Characterising Testing Preorders for Broadcasting Distributed Systems ⋆

Abstract. We present a process calculus for both specifying the desired behaviour of distributed systems and for describing their actual implementation; the calculus is aimed at the internet layer of the TCP/IP reference model. This allows us to define behavioural preorders in the style of DeNicola and Hennessy, relating specifications and implementations for distributed systems at this level of abstraction. The main result of the paper is a complete characterisation of these preorders, for a large class of systems, in terms of traces of extensional actions. This result underpins a sound and complete proof methodology which is demonstrated by the verification of the correct behaviour of a virtual shared memory protocol.