Cisco 7905G Administrator's Manual page 191

Appendix C SIP Call Flows
Table C-5 Action Descriptions
Step Action
Step 1
INVITE—Cisco IP Phone A to SIP server
Step 2
100 Trying—SIP server to Cisco IP Phone A SIP server returns a 100 trying message,
Step 3
INVITE—SIP server to Cisco IP Phone B
Step 4
100 Trying—Cisco IP Phone B to SIP server Cisco IP Phone B returns a 100 trying
Step 5
180 Ringing—Cisco IP Phone B to SIP
server
Step 6
180 Ringing—SIP server to Cisco IP Phone
A
Step 7
200 OK—Cisco IP Phone B to SIP server
Step 8
200 OK—SIP server to Cisco IP Phone A
Step 9 ACK—Cisco IP Phone A to SIP server
Step 10
ACK—SIP server to Cisco IP Phone B
A two-way voice path is established between Cisco IP Phone A and Cisco IP Phone B.
Step 11 BYE—Cisco IP Phone A to SIP server
OL-4277-01
Description
Cisco IP Phone A sends a call session
INVITE request to the SIP server to pass on to
Cisco IP Phone B.
indicating that the INVITE request has been
received.
SIP server sends the call session INVITE
request to Cisco IP Phone B.
message indicating that the INVITE request
has been received.
Cisco IP Phone B sends a 180 ringing
response to the SIP server to pass on to
Cisco IP Phone A.
SIP server sends the 180 ringing response to
Cisco IP Phone A.
Cisco IP Phone B sends a 200 OK message to
the SIP server indicating that a connection has
been established.
SIP server passes the 200 OK message to
Cisco IP Phone A.
Cisco IP Phone A sends acknowledgement of
the 200 OK response to the SIP server to pass
on to Cisco IP Phone B.
SIP server passes ACK response to
Cisco IP Phone B.
Cisco IP Phone A terminates the call session
and sends a BYE request to the SIP server
indicating that Cisco IP Phone A wants to
terminate the call.
Cisco IP Phone Models 7905G and 7912G Administrator Guide (SIP)
Call Flow Scenarios for Successful Calls
C-9