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Embedded, Everywhere: A Research Agenda for Networked Systems of Embedded Computers Embedded, Everywhere A Research Agenda for Networked Systems of Embedded Computers Committee on Networked Systems of Embedded Computers Computer Science and Telecommunications Board Division on Engineering and Physical Sciences National Research Council NATIONAL ACADEMY PRESS Washington, D.C.
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Embedded, Everywhere: A Research Agenda for Networked Systems of Embedded Computers NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance. Support for this project was provided by the Defense Advanced Research Projects Agency and the National Institute of Standards and Technology. Any opinions, findings, conclusions, or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the sponsor. Moreover, the views, opinions, and findings contained in this report should not be construed as an official Department of Defense position, policy, or decision, unless so designated by other official documentation. Library of Congress Control Number: 2001093511 International Standard Book Number 0-309-07568-8 Additional copies of this report are available from: National Academy Press 2101 Constitution Avenue, N.W. Box 285 Washington, DC 20055 800/624-6242 202/334-3313 (in the Washington metropolitan area) http://www.nap.edu Copyright 2001 by the National Academy of Sciences. All rights reserved. Printed in the United States of America
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Embedded, Everywhere: A Research Agenda for Networked Systems of Embedded Computers THE NATIONAL ACADEMIES National Academy of Sciences National Academy of Engineering Institute of Medicine National Research Council The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Bruce M. Alberts is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. Wm. A. Wulf is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, upon its own initiative, to identify issues of medical care, research, and education. Dr. Kenneth I. Shine is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy’s purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Bruce M. Alberts and Dr. Wm. A. Wulf are chairman and vice chairman, respectively, of the National Research Council.
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Embedded, Everywhere: A Research Agenda for Networked Systems of Embedded Computers COMMITTEE ON NETWORKED SYSTEMS OF EMBEDDED COMPUTERS DEBORAH L. ESTRIN, University of California at Los Angeles, Chair GAETANO BORRIELLO, University of Washington ROBERT PAUL COLWELL, Intel Corporation JERRY FIDDLER, Wind River Systems, Inc. MARK HOROWITZ, Stanford University WILLIAM J. KAISER, Sensoria Corporation NANCY G. LEVESON, Massachusetts Institute of Technology BARBARA H. LISKOV, Massachusetts Institute of Technology PETER LUCAS, Maya Design Group DAVID P. MAHER, InterTrust Technologies Corporation PAUL M. MANKIEWICH, Lucent Technologies RICHARD TAYLOR, Hewlett-Packard Laboratories JIM WALDO, Sun Microsystems, Inc. Staff LYNETTE I. MILLETT, Program Officer (Study Director beginning September 2000) JERRY R. SHEEHAN, Senior Program Officer (Study Director through August 2000) SUZANNE OSSA, Senior Project Assistant
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Embedded, Everywhere: A Research Agenda for Networked Systems of Embedded Computers COMPUTER SCIENCE AND TELECOMMUNICATIONS BOARD DAVID D. CLARK, Massachusetts Institute of Technology, Chair DAVID BORTH, Motorola Labs JAMES CHIDDIX, AOL Time Warner JOHN M. CIOFFI, Stanford University ELAINE COHEN, University of Utah W. BRUCE CROFT, University of Massachusetts at Amherst SUSAN L. GRAHAM, University of California at Berkeley JUDITH HEMPEL, University of California at San Francisco JEFFREY M. JAFFE, Bell Laboratories, Lucent Technologies ANNA KARLIN, University of Washington MICHAEL KATZ, University of California at Berkeley BUTLER W. LAMPSON, Microsoft Corporation EDWARD D. LAZOWSKA, University of Washington DAVID LIDDLE, U.S. Venture Partners TOM M. MITCHELL, WhizBang! Labs, Inc. DONALD NORMAN, UNext.com DAVID A. PATTERSON, University of California at Berkeley HENRY (HANK) PERRITT, Chicago-Kent College of Law BURTON SMITH, Cray, Inc. TERRY SMITH, University of California at Santa Barbara LEE SPROULL, New York University MARJORY S. BLUMENTHAL, Executive Director HERBERT S. LIN, Senior Scientist ALAN S. INOUYE, Senior Program Officer JON EISENBERG, Senior Program Officer LYNETTE I. MILLETT, Program Officer CYNTHIA PATTERSON, Program Officer JANET BRISCOE, Administrative Officer MARGARET HUYNH, Senior Project Assistant SUZANNE OSSA, Senior Project Assistant DAVID DRAKE, Project Assistant DAVID PADGHAM, Research Assistant BRANDYE WILLIAMS, Office Assistant
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Embedded, Everywhere: A Research Agenda for Networked Systems of Embedded Computers Preface Continued advances in information technologies are enabling a growing number of physical devices to be imbued with computing and communications capabilities. Aircraft, cars, household appliances, cellular telephones, and health monitoring devices all contain microprocessors that are being linked with other information processing devices. Such examples represent only the very beginning of what is possible. As microprocessors continue to shrink, wireless radios are also becoming more powerful and compact. As the cost of these and related technologies continues to decrease, computing and communications technologies will be embedded into everyday objects of all kinds to allow objects to sense and react to their changing environments. Networks comprising thousands or millions of sensors could monitor the environment, the battlefield, or the factory floor; smart spaces containing hundreds of smart surfaces and intelligent appliances could provide access to computational resources. Getting to this point will not be easy. Networks of embedded computers pose a host of challenges qualitatively different from those faced by more traditional computers or stand-alone embedded computers because they will be more tightly integrated with their physical environments, more autonomous, and more constrained in terms of space, power, and other resources. They will also need to operate, communicate, and adapt in real time, often unattended. Enabling such innovation will require that a number of research challenges be overcome. How can large numbers of embedded computing devices assemble themselves seam-
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Embedded, Everywhere: A Research Agenda for Networked Systems of Embedded Computers lessly into an integrated network? How can their performance be guaranteed? How can social issues raised by the advent of more pervasive information collection and processing—for example, concerns about privacy, robustness, and usability—be addressed? CHARGE TO THE COMMITTEE To improve understanding of these issues and help guide future research endeavors, the Defense Advanced Research Projects Agency (DARPA) and the National Institute of Standards and Technology (NIST) asked the Computer Science and Telecommunications Board (CSTB) of the National Research Council (NRC) to conduct a study of networked systems of embedded computers (EmNets) that would examine the kinds of systems that might be developed and deployed in the future and identify areas in need of greater investigation. This report identifies opportunities for the use of EmNets, examines the ways EmNets differ from more traditional systems, and delineates the research topics that need to be addressed. The objective is to develop a research agenda that could guide federal programs related to computing research and inform the research community (in industry, universities, and government) about the challenging needs of this emerging research area. This report examines both issues related to components of embedded computers—such as hardware needs, operating systems, programming capabilities, and human interfaces—and systems-level issues resulting from the interconnection of multiple embedded computers—system architectures, coordination, adaptation, reliability, security, safety, interoperability, stability, and guaranteed performance. To that end, the committee attempted to answer questions such as the following: What are networked systems of embedded computing systems? How do networks of embedded computers differ from more traditional computer networks? How do these differences affect research needs? What types of applications could arise from greater networking of embedded systems? What are the general characteristics of different applications? What would be the benefits and capabilities of such systems? How can systems of interconnected embedded processors be more easily designed, developed, and maintained? How can system reliability, safety, operability, and maintainability be ensured in networked systems? How do such considerations differ for embedded and more traditional forms of computing? What kinds of advances are needed in enabling component technologies, such as hardware devices, operating systems, and communications networks, to make EmNets possible and more capable?
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Embedded, Everywhere: A Research Agenda for Networked Systems of Embedded Computers What types of user interfaces are needed to allow users to interact with and to program systems composed of large numbers of interconnected embedded systems? How do these requirements differ for different kinds of users (experts, novices, system integrators)? What types of “programming” will consumers be expected to perform? How can the stability and effectiveness of interconnected systems of embedded computers be assured if individual components come from a wide variety of developers and use a variety of hardware and software platforms, some of which may run the latest versions of the software, and others of which may be several generations behind? COMMITTEE COMPOSITION AND PROCESS To conduct the study, CSTB assembled a committee of 15 members from industry and academia with expertise in areas of apparent importance to EmNets, such as computing devices, very-large-scale integrated circuit technology, networking, wireless communications, embedded operating systems, software safety, distributed computing, programming languages, human-computer interfaces and usability, and computer system security.1 Several committee members brought with them a familiarity with federal research programs related to EmNet technologies and provided invaluable insight into the challenges of organizing research programs in this area. Several committee members changed their organizational affiliation during the course of the study, attesting to the dynamic nature of this field. Indeed, because of growing commercial interest in ubiquitous or pervasive computing technology, two of the original committee members, Walter Davis from Motorola and Ajei Gopal from IBM, were unable to continue their participation in the project. The committee met six times between December 1999 and March 2001 to plan its course of action, solicit testimony from relevant experts, deliberate its findings, and draft its final report. It continued its work by electronic communications into the spring of 2001. During the course of the project, the committee heard from information technology researchers in industry and universities and from directors of government agencies involved in funding computing research (including research related to EmNets).2 It also met with people involved in developing and deploying EmNets to serve a range of missions, from controlling lighting and heating systems in office buildings and automating manufacturing lines, to 1 See Appendix A for biographies of committee members. 2 See Appendix B for a list of briefers to the committee.
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Embedded, Everywhere: A Research Agenda for Networked Systems of Embedded Computers monitoring the health of astronauts in space and of patients in emergency rooms. The committee also gathered information on major initiatives to pursue research on ubiquitous and pervasive computing, and it collected data on microprocessors, microcontrollers, wireless communications nodes, and their applications in order to track the emergence of an EmNet environment. ACKNOWLEDGMENTS As with any project of this magnitude, thanks are due to the many individuals who contributed to the work of the committee. First, thanks are due to the members of the committee itself, who volunteered considerable time during the course of the study to attend meetings, engage in e-mail and telephone discussions, draft sections of the report, and respond to comments from external reviewers. Beyond the committee, numerous persons provided valuable information through briefings to committee meetings: Andrew Berlin, Xerox Palo Alto Research Center; Stephen P. Boyd, Stanford University; Janusz Bryzek, Maxim Integrated Products, Inc.; David D. Clark, Massachusetts Institute of Technology; Alan Davidson, Center for Democracy and Technology; Robert Dolin, Echelon Corporation; John Hines, National Aeronautics and Space Administration; Rodger Lea, Sony Distributed Systems Laboratory; K. Venkatesh Prasad, Ford Research Laboratory; Jonathan Smith, University of Pennsylvania; Karen Sollins, National Science Foundation; and Keith Uncapher, Corporation for National Research Initiatives. Thanks are also due to those who sponsored the study. David Tennenhouse, formerly the director of the Defense Advanced Research Project Agency’s (DARPA) Information Technology Office (ITO) and now vice president of research at Intel Corporation, provided the original impetus for the study, identifying networked systems of embedded computers as a potentially revolutionary set of technologies and laying out a vision for the field. Shankar Sastry and Janos Sztipanovits ensured continued DARPA support for the project as they expanded ITO’s research efforts in EmNets of different kinds. Sri Kumar, also of DARPA’s ITO, provided considerable guidance and input related to sensor networks. Jerry Linn, formerly of the Information Technology Lab at NIST, generated interest and financial support from several laboratories within NIST. Other members of the Technology Policy Working Group also supported the concept of the study, even if they did not provide financial support. Many others also provided valuable input or services to the committee that should not go unnoted. Martin Herman and Alden Dima of NIST provided relevant information about NIST programs near the end of the
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Embedded, Everywhere: A Research Agenda for Networked Systems of Embedded Computers study process. As she has done so many times in the past, Laura Ost, a free-lance editor, provided invaluable assistance in preparing the manuscript for review. Jim Igoe, with the National Academies library, was helpful with background research. Craig Kaplan of the University of Washington assisted with cover design. Jeffrey Risberg of TIBCO Software, Inc.; Maja Mataric of the University of Southern California; Gaurav Sukhatme of the University of Southern California; Scott Stadler of the Massachusetts Institute of Technology’s Lincoln Laboratory; Gregory J. Pottie of the University of California at Los Angeles; and Steven T. Sonka of the University of Illinois at Urbana-Champaign also provided background information to the committee. Finally, the committee would like to acknowledge the work of the NRC staff. During the first 12 months of our study, Jerry Sheehan shaped the content and process of the report. He contributed vision, guidance, feedback, and discipline. Moreover, he continued to act as a key consultant after his official departure. We were all quite anxious about Jerry’s departure midway through our process; frankly, I was not sure we could carry it off without him. However, we were tremendously pleased to find that his replacement, Lynette Millett, was able to come in and march us to completion without missing a beat. She ferreted out our inconsistencies, turned our bullets into prose, implemented innumerable reorganizations and rewrites, and last but not least, came up with the title for the report! Lynette’s contributions are certainly embedded everywhere in this report. Alan Inouye worked with Lynette behind the scenes during the final phases of the project, providing advice and feedback and helping shepherd the project to completion. Liz Fikre made significant editorial contributions to the final manuscript. Claudette Baylor-Fleming, Carmela Chamberlain, and David Padgham assisted with final report preparation. Suzanne Ossa provided the committee with excellent support during meetings and assisted with background research and editorial work. Finally, we thank Marjory Blumenthal, whose vision and commitment directly and indirectly shaped the report through her hiring and mentoring of excellent staff and her detailed comments on many versions of the report. Deborah L. Estrin, Chair Committee on Networked Systems of Embedded Computers
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Embedded, Everywhere: A Research Agenda for Networked Systems of Embedded Computers Acknowledgment of Reviewers This report has been reviewed in draft form by individuals chosen for their diverse perspectives and technical expertise, in accordance with procedures approved by the NRC’s Report Review Committee. The purpose of this independent review is to provide candid and critical comments that will assist the institution in making its published report as sound as possible and to ensure that the report meets institutional standards for objectivity, evidence, and responsiveness to the study charge. The review comments and draft manuscript remain confidential to protect the integrity of the deliberative process. We wish to thank the following individuals for their review of this report: Michael DeWalt, Certification Services, Batya Friedman, University of Washington, Matthew S. Jaffe, Emory Riddle Aeronautical University, Randy H. Katz, University of California at Berkeley, Alan Kay, Walt Disney Imagineering, Edward A. Lee, University of California at Berkeley, John McHugh, CERT, Software Engineering Institute, Carnegie Mellon University, Kristofer S.J. Pister, University of California at Berkeley, Rush D. Robinett, Sandia National Laboratories, Daniel P. Siewiorek, Carnegie Mellon University, and Andrew J. Viterbi, Viterbi Group, LLC.
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Embedded, Everywhere: A Research Agenda for Networked Systems of Embedded Computers Although the reviewers listed above have provided many constructive comments and suggestions, they were not asked to endorse the conclusions or recommendations, nor did they see the final draft of the report before its release. The review of this report was overseen by Robert J. Spinrad, Xerox PARC (retired), appointed by the Division on Engineering and Physical Sciences, who was responsible for making certain that an independent examination of this report was carried out in accordance with institutional procedures and that all review comments were carefully considered. Responsibility for the final content of this report rests entirely with the authoring committee and the institution.
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Embedded, Everywhere: A Research Agenda for Networked Systems of Embedded Computers Contents EXECUTIVE SUMMARY 1 1 INTRODUCTION AND OVERVIEW 14 Examples, 16 Example 1: Automotive Telematics, 17 Example 2: Precision Agriculture, 20 Example 3: Defense Systems, 21 Understanding Networked Systems of Embedded Computers, 24 How EmNets Differ from Traditional Systems, 26 EmNets Are Tightly Coupled to the Physical World, 27 EmNet Nodes Are Often Resource-Constrained, 28 EmNets’ Long Lifetimes, 29 EmNet Size and Scale Are Significant, 30 EmNet Users Are Not System Experts, 31 Why a New Research Agenda?, 31 What This Report Does Not Do, 33 Advanced Sensors and Actuators, 34 Public Policy Issues, 34 Commercialization Issues, Standards, Business Models, 35 Stand-alone Embedded Systems and Other Networked Information Systems, 36 Organization of This Report, 37 References, 38
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Embedded, Everywhere: A Research Agenda for Networked Systems of Embedded Computers 2 ENABLING TECHNOLOGIES 39 Silicon Scaling, 40 Computing, 41 Growing Complexity, 42 Simpler Processors, 43 Power Dissipation, 45 Communication, 49 Wireline Communications, 50 Wireless Communications, 53 Geolocation, 57 Computing Software—Operating Systems and Applications, 59 Real-time and Performance-critical Aspects of Embedded Operating Systems, 64 Microelectromechanical Systems, 65 Summary, 68 References, 73 Bibliography, 74 3 SELF-CONFIGURATION AND ADAPTIVE COORDINATION 76 Terminology, 77 Self-configuration and Adaptive Coordination in Distributed Systems, 79 Discovery in Distributed Systems, 80 Interfaces and Interoperability, 84 Adaptive Coordination in Existing Networks, 90 Research Challenges for Configuration and Adaptive Coordination, 93 Research Issues in Self-configuration, 93 Research Issues for Adaptive Coordination, 101 Summary, 117 References, 118 4 BUILDING TRUSTWORTHY NETWORKED SYSTEMS OF EMBEDDED COMPUTERS 119 Reliability, 121 Reliability Research Topics Deserving Attention, 123 Safety, 123 Safety Research Topics Deserving Attention, 126 Security, 128 Protecting System Boundaries, 129 Managing Scale and Complexity, 130 Mobile Code and Security, 131
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Embedded, Everywhere: A Research Agenda for Networked Systems of Embedded Computers Denial of Service, 132 Security Research Topics Deserving Attention, 133 Privacy, 134 Privacy As Related to Security, 137 Privacy Research Topics Deserving Attention, 138 Usability, 140 Creating Mental Models, 141 EmNet-Specific Usability Issues, 143 Usability Research Topics Deserving Attention, 144 References, 145 Bibliography, 146 5 MODELS OF COMPUTATION 147 What Are Models of Computation?, 149 Distributed Computing Models: Current Practice, 152 New Models for Networked Systems of Embedded Computers, 156 Models with Resource Constraints, 158 Models Dealing with Failures, 160 New Data Models, 162 Models of Trust, 165 Models for Concurrency, 165 Models of Location, 167 Conducting Research on Models and Abstractions, 168 References, 171 6 CONCLUSIONS AND RECOMMENDATIONS: AN AGENDA FOR RESEARCH 172 An EmNet-specific Research Agenda, 174 Predictability and Manageability, 175 Adaptive Self-configuration, 176 Monitoring and System Health, 177 Computational Models, 178 Network Geometry, 179 Interoperability, 180 Integration of Technical, Social, Ethical, and Public Policy Issues, 181 Enabling Technologies, 183 Structuring the Research Enterprise for EmNets, 184 Stimulating Interdisciplinary Research, 185 What Can Government Do? Recommendations to Federal Agencies, 189
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Embedded, Everywhere: A Research Agenda for Networked Systems of Embedded Computers Recommendations to the Defense Advanced Research Projects Agency, 190 Recommendations to the National Institute of Standards and Technology, 197 Recommendations to the National Science Foundation, 199 Recommendations to Other Federal Agencies, 201 Summary, 202 References, 202 APPENDIXES 205 A Biographies of Committee Members 207 B Briefers at Plenary Meetings 214
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Embedded, Everywhere: A Research Agenda for Networked Systems of Embedded Computers Embedded, Everywhere A Research Agenda for Networked Systems of Embedded Computers
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