We address the enumeration and the leader election problems over partially anonymous and multi-hop broadcast networks. We consider an asynchronous communication model where each process broadcasts a message and all its neighbours receive this message after arbitrary and unpredictable time. In this paper, we present necessary conditions that must be satisfied by any graph to solve these problems and we show that these conditions are sufficient by providing an enumeration algorithm on the one hand and a leader election algorithm on the other hand. For both problems, we highlight the importance of the initial knowledge. Considering the enumeration problem, each process only knows the size of the graph and, contrary to related works, the number of its neighbouring processes is unknown. Whereas for the election problem, we show that this combination of knowledge is not sufficient. Our algorithm assumes that each process initially knows a map of the network (without knowing its position in this map). From the complexity viewpoint, our algorithms offer polynomial complexities (memory at each process, number and size of exchanged messages).
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We study the election and the naming problems in the asynchronous message passing model. We present a necessary condition based on Angluin's lifting lemma [1] that must be satisfied by any network that admits a naming (or an election) algorithm. We then show that this necessary condition is also sufficient: we present an election and naming algorithm based on Mazurkiewicz's algorithm [17]. The algorithm we obtained is totally asynchronous and it needs a polynomial number of messages of polynomial size, whereas previous election algorithms in this model are pseudo-synchronous and use messages of exponential size.
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We examine the power and limitations of the weakest vertex relabelling system which allows to change a label of a vertex in function of its own label and of the label of one of its neighbours. We characterize the graphs for which two important distributed algorithmic problems are solvable in this model : naming and election.
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