A Framework for the Timing Analysis of Ethernet-Based Factory Floor Networks
Ref: HURRAY-TR-050301 Publication Date: 1, Mar, 2005
A Framework for the Timing Analysis of Ethernet-Based Factory Floor NetworksRef: HURRAY-TR-050301 Publication Date: 1, Mar, 2005
Throughout the years, researchers have developed and applied a considerable range of theory to the validation of factory-floor distributed real-time systems. Nowadays, some of those systems are based on Ethernet technologies. In fact, a number of characteristics are boosting the eagerness of extending Ethernet to also cover factory-floor distributed real-time applications. Full-duplex links, non-blocking and priority-based switching, bandwidth availability, just to mention a few, are characteristics upon which that eagerness is building up. In the past few years, it is particularly significant the considerable amount of work that has been devoted to the timing analysis of Ethernet-based technologies. It happens, however, that the majority of those works are restricted to the analysis of subsets of the overall computing and communication system, thus without addressing the system as a whole. In fact, Ethernet technology, by itself, does not include features above the lower layers of the communication stack. Where are the higher layers that permit building real industrial applications? And, taking for free that they are available, what is the impact of those protocols, mechanisms and application models on the overall performance of Ethernet-based distributed factory-floor applications? This dissertation attempts to pave the way towards providing some reasonable answers to these issues. To this end, a few analysis approaches are explored with the purpose of setting a framework for developing tools suitable to extract temporal properties of Commercial-Off-The-Shelf (COTS), Ethernet-based factory-floor communication systems. The particular case of Ethernet/IP is taken into the research work. Two models, enabling finding end-to-end response times in Ethernet/IP based distributed systems are provided. The first model is an analytical model, built upon traditional real-time response time analysis, considering a number of worst-case assumptions to derive the end-to-end response time bounds. The second model is a discrete-event simulation model, providing an adequate solution to understand and analyse the timing behaviour of actual systems, also facilitating approaches for timeliness evaluation based on probabilistic measures of meeting deadlines. This may become relevant since modern factory-floor systems tend to be more flexible and adaptive in their nature. Additionally, results from applying both models are presented, and a discussion of the two is provided.
Master Thesis, Escola de Engenharia, Universidade do Minho.