| In recent years, the P2P network technology of network applications was rapid developed. Initially,BT,Emule as the representative of the P2P network to download software create a rapid download records, compared to the previous network to download have a big leap. Nearly 1-2 years to PPlive fiery as the representative of the network video technology development is inseparable from P2P networkapplications. These enable P2P technology of Internet users in general elicited a great response, so as to bring about a wide range of concerns.But so far, P2P is a relatively new technology, there are still many problems, there are also challenges. But P2P is changing the outlook of the Internet, changing the way of people exchanges. Decentralized P2P, popularity of the low-cost, high efficiency, and its scalability is still worthy of recollection, and to study it.In the P2P network, how to resources for accurate positioning is very important. Compared to the traditional search technology, the rising of P2P search technology currently, not need for servers, but also can be exempted from the restrictions on equipment. Because the resources are very scattered in the P2P network, often in different computer nodes and these nodes is not the resources, and these nodes are free to join and withdraw, this will cause a moment in a P2P network Dynamic changes in species. So P2P network resources raise a new search request. P2P networks and the distribution of resources in the search technical decision with the previous search are very different. As the Internet has a lot of resources are idle, and not fully used. P2P search technology can help people find these idle resources, thereby enhancing the utilization of resources, the complete sharing of resources. At the same time, P2P search technology can also help people to work together. So study P2P search technology has important practical significance.This paper is based on the 2001 from the Massachusetts Institute of Technology put the P2P network Chord thinking of the search algorithm to improve. Therefore, first introduced based on the concept of P2P networks, Several of the basic idea of search algorithm in P2P networks, and its basic search process. Then, the main thrust of this paper - the Chord P2P network search algorithm improvements start with the realization introduced. This paper is composed by theory and simulation realization, the paper mainly to the following aspects:(1) Introduces the structure of the Chord algorithm , analysis of the Chord agreement routing table. Chord algorithm is agreement by the MIT (Massachusetts Institute of Technology) research and development of a distributed structure of the P2P networks for agreement. The basic idea is that represent the keywords and information resources nodes are mapped to a unified position virtual space. Chord According to the IP address of nodes and keyword Hash overall computing gets only one logo. In order to ensure the uniqueness of the identifier, it adopted the same hash function to the keywords and hash computing nodes.Chord is based on the compatibility hash (Consistent Hashing), a resource position and finding algorithm. Requirement to use of the hash algorithm is SHA-1 in Chord agreement.In the Chord algorithm, network nodes logo to model for a ring, m is the identification of resources. In order to enable different nodes through a hash calculated by different ID (id), large enough to take the value of m, m is usually greater than or equal to 160, the median so long almost impossible to guarantee that the ID duplication and ensure the uniqueness of the ID. Construction on the Chord network, the first use of each machine Hash Function by sharing resources and each machine (nodes) to the IP address compatibility hash calculations, the key value calculated by K said. Chord resources and then nodes assigned to the K-value virtual network composed of Chord ring ring.(2) Chord agreement deficiencies. Analysis of Chord of the agreement routing table of redundant.Chord algorithm finger under the table thinking of the structure, a different degree of redundancy is inevitable, and if we can remove the redundant information, add the corresponding number of other nodes effective information will greatly enhance the efficiency of Chord algorithm enquiries.(3) Improvement of Chord agreement programme. Really Chord algorithm routing redundancy, finger on the table to do the improvements, so that it remove redundancy, but also for each node added a table so as to speed up TOP for speed and efficiency. Chord algorithm in the original table of the finger can only cover half of Chord Central, improved the finger Chord table to cover the entire network, and each node increased TOP Table 1 (a certain period of time, resources are often looking for , was joined TOP table). This will improve query speed.(4) Analysis of improve the Chord algorithm theory. Prove that its performance optimization. Chord algorithm to improve, we are most concerned about is the improved performance of the algorithm in the search how. Because the path length is a measure of routing protocol is an important indicator, so we improved the Chord algorithm path length of the theoretical analysis.(5) Design a Chord search algorithm simulation system, the improvement of the Chord algorithm simulation achieves. In the computer network or distributed system of the study, people tend to favor the actual network, because its true, reliable, non-excessive theoretical assumptions, however, this is not the correct choice of P2P, as a large-scale, high - Dynamic Construction of the actual P2P networks to be quite difficult, and the need for expensive overhead. So I think that the "mock" P2P networks achieving a viable system testing, evaluation, and comparison and authentication mechanisms. Therefore, to verify I Chord algorithm routing table of improved performance, I designed a Chord simulator, the Chord algorithm to search properties of experimental analysis.(6) Simulation acquired data, and the original Chord search algorithm analysis, comparison. Fully proved that the improved performance in the Chord algorithm optimization.The localization of the resources in P2P networks is still in the developing stage. In recent years, as people gradually to the new awareness of P2P networks, P2P networks become a popular research. But the P2P network resource location algorithm research in China is still relatively small. In this paper, I improve the Chord algorithm of the search. Chord search algorithm provides a very efficient routing algorithm, and algorithm in the routing table has been added to enhance the search speed. But Chord agreement is exist of redundant items in the routing table. Affect the efficiency of search. In this paper, removed the finger of redundancy in the table has been added to the original Chord search algorithm finger table does not cover the regional nodes, but also joined the TOP table, and design a Chord algorithm simulation system, the original algorithm and improved Chord Chord after the simulation algorithm to achieve the realization of the simulation data for analysis and comparison. Fully prove that improved the Chord algorithm than the original Chord algorithm in the search speed, Jump, nodes, such as delay time performance optimization. Particularly improved the Chord algorithm suitable for the more popular queries cases, if the View in the most recent period, often for resources, the delay time for Jump nodes and the number will be reduced significantly, this way it will be no guarantee will occupy too much space under the premise that everyone Chord ring preserve more nodes in the node information, which improves the search speed. |
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