Investigations on a Distributed Time-triggered Ethernet Realtime Protocol Used by PROFINET

With a standard bridged Ethernet network, a possible delay of high-priority packets by lower-priority packets that are just being served within a bridge or device cannot be avoided. The results are higher transaction times and jitter values, especially when using long chains of bridges. With this characteristic, Ethernet cannot be used in timecritical synchronous applications. In this paper we analyze the real-time characteristic of a new distributed timeslotting method for Ethernet, which is part of the involved bridges to realize minimized transaction times. This algorithm will be used by the emerging standard PROFINET IRT1 and has therefore practical relevance. The simulation results will be compared with analytical results of a standard Ethernet System with priority support.