Testing Black-Box SDN Applications with Formal Behavior Models

The programmability of Software-Defined Networking (SDN) challenges the correctness and reliability of networks. There may be design flaws as well as implementation bugs in SDN applications. White-box testing methods with formal models rely on source codes, which limits the applicability of these methods. Black-box methods without behavior models cannot systematically cover an application's functions. Most previous work has mainly focused on design flaws and has ignored implementation bugs. In this paper, we propose a new black-box test framework to detect both design flaws and implementation bugs. Following this test framework, we propose a new model, Information Table Extended State Machine (IT-EFSM), combining a group of parallel state machines and an abstract topology to specify the SDN applications. We employ a model checking tool to generate tests against design flaws and propose a test generation based on partial composition, symmetry simplification on the topology and topology simulated execution to expose implementation bugs. The experimental results of the testing process demonstrate the effectiveness and applicability of our method.