The 6TiSCH Architecture for the Industrial Internet of Things: analysis and improvements

The Internet Engineering Task Force (IETF) is defining the 6TiSCH architecture for the Industrial Internet of Things (IIoT) to ensure reliable and timely communication. The 6TiSCH architecture is expected to play a significant role to enable the Internet of Things (IoT) paradigm in the industrial environment, where reliability and timeliness are paramount to support critical applications. 6TiSCH relies on the IEEE 802.15.4 TSCH Medium Access Control (MAC) protocol and defines a distributed management mode, in which the required network resources are computed by nodes and allocated through a distributed negotiation. Specifically, each node leverages a Scheduling Function (SF) to compute the required number of cells, and the 6top Protocol (6P) to negotiate them with their neighbors. Currently, the Minimal Scheduling Function (MSF) is under consideration for standardization as a distributed scheduling scheme. However, multiple SFs are expected to be used in real deployments, in order to accommodate the requirements of different use cases. Recently, also Autonomous scheduling schemes, which relies on a set of rules to compute the schedule in an autonomous manner, without any negotiation, have attracted the interest of researchers. In this thesis we carry out a comprehensive analysis of many aspects of the 6TiSCH architecture. First, we analyze the 6top Protocol and its interplay with the IPv6 Routing Protocol for Low-Power and Lossy Networks (RPL) to draw a set of guidelines to guarantee a reliable resource allocation process. Then, we evaluate the performance of distributed SFs and propose a new distributed SF, E-OTF, to improve the overall 6TiSCH performance. We also compare distributed and autonomous SFs to investigate the pros and cons of both the approaches in different scenarios. Then, since the previous analysis highlight that RPL may have negative impact on the 6TiSCH performance, we analyze the performance of existing Link Quality Estimation (LQE) strategies exploited by RPL and propose an extension of the 6TiSCH Minimal Configuration to reduce the LQE error. Finally, we assess the security vulnerabilities of the 6top Protocol. We prove that attacks aimed at reducing reliability and increasing energy consumption in the overall network are feasible. Thus, countermeasures should be run in order to mitigate their impact. Our comprehensive analysis of the 6TiSCH architecture highlighted multiple issues on different aspects of the architecture. In our work we proposed some solutions for some of these aspects, while others are still open issues and need to be investigated in the future in order to ensure the readiness of the 6TiSCH architecture for a secure and reliable IIoT deployment.