Model Checking Probabilistic Lossy Channel Systems

Lossy channel systems model a set of nite state processes interacting with each other over unbounded, lossy FIFO channels. This computational model is an abstraction of protocols in the lower layers of the network protocol hierarchy. In spite of its unbounded FIFO queues the Lossy channel system model is not turing-powerful. It has been shown that the reachability problem is decidable 1]. However, the model-checking problem, against speciications in linear time temporal logic (LTL), is known to be undecidable 2]. Given that the rate of message loss in communication systems can be probabilistically characterized we consider a probabilistic version of Lossy channel systems. We show that the problem of checking whether a LTL requirement holds almost always. i.e., with probability 1, of probabilistic lossy channel systems (PLCS) is decidable. As can be expected the probability of message loss does not play a part in the model-checking procedure.