BILHANAN SILVERAJAN Communication Protocol and Management Considerations for Internet of Things Gateways Tampere University Dissertations 426 7CTWGXG8UQbGXYQ`d"QYYGX`C`QVUY '0&226'09#5(2 !aE4ESF 1I!F HHPI%c !1!3 DF/cPPH P$EaSHHEPSIF!aEEGUE H/ HaDSEFEaPaFa 13 HS/)RRaSaRa1// a31/1iESER: !1!3 /$EaSHHEPSIF!aEEEY $SF 4H)e 7CTWGXG8UQbGXYQ`d $SF 4H@P 4H4 EbGH@SSI 0878UQbGXYQ`d cBSF $SF 4HaR HSR $SF PISHPPPDUEPERFaIPa3IS!PER YGXbQE: !IPf31aP !FGYQIPaE: FF3F13FMO FF3F11FMFHO F3MO 3F33MFHO PPPa:HPFF3F11F 4a1a3hAS (VGUaa31 Abstract Today, it is inconceivable to think about modern life without the Internet. The Internet has transformed our lives, serving as a digital backbonefor communication, media and Web-based interaction among human users. It has, however, begun to evolve into the Internet of Things (IoT), interconnecting constrained devices such as sensors, actuators and miniaturised computing platforms. Aided in large part by advances in decreasing hardware costs, better battery, radio and computational technology, these kinds of connected IoT devices have rapidly begun to proliferate. The resulting traffic generated and exchanged by IoT devices is expected to dwarf that produced by humans. However IoT devices exhibit significant differences in terms of computational and storage capacities, wireless radio networks and communication protocols. Integrating them into the Internet is not straightforward, in terms of device addressing, reachability as well as data representation and transfer. In many IoT domains, there are already deployed networks, devices and sensors based on legacy technology, that the IoT is compelled to integrate. All this has led to the emergence of IoT gateways in playing a central role for integration and interoperability, in ensuring interconnection and end-to-end communication with different kinds of IoT devices and networks. IoT gateways themselves can be multi-functional; their complexity and usage depends on exactly what kinds of IoT devices and networks they need to integrate into the Internet, and what additional services are expected of them in ensuring successful interaction with edge devices. This dissertation focuses on these roles IoT gateways fulfill, enabling them to function as essential components of the IoT. The main research question of this dissertation is: “For various kinds of IoT network topologies, how can gateways be configured and managed, to support connectivity and communication with IoT end devices?” To answer this question, four research areas for IoT gateways were studied, by applying Design Science Research Methodology (DSRM): Network Connectivity, Energy Consumption, Protocol Composition, and Gateway Man- agement. For network connectivity, the communication and reachability requirements exerted on IoT gateways by IoT devices and various IoT edge network topologies were studied. For energy consumption, the utilisation of gateway energy consumption patterns were investigated, in order to optimise communication as well as monitor operational performance. For protocol composition, the specification, implementation and deployment of protocols, gateway protocol stacks and network services was researched. Lastly, for gateway management, the research into redundancy management as well as development of IoT management practices for operational management and configuration, was performed. The results and contributions of this dissertation are categorised into three abstraction levels of an IoT gateway. These are at the network, management and communication levels i ii Abstract of abstractions respectively. At the network abstraction, the work is oriented towards IPv6- based networks. The results describe the various IoT topologies, and gateway configuration and design to aid with IPv6 address allocation and network connectivity for edge devices. At the management abstraction, the dissertation identifies patterns in IoT gateway management and contributes object models and communication techniques for gateway configuration, operational monitoring, redundancy management and device proxying. At the communication abstraction, the dissertation contributes an implementation framework and a specification language allowing rapid development of communication protocols. The results also describe how energy consumption in IoT gateways can be employed both to optimise data transmissions as well as detect network-based attacks. Both proofs of concept as well as conducted field experiments were used to verify the results of the dissertation. Empirical findings and obtained results have also been adopted both for Internet and IoT device management standardisation. Preface "My big fish must be somewhere." -Santiago, Ernest Hemingway’s The Old Man and the Sea My doctoral dissertation was in gestation for a significant amount of time. This was my big fish. I have had the distinct privilege of meeting, interacting and working with some immensely talented people throughout this process. I wish to firstly acknowledge Tampere University for providing me the opportunities to pursue my doctoral research, and the conducive environments in which to undertake it. Prof Jarmo Harju was responsible for setting me on this journey and served as my mentor and supervisor until his retirement. Prof Kari Systä then took an active role towards my dissertation as my supervisor. I am grateful to them both for their guidance, reviews and frank discussions which became instrumental in shaping and completing my dissertation. I wish to thank Prof Jari Porras and Prof Winston Seah, for serving as pre-examiners. Their very thorough reviews helped significantly improve my final manuscript. I also wish to thank Prof Sasu Tarkoma for graciously agreeing to be my dissertation opponent. My gratitude goes to Ms Elina Orava from the Faculty of Information Technology and Communication Sciences and Ms Sonja Mattsson from the Library Open Science Services for their advice and assistance in the publication of my dissertation. I have selected nine peer-reviewed publications for inclusion into my dissertation, and my deepest thanks go to my co-authors in all these papers: Karri Huhtanen, Riku Itäpuro, Nadir Javed, Jaime Jiménez, Antti Kolehmainen, Juha-Pekka Luoma, Andrea Mola, Maurizio Magarini, Mert Ocak, Teemu Savolainen, Davide Scazzoli, Jonne Soininen, Markku Vajaranta and Giacomo Verticale. I have been, and continue to be, greatly enriched by my involvement with the IETF community, particularly the members of the CoRE Working Group, as well as with members of the OMA, and Smart Object Committee of the IPSO Alliance (which is now part of OMA SpecWorks). No words can convey the depth of gratitude I feel towards my family members for their trust, support and encouragement. Your sacrifices meant I never gave up. Finally I wish to acknowledge the many persons without whom my dissertation would not have come to fruition. I cannot name each and every single one of you, for you are too many. Thank you all for giving me your shoulders to lean on when I needed your aid, and to stand upon when I needed to reach higher. iii Contents Abstract i Preface iii Acronyms vii List of Figures x List of Tables xi List of Publications xiii Author’s Contribution to the Publications xv 1 Introduction 1 1.1 Gateways in the IoT .............................. 2 1.2 Research Questions ............................... 3 1.3 Scope and Contributions ............................ 5 1.4 Research Methodology ............................. 7 1.5 Thesis Structure ................................ 9 2 Background and Related Work 11 2.1 Connectivity and Reachability ......................... 11 2.2 REST and IoT ................................. 14 2.3EnergyMeasurements............................. 15 2.4 Composing Protocols and Protocol stacks . ................. 16 2.5 Management of IoT nodes ........................... 18 2.6 Summary .................................... 20 3 Connectivity and Reachability Considerations 23 3.1 Gateways allocating native IPv6 addresses in edge networks ........ 23 3.2 Gateway address allocation via IPv6 transition technologies . ..... 25 3.3 Data Reachability ............................... 27 3.4 Summary .................................... 28 4 Energy awareness in gateway communication 31 4.1 Undertaken Measurement Methods . .................... 31 4.2 Optimising cellular REST communication .................. 32 4.3 Anomalous Gateway Behaviour ........................ 34 4.4 Summary .................................... 35 v vi Contents 5 Composing Communication Protocols 37 5.1 Addressing IoT Gateway Hardware and Platform Heterogeneity ...... 38 5.2 Measuring network event handlers ...................... 39 5.3 Protocol Specification and Code Synthesis .................. 41 5.4 Monitoring runtime events and protocol parameters ............ 45 5.5 Summary .................................... 48 6 Gateway Management 51 6.1 Managing IoT endpoints ............................ 51 6.2 IoT Gateway Management Patterns ..................... 52 6.3 Operational considerations ........................... 57 6.4 Summary .................................... 61 7 Conclusion 63 7.1 Results ...................................... 63 7.2 Summary of Contributions ........................... 65 7.3 Discussion and Future Directions ....................... 65 Bibliography 71 Publications 79 Acronyms 3GPP Third Generation Partnership Project 6LowPAN IPv6 over Low-Power Wireless Personal Area Network 6lbr 6LowPAN Border Router ABNF Augmented