The Implementation Of P2P In VoIP

With the development of Internet mode and popularization of the broadband access, Internet phone, as a new optional communication tool, gets more and more attracted, for its high quality and low price, also all kinds of added-value service. P2P and SIP are two of those most popular technologies at present. There are not any centralized servers in a P2P system. The P2P system's self-organization, high scalability, robustness and fault tolerance features bring a revolution of compute pattern to the whole IT world. At the same time, SIP protocol is also becoming more and more popular both in the current Internet communication systems and IT industries. How to combine these two technologies together and make use of their advantages is an important goal for many research institutes. This paper will do a widely discussion on it.Firstly, the paper explains the SIP (Session Initiation Protocol) from three points: the SIP servers, the protocol framework and the message format and introduces the P2P (Peer-to-Peer) technology and analyzes the popular four network topologies and the Chord algorithm in base of DHT.Then, based on the two possible modes of combination of SIP and P2P, we make the design of this P2P-SIP system. The node of this P2P-SIP system and the design of user function are introduced too.Furthermore, we make four modules to implement the system: NAT module, SIP module, Chord module and voice module. The paper introduces the partition of the modules and implementation in detail.Lastly, we measure and compare the login time, call-setup time, call-cancel time, call-delay time and the ratio of packet loss between the P2P-SIP and Skype system in the two condition: public network and network with firewall and analyze the result.