Query-Based Model Checking of Ad Hoc Network Protocols

Abstract

A prominent source of complexity in the verification of ad hoc network (AHN) protocols is the fact that the number of network topologies grows exponentially with the square of the number of nodes. To combat this instance explosion problem, we present a query-based verification framework for AHN protocols that utilizes symbolic reachability analysis. Specifically we consider AHN nodes of the form P:I, where P is a process and I is an interface: a set of groups, where each group represents a multicast port. Two processes can communicate if their interfaces share a common group. To achieve a symbolic representation of network topologies, we treat process interfaces as variables and introduce a constraint language for representing topologies. Terms of the language are simply conjunctions of connection and disconnection constraints of the form $conn({\mathcal{J}}_i,{\mathcal{J}}_j)$ and $dconn({\mathcal{J}}_i, {\mathcal{J}}_j)$, where ${\mathcal{J}}_i$ and ${\mathcal{J}}_j$ are interface variables. Our symbolic reachability algorithm explores the symbolic state space of an AHN in breadth-first order, accumulating topology constraints as multicast-transmit and multicast-receive transitions are encountered. We demonstrate the practical utility of our framework by applying it to the problem of detecting unresolved collisions in the LMAC protocol for sensor networks.