The Experts below are selected from a list of 2763 Experts worldwide ranked by ideXlab platform
Christian Fraboul - One of the best experts on this subject based on the ideXlab platform.
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wctt analysis of avionics Switched Ethernet network with wrr scheduling
Real-Time Networks and Systems, 2018Co-Authors: Aakash Soni, Jean-luc Scharbarg, Christian FraboulAbstract:Nowadays, a real-time embedded system often has to cope with flows with different criticality levels. Such a situation is forecasted for next generation avionics networks, in order to better use communication resources. Indeed, the present situation, where the Avionics Full Duplex Switched Ethernet (AFDX) network is reserved for critical avionics flows, leads to a very lightly loaded network. Quality of Service (QoS) mechanisms such as service disciplines are mandatory in order to cope with the heterogeneous constraints of the different kinds of flows. Weighted Round Robin (WRR) is envisioned in the context of avionics. Worst-case traversal time (WCTT) analysis is mandatory to ensure that temporal constraints of flows are met. Network Calculus (NC) is a popular solution for this analysis and results exist for WRR. They lead to pessimistic upper bounds. The main contribution of this paper is to show how existing NC results for WRR can be applied and improved in the context of an avionics configuration. The resulting analysis is evaluated on an industrial size configuration.
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Integrating Offset in Worst Case Delay Analysis of Switched Ethernet Network With Deficit Round Robbin
2018Co-Authors: Aakash Soni, Jean-luc Scharbarg, Christian FraboulAbstract:In order to handle mixed criticality flows in a realtime embedded network, Switched Ethernet with Quality of Service (QoS) facilities has become a popular solution. Deficit Round Robin (DRR) is such a QoS facility. Worst-Case Traversal Time (WCTT) analysis is mandatory for such systems, in order to ensure that end-to-end delay constraints are met. Network Calculus is a classical approach to achieve this WCTT analysis. A solution has been proposed for Switched Ethernet with DRR. It computes pessimistic upper bounds on end-to-end latencies. This pessimism is partly due to the fact that the scheduling of flows by end systems is not considered in the analysis. This scheduling can be modeled by offsets between flows. This modeling has been integrated in WCTT analysis of Switched Ethernet with First In First Out (FIFO) scheduling. It leads to a significant reduction of delay upper bounds. The contribution of this paper is to integrate the offsets in the WCTT analysis for Switched Ethernet with DRR and to evaluate the reduction on delay upper bounds, considering a realistic case study.
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Optimizing Network Calculus for Switched Ethernet Network with Deficit Round Robin
2018 IEEE Real-Time Systems Symposium (RTSS), 2018Co-Authors: Aakash Soni, Jean-luc Scharbarg, Christian FraboulAbstract:Avionics Full Duplex Switched Ethernet (AFDX) is the de facto standard for the transmission of critical avionics flows. It is a specific Switched Ethernet solution based on First-in First-out (FIFO) scheduling. Worst-case traversal time (WCTT) analysis is mandatory for such flows, since timing constraints have to be guaranteed. A classical approach in this context is Network Calculus (NC). However, NC introduces some pessimism in the WCTT computation. Moreover, the worst-case often corresponds to very rare scenarios. Thus, the network architecture is most of the time lightly loaded. Typically, less than 10 % of the available bandwidth is used for the transmission of avionics lows on an AFDX network embedded in an aircraft. One solution to improve the utilization of the network is to introduce Quality of Service (QoS) mechanisms. Deficit Round Robin (DRR) is such a mechanism and it is envisioned for future avionics networks. A WCTT analysis has been proposed for DRR. It is based on NC. It doesn't make any assumption on the scheduling of flows by end systems. The first contribution of this paper is to identify sources of pessimism of this approach and to propose an improved solution which removes part of this pessimism. The second contribution is to show how the scheduling of flows can be integrated in this optimized DRR approach, thanks to offsets. An evaluation on a realistic case study shows that both contributions bring significantly tighter bounds on worst-case latencies.
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partially synchronizing periodic flows with offsets improves worst case end to end delay analysis of Switched Ethernet
Leveraging Applications of Formal Methods, 2010Co-Authors: Jean-luc Scharbarg, Christian FraboulAbstract:A Switched Ethernet network needs a worst-case delay analysis to prove that real-time applications can be correctly implemented on it. Existing approaches for upper bounding end-to-end delay assume that there is either no-synchronization or a global synchronization of flows which needs a global clock. Conversely, flows emitted by the same end-system can be easily synchronized using the existing local clock. This paper explains how the partial synchronization of periodic flows can be integrated in the worst-case delay analysis provided by Network Calculus approach. End-to-end delays computed on Switched Ethernet configurations show that the proposed method clearly reduces the upper bounds of end-to-end delay.
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performance analysis of a master slave Switched Ethernet for military embedded applications
IEEE Transactions on Industrial Informatics, 2010Co-Authors: Ahlem Mifdaoui, Fabrice Frances, Christian FraboulAbstract:Current military communication network is a generation old and is no longer effective in meeting the emerging requirements imposed by the next-generation military embedded applications. A new communication network based upon Full Duplex Switched Ethernet is proposed in this paper to overcome these limitations. To allow existing military subsystems to be easily supported by a Switched Ethernet network, our proposal consists in keeping their current centralized communication scheme by using an optimized master/slave transmission control on Switched Ethernet thanks to the Flexible Time Triggered (FTT) paradigm. Our main objective is to assess the performance of such a proposal and estimate the quality-of-service we can expect in terms of latency. Using the Network Calculus formalism, schedulability analysis are determined. These analysis are illustrated in the case of a realistic military embedded application extracted from a real military aircraft network, to highlight the proposal's ability to support the required time constrained communications.
Jean-luc Scharbarg - One of the best experts on this subject based on the ideXlab platform.
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wctt analysis of avionics Switched Ethernet network with wrr scheduling
Real-Time Networks and Systems, 2018Co-Authors: Aakash Soni, Jean-luc Scharbarg, Christian FraboulAbstract:Nowadays, a real-time embedded system often has to cope with flows with different criticality levels. Such a situation is forecasted for next generation avionics networks, in order to better use communication resources. Indeed, the present situation, where the Avionics Full Duplex Switched Ethernet (AFDX) network is reserved for critical avionics flows, leads to a very lightly loaded network. Quality of Service (QoS) mechanisms such as service disciplines are mandatory in order to cope with the heterogeneous constraints of the different kinds of flows. Weighted Round Robin (WRR) is envisioned in the context of avionics. Worst-case traversal time (WCTT) analysis is mandatory to ensure that temporal constraints of flows are met. Network Calculus (NC) is a popular solution for this analysis and results exist for WRR. They lead to pessimistic upper bounds. The main contribution of this paper is to show how existing NC results for WRR can be applied and improved in the context of an avionics configuration. The resulting analysis is evaluated on an industrial size configuration.
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Integrating Offset in Worst Case Delay Analysis of Switched Ethernet Network With Deficit Round Robbin
2018Co-Authors: Aakash Soni, Jean-luc Scharbarg, Christian FraboulAbstract:In order to handle mixed criticality flows in a realtime embedded network, Switched Ethernet with Quality of Service (QoS) facilities has become a popular solution. Deficit Round Robin (DRR) is such a QoS facility. Worst-Case Traversal Time (WCTT) analysis is mandatory for such systems, in order to ensure that end-to-end delay constraints are met. Network Calculus is a classical approach to achieve this WCTT analysis. A solution has been proposed for Switched Ethernet with DRR. It computes pessimistic upper bounds on end-to-end latencies. This pessimism is partly due to the fact that the scheduling of flows by end systems is not considered in the analysis. This scheduling can be modeled by offsets between flows. This modeling has been integrated in WCTT analysis of Switched Ethernet with First In First Out (FIFO) scheduling. It leads to a significant reduction of delay upper bounds. The contribution of this paper is to integrate the offsets in the WCTT analysis for Switched Ethernet with DRR and to evaluate the reduction on delay upper bounds, considering a realistic case study.
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Optimizing Network Calculus for Switched Ethernet Network with Deficit Round Robin
2018 IEEE Real-Time Systems Symposium (RTSS), 2018Co-Authors: Aakash Soni, Jean-luc Scharbarg, Christian FraboulAbstract:Avionics Full Duplex Switched Ethernet (AFDX) is the de facto standard for the transmission of critical avionics flows. It is a specific Switched Ethernet solution based on First-in First-out (FIFO) scheduling. Worst-case traversal time (WCTT) analysis is mandatory for such flows, since timing constraints have to be guaranteed. A classical approach in this context is Network Calculus (NC). However, NC introduces some pessimism in the WCTT computation. Moreover, the worst-case often corresponds to very rare scenarios. Thus, the network architecture is most of the time lightly loaded. Typically, less than 10 % of the available bandwidth is used for the transmission of avionics lows on an AFDX network embedded in an aircraft. One solution to improve the utilization of the network is to introduce Quality of Service (QoS) mechanisms. Deficit Round Robin (DRR) is such a mechanism and it is envisioned for future avionics networks. A WCTT analysis has been proposed for DRR. It is based on NC. It doesn't make any assumption on the scheduling of flows by end systems. The first contribution of this paper is to identify sources of pessimism of this approach and to propose an improved solution which removes part of this pessimism. The second contribution is to show how the scheduling of flows can be integrated in this optimized DRR approach, thanks to offsets. An evaluation on a realistic case study shows that both contributions bring significantly tighter bounds on worst-case latencies.
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Work in progress paper: pessimism analysis of network calculus approach on AFDX networks
2017Co-Authors: Aakash Soni, Jean-luc ScharbargAbstract:Worst-case delay analysis of real-time networks is mandatory, since distributed real-time applications require bounded end-to-end delays. Switched Ethernet technologies have become popular solutions in the context of real-time systems. Several approaches, based on Network Calculus, trajectories, ..., have been proposed for the worst-case analysis of such technologies. They compute pessimistic upper bounds of end-toend delays. Since this pessimism leads to an over-dimensioning of the network, it is important to quantify the pessimism of the computed upper bounds. In this paper, we propose such a pessimism analysis, based on Network Calculus. In a first step we focus on avionics Switched Ethernet network (AFDX) with Fixed Priority/First In First Out (FP/FIFO) scheduling.
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Priority assignment on an avionics Switched Ethernet Network (QoS AFDX)
2014 10th IEEE Workshop on Factory Communication Systems (WFCS 2014), 2014Co-Authors: Tasnim Hamza, Jean-luc ScharbargAbstract:AFDX (Avionics Full Duplex Switched Ethernet) standardised as ARINC 664 is a major upgrade for avionics systems. For current aircrafts, it implements a FIFO scheduling policy and allows the transmission of sporadic flows between avionics functions distributed on a set of end systems. The certification imposes to guarantee that the end-to-end delay of any frame transmitted on the network is upper-bounded and that no frame is lost due to buffer overflow. This guarantee is obtained thanks to a worst-case analysis which is based on either network calculus or trajectory approach. However it leads to an over-dimensioning of the network. For future aircraft, it is envisioned to use a Fixed Priority scheduling policy in order to better use network resources (QoS AFDX). Existing AFDX switches implement two priority levels. A worst-case analysis of such a network exists, based on the Trajectory approach. Thus, the remaining issue is to assign efficiently the available priorities to the flows. The contribution of this paper deals with this issue. It proposes to assign the priorities to the flows using the well-know Optimal Priority Assignment algorithm (OPA) which was first defined for monoprocessor preemptive systems. The proposed solution is applied on two case studies. The overall worst-case delay is reduced by 30 % on a small configuration and 20 % on a realistic one.
Aakash Soni - One of the best experts on this subject based on the ideXlab platform.
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wctt analysis of avionics Switched Ethernet network with wrr scheduling
Real-Time Networks and Systems, 2018Co-Authors: Aakash Soni, Jean-luc Scharbarg, Christian FraboulAbstract:Nowadays, a real-time embedded system often has to cope with flows with different criticality levels. Such a situation is forecasted for next generation avionics networks, in order to better use communication resources. Indeed, the present situation, where the Avionics Full Duplex Switched Ethernet (AFDX) network is reserved for critical avionics flows, leads to a very lightly loaded network. Quality of Service (QoS) mechanisms such as service disciplines are mandatory in order to cope with the heterogeneous constraints of the different kinds of flows. Weighted Round Robin (WRR) is envisioned in the context of avionics. Worst-case traversal time (WCTT) analysis is mandatory to ensure that temporal constraints of flows are met. Network Calculus (NC) is a popular solution for this analysis and results exist for WRR. They lead to pessimistic upper bounds. The main contribution of this paper is to show how existing NC results for WRR can be applied and improved in the context of an avionics configuration. The resulting analysis is evaluated on an industrial size configuration.
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Integrating Offset in Worst Case Delay Analysis of Switched Ethernet Network With Deficit Round Robbin
2018Co-Authors: Aakash Soni, Jean-luc Scharbarg, Christian FraboulAbstract:In order to handle mixed criticality flows in a realtime embedded network, Switched Ethernet with Quality of Service (QoS) facilities has become a popular solution. Deficit Round Robin (DRR) is such a QoS facility. Worst-Case Traversal Time (WCTT) analysis is mandatory for such systems, in order to ensure that end-to-end delay constraints are met. Network Calculus is a classical approach to achieve this WCTT analysis. A solution has been proposed for Switched Ethernet with DRR. It computes pessimistic upper bounds on end-to-end latencies. This pessimism is partly due to the fact that the scheduling of flows by end systems is not considered in the analysis. This scheduling can be modeled by offsets between flows. This modeling has been integrated in WCTT analysis of Switched Ethernet with First In First Out (FIFO) scheduling. It leads to a significant reduction of delay upper bounds. The contribution of this paper is to integrate the offsets in the WCTT analysis for Switched Ethernet with DRR and to evaluate the reduction on delay upper bounds, considering a realistic case study.
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Optimizing Network Calculus for Switched Ethernet Network with Deficit Round Robin
2018 IEEE Real-Time Systems Symposium (RTSS), 2018Co-Authors: Aakash Soni, Jean-luc Scharbarg, Christian FraboulAbstract:Avionics Full Duplex Switched Ethernet (AFDX) is the de facto standard for the transmission of critical avionics flows. It is a specific Switched Ethernet solution based on First-in First-out (FIFO) scheduling. Worst-case traversal time (WCTT) analysis is mandatory for such flows, since timing constraints have to be guaranteed. A classical approach in this context is Network Calculus (NC). However, NC introduces some pessimism in the WCTT computation. Moreover, the worst-case often corresponds to very rare scenarios. Thus, the network architecture is most of the time lightly loaded. Typically, less than 10 % of the available bandwidth is used for the transmission of avionics lows on an AFDX network embedded in an aircraft. One solution to improve the utilization of the network is to introduce Quality of Service (QoS) mechanisms. Deficit Round Robin (DRR) is such a mechanism and it is envisioned for future avionics networks. A WCTT analysis has been proposed for DRR. It is based on NC. It doesn't make any assumption on the scheduling of flows by end systems. The first contribution of this paper is to identify sources of pessimism of this approach and to propose an improved solution which removes part of this pessimism. The second contribution is to show how the scheduling of flows can be integrated in this optimized DRR approach, thanks to offsets. An evaluation on a realistic case study shows that both contributions bring significantly tighter bounds on worst-case latencies.
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Work in progress paper: pessimism analysis of network calculus approach on AFDX networks
2017Co-Authors: Aakash Soni, Jean-luc ScharbargAbstract:Worst-case delay analysis of real-time networks is mandatory, since distributed real-time applications require bounded end-to-end delays. Switched Ethernet technologies have become popular solutions in the context of real-time systems. Several approaches, based on Network Calculus, trajectories, ..., have been proposed for the worst-case analysis of such technologies. They compute pessimistic upper bounds of end-toend delays. Since this pessimism leads to an over-dimensioning of the network, it is important to quantify the pessimism of the computed upper bounds. In this paper, we propose such a pessimism analysis, based on Network Calculus. In a first step we focus on avionics Switched Ethernet network (AFDX) with Fixed Priority/First In First Out (FP/FIFO) scheduling.
Eric Rondeau - One of the best experts on this subject based on the ideXlab platform.
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Network calculus based FDI approach for Switched Ethernet architecture
2006Co-Authors: Belynda Brahimi, Christophe Aubrun, Eric RondeauAbstract:The Networked Control Systems (NCS) are complex systems which integrate information provided by several domians such as automatic control, computer science, communication network. The work presented in this paper concerns fault detection, isolation and compensation of communication network. The proposed method is based on the classical approach of Fault Detection and Isolation and Fault Tolerant Control (FDI/FTC) currently used in diagnosis. The modelling of the network to be supervised is based on both couloured petri nets and network calculus theory often used to represent and analyse the network behaviour. The goal is to implement inside network devices algorithms enabling to detect, isolate and compensate communication faults in an autonomous way.
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confronting the performances of a Switched Ethernet network with industrial constraints by using the network calculus
International Journal of Communication Systems, 2005Co-Authors: Jeanphilippe Georges, Thierry Divoux, Eric RondeauAbstract:The Ethernet network is more and more used to interconnect industrial devices. The objective of this paper is to study the performances of such a network to support real-time communications. For this, first we propose a general representation to model a Switched Ethernet network by using a sequence of elementary components such as buffers, multiplexers, etc. Second, we aggregate the individual temporal properties of each component given in the Cruz' survey to obtain a global formula enabling one to calculate the maximum end-to-end delay for any industrial communication scenarios. Finally, we deduce the limits of the Switched Ethernet network regarding the number of input/output cards connected to the network and to the sizes of periodic and aperiodic messages. Copyright © 2005 John Wiley & Sons, Ltd.
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Confronting the performances of a Switched Ethernet network with industrial constraints by using the network calculus: Research Articles
International Journal of Communication Systems, 2005Co-Authors: Jeanphilippe Georges, Thierry Divoux, Eric RondeauAbstract:The Ethernet network is more and more used to interconnect industrial devices. The objective of this paper is to study the performances of such a network to support real-time communications. For this, first we propose a general representation to model a Switched Ethernet network by using a sequence of elementary components such as buffers, multiplexers, etc. Second, we aggregate the individual temporal properties of each component given in the Cruz' survey to obtain a global formula enabling one to calculate the maximum end-to-end delay for any industrial communication scenarios. Finally, we deduce the limits of the Switched Ethernet network regarding the number of input/output cards connected to the network and to the sizes of periodic and aperiodic messages. Copyright © 2005 John Wiley & Sons, Ltd.
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strict priority versus weighted fair queueing in Switched Ethernet networks for time critical applications
International Parallel and Distributed Processing Symposium, 2005Co-Authors: Jeanphilippe Georges, Thierry Divoux, Eric RondeauAbstract:In an industrial or technical context, some of the communications are strongly time-constrained. Our objective is to evaluate the service offered by a Switched Ethernet architecture. We have chosen the network calculus theory because it gives a good representation of the exchanges and enables to determine the maximum end to end delays. Previous models implementing a strict priority policy presented in (J. -P. Georges et al., 2004) are improved in order to take into account the weighted fair queueing mechanism, which enables to balance the allocation of the network to the different traffics regarding the time contraints they have to respect. This paper also presents the new analytical formulas which upper bound the maximum end-to-end delays of the time-critical messages over the whole network. This enables to determine the optimal bandwith dedicated to both critical and best effort traffics. On an industrial scenario, strict priority and weighted fair queueing policies are finally compared.
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strict priority versus weighted fair queueing in Switched Ethernet networks for time critical applications
International Parallel and Distributed Processing Symposium, 2005Co-Authors: Jeanphilippe Georges, Thierry Divoux, Eric RondeauAbstract:In an industrial or technical context, some of the communications are strongly time-constrained. Our objective is to evaluate the service offered by a Switched Ethernet architecture. We have chosen the network calculus theory because it gives a good representation of the exchanges and enables to determine the maximum end to end delays. Previous models implementing a strict priority policy presented in (J. -P. Georges et al., 2004) are improved in order to take into account the weighted fair queueing mechanism, which enables to balance the allocation of the network to the different traffics regarding the time contraints they have to respect. This paper also presents the new analytical formulas which upper bound the maximum end-to-end delays of the time-critical messages over the whole network. This enables to determine the optimal bandwith dedicated to both critical and best effort traffics. On an industrial scenario, strict priority and weighted fair queueing policies are finally compared.
Soheil Samii - One of the best experts on this subject based on the ideXlab platform.
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design optimization of frame preemption in real time Switched Ethernet
Design Automation and Test in Europe, 2019Co-Authors: Taeju Park, Soheil Samii, Kang G ShinAbstract:Switched Ethernet has been, and will also be increasingly common in current and future real-time and embedded systems. The IEEE 802.1 working group has recently developed standards and technologies, commonly referred to as Time-Sensitive Networking (TSN), to enhance Switched Ethernet with timeliness and dependability. We address, for the first time, the synthesis problem for the TSN frame preemption standards IEEE 802.3br-2016 and 802.1Qbu-2016 by introducing two new configuration parameters: flow to queue and queue to Express/Preemptable MAC interface assignments. We present an optimization framework to determine these configuration parameters with reliability as the optimization goal. Our proposed framework is shown to outperform commonly used priority-assignment as well as intuitive approaches.
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Synthesis of Queue and Priority Assignment for Asynchronous Traffic Shaping in Switched Ethernet
2017 IEEE Real-Time Systems Symposium (RTSS), 2017Co-Authors: Johannes Specht, Soheil SamiiAbstract:Real-time Switched Ethernet communication is of increasing importance in many cyber-physical and embedded systems application areas such as automotive electronics, avionics, and industrial control. The IEEE 802.1 Time-Sensitive Networking (TSN) task group develops standards for real-time Ethernet, for example a time-triggered traffic class (IEEE 802.1Qbv-2015). New application areas, such as active safety and autonomous driving using radar, lidar, and camera sensors, which do not fall into the strictly periodic, time-triggered communication model, require a flexible traffic class that can accommodate various communication models while still providing hard real-time guarantees. In our previous work, we developed such a traffic class, Urgency-Based Scheduler (UBS), and its worst-case latency analysis. UBS is currently under standardization (P802.1Qcr) in the TSN task group. In this paper, we introduce and solve the UBS synthesis problem of assigning hard real-time data flows to queues and priorities to queues, the main parameters that determine communication latencies. The synthesis problem is particularly challenging due to the flexibility offered by UBS to aggregate flows and assign individual priority levels per network hop. We present an SMT approach, a cluster-based heuristic, and an extensive experimental evaluation.
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urgency based scheduler for time sensitive Switched Ethernet networks
Euromicro Conference on Real-Time Systems, 2016Co-Authors: Johannes Specht, Soheil SamiiAbstract:Due to increasing bandwidth requirements, Ethernet technology is emerging in embedded systems application areas such as automotive, avionics, and industrial control. In the automotive domain, Ethernet enables integration of cameras, radars, and fusion to build active safety and automated driving systems. While Ethernet provides the necessary communication bandwidth, solutions are needed to satisfy stringent dependability and temporal requirements of such safety-critical systems. This paper introduces an asynchronous traffic scheduling algorithm, which gives low delay guarantees in a Switched Ethernet network, while maintaining a low implementation complexity. We present a timing analysis and demonstrate the tightness of the delay bounds by extensive simulation experiments.
