In a reference implementation, it is demonstrated that it is possible to set up an overlay network that hides any network changes from the service layer. Using a newly proposed four-layered approach, service development may be realized independently from the underlying physical network. In this paper a new model for providing autonomous and decentralized services is proposed, especially focusing on mobile ad hoc networks (MANETs). In order to cope with these requirements, services are expected to adapt to environmental conditions and require minimum human intervention. Future networks are becoming larger in scale, more dynamic and more heterogeneous. Next generation network characteristics increase the complexity in the design and provision of advanced services, making inappropriate the selection of traditional approaches. Interesting directions and research questions worthy of investigation. Three veins of literature show several shortcomings which form several Our survey and analyses of the different schemes in the Theory that have shown to be effective in defending against the attack underĬertain assumptions. Social networks used as bootstrapping security and tools from random walk The third and last vein of literature is by mitigating the attack combining Network coordinates, recurring cost as by requiring clients to solve puzzles. The attack by resources testing, which can by in the form of IP testing, The second vein of literature considers defending against Theįirst vein of literature considers defending against the attack using trustedĬertification, which is done by either centralized certification or distributedĬertification using cryptographic primitives that can replace the centralizedĬertification entity. Trusted certification, using resources testing, and using social networks. Three major veins of literature work to defend against the attack: using In this paper we have a close look at the Sybil attack and advances inĭefending against it, with particular emphasis on the recent work. The measured results show that Gnutella network has pretty well scalability as well as the abilities to tolerating failures and attacks against peers, but with low routing efficiencies Gnutella overlay network has the small world characters, but it is not a scale-free network, which has developed over time following a different set of growth processes from those of the BA (Barabdsi-Albert) model. Fitting results indicate that power law could fit better for the degree-rank distribution and frequency-degree distribution of bottom level graphs, while Gaussian could describe the frequency-degree distribution of the top level graphs. The bottom level graph shows power law both in its degree-rank distribution and in its frequency-degree distribution. The results indicate that each tier of Gnutella network shows individual characters, namely, the top level graph fits the power law in degree-rank distribution, but follows the Gaussian function in frequency-degree distribution. The small world characteristics for Gnutella network are discussed. The properties of degree-rank distribution and frequency-degree distributions of the measured topology graphs are analyzed in detail. In this paper, the measured Gnutella network topology is basically taken as an example. Mapping and analyzing the topological properties of P2P overlay network will benefit the further design and development of the P2P networks.