Measuring delays of ethernet communication for distributed real-time applications using carrier sense

Ethernet is emerging for many distributed real-time applications in industrial environments. It is also considered for substation automation in power systems with regard to IEC 61850 offering many advantages over conventional parallel wiring with analog signals. Mission-critical for protection and control systems as well as other demanding applications is the end-to-end delay of messages. Beside the frame duration of an Ethernet message on the physical layer, the overall delay is affected by processing times of communication stacks and applications significantly. A timing analysis of Ethernet frames is possible with standard network interface cards (NICs) but a high-resolution is only given with specific hardware or professional network analyzers. Furthermore, to determine stack processing delays, immediate signals are required from the application prior to the transmission and after retrieval additionally. This paper proposes a method to measure delays of Ethernet communication with a common transceiver. The achievable timing resolution is less than 0.1μs using a typical micro-controller unit (MCU).