Finding bugs in network protocols using simulation code and protocol-specific heuristics

Traditional network simulators perform well in evaluating the performance of network protocols but lack the capability of verifying the correctness of protocols. To address this problem, we have extended the J-Sim network simulator with a model checking capability that explores the state space of a network protocol to find an execution that violates a safety invariant. In this paper, we demonstrate the usefulness of this integrated tool for verification and performance evaluation by analyzing two widely used and important network protocols: AODV and directed diffusion. Our analysis discovered a previously unknown bug in the J-Sim implementation of AODV. More importantly, we also discovered a serious deficiency in directed diffusion. To enable the analysis of these fairly complex protocols, we needed to develop protocol-specific search heuristics that guide state-space exploration. We report our findings on discovering good search heuristics to analyze network protocols similar to AODV and directed diffusion.