sip，sdp，sap之间的关系。以及应用。非常好的理解sip的一篇文摘-sip, sdp, the relationship between sap. , And applications. Sip a very good understanding of a CAS

SIP是IETF致力于将电话服务带入IP网络众多协议的一个组成部分（它与SDP、RTP、RTCP、RTSP、RSVVP、TRIP等众多协议构成SIP系统协议栈）. 这是sip协议栈实现最新版， 可用于开开发sip客户端/代理/服务器 -SIP is the IETF committed an integral part of many protocols into the IP network telephone service (which many agreements with the