This figure shows the call flow messages between, from right to left, a Client Application, Signaling Engine, a SIP Proxy, and a SIP Phone. The message include:
Client to Signaling Engine: handshake.
Signaling Engine to Client: handshake response.
Client to Signaling Engine: connect
.
Signaling Engine to SIP Proxy: register
.
SIP Proxy to Signaling Engine: 200/OK
.
Signaling Engine to Client: connect
response.
Signaling Engine to SIP Proxy: REGISTER
.
SIP Proxy to Signaling Engine: 200/OK
.
Signaling Engine to Client: connect
/response.
SIP Phone to SIP Proxy: INVITE
.
The SIP Proxy starts a SIP session by sending an INVITE
to Signaling Engine.
Signaling Engine to Client: start
which starts a subsession.
Signaling Engine to SIP Proxy: 100
/trying.
Client to Signaling Engine: start
/initial response.
Signaling Engine to SIP Proxy: 180
/Calling.
Client to Signaling Engine: start
/final response.
Signaling Engine to SIP Proxy: 200/OK
.
SIP Proxy to Signaling Engine: ACK
.
Signaling Engine to Client: complete
.
The media session then opens between the Client and the SIP Proxy.
SIP Proxy to Signaling Engine: BYE
.
Signaling Engine to Client: shutdown
which shuts down the subsession and WebSocket.
Signaling Engine to SIP Proxy: 200/OK
, which ends the SIP session.