Priority assignment on an avionics switched Ethernet network (QoS AFDX)

International audienceAFDX (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

Ethernet - a survey on its fields of application

During the last decades, Ethernet progressively became the most widely used local area networking (LAN) technology. Apart from LAN installations, Ethernet became also attractive for many other fields of application, ranging from industry to avionics, telecommunication, and multimedia. The expanded application of this technology is mainly due to its significant assets like reduced cost, backward-compatibility, flexibility, and expandability. However, this new trend raises some problems concerning the services of the protocol and the requirements for each application. Therefore, specific adaptations prove essential to integrate this communication technology in each field of application. Our primary objective is to show how Ethernet has been enhanced to comply with the specific requirements of several application fields, particularly in transport, embedded and multimedia contexts. The paper first describes the common Ethernet LAN technology and highlights its main features. It reviews the most important specific Ethernet versions with respect to each application field’s requirements. Finally, we compare these different fields of application and we particularly focus on the fundamental concepts and the quality of service capabilities of each proposal

QoS-aware AFDX: Benefits of an efficient priority assignment for avionics flows

International audienceAFDX (Avionics Full Duplex Switched Ethernet) standardised as ARINC 664 is a major upgrade for avionics systems. The certification imposes to guarantee that the end-toend delay of any frame transmitted on the network is upperbounded and that no frame is lost due to buffer overflow. This guarantee is obtained thanks to a worst-case analysis assuming a FIFO scheduling policy of flows on each output port. For future aircraft, it is envisioned to modify AFDX switch and to use a Fixed Priority scheduling policy of flows (QoS AFDX using IEEE 802.p mechanisms). A worst-case analysis of such a network has been proposed, based on the Trajectory approach. But the remaining issue is to efficiently assign available priorities to the avionics flows inside the network without modifying the application knowledge. The objective is then to minimise overall the worst case end to end delay of flows and consequently to minimise needed buffer size at switch level. The main contribution of this paper deals with the assignment of priorities to the flows using the well-know Optimal Priority Assignment algorithm (OPA) which was first defined for monoprocessor preemptive systems. The schedulability test is then based on the worst case delay analysis of each flow allocated on the AFDX QoS network computed by the trajectory approach. The proposed mechanisms have been applied on an industrial AFDX case study using two priority levels and the overall worstcase delay could be reduced by 20 %

QoS-aware AFDX: Benefits of an efficient priority assignment for avionics flows

AFDX (Avionics Full Duplex Switched Ethernet) standardised as ARINC 664 is a major upgrade for avionics systems. The certification imposes to guarantee that the end-toend delay of any frame transmitted on the network is upperbounded and that no frame is lost due to buffer overflow. This guarantee is obtained thanks to a worst-case analysis assuming a FIFO scheduling policy of flows on each output port. For future aircraft, it is envisioned to modify AFDX switch and to use a Fixed Priority scheduling policy of flows (QoS AFDX using IEEE 802.p mechanisms). A worst-case analysis of such a network has been proposed, based on the Trajectory approach. But the remaining issue is to efficiently assign available priorities to the avionics flows inside the network without modifying the application knowledge. The objective is then to minimise overall the worst case end to end delay of flows and consequently to minimise needed buffer size at switch level. The main contribution of this paper deals with the assignment of priorities to the flows using the well-know Optimal Priority Assignment algorithm (OPA) which was first defined for monoprocessor preemptive systems. The schedulability test is then based on the worst case delay analysis of each flow allocated on the AFDX QoS network computed by the trajectory approach. The proposed mechanisms have been applied on an industrial AFDX case study using two priority levels and the overall worstcase delay could be reduced by 20 %

Specification and Performance Indicators of AeroRing—A Multiple-Ring Ethernet Network for Avionics Embedded Systems

The complexity and costs of the avionics communication architecture are increasing exponentially with the increasing number of embedded computers over the last few decades. To limit the cabling complexity and the deployment costs of such a communication architecture, we specify a new Gigabit multiple-ring Ethernet network, called AeroRing, while meeting the avionics requirements. First, we describe the current Aircraft Data Communication Network (ADCN) to highlight the main characteristics and requirements that have to be fulfilled by our solution. Then, we give an overview of the most relevant solutions to improve ADCN performance and relate them to AeroRing. Afterwards, we detail the specifications and the main Performance Indicators (PIs) of AeroRing. Finally, sensitivity and validation analyses of AeroRing are conducted through a realistic avionics application, regarding the various PIs, in comparison to the backbone network of the ADCN, the Avionics Full DupleX Switched Ethernet (AFDX). The computed AeroRing performance metrics show its ability to guarantee the avionics requirements

Scheduling Rate Constrained traffic in End Systems of Time-Aware Networks

Nowadays, most of cyber-physical systems in avionics, automotive or recent Industry 4.0 domains require networked communication for mixed-critical applications. Ethernet-based networks such as AFDX, TTEthernet or TSN are capable to support transmission of both safety-critical and non-critical flows. This paper focuses on the TTEthernet network compliant with the avionics ARINC 664-P7 standard supporting time-triggered communication (TT) together with rate-constrained (RC) and best-effort (BE) traffic. Due to a global synchronization, TTcommunication with low latency and minimal jitter is ensured with static schedules computed offline. For event-triggered RC flows, bounded jitter at the source and end-to-end latency are guaranteed with worst-case analysis methods. With the increasing demands of applications, flows with Quality of Service (QoS) requirements such as video or audio may be transmitted as BE flows. However, on current configurations, no guarantees are offered to BE flows. In this paper, we aim at increasing the maximum RC utilization and improving the QoS of BE flows to allow the transmission of video or audio traffic with low jitter and end-to-end delay requirements. For this, we focus on the scheduling mechanisms and propose a scheduling approach based on a static slotted table that is applied at end systems. This table integrates the TT schedules usually obtained with Satisfiability Modulo Theories (SMT) approaches and establishes offsets of RC flows that reduce the end-to-end delay of BE flows. Several strategies for offset computations are proposed based on the distribution of flows locally at end system or globally at switch. We show that local strategies perform better than the global ones to reduce end-to-end delay of BE flows

Real-time performance analysis of a QoS based industrial embedded network

AFDX serves as a backbone network for transmission of critical avionic flows. This network is certified thanks to the WCTT analysis using Network Calculus (NC) approach. However, the pessimism introduced by NC approach often leads to an over-sized and eventually an underutilized network. The manufacturers envision to better use the available network resources by increasing occupancy rate of the AFDX network by allowing additional traffic from other critical and non-critical functions. Such harmonization of AFDX network with mixed criticality flows necessitates the use of QoS mechanism to satisfy the delay constraints in different classes of flow. In this thesis we study such QoS-aware network, in particular, based on DRR and WRR scheduling. We propose an optimal bandwidth distribution method that ensures the service required by critical flows while providing maximum service to other non-critical flows. We also propose an optimized NC approach to compute tight delay bounds. Our approach has led to computation of up to 40% tighter bounds, in an industrial AFDX configuration, as compared to the classical approach

AeroRing: Avionics Full Duplex Ethernet Ring with High Availability and QoS Management

The avionics standard AFDX has been introduced to provide high speed communication for new generation aircraft. However, this switched network is deployed in a full redundant way, which leads to significant quantities of wires. To overcome this limitation, a new avionic communication network, called AeroRing, is proposed in this paper to decrease the wiring weight, while guaranteeing the required performance and safety levels. AeroRing is based on a Gigabit Ethernet technologyand implements a daisy-chain wiring scheme on a Full Duplex ring topology. First, the main features of such a proposal, and particularly the QoS and robustness management, are detailed. Then, numerical results of some Performance Indicators (PI) are illustrated to highlight its ability to guarantee the avionics requirements

Analyse pire cas exact du réseau AFDX

L'objectif principal de cette thèse est de proposer les méthodes permettant d'obtenir le délai de transmission de bout en bout pire cas exact d'un réseau AFDX. Actuellement, seules des bornes supérieures pessimistes peuvent être calculées en utilisant les approches de type Calcul Réseau ou par Trajectoires. Pour cet objectif, différentes approches et outils existent et ont été analysées dans le contexte de cette thèse. Cette analyse a mis en évidence le besoin de nouvelles approches. Dans un premier temps, la vérification de modèle a été explorée. Les automates temporisés et les outils de verification ayant fait leur preuve dans le domaine temps réel ont été utilisés. Ensuite, une technique de simulation exhaustive a été utilisée pour obtenir les délais de communication pire cas exacts. Pour ce faire, des méthodes de réduction de séquences ont été définies et un outil a été développé. Ces méthodes ont été appliquées à une configuration réelle du réseau AFDX, nous permettant ainsi de valider notre travail sur une configuration de taille industrielle du réseau AFDX telle que celle embarquée à 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