Research On The Key Technique Of Distributed Internet Telephony Systems Based On Peer-To-Peer Network

Since the telephone was invented in 1876 by Bell, with increasingly rise of social requirement and continually development of science technology, telephone exchange technology is undergoing the rapidly updating and developing. It has expanded from manual switching to Program Control Switching. After that, VoIP technology and Mobile Communication technology have come. The content for exchanging expands to video, Instance Message, files from only voice.Recently years, Peer-to-Peer (P2P) system is a research field with rapid development. For the application areas of P2P systems have gradually expanded from traditional file sharing to distributed computing over Internet, share of storing space, information searching, instance communication and so on, the technology attracts more and more attention. For the advantages such as distributed controlling, self-organizing, self-adapting and well-scalable of P2P system, it is specially suiting to use in transforming between kinds of data information those with great capacity, distributed internet telephony system is also involved.The distributed structure of P2P system absolutely changes existing centralize-controlling module of telephone exchange network, the P2P system can sufficiently use the host resource of Internet, providing completely self-organizing, well-adaptable, well-scalable and zero-devoted service of distributed internet telephony. Research of P2P system is recently converging in the field of file sharing, information searching, and the study technically aims to distributed internet telephony system based on P2P network has been set to work just now, so there are lots of issues for solving.This dissertation foucus on the existing P2P overlay, and it considers adequately in the specialty of distributed internet telephony system, researches the key issues about distributed internet telephony system in-depth, presents a new network topology of P2P overlay as well as its routing algorithm, solves some key problems. The results of simulation and analyses showing that, compared with the existing P2P system, the network topology and its routing algorithm presented by this dissertation can improve the performance of distributed internet telephony system effectively.In this dissertation, aiming at the requirement of location service in distributed internet telephony system, it firstly presents an unstructured location service system model which is organized based on neighbor region and supports multi-keywords fuzzy search, and defines the abstractly expression of search process using Resource Description Framework (RDF). This model uses the relationship among metadata to describe the relationship among users' characteristic in distributed internet telephony system, organizes the neighbor region according to the relation degree between metadata. Based on the abstract model, this dissertation puts forward a multi-keywords fuzzy search algorithm which is based on the greedy approximate strategy and does not rely on index mechanism, with that, this dissertation presents a search model based on the random nodes distributed in the 2-dimension vector space to simulate the users' calling behavior in distributed internet telephony system, and proves that the model is effective on mathematics. In the end, by simulating and analyzing, it gets the conclusion that the flooding search is much more effective than the parallel search in the peer to peer search system organized by neighbor region and this peer to peer search system enhances the search performance notably than Gnutella.This dissertation defines and realizes the simulation environment, which is based on the P2P system and can reflect the characteristic of actual distributed internet telephony system. The simulation environment can be used to simulate the behaviors of dynamic join, leave, fail, route, etc, and support the network topology from one dimension to multi-dimension. Various P2P routing algorithm and nodes' behavior can be realized by the simulation environment and the performance simulation result can be attained. The simulation environment lays a foundation for future research on P2P overlay.An Incremental Fuzzy Clustering (IFC) algorithm which is based on the absolute self-organization P2P searching system is presented. It can accomplish the incremental cluster by local view in the condition of absolute self-organization. With the basis of the IFC algorithm, a strategy of adding long links of cluster center has been puts forward to improve the search efficiency using small world model, vector clustering method has been proposed by considering the direction of cluster, which improves the searching performance using well-proportioned route table. Based on the IFC algorithm and vector clustering method, this dissertation defines a cluster spatial topological structure based on multi-layer rings, called Small World IFC (SWIFC), and presents a self-adapting radius algorithm for enhancing the self-adaptive ability. The result of simulation shows that the SWIFC cluster algorithm is effective, the average path length reduced by about75% , that is, the call delay of distributed internet telephony system can be shorten.In this dissertation, it puts forward a novel network topology structure, Self-Organizing Multi-Character Overlay (SOMCO), which is suitable to distributed internet telephony system. The SOMCO adopts dimension positive, regular, limited Cartesian space structure, achieves construction of network topology by making use of SWIFC algorithm. It proposes a scheme to solve the inter-communication of heterotypic network, and presents a space transformation mechanism for enhancing the P2P attribution of nodes in spatial topology. Concretely realizable algorithm for vector clustering is also provided. Based on the SOMCO topology structure, SOMCO routing algorithm is proposed. Considering the behaviors of nodes, the dissertation put forward a route replacement algorithm combining with Ant colony algorithm (ACA), which reduces the route convergent time and improves the robustness, without any additional network load,. The result of simulation shows, compared with existing route algorithms of P2P system, SOMCO route algorithm is better on the route efficiency, network load and network adaptability, is more suitable for applying into distributed internet telephony system.