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.