The Eventual Clusterer Oracle and Its Application to Consensus in MANETs

This paper studies the design of hierarchical consensus protocols for mobile ad hoc networks. A two-layer hierarchy is imposed on the mobile hosts by grouping them into clusters, each with a clusterhead. The messages from and to the hosts in the same cluster are merged/unmerged by the clusterhead so as to reduce the message cost and improve the scalability. We adopt a modular method in the design, separating clustering from achieving consensus using the clusters. The clustering function, named eventual clusterer (denoted as diamC), is designed to construct a cluster-based hierarchy over the mobile hosts in the network. Since diamC provides the fault tolerant clustering function transparently, it can be used as a new oracle (i.e. an abstract tool to provide some kind of information about the state of the system) for the design of hierarchical consensus protocols. Based on diamC, we design a new consensus protocol, which can significantly reduce the message cost of achieving consensus. We also propose an implementation of the diamC oracle based on the failure detector diamS.