Protocol validation in complex systems

Abstract

Protocol validation and verification techniques have been applied successfully for a number of years to a wide range of protocols. The increasing complexity of our communications systems requires us to examine existing techniques and make a realistic assessment of which techniques will be applicable to the complex systems of the future. We believe that validation techniques based on an exhaustive reachability analysis will not be effective. Sampling techniques, such as executing a random walk through the reachable state space, are effective in complex systems, since most protocol errors occur in many different states of the system. More than 10 years have elapsed since the first automated validation techniques were first applied to communications protocols [1,2]. In the meantime, considerable advances have been made in validation technology, but more significantly, the scale and nature of the validation problem have changed. The communications systems that we need to validate today are significantly more complex than those of ten years ago. Our methods must evolve in order to address the current challenge. This paper is concerned primarily with the nature of the validation process, and the results that we might reasonably expect to achieve when validating protocols in complex communications systems.