Enhanced Fast Failover for Software-Defined Smart Grid Communication Networks

Abstract

Future energy systems depend on a corresponding Information and Communication Technology (ICT) overlay, allowing timely transmission of critical grid information in particular in case of failures or other unanticipated events. Therefore, to maintain grid stability, Smart Grid communication networks are required to be highly reliable and real-time capable. Within this paper, we propose and evaluate techniques for improved fault tolerance with regard to link failures within the ICT infrastructure, utilizing the concepts of Software-Defined Networking (SDN). centralized and decentralized approaches for both failure detection and traffic recovery are compared. While decentralized approaches, employing Bidirectional Forwarding Detection and OpenFlow's fast failover groups, allow for shorter traffic disruptions by saving the delay of controller-switch communication, they result in sub-optimal configurations and possibly overloaded links. Vice versa, controller-driven approaches, using a custom heartbeat detection mechanism, may offer better alternative configurations due to fast re-calculation of routes, yet incur higher delays. Combining the advantages of both approaches, a hybrid concept is proposed, which enables nearly instant local recovery, succeeded by immediate optimal route updates, issued by the SDN controller. Thus, failover times are reduced to 4.5 ms mean delay, fulfilling IEC 61850 Smart Grid requirements, while providing optimal routes almost continuously and maintaining defined Quality-of-Service (QoS) levels.