Evaluating chord over a hierarchical MANET

Hierarchical network architectures are widely deployed to reduce routing overheads and increase scalability. In our work, we are interested in deploying a P2P overlay in ultimately large-scale Mobile Ad-Hoc Networks (MANETs). We therefore study the performance of such an approach, creating a number of hierarchical network configurations and deploy Chord over them. The clusters are MANETs, running OLSR locally. Each cluster has a gateway, and the gateways are interconnected through a backbone that deploys flooding. As we increase the number of clusters, we keep the number of nodes in the Chord overlay constant and run simulations in OMNeT++ to evaluate the performance of Chord (GET and PUT success ratio, latency). Our results show that overall the performance of the P2P overlay deteriorates as we increase the number of clusters. One of the main reasons is that the backbone carried more and more of the overlay maintenance and lookup traffic, becoming a performance bottleneck. We therefore conclude that deploying a more efficient routing protocol in the backbone, in contrast with the basic flooding approach, may be required to significantly improve the performance of a P2P overlay over hierarchical MANETs.