Faster Pushdown Reachability Analysis with Applications in Network Verification

Reachability analysis of pushdown systems is a fundamental problem in model checking that comes with a wide range of applications. We study performance improvements of pushdown reachability analysis and as a case study, we consider the verification of the policy-compliance of MPLS (Multiprotocol Label Switching) networks, an application domain that has recently received much attention. Our main contribution are three techniques that allow us to speed up the state-of-the-art pushdown reachability tools by an order of magnitude. These techniques include the combination of classic pre∗ and post∗ saturation algorithms into a dual-search algorithm, an on-the-fly technique for detecting the possibility of early termination, as well as a counter-example guided abstraction refinement technique that improves the performance in particular for the negative instances where the early termination technique is not applicable. As a second contribution, we describe an improved translation of MPLS networks to pushdown systems and demonstrate on an extensive set of benchmarks of real internet wide-area networks the efficiency of our approach.