说明：  “会话发起协议(Session Initiation Protocol-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。”
(" Session Initiation Protocol (Session Initiation Protocol-SIP) is an application layer control protocol signaling. To create, modify, and terminate one or more participants in the session. These sessions can be Internet multimedia conferencing, IP phones or multimedia distribution (example: voice mail). multicast session by the participants (multicast), mesh unicast (unicast) or a mixture of the two to communicate. " )