P2P Overlay Performance in Large-Scale MANETs

We explored how to deploy P2P overlays in ultimately large-scale Mobile Ad-Hoc Networks (MANETs). We therefore studied the performance of P2P overlays such as Chord, creating a number of flat and hierarchical MANET networks. The hierarchical network consists of clusters, interconnected by a backbone. The subnetworks (cluster or the whole network) ran OLSR as network-layer routing protocol. Each cluster had a gateway, interconnected through a backbone that deployed flooding. As we increased the number of clusters, we kept the number of nodes in the Chord overlay constant. Using simulations in OMNeT++, we evaluated the P2P performance. Our results show that an unmodified P2P network does not perform well even for relatively small network sizes. The performance can be improved through the use of a cross-layered P2P solution, such as OneHopOverlay4MANET. However, such cross-layered approaches require complete information about overlay nodes from the routing layer and are therefore not suitable in hierarchical MANETs. For hierarchical underlays, the performance of the P2P overlay deteriorated as we increased the number of clusters. One of the main reasons is that the backbone quickly became a performance bottleneck.