SIP协议是NGN中的重要协议，是一个基于文本的应用层控制协议，独立于底层传输协议TCP/UDP/SCTP，用于建立、修改和终止IP网上的双方或多方多媒体会话。-NGN SIP protocol is an important protocol is a text-based application-layer control protocol, independent of the underlying transport protocols TCP/UDP/SCTP, for creating, modifying and terminating IP network multimedia sessions two or more parties