Taking the sting out of flow update peaks in software-defined service chaining

Dynamic network service chaining allows network operators to apply network services to customer traffic on demand and in a highly flexible manner. SDN and particularly OpenFlow-based approaches have been presented that exploit the flexibility and feature richness of OpenFlow for service chaining in data center settings. These systems often use network architectures similar to MPLS, where network traffic is processed at the network edges and the network core conducts simple packet forwarding only. This approach is suitable for many use cases due to the complementary characteristics of the hardware devices used in the core and the virtual switches used at the edge on virtualization hosts. Yet, this leads to a concentration of processing flow updates solely at the network edges, which can cause lowered QoS during flow update peaks, e.g. when a virtualization host fails. To tackle this problem, in this paper a concept is presented and evaluated that offloads OpenFlow rule updates from software-based edge switches to exploit hitherto unused resources on hardware switches in the core of the network. Furthermore, an analytical model is presented that allows describing the expected gain of the approach based on characteristics of the used OpenFlow devices.