applications that require hard real-time con-straints and high dependability. This is almost a personal record of a person involved in the develop-ment of WorldFIP.

A brief record of the origins and evolution of the FOUNDATION Fieldbus (H1, H2, and HSE) and

system profiles, and integration technologies such as GSD (general station description), EDD (electronicdevice description), and DTM (device type manager).

technology behind it, that has emerged as a result of the trend in automation technology toward modular,reusable machines and plants with distributed intelligence. PROFInet is an open standard for industrialautomation based on the industrial Ethernet. The material is presented by researchers from the Automa-

concept and the driving force for the technology development. The TTP (Time-Triggered Protocol) andTTA (Time-Triggered Architecture) had a profound impact on the development of safety-critical systems,particularly in the automotive industry. This is one of the most authoritative presentations on this topic.

The time-triggered CAN (TTCAN) protocol was introduced by Bosch in 1999 with the aim of making

Protocol) -based networks: DeviceNet, a CIP implementation employing a CAN data link layer; ControlNet,implementing the same basic protocol on new data link layers that allow for much higher speed (5 Mbps),strict determinism, and repeatability while extending the range of the bus (several kilometers with repeat-ers); and Ethernet/IP, in which CIP runs over TCP/IP. The chapter also introduces CIP Sync, which is aCIP-based communication principle that enables synchronous low-jitter system reactions without the needfor low-jitter data transmission. This is important in applications that require much tighter control of anumber of real-time parameters characterizing hard real-time control systems. The chapter also overviewsCIP Safety, a safety protocol that adds additional services to transport data with high integrity.

was written by the chairman of the International P-NET User Organization and the technical directorof PROCES-DATA (U.K.) Ltd., which provides the real-time PC operating system for P-NET.

over 6 million nodes installed, and a broad base of device manufacturers. The chapter also brieflyintroduces IP over INTERBUS and looks at data throughput for IP tunneling.

The IEEE 1394 FireWire, a high-performance serial bus, principles of its operation, and applications

and monitoring, and adding new devices to the network, to mention some activities) of fieldbus systems

2005 by CRC Press

its technical principles is presented in the chapter FOUNDATION Fieldbus: History and Features.The description of PROFIBUS (PROFIBUS DP) is presented in PROFIBUS: Open Solutions for the

in the fieldbus field, and it includes material on HART on PROFIBUS DP, application and master andWorld of Automation. This is a comprehensive overview of PROFIBUS DP, one of the leading players

The chapter Principles and Features of PROFInet presents a new automation concept, and the

Dependable time-triggered communication and architecture are presented in Dependable Time-tion and Drives Division of Siemens AG, the leading provider of automation solutions within Siemens AG.

Triggered Communication, written by Hermann Kopetz et al. Hermann Kopetz is the inventor of the

CAN suitable for the new needs of the automotive industry. This technology is introduced in Controller

protocol, including TTCAN.Area Network: A Survey. This chapter describes the main features of the Controller Area Network (CAN)

The chapter The CIP Family of Fieldbus Protocols introduces the following CIP (Common Industrial

The P-NET fieldbus is presented in the chapter The Anatomy of the P-NET Fieldbus. The chapter

The chapter INTERBUS Means Speed, Connectivity, Safety introduces INTERBUS, a fieldbus with

in the industrial environment are presented in Data Transmission in Industrial Environments Using

The issues involved in the configuration (setting up a fieldbus system) and management (diagnosisIEEE 1394 FireWire.

x

plug-and-participate concept and its implementations in the industrial environment.The section on fieldbus technology is concluded by an excellent chapter discussing the pros and cons

of selecting control networks for specific applications and application domains. The material in thischapter is authored by Jean-Dominique Decotignie. It includes a great deal of practical recommendationsthat can be useful for practicing professionals. It is the kind of material that cannot be easily found inthe professional literature.

Ethernet and Wireless Network Technologies

This section on Ethernet and wireless/mobile network technologies contains four chapters discussing theuse of Ethernet and its variants in industrial automation, as well as selected issues related to wirelesstechnologies. Ethernet is fast becoming a de facto industry standard for communication in factories andplants at the fieldbus level. The random and native CSMA/CD (carrier-sense multiple access with collisiondetection) arbitration mechanism is being replaced by other solutions allowing for deterministic behaviorrequired in real-time communication to support soft and hard real-time deadlines. The idea of usingwireless technology on the factory floor is appealing, since fieldbus stations and automation componentscan be mobile, and furthermore, the need for (breakable) cabling is reduced. However, the wirelesstransmission characteristics are fundamentally different from those of other media types, leading tocomparably high and time-varying error rates. This poses a significant challenge for fulfilling the hardreal-time and reliability requirements of industrial applications.

discusses various approaches to ensure real-time communication capabilities, to include those thatsupport probabilistic as well as deterministic analysis of the network access delay. This chapter alsopresents a brief description of the Ethernet protocol.

The practical solutions to ensure real-time communication capabilities using switched Ethernet are

switched Ethernet suitability in the context of industrial automation and presents practical solutionsobtained through R&D to address actual needs.

The issues involving the use of wireless and mobile communication in the industrial environment

wireless links and lower-layer wireless protocols for industrial applications. It also briefly discusses

wireless stations.

and limits of technologies such as Bluetooth, IEEE 802.11, and ZigBee for deployment in the industrialenvironments.

Linking Factory Floor with the Internet and Wireless Fieldbuses

The demand for process data availability at different levels of factory organizational hierarchy, fromproduction to the business level, has caused an upsurge in the activities to link the factory floor withthe intranet/Internet. The issues, solutions, and technologies for linking industrial environments withthe Internet and wireless fieldbuses are extensively discussed in this section.

2005 by CRC Press

are presented in Configuration and Management of Fieldbus Systems. This chapter also discusses the

This section begins with the chapter Approaches to Enforce Real-Time Behavior in Ethernet, which

(factory floor) are discussed in Wireless LAN Technology for the Factory Floor: Challenges andApproaches. This is a very comprehensive chapter dealing with topics such as error characteristics of

hybrid systems involving extending selected fieldbus technologies (such as PROFIBUS and CAN) with

The chapter Wireless Local and Wireless Personal Area Network Technologies for Industrial Deploy-ment concludes this section. This chapter discusses from the radio network perspective the potentials

presented in Switched Ethernet in Automation Networking. This chapter provides an evaluation of the

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discusses new trends involving industrial Ethernet.

protocol. This contribution comes from authors from industry involved directly in the relevant technol-ogy development.

The means for interconnecting wire fieldbuses to wireless ones in the industrial environment, various

presented by one of the leading authorities of the fieldbus technology.

Security and Safety Technologies in Industrial Networks

Security in the field area networks employed in the industrial environment is a major challenge. Therequirement for process data availability via intranet/Internet access opens possibilities for intrusion andpotential hostile actions to result in engineering system failures, including catastrophic ones if they involvechemical plants, for instance. These and safety issues are the focus of this section.

provides a comprehensive discussion of the issues involved, challenges, and existing solutions amenableto adaptation to industrial environments, and outlines a need for new approaches and solutions.

on the existing solutions and supporting technology in the context of PROFIBUS, one of the most widelyused fieldbuses in industrial applications. The material is presented by some of the creators of PROFIsafe.

CIP Safety, a safety protocol for CIP, is presented in the Field Area and Control Networks section in

Applications of Networks and Other Technologies

networks (synonymous with fieldbuses) and their applications to cover automotive communicationtechnology, building automation, manufacturing message specification in industrial communicationsystems, motion control, train communication, smart transducers, energy systems, and SEMI (Semicon-ductor Equipment and Materials International). This section tries to present some of the most represen-tative applications of field area networks outside the industrial controls and automation presented in theField Area and Control Networks section.

approaches, solutions, and technologies. The automotive industry is a very fast growing consumer offield area networks, aggressively adopting mechatronic solutions to replace or duplicate existing mechan-

protocols (TTP/C, FlexRay, and TTCAN) and operating systems and middleware services (OSEKTime

illustrating the design of a Steer-by-Wire system.The newly emerging standard and technology for automotive safety-critical communication FlexRay

2005 by CRC Press

with the Internet/intranet are discussed in Linking Factory Floor and the Internet. This chapter alsoThe issues and actual and potential solutions behind linking factory floor/industrial environments

overview of the use of the ANSI/EIA-852 standard to encapsulate the ANSI/EIA-709 control networkThe chapter Extending EIA-709 Control Networks across IP Channels presents a comprehensive

design alternatives, and their evaluation are presented in Interconnection of Wireline and WirelessFieldbuses. This is one of the most comprehensive and authoritative discussions of this challenge,

This section begins with the chapter Security Topics and Solutions for Automation Networks, which

The second paper in this section is PROFIsafe: Safety Technology with PROFIBUS, which focuses

This is the last major section in the book. It has eight subsections dealing with specialized field area

The CIP Family of Fieldbus Protocols.

and FTCom) used in automotive applications. The chapter also presents a comprehensive case study

tems, which gives an overview of the X-by-wire approach and introduces safety-critical communication

is presented in the chapter FlexRay Communication Technology. The material is among the most

The Automotive Communication Technologies subsection has four chapters discussing different

ical/hydraulic systems. This subsection begins with the chapter Design of Automotive X-by-Wire Sys-

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comprehensive and authoritative available at the time of this books publication, and it is written byindustry people directly involved in the standard and technology development.

The LIN (Local Interconnect Network) communication standard, enabling fast and cost-efficientimplementation of low-cost multiplex systems for local interconnect networks in vehicles, is presented

The Volcano concept and technology for the design and implementation of in-vehicle networks using

provides insight into the design and development process of an automotive communication network.Another fast-growing consumer of field area networks is building automation. At this stage, particularly

for office, commercial, and industrial complexes, the use of automation solutions offers substantialfinancial savings on costs of lighting and HVAC and can considerably improve the quality of the envi-ronment. There are other benefits as well. Relevant communication solutions for this application domainare presented in the subsection Networks in Building Automation. This subsection is composed of threecontributions, outlining the issues involved and the specific technologies currently in use.

of the pioneers of the concept of building automation and a technology developer.The details of the European Installation Bus (EIB), a field area network designed specifically for

contributed by one of the most active proponents of using field area networks in building automationand a co-founder of one of the largest research groups in this field, the Vienna University of Technology.

introduces the technical aspects of LonWorks networks, one of the main contenders for building auto-mation. It covers protocol, development environments, and tools.

successful international standard MMS (manufacturing message specification), which is an Open SystemsInterconnection (OSI) application layer messaging protocol designed for the remote control and moni-

MOTIP (MMS on top of TCP/IP) in development and operation of the virtual factory environment. Thechapter also discusses an MMS-based Internet monitoring system.

communication between digital motion controls, drives, input/output (I/O), and sensors. It includesdefinitions, a brief history, a description of SERCOS interface communication methodology, an intro-duction to SERCOS interface hardware, a discussion of speed considerations, information on conform-ance testing, and information on available development tools. A number of real-world applications arepresented and a list of sources for additional information is provided.

TheIEC 61375, adopted in 1999. It also discusses other European and U.S. initiatives in this field.

2005 by CRC Press

in The LIN Standard.

by Design. The material comes from the source: Volcano Communications Technologies AG. This chapter

An excellent introduction to issues, architectures, and available solutions is presented in The Use ofNetwork Hierarchies in Building Telemetry and Control Applications. The material was written by one

building automation purposes, are presented in EIB: European Installation Bus. This chapter was

the standardized CAN and LIN communication protocols are presented in Volcano: Enabling Correctness

Fundamentals of LonWorks/EIA-709 Networks: ANSI/EIA-709 Protocol Standard (LonTalk) chapter

toring of devices such as remote terminal units (RTUs), programmable logic controllers (PLCs), numer-

The subsection Manufacturing Message Specification in Industrial Automation focuses on the highly

ical controllers (NCs), robot controllers (RCs), etc. This section features two chapters: The StandardMessage Specification for Industrial Automation Systems: ISO 9506 (MMS), which gives a fairly com-prehensive introduction to the standard and illustrates its use; and Virtual Factory CommunicationSystem Using ISO 9506 and Its Application to Networked Factory Machine, which shows the use of

The chapter The SERCOS interface describes the international standard (IEC/EN 61491) for

IEC/IEEE Train Communication Network chapter presents details of the international standard

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1451 standards for connecting sensors and actuators to microprocessors, control and field area networks,and instrumentation systems. The standards also define the Transducer Electronic Data Sheet (TEDS),which allows for the self-identification of sensors. The IEEE 1451 standards facilitate sensor networking,a new trend in industrial automation, which, among other benefits, offers strong economic incentives.

The use of IEC 61375 (Train Communication Network) in substation automation is presented in

for various application domains.The last subsection and chapter in the Applications of Networks and Other Technologies section is

introduction to SEMI, providing an overview of the fundamentals of the SEMI Equipment CommunicationStandard, commonly referred to as SECS, its interpretation, the available software tools, and case studyapplications. The material was written by experts from the Singapore Institute of Manufacturing Technol-ogy who were involved in a number of SEMI technology developments and deployments.

Locating Topics

To assist readers with locating material, a complete table of contents is presented at the front of the book.Additionally, each chapter begins with its own table of contents. For further assistance, two indexes areprovided at the end of the book: an index of authors who contributed to the book, together with thetitles of their contributions, and a detailed subject index.

2005 by CRC Press

A Smart Transducer Interface Standard for Sensors and Actuators presents material on the IEEE

SEMI Interface and Communication Standards: An Overview and Case Study. This is an excellent

Applying IEC 61375 (Train Communication Network) to Data Communication in Electrical Substa-tions. This is in an interesting case study illustrating the suitability of some of the field area networks

Acknowledgments

I thank all members of the International Advisory Board for their help with structuring the book, selectionof authors, and material evaluation. I have received tremendous cooperation from all contributingauthors. I thank all of them for that. I also express gratitude to my publisher, Nora Konopka, and otherCRC Press staff involved in the books production, particularly Jessica Vakili, Elizabeth Spangenberger,and Gail Renard. My gratitude goes also to my wife, who tolerated the countless hours I spent preparingthis book.

Richard ZurawskiISA Corp

Santa Clara, CA

2005 by CRC Press

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The Editor

Dr. Richard Zurawski is president and CEO of ISA Corp., South San Francisco and Santa Clara, CA, acompany involved in providing solutions for industrial and societal automation. He is also chief scientistwith and a partner in a Silicon Valley-based start-up involved in the development of wireless solutionsand technology. Dr. Zurawski is a co-founder of the Institute for Societal Automation, Santa Clara, aresearch and consulting organization.

Dr. Zurawski has over 25 years of academic and industrial experience, including a regular appointmentat the Institute of Industrial Sciences, University of Tokyo, and full-time R&D advisor with KawasakiElectric, Tokyo. He has provided consulting services to Telecom Research Laboratories, Melbourne,Australia, and Kawasaki, Ricoh, and Toshiba Corporations, Japan.

He has participated in an IMS package: Formal Methods in Distributed Autonomous ManufacturingSystems and Distributed Logic Controllers, Task 8: Distributed Intelligence in Manufacturing Systems;

Intelligent Manufacturing Systems programs.Dr. Zurawskis involvement in R&D projects and activities in the past few years includes remote mon-

itoring and control, network-based solutions for factory floor control, network-based demand side man-agement, MEMS (automatic microassembly), Java technology, SEMI (Semiconductor Equipment andMaterials International) implementations, development of DSL telco equipment, and wireless applications.

Dr. Zurawski currently serves as an associate editor of the IEEE Transactions on Industrial Electronicsand Real-Time Systems: The International Journal of Time-Critical Computing Systems, Kluwer AcademicPublishers. He was a guest editor of three special sections in IEEE Transactions on Industrial Electronics:two sections on factory automation and one on factory communication systems. He has also been a guesteditor of a special issue of the Proceedings of the IEEE dedicated to industrial communication systems.In addition, Dr. Zurawski was invited by IEEE Spectrum to contribute material on Java technology toTechnology 1999: Analysis and Forecast Issue.

Dr. Zurawski is the series editor for The Industrial Information Technology Series, CRC Press, BocaRaton, FL, and has served as a vice president of the Institute of Electrical and Electronics Engineers(IEEE) Industrial Electronics Society (IES), chairman of the Factory Automation Council, and chairmanof the IEEE IES Ad Hoc Committee on IEEE Transactions on Factory Automation. He was an IESrepresentative to the IEEE Neural Network Council and IEEE Intelligent Transportation Systems Council.He was also on a steering committee of the ASME/IEEE Journal of Micromechanical Systems. In 1996, hereceived the Anthony J. Hornfeck Service Award from the IEEE Industrial Electronics Society.

Dr. Zurawski has established two IEEE events: the IEEE Workshop on Factory CommunicationSystems, the only IEEE event dedicated to industrial communication networks; and the IEEE Interna-tional Conference on Emerging Technologies and Factory Automation, the largest IEEE conference onfactory automation. He has served as a general, program, and track chair for a number of IEEE confer-ences and workshops.

2005 by CRC Press

Globeman 21 Group I: Global Product Management. He has also participated in a number of Japanese

Dr. Zurawski has published extensively on various aspects of control systems, industrial and factoryautomation, industrial communication systems, robotics, formal methods in the design of embeddedand industrial systems, and parallel and distributed programming and systems. Currently, he is preparingThe Embedded Systems Handbook, soon to be published by CRC Press.

2005 by CRC Press

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Contributors

Lus AlmeidaUniversidade de AveiroAveiro, Portugal

Herbert BarthelSiemens AGNrnberg-Moorenbrunn,

Germany

Gnther BauerVienna University of TechnologyVienna, Austria

Ralph BsgenSiemens AGNrnberg, Germany

Salvatore CavalieriUniversity of CataniaCatania, Italy

Gianluca CenaIEIIT-CNRTorino, Italy

Jean-Dominique Decotignie

Centre Suisse dElectronique et de Microtechnique

Neuchatel, Switzerland

Wilfried ElmenreichVienna University of TechnologyVienna, Austria

Joachim FeldSiemens AGNrnberg, Germany

A.M. FongSingapore Institute of

Manufacturing TechnologySingapore

Klaus FrommhagenFraunhofer Institute of Photonic

MicrosystemsDresden, Germany

K.M. GohSingapore Institute of


Zygmunt J. HaasCornell UniversityIthaca, New York

Scott C. HibbardBosch Rexroth CorporationHoffman Estates, Illinois

Helmut HlavacsUniversity of ViennaVienna, Austria

Mai HoangUniversity of PotsdamPotsdam, Germany

yvind HolmeideOnTime NetworksBillingstad, Norway

Jrgen JasperneitePhoenix Contact GmbH & Co.

KGBad Pyrmont, Germany

Ulrich JechtUJ Process AnalyticsBaden-Baden, Germany

Christopher G. JenkinsPROCES-DATA (U.K.) Ltd.Wallingford, Oxon, United

Kingdom

Svein JohannessenABB Corporate ResearchBillingstad, Norway

Wolfgang KampichlerFrequentis GmbHVienna, Austria

Wolfgang KastnerVienna University of TechnologyVienna, Austria

Dong-Sung KimKumoh National Institute of

TechnologyGumi-Si, South Korea

2005 by CRC Press

xviii

Hubert KirrmannABB Corporate ResearchBaden, Switzerland

Edward KochAkua ControlSan Rafael, California

Hermann KopetzVienna University of TechnologyVienna, Austria

Christopher KruegelVienna University of TechnologyVienna, Austria

Christian KurzUniversity of ViennaVienna, Austria

Ronald M. LarsenSERCOS North AmericaLake in the Hills, Illinois

Kang LeeNational Institute of Standards

and TechnologyGaithersburg, Maryland

Y.G. LimSingapore Institute of


Lucia Lo BelloUniversity of CataniaCatania, Italy

Dietmar LoyLOYTEC Electronics GmbHVienna, Austria

Peter LutzInterests Group SERCOS

interface e.V.Stuttgart, Germany

Kirsten MatheusCarmeq GmbHBerlin, Germany

Dietmar MillingerDECOMSYS Dependable

Computer SystemsVienna, Austria

Petra NauberFraunhofer Institute of Photonic


Nicolas NavetLORIAVandoeuvre-ls-Nancy, France

Georg Neugschwandtner

Vienna University of TechnologyVienna, Austria

Roman NossalDECOMSYS Dependable

Computer SystemsVienna, Austria

Paulo PedreirasUniversidade de AveiroAveiro, Portugal

Stefan PitzekVienna University of TechnologyVienna, Austria

Manfred PoppSiemens AGFrth, Germany

Antal RajnkVolcano AGTgerwilen, Switzerland

Thilo SauterAustrian Academy of SciencesWiener Neustadt, Austria

Uwe SchelinskiFraunhofer Institute of Photonic


Viktor SchifferRockwell AutomationHaan, Germany

Michael SchollesFraunhofer Institute of Photonic


Christian SchwaigerAustria Card GmbHVienna, Austria

Karlheinz SchwarzSchwarz Consulting Company

(SCC)Karlsruhe, Germany

Franoise Simonot-LionLORIAVandoeuvre-ls-Nancy, France

Tor SkeieABB Corporate ResearchBillingstad, Norway

Ye Qiong SongLORIAVandoeuvre-ls-Nancy, France

2005 by CRC Press

xix

Stefan SoucekLOYTEC Electronics GmbHVienna, Austria

Wilfried SteinerVienna University of TechnologyVienna, Austria

Wolfgang StripfSiemens AGKarlsruhe, Germany

Jean-Pierre ThomesseInstitut National Polytechnique

de Lorraine Vandoeuvre-ls-Nancy, France

O. TinSingapore Institute of


Albert TreytlVienna University of TechnologyVienna, Austria

Adriano ValenzanoIEIIT-CNRTorino, Italy

Peter WenzelPROFIBUS InternationalKarlsruhe, Germany

Andreas WilligUniversity of PotsdamPotsdam, Germany

Cdric WilwertPSA PeugeotCitroenLa Garenne Colombe, France

Hagen WoesnerTechnical University of BerlinBerlin, Germany

K. YiSingapore Institute of


Pierre A. ZuberBombardier TransportationTotal Transit SystemsPittsburgh, Pennsylvania

2005 by CRC Press

xxi

Contents

Industrial Communication Networks..............................................................................1-1

Andreas Willig and Hagen Woesner

2

3 A Perspective on Internet Routing: IP Routing Protocols and Addressing Issues.......3-1

4 Fundamentals in Quality of Service and Real-Time Transmission...............................4-1

5 Survey of Network Management Frameworks................................................................5-1

6 Internet Security ................................................................................................................6-1

Part 2 Industrial Communication Technology and Systems

Section I Field Area and Control Networks7 Fieldbus Systems: History and Evolution ........................................................................7-1

8 The WorldFIP Fieldbus .....................................................................................................8-1

9 FOUNDATION Fieldbus: History and Features ....................................................................9-1

10 PROFIBUS: Open Solutions for the World of Automation .........................................10-1

11 Principles and Features of PROFInet ............................................................................11-1

12 Dependable Time-Triggered Communication ..............................................................12-1

2005 by CRC Press

1 Principles of Lower-Layer Protocols for Data Communications in

Part 1 Basics of Data Communication and IP Networks

IP Internetworking ............................................................................................................2-1

Helmut Hlavacs and Christian Kurz

Wolfgang Kampichler

Christopher Kruegel

Mai Hoang

Lucia Lo Bello

Thilo Sauter

Jean-Pierre Thomesse

Salvatore Cavalieri

Ulrich Jecht, Wolfgang Stripf, and Peter Wenzel

Manfred Popp, Joachim Feld, and Ralph Bsgen

Hermann Kopetz, Gnther Bauer, and Wilfried Steiner

xxii

13 Controller Area Network: A Survey ...............................................................................13-1

Gianluca Cena and Adriano Valenzano

14 The CIP Family of Fieldbus Protocols ...........................................................................14-1

Viktor Schiffer

15 The Anatomy of the P-NET Fieldbus .............................................................................15-1

Christopher G. Jenkins

16 INTERBUS Means Speed, Connectivity, Safety.............................................................16-1

Jrgen Jasperneite

17 Data Transmission in Industrial Environments Using IEEE 1394 FireWire..............17-1

Michael Scholles, Uwe Schelinski, Petra Nauber, and Klaus Frommhagen

18 Configuration and Management of Fieldbus Systems..................................................18-1

Stefan Pitzek and Wilfried Elmenreich

19 Which Network for Which Application.........................................................................19-1


Section II Ethernet and Wireless Network Technologies20 Approaches to Enforce Real-Time Behavior in Ethernet .............................................20-1

Paulo Pedreiras and Lus Almeida

21 Switched Ethernet in Automation Networking .............................................................21-1

Tor Skeie, Svein Johannessen, and yvind Holmeide

22 Wireless LAN Technology for the Factory Floor: Challenges and Approaches..........22-1

Andreas Willig

23 Wireless Local and Wireless Personal Area Network Technologies for Industrial Deployment ......................................................................................................................23-1

Kirsten Matheus

Section III Linking Factory Floor with the Internet and Wireless Fieldbuses24 Linking Factory Floor and the Internet.........................................................................24-1

Thilo Sauter

25 Extending EIA-709 Control Networks across IP Channels..........................................25-1

Dietmar Loy and Stefan Soucek

26 Interconnection of Wireline and Wireless Fieldbuses..................................................26-1


Section IV Security and Safety Technologies in Industrial Networks27 Security Topics and Solutions for Automation Networks............................................27-1

Christian Schwaiger and Albert Treytl

2005 by CRC Press

xxiii

28 PROFIsafe: Safety Technology with PROFIBUS ...........................................................28-1

Wolfgang Stripf and Herbert Barthel

Section V Applications of Networks and Other Technologies

Automotive Communication Technologies

29 Design of Automotive X-by-Wire Systems ....................................................................29-1

Cdric Wilwert, Nicolas Navet, Ye Qiong Song, and Franoise Simonot-Lion

30 FlexRay Communication Technology ............................................................................30-1

Dietmar Millinger and Roman Nossal

31 The LIN Standard ............................................................................................................31-1

Antal Rajnk

32 Volcano: Enabling Correctness by Design.....................................................................32-1

Antal Rajnk

Networks in Building Automation

33 The Use of Network Hierarchies in Building Telemetry and ControlApplications......................................................................................................................33-1

Edward Koch

34 EIB: European Installation Bus ......................................................................................34-1

Wolfgang Kastner and Georg Neugschwandtner

35 Fundamentals of LonWorks/EIA-709 Networks: ANSI/EIA-709 ProtocolStandard (LonTalk)..........................................................................................................35-1

Dietmar Loy

Manufacturing Message Specification in Industrial Automation

36 The Standard Message Specification for Industrial Automation Systems:ISO 9506 (MMS) ..............................................................................................................36-1

Karlheinz Schwarz

37 Virtual Factory Communication System Using ISO 9506 and Its Application to Networked Factory Machine...........................................................................................37-1

Dong-Sung Kim and Zygmunt J. Haas

Motion Control

38 The SERCOS interface..................................................................................................38-1

Scott C. Hibbard, Peter Lutz, and Ronald M. Larsen

Train Communication Network

39 The IEC/IEEE Train Communication Network ............................................................39-1

Hubert Kirrmann and Pierre A. Zuber

2005 by CRC Press

xxiv

Smart Transducer Interface

40 A Smart Transducer Interface Standard for Sensors and Actuators ...........................40-1

Kang Lee

Energy Systems

41 Applying IEC 61375 (Train Communication Network) to Data Communication in Electrical Substations ..................................................................................................41-1

Hubert Kirrmann

SEMI

42 SEMI Interface and Communication Standards: An Overview and Case Study........42-1

A.M. Fong, K.M. Goh, Y.G. Lim, K. Yi, and O. Tin

2005 by CRC Press

1

-1

1

Basics of Data Communication and

IP Networks

1 Principles of Lower-Layer Protocols for Data Communications in Industrial Communication Networks................................................................................................1-1

Andreas Willig and Hagen Woesner

2 IP Internetworking ............................................................................................................2-1

Helmut Hlavacs and Christian Kurz

3 A Perspective on Internet Routing: IP Routing Protocols and Addressing Issues.......3-1

Lucia Lo Bello

4 Fundamentals in Quality of Service and Real-Time Transmission...............................4-1

Wolfgang Kampichler

5 Survey of Network Management Frameworks................................................................5-1

Mai Hoang

6 Internet Security ................................................................................................................6-1

Christopher Kruegel

3077_book.fm Page 1 Friday, November 19, 2004 11:21 AM

2005 by CRC Press

1-1

1Principles of Lower-Layer

Protocols for DataCommunications in

Industrial CommunicationNetworks

1.1 Introduction ........................................................................1-11.2 Framing and Synchronization............................................1-2

and Frame Synchronization in the PROFIBUS

1.3 Medium Access Control Protocols.....................................1-6

Protocols

1.4 Error Control Techniques.................................................1-15

1.5 Flow Control Mechanisms................................................1-18

1.6 Packet Scheduling Algorithms..........................................1-20

1.7 Link Layer Protocols .........................................................1-22

References .....................................................................................1-24

1.1 Introduction

In packet-switched networks the lower layers (data link layer, medium access control layer, physicallayer) have to solve some fundamental tasks to facilitate successful communication. The lower layersare concerned with communication between neighbored stations, in contrast to the layers above (net-working layer, transport layer), which are concerned with end-to-end communications over multipleintermediate stations.

Andreas WilligUniversity of Potsdam

Hagen WoesnerTechnical University of Berlin

2005 by CRC Press

Bit Synchronization Frame Synchronization Example: Bit

Requirements and Quality-of-Service Measures Design Factors Random Access Protocols Fixed-Assignment Protocols Demand-Assignment Protocols Meta-MAC

Open-Loop Approaches Closed-Loop Approaches Hybrid Approaches Further Countermeasures

XON/XOFF and Similar Methods Sliding-Window Flow Control Further Mechanisms

Priority Scheduling Fair Scheduling

Bit and Frame Synchronization Medium Access Control

Protocols Packet SchedulingProtocols Error Control Flow Control Link Layer

The HDLC Protocol Family The IEEE 802.2 LLC Protocol

1-2 The Industrial Communication Technology Handbook

The lower layers communicate over physical channels, and consequently, their design is stronglyinfluenced by the properties of the physical channel (bandwidth, channel errors). The importance of thelower layers for industrial communication systems is related to the requirement for hard real-time andreliability guarantees: if the lower layers are not able to guarantee successful delivery of a packet/frame*within a prescribed amount of time, this cannot be compensated by any actions of the upper layers.Therefore, a wide variety of mechanisms have been developed to implement these guarantees and to dealwith harmful physical channel properties like transmission errors.

In virtually all data communication networks used in industrial applications the transmission is packetbased; i.e., the user data are segmented into a number of distinct packets, and these packets are transmittedover the channel. Therefore, the following fundamental problems have to be solved:

What constitutes a frame and how are the bounds of a frame specified? How does the receiverdetect frames and the data contained? To this end, framing and synchronization schemes are needed,

When should a frame be transmitted? If multiple stations want to transmit their frames over acommon channel, appropriate rules are needed to share the channel and to let each stationdetermine when it may send its frames. This problem is tackled by medium access control (MAC)

How should channel errors be coped with? The topic of error control is briefly touched on in

How should the receiver be protected against too much data sent by the transmitter? This is the

Which packet should be transmitted next? This is the problem of packet scheduling, sketched in

Finally, in link layer protocols all these mechanisms are combined into a working protocol. We

The chapter is necessarily short on many topics. The interested reader will find further references inthe text.

1.2 Framing and Synchronization

The problem of synchronization is related to the transmission of information units (packets, frames)between a sending and a receiving entity. In computer systems, information is usually stored and pro-cessed in a binary digital form (bits). A packet is formed from a group of bits and shall be transmittedto the receiver. The receiver must be able to uniquely determine the start and end of a packet as well asthe bits within the packet.

The transmission of information over short distances, for instance, inside the computer, can be donewith parallel transmission. Here, a number (say 64) of parallel copper wires transport all bits of a 64-bitdata word at the same time. In most cases, one additional wire transmits the common reference clock.Whenever the transmitter has applied the correct voltage (representing a 0 or 1 bit) on all wires, it signalsthis by sending a sampling pulse on the clock wire toward the receiver. Conversely, on receiving a pulseon the clock wire, the receiver samples the voltage levels on all data wires and converts them back to bitsby comparing them with a threshold.

This kind of transmission is fast and simple, but cannot span large distances, because the cabling costbecomes prohibitive. Therefore, the data words have to be serialized and transmitted bit by bit on a single wire.

*We will use both terms interchangeably.The term wire is actually used here as a synonym for a transmission channel. It therefore could also be a wireless

or ISDN channel.

2005 by CRC Press

discussed in Section 1.2.

protocols, discussed in Section 1.3.

Section 1.4.

problem of flow control, discussed in Section 1.5.

Section 1.6.

discuss two important protocols in Section 1.7.

Principles of Lower-Layer Protocols for Data Communications 1-3

1.2.1 Bit Synchronization

The spacing of bits generated by the transmitter depends on its local clock. The receiver needs this clockinformation to sample the incoming signal at appropriate points in time. Unfortunately, the transmittersand receivers clocks are not synchronized, and the synchronization information has to be recoveredfrom the data signal; the receiver has to synchronize with the transmitter. This process is called bitsynchronization. The aim is to let the receiver sample the received signal in the middle of the bit periodin order to be robust against the impairments of the physical layer, like bandwidth limitation and signaldistortions. Bit synchronization is called asynchronous if the clocks are synchronized only for one dataword and have to be resynchronized for the next word. A common mechanism used for this employsone start bit preceding the data word and one or more stop bits concluding it. The Universal AsynchronousReceiver/Transmitter (UART) specification defines one additional parity bit, which is appended to the

For longer streams of information bits, the receiver clock must be synchronized continuously. Thedigital phase-locked loop (DPLL) is an electrical circuit that controls a local clock and adjusts it to thereceived clock being extracted from the incoming signal [23]. To recover the clock from the signal,sufficiently frequent changes of signal levels are needed. Otherwise, if the wire shows the same signallevel for a long time (as may happen for the non-return to zero (NRZ) coding method, where bits aredirectly mapped to voltage levels), the receiver clock could drift away from the transmitter clock. TheManchester encoding (shown in the second row of Figure 1.1) ensures that there is at least one signalchange per bit. Every logical 1 is represented by a signal change from one to zero, whereas a logical 0shows the opposite signal change. The internal clock of the DPLL samples the incoming signal with amuch higher frequency, for instance, 16 times per bit. For a logical 0 bit that is arriving exactly in time,the DPLL receives a sample pattern of 0000000011111111. If the transition between the 0 and 1 samplesis not exactly in the middle of the bit but rather left or right of it, the local clock has to be readjusted torun faster or slower, respectively. In the classical IEEE 802.3 Ethernet, the bits are Manchester encoded[2]. To allow the DPLL of the receiver to synchronize to the received bit stream, a 64-bit-long preambleis transmitted ahead of each frame. This preamble consists of alternating 0 and 1 bits that result in asquare wave of 5 MHz. A start-of-frame delimiter of two consecutive 1 bits marks the end of the preambleand the beginning of the data frame.

FIGURE 1.1 NRZ, Manchester, and differential Manchester codes.

1 0 1 1 0 0 1 0

Diff. Manchester

Manchester

NRZ

1 means no level change 0 means level change

2005 by CRC Press

8 data bits, leading to the transmission of 11 bits total for every 8 data bits [3]. The upper row in Figure1.2 illustrates this.


1.2.2 Frame Synchronization

It is of interest for the receiver to know whether the received information is (1) complete and (2) correct.

needs to know where a packet starts and ends. The question that arises immediately is that of markingthe start and end of a frame. There are several ways to accomplish this; in real-world protocols one oftenfinds combinations of them. In the following, the most important will be discussed briefly.

1.2.2.1 Time Gaps

The most straightforward way to distinguish between frames is to leave certain gaps of silence betweenthem. However, when many stations share the same medium, all of them have to obey these time gaps.

the medium is accessible.While time gaps are a simple way to detect the start of a frame, it should be possible to detect the end

of it, too. Using time gaps, the end of the previous packet can be detected only after a period of silence.Even if the receiver detects a silent medium, it cannot be sure if this is the result of a successful transmissionor a link or node failure. Therefore, additional mechanisms are needed.

1.2.2.2 Code Violations

A bit is usually encoded by a certain signal pattern (e.g., a change in voltage or current levels) thatis, of course, different for a 0 and 1 bit. A signal pattern that represents neither of the allowed valuescan be taken as a marker for the start of a frame. An example for this is the IEEE 802.5 Token Ring

symbols appear: J for a so-called positive code violation and K for a negative one. In contrast to thebit definitions in the encoding, these special symbols do not show a transition in the middle of thebit. Special 8-bit-long characters that mark the beginning and end of the frame are constructed fromthese symbols.

1.2.2.3 Start/End Flags

Some protocols use special flags to indicate the frame boundaries. A sequence of 01111110, that is, six1 bits in a sequence surrounded by two 0 bits, marks the beginning and the end of each frame. Of course,since the payload that is being transmitted can be an arbitrary sequence of bits, it is possible that theflag is contained in the payload. To avoid misinterpretation of a piece of payload data as being the endof a frame, the sender has to make sure that it only transmits the flag pattern if it is meant as a flag. Any

FIGURE 1.2 EN 50170 PROFIBUS: character and selected frame formats.

SD1 DA SA FC FCS ED

SD2 DA SA FC Data FCS ED

SD3 LE LEr SD3 SA DA FC Data FCS ED

SD1SD3 Start DelimiterDA, SA Destination, Source addressFC Frame Control byteFCS Frame Check Sequence (CRC)LE Length FieldLEr Length Field repeatedED End Delimiter

Start

Control frame (no data)

Fixed data length (8 characters)

UART character (11 bit)

Variable length data frame (0249 characters)

Start, Stop Start/Stop bit

StopParityD7 D6 D5 D4 D3 D2 D1 D0

D7D0 Data bits

2005 by CRC Press

protocol [28], which uses differential Manchester encoding (see Figure 1.1 and [28]). Here, two special

Section 1.4 treats the latter problem in some more detail. To decide about the first problem, the receiver

As it will be seen in Section 1.3.3.2, several MAC protocols rely on minimum time gaps to determine if


flag-like data have to be altered in a consistent way to allow the receiver to recover the original payload.This can be done using bit- or byte-/character-stuffing techniques.

Bit stuffing, as exercised in high-level data link control (HDLC) [23] protocols, requires the sender toinsert a zero bit after each sequence of five consecutive 1 bits. The receiver checks if the sixth bit thatfollows five 1s is a zero or one bit. If it detects a zero, it is removed from the sequence of bits. If it detectsa 1, it can be sure that this is a frame boundary. Unfortunately, it might happen that a transmission errormodifies the data sequence 01111100 into 01111110, and thus creates a flag prematurely. Therefore,additional mechanisms like time gaps are needed to remove the following bits and detect the actual endof the frame.

Byte stuffing, as employed in Point-to-Point Protocol (PPP), uses the same flag pattern, but relies ona byte-oriented transmission medium [5, 6]. The flag can be written as a hexadecimal value 07E. Everyunintentional appearance of the flag pattern is replaced by two characters, 07D 05E. This way, the flagcharacter disappears, but the 07D (also called escape character) has to be replaced, if it is found in theuser data. To this end, 07D is replaced by 07D 05D. The receiver, after detecting the escape characterin the byte stream, discards this byte and performs an exclusive-or (XOR) operation of 020 with thefollowing byte to recover the original payload.

In both cases, more data are being transmitted than would be necessary without bit- or byte-stuffingtechniques. To make things worse, the amount of overhead depends on the contents of the payload. Amalicious user might effectively double the data rate (with byte stuffing) or increase it by around 20%(with bit stuffing) by transmitting a continuous stream of flags. To avoid this, several measures can betaken. One is to scramble the user data before they are put into data frames [4].

Another possibility is the so-called consistent overhead byte stuffing (COBS), proposed in [1]. Here,the stream of data bytes is scanned in advance for appearing flags. The sequence of data bytes is thencut into chunks of at most 254 bytes not containing the flag. Thus, every flag that appears in the flow isreplaced by one byte representing the number of nonflag data bytes following it. This way, no additionaldata are to be transmitted as long as there is at least one flag every 255 data bytes. Otherwise, one byteis inserted every 254 bytes, indicating a full-length chunk.

1.2.2.4 Length Field

To avoid the processing overhead that comes with bit or character stuffing, it is possible to reserve afield in the frame header that indicates the length of the whole frame. Having read this field, the receiverknows in advance how many characters or bytes will arrive. No end delimiter is needed anymore. Eithera continuous transmission of packets followed by idle symbols, or the usual combination of preambleand start delimiter is needed to correctly determine which of the header fields carries the lengthinformation.

Being potentially the best solution concerning transmission overhead, the length field mechanismsuffers from erroneous transmission media. If the packet length information is lost or corrupted, thenit is difficult to find again. Therefore, it has to be protected separately using error-correcting codes orredundant transmission. Additional mechanisms (for example, time gaps) should be employed to findthe end of a frame even when the length field is erroneous.

1.2.3 Example: Bit and Frame Synchronization in the PROFIBUS

As an example to illustrate the mechanisms introduced above, let us look at the lower layers of the EN50170/DIN 19245 process fieldbus (PROFIBUS) [52]. This standard defines a fieldbus system for indus-trial applications. The lowest layer, the physical layer, is based on the RS-485 electrical interface. Shieldedtwisted-pair or fiber cable may be used as the transmission medium. The UART converts every byte into11-bit transmission characters by adding start, parity, and stop bits. Thus, asynchronous bit synchroni-zation is used on the lowest layer of the PROFIBUS.

2005 by CRC Press

The second layer is called the fieldbus data link (FDL). It defines the frame format, as shown in Figure1.2. Start and end delimiters are used in every frame, but different start delimiters SDx (SD1 to SD4; the


latter is not shown in the figure) define different frame types. Thus, a receiver knows after reading anSD1 that a control frame of fixed length will arrive. In addition, time gaps of 33 bit times are requiredbetween the frames. After receiving an SD3, the receiver interprets the next byte as LE (length field) andchecks this against the redundant transmission of LE in the third byte, thereby decreasing the probabilityof undetected errors in the length field. Using the combination of time gaps and the redundant trans-mission of the length field, a character stuffing to replace all possible start and end delimiters in thepayload becomes unnecessary.

1.3 Medium Access Control Protocols

All medium access control or multiple-access control (MAC) protocols try to solve the same problem: to leta number of stations share a common resource (namely, the transmission medium) in an efficient mannerand such that some desired performance objectives are met. They are a vital part of local area network(LAN) and metropolitan area network (MAN) technologies, which typically connect a small to moderatenumber of users in a small geographical area, such that a user can communicate with other users.

With respect to the Open Systems Interconnection (OSI) reference model, the MAC layer does notform a protocol layer on its own, but is considered a sublayer of either the physical layer or the data linklayer [45]. However, due to its distinguished task, the MAC sublayer deserves separate treatment. Theimportance of the MAC layer is reflected by the fact that many MAC protocol standards exist, for example,the IEEE 802.x standards. Its most fundamental task is to determine for each station attached to a commonbroadcast medium the points in time where it is allowed to access the medium, i.e., to send data orcontrol frames. To this end, each station executes a separate instance of a MAC protocol.

The design and behavior of a MAC protocol depend on the design goals and the properties of theunderlying physical medium. Specifically for hard real-time communications, the MAC layer is a keycomponent: if the delays on the MAC layer are not strictly bounded, the upper layers cannot compensatethis. A large number of MAC protocols have been developed during the last three decades. The followingreferences are landmark papers or survey articles covering the most important protocols: [7], [8], [17],[20], [21], [32], [33], [34], [36], [42], [43], [48], [49], [50], [54]. Furthermore, MAC protocols arecovered in many textbooks on computer networking, for example, [12], [23], [45]. In this survey, westick to those protocols that are important for industrial applications and that have found some deploy-ment in factory plants, either as stand-alone solutions or as building blocks of more complex protocols.

1.3.1 Requirements and Quality-of-Service Measures

There are a number of (sometimes conflicting) requirements for MAC protocols; some of them arespecific for industrial applications with hard real-time and reliability constraints.

There are two main delay-oriented measures: the medium access delay and the transmission delay. Themedium access delay is the time between arrival of a frame and the time where its transmission starts.This delay is affected by the operational overhead of the MAC itself, which may include collisions, MACcontrol frames, backoff and waiting times, and so on. The transmission delay denotes the time betweenframe arrival and its successful reception at the intended receiver. Clearly, the medium access delay is afraction of the transmission delay. For industrial applications with hard real-time requirements, bothdelays must be upper bounded. In addition, a desirable property is to have low medium access delays incase of low network loads.

A key requirement for industrial applications is the support for priorities: important frames (forexample, alarms, periodic process data) should be transmitted before unimportant ones. This require-ment can be posed locally or globally: in the local case, each station decides independently which of itswaiting frames is transmitted next. There is no guarantee that station As important frames are not blockedby station Bs unimportant frames. In the global case, the protocol identifies the most important frameof all stations to be transmitted next.

2005 by CRC Press


The need to share bandwidth between stations constitutes another important class of desired MACproperties. A frequently posed requirement is fairness: stations should get their fair share of the band-width, even if other stations demand much more. It is also often required that a station receives a minimumbandwidth, like for the transmission of periodic process data of fixed size.

With respect to throughput, it is clearly important to keep the MAC overhead small. This concerns theframe formats, the number and frequency of MAC control frames, and efficiency losses due to theoperation of the MAC protocol. An example for efficiency loss is collisions: the bandwidth spent forcollided packets is lost, since typically the collided frames are useless and must be retransmitted. A MACprotocol is said to be stable if an increase in the overall load does not lead to a decrease in throughput.

Depending on the application area, other constraints can be important as well. For simple field devices,the MAC implementation should have a low complexity and be simple enough to be implementable inhardware. For mobile stations using wireless media, the energy consumption is a major concern; therefore,power-saving mechanisms are needed. For wireless transmission media, the MAC should contain addi-tional mechanisms to adapt to the instantaneous error behavior of the wireless channel; possible controlknobs are the transmit power, error-correcting codes, the bit rate, and several more.

1.3.2 Design Factors

The most important factors influencing the design of MAC protocols are the medium properties/mediumtopology and the available feedback from the medium.

We can broadly distinguish between guided media and unguided media. In guided media the signalsoriginating from frame transmissions propagate within well-specified geographical bounds, typicallywithin copper or fiber cables. If the medium is properly shielded, then beyond these bounds the com-munications are invisible and two cables can be placed close to each other without mutual interference.In contrast, in unguided media (with radio frequency or infrared wireless media being the prime example)the wave propagation is visible in the whole geographical vicinity of the transmitter, and ongoingtransmissions can be received at any point close enough to the transmitter. Therefore, two differentnetworks overlayed within the same geographical region can influence each other. This coexistenceproblem appears, for example, with IEEE 802.11b [37] and Bluetooth [13, 22]. Both systems utilize the2.4-GHz industrial, scientific, and medical (ISM) band [16, 25, 35].

Guided media networks can have a number of topologies. We discuss a few examples. In a ring topology(see Figure 1.3), each station has a point-to-point link to its two neighbors, such that the stations forma ring. In a bus topology like the one shown in Figure 1.4, the stations are connected to a common bus

FIGURE 1.3 Ring topology.FIGURE 1.4 Bus topology (the black boxes are line ter-minations).

1 2

34

1

3

2

4

2005 by CRC Press


and all stations see the same signals. Hence, the bus is a broadcast medium. In the star topology illustratedin Figure 1.5, all stations only have a physical connection to a central device, the star coupler, whichrepeats and optionally amplifies the signals coming from one line to all the other lines. A network witha star topology also provides a broadcast medium, where each station can hear all transmissions. Whenusing wireless transmission media, the distance between stations might be too large to allow all stationsto receive all transmissions. Therefore, the network is often only partially connected or has a partial meshstructure, shown in Figure 1.6. Additional routing mechanisms have to be employed to implementmultihop transmission, for example, from station 4 to station 8.

An important property of a physical channel is the available feedback. Specifically, some kinds of mediaallow a station to read back data from the channel while transmitting. This can be done to detect faultytransceivers (like in the PROFIBUS protocol [52]), collisions (like in the Ethernet protocol), or parallelongoing transmissions of higher priority (like in the Controller Area Network (CAN) protocol). Thisfeature is typically not available when using wireless technologies: it is not possible to send and receivesimultaneously on the same channel.

1.3.3 Random Access Protocols

In random access (RA) protocols the stations are uncoordinated and the protocols work in a fullydistributed manner. RA protocols typically incorporate a random element, for example, by exploitingrandom packet arrival times, setting timers to random values, and so on. The lack of central coordinationand of fixed resource assignment allows the sharing of a channel between a potentially infinite numberof stations, whereas fixed assignment and polling protocols support only a finite number of stations.However, the randomness can make it impossible to give deterministic guarantees on medium accessdelays and transmission delays. There are many RA protocols that are used not only on their own, butalso as building blocks of more complex protocols. One example is the GSM system, where speech dataare transmitted in exclusively allocated time slots on a certain frequency, but the call setup messages haveto contend for a shared channel using an ALOHA-like protocol.

FIGURE 1.5 Star topology.

FIGURE 1.6 Partial mesh topology.

1 2

34

Star

4

1

3

2

5

7

6

8

2005 by CRC Press


1.3.3.1 ALOHA and Slotted ALOHA

A classical protocol is ALOHA [7], for which we present two variants here. In both variants a numberof stations want to transmit packets to a central station. In pure ALOHA a station sends a newly arrivingdata frame immediately without inquiring the status of the transmission medium. Hence, frames frommultiple stations can overlap at the central station (collision) and become unrecognizable. In slottedALOHA all stations are synchronized to a common time reference and the time is divided into fixed-sizetime slots. Newly arriving frames are transmitted at the beginning of the next time slot. In both ALOHAvariants the transmitter starts a timer after frame transmission. The receiver has to send an immediateacknowledgment frame upon successful reception of the data frame. When the transmitter receives theacknowledgment, it stops the timer and considers the frame successfully transmitted. If the timer expires,the transmitter selects a random backoff time and waits for this time before the frame is retransmitted.The backoff time is chosen randomly to avoid synchronization of colliding stations. This protocol hastwo advantages: it is extremely simple and it offers short delays in case of a low network load. However,the protocol does not support priorities, and with increasing network load, the collision rate increasesand the transmission delays grow as well. In addition, ALOHA is not stable: above a certain thresholdload an increase in the overall load leads to a decrease in overall throughput. The maximum normalizedthroughput of pure ALOHA is 1/2e 18% under Poisson arrivals and an infinite number of stations. Themaximum throughput can be doubled with slotted ALOHA. A critical parameter in ALOHA is the backofftime, which is typically chosen from a certain time interval (backoff window). A collision can be interpretedas a sign of congestion. If another collision occurs after the backoff time, the next backoff time shouldbe chosen from a larger backoff window to reduce the pressure on the channel. A popular rule for theevolution of the backoff window is the truncated binary exponential backoff scheme, where the backoffwindow size is doubled upon every collision. Above a certain number of failed trials, the window remainsconstant. After successful transmission the backoff window is restored to its original value.

1.3.3.2 CSMA Protocols

In carrier-sense multiple-access (CSMA) the stations act more careful than in ALOHA: before transmit-ting a frame they listen on the medium (carrier sensing) to see whether it is busy or free [32, 46]. If themedium is free (many protocols require it to be contiguously free for some minimum amount of time),the station transmits its frame. If the medium is busy, the station defers transmission. The various CSMAprotocols differ in the following steps.

In nonpersistent CSMA the station simply defers for a random time (backoff time) without listeningto the medium during this time. After this waiting time the station listens again. All other protocolsdiscussed next wait until the end of the ongoing transmission before starting further activities.

In p-persistent CSMA (0 < p < 1) the time after the preceding transmission ends is divided into timeslots. A station listens to the medium at the beginning of a slot. If the medium is free, the station startstransmitting its frame with a probability p and with probability 1 p it waits until the next slot comes.In 1-persistent CSMA the station transmits immediately without further actions. Both approaches stillhave the risk of collisions, since two or more stations can decide to transmit (1-persistent CSMA) or canchoose the same slot (p-persistent CSMA). The problem is the following: if station A senses the mediumas idle and starts transmission at time t0, station B would notice this earliest at some later time t0 + t,due to the propagation delay. If B performs carrier sensing at a time between t0 and t0 + t, it senses themedium to be idle and starts transmission too, resulting in a collision. Therefore, the collision probabilitydepends on the propagation delay, and thus on the maximum geographical distance between stations.Similar to ALOHA, pure CSMA protocols rely on acknowledgments to recognize collisions.

Although the throughput of CSMA-based protocols is much better than that of ALOHA (ongoingtransmissions can be completed without disturbance), the number of collisions and their duration limitthe throughput. Collision detection and collision avoidance techniques can be used to relax these prob-lems. These are discussed in the following sections.

Specifically for wireless media the task of carrier sensing is not without problems. After all, thetransmitter senses the medium ultimately because he wants to know the state of the medium at the

2005 by CRC Press


intended receiver, since collisions are only important at the receiver. However, due to path loss [40,

required, the hidden-terminal problem occurs (refer to Figure 1.7): consider three stations, A, B, and C,with transmission radii as indicated by the circles. Stations A and C are in range of B, but A is not inthe range of C and vice versa. If C starts to transmit to B, A cannot detect this by its carrier-sensingmechanism and considers the medium to be free. Hence, A also starts frame transmission and a collisionoccurs at B.

For wireless media there is a second scenario where carrier sensing leads to false predictions about thechannel state at the receiver: the so-called exposed-terminal scenario, depicted in Figure 1.8. The fourstations A, B, C, and D are placed such that the pairs A/B, B/C, and C/D can hear each other; all remainingcombinations cannot. Consider the situation where B transmits to A, and one short moment later Cwants to transmit to D. Station C performs carrier sensing and senses the medium is busy, due to Bstransmission. As a result, C postpones its transmission. However, C could safely transmit its frame to Dwithout disturbing Bs transmission to A. This leads to a loss of efficiency.

Two approaches to solve these problems are busy-tone solutions [50] and the request-to-send (RTS)/clear-to-send (CTS) protocol, as applied in the IEEE 802.11 wireless LAN (WLAN) medium access controlprotocol [47]. In the busy-tone approach the receiver transmits a busy-tone signal on a second channelduring frame reception. Carrier sensing is performed on this second channel. This solves the exposed-terminal problem. The hidden-terminal scenario is also solved, except the rare cases where A and C starttheir transmissions simultaneously.

The RTS/CTS protocol attacks the hidden-terminal problem using only a single channel. Consider thecase that A has a data frame for B. After A has obtained channel access, it sends a short RTS frame to B,indicating the time duration needed for the whole frame exchange sequence (the sequence consists ofthe RTS frame, the CTS frame, a data frame, and a final acknowledgment frame). If B receives the RTSframe properly, it answers with a CTS frame, indicating the time needed for the remaining frame exchangesequence. Station A starts transmission after receiving the CTS frame. Station C, hearing the RTS andCTS frames, defers its transmissions for the indicated time, thus not disturbing the ongoing frameexchange. It is a conservative choice to defer on any of these frames, but the exposed-terminal problemstill exists. If station C defers only on receiving both frames, the exposed-terminal problem is solved.However, there is the risk of bit errors in the CTS frame, which may lead C to start transmissions falsely.The RTS/CTS protocol of IEEE 802.11 does not resolve collisions of RTS frames at the receiver, nor does

FIGURE 1.7 Hidden-terminal scenario.

FIGURE 1.8 Exposed-terminal scenario.

A B C

A B DC

2005 by CRC Press

Chapter 4], any signal experiences attenuation with increasing distance. If a minimum signal strength is


it entirely solve the hidden-terminal problem [39]. Furthermore, this four-way handshake imposes seriousoverhead, which only pays out for large frames.

1.3.3.3 CSMA Protocols with Collision Detection

If two or more stations collide without recognizing this, they would uselessly transmit their entire frames.If the stations could quickly detect a collision and abort transmission, less bandwidth is wasted. The classof carrier-sense multiple access with collision detection (CSMA/CD) protocols enhances the basic CSMAmethod with a collision detection facility. The collision detection is performed by reading back the signalfrom the cable during transmission, and by comparing the measured signal with the transmitted one. If

When a station experiences a collision, it executes a backoff algorithm. In the IEEE 802.3 Ethernet thisalgorithm works with slotted time. A time slot is large enough to accommodate the maximum round-trip time, in order to make sure that all stations have the chance to reliably recognize an ongoingtransmission. As an example, in the CSMA/CD method of IEEE 802.3 a truncated binary exponentialbackoff scheme is used: after the first collision, a station randomly chooses to wait either 0 or 1 slot. Ifanother station starts transmission during the waiting time, the station defers. After the second collision,a station chooses to wait between 0 and 3 slots, and for all subsequent collisions, the backoff window isdoubled. After 10 collisions the backoff window is kept fixed to 1024 slots, and after 16 collisions thestation gives up and discards the frame.

In wireless LANs (for example, in the IEEE 802.11 wireless LAN) acknowledgment frames are usedto give the transmitter feedback, since wireless transceivers cannot transmit and receive simultaneouslyon the same channel. The lack of an acknowledgment frame indicates either a collision or a transmissionerror. Furthermore, two colliding frames do not necessarily result in total loss of information: when thesignal strength of one frame is much stronger than the other one, the receiver may be able to successfullydecode the frame (nearfar effect).

1.3.3.4 CSMA Protocols with Collision Resolution

This class of CSMA protocols reacts to collisions not by going into a backoff mode and deferringtransmissions, but by trying to resolve them. One approach to resolving a collision is to determine onestation among the contenders, which is ultimately allowed to send its frame. One example for this isprotocols with bit-wise priority arbitration like the MAC protocol of Controller Area Network (CAN)[30] and the protocol used for the D-channel of Integrated Services Digital Network (ISDN) [41]. Anotherapproach is to give all contenders a chance to transmit, like what is done in the adaptive tree walkingprotocol [14], which works as follows: The time is slotted, just as in the Ethernet CSMA/CD protocol.Furthermore, all stations are arranged in a balanced binary tree T and know their respective positionsin this tree. All stations wishing to transmit a frame (called backlogged stations) wait until the end ofthe ongoing transmission and start to transmit their frame in the first slot (slot 0). If there is only onebacklogged station, then it could transmit its frame without further disturbance. If two or more stationscollide, then in slot 1 only the members of the left subtree TL are allowed to try transmission again. Ifanother collision happens, only stations of the left subtree TL,L of TL are allowed to transmit in slot 2,and so forth. On the other hand, if only one

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