Analysis of Distributed Abstract Machines Damien Pous ENS Lyon, France. We illustrate the use of recently developed proof techniques for weak bisimulation sing a generic framework for the definition of distributed abstract machines based on a message-passing implementation. We first define this framework, and then focus on the algorithm which is used to route messages asynchronously to their destination. A first version of this algorithm can be analysed using the standard bisimulation up to expansion proof technique. We show that in a second, optimised version, rather complex behaviours appear, for which more sophisticated techniques, relying on termination arguments, are necessary to establish behavioural equivalence. Key words: weak bisimilarity, up-to techniques, process algebras, distributed machines, forwarders.