Modelling Link State Routing in Event-B

In this paper we present a stepwise formal development of the Optimised Link State Routing (OLSR) protocol in Event-B. OLSR is a proactive routing protocol which finds routes for different destinations in advance by exchanging control messages through the network. As a consequence, whenever a data packet is injected into the network can be delivered to a certain destination immediately. To achieve this, routing tables in OLSR are continuously updated, by following a rather complicated algorithm. By modelling OLSR in Event-B, we address the scalability problem of our previous work [1], and structure the OLSR complexity in five distinct abstraction layers. These layers are manageable to understand and to verify and are linked to each other by refinement. As Event-B is supported by a theorem proving platform (Rodin), we model and prove functional properties of OLSR in an automated and interactive manner, at a highly general level. Our approach can serve as a proof-of-concept to be adapted to modelling and verifying of the other routing protocols for large-scale networks.