Eventual Clusterer: A Modular Approach to Designing Hierarchical Consensus Protocols in MANETs

This paper proposes a modular approach to the design of hierarchical consensus protocols for the mobile ad hoc network with a static and known set of hosts. A two-layer hierarchy is imposed on the network by grouping mobile hosts 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. The proposed modular approach separates the concerns of clustering hosts from achieving consensus. A clustering function, called eventual clusterer (denoted as diamC), is designed for constructing and maintaining the two-layer hierarchy. Similar to unreliable failure detectors, diamC greatly facilitates the design of hierarchical protocols by providing the fault-tolerant clustering function transparently. We propose an implementation of diamC based on the failure detector diamS. Using diamC, we design a new hierarchical consensus protocol. As shown by the performance evaluation results, the proposed consensus protocol can save both message cost and time cost. Our proposed modular design is therefore effective and can lead to efficient solutions to achieving consensus in mobile ad hoc networks.