Validating Wireless Congestion Control and Reliability Protocols using ProB and Rodin

Implicit hop-by-hop congestion control is a novel congestion control paradigm for wireless multihop networks. Implemented in the CXCC protocol, it has already proven its performance in simulations and measurements. Since CXCC makes extensive use of the properties of an inherently unreliable medium, it is, however, vitally necessary to validate the correctness of the protocol. Indeed, an early version of the CXCC protocol contained deadlocks. CXCC is complemented by an end-to-end reliability mechanism in the BarRel transport protocol. In combination, both protocols offer TCP-equivalent service in dynamic wireless multihop environments, including, e.g., route changes. BarRel relies on properties of CXCC. It therefore likewise deserves validation. In this work we attempt to validate the CXCC and BarRel protocols using formal methods. To this end, we are developing various models in B and Event-B. We are using the ProB tool to animate and model check the formal models and the Rodin platform to formally prove correctness properties. In this paper we present first encouraging steps towards a full formal validation of the protocols.