In the high-tech and automotive industry, bandwidth considerations and widely accepted standardization are two important reasons why Ethernet is currently being considered as an alternative solution for real-time communication (compared to traditional fieldbusses). Although Ethernet was originally not intended for this purpose, the development of the Ethernet AVB standard enables its use for transporting high-volume data (e.g. from cameras and entertainment applications) with low-latency guarantees. In complex industrial systems, the network is shared by many applications, developed by different parties. To face this complexity, the development of these applications must be kept as independent as possible. In particular, from a network point of view, progress of all communication streams must be guaranteed, and the performance for individual streams should be predictable using only information regarding the stream under study and the general parameters of the communication standard used by the network. Initial methods to guarantee latency for Ethernet AVB networks rely on the traditional busy-period analysis. Typically, these methods are based on knowledge of the inter-arrival patterns of both the stream under study and the interfering streams that also traverse the network. The desired independence is therefore not achieved. In this paper, we present an independent real-time analysis based on so-called eligible intervals, which does not rely on any assumptions on interfering priority classes other than those enforced in the Ethernet AVB standard. We prove this analysis is tight in case there is only a single higher-priority stream, and no additional information on interference is known. In case there are multiple higher-priority streams, we give conditions under which the analysis is still tight. Furthermore, we compare the results of our approach to the two most recent busy-period analyses, point out sources of pessimism in these earlier works, and argue that assuming more information on the sources of interference (e.g. a minimal inter-arrival time between interfering frames) has only limited advantages.

中文翻译：

---

以太网 AVB 中各个优先级的独立 WCRT 分析

在高科技和汽车行业，带宽考虑和广泛接受的标准化是目前以太网被视为实时通信的替代解决方案（与传统现场总线相比）的两个重要原因。尽管以太网最初并非用于此目的，但以太网 AVB 标准的发展使其能够以低延迟保证传输大容量数据（例如来自相机和娱乐应用程序）。在复杂的工业系统中，网络由不同方开发的许多应用程序共享。为了面对这种复杂性，这些应用程序的开发必须尽可能保持独立。特别是从网络的角度来看，必须保证所有通信流的进度，并且单个流的性能应该是可预测的，仅使用有关正在研究的流的信息和网络使用的通信标准的一般参数。保证以太网 AVB 网络延迟的初始方法依赖于传统的繁忙期分析。通常，这些方法基于所研究的流和也穿过网络的干扰流的到达间隔模式的知识。因此无法实现所需的独立性。在本文中，我们提出了基于所谓的合格间隔的独立实时分析，该分析不依赖于除以太网 AVB 标准中强制执行的那些优先级之外的任何关于干扰优先级的假设。我们证明这种分析是严密的，以防只有一个更高优先级的流，并且没有关于干扰的额外信息是已知的。如果有多个更高优先级的流，我们会给出分析仍然紧张的条件。此外，我们将我们的方法的结果与最近两个繁忙期分析的结果进行了比较，指出了这些早期工作中悲观主义的来源，并认为假设有更多关于干扰源的信息（例如，干扰之间的最小到达间隔时间）框架）的优势有限。