49 research outputs found

    Analyse pire cas exact du réseau AFDX

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    L'objectif principal de cette thĂšse est de proposer les mĂ©thodes permettant d'obtenir le dĂ©lai de transmission de bout en bout pire cas exact d'un rĂ©seau AFDX. Actuellement, seules des bornes supĂ©rieures pessimistes peuvent ĂȘtre calculĂ©es en utilisant les approches de type Calcul RĂ©seau ou par Trajectoires. Pour cet objectif, diffĂ©rentes approches et outils existent et ont Ă©tĂ© analysĂ©es dans le contexte de cette thĂšse. Cette analyse a mis en Ă©vidence le besoin de nouvelles approches. Dans un premier temps, la vĂ©rification de modĂšle a Ă©tĂ© explorĂ©e. Les automates temporisĂ©s et les outils de verification ayant fait leur preuve dans le domaine temps rĂ©el ont Ă©tĂ© utilisĂ©s. Ensuite, une technique de simulation exhaustive a Ă©tĂ© utilisĂ©e pour obtenir les dĂ©lais de communication pire cas exacts. Pour ce faire, des mĂ©thodes de rĂ©duction de sĂ©quences ont Ă©tĂ© dĂ©finies et un outil a Ă©tĂ© dĂ©veloppĂ©. Ces mĂ©thodes ont Ă©tĂ© appliquĂ©es Ă  une configuration rĂ©elle du rĂ©seau AFDX, nous permettant ainsi de valider notre travail sur une configuration de taille industrielle du rĂ©seau AFDX telle que celle embarquĂ©e Ă  bord des avions Airbus A380. The main objective of this thesis is to provide methodologies for finding exact worst case end to end communication delays of AFDX network. Presently, only pessimistic upper bounds of these delays can be calculated by using Network Calculus and Trajectory approach. To achieve this goal, different existing tools and approaches have been analyzed in the context of this thesis. Based on this analysis, it is deemed necessary to develop new approaches and algorithms. First, Model checking with existing well established real time model checking tools are explored, using timed automata. Then, exhaustive simulation technique is used with newly developed algorithms and their software implementation in order to find exact worst case communication delays of AFDX network. All this research work has been applied on real life implementation of AFDX network, allowing us to validate our research work on industrial scale configuration of AFDX network such as used on Airbus A380 aircraft. ABSTRACT : The main objective of this thesis is to provide methodologies for finding exact worst case end to end communication delays of AFDX network. Presently, only pessimistic upper bounds of these delays can be calculated by using Network Calculus and Trajectory approach. To achieve this goal, different existing tools and approaches have been analyzed in the context of this thesis. Based on this analysis, it is deemed necessary to develop new approaches and algorithms. First, Model checking with existing well established real time model checking tools are explored, using timed automata. Then, exhaustive simulation technique is used with newly developed algorithms and their software implementation in order to find exact worst case communication delays of AFDX network. All this research work has been applied on real life implementation of AFDX network, allowing us to validate our research work on industrial scale configuration of AFDX network such as used on Airbus A380 aircraft

    Modeling a spacewire architecture using timed automata to compute worst-case end-to-end delays

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    International audienceSpacewire is a real-time communication network for use onboard satellites. It has been designed to transmit both payload and control/command data. To guarantee that communications respect the real-time constraints, designers use tools to compute the worst-case end-to-end delays. Among these tools, recursive flow analysis and Network Calculus approaches have been studied. This paper proposes to use the model-checking approach based on timed automata. A case study based on an industrial one is shown. Our approach is compared with recursive flow analysis and Network Calculus

    A Compositional Approach for Schedulability Analysis of Distributed Avionics Systems

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    This work presents a compositional approach for schedulability analysis of Distributed Integrated Modular Avionics (DIMA) systems that consist of spatially distributed ARINC-653 modules connected by a unified AFDX network. We model a DIMA system as a set of stopwatch automata in UPPAAL to verify its schedulability by model checking. However, direct model checking is infeasible due to the large state space. Therefore, we introduce the compositional analysis that checks each partition including its communication environment individually. Based on a notion of message interfaces, a number of message sender automata are built to model the environment for a partition. We define a timed selection simulation relation, which supports the construction of composite message interfaces. By using assume-guarantee reasoning, we ensure that each task meets the deadline and that communication constraints are also fulfilled globally. The approach is applied to the analysis of a concrete DIMA system.Comment: In Proceedings MeTRiD 2018, arXiv:1806.09330. arXiv admin note: text overlap with arXiv:1803.1105

    Computing the exact worst-case End-to-end delays in a Spacewire network using Timed Automata

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    National audienceSpacewire is a real-time communication network for use onboard satellites. It has been designed to transmit both payload and control/command data. To guarantee that communications respect the real-time constraints, designers use tools to compute the worst-case end-to-end delays. Among these tools, recursive flow analysis and Network Calculus approaches have been studied. This paper proposes to use the model-checking approach based on timed automata to compute the exact worstcase end-to-end delays and two case studies are presented

    Schedulability Analysis of Distributed Multi-core Avionics Systems with UPPAAL

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    Exact worst-case communication delay analysis of AFDX network

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    The main objective of this thesis is to provide methodologies for finding exact worst case end to end communication delays of AFDX network. Presently, only pessimistic upper bounds of these delays can be calculated by using Network Calculus and Trajectory approach. To achieve this goal, different existing tools and approaches have been analyzed in the context of this thesis. Based on this analysis, it is deemed necessary to develop new approaches and algorithms. First, Model checking with existing well established real time model checking tools are explored, using timed automata. Then, exhaustive simulation technique is used with newly developed algorithms and their software implementation in order to find exact worst case communication delays of AFDX network. All this research work has been applied on real life implementation of AFDX network, allowing us to validate our research work on industrial scale configuration of AFDX network such as used on Airbus A380 aircraft

    Network Latency and Packet Delay Variation in Cyber-physical Systems

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    The problem addressed in this paper is the limitation imposed by network elements, especially Ethernet elements, on the real-time performance of time-critical systems. Most current network elements are concerned only with data integrity, connection, and throughput with no mechanism for enforcing temporal semantics. Existing safety-critical applications and other applications in industry require varying degrees of control over system-wide temporal semantics. In addition, there are emerging commercial applications that require or will benefit from tighter enforcement of temporal semantics in network elements than is currently possible. This paper examines these applications and requirements and suggests possible approaches to imposing temporal semantics on networks. Model-based design and simulation is used to evaluate the effects of network limitations on time-critical systems

    Ethernet-based AFDX simulation and time delay analysis

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    Nowadays, new civilian aircraft have applied new technology and the amount of embedded systems and functions raised. Traditional avionics data buses design can‘t meet the new transmission requirements regarding weight and complexity due to the number of needed buses. On the other hand, Avionics Full Duplex Switched Ethernet (AFDX) with sufficient bandwidth and guaranteed services is considered as the next generation of avionics data bus. One of the important issues in Avionics Full Duplex Switched Ethernet is to ensure the data total time delay to meet the requirements of the safety-critical systems on aircraft such as flight control system. This research aims at developing an AFDX time delay model which can be used to analyse the total time delay of the AFDX network. By applying network calculus approach, both (σ,ρ) model and Generic Cell Rate Algorithm (GCRA) model are introduced. For tighter time-delay result, GCRA model is applied. Meanwhile, the current AFDX network simulation platform, FACADE, will be enhanced by adding new functions. Moreover, avionics application simulation modules are developed to exchange data with FACADE. The total time delay analysis will be performed on the improved FACADE to validate this AFDX network simulation platform in several scenarios. Moreover, each scenario is appropriated to study the association between total time delay performance and individual variable. The results from updated FACADE reflect the correlation between total time delay and certain variables. Larger BAG and more switches between source and destination end systems introduce larger total time delay while Lmax could also affect the total time delay. However, the results illustrate that the total time delays from updated FACADE are much larger than GCRA time delay model which could up to 10 times which indicates that this updated FACADE needs further improvement

    Differentiable Programming & Network Calculus: Configuration Synthesis under Delay Constraints

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    With the advent of standards for deterministic network behavior, synthesizing network designs under delay constraints becomes the natural next task to tackle. Network Calculus (NC) has become a key method for validating industrial networks, as it computes formally verified end-to-end delay bounds. However, analyses from the NC framework have been designed to bound the delay of one flow at a time. Attempts to use classical analyses to derive a network configuration have shown that this approach is poorly suited to practical use cases. Consider finding a delay-optimal routing configuration: one model had to be created for each routing alternative, then each flow delay had to be bounded, and then the bounds had to be compared to the given constraints. To overcome this three-step process, we introduce Differential Network Calculus. We extend NC to allow the differentiation of delay bounds w.r.t. to a wide range of network parameters - such as flow paths or priority. This opens up NC to a class of efficient nonlinear optimization techniques that exploit the gradient of the delay bound. Our numerical evaluation on the routing and priority assignment problem shows that our novel method can synthesize flow paths and priorities in a matter of seconds, outperforming existing methods by several orders of magnitude
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