Based On P2p Sip Session

The appearnce of the P2P(peer-to-peer) network technology have greatly changed the manner of network services, such as Files Sharing, Instant Message, Distributed Storage, Distributed Computing and Streaming Media. The systems those based on P2P have the characters that high reliability, high expansibility and high tolerance. And they are also excellent at evolution speed. In these systems, the servers are not master any longer. Instead, many individuals join together and play the most important role. SIP, which was developed several years ago, is the controlling protocol of VoIP. It meant to offer a service of network-phone. The SIP is very easy to be expanded. While developing the SIP protocol, people took the idea of P2P into account. But, the SIP system is not a pure P2P network. So, when the SIP system became bigger and bigger, the problems came-performance and expansibility.The topology of P2P network can be divided into three kinds. The first is central topology, the second is pure distributed topology and the third is intergradation of the first and the second. The second topology, pure distributed topology, can be divided into two kinds, the structural and no-structrual. The topology which is pure distributed and structural sustains ordinal and right search, and network phone system need Qos, so the pure distributed structural topology fits to be the base of SIP system. In this paper, the writer introduces four P2P systems which have the pure distributed structural topology. They are Chord, CAN, Tapestry and Pastry, and Pastry is chosen to be the base of SIP systems. This SIP system is called P2P-SIP. In P2P-SIP systems, users register their information onto other peers according to one special mechanism. Every peer of P2P-SIP needs to have the function of client and servers in traditional SIP system. When one wants to communicate with the other one, it first gets peer which have the other peer's information and consider it as the server in this communication. The other processes are the same as traditional SIP system. In P2P-SIP system, Pastry adopts the prefix-match arithmetic. This characteristic is used to construct the multi-broadcast tree that bases on content. The multi-broadcast tree is better than IP multicast which is used in traditional SIP system when launch a phone conference. In P2P-SIP systems, users register their information on others peers, so the security is also a very important. This paper introduces the public-key mechanism to assure the security of communication content. The other problem of P2P-SIP is how to be compatible with the traditional SIP system. Some special peers are designed to solve this problem in this paper.