Design and implementation of SIP B2BUA server

The SIP(Session Initiation Protocol) is the core control protocol of the Next Generation Networks(NGN), which is used for initiating, modifying and tearing down multimedia sessions on IP data network. Because the SIP server is the core facility of NGN, its realization is especially important. One way to realize the SIP server is the proxy server, which mainly provides routing service. Namely, it ensures that request message will be sent to place that is closest to target user. However, the proxy server just keeps the state during the SIP interaction instead of the state during call process, which causes that the proxy server is limited to be used in more wide range. Another way is the B2BUA server, which keeps the state during the whole call process. So, at first, the Resiprocate is introduced from the basic principle of the SIP protocol in this paper, and the B2BUA server is realized. Then, taking advantage of the advantage of the B2BUA server, the group call system based on the B2BUA server is realized. At last, this paper use the SIPp, a open software which is specially used to test the SIP system, to test and analysis the performance of the B2BUA server.