Assessing the Maturity of SDN Controllers with Software Reliability Growth Models

In software defined networking (SDN), critical control plane functions are offloaded to a software entity known as the SDN controller. Today's SDN controllers are complex software systems, owing to heterogeneity of networks and forwarding devices they support, and are inherently prone to bugs. Our previous work showed that software reliability growth models (SRGM) can model the stochastic nature of bug manifestation process open source SDN controllers. In this paper, we focus on different applications of our SRGM framework crucial for an efficient management of SDN-based networks. We provide guidelines for network operators to decide when the controller software is mature enough to be deployed in operational environment, based on the reliability requirements of network applications, and quantify the marginal benefits of the prolonged testing phase on the software quality. We show how the accuracy of software reliability prediction in the early phase of the software lifecycle can be improved by extrapolating the behavior of previous controller software releases. We also propose software maturity metrics that can be used by operators to discriminate between the competing SDN controller designs, i.e., ONOS and OpenDaylight, when software reliability is a major concern.