Modelling Overlay-Underlay Correlations Using Visualization

Abstract. Overlay applications are popular as they provide high-level functionality by masking the intrinsic complexity of the underlay network. However, overlays rely on the underlay to provide them with basic connectivity. Therefore, the intrinsic features of the underlay network determine the efficiency of the overlay. Accordingly, studying the interdependency of the overlay and underlay networks leads to a better understanding of overlay application behaviour. We present a visualization-driven analysis technique for evaluating the overlay architecture with respect to the underlay, driven by the goal of overlay engineering. Using Gnutella as a case study, our analysis confirms that Gnutella topology differs from a randomly generated network and that there is an implicit correlation between the overlay and underlay topologies.