Fragmentation Strategies for Real-Time Ethernet PROFINET (Masterarbeit)


Alexander Merkle


Ethernet has emerged to be the de-facto standard for local area networks. In this thesis we will discuss the task of fragmentation for PROFINET, an Ethernet based real-time bus system for industrial automation applications. The real-time capabilities of PROFINET are based on a bandwidth splitting approach via TDMA. In order to improve the achievable TDMA cycle-time the maximum transmission unit must be reduced. This is done transparently by fragmentation while keeping compatibility to legacy Ethernet devices. In this thesis multiple PROFINET compatible fragmentation algorithms were developed and compared. On the other hand, the influence of the maximum transmission unit to the delay of real-time traffic was analyzed. Thereby contradicting requirements during the delay and bandwidth optimization were found. Finally, we combined these insights and found a compromise improving the delay and jitter of delay sensitive traffic while keeping the performance of bandwidth sensitive traffic more or less equal. The analytical results were deduced from a simple PROFINET model which was verified using a SystemC event simulation.