Abstract-Underlay-unawareness in P2P systems can result in sub-optimal peer selection for overlay routing and hence poor performance. The majority of underlay aware proposals for peer selection focus on finding the shortest overlay routes by selecting the nearest peers according to proximity. However, in case of multiple and parallel downloads, if the underlay paths between a downloader and its selected nearest peers share a bottleneck, this can cause congestion, leading to performance deterioration instead of improvement. This effect was neglected in previous work because, in today's Internet, the bottleneck is usually not shared as it is the end user's access link. This is no longer the case in more modern scenarios, e.g. with FTTH or with upcoming innetwork caching techniques such as DECADE. We propose an improved peer selection approach for P2P applications called Fewest Common Hops (FCH) that ensures proximity based node selection having maximum path disjointness. It is a client based, infrastructure independent heuristic to optimize download time for multiple and parallel downloads in P2P content distribution applications. Simulations show that, even when FCH is implemented in the simplest possible fashion (using only traceroute), it can significantly decrease the download time.
Cloud computing is an emerging patterning that provides computing, communication and storage resources-as-service over a network. In existing system, data stored in a cloud is unsafe due to the eaves dropping and hacking process. To overcome the drawbacks of earlier approaches, Division and Replication of Data in the Cloud for Optimal Performance and Security (DROPS) methodology is used. The node selection is ensured by means of Graph Topology Grid Algorithm and also data is encrypted here for security. In this process, the common data are divided into multiple nodes and replicate the fragmented data over the cloud nodes. Each data is stored in a different node as fragments in individual locations. In case of any attackers attack a node, no meaningful information will expose to them. The controlled replication of the file fragments is ensured and each of the fragments is replicated only once for the purpose of improved security and minimal retrieval time. In this survey, various relevant approaches were studied and analyzed. Furthermore the DROPS with Graph Topology Grid Algorithm give the better way of security in cloud environment over the earlier approaches.
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