Design considerations for high-performance Time Sensitive Networking switches

Time-Sensitive Networking (TSN) encompasses standards to facilitate near-deterministic performance in wired networks and the integration of TSN with modern wireless systems, such as Fifth Generation (5G) systems, is intensely pursued. Consequently, TSN is examined by numerous research groups. Given the limited and costly access to TSN hardware, a reliable simulator becomes crucial. OMNeT++ is a modular simulator that can be expanded with network simulation models, such as INET, which can simulate TSN functionalities. We evaluate the accuracy of the OMNeT++ INET simulator in mirroring the physical (hardware-based) reality by comparing OMNeT++ INET simulations with measurements of two commercial TSN switches. Our evaluations encompass the generalized Precision Time Protocol (gPTP) accuracy, the Store-and-Forward (SF) and Cut-Through (CT) switching forwarding latencies, the Time Aware Shaper (TAS), and Frame Preemption (FP), including combinations of CT, TAS, and FP. We find that compared to hardware measurements, INET simulations exhibit different clock synchronization dynamics, underestimate the switching latencies, and do not support CT with FP. We enhance the alignment of INET simulations with authentic hardware behaviors by modifying INET modules. We modify the INET gPTP synchronization model and the INET simulation models for the SF and CT forwarding latencies. Also, we modify the INET simulation modules to support the combined operation of CT and FP. We demonstrate how our INET modifications, which we make publicly available, accurately simulate the behaviors of real TSN hardware.

Time-sensitive networking (TSN) is a new industrial communication technology being actively promoted by the international industry. The deterministic transmission of time-triggered (TT) traffic in TSN is guaranteed by Time-aware shaper (TAS), which is defined in IEEE 802.1Qbv. However, if the TSN technology needs to be applied to the existing network environment, the deterministic transmission is difficult to achieve. This paper designs and implements a TAS to realizes deterministic transmission of TT streams in TSN. Experimental results show that the proposed TAS can achieve good shaping effects and can meet the transmission requirements of the TT streams.

With the interconnection of distributed devices from different industrial automation networks, heterogeneous traffics with different Quality of Service (QoS) requirements increase dramatically. Shapers in Time-Sensitive Networking (TSN) enable the coexistence of different industrial traffics within a single network infrastructure. In this paper, with full consideration of the time-criticality of different industrial traffics and shaping mechanisms, we propose a network calculus-based modeling scheme for the widely-used Credit Based Shaper (CBS) and Time Aware Shaper (TAS). Then, we analyze the QoS of industrial traffics with different real-time characteristics by CBS and TAS, respectively. To evaluate the accuracy of network calculus-based modeling scheme, we compare our theoretical analysis with simulations, wherein a compactness function is defined to describe QoS compactness. Simulation results verify the effectiveness of proposed modeling scheme, by which we further validate both CBS and TAS can satisfy the QoS of traffics for different industrial automation scenarios.

Time-sensitive networking (TSN) strives to provide an ultralow-latency real-time deterministic network for time-critical traffic using the time-aware shaper (TAS) mechanism. For this purpose, methods for routing and scheduling the time-critical flows must be specified. However, this is an NP-hard problem. Although several prior studies have suggested constraint programming (CP)-based approaches, these methods fail to provide a reasonable runtime due to the complexity of the problem. Motivated by this, we propose a TAS co-optimization (TACO) framework that solves the TAS scheduling and routing problem in TSN with a reasonable runtime. As an alternative to CP-based approaches, TACO considers a metaheuristic approach to co-optimize routing, scheduling order, and transmission timing. However, joint optimization through a metaheuristic algorithm is challenging due to the heterogeneous search spaces of the subproblems. Therefore, TACO carefully integrates the search spaces into a single domain and optimizes routing and TAS scheduling jointly with its heuristic algorithm. We evaluate TACO in various industrial networking scenarios to demonstrate that TACO achieves up to an 88% increase in the scheduling success rate with a good convergence rate and an overall low latency/jitter compared to other approaches.

Smart substations are an important trend in substation construction. With increasing data traffic, it is difficult for the traditional Ethernet network to meet the real-time requirements of control information in smart substations. Hence, in this paper, a deterministic network architecture for substations based on time-sensitive networks (TSN) has been developed in order to realize the domain-wide time synchronization and efficient real-time communication of the “three-layer and two-network” model in smart substations. Furthermore, a design scheme for substation automation equipment based on TSN is proposed. The proposed device realizes the timely transmission of real-time control information packets by utilizing the Earliest TxTime First (ETF) Qdisc technology of Linux and the timing sending capability of Intel 210 NIC. Furthermore, it collaborates with the time-aware shaper (TAS) traffic scheduling mechanism of TSN switches to ensure the end-to-end deterministic delay of time-sensitive traffic. As a result, it provides efficient real-time communication services with low latency and jitter for smart substation automation systems.

As new networking paradigms emerge for different networking applications, e.g., cyber-physical systems, and different services are handled under a converged data link technology, e.g., Ethernet, certain applications with mission critical traffic cannot coexist on the same physical networking infrastructure using traditional Ethernet packet-switched networking protocols. The IEEE 802.1Q Time Sensitive Networking (TSN) Task Group is developing protocol standards to provide deterministic properties, i.e., eliminates non-deterministic delays, on Ethernet based packet-switched networks. In particular, the IEEE 802.1Qcc, centralized management and control, and the IEEE 802.1Qbv, Time-Aware Shaper (TAS), can be used to manage and control Scheduled Traffic (ST) streams with periodic properties along with Best-Effort (BE) traffic on the same network infrastructure. We investigate the effects of using the IEEE 802.1Qcc management protocol to accurately and precisely configure TAS enabled switches (with transmission windows governed by Gate Control Lists (GCLs) with Gate Control Entries (GCEs)) ensuring ultra-low bounded latency, zero packet loss, and minimal jitter for ST TSN traffic. We examine both a centralized network/distributed user model (hybrid model) and a fully-distributed (decentralized) 802.1Qcc model on a typical industrial control network with the goal of maximizing the number of ST streams.

Time-Sensitive Networking (TSN) is a new technology developed from Ethernet that guarantees deterministic transmission of various types of flows, such as Time-triggered (TT) flows and Audio-video-bridging (AVB) flows, in the same network. Currently, Time-aware Shaping (TAS) and Credit-based Shaping (CBS) are widely used for scheduling hybrid flows, where the credit value in CBS is directly linked to the logical bandwidth value idleSlope , which affects the real-time performance of AVB flows. However, as the network scale increases, existing bandwidth allocation methods result in higher computation times and lower allocation success rates. In this article, the aforementioned problem is addressed by two-step: first, we design a load-balanced routing heuristic (LBRH) to improve the allocation success rate; second, we accelerate the CBS bandwidth allocation by using unified bandwidth allocation scheme, which integrates LBRH and further improves the allocation success rate. Performance evaluation in multiple test cases shows that LBRH can improve the success rate of bandwidth allocation, and the unified bandwidth allocation scheme integrating LBRH significantly reduces the overall execution time while improving the success rate of bandwidth allocation, which is more suitable for large-scale TSN networks with complex routing.

Introduction: Ethernet-based automotive networks require additional mechanisms to ensure low latency for time-sensitive streams. The Time-Sensitive Networking (TSN) task group for real-time systems has proposed several mechanisms, including the time-aware shaper (TAS), to provide real-time performance. TAS enables the setting of separate transmission time windows at output ports for different queues, thereby preventing interference from other priorities. The primary objective of this study is to determine the worst-case end-to-end delay of class-based TAS streams in vehicular networks with less conservative error, which can then be used to guide the reverse design of TAS parameters. Method: This study employs Compositional Performance Analysis (CPA) to compute the worst-- case end-to-end (E2E) delay of class-based TAS streams at the data link layer. The optimized CPA results are compared with pre-optimization calculations and simulation outcomes. Result: The optimized CPA calculation reduces the end-to-end delay by an average of 42.6% for two-hop TAS streams and 57.8% for three-hop TAS streams compared to the pre-optimization results. Discussion: Building on the existing CPA method, this study enhances E2E worst-case delay analysis and reduces conservative error. Additionally, synchronization errors and extreme operational scenarios are discussed. However, the methodology proposed in this study is only applicable to scenarios with aligned gating windows. Conclusion: All simulation results for TAS streams fall within the bounds predicted by the CPA calculation. The optimized CPA analysis of the worst-case end-to-end delay greatly reduces conservative error. It can be used to validate the appropriateness of the class-based gate control parameter configurations.

In order to improve the real-time performance of Industrial Internet, this paper proposes a network communication delay optimization scheme that based on the IEEE 802.1Qbv protocol of time sensitive network (TSN). The scheme distinguishes the network data types with different time delay requirements, and proposes a TAS-EWRR scheduling algorithm in the data link layer of OSI model. The algorithm combines with time aware shaper (TAS), stream reservation protocol (SRP), frame preemption mechanism and enhanced weighted round robin (EWRR) algorithm. At the same time, a shortest path algorithm based on delay is combined at the network layer to realize the optimization of the delay of the entire network.KeywordsIndustrial internetDelayTSNTASShortest path

This paper addresses Wi-Fi 6 time-aware scheduling based on Target Wake Time (TWT) in a way that is compatible with the Time Sensitive Networking (TSN) Time-aware Shaper (TAS). The paper proposes novel mechanisms and describes a proof-of-concept implementation. The implemented solution has been evaluated in terms of latency and jitter in a testbed with operational Wi-Fi 6 equipment. Results achieved in terms of latency and jitter show that our proposal provides a way to isolate critical traffic from other types of traffic in an effective and flexible way.

The audio-video bridging (AVB) technology has been standardized by IEEE to deliver high-quality audio/video in real time over an Ethernet network. The IEEE AVB Ethernet standard includes protocols to synchronize time, set up standards for stream reservation, and schedule standards for forwarding and queuing, among others. However, AVB is difficult to apply to industrial networks such as industrial automation and automobiles due to lack of consideration for control data that must ensure transmission time. To solve this issue, IEEE proposes the 802.1 time-sensitive network standard, and various studies are being conducted with regard to related applications. In this study, based on the structure of the existing IEEE 802.1Qav protocol, the time-determined forwarding and queuing functions designed using the time-aware shaper, priority queuing, and credit-based shaper algorithms are described. TC275 (Infineon) was used for functional implementation, and VN5620 (Vector) was used for data monitoring. Through the experimental process in the simulation environment, it was confirmed that the TAS algorithm transmits control data at intervals of 200ms and 500ms.

The explosion of Internet traffic has brought about an acute need for high-performance networks. The bandwidth available on a single fiber has increased dramatically by the wavelength division multiplexing (WDM) technologies. How to use the huge bandwidth flexibly and efficiently is one of the hot topics of optical networks. It is high time that the high-performance switches/routers should be designed. All-optical switching network is a networking platform with effective and agile utilization of the available optical bandwidth. Some promising optical switching networks, such as optical packet switched, optical burst switched, and optical label switched networks are proposed. The benefit of these networks compared to the existing optical WDM networks rises from the higher network utilization at sub-wavelength granularity and from the supporting of more various services. However, there are still a lot of challenges. One challenge of them is contention. Due to the fact that the viable optical random access memory is not available in the optical domain so far, there exists a real possibility that packets may contend with one another at a switching node. In this paper, a novel node architecture called packet calking switch is proposed for all-optical switching networks. The proposed architecture is accompanied by a signaling protocol for packet-based traffic handling. This proposed node architecture is introduced into a simple network and a mesh network through simulation. The simulation results show that it is suitable for prioritized packet transmission. And it is more cost-effective than the existing node architectures because it requires much smaller optical switches and wavelength conversion to achieve nearly the same packet drop performance as the node configured partial wavelength conversion.

Fault-tolerant bandwidth reservation strategies for data transfers in high-performance networks

A novel all-optical self-routed wavelength-addressable network based on a new multiwavelength routing protocol is proposed. A distributed switching network that uses a low-speed routing header provides a transparent path for the high-speed data while utilizing low-speed electronic processing of the routing header. Each data packet is preceded by a routing header composed of a serial combination of wavelengths. The number of destination addresses is dramatically increased over conventional wavelength-division multiplexing or conventional photonic packet switching networks for the same number of wavelengths or header digits, respectively. A 1/spl times/4 switching node is implemented demonstrating the switching and transmission capabilities of this wavelength-addressable network. >

At a switching node in an optical packet switching (OPS) network, packet contention occurs whenever two or more packets try to reach the same output port of the node at the same wavelength, consequently it degrades network performance. Previous works on optical packet switching flourishingly adopted optical buffering with optical fibre delay line (FDL), wavelength conversion, or deflection routing to resolve packet contention. In this paper, we focus on the optical fibre delay line approach, especially the selection of proper length of FDL under asynchronous variable length packet traffic. As the length of fibre coils equipped in a FDL optical buffering system is impossible to be reconfigured frequently, a proper length of FDL should be determined during manufacture. The motivation is to observe the impact factors on FDL optical system performance in a WDM network scenario, and provide the empirical data as supports to select the proper length of FDL in an OPS node system.