Managing industrial communication delays with software-defined networking

Recent technological advances have fostered the development of complex industrial cyber-physical systems with communication delay requirements. The consequences of delay requirement violation in such systems may become increasingly severe. In this paper, we propose a contract-based fault-resilient methodology which aims at managing the communication delays of network flows in industries. With this objective, we present a lightweight mechanism to estimate end-to-end communication delays in the network where the clocks of the switches are not synchronized. The mechanism aims at providing high level of accuracy with little communication overhead. We then propose a contract-based framework using software-defined networking (SDN) where the components are associated with delay contracts and a resilience manager. The proposed resilience management framework contains: (1) contracts which state requirements about components' behaviors, (2) observers which are responsible to detect contract failure (fault), (3) monitors to detect events such as run-time changes in the delay requirements and link failure, (4) control logic to take suitable decisions based on the type of the fault, (5) resilience manager to decide response strategies containing the best course of action as per the control logic decision. Finally, we present a delay-aware path finding algorithm which is used to route/reroute the network flows to provide resilience in the case of faults and, to adapt to the changes in the network state. Performance of the proposed framework is evaluated with the Ryu SDN controller and Mininet network emulator.