The Research Of Softphone System Based On P2PSIP

The technology of SIP is one trend of development in VoIP, but it has one of hardest problems: the framework on C/S makes hard load balance in central server and can't assure the quality of communication in application.After analyzing the technology of P2P, there is a good method to solve the problem by combining the P2P and SIP.It can improve self-management,extensibility and robustness of the network.The most domestic and foreign teaching and studying institutions study VoIP on P2PSIP deeply. However many researches and realizations were achieved by Chord on UNIX(Linux).So the author presented a Softphone system for realizing some function based on P2PSIP by Kademlia on Windows.This paper analyzed the topology structure of P2P in detail.In the aspect of SIP message, the author analyzed the protocol and combined with the SIP software of X-Lite which based on C/S structure for studying the realization of SIP.After analyzing the draft P2PSIP protocol, the author compared some DHT algorithms.As the result of that Kademlia is based on symmetrical XOR metric,it has some advantages such as:requests of search have available messages,decreasing the distance between source note and aimed note and so on.So that the author selected Kademlia as the algorithm which used at P2P in this system.Meanwhile it researched those Kademlia procedures in EMULE which realizes Kademlia algorithm successfully.At last,it presented Softphone system.The system used Kademlia for constructing P2P Overlay ,the Overlay included some supernodes,bootstrap nodes and regedit nodes. Transmiting SIP message on the Overlay.The system had good performances which were tested in extensibility, effience of updating, heterogeneity and fault tolerant.