P2P Communication Based On SIP And Research Of Firewall Traversing

Recently, VoIP (Voice over IP) has become a hot topic in the communication and Internet fields. And IP telephony has become one of the most competitive technical because of its economic and efficient. Most VoIP softphone adopt the Client/Server network model, every service is centered on servers and based on its normal operation in the manner. Ability of server is bound to be a bottleneck of the whole network by increasing user. The emergence of P2P technology will fundamentally subvert the traditional Client/Server model, and completely get rid off the restraint of server. There is no centralized server in P2P network, and each node is an information consumer, but also an information provider, the rights and obligations of node are equal. So P2P systems inherently have high scalability, robustness and fault tolerance. The prevailing Skype connects and organise all the resources of users by P2P technology. However, it implements a private protocol which is not published.Result from the above, we design a feasible P2P communications models following SIP protocol and using Chord as the underlying routing algorithm. In addition, since almost users are behind the firewall and Nat, we deal with the problem of travesing Nat using ICE method.First, the paper summarizes the P2P technology, analyze the network of Skype and the Chord algorithm; Next design the network model based on Skype. Further, presents the architecture of our P2P systerm. it also discusses the advantages and disadvantages between our P2P system, Skype and traditional telephone; In order to implement P2P communication, it designs P2P message by extending the standard SIP message, and detailedly describes the message flow in a simple network environment; The last chapter of the paper introduces the overall design and concrete implementation in P2P communication, the result of the test indicates that the capability of the solution is good and strong.