Refer to the exhibit. Which SIP message will trigger the calling device to open channels for early media reception?
A. 180 Ringing
B. ACK
C. INVITE
D. 183 session-progress
E. 200 OK
Refer to the exhibit. Which SIP message will trigger the calling device to open channels for early media reception?
A. 180 Ringing
B. ACK
C. INVITE
D. 183 session-progress
E. 200 OK