BUZZ: Testing Context-Dependent Policies in Stateful Data Planes (CMU-CyLab-14-013)

Network operators spend significant effort in ensuring that the network meets their intended policies. While recent work on checking reachability and isolation policies have taken giant strides in this regard, they do not handle context-dependent policies that operators implement via stateful data plane elements. To address this challenge, we present the design and implementation of BUZZ, a testing framework to ensure that a network with stateful data plane elements meets complex context-dependent policies. In designing BUZZ, we address significant challenges in: (1) modeling stateful data plane elements, and (2) tackling the state-space explosion problem in generating test scenarios. We also implement practical heuristics to resolve interference from background traffic and to localize sources of policy violations. We demonstrate the scalability of BUZZ in localizing policy violations on networks with more than 100 nodes.