D-7
Cisco ATA 186 and Cisco ATA 188 Analog Telephone Adaptor Administrator’s Guide (SIP)
OL-3410-01
AppendixD SIP Call Flows
Call Flow Scenarios for Successful Calls
TableD-5 Action Descriptions
Step Action Description
Step1 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.
Step2 100 Trying—SIP server to Cisco ATA A SIP server returns a 100 trying message, indicating that the
INVITE request has been received.
Step3 INVITE—SIP server to Cisco ATA B SIP server sends the call session INVITE request to Cisco ATA B.
Step4 100 Trying—Cisco ATA B to SIP server CiscoATA B returns a 100 trying message indicating that the
INVITE request has been received.
Step5 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.
Step6 180 Ringing—SIP server to Cisco ATA A SIP server sends the 180 ringing response to Cisco ATA A.
Step7 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.
Step8 200 OK—SIP server to Cisco ATA A SIP server passes the 200 OK message to CiscoATA A.
Step9 ACK—Cisco ATA A to SIP server Cisco ATA A sends acknowledgement of the 200 OK response to
the SIP server to pass on to Cisco ATA B.
Step10 ACK—SIP server to Cisco ATA B SIP server passes ACK response to CiscoATA B.
A two-way voice path is established between CiscoATA A and Cisco ATA B.
Step11 BYE—Cisco ATA A to SIP server C isco ATA A terminates the call session and sends a BYE request
to the SIP server indicating that CiscoATA A wants to terminate
the call.
Step12 100 Trying—SIP server to Cisco ATA A SIP server returns a 100 trying message indic ating that the BYE
request has been received.
Step13 BYE—SIP server to Cisco ATA B SIP server passes the BYE request to Cisco ATA B.
Step14 200 OK—Cisco ATA B to SIP server Cisco ATA B sends a 200 OK message to the SIP server
indicating that CiscoATA B has received the BYE request.
Step15 200 OK—SIP server to Cisco ATA A SIP server passes the BYE request to Cisco ATA A.