Routing algorithms for time sensitive networks

IEEE 802.1Qbv standard is an enhancement introduced by Time Sensitive Network Task Group to provide real time communication in a converged Ethernet network capable of transmitting both time critical traffic and best effort traffic. The standard includes a gating mechanism which controls the access to the transmission medium at the egress port of a switch, allowing transmission of frames from the specified queue. The gating events are time triggered and are programmed using a transmission schedule. A transmission schedule is a cyclic schedule that can be generated using various independent scheduling methods. However, the first step to each method involves routing the traffic across the network, followed by computation of gate schedules along the route. Due to lack of a standard, assessment of the quality of a schedule is difficult. Therefore independent metrics are used to measure the quality of schedule generated by different scheduling methods. However, the aim of each scheduling method is to transmit maximum amount of data traffic in a single cycle of a schedule. This thesis proposes that routing impact the quality of a transmission schedule irrespective of the scheduling method used. To begin evaluations showing the impact of routing algorithms on the data load distribution across the network are present. Followed by evaluations of the impact of data load distribution on the quality of a transmission schedule. Consequently establishing a direct relation between routing of the data traffic and the quality of a schedule. In response a generic routing algorithm aimed at optimizing the data load distribution is presented. The algorithm is based on heuristic algorithm Tabu Search to make it scalable in nature, allowing its use across different scenarios. We evaluate the algorithms with respect to data load distribution, impact on the quality of a schedule and scalability

Formal Scheduling Constraints for Time-Sensitive Networks

In recent years, the IEEE 802.1 Time Sensitive Networking (TSN) task group has been active standardizing time-sensitive capabilities for Ethernet networks ranging from distributed clock synchronization and time-based ingress policing to frame preemption, redundancy management, and scheduled traffic enhancements. In particular the scheduled traffic enhancements defined in IEEE 802.1Qbv together with the clock synchronization protocol open up the possibility to schedule communication in distributed networks providing real-time guarantees. In this paper we formalize the necessary constraints for creating window-based IEEE~802.1Qbv Gate Control List schedules for Time-sensitive Networks (TSN). The resulting schedules allow a greater flexibility in terms of timing properties while still guaranteeing deterministic communication with bounded jitter and end-to-end latency

A journey into time-triggered communication protocols with a focus on Ethernet TSN

This presentation provides an historical perspective on time-triggered (TT) protocols and highlights a few possible misconceptions about TT communication. The presentation is organized as follows: 1) landscape of real-time (wired) communication networks, 2) Time-triggered (TT) protocols evolution: TTP, FlexRay, TTEthernet, TSN/TAS (IEEE802.1Qbv) 3) Misconceptions about TT communication 4) Takeaways and what is ahead of us

5G Configured Grant Scheduling for 5G-TSN Integration for the Support of Industry 4.0

Factories are evolving towards digitalized databased ecosystems under the paradigm of the Industry 4.0 where new industrial services allow the implementation of more robust, resilient and customized manufacturing systems. Such services (e.g., digital twins, extended reality or cooperative robots) will require highly reliable and deterministic communication networks capable of supporting stringent latency and reliability requirements. 5G networks and their future evolution have the necessary capabilities to meet these requirements. However, the use of 5G in industrial environments requires its effective and efficient integration with Time Sensitive Networking (TSN), which is becoming the standard wired technology for Industry 4.0 environments. TSN provides unprecedented deterministic service levels with perfectly bounded latencies. The integration of the industrial 5G and TSN networks will be key to support the flexibility and determinism demanded by the Industry 4.0 paradigm. A critical aspect to achieve this integration is the coordination of the schedulers of both networks. TSN has information about the capabilities of the 5G-TSN integrated network, and it is in charge of deciding the path and scheduling for each TSN traffic flow. The scheduling in 5G must be done according to the scheduling decisions and information provided by TSN to guarantee the end-to-end latency requirements of TSN traffic. In this context, this paper proposes a novel Configured Grant scheduling scheme for 5G integrated into a TSN network that aims to meet the latency requirements of the different TSN flows. The proposed scheme exploits the information provided by TSN about the characteristics of the TSN traffic to coordinate its decision with the scheduling of TSN. This study demonstrates that the proposed scheduling scheme considerably increases the number of TSN flows that can be satisfactorily served in the integrated 5G-TSN network compared with a commonly used Configured Grant (CG) scheduling scheme

Stability-Aware Integrated Routing and Scheduling for Control Applications in Ethernet Networks

Real-time communication over Ethernet is becoming important in various application areas of cyber-physical systems such as industrial automation and control, avionics, and automotive networking. Since such applications are typically time critical, Ethernet technology has been enhanced to support time-driven communication through the IEEE 802.1 TSN standards. The performance and stability of control applications is strongly impacted by the timing of the network communication. Thus, in order to guarantee stability requirements, when synthesizing the communication schedule and routing, it is needed to consider the degree to which control applications can tolerate message delays and jitters. In this paper we jointly solve the message scheduling and routing problem for networked cyber-physical systems based on the time-triggered Ethernet TSN standards. Moreover, we consider this communication synthesis problem in the context of control applications and guarantee their worst-case stability, taking explicitly into consideration the impact of communication delay and jitter on control quality. Considering the inherent complexity of the network communication synthesis problem, we also propose new heuristics to improve synthesis efficiency without any major loss of quality. Experiments demonstrate the effectiveness of the proposed solutions

Latency Analysis of Multiple Classes of AVB Traffic in TSN with Standard Credit Behavior using Network Calculus

Time-Sensitive Networking (TSN) is a set of amendments that extend Ethernet to support distributed safety-critical and real-time applications in the industrial automation, aerospace and automotive areas. TSN integrates multiple traffic types and supports interactions in several combinations. In this paper we consider the configuration supporting Scheduled Traffic (ST) traffic scheduled based on Gate-Control-Lists (GCLs), Audio-Video-Bridging (AVB) traffic according to IEEE 802.1BA that has bounded latencies, and Best-Effort (BE) traffic, for which no guarantees are provided. The paper extends the timing analysis method to multiple AVB classes and proofs the credit bounds for multiple classes of AVB traffic, respectively under frozen and non-frozen behaviors of credit during guard band (GB). They are prerequisites for non-overflow credits of Credit-Based Shaper (CBS) and preventing starvation of AVB traffic. Moreover, this paper proposes an improved timing analysis method reducing the pessimism for the worst-case end-to-end delays of AVB traffic by considering the limitations from the physical link rate and the output of CBS. Finally, we evaluate the improved analysis method on both synthetic and real-world test cases, showing the significant reduction of pessimism on latency bounds compared to related work, and presenting the correctness validation compared with simulation results. We also compare the AVB latency bounds in the case of frozen and non-frozen credit during GB. Additionally, we evaluate the scalability of our method with variation of the load of ST flows and of the bandwidth reservation for AVB traffic

Towards Deterministic Communications in 6G Networks: State of the Art, Open Challenges and the Way Forward

Over the last decade, society and industries are undergoing rapid digitization that is expected to lead to the evolution of the cyber-physical continuum. End-to-end deterministic communications infrastructure is the essential glue that will bridge the digital and physical worlds of the continuum. We describe the state of the art and open challenges with respect to contemporary deterministic communications and compute technologies: 3GPP 5G, IEEE Time-Sensitive Networking, IETF DetNet, OPC UA as well as edge computing. While these technologies represent significant technological advancements towards networking Cyber-Physical Systems (CPS), we argue in this paper that they rather represent a first generation of systems which are still limited in different dimensions. In contrast, realizing future deterministic communication systems requires, firstly, seamless convergence between these technologies and, secondly, scalability to support heterogeneous (time-varying requirements) arising from diverse CPS applications. In addition, future deterministic communication networks will have to provide such characteristics end-to-end, which for CPS refers to the entire communication and computation loop, from sensors to actuators. In this paper, we discuss the state of the art regarding the main challenges towards these goals: predictability, end-to-end technology integration, end-to-end security, and scalable vertical application interfacing. We then present our vision regarding viable approaches and technological enablers to overcome these four central challenges. Key approaches to leverage in that regard are 6G system evolutions, wireless friendly integration of 6G into TSN and DetNet, novel end-to-end security approaches, efficient edge-cloud integrations, data-driven approaches for stochastic characterization and prediction, as well as leveraging digital twins towards system awareness.Comment: 22 pages, 8 figure

Rede sensível ao tempo: um estudo do mapeamento sistemático

The time sensitive network (TSN) is a technology that aims to provide a whole new level of determinism. It is made up of a set of standards, which are still being developed by the IEEE 802.1 working group. Its goal is to provide a network with extremely small packet loss in addition to calculable latencies and jitter. Because it is fairly recent, there is a certain di culty nding relevant materials for conducting research or developing it. Based on this problem this problem, the objective of this work is to perform a survey, gathering the important information about this new technology. The TSN is a set of several mechanisms. Each of them belongs to the 802.1 standard group. The work done here, talks about eight of the main mechanisms. In this way, a reader who has some level of information about networks, is able to understand the most relevant mechanisms and therefore can understand how the time sensitive network works, and its full potential.A rede sensível ao tempo (TSN) é uma tecnologia que visa fornecer um nível de determinismo totalmente novo. Ela é formada por um conjunto de padrões, os quais ainda estão sendo desenvolvidos pelo grupo de trabalho IEEE 802.1. Eles visam fornecer uma rede com perda de pacotes extremamente pequena alem de latências calculáveis e jitter limitado. Por ser razoavelmente recente, ha uma certa dificuldade de encontrar materiais relevantes para a realização uma pesquisa ou para o desenvolvimento da mesma. Visando essa problemática, o objetivo deste trabalho é realizar um mapeamento sistemático reunindo as informações importantes sobre esta nova tecnologia. A TSN é um conjunto de vários mecanismos. Cada um deles pertence a um padrão do grupo 802.1. O trabalho realizado aqui, fala sobre oito dos principais mecanismos. Deste modo o leitor, que possua algum nível de informação sobre redes, é capaz de compreender os mecanismos mais relevantes e por conseguinte entender como a rede sensível ao tempo funciona e todo o seu potencial

Design of Time-Sensitive Networks For Safety-Critical Cyber-Physical Systems

A new era of Cyber-Physical Systems (CPSs) is emerging due to the vast growth in computation and communication technologies. A fault-tolerant and timely communication is the backbone of any CPS to interconnect the distributed controllers to the physical processes. Such reliability and timing requirements become more stringent in safety-critical applications, such as avionics and automotive. Future networks have to meet increasing bandwidth and coverage demands without compromising their reliability and timing. Ethernet technology is efficient in providing a low-cost scalable networking solution. However, the non-deterministic queuing delay and the packet collisions deny low latency communication in Ethernet. In this context, IEEE 802.1 Time Sensitive Network (TSN) standard has been introduced as an extension of the Ethernet technology to realize switched network architecture with real-time capabilities. TSN offers Time-Triggered (TT) traffic deterministic communication. Bounded Worst-Case end-to-end Delay (WCD) delivery is yielded by Audio Video Bridging (AVB) traffic. In this thesis, we are interested in the TSN design and verification. TSN design and verification are challenging tasks, especially for realistic safety-critical applications. The increasing complexity of CPSs widens the gap between the underlying networks' scale and the design techniques' capabilities. The existing TSN's scheduling techniques, which are limited to small and medium networks, are good examples of such a gap. On the other hand, the TSN has to handle dynamic traffic in some applications, e.g., Fog computing applications. Other challenges are related to satisfying the fault-tolerance constraints of mixed-criticality traffic in resource-efficient manners. Furthermore, in space and avionics applications, the harsh radiation environment implies verifying the TSN's availability under Single Event Upset (SEU)-induced failures. In other words, TSN design has to manage a large variety of constraints regarding the cost, redundancy, and delivery latency where no single design approach fits all applications. Therefore, TSN's efficient employment demands a flexible design framework that offers several design approaches to meet the broad range of timing, reliability, and cost constraints. This thesis aims to develop a TSN design framework that enables TSN deployment in a broad spectrum of CPSs. The framework introduces a set of methods to address the reliability, timing, and scalability aspects. Topology synthesis, traffic planning, and early-stage modeling and analysis are considered in this framework. The proposed methods work together to meet a large variety of constraints in CPSs. This thesis proposes a scalable heuristic-based method for topology synthesis and ILP formulations for reliability-aware AVB traffic routing to address the fault-tolerance transmission. A novel method for scalable scheduling of TT traffic to attain real-time transmission. To optimize the TSN for dynamic traffic, we propose a new priority assignment technique based on reinforcement learning. Regarding the TSN verification in harsh radiation environments, we introduce formal models to investigate the impact of the SEU-induced switches failures on the TSN availability. The proposed analysis adopts the model checking and statistical model checking techniques to discover and characterize the vulnerable design candidates