A Survey of Limitations and Enhancements of the IPv6 Routing Protocol for Low-power and Lossy Networks: A Focus on Core Operations <s>  <s> This paper addresses the Internet of Things. Main enabling factor of this promising paradigm is the integration of several technologies and communications solutions. Identification and tracking technologies, wired and wireless sensor and actuator networks, enhanced communication protocols (shared with the Next Generation Internet), and distributed intelligence for smart objects are just the most relevant. As one can easily imagine, any serious contribution to the advance of the Internet of Things must necessarily be the result of synergetic activities conducted in different fields of knowledge, such as telecommunications, informatics, electronics and social science. In such a complex scenario, this survey is directed to those who want to approach this complex discipline and contribute to its development. Different visions of this Internet of Things paradigm are reported and enabling technologies reviewed. What emerges is that still major issues shall be faced by the research community. The most relevant among them are addressed in details. <s> BIB001 </s> A Survey of Limitations and Enhancements of the IPv6 Routing Protocol for Low-power and Lossy Networks: A Focus on Core Operations <s>  <s> This paper provides an overview of the Internet of Things (IoT) with emphasis on enabling technologies, protocols, and application issues. The IoT is enabled by the latest developments in RFID, smart sensors, communication technologies, and Internet protocols. The basic premise is to have smart sensors collaborate directly without human involvement to deliver a new class of applications. The current revolution in Internet, mobile, and machine-to-machine (M2M) technologies can be seen as the first phase of the IoT. In the coming years, the IoT is expected to bridge diverse technologies to enable new applications by connecting physical objects together in support of intelligent decision making. This paper starts by providing a horizontal overview of the IoT. Then, we give an overview of some technical details that pertain to the IoT enabling technologies, protocols, and applications. Compared to other survey papers in the field, our objective is to provide a more thorough summary of the most relevant protocols and application issues to enable researchers and application developers to get up to speed quickly on how the different protocols fit together to deliver desired functionalities without having to go through RFCs and the standards specifications. We also provide an overview of some of the key IoT challenges presented in the recent literature and provide a summary of related research work. Moreover, we explore the relation between the IoT and other emerging technologies including big data analytics and cloud and fog computing. We also present the need for better horizontal integration among IoT services. Finally, we present detailed service use-cases to illustrate how the different protocols presented in the paper fit together to deliver desired IoT services. <s> BIB002
he ever-tighter integration of physical world with computing has given birth to a new communication paradigm referred to as the Internet of Things (IoT) BIB001 BIB002 . One of the building blocks of the IoT is the Low-power and Lossy Network (LLN), a collection of interconnected embedded devices, such as sensor nodes, typically characterized by constraints on both node survey can be summarized as follows:  We provide a thorough background on LLNs environments, communication technologies and different LLNs routing requirements within the context of IoT applications.  We present a comprehensive overview of RPL's limitations and drawbacks reported in the literature that are related to its core operations (i.e. routing selection and optimization, routing maintenance operations and downward routing).  We provide an extensive survey and an in-depth analysis of research efforts made to address the limitations of RPL and assess where they still fall short of.  We present an outline of the future research directions and open issues. The main findings of this survey is that RPL's extensions were only partially successful in addressing its limitations. Hence, a further research into overcoming RPL's limitations that are not fully addressed is needed. We articulate that the main issues that RPL's extensions have not addressed successfully are the efficient construction of downward routes, load-balancing and metric composition.