Sven Kerschbaum

A Framework for Establishing Performance Guarantees in Industrial Automation Networks

In this paper we investigate the application of Network Calculus for industrial automation networks to obtain performance bounds (latency, jitter and backlog). In our previous work we identified the modeling of industrial networks as the most challenging aspect since in industry most users do not have detailed knowledge about the traffic load caused by applications. However, exactly this knowledge is indispensable when it comes to modeling the corresponding arrival curves. Thus, we suggest the use of generalized traffic profiles, which are provided by the engineering tool. During the engineering process, the user has to specialize these profiles to meet the application configurations. The engineering tool derives the corresponding arrival curves from the specialized profiles and calculates the performance bounds using Network Calculus. To guarantee that the calculated performance bounds are kept during the runtime of the industrial automation, we must ensure that the real traffic flows do not exceed their engineered arrival curves. We therefore propose the use of shapers at the edge of the network domain. The shaper configurations can be automatically derived from the engineered arrival curves of the flows.

The need for shaping non-time-critical data in PROFINET networks

Nowadays factory automation customers require that industrial automation networks are capable of transmitting real-time I/O data and non-time-critical data. PROFINET, one of the most used industrial Ethernet standards available today [1], promises that “everything [can be transmitted] on one cable” [2]. Nevertheless, the standard also recommends that the non-time-critical data sent by a device is limited to 3 kilobytes per millisecond to avoid network overload [3]. In this paper we discuss the need for controlling the non-time-critical data sent to PROFINET networks. Since Microsoft Windows is an often used operating system in industrial automation today [4] we show that its built-in traffic shaping capabilities are not appropriate for industrial automation networks since it is not possible to limit the bursts sent by applications. Thus, we developed our own industrial traffic shaper that is able to limit the burst and the rate per non-time-critical flow. This enables us to apply Network Calculus to obtain guaranteed performance bounds for PROFINET networks that both transmit real-time I/O and non-time-critical data [5]. Both the analysis and the Windows traffic shaper are now provided by the Siemens AG as Siemens Network Planner (SINETPLAN) [6]. Our work is not limited to PROFINET but also applicable to Industrial Ethernet technologies based on IEEE 802.3 such as EtherNet/IP.

Auswirkungen der Netzwerkplanung auf die Qualität von Industriellen Anlagen

Bereits heute werden industrielle Automatisierungsnetzwerke zusatzlich zur Ubertragung von NRT-Verkehr verwendet. Dies liegt zum einen am hohen Kostendruck und zum anderen an der zunehmenden Verschmelzung der Ebenen der klassischen Automatisierungspyramide [1, 2]. Mit Blick auf Industrie 4.0 wird sich dieser Trend zukunftig noch weiter verstarken. Dies macht neben der Planung auch die Validierung der zu erwartenden Netzlast in grosen Netzwerken erforderlich. Nach heutigem Stand existieren Losungen, die detailliert IRT, RT und NRTVerkehr in einer Netzwerkzelle modellieren. Diese mussen daher um den zellenubergreifenden Netzwerkverkehr erweitert werden. Ziel der Arbeiten ist die Planung, Analyse, Uberwachung und Steuerung industrieller Kommunikationsnetzwerke, um deren Betriebssicherheit garantieren zu konnen.