  Industrial cyber-physical systems (CPS) have gained enormous attention of
manufacturers in recent years due to their automation and cost reduction
capabilities in the fourth industrial revolution (Industry 4.0). Such an
industrial network of connected cyber and physical components may consist of
highly expensive components such as robots. In order to provide efficient
communication in such a network, it is imperative to improve the
Quality-of-Service (QoS). Software Defined Networking (SDN) has become a key
technology in realizing QoS concepts in a dynamic fashion by allowing a
centralized controller to program each flow with a unified interface. However,
state-of-the-art solutions do not effectively use the centralized visibility of
SDN to fulfill QoS requirements of such industrial networks. In this paper, we
propose an SDN-based routing mechanism which attempts to improve QoS in robotic
cyber-physical systems which have hard real-time requirements. We exploit the
SDN capabilities to dynamically select paths based on current link parameters
in order to improve the QoS in such delay-constrained networks. We verify the
efficiency of the proposed approach on a realistic industrial OpenFlow
topology. Our experiments reveal that the proposed approach significantly
outperforms an existing delay-based routing mechanism in terms of average
throughput, end-to-end delay and jitter. The proposed solution would prove to
be significant for the industrial applications in robotic cyber-physical
systems.
