Just a Second -- Scheduling Thousands of Time-Triggered Streams in Large-Scale Networks

TL;DR

This paper introduces two scalable algorithms, H2S and CELF, for scheduling thousands of time-triggered streams in large-scale networks like TTEthernet, enabling quick schedule computation for safety-critical systems.

Contribution

The paper presents two novel algorithms that significantly improve the scalability and efficiency of scheduling time-triggered streams in large networks.

Findings

H2S and CELF can schedule over 45,000 streams in seconds.

Algorithms are effective on both random and real-world energy grid networks.

Scalable scheduling supports real-time extensions in large cyber-physical systems.

Abstract

Deterministic real-time communication with bounded delay is an essential requirement for many safety-critical cyber-physical systems, and has received much attention from major standardization bodies such as IEEE and IETF. In particular, Ethernet technology has been extended by time-triggered scheduling mechanisms in standards like TTEthernet and Time-Sensitive Networking. Although the scheduling mechanisms have become part of standards, the traffic planning algorithms to create time-triggered schedules are still an open and challenging research question due to the problem's high complexity. In particular, so-called plug-and-produce scenarios require the ability to extend schedules on the fly within seconds. The need for scalable scheduling and routing algorithms is further supported by large-scale distributed real-time systems like smart energy grids with tight communication requirements. In this paper, we tackle this challenge by proposing two novel algorithms called Hierarchical Heuristic Scheduling (H2S) and Cost-Efficient Lazy Forwarding Scheduling (CELF) to calculate time-triggered schedules for TTEthernet. H2S and CELF are highly efficient and scalable, calculating schedules for more than 45,000 streams on random networks with 1,000 bridges as well as a realistic energy grid network within sub-seconds to seconds.