Detecting IP Prefix Mismatches on SDN Data Plane

Software-defined networking (SDN) enables centralized network management by separating the control and data plane. However, the actual packet behavior on data-plane may deviate from the control-plane rules sometimes. Many probe-based tools have been developed to verify the data plane’s correctness and detect forwarding errors by sending test packets. However, they all assume simple fault models, such as incorrect action fields in the forwarding rules. To address this gap, this paper identifies a new class of error affecting the IP match field called IP prefix mismatch, which previous tools failed to identify thoroughly. We categorize IP prefix mismatches into prefix shrinkage and prefix expansion. We then present novel test packet generation algorithms to construct test packets designed to exhibit different behaviors depending on the presence of these errors. Using these algorithms, we develop a system that guarantees the discovery of at least one prefix mismatch in every detection round, even in the worst-case scenario.Several experiments were conducted to compare our system to a conventional probe-based method that sends a single test packet per rule. The results demonstrate that our system achieves perfect fault coverage within a minimal number of detection rounds. Even when faced with a network containing 50% erroneous rules, it successfully identifies all prefix mismatches within an average of only two detection rounds. In contrast, the conventional method fails to uncover all errors, even after spending on additional detection rounds.