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Cisco SIP IP Phone 7960 Administrator Guide
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Appendix B SIP Call Flows
Call Flow Scenarios for Successful Calls
5
486 Busy Here—Cisco SIP IP
phone B to SIP proxy server
Cisco SIP IP phone B sends a 486 Busy here message to the
SIP proxy server. The message indicates that Cisco SIP IP
phone B is in use and the user is not willing or able to take
additional calls.
6
ACK—SIP proxy server to Cisco
SIP IP phone B
SIP proxy server forwards the SIP ACK to the Cisco SIP IP
phone B. The ACK confirms that the SIP proxy server has
received the 486 Busy here response from Cisco SIP IP
phone B.
7
INVITE—SIP proxy server to
Cisco SIP IP phone C
SIP proxy server sends a SIP INVITE request to Cisco SIP
IP phone C. The INVITE request is an invitation to User C
to participate in a call session.
8
180 Ringing—Cisco SIP IP
phone C to SIP proxy server
Cisco SIP IP phone C sends a SIP 180 Ringing response to
the SIP proxy server
9
200 OK—Cisco SIP IP phone C
to SIP proxy server
Cisco SIP IP phone C sends a SIP 200 OK response to the
SIP proxy server.
10
200 OK—SIP proxy server to
Cisco SIP IP phone A
SIP proxy server forwards the SIP 200 OK response to
Cisco SIP IP phone A.
11
ACK—Cisco SIP IP phone A to
SIP proxy server
Cisco SIP IP phone A sends a SIP ACK to the SIP proxy
server. The ACK confirms that Cisco SIP IP phone A has
received the 200 OK response from Cisco SIP IP phone C.
12
ACK—SIP proxy server to Cisco
SIP IP phone C
SIP proxy server forwards the SIP ACK to the Cisco SIP IP
phone C. The ACK confirms that Cisco SIP IP phone A has
received the 200 OK response from Cisco SIP IP phone C.
Step Action Description