What in SIP signaling indicates the action to be completed by the signaling?

The INVITE transaction represents a call, bye represents the end of the call, and register represents registration to the server.

SIP (Session Initiation Protocol) is a multimedia communication protocol developed by the IETF (Internet Engineering Task Force). It is a text-based application layer control protocol used to create, modify and release sessions with one or more participants. It is widely used in CS (Circuit Switched, circuit switching), NGN (Next Generation Network, next generation network) and IMS (IP Multimedia Subsystem, IP multimedia subsystem) networks, and can support and be applied to multimedia such as voice, video, and data. business, and can also be applied to specialty services such as Presence and Instant Message. It can be said that wherever there is an IP network, the SIP protocol exists.

SIP is similar to HTTP. SIP can reduce the development time of applications, especially advanced applications. Since SIP based on the IP protocol utilizes the IP network, fixed network operators will gradually realize the far-reaching significance of SIP technology to them.