Avionics Full-DupleX (AFDX) is a switched Ethernet-based network used in modern commercial airplanes for the transmission of command and control avionics flows. These critical flows require deterministic guarantees leading to a lightly loaded network. Aircraft manufacturers envision to carry additional non avionics flows (i.e. video, audio, service) to take advantage of the spare bandwidth. However, it is then compulsory to preserve the real-time guarantees of avionics flows in terms of bounded jitter at the transmitter output and of bounded end-to-end latency. Depending on the type of additional traffic, Quality of Service (QoS) end-to-end guarantees may be offered to the additional flows of lower criticality in terms of reduced delay or bounded jitter for instance. These guarantees can be ensured by scheduling policies at transmitter and switch level. However, an important safety-related constraint is the asynchronous design of avionics distributed systems that prohibits the use of a network-wide synchronization of end systems and switches. Thus, time-triggered networking such as emerging Time-Triggered Ethernet (TTEthernet) or Time-Sensitive Networking (TSN) cannot be leveraged. This paper underlines the benefits of only scheduling flows at the transmitter, which is compatible with the asynchronous safety constraint of avionics systems. We show that it is possible to build a table schedule that carries both critical avionics flows and additional video flows that meet their timing and bandwidth allocation constraints. Therefore, we design scheduling strategies for efficient distribution of flows in the table scheduling whose performance is compared to the optimal schedule minimizing the emission lag of additional flows. Proposed heuristics are constructed such as to favor the network responsiveness for avionics flows thanks to slot over-provisioning. Extensive results on an A350 AFDX industrial configuration show that for a transmitter load of up to 70% of the available bandwidth, the uniform allocation heuristic provides a performance close to optimal in terms of minimum emission lag for additional flows, so offering a practical configuration heuristic to industry.

中文翻译：

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异步 AFDX 航空电子网络终端系统混合关键流的时间触发调度

航空电子设备全双工 (AFDX) 是一种基于交换以太网的网络，用于现代商用飞机中，用于传输命令和控制航空电子设备流。这些关键流程需要确定性保证，从而形成轻负载的网络。飞机制造商希望承载额外的非航空电子设备流（即视频、音频、服务）以利用空闲带宽。然而，就必须在发射机输出的有限抖动和有限的端到端延迟方面保持航空电子设备流的实时保证。根据附加流量的类型，可以向较低关键性的附加流量提供服务质量（QoS）端到端保证，例如在减少延迟或有界抖动方面。这些保证可以通过发射机和交换机级别的调度策略来确保。然而，一个重要的安全相关约束是航空电子分布式系统的异步设计，它禁止使用终端系统和交换机的网络范围同步。因此，无法利用时间触发网络，例如新兴的时间触发以太网（TTEthernet）或时间敏感网络（TSN）。本文强调了仅在发射机处调度流的好处，这与航空电子系统的异步安全约束兼容。我们表明，可以构建一个既承载关键航空电子设备流又满足其时序和带宽分配约束的附加视频流的表调度。因此，我们设计了调度策略，以在表调度中有效分配流量，其性能与最佳调度进行比较，以最小化附加流量的排放滞后。所提出的启发式方法的构建是为了通过时隙过度配置来提高航空电子设备流的网络响应能力。 A350 AFDX 工业配置的广泛结果表明，对于高达可用带宽 70% 的发射机负载，统一分配启发式在附加流量的最小发射延迟方面提供了接近最佳的性能，因此提供了实用的配置启发式到工业。