| The Session Initial Protocol which is proposed by IETF has got support of lots of companies and became the chief signaling protocol of VoIP since its advantages of simplicity,flexibility and scalability.But along with the high-speed increase of users, the SIP system has got the problems of single point of failure and performance bottleneck because of its C/S architecture.P2P systems inherently have high scalability,robustness and fault tolerance because there is no centralized server and the network self-organizes itself.P2P technology becomes one of the main way to solve the problems mentioned above.So researches on how to combine SIP with P2P efficiently become very significant.This article first analyzes the key technologies of VoIP,especially emphasis on the calling flow of SIP.And then we have a deeply study on the P2P technology.After doing comparison with the four classical structured P2P algorithm,we choose Kademlia as our routing algorithm,and a P2P-SIP model based on it is designed to fit our VoIP system.Then according to the P2P-SIP model and taking portability and reusability as based principle,the article proposed a layered architecture for the P2P-SIP VoIP system and realized it on Winodws operating system.The testing result shows that the system works stably and has good Qos performance.The characteristics and innovations in this article are as follows:(1) A VoIP system based on P2P-SIP technology is designed and implemented. The system supports both C/S and P2P communication model.(2) The delay of user location is greatly reduced because we use improved Kademlia as the routing algorithm.(3) Using module programming method to support portability and reusability. |
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