Time-Sensitive Networking Research Articles

Reliability Optimization of Traffic Routing in Train Communication Networks Based on Faulty Link Diagnosis

With the increasing adoption of industrial Ethernet in train communication network (TCN), the limitations of insufficient reliability and incompatibility between different Ethernet technologies have become increasingly apparent. To address these challenges, time‐sensitive networking (TSN) has emerged as a solution, enabling multi‐network convergence and enhancing data transmission determinism and reliability through techniques such as frame replication and elimination for reliability (FRER). However, the utilization of these policies will adversely affect schedulability due to increased network load. To address the issue of link failures in TCN topologies, a routing policy based on faulty link diagnosis is proposed. The proposed policy utilizes an improved max‐min ant system (IMMAS) for diagnosing and resolving faulty links. Furthermore, a routing optimization algorithm is introduced to enhance transmission reliability by planning alternative paths for traffic. To evaluate the performance of the proposed routing algorithm, multiple sets of test cases are conducted separately under different failure scenarios to compare them with other routing policies. The results demonstrate the superior reliability of the proposed routing policy over alternative approaches. Additionally, the traffic utilizing the proposed routing policy show improved schedulability following integer linear programming (ILP) scheduling. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

Software-Defined Time-Sensitive Networking for Cross-Domain Deterministic Transmission

With the rapid development of Industrial 4.0, massive emerging time-critical applications pose new demands for industrial networks, such as strict latency boundaries, ultra-reliable transmission, and so on. Time-Sensitive Networking (TSN) is well suited for these demanding scenarios due to its support for deterministic transmission based on Ethernet. However, many use cases in real industrial scenarios involve non-TSN domains, and, thus, the network requires providing deterministic transmission across non-TSN domains to support them. To this end, this paper proposes a novel Software-Defined Time-Sensitive Networking (SD-TSN) framework that integrates the determinism of TSN and scalability of Software-Defined Networking (SDN). SD-TSN exploits the coordination between the coordinated controller and different domain controllers to bound non-deterministic queuing delays in a way that guarantees determinism. In particular, we designed a multi-domain time-aware traffic scheduling model, which harmonizes the time-aware shaper (TAS) in TSN and time-slots in non-TSN domains based on a global view, generating transmission schedules for each domain. A prototype testbed was built to conduct the experiments. The evaluation results demonstrate that the proposed method can efficiently achieve bounded delay and low delay variations in the transmission across non-TSN domains.

Low-Latency Wireless Network Extension for Industrial Internet of Things.

The timely delivery of critical messages in real-time environments is an increasing requirement for industrial Internet of Things (IIoT) networks. Similar to wired time-sensitive networking (TSN) techniques, which bifurcate traffic flows based on priority, the proposed wireless method aims to ensure that critical traffic arrives rapidly across multiple hops to enable numerous IIoT use cases. IIoT architectures are migrating toward wirelessly connected edges, creating a desire to extend TSN-like functionality to a wireless format. Existing protocols possess inherent challenges to achieving this prioritized low-latency communication, ranging from rigidly scheduled time division transmissions, scalability/jitter of carrier-sense multiple access (CSMA) protocols, and encryption-induced latency. This paper presents a hardware-validated low-latency technique built upon receiver-assigned code division multiple access (RA-CDMA) techniques to implement a secure wireless TSN-like extension suitable for the IIoT. Results from our hardware prototype, constructed on the IntelFPGA Arria 10 platform, show that (sub-)millisecond single-hop latencies can be achieved for each of the available message types, ranging from 12 bits up to 224 bits of payload. By achieving one-way transmission of under 1 ms, a reliable wireless TSN extension with comparable timelines to 802.1Q and/or 5G is achievable and proven in concept through our hardware prototype.

Enhanced FRER Mechanism in Time-Sensitive Networking for Reliable Edge Computing.

Time-Sensitive Networking (TSN) and edge computing are promising networking technologies for the future of the Industrial Internet. TSN provides a reliable and deterministic low-latency communication service for edge computing. The Frame Replication and Elimination for Reliability (FRER) mechanism is important for improving the network reliability of TSN. It achieves high reliability by transmitting identical frames in parallel on two disjoint paths, while eliminating duplicated frames at the destination node. However, there are two problems with the FRER mechanism. One problem is that it does not consider the path reliability, and the other one is that it is difficult to find two completely disjoint path pairs in some cases. To solve the above problems, this paper proposes a method to find edge-disjoint path pairs considering path reliability for FRER in TSN. The method includes two parts: one is building a reliability model for paths, and the other one is computing a working path and a redundant path with the Edge-Disjoint Path Pairs Selection (EDPPS) algorithm. Theoretical and simulation results show that the proposed method effectively improves path reliability while reducing the delay jitter of frames. Compared with the traditional FRER mechanism, the proposed method reduces delay jitter by 15.6% when the network load is 0.9.

Design and implementation of a frame preemption model without guard bands for time-sensitive networking

In time-sensitive networks, the frames of time-triggered (TT) flows need to be transmitted in scheduled slots. To avoid the interference of frames from other flows to the frames of the TT flows, guard bands are generally reserved prior to scheduled slots. The time-sensitive networking (TSN) standard, IEEE 802.1Qbu, specifies a frame preemption model that enables frames of TT flows (preemption frames) to preempt frames of other flows (preempted frames). According to this model, preempted frames are divided into fragments that are transmitted in the gaps of preemption frames. Consequently, the IEEE 802.1Qbu model reduces the guard band from the longest Ethernet frame (typically 1518 bytes) to 123 bytes, which improves the bandwidth utilization and delay performance of preempted frames without causing frame disorder. However, in scenarios in which the preempted frame load is heavy, and the length is short, numerous guard bands smaller than 123 bytes are generated. These guard bands prevent the IEEE 802.1Qbu model from transmitting preempted frame fragments, resulting in a considerable decrease in bandwidth utilization. To solve this problem, we propose a novel frame preemption model without guard bands, based on a padding and splicing mechanism. While ensuring that preemption frames are transmitted according to scheduled slots, this model can transmit preempted frames within arbitrary byte gaps based on the schedule without obtaining the length of the preempted frames in advance. We compared the transmission-delay performance of the proposed model with that of the IEEE 802.1Qbu model using a theoretical analysis. The evaluation results obtained from heavily loaded preemption frame scenarios revealed that the proposed model improved link utilization by 32.8% relative to the IEEE 802.1Qbu model and reduced the transmission delay by more than one order of magnitude. Moreover, when the IEEE 802.1Qbu model fails, the proposed model still transmits 60% of preempted frames.

Analysis of End-to-End Delay in the Transport Segment of Fronthaul 4G/5G Networks Based on TSN Technology

One of the characteristic features of 4G/5G mobile networks is the spatial separation of functional blocks. The corresponding segments of the xHaul transport network are used to connect these blocks. One of them is the Fronthaul front end segment, which connects remote radio equipment with their control equipment. The data streams of standard CPRI/eCPRI radio interfaces in this segment impose strict requirements on the quality of service and, above all, on delays. To meet these requirements, it was proposed to use in the Fronthaul segment Ethernet bridge network based on the technology of time-sensitive networks TSN (Time Sensitive Networking), which provides determinated delays, reliable packet delivery and high accuracy of synchronization of nodes in the network. The IEEE 802.1CM standard describes profiles of TSN networks that defines the functions, options, configurations, default values, protocols and procedures of bridges, stations and local networks required to build the Fronthaul transport segment. The article presents a methodology for determining the maximum end-to-end traffic delays of standard CPRI/eCPRI radio interfaces in the Fronthaul segment of 4G/5G networks, built on the basis of TSN technology, in accordance with the requirements of IEEE 802.1CM standard. Two main components of end-to-end delay are identified ‒ delays in TSN bridges and delays in xEthernet channels. For high-priority traffic flows of CPRI/eCPRI radio interfaces in bridges, characteristic cases of mutual influence of flows arriving simultaneously at different input ports are given. An example of numerical calculation is given, which allowed to determine the permissible physical length of the Fronthaul segment at a given boundary end-to-end delay of transmission of high-priority traffic.

Enhanced Real-time Scheduling of AVB Flows in Time-Sensitive Networking

Time-Sensitive Networking (TSN) realizes high bandwidth and time determinism for data transmission and thus becomes the crucial communication technology in time-critical systems. The Gate Control List (GCL) is used to control the transmission of different classes of traffic in TSN, including Time-Triggered (TT) flows, Audio-Video-Bridging (AVB) flows, and Best-Effort (BE) flows. Most studies focus on optimizing GCL synthesis by reserving the preceding time slots to serve TT flows with the strict delay requirement, but ignore the deadlines of non-TT flows and cause the large delay. Therefore, this paper proposes a comprehensive scheduling method to enhance the real-time scheduling of AVB flows while guaranteeing the time determinism of TT flows. This method first optimizes GCL synthesis to reserve the preceding time slots for AVB flows, and then introduces the Earliest Deadline First (EDF) method to further improve the transmission of AVB flows by considering their deadlines. Moreover, the worst-case delay (WCD) analysis method is proposed to verify the effectiveness of the proposed method. Experimental results show that the proposed method improves the transmission of AVB flows compared to the state-of-the-art methods.

Joint Routing and Scheduling Optimization of In-Vehicle Time-Sensitive Networks Based on Improved Grey Wolf Optimizer

Joint Routing and Scheduling Optimization of In-Vehicle Time-Sensitive Networks Based on Improved Grey Wolf Optimizer

Towards Functional Safety in Dynamic Distributed Systems

Functional safety (FS) is a well-established concept to avoid technical systems to cause harm during operation. Since FS is based on information exchange, the communication infrastructure plays a vital role to enable FS. Black channel or grey channel approaches are the basis for achieving effective and efficient FS schemes. While simple safety functions (SFs) can be implemented using point-to-point (P2P) transmission protocols, they are usually not suitable to provide FS in dynamic distributed systems (DDSs). This paper discusses time-sensitive networking (TSN) as an important approach for providing FS in wireless TSN (W-TSN) and evaluates the achievable safety integrity levels (SILs) for applications based on PROFISafe running over W-TSN. A discussion on initial ideas for providing FS in DDSs reveals that FS concepts have to be designed and optimized jointly with communication protocols beyond P2P transmission to improve the resulting efficiency required for applying the concepts in industrial processes.

Traffic Classification and Packet Scheduling Strategy with Deadline Constraints for Input-Queued Switches in Time-Sensitive Networking

Deterministic transmission technology is a core key technology that supports deterministic real-time transmission requirements for industrial control in Time-Sensitive Networking (TSN). It requires each network node to have a deterministic forwarding delay to ensure the real-time end-to-end transmission of critical traffic streams. Therefore, when forwarding data frames, the switch nodes must consider the time-limited requirements of the traffic. In the input-queued switch system, an algorithm for clock-synchronized deterministic network traffic classification scheduling (CSDN-TCS) is proposed to address the issue of whether a higher-quality-of-service (QoS) performance can be provided under packet deadline constraints. First, the scheduling problem of the switch is transformed into a decomposition problem of the traffic matrix. Secondly, the maximum weight-matching algorithm in graph theory is used to solve the matching results slot by slot. By fully utilizing the slot resources, as many packets as possible can be scheduled to be completed before the deadline arrives. For two types of packet scheduling problems, this paper uses the maximum flow algorithm with upper- and lower-bound constraints to move packets from a larger deadline set to idle slots in a smaller deadline set, enabling early transmission, reducing the average packet delay, and increasing system throughput. When there are three or more types of deadlines in the scheduling set, this scheduling problem is an NP-hard problem. We solve this problem by polling the two types of scheduling algorithms. In this paper, simulation experiments based on the switching size and line load are designed, and the Earliest Deadline First (EDF) algorithm and the Flow-Based Iterative Packet Scheduling (FIPS) algorithm are compared with the CSDN-TCS algorithm. The simulation results show that under the same conditions, the CSDN-TCS algorithm proposed in this paper outperforms the other two algorithms in terms of success rate, packet loss rate, average delay and throughput rate. Compared with the FIPS algorithm, the CSDN-TCS algorithm has lower time complexity under the same QoS performance.

Efficient Task-Network Scheduling With Task Conflict Metric in Time-Sensitive Networking

With the rapid development of Industrial Internet of Things (IIoT), Time-Sensitive Networking (TSN) with deterministic and real-time features has gained broad interest. However, most existing research focuses on the network scheduling with fixed task placement and computing resource allocation, restricting the scheduling space of coupled task-network. To tackle this coupling problem, an efficient task-network scheduling (ETNS) scheme is proposed in this paper for time-sensitive networking. A task-conflict metric (TCM) is established to quantify the competition degree of scheduling resources. For increasing the overall scheduling space, a TCM-aware pre-scheduling method is proposed by optimizing task placement and routing paths to reduce the potential conflicts between tasks. Integrated with the pre-scheduling method, we design a TCM-aware parallel group-scheduling algorithm by reducing the conflicts between task groups to enhance schedulability and scalability. Experiments show that our ETNS scheme significantly improves the schedulability and scalability performances compared with the existing scheduling approaches. The larger number of tasks, the higher the performance improvement.

Hybrid Scheduling of Tasks and Messages for TSN-Based Avionics Systems

Time-Sensitive Networking (TSN) has been widely considered as a promising networking candidate for avionics systems due to its capability of deterministic communication. In such TSN-based avionics systems, the network scheduling enables the timely transmission of messages. However, this is insufficient to satisfy the real-time requirements of functions, since functions involve the chain-execution of several tasks where messages only serve for the inter-task communication. In order to enhance the functionality of TSN-based avionics systems, scheduling should be extended from the network level to the system level to coordinate message transmission with task execution. Then, how to efficiently implement the hybrid scheduling of tasks and messages becomes an important issue. In this paper, we construct a novel hybrid scheduling framework for TSN-based avionics systems, which consists of system consistency constraints, in-loop function delay calculation, and two hybrid scheduling algorithms. Consistency constraints restrict the unexpected interaction of messages and tasks for hybrid scheduling to guarantee the system-level determinism. Function delay is the end-to-end delay of the task chain, and its calculation provides the optimization objective for hybrid scheduling indicated by two metrics, namely reaction delay and age delay. Scheduling algorithms improve solving efficiency and functional performance through the incremental strategies of message dynamic ordering and task-message rescheduling. Experimental results verify that, compared with exiting scheduling work which considers the dependency of messages on tasks, our work can complete complex scheduling for large systems even with hundreds of functions, and can reduce function delays by 69% in reaction delay and 37% in age delay.

Scheduling Time-Critical Traffic With Virtual Queues in Software-Defined Time-Sensitive Networking

The emerging applications in vertical industries generate diverse time-critical traffic flows with bounded delay requirements. Time-Sensitive Networking (TSN) enhances the traditional Ethernet by using Time-Aware Shaper (TAS), providing delay guarantees for traffic flow transmission. However, the fixed scheduling granularity of physical queues in TAS can bring an obstacle for the flow isolation in per-flow scheduling, such as the complex computing and configuration. This paper proposes a method of Virtual Queues-based Time-Aware Traffic Scheduling (VQ-TATS) in Software-Defined Time-Sensitive Networking (SD-TSN). SD-TSN is a networking architecture that integrates the determinism guarantees of TSN and flexible network resource allocation of Software-Defined Networking (SDN). Through the capability of SD-TSN, the physical queues resource is virtualized for VQ-TATS. VQ-TATS includes the VQ clustering and VQ mapping stages. VQ clustering aggerates virtual queues to adapt to the scheduling granularity of TAS. VQ mapping builds the relationship between virtual and physical queues and generates the gate control list of TAS. The clustering and mapping algorithms are also designed to perform VQ-TATS. The evaluation in an industrial control use case shows the effectiveness of the proposed method in schedulability and runtime.

5G Physical Layer-Based Procedure to Support Time-Sensitive Networking

Deploying 5G in new and diverse use cases, such as Industry 4.0 and factory automation, requires 5G systems to harmonize with the communication technologies used in these industries. To this end, 3GPP Release 16 and Release 17 have made significant progress in integrating 5G systems with the IEEE 802.1 working group specifications on Time-Sensitive Networking (TSN). This paper explains a method and architecture for supporting TSN over a wireless channel in a 5G network that adds the TSN synchronization function in a Small Cell gNB implementing the TSN Translator function (SC-TT). This TSN-capable small cell provides TSN over the wireless network to synchronize UEs with the Grand Master (GM) using the physical layer signal of the 5G radio frame and the transmission of the GM reference time to provide high-precision synchronization. This paper explores the pivotal role of a Slot Indicator Signal in enhancing synchronization precision, ensuring that the UE-GM synchronization occurs within an exceptionally narrow timeframe as small as 10 ns.

IEEE 802.1 Zaman Hassas Araç-İçi Haberleşme Ağları için Siber Güvenlik: Güncel Gelişmeler ve Hizmet Reddi Saldırılarının Etki Analizi

Dedicated computers control the operation of Cyber Physical Systems such as in-vehicle architectures with the help of sensors and actuators. Securing the real-time communication technologies for in-vehicle platforms attracts the attention of the research community. IEEE 802.1 Time Sensitive Networking (TSN) task group targets the standardization of Ethernet-based deterministic communication technologies due to its high bandwidth and low cost. IEEE P802.1DG working group specifies the profile for secure and real-time automotive embedded systems relying on TSN, which is envisioned to be widely used in future in-vehicle platforms. In this paper, we present an elaborate review of the research work on the security of in-vehicle communication networks with TSN support, and define various Denial of Service (DoS) attack scenarios targeting the real-time traffic in in-vehicle networks. We evaluate the impact of our attack scenarios on the performance of two different realistic in-vehicle communication networks with varying sizes. Experimental results show that DoS attacks can lead to severe consequences disrupting the healthy operation of safety-critical functions in a TSN-compliant in-vehicle network.

A novel low-latency scheduling approach of TSN for multi-link rate networking

Time Sensitive Networks (TSN), as an important representative of deterministic networks, provide low-latency and highly reliable communication services for the growing network applications that have strict requirements. Cyclic Queuing and Forwarding (CQF) is a well-known mechanism proposed by IEEE 802.1Qch for low-latency flow control of time-sensitive networks. It achieves bounded end-to-end delay and jitter transmission through a set of queues without complicated queue gating. However, most of the current work overlooks the widespread existence of multi-link rate networks in LANs and WANs, and the single-cycle CQF is unable to adjust different link rates, resulting in low bandwidth utilization and high latency. In this paper, we propose a novel scheduling approach named Multi-Cycle CQF (MCCQF) to solve the transmission problem in multi-link rate networks, aiming to reduce deterministic end-to-end delay and improve link bandwidth utilization. In addition, we formulate the scheduling constraints, being of guiding significance for designing the transmission of multi-link-rate networks, and we design an online scheduling algorithm based on it. We compare the proposed scheme with the single-cycle CQF online scheduling algorithm in hierarchical multi-link-rate networking scenarios, and the evaluation shows that our algorithm achieves better end-to-end ultra-low latency (38.9% reduction) with a smaller schedulability gap compared with single-cycle CQF. And we also improved the schedulability based on MCCQF by utilizing internal offset.

Time-Sensitive Network Simulation for In-Vehicle Ethernet Using SARSA Algorithm

In order to more accurately analyze the problem of time delay simulation and calculation in the time-sensitive network (TSN) of vehicular Ethernet, a TSN reservation class data delay analysis model improved based on the State–Action–Reward–State–Action (SARSA) reinforcement learning algorithm is proposed. Firstly, the TSN data queue forwarding delay model and reservation class data delay analysis intelligent body model are established, then the TSN traffic scheduling mechanism is improved by the SARSA reinforcement learning algorithm, and the improved TSN network reservation class data analysis model is established for the uncertainty of traffic scheduling in the network; finally, the fitting performance of the proposed method is verified by simulation and experimental validation. The results show that the deviation between the two is less than 5% under different BE loads, i.e., the established reservation class data delay analysis model is able to correctly fit the scheduling mechanism of the vehicle-mounted TSN network, which proves the reasonableness of the model simulation.

Modeling Time-Sensitive Networking Using Timed Continuous Petri Nets

Time-Sensitive Networking (TSN) is a set of standards designed to provide determinism to Ethernet or wireless networks for real-time applications. Network Calculus (NC) is the best-known formal tool for TSN analysis, but it is hard to apply in scenarios of changing conditions. Petri Nets can potentially overcome some limitations of NC, but they have rarely been used as an analytical tool for TSN. This work presents a novel modeling methodology exploiting Timed Continuous Petri Nets (TCPNs) to abstract and analyze TSN nodes.

Time-Sensitive Networking in Low Latency Cyber-Physical Systems

Time-Sensitive Networking in Low Latency Cyber-Physical Systems

An Efficient Hypergraph-Based Routing Algorithm in Time-Sensitive Networks

An Efficient Hypergraph-Based Routing Algorithm in Time-Sensitive Networks