SIP implements a three-way handshake.
If the first INVITE message includes a SDP call description, the 200OK includes the callee's SDP.
- The caller sends an INVITE
- The callee sends an 200 OK to accept the call
- The caller sends an ACK to indicate that the handshake is done and a call is going to be setup
If the first INVITE message includes a SDP call description, the 200OK includes the callee's SDP.
Comments
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- The caller sends and INVITE
- The callee sends a 200 OK to accept the call
- The caller sends and ACK to acknowledge the 200 OK and setup the call, thus completing the handshake