This paper identifies that existing industrial automation standards, such as IEC/IEEE 60802 and IEEE 802.1Q, often have inconsistent definitions of traffic types. In the context of utilizing time-sensitive networking (TSN) standards for future automation systems, clear and consistent traffic characteristics and use cases should be defined to benefit from TSN features. Besides that, to facilitate the integration of TSN into the automation systems, the current standards provide a recommendation for mapping the automation traffic to the TSN traffic classes. In this paper, we propose an alternative mapping methodology for automation traffic to TSN traffic classes after presenting the existing automation traffic and their characteristics. Finally, through a case study, we show the potential of the new mapping methodology compared to the standard mapping strategy.

The Time-Sensitive Networking (TSN) Task Group of the IEEE has proposed standards to provide Ethernet with real-time guarantees, network management and fault tolerance mechanisms. In this way, the Task Group expects Ethernet to become the standard network technology for novel industrial applications with real-time and reliability requirements. TSN proposes to use space redundancy to increase the reliability of the network, but redundancy alone might not be enough to reach the reliability guarantees required by certain applications, such as offshore industrial systems. For this reason, we propose a fault diagnosis mechanism called FAUDI that represents the first step towards automatic online reconfiguration of TSN networks to adapt to faults affecting the network. We present the design of FAUDI and we model it using the UPPAAL model checker, which allows to carry out an exhaustive evaluation of FAUDI's design. We use the model to validate the design and to verify that FAUDI exhibits properties that are of paramount importance in reliable real-time systems.

In an Industrial Control System (ICS), link failures causing partitioning between the redundant controller pair can prevent synchronization. This disruption could potentially trigger incorrect redundancy role-switching procedures. Distinguishing link and node failures from each controller's perspective can effectively mitigate these dependability threats. We introduce an algorithm capable of detecting and differentiating link failures from node failures within a bounded time. The proposed algorithm leverages periodic messages generated by industrial protocols operational in network devices. Our preliminary evaluation indicates the feasibility of the proposed algorithm in terms of meeting the real-time requirements of the ICSs.

The energy transition is bringing new challenges into the electrical infrastructure in general, and in the substations in particular. Specifically, more devices are expected to be connected, increasing the demands on the network infrastructure. Time-Sensitive Networking is a promising solution to drive this transition, as it provides different real-time guarantees for critical applications, such as those executed in substations. Digital sub-stations rely on the IEC 61850 protocol to exchange information to perform the control of the grid devices. The integration of TSN into substation networks could improve the handling of this traffic and, consequently, the controllability of power grids. This paper investigates the use of TSN in an IEC 61850 process bus typically implemented in an substation. We use simulations over OMNeT++, as well as scheduling and analysis of TSN traffic to evaluate the impact on the jitter when compared to traditional solutions using IEC 61850 over non-real-time Ethernet.

As the industry trend is moving toward Ethernet-based Industrial Control Systems (ICSs) in line with the industry 4.0 paradigm, the network traffic must be monitored and managed to keep the systems reliably available. A flat converged network architecture where all the controllers, Input/Output (I/O), and supervisory systems are connected introduces mixed traffic classes competing for network resources and access to the shared medium. These traffic classes are typically managed with different Quality of Service (QoS) techniques. The challenge lies in managing end-to-end QoS in a heterogeneous environment and configuring switches according to the vendor, model, and operating software. Meanwhile, emerging greenfield technology are not deployable with switches used in today's ICS. We propose a distributed QoS supervisory agent, capable of detecting and correcting faulty QoS configurations in a contemporary heterogeneous Layer 2 switch environment. The initial results are achieved through two experimental testbeds in a use case where our agent successfully corrected the QoS configurations.

Novel production paradigms aim at increasing the efficiency and flexibility of production systems. Nonetheless, traditional industrial infrastructures lack the mechanisms needed to support these new paradigms. One of the main limiting factors is the architecture, which follows the automation pyramid in which subsystems are divided in layers depending on their functionalities. This allowed to meet the timing and dependability requirements of the production subsystems, however at the cost of limiting the exchange of information required to provide increased flexibility to the system. For this reason, in this paper we propose a new industrial architecture with a single network infrastructure to connect all the devices that conform to the industrial systems. On top of that, we design an Automatic Network Configurator to support the automatic configuration of the system. To assess the feasibility of our design and evaluate its performance, we implement the first instance of the architecture capable of supporting changes in the traffic requirements during run-time, i.e., without stopping or disrupting the system's operation. Furthermore, we use the implemented instance to measure the time required for reconfigurations.

There is a growing interest in increasing the flexibility and the mobility of industrial infrastructures to support novel industrial applications. To support this change, industrial networks must provide real-time guarantees while integrating a great variety of traffic over a cohesive network infrastructure. Specifically, there is special interest in the integration of wired and wireless communications in the industrial domain. We present a solution that integrates a Time-Sensitive Networking Ethernet network with a low-power 6TiSCH IoT network and discuss the implementation alternatives and their implications on delay and resource consumption. The main goal is to experimentally identify the research challenges and necessary enhancements for interoperability between constrained battery-driven wireless communication with the time sensitive wired networks.

Novel industrial applications are leading to important changes in industrial systems. One of the most important changes is the need for systems that are capable to adapt to changes in the environment or the system itself. Because of their nature many of these applications are distributed, and their network infrastructure is key to guarantee the correct operation of the overall system. Furthermore, in order for a distributed system to be able to adapt, its network must be flexible enough to support changes in the traffic during runtime. The Time-Sensitive Networking (TSN) Task Group has proposed a series of standards that aim at providing deterministic real-time communications over Ethernet. TSN also provides centralised online configuration and control architectures which enable the online configuration of the network. A key part in TSN’s centralised architectures is the Centralised Network Configuration element (CNC). In this work we present a first implementation of a CNC capable of scheduling time-triggered traffic and deploying such configuration in the network using the Network Configuration (NETCONF) protocol. We also assess the correctness of our implementation using an industrial use case provided by Volvo Construction Equipment.

Distributed Control Systems (DCSs) for emerging industrial control applications impose new communication requirements that cannot be satisfied by current Industrial Ethernet protocols. As a result, industry is pushing the Time-Sensitive Networking (TSN) standards as the de-facto Ethernet-based linklayer to fulfill these requirements. Adequate roadmaps are needed to support a smooth transition from Industrial-Ethernet-based legacy systems to TSN-based ones. In this context some works propose mechanisms to migrate, i.e. map, route and schedule, legacy traffic to TSN. However none of them considers traffic including streams with spatial redundancy requirements and, thus, they cannot be used to migrate legacy highly-reliable DCSs. The present work extends a previous toolchain to migrate, for the first time, legacy critical traffic that includes spatially redundant streams. Particularly, since redundancy is costly, this work proposes and compares two routing methods that consider one redundant stream per traffic.

The integration of Time-Sensitive Networks (TSN) with 5G cellular networks requires a defined architecture for network configuration and management. Although 3GPP specifications provide necessary means for the TSN-5G integration, the operation of such converged TSN-5G network remains an open challenge for the research community. To address this challenge, this paper presents the ongoing work in developing a centralized architectural model to configure the TSN-5G network, and forward traffic from TSN to 5G and vice-versa. The proposed architectural model uses knowledge of the traffic characteristics to carry out a more accurate mapping of quality of service attributes between TSN and 5G.

The IEEE Audio Video Bridging (AVB) Task Group (TG) was created to provide Ethernet with soft real-time guarantees. Later on, the TG was renamed to Time-Sensitive Networking (TSN) and its scope broadened to support hard real-time and critical applications. The Stream Reservation Protocol (SRP) is a key work of the TGs as it allows reserving resources in the network, guaranteeing the required quality of service. AVB's SRP is based on a distributed architecture, whereas TSN's is based on centralized ones. The distributed version of SRP is supported and used in TSN. Nevertheless, it was not designed to provide properties that are important for critical applications. In this article, we model SRP using UPPAAL and we study the termination and consistency. We verify that SRP does not provide such properties. Furthermore, we propose an improved protocol called Consistent Stream Reservation Protocol (CSRP) and we formally verify its correctness using UPPAAL.

The Time-Sensitive Networking (TSN) Task Group (TG) is providing Ethernet with timing guarantees, reconfiguration services and fault tolerance mechanisms. Some of TSN's targeted applications are real-time critical applications, which must provide a correct service continuously. To support these applications the TSN TG standardised a spatial redundancy mechanism. Even though spatial redundancy can tolerate permanent and temporary faults, it is not cost-effective. Instead, temporary faults can be tolerated using time redundancy. We proposed the Proactive Transmission of Replicated Frames (PTRF) mechanism to tolerate temporary faults in the links. In this work we present a new PTRF approach, a PTRF simulation model and a comparison of the approaches using exhaustive fault injection.

The Audio Video Bridging Task Group (AVB TG) from the IEEE proposed a series of standards to provide Ethernet with soft real-time guarantees. Later on, the group was renamed to Time-Sensitive Networking and its scope was broadened to provide new services to support critical applications. The Stream Reservation Protocol (SRP) stands out among the projects developed by the groups. Nonetheless, SRP was originally designed for audio/video applications and does not take into account properties that are important for critical systems; such as termination and consistency. In this work we study the termination and consistency of SRP at different levels, using a model we developed of this protocol in Uppaal. We see that SRP does not provide termination nor consistency, we discuss how this can impact critical applications and we propose solutions for all the issues detected.

Many industrial systems have specific requirements derived from the applications they execute. Specifically, the interaction of a distributed embedded control system (DECS) with the real-world imposes strict real-time (RT) and reliability requirements. For a system to be RT, it has to produce a proper result in a bounded time. On top of that, for a system to be reliable, it has to operate continuously during its mission time, and in cases in which very high reliability is needed, fault tolerance (FT) techniques are used. Moreover, these systems are often deployed in dynamic environments where the operational conditions may change in an unpredictable manner. Therefore, there is an increasing interest in creating DECSs that are capable of modifying their behavior autonomously and dynamically in response to unexpectedly changing requirements or conditions. In recent years, there is a growing trend toward using Ethernet as the network technology for DECSs. Unfortunately, the original specification of this technology lacks appropriate services to fulfill the most demanding requirements of industrial systems. In this regard, many Ethernet-based protocols and standards have been proposed along the past years to deal with these limitations. In this paper, we survey solutions that have been proposed to achieve FT in Ethernet-based DECSs, considering faults both in their nodes and communication subsystem. In addition, we discuss adaptive FT techniques that can be used to increase the flexibility of adaptive DECS. Finally, we identify future trends and open challenges to build highly reliable DECS in the future.

The Time Sensitive Networking (TSN) Task Group has been working on describing a set of standards that will provide enhanced capabilities to standard Ethernet. Specifically, they work to provide Ethernet with real-time, reliability and reconfiguration capacities. Nevertheless, this set of standards (commonly referred to as TSN) does not cover some reliability aspects that are relevant for the correct operation of critical distributed control systems. Thus, in this work we present a first proposal of a highly reliable architecture and a set of mechanisms based on TSN to support the real-time and reliability requirements of these critical systems.

Time-Sensitive Networking (TSN) is a set of technical standards that is being developed to provide Ethernet with hard real-time, reliability and flexibility services. In the last years, there has been a growing interest in increasing the connectivity of all kind of devices. This trend has reached industrial environments, where the demanding timing and reliability constraints imposed the use of specialised networks with specific features to support these requirements. Moreover, the industry has shown interest in using Ethernet as the network technology in industrial environments, due to its low cost, high bandwidth and extensive use. The ability of TSN to support both, data-oriented and traditional control traffic over the same network makes it an appealing technology to implement the next generation of industrial networks with high connectivity. Nevertheless, TSN does not cover some reliability aspects important for its deployment in critical systems. In this work we propose the implementation of time redundancy of frames in order to tolerate temporary faults in the channel and, therefore, increase the reliability of the network.

There is a growing interest in developing embedded systems capable of being deployed in dynamic environments that may change in unpredictable manners. When such systems are Distributed Embedded Systems (DESs) they must exhibit flexibility at all levels of their architecture, including the network. On the other hand, there is a clear trend in industry towards using Ethernet-based protocols at the network level of DESs. Nevertheless, Ethernet lacks appropriate support for real-time (RT) communications, mixing different RT traffic and on-line management of the Quality of Service (QoS). Several implementations of the Flexible Time-Tiggered (FTT) protocol over Ethernet were proposed to cope with these drawbacks. FTT is a master/multi-slave protocol that is able to simultaneously convey real and non-real-time traffic and provides mechanisms for dynamically changing the QoS of the network, including Admission Control (AC). The AC is a fundamental component for on-line network management, since it guarantees that each participant gets the required QoS. This paper presents the implementation in OMNeT++ of a simulation model of the AC in the FTT HaRTES switch as well as a preliminary performance study using that model.

Ethernet is gaining importance in fields such as automation, avionics and automotive. In these fields novel multimedia-based applications must coexist with traditional control systems, which leads to high diversity in size, intensity and timing requirements of the traffic traversing the channel. Multimedia traffic is characterised by having large size, low intensity and soft real-time requirements, while control traffic usually conveys small amounts of information with a high intensity and hard real-time requirements. Moreover, many modern applications must support on-line connection and disconnection of participants. Since Ethernet was designed as a general purpose data network protocol it lacks appropriate support for real-time communications and dynamic quality of service management. Several protocols were proposed to cope with these drawbacks, including Flexible Time-Triggered Switched Ethernet and, more recently, Audio Video Bridging. In this paper we discuss the importance of the admission control and make a comparison of the implementations carried out in the aforementioned protocols.

Distributed embedded systems typically have real-time and dependability requirements. Moreover, they must also be flexible to changing conditions when they are deployed in dynamic environments. The FT4FTT project aims at providing a switched Ethernet architecture that can support distributed control applications that are predictable, highly-reliable and adaptive. FT4FTT relies on the Flexible Time-Triggered Replicated Star for Ethernet (FTTRS) to tolerate channel faults. Moreover, nodes' hardware faults are tolerated by means of active node replication with majority voting. In order to coordinately trigger the execution of the tasks in the replicas, we designed the CD4NR mechanism, in which the network assists in deciding what to execute and when. This paper presents the first implementation of the CD4NR mechanism on a real prototype of FTTRS and the first testing of the complete system. For this we developed an experimental setup, based on the hardware-in-the-loop technique, running a real-time control application.

The communication subsystem of distributed embedded systems (DES) that must operate continuously and satisfy unpredictable requirement changes must be reliable and flexible. Recently the Flexible Time-Triggered Replicated Star for Ethernet (FTTRS) has been proposed as a communication subsystem that satisfies these two attributes. It is based on the master/multi-slave Flexible-Time Triggered (FTT) communication paradigm and relies on two custom switches, each with its own embedded FTT master. Both masters are active simultaneously and provide the same service. Specifically, they simultaneously and periodically broadcast so-called trigger messages (TMs) in a redundant manner to make them robust to transient channel faults. One of the functions of these TMs is to divide the communication time into rounds called elementary cycles (ECs). For the correct operation of FTTRS, it is important that all slaves agree when each EC starts and ends. A mechanism to achieve this has been recently proposed. This paper presents a first implementation of this mechanism and a series of experimental tests that constitute a first step towards building a prototype of an FTTRS network.