说明：  SIP是一种应用层控制协议，可以建立，修改和终止多媒体会话（会议），例如互联网电话呼叫。SIP还可以邀请参与者访问现有会话，例如多播会议。通常，SIP使用UDP和TCP端口5060和TCP 5061进行SSL通信。SIP协议与HTTP非常相似，因此如果您对HTTP有一些了解，那么很容易学习SIP。SIP不传输会话数据，如音频，视频。使用RTP（实时协议），SIP只是帮助打开RTP流。
(SIP can also invite participants to access existing sessions, such as multicast meetings. Generally, SIP uses UDP and TCP port 5060 and TCP 5061 for SSL communication. SIP protocol is very similar to HTTP, so if you have some knowledge of HTTP, it's easy to learn SIP. SIP does not transmit session data, such as audio and video. Using RTP (Real-time Protocol), SIP only helps open RTP streams.)