Performance Evaluation and Optimization of Standard-Ethernet Traffic in Ttethernet Systems
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Die approbierte Originalversion dieser Dissertation ist an der Hauptbibliothek der Technischen Universität Wien aufgestellt (http://www.ub.tuwien.ac.at). The approved original version of this thesis is available at the main library of the Vienna University of Technology (http://www.ub.tuwien.ac.at/englweb/). Performance Evaluation and Optimization of Standard-Ethernet Traffic in TTEthernet Systems DISSERTATION submitted in partial fulfillment of the requirements for the degree of Doktor/in der technischen Wissenschaften by Ekarin Suethanuwong Registration Number 0628110 to the Faculty of Informatics at the Vienna University of Technology Advisor: O. Univ. -Prof. Dr. Hermann Kopetz The dissertation has been reviewed by: (O. Univ. -Prof. Dr. Hermann Kopetz) (Prof. Dr.-Ing. habil. Roman Obermaisser) Wien, 10 November 2011 (Ekarin Suethanuwong) Technische Universität Wien A-1040 Wien ▪ Karlsplatz 13 ▪ Tel. +43-1-58801-0 ▪ www.tuwien.ac.at Erklärung zur Verfassung der Arbeit Ekarin Suethanuwong Brigittenauer Länder 222-224, 1200 Wien Hiermit erkläre ich, dass ich diese Arbeit selbständig verfasst habe, dass ich die verwendeten Quellen und Hilfsmittel vollständig angegeben habe und dass ich die Stellen der Arbeit einschließlich Tabellen, Karten und Abbildungen -, die anderen Werken oder dem Internet im Wortlaut oder dem Sinn nach entnommen sind, auf jeden Fall unter Angabe der Quelle als Entlehnung kenntlich gemacht habe. Wien, 10 November 2011 (Ort, Datum) (Unterschrift Verfasser) i ii Performance Evaluation and Optimization of standard-Ethernet Traffic in TTEthernet Systems Nowadays standard Ethernet is widely used in home and office computer networks, and well recognized as the low-layer protocol of the Internet protocol. There are three main advantages of using today’s Ethernet technology: (1) high bandwidths, for example with Fast Ethernet and Gigabit Ethernet, (2) open standard protocol, defined in IEEE 802.3, and (3) low prices of commercial-off-the-shelf standard-Ethernet devices. In additional, today’s Ethernet technology, which is so-called switched Ethernet, has higher bandwidth utilization than traditional Ethernet based on bus network topology, since switched Ethernet provides full-duplex communication and no collision occurrence. However standard-Ethernet, which was not originally designed for real-time communication, does not provide a timely-determinism property. In the last decade there have been many designs that adapt standard Ethernet to provide temporal guarantees. Such a standard-Ethernet based protocol augmenting with temporal guarantees is called real-time Ethernet (e.g. Ethernet POWERLINK, SERCOS III, PROFINET IRT, Ethernet/IP, MODBUS- TCP, AFDX, and TTEthernet). Recently there has been a main driving force behind applications of real-time Ethernet that is the increasing demand for a seamless connectivity between legacy Ethernet networks and real-time Ethernet networks. This can be seen in the industrial automation domain, for example, the connectivity between the administrative tasks of a company (office networks) and the factory floor (fieldbus networks) has been increased. Another main driving force for adapting standard Ethernet to real-time Ethernet is to integrate all application types into a single standard-Ethernet based network. Such a single standard-Ethernet based network is potentially very cost effective, and reduces the complexity of network infrastructure. TTEthernet was designed to be a novel unified communication architecture that meets the requirements of all application types from non real-time applications, to real-time applications, to the most demanding safety-critical real-time applications. TTEthernet were aimed to altogether achieve the three main properties: (1) determinism property for real-time traffic, (2) full standard-Ethernet compatibility for real-time communication, and (3) high Ethernet-bandwidth utilization for standard-Ethernet traffic. Due to the fact that TT traffic in TTEthernet systems takes precedence over standard-Ethernet traffic, the flow of standard-Ethernet traffic depends only on a TT-traffic communication schedule. The objective of this thesis is to investigate a TT- traffic scheduling approach for obtaining the highest performance of standard-Ethernet traffic coexisting with the TT traffic in the same TTEthernet systems. The throughput and timing- performance of standard-Ethernet traffic are evaluated in both simulated and physical 100-Mbps TTEthernet systems. For the simulated TTEthernet systems a simulation model for TTEthernet systems is developed and implemented. iii iv Table of Contents Table of Contents v List of Figures xi List of Tables xvii 1. Introduction 1 1.1 Problem Statement .................................................................................................................2 1.1.1 Dataflow integration in a real-time Ethernet network ....................................................2 1.1.2 Performance of standard Ethernet in a TTEthernet network .........................................5 1.2 Structure of Thesis .................................................................................................................6 2. Basic Concepts 9 2.1 Distributed Real-Time Systems .............................................................................................9 2.1.1 Characteristics of a communication channel ...............................................................11 2.1.2 Event and State Messages ..........................................................................................11 2.1.3 Event-triggered and Time-triggered Communication Systems ...................................12 2.2 The concepts of time-triggered communication for TTEthernet .........................................13 2.2.1 Reference Clock and Local Clock ..............................................................................13 2.2.2 Global Time and Clock Synchronization ...................................................................14 2.2.3 Cluster Cycle ..............................................................................................................15 2.2.4 Message Permanence ..................................................................................................15 2.2.5 Determinism ...............................................................................................................16 2.3 Ethernet Technology ...........................................................................................................17 2.3.1 Ethernet Standard as IEEE 802.3 ...............................................................................17 2.3.2 Shared Ethernet ..........................................................................................................17 2.3.3 Switched Ethernet ........................................................................................................20 2.4 Ethernet Performance Metrics .............................................................................................22 v 2.4.1 Throughput .................................................................................................................22 2.4.2 Latency .......................................................................................................................24 2.5 Mixed-criticality systems ....................................................................................................27 2.6 Discrete Event Simulation ...................................................................................................28 3. State of the Art 31 3.1 EtherNet/IP ..........................................................................................................................31 3.1.1 Structure and Functionality of EtherNet/IP ................................................................32 3.1.2 Performance of EtherNet/IP .......................................................................................34 3.2 PROFINET ..........................................................................................................................36 3.2.1 Structure and Functionality of PROFINET ................................................................37 3.2.2 Performance of PROFINET .......................................................................................41 3.3 MODBUS-TCP ...................................................................................................................42 3.3.1 Structure and Functionality of MODBUS-TCP .........................................................42 3.3.2 Performance of MODBUS-TCP .................................................................................45 3.4 SERCOS III ........................................................................................................................46 3.4.1 Structure and Functionality of SERCOS III ...............................................................46 3.4.2 Performance of SERCOS III ......................................................................................50 3.5 EtherCAT ............................................................................................................................51 3.5.1 Structure and Functionality of EtherCAT ..................................................................51 3.5.2 Performance of EtherCAT ..........................................................................................55 3.6 Ethernet POWERLINK .......................................................................................................55