Guided Exploration of Control-Plane Routing States

In recent years, significant progress has been made towards scalable network control-plane verification. Yet, operators are still hesitant to deploy such systems. We argue that this reluctance is in part due to a semantic gap between operators reasoning about routing states and verifiers exploring the space of environments. Indeed, operators express the specification in terms of behavior of routing states, while verifiers usually rely on solvers to find specific environments that violate the specification. This semantic gap prevents users from guiding these solvers to directly explore routing states that violate the specification, or to search for states that are most relevant or likely.In this paper, we present a new approach for flexible control-plane verification. Instead of relying on rigid off-the-shelf solvers, we design a novel backtracking algorithm to directly explore the space of routing states. This enables users to guide the exploration according to the specification and domain-specific knowledge from operators. This algorithm paves the way for novel use cases, ranging from finding relevant (e.g., likely) counterexamples to performing verification of probabilistic specifications.