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D-13
Cisco ATA 186 and Cisco ATA 188 Analog Telephone Adaptor Administrator’s Guide (SIP)
OL-3410-01
Appendix D SIP Call Flows
Call Flow Scenarios for Successful Calls
Table D-7 Action Descriptions
Step Action Description
Step 1
INVITE—Cisco ATA A to SIP server Cisco ATA A sends a call session INVITE request to the SIP
server to pass on to Cisco ATA B.
Step 2
100 Trying—SIP server to Cisco ATA A SIP server returns a 100 Trying message, indicating that the
INVITE request has been received.
Step 3
407 Proxy Authentication Required— SIP server
to Cisco ATA A
SIP server returns a request for authentication to Cisco ATA A.
Step 4
ACK—Cisco ATA A to SIP server Cisco ATA A acknowledges the request for authentication.
Step 5
INVITE—Cisco ATA A to SIP server Cisco ATA A sends a call session INVITE request along with
authentication credential to the SIP server to pass on to
Cisco ATA B.
Step 6
100 Trying—SIP server to Cisco ATA A SIP server returns a 100 Trying message, indicating that the
INVITE request has been received.
Step 7
INVITE—SIP server to Cisco ATA B SIP server sends the call session INVITE request to Cisco ATA
B.
Step 8
100 Trying—Cisco ATA B to SIP server Cisco ATA B returns a 100 trying message indicating that the
INVITE request has been received.
Step 9
180 Ringing—Cisco ATA B to SIP server Cisco ATA B sends a 180 ringing response to the SIP server to
pass on to Cisco ATA A.
Step 10
180 Ringing—SIP server to Cisco ATA A SIP server sends the 180 ringing response to Cisco ATA A.
Step 11
200 OK—Cisco ATA B to SIP server Cisco ATA B sends a 200 OK message to the SIP server
indicating that a connection has been established.
Step 12
200 OK—SIP server to Cisco ATA A SIP server passes the 200 OK message to Cisco ATA A.
Step 13
ACK—Cisco ATA A to SIP server Cisco ATA A sends acknowledgment of the 200 OK response to
the SIP server to pass on to Cisco ATA B.
Step 14
ACK—SIP server to Cisco ATA B SIP server passes ACK response to Cisco ATA B.
A two-way voice path is established between Cisco ATA A and Cisco ATA B.
Step 15
BYE—Cisco ATA A to SIP server Cisco ATA A terminates the call session and sends a BYE
request to the SIP server indicating that Cisco ATA A wants to
terminate the call.
Step 16
100 Trying—SIP server to Cisco ATA A SIP server returns a 100 trying message indicating that the BYE
request has been received.
Step 17
BYE—SIP server to Cisco ATA B SIP server passes the BYE request to Cisco ATA B.
Step 18
200 OK—Cisco ATA B to SIP server Cisco ATA 186 B sends a 200 OK message to the SIP server
indicating that Cisco ATA 186 B has received the BYE request.
Step 19
200 OK—SIP server to Cisco ATA A SIP server passes the BYE request to Cisco ATA A.