Low-latency hard real-time communication over switched ethernet

Abstract

Ethernet, the most widely used commodity network, increasingly moves toward switches as implementation technology thus replacing buses. This allows to use traffic shaping techniques to implement hard real-time distributed systems on commodity networks. However, because Ethernet switches lack build-in policing features, nodes connected by switched Ethernet need to be cooperative. Although the theory behind traffic shaping for real-time communication is known for some time, it has not been considered for Ethernet so far. In this paper, we present the implementation of traffic shaping on switched Ethernet technology. We make thorough experiments to understand the cost and practical limits of using fast and gigabit Ethernet for hard real-time communication. We do measurements to analyze properties of switches and delays that we can achieve using these switches. We further analyze the influences of non real-time Linux nodes sharing the network.