SIP是一个应用层的信令控制协议，用于创建、修改和终止一个或多个参与者的会话。这些会话可以是Internet多媒体会议、IP电话或多媒体分发（例如语音信箱）。会话的参与者可以通过组播(multicast)、网状单播(unicast)或两者的混合体进行通信。更为详细的SIP介绍，可参考相关的网站和书籍，如SIP FORUM等-SIP is an application-layer control protocol signaling for creating, modification and termination of one or more participants in the conversation. These sessions can be multimedia Internet, IP telephony and multimedia distribution (such as voice mail). Session participants through multicast (multicast), mesh unicast (Unicast), or a combination of both mass communications. More detailed SIP, can refer to the relevant Web sites and books, such as SIP FORUM