Cisco 7960G Administrator's Manual page 126
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Also See for 7960G:
- Administration manual (184 pages) ,
- User manual (122 pages) ,
- Phone manual (74 pages)
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Call Flow Scenarios for Successful Calls
Step
Action
9.
INVITE—Phone B to Phone C
10.
100 Trying—Phone C to Phone B
11.
180 Ringing—Phone C to Phone B Phone C sends a SIP 180 Ringing response to Phone B.
200 OK—Phone C to Phone B
12.
ACK—Phone B to Phone C
13.
A two-way RTP channel is established between Phone B and Phone C.
User B then selects the option to transfer the call to User C.
INVITE—Phone B to Phone A
14.
200 OK—Phone A to Phone B
15.
ACK—Phone B to Phone C
16.
REFER—Phone B to Phone A
17.
501 Not Implemented—Cisco SIP
18.
IP Phone A to Cisco SIP IP
Phone B
BYE—Phone B to Phone A
19.
Cisco SIP IP Phone Administrator Guide, Release 6.x and 7.x
B-30
Description
Phone B sends a SIP INVITE request to Phone C. The request is an invitation
to User C to participate in a call session.
Phone C sends a SIP 100 Trying response to Phone B. The response indicates
that the INVITE request has been received.
Phone C sends a SIP 200 OK response to Phone B. The response notifies
Phone B that the connection has been made.
If Phone B supports the media capability advertised in the INVITE message
sent by Phone A, it advertises the intersection of its own and Phone A's media
capability in the 200 OK response. If Phone B does not support the media
capability advertised by Phone A, it sends back a 400 Bad Request response
with a 304 Warning header field.
Phone B sends a SIP ACK to Phone C. The ACK confirms that Phone B has
received the 200 OK response from Phone C.
The ACK might contain a message body with the final session description to be
used by Phone C. If the message body of the ACK is empty, Phone C uses the
session description in the INVITE request.
Phone B sends a midcall INVITE to Phone A with new SDP session parameters
(IP address), which are used to place the call on hold.
Call_ID=1
SDP: c=IN IP4 0.0.0.0
The c= SDP field of the SIP INVITE contains an 0.0.0.0. This places the call in
hold.
Phone A sends a SIP 200 OK response to Phone B.
Phone B sends a SIP ACK to Phone C. The ACK confirms that Phone B has
received the 200 OK response from Phone C.
Phone B sends a REFER message to Phone A. The message contains the
following information:
Refer-To: C
•
Replaces: B
•
Referred-By: B
•
The message indicates that the user (recipient) should contact a third party for
use in transferring parties.
Phone A sends a 501 Not Implemented message to Phone B. The message
indicates that the REFER message is not supported and that Phone B should
failover to Bye/Also.
Phone B sends a BYE message to Phone A. The message includes the following
information:
Also: C
•
The message indicates that the 501 Not Implemented message was received in
response to a REFER message.
Appendix B
SIP Call Flows
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