Generic Peer-to-Peer Networks: Theory, Implementation and Applications in Image Retrieval Using the Wavelet Transform

Almost ten years have passed since the expression “peer-to-peer” reached the large internet population. It has had considerable success, but there still seems to be a long way ahead. In these ten years, a wealth of peer-to-peer systems has been proposed by the research institutions, but only few have made it commercially. While the research community introduces ever more advanced structured peer-to-peer networks, the public seems to prefer the simplicity and elasticity of unstructured peer-to-peer networks, despite their numerous and obvious flaws. Even developers or system designers seem to prefer either unstructured networks, or, at best, hybrid systems. Why? One of the important factors, business considerations aside, is that designing, implementing and testing one such system before deployment is virtually impossible for someone without a PhD in the area. Even comparing existing systems is difficult, because there is no unifying benchmarks or models. This thesis addresses this problem by introducing theoretical models for both structured and unstructured networks, by implementing simulators to help system designers get a better idea of the performance before going to a real implementation and, finally, by showcasing an image retrieval application on structured peer-to-peer networks. We organize this work in 4 chapters, in addition to the introductory and concluding remarks. First, we make a thorough overview of the state of the art in peer-to-peer networks, both structured and unstructured, as well as existing attempts at providing a generic model for such networks. In the same chapter, we also review techniques in information retrieval on peer-to-peer networks, as well as image retrieval techniques that we will subsequently adapt for our application environment. Afterwards, we dedicate one chapter for each of the three important contributions of the thesis: the structured network model, the unstructured network model and the image retrieval application. This thesis demonstrates the possibility of defining new peer-to-peer networks or modeling existing designs easily, as well as the applicability of image retrieval techniques in a