Configuration processes of real-time networks are costly both in terms of time and engineering effort and require the system to be shutdown during the reconfiguration phase thus resulting in significant down time as well. The convergence of IT/OT technologies is bringing a whole world of possibilities for the configuration and management of real-time networks for the automation industry. With software defined networking (SDN) features like the separation of the data and control plane and standards like IEEE 802.1 developed with the goal of adding deterministic capabilities to traditionally dynamic switched Ethernet networks, the plug and play paradigm is almost around the corner. In this paper, we go one step further and start looking into the self-configuration of real-time networks. To achieve that we propose to introduce a Configuration Agent in the network, an entity that continuously monitors the network to detect changes and automatically update the configuration to adapt to such changes while maintaining desired quality of service. We present here the complete framework for the Configuration Agent that will provide self-configuration capabilities to real-time networks. The proposed framework has IEEE 802.1 as its core, but also shows how the set of standards need to be extended in order to achieve the self-configuration requirements. Concretely we examine the role of existing communication protocols like NETCONF and OPC-UA and propose the essential ingredients (managed objects) for a YANG model for the learning aspects in the bridges, including different working modes.

Industry 4.0 and Industrial Internet of Things projects work towards adoption of standard IT technologies for real-time control networks in industrial automation. For this the IEEE 802.1 Time-Sensitive Networking (TSN) Task Group has developed and continues to develop a set of standards. One of these standards is the IEEE 802.1AS clock synchronization protocol. IEEE 802.1AS can be used to enable time-triggered communication as well as to coordinate distributed actions in industrial networks. In this paper we study the synchronization quality of IEEE 802.1AS and we are interested in whether the clocks can be synchronized with sufficiently low error such that the protocol can be used for demanding industrial automation applications. In particular, we study the protocol behavior in large-scale networks while considering critical implementation details. We report analytical worst-case results as well as probabilistic results based on simulations, that show that implementation details such as the PHY jitter and the clock granularity have a big impact on the time synchronization precision.

Ethernet-based networks have found their way into industrial communication more than a decade ago. However, while industry and academia developed Ethernet variants to also meet real-time and fault-tolerant requirements, recent standardization efforts within the IEEE 802 will broadly bring standard IT switched Ethernet in future industrial communication networks. As first standards of IEEE 802.1 time-sensitive networking (TSN) are becoming published at the time of this writing, we review these standards and formulate further research challenges that still go beyond current standard developments. Furthermore, we report on recent research results from the RetNet project that target these research challenges.

Distributed cyber-physical systems are growing in size and functionality and deterministic communication is an important requirement for those systems. The existing solutions based on the time-triggered paradigm pose certain limitations in regards to the configuration. Usually configuration is seen as a one-time event during the installation of the network. Future realtime networks need to be able to adapt more easily to changes in the network. Thus, the configuration becomes an ongoing service, e.g., as for network maintenance and re-configuration to add and remove new, respectively old, equipment. We postulate that configuration will emerge to a continued service that accompanies a real-time network throughout its different life-cycle phases. In this context of evolving and dynamic networks, we introduce the concept of a configuration agent for real-time networks and demonstrate the concept by a realization based on the time triggered paradigm.

Earliest Deadline First (EDF) is the most widely studied optimal dynamic scheduling algorithm for uniprocessor real-time systems. For realistic programs, tasks must be allowed to exchange data and use other forms of resources that must be accessed under mutual exclusion. With EDF scheduled systems, access to such resources is usually controlled by the use of Baker’s Stack Resource Protocol (SRP). In this paper we propose an alternative scheme based on deadline inheritance. Shared resources are assigned a relative deadline equal to the minimum (floor) of the relative deadlines of all tasks that use the resource. On entry to the resource a task’s current absolute deadline is subject to an immediately reduction to reflect the resource’s deadline floor. On exit the original deadline for the task is restored. We show that the worst-case behaviour of the new protocol (termed DFP—Deadline Floor inheritance Protocol) is the same as SRP. Indeed it leads to the same blocking term in the scheduling analysis. We argue that the new scheme is however more intuitive, removes the need to support preemption levels and we demonstrate that it can be implemented more efficiently.