Study Of PTCC Model Based On Chord Protocol Of P2P Network

Since the increasing popularity of Napster in 1999, more and more attention have been paid to the research of P2P technology. P2P technology makes Internet regains its essence of freedom and equality. Meanwhile, with the utilization of resources improved, the total resources can be shared at a higher level. One of the key technologies in P2P is that it sets up logical overlay network upon physical network so as to provide services of resource organization and location.This paper begins by reviewing the Napster, Gnutella, Kazza and Chord—four typical protocols detailedly. Through analysis, it concludes that Chord possesses fine qualities. Inspired by the conclusion, a Physical Topology besed Compound Chord model—PTCC is put forward. Based upon Chord, the model solves the following problems.(1)The mismatch between physical network and logical overlay network topology. Here, IPv6 protocol which will be inevitable in the future is used as network protocol and the way to devide hash the prefix and suffix of the node's IPv6 address is employed to construct the identifier of the node which is able to carry the location information of the node. In this way, node with the same identifier prefix will be in the same local ring and thus nodes of shorter physical distance will correspondingly have shorter logical distance. Also, within the ring, local pointer table is used for information routing and between rings, inter-pointer table is used.(2)Some resources are not available because of the failure of resource's own nodes or their index nodes.In the model, the share resource's identifier are constructed with the method of multi-keyword hash, then each identifier is published at the same time to the index nodes in the local ring as well as in the foreign ring. Besides, other nodes will also publish the resouces when they possesses them. In this way, the resouce is corresponding with many own nodes and index nodes, so it will be utilized better.(3)Imbalance of load of the reource's own nodes and index nodes caused by hotspot. See the above.The mostly access to resource that published by the above way can be resolved within the local ring.Finally, simulation and quality comparison are made in the thesis through the use of P2PSim simulator developed by MIT. The result shows that PTCC model has superior qualities to Chord on lookup efficiency.