IEEE Time-Sensitive Networking Research Articles

Time-Sensitive Networking (TSN) for Industrial Automation: Current Advances and Future Directions

With the introduction of Cyber-Physical Systems (CPS) and Internet of Things (IoT) technologies, the automation industry is undergoing significant changes, particularly in improving production efficiency and reducing maintenance costs. Industrial automation applications often need to transmit time- and safety-critical data to closely monitor and control industrial processes. Several Ethernet-based fieldbus solutions, such as PROFINET IRT, EtherNet/IP, and EtherCAT, are widely used to ensure real-time communications in industrial automation systems. These solutions, however, commonly incorporate additional mechanisms to provide latency guarantees, making their interoperability a grand challenge. The IEEE 802.1 Time-Sensitive Networking (TSN) task group was formed to enhance and optimize IEEE 802.1 network standards, particularly for Ethernet-based networks. These solutions can be evolved and adapted for cross-industry scenarios, such as large-scale distributed industrial plants requiring multiple industrial entities to work collaboratively. This paper provides a comprehensive review of current advances in TSN standards for industrial automation. It presents the state-of-the-art IEEE TSN standards and discusses the opportunities and challenges of integrating TSN into the automation industry. Some promising research directions are also highlighted for applying TSN technologies to industrial automation applications.

Autonomous integration of TSN-unaware applications with QoS requirements in TSN networks

Modern industrial networks transport both best-effort and real-time traffic. Time-Sensitive Networking (TSN) was introduced by the IEEE TSN Task Group as an enhancement to Ethernet to provide high quality of service (QoS) for real-time traffic. In a TSN network, applications signal their QoS requirements to the network before transmitting data. The network then allocates resources to meet these requirements. However, TSN-unaware applications can neither perform this registration process nor profit from TSN’s QoS benefits.The contributions of this paper are twofold. First, we introduce a novel network architecture in which an additional device acts as a central user configuration (CUC) for TSN-unaware applications and autonomously signals their QoS requirements to the network. Second, we propose a processing method to detect real-time streams in a network and extract the necessary information for the TSN stream signaling. It leverages a Deep Recurrent Neural Network (DRNN) to detect periodic traffic, extracts an accurate traffic description, and uses traffic classification to determine the source application. As a result, our proposal allows TSN-unaware applications to benefit from TSNs QoS guarantees. Our evaluations underline the effectiveness of the proposed architecture and processing method.

Secure Time-Sensitive Software-Defined Networking in Vehicles

Current designs of future In-Vehicle Networks (IVN) prepare for switched Ethernet backbones, which can host advanced LAN technologies such as IEEE Time-Sensitive Networking (TSN) and Software-Defined Networking (SDN). In this paper, we present an integrated Time-Sensitive Software-Defined Networking (TSSDN) architecture that simultaneously enables control of synchronous and asynchronous real-time and best-effort communication for all IVN traffic classes. Despite the central SDN controller, we can validate that control can operate without a delay penalty for TSN traffic, provided protocols are properly mapped. We demonstrate how TSSDN adaptably and reliably enhances network security for in-vehicle communication. A systematic investigation of the possible control flow integrations with switched Ether-networks reveals that these strategies allow for shaping the attack surface of a software-defined IVN. We discuss embeddings of control flow identifiers on different layers, covering the range from a fully exposed mapping to deep encapsulation. We experimentally evaluate these strategies in a production vehicle, which we map to a modern Ethernet topology. Our findings indicate that visibility of automotive control flows on lower network layers enables isolation and access control throughout the network infrastructure. Such a TSSDN backbone can establish and survey trust zones within the IVN and reduce the attack surface of connected cars in various attack scenarios.

EnGINE: Flexible Research Infrastructure for Reliable and Scalable Time Sensitive Networks

Self-driving and multimedia systems have common implications: increased demand on network bandwidth and computation nodes. To cope with the current and future challenges, intra-vehicular networks (IVNs) change their layout. They are built around powerful central nodes connected to the rest of the vehicle via Ethernet. The usage of Ethernet presents a challenge, as it by design lacks support for deterministic behavior, which is crucial for real-time systems. Therefore, the IEEE Time-Sensitive Networking (TSN) task group offers standards introducing low-latency and deterministic communication into Ethernet based networks allowing coexistence of best-effort and real-time traffic. To understand the coexistence challenges, these new networked systems need to be thoroughly evaluated with IVN requirements in mind. To assess various topologies, configurations, and data traffic types in IVN setups, we introduce Environment for Generic In-vehicular Networking Experiments—EnGINE. It allows, among many others, repeatable, reproducible, and replicable TSN experiments with high precision and flexibility. EnGINE is based on commercial off-the-shelf hardware and uses the flexible Ansible framework for experiment orchestration. This allows us to configure various topologies emulating realistic behavior of IVNs or other time sensitive systems used, e.g., in industrial automation. Obtaining such realism is challenging using simulations. Based on available related work, we further address the challenges found in those networks, especially IVNs. We derive TSN domain framework requirements, provide details on design decisions for the EnGINE, and present results to show its capabilities. The results present relevant network metrics based on collected data. A key focus is on the experiment campaigns realism achieved by real IVNs’ data footage and the OS optimizations to offer real-time behavior. We believe that EnGINE provides the ideal environment for TSN experiments from different domains.

Quantitative Performance Comparison of Various Traffic Shapers in Time-Sensitive Networking

Owning to the sub-standards being developed by IEEE Time-Sensitive Networking (TSN) Task Group, the traditional IEEE 802.1 Ethernet is enhanced to support real-time dependable communications for future time- and safety-critical applications. Several sub-standards have been recently proposed that introduce various traffic shapers (e.g., Time-Aware Shaper (TAS), Asynchronous Traffic Shaper (ATS), Credit-Based Shaper (CBS), Strict Priority (SP)) for flow control mechanisms of queuing and scheduling, targeting different application requirements. These shapers can be used in isolation or in combination and there is limited work that analyzes, evaluates and compares their performance, which makes it challenging for end-users to choose the right combination for their applications. This paper aims at (i) quantitatively comparing various traffic shapers and their combinations, (ii) summarizing, classifying and extending the architectures of individual and combined traffic shapers and their Network calculus (NC)-based performance analysis methods and (iii) filling the gap in the timing analysis research on handling two novel hybrid architectures of combined traffic shapers, i.e., TAS+ATS+SP and TAS+ATS+CBS. A large number of experiments, using both synthetic and realistic test cases, are carried out for quantitative performance comparisons of various individual and combined traffic shapers, from the perspective of upper bounds of delay, backlog and jitter. To the best of our knowledge, we are the first to quantitatively compare the performance of the main traffic shapers in TSN. The paper aims at supporting the researchers and practitioners in the selection of suitable TSN sub-protocols for their use cases.

ETAS: Enhanced Time-Aware Shaper for Supporting Nonisochronous Emergency Traffic in Time-Sensitive Networks

To guarantee stringent real-time requirements of time-critical traffic in industrial systems, the IEEE time-sensitive networking (TSN) task group has standardized time-aware shaping (TAS) in IEEE 802.1Qbv, which schedules precise and periodic transmission times using preassigned traffic information. However, nonperiodic/unexpected but time-critical traffic, such as emergency events or alarms, may occur in real industrial scenarios, and TAS does not provision for performance of traffic that are unknown <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a priori</i> , nor the impact thereof on prescheduled traffic. Moreover, recalculating the schedule for every sporadic, nonisochronous event traffic is extremely difficult, complex, and costly. To address these challenges, we propose a novel enhancement to TAS, referred to as <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eTAS</i> , which defines a new scheduling rule for immediate forwarding of emergency traffic to guarantee real-time performance, while dynamically extending the scheduled time windows to protect scheduled time-critical traffic from the interference of emergency traffic. We evaluate <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eTAS</i> through extensive simulations on OMNeT++ under an advanced driver assistance system (ADAS) scenario for autonomous driving to show that <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eTAS</i> effectively allows rapid transmission of event traffic with minimal impact on scheduled traffic, even for highly congested networks.

Quantitative Performance Comparison of Various Traffic Shapers in Time-Sensitive Networking

Owning to the sub-standards being developed by IEEE Time-Sensitive Networking (TSN) Task Group, the traditional IEEE 802.1 Ethernet is enhanced to support real-time dependable communications for future time- and safety-critical applications. Several sub-standards have been recently proposed that introduce various traffic shapers (e.g., Time-Aware Shaper (TAS), Asynchronous Traffic Shaper (ATS), Credit-Based Shaper (CBS), Strict Priority (SP)) for flow control mechanisms of queuing and scheduling, targeting different application requirements. These shapers can be used in isolation or in combination and there is limited work that analyzes, evaluates and compares their performance, which makes it challenging for end-users to choose the right combination for their applications. This paper aims at (i) quantitatively comparing various traffic shapers and their combinations, (ii) summarizing, classifying and extending the architectures of individual and combined traffic shapers and their Network calculus (NC)-based performance analysis methods and (iii) filling the gap in the timing analysis research on handling two novel hybrid architectures of combined traffic shapers, i.e., TAS+ATS+SP and TAS+ATS+CBS. A large number of experiments, using both synthetic and realistic test cases, are carried out for quantitative performance comparisons of various individual and combined traffic shapers, from the perspective of upper bounds of delay, backlog and jitter. To the best of our knowledge, we are the first to quantitatively compare the performance of the main traffic shapers in TSN. The paper aims at supporting the researchers and practitioners in the selection of suitable TSN sub-protocols for their use cases.

Large-scale periodic scheduling in time-sensitive networks

The real-time and safety-critical demands posed in a variety of industrial systems can now be handled on the Ethernet architecture by virtue of the IEEE Time-Sensitive Networking task group. In particular, deterministic nature and timeliness guarantees can be achieved by time-triggered communication schedules that are enabled by the IEEE 802.1Qbv standard. However, generating such a schedule is a computationally challenging task due to several harsh constraints that must be satisfied. This problem is usually transformed into some existing formalism, e.g., Satisfiability Modulo Theories, and solved using a general third-party solver, which has the drawback of limited scalability. Except for some one-pass heuristics, such as the earliest deadline first or as-soon-as-possible scheduling, the current literature does not provide any algorithm tailored to this specific problem of scheduling time-triggered traffic in time-sensitive networks. In this paper, we develop an efficient algorithm that does not use any third-party solver and is based on the search in the space of partial schedules while being guided by the discovered conflicts. Our algorithm calculates schedules for problem instances consisting of 2000 network nodes and more than 10000 flows.

Time-Sensitive Networking in automotive embedded systems: State of the art and research opportunities

The functionality advancements and novel customer features that are currently found in modern automotive systems require high-bandwidth and low-latency in-vehicle communications, which become even more compelling for autonomous vehicles. In a recent effort to meet these requirements, the IEEE Time-Sensitive Networking (TSN) task group has developed a set of standards that introduce novel features in Switched Ethernet. TSN standards offer, for example, a common notion of time through accurate and reliable clock synchronization, delay bounds for real-time traffic, time-driven transmissions, improved reliability, and much more. In order to fully utilize the potential of these novel protocols in the automotive domain, TSN should be seamlessly integrated into the state-of-the-art and state-of-practice model-based development processes for automotive embedded systems. Some of the core phases in these processes include software architecture modeling, timing predictability verification, simulation, and hardware realization and deployment. Moreover, throughout the development of automotive embedded systems, the safety and security requirements specified on these systems need to be duly taken into account. In this context, this work provides an overview of TSN in automotive applications and discusses the recent technological developments relevant to the adoption of TSN in automotive embedded systems. The work also points at the open challenges and future research directions.

Zero Jitter for Deterministic Networks Without Time-Synchronization

The demands for deterministic network services are getting significant. IEEE Time sensitive networking (TSN) task group has aimed for deterministic services through IEEE 802 networks. TSN's solutions rely on the time-synchronization and the slot scheduling coordinated throughout a network. The former requires costly hardware implementations for accuracy and scalability. The latter requires a schedulability analysis, which is proven to be NP-complete and not scalable. For modest-to-large scale dynamic networks, a more flexible solution is necessary. We propose a scalable framework that guarantees any desired jitter upper bound, including zero jitter. The framework is composed of; packets with relative time-stamps, a network that guarantees latency bounds, and buffers at the network egress. The latency bounds of a network can be of any value. The buffer holds packets for predetermined intervals to reproduce arbitrary inter-arrival intervals to inter-departure intervals, based on the network's latency bound. The idea behind the proposed framework is to minimize the latency first with work-conserving schedulers, and then adjust the jitter at the egress of a network. We argue that this is simpler than minimizing latency and jitter at the same time. A direct benefit of such simplicity is its scalability. We examine the network solutions that guarantee latency bound, such as the DiffServ and the Flow aggregate-interleave regulator (FAIR), as the candidates for the component in the framework. We show with a case study and simulations that the proposed framework can guarantee smaller latency bounds, with zero jitter, than those of the TSN's synchronous approach.

An SDN architecture for time sensitive industrial IoT

Industrial Internet of Things (IoT) applications have diverse network session requirements. Certain critical applications, such as emergency alert relay, industrial floor evacuation, and surveillance systems, require fresh updates that can maintain the most recently delivered packets. This requires high reconfigurability to an extent where the system can measure the impact of an event and adapt the network accordingly. Several approaches have been proposed that provide high precision transmission and bounded latencies. One prominent solution strategy in the literature is based on Software Defined Networking (SDN) control to resolve latency-related issues, such as congestion, for factory floor transmissions. The OpenFlow protocol is a key interface used in SDN to create a low-latency environment. However, the existing approaches provide only offline solutions that are typically compute intensive. Therefore, this article proposes an algorithm based on simple online strategies that utilize an SDN controller with a global view of the network. More specifically, within the context of the IEEE Time Sensitive Networking (TSN) standards this article: (1) designs a control policy framework called TSNu that guarantees transmission time-slot allocations for Scheduled Traffic while mitigating network congestion, (2) develops a utility maximization approach to jointly optimize scheduling, routing, and admission control while ensuring network stability and maximizing the flow admission to the network, and (3) presents extensive theoretical analysis and simulation to evaluate the proposed TSNu design. The conducted evaluations indicate substantially improved performance compared with state-of-the-art policies.

A Novel Routing Algorithm for the Acceleration of Flow Scheduling in Time-Sensitive Networks.

IEEE Time-Sensitive Networking (TSN) Task Group specifies a series of standards such as 802.1Qbv for enhancing the management of time-critical flows in real-time networks. Under the IEEE 802.1Qbv standard, the scheduling algorithm is employed to determine the time when a specific gate in the network entities is opened or closed so that the real-time requirements for the flows are guaranteed. The computation time of this scheduling algorithm is critical for the system where dynamic network configurations and settings are required. In addition, the network routing where the paths of the flows are determined has a significant impact on the computation time of the network scheduling. This paper presents a novel scheduling-aware routing algorithm to minimize the computation time of the scheduling algorithm in network management. The proposed routing algorithm determines the path for each time-triggered flow by including the consideration of the period of the flow. This decreases the occurrence of path-conflict during the stage of network scheduling. The detailed outline of the proposed algorithm is presented in this paper. The experimental results show that the proposed routing algorithm reduces the computation time of network scheduling by up to 30% and improves the schedulability of time-triggered flows is the network.

Enhancing Schedulability and Throughput of Time-Triggered Traffic in IEEE 802.1Qbv Time-Sensitive Networks

Thanks to the standards being developed by IEEE Time-Sensitive Networking (TSN) Task Group, the classical IEEE 802.1 Ethernet architecture is now enhanced to accommodate real-time and safety-critical requirements emerging in various cyber-physical systems. The deterministic nature of the communication is achieved through the time-triggered traffic, which requires introducing strict scheduling constraints that may be an obstacle in finding a feasible schedule. In this article, we propose a simple hardware enhancement of a switch along with a relaxed scheduling constraint that increases schedulability and throughput of the time-triggered traffic but maintains the deterministic nature and timeliness guarantees in a TSN network. We give a formal proof to justify the claims and an algorithm benchmarking and experimental validation to demonstrate the gains. The results show that the number of flows that can be scheduled in the model with the relaxed constraint is on average by 75.1 % larger than in the traditional model.

Traffic-type Assignment for TSN-based Mixed-criticality Cyber-physical Systems

This article focuses on mixed-criticality applications with functions that have different timing requirements, i.e., hard real-time (HRT), soft real-time (SRT), and functions that are not time-critical (NC). The applications are implemented on distributed cyber-physical systems that use IEEE Time-sensitive Networking (TSN). TSN is the product of an IEEE effort to bring deterministic real-time capabilities to IEEE 802.3 Ethernet. TSN supports the convergence of multiple traffic types, i.e., critical, real-time, and regular “best-effort” traffic within a single network: Time-triggered (TT), where the messages are transmitted based on static schedule tables, Audio-video Bridging (AVB), for dynamically scheduled messages with a guaranteed bandwidth and bounded delays, and Best Effort (BE), for which no timing guarantees are provided. The HRT messages have deadlines, whereas we capture the quality-of-service for the SRT messages using “utility functions.” Given the network topology, the set of application messages, including their routing, and the set of available AVB classes, we are interested in determining the traffic type of each message, such that all the HRT messages are schedulable and the total utility for the SRT messages is maximized. We propose a Tabu Search-based metaheuristic to solve this optimization problem. The proposed proof-of-concept tool has been evaluated using several benchmarks, including two realistic test cases.

A Perspective on IEEE Time-Sensitive Networking for Industrial Communication and Automation Systems

Networks are a core element of many industrial and automation systems at present. Often these networks transport time- and safety-critical messages that control physical processes. Thus, timely and guaranteed delivery is an essential property of networks for such critical systems. Over the past decade, a variety of network solutions have evolved to satisfy said properties. However, these solutions are largely incompatible with each other and many system architects are forced to deploy different solutions in parallel due to their different capabilities. IEEE 802.1 Time-Sensitive Networking (TSN) is a standardization group that enhances IEEE networking standards, most prominently Ethernet-based networks, with said properties and has the unique potential to evolve as a cross-industry mainstream networking technology. In this survey paper, we give an overview of TSN in industrial communication and automation systems and discuss specific TSN standards and projects in detail as well as their applicability to various industries.

Ultra-Low Latency (ULL) Networks: The IEEE TSN and IETF DetNet Standards and Related 5G ULL Research

Many network applications, e.g., industrial control, demand ultra-low latency (ULL). However, traditional packet networks can only reduce the end-to-end latencies to the order of tens of milliseconds. The IEEE 802.1 time sensitive networking (TSN) standard and related research studies have sought to provide link layer support for ULL networking, while the emerging IETF deterministic networking (DetNet) standards seek to provide the complementary network layer ULL support. This paper provides an up-to-date comprehensive survey of the IEEE TSN and IETF DetNet standards and the related research studies. The survey of these standards and research studies is organized according to the main categories of flow concept, flow synchronization, flow management, flow control, and flow integrity. ULL networking mechanisms play a critical role in the emerging fifth generation (5G) network access chain from wireless devices via access, backhaul, and core networks. We survey the studies that specifically target the support of ULL in 5G networks, with the main categories of fronthaul, backhaul, and network management. Throughout, we identify the pitfalls and limitations of the existing standards and research studies. This survey can thus serve as a basis for the development of standards enhancements and future ULL research studies that address the identified pitfalls and limitations.

Traffic Planning for Time-Sensitive Communication

Many industries, including the automotive industry and industrial automation, have a need for reliable real-time communication. To satisfy this need, industry-specific, often proprietary, solutions have been developed in recent decades. Time-sensitive networking (TSN) is addressing a grand unification of these existing technologies to leverage cross-industry cost efficiency as well as to guarantee a stable growth path of communication capabilities. While the functionality of time-sensitive networking is exhaustively standardized in IEEE 802.1, configuration standards for TSN are largely missing. Thus, in this article we review the IEEE TSN standards, in particular 802.1Qbv, and continue to illustrate a reference model for traffic planning for time-sensitive communication. Furthermore, the article references a detailed technical report describing the complete model, which is ideally suited as a starting point for standardization and ensures the interoperability of future TSN traffic planning tools.

Tunneling Horizontal IEC 61850 Traffic through Audio Video Bridging Streams for Flexible Microgrid Control and Protection

In this paper, it is argued that some low-level aspects of the usual IEC 61850 mapping to Ethernet are not well suited to microgrids due to their dynamic nature and geographical distribution as compared to substations. It is proposed that the integration of IEEE time-sensitive networking (TSN) concepts (which are currently implemented as audio video bridging (AVB) technologies) within an IEC 61850 / Manufacturing Message Specification framework provides a flexible and reconfigurable platform capable of overcoming such issues. A prototype test platform and bump-in-the-wire device for tunneling horizontal traffic through AVB are described. Experimental results are presented for sending IEC 61850 GOOSE (generic object oriented substation events) and SV (sampled values) messages through AVB tunnels. The obtained results verify that IEC 61850 event and sampled data may be reliably transported within the proposed framework with very low latency, even over a congested network. It is argued that since AVB streams can be flexibly configured from one or more central locations, and bandwidth reserved for their data ensuring predictability of delivery, this gives a solution which seems significantly more reliable than a pure MMS-based solution.