This paper presents a programming experiment of a complex network routing protocol for mobile ad hoc networks within the ReactiveML language. Mobile ad hoc networks are highly dynamic networks characterized by the absence of physical infrastructure. In such networks, nodes are able to move, evolve concurrently and synchronize continuously with their neighbors. Due to mobility, connections in the network can change dynamically and nodes can be added or removed at any time. All these characteristics — concurrency with many communications and the need of complex data-structure — combined to our routing protocol specifications make the use of standard simulation tools (e.g., NS, OPNET) inadequate and network protocols appear to be very hard to program efficiently in conventional programming languages. In this paper, we show that the synchronous reactive model, as introduced in the pioneering work of Boussinot, matters for programming such systems. This model provides adequate programming constructs — namely synchronous parallel composition, broadcast communication and dynamic creation — which allow for a natural implementation of the hard part of the simulation. The implementation has been done in ReactiveML, an embedding of the reactive model inside a statically typed, strict functional language. ReactiveML provides reactive programming constructions with most of the features of Ocaml. Moreover, it provides an efficient execution scheme for reactive constructs which made the simulation of real-size examples feasible. Experimental results show that the ReactiveML implementation is two orders of magnitude faster than the original C version; it was able to simulate more than 1000 nodes where the original C version failed (after 200 nodes) and is twice faster than the version programmed in NAB
