Abstract-This paper capitalizes on two emerging trends, i.e. the growing use of wireless at the edge of industrial control networks and the growing interest to integrate IP into said networks. This is facilitated by recent design contributions from the IEEE and the IETF, where the former developed a highly efficient deterministic time-frequency scheduled medium access control protocol in form of IEEE 802.15.4e TSCH and the latter IPv6 networking paradigms in form of 6LoWPAN/ROLL, and scheduling approaches in form of 6TiSCH. The focus of the present work is on advancing the state of the art of deterministic 6TiSCH schedules towards more flexible but equally reliable distributed approaches. In addition, this paper aims to introduce the first implementation of 6TiSCH networks for factory automation environments: it outlines the challenges faced to overcome the scalability issues inherent to multi-hop dense low-power networks; the experimental results confirm that the naturally unreliable radio medium can support time-critical and reliable applications. These developments pave the way for wireless industry-grade monitoring approaches.

The Time Slotted Channel Hopping (TSCH) Medium Access Control (MAC) has been introduced in the recent IEEE 802.15.4e amendment to improve energy efficiency and reliability of short range wireless communications in industrial applications. However the joining phase can take very long time due to the operation of TSCH and beside being a problem in the deployment phase it may become a relevant source of energy consumption. To overcome this issue the present contribution investigates the problem of acquiring the first synchronization in a TSCH network from several points of view: (i) two novel mechanisms are proposed and implemented in real motes to speed up joining operations; (ii) for each of them, the average joining time is analytically modeled with closed form expressions as a function of node density, communication reliability, and beacon transmission frequency; (iii) the effectiveness of these novel algorithms and the accuracy of their models are experimentally validated in different scenarios.

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Interoperability, flexibility, and adaptability are key requirements of future internet applications. Convergence of contents, services, things, and networks can be the cornerstone to fulfill these requirements. Such rich and composite sources of data and processing capabilities call for a structured and formal approach that manages and capitalizes heterogeneous information. This paper proposes an approach to the run-time composition of software system architectures, aimed at addressing goals revealed at runtime. The approach is grounded on a graph model characterized by two control levels: a metamodeling and an instantiation level. At metamodeling level, the graph describes facts that may occur in a scenario of interest, processes triggered by facts, and technologies available to execute processes. The actual occurrence of facts, together with the deriving processes and technologies, is managed at instantiation level, with reference to an application-specific model. In particular, the paper proposes an algorithm that determines an optimal way to manage a change in the run-time environment, by finding a minimum cost path in the model. The usefulness of the proposed approach and its applicability to actual scenarios have been validated in an example smart home environment.

Ahstract-The IEEE 802.15.4 standard is widely recognized as one of the most successful enabling technologies for short range low rate wireless communications. Although it provides all the details of both MAC and PHY layers of the protocol stack, the standard also explains specific methodologies to protect MAC packets through symmetric-key cryptography techniques under several security options. However, the orchestration of available security profiles and the management of key negotiation schemes is delegated to upper layers. In support of this feature, this work describes a standard compliant security framework aimed at proposing: (i) different kind of security architectures, (ii) an efficient mechanism for initializing a secure IEEE 802.15.4 domain, and (iii) a lightweight mechanism to negotiate link keys among devices. Experimental tests have been conducted to demonstrate the behavior of the proposed solution in real environments. Obtained results clearly show that the enabling of security features in constrained nodes requires additional computational efl'orts, which involve a not negligible growth of communication latencies. Such findings have to be carefully considered when designing and developing enhanced applications in future and secured Internet of Things (loT) systems.

With reference to the IEEE 802.15.4 standard, many solutions have been formulated to face the different facets of layer-2 security. Unfortunately, the opportunities and subtleties arising from their joint adoption has been not investigated, due to the lack of an integrating framework. To this end, hereby a novel standard compatible framework is proposed, which is able to orchestrate several layer-2 security mechanisms with a limited computational footprint. Conceived as a distributed scheme, it covers the following key features: (i) multiple security configurations in homogeneous and heterogeneous scenarios; (ii) adaption to dynamic networks; (iii) lean and scalable initialization functionalities; (iv) lightweight Key Management Protocol; and (v) resilience to several attacks. The robustness against security attacks have been evaluated through a wellknown automatic cryptographic protocol verifier, namely ProVerif. Moreover, to further demonstrate its effectiveness, the proposed framework has been implemented within the emerging OpenWSN protocol stack, experimentally evaluated, and compared with respect to the ZigBee IP security architecture, which integrates the Symmetric Key-Key Establishment protocol (SKKE). Results clearly show that, although security features in constrained nodes incur not negligible computational costs (which impair latencies and energy efficiency), the proposed approach always guarantees better performances with respect to the ZigBee IP security architecture. In fact, it speeds up the configuration of

International audienceThe Internet of Things (IoT) paradigm envisions an interconnected world where things can communicate with each other, transmit state information and execute smart tasks. The number of devices connected in Internet has been growing exponentially in the past years and the Machine-to-Machine plays a major role in enabling IoT paradigm while it is expected that in the near future billion of devices will be connected. Till now many vertical solutions in the M2M domain exist. To bridge this gap , the European Telecommunications Standards Institute (ETSI) has defined SmartM2M a horizontal service layer that separates the communication part from the application domain and guaranteeing interoperability among different technologies. Each device independently from the technology should register and post data to the service layer, which makes them available to applications in a seamless way. However the integration with very constrained devices like a 6LoWPAN based network is not straight forward. In this paper at first it is analyzed the problem of the hierarchical Uniform Resource Identifier (URI) in the SmartM2M standard specifications. Then a new non hierarchical resource structure is presented which enables the use of very short overall URI for constrained devices

Interoperability, flexibility and adaptability are key requirements of Future Internet applications. Convergence of contents, services, things and networks seems to be the cornerstone to fullfill these requirements. In this paper we propose a model for runtime composition of software applications in sensors newtworks based on data, processes and technology, in order to design an "on the fly" architecture of a software system. The model is graph-based and composed by two control levels: a formal model and the instantiation level. An algorithm extracts a subgraph that identifies the applications to be executed according to changes in the external context. The proposed approach has been instantiated in a use case example in a smart home environment, to evaluate the usefulness of the approach and the applicability of the model in actual scenarios.