A scheme to determine QoS requirements for control network data over IP

Interconnections between control networks like fieldbus systems and IP-based networks are widely used, but have to cope with very different timing behavior on either side. The main problem is how to meet QoS requirements imposed by the control application on the IP-based network. Based on the common two-level interconnection model (gateway or tunneling router), we define classification criteria for the relevant QoS parameters. In addition, we classify typical applications in control networks according to their requirements concerning network delay and derive a method to calculate the requirements. An example illustrates the method by investigating the effects of variable delays on a LonWorks application tunneled over an IP network.