Call Waiting - Cisco 7960G Administration Manual

Call Flow Scenarios for Successful Calls
Step Action
200 OK—Phone C to Phone B
10.
11. ACK—Phone B to Phone C
A two-way RTP channel is established between Phone B and Phone C.
BYE—Phone B to Phone C
12.
200 OK—Phone C to Phone B
13.
The RTP channel between Phone B and Phone C is torn down.
INVITE—Phone B to Phone A
14.
200 OK—Phone A to Phone B
15.
ACK—Phone B to Phone A
16.
A two-way RTP channel is reestablished between Phone A and Phone B.

Call Waiting

Figure B-6
and one of the participants receives a call from a third party and then returns to the original call. In this
call flow scenario, the end users are User A, User B, and User C. They are all using
Cisco IP Phone 7960G/7940G, which are connected using an IP network.
The call flow scenario is as follows:
1.
2.
3.
4.
5.
6.
7.
8.
Cisco Unified IP Phone 7960G and 7940G Administration Guide for Release 8.0 (SIP)
B-14
Description
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.
The call continues and then User B hangs up. Phone B sends a SIP BYE
request to Phone C. The request indicates that User B wants to release the
call.
Phone C sends a SIP 200 OK response to Phone B. The response notifies
Phone B that the BYE request has been received. The call session between
User A and User B terminates.
User B takes User A off hold. Phone B sends a SIP INVITE request to
Phone A with the same call ID as the previous INVITE and a new SDP
attribute parameter (sendrecv), which is used to reestablish the call.
Phone A sends a SIP 200 OK response to Phone B.
Phone B sends a SIP ACK to Phone A. The ACK confirms that Phone B has
received the 200 OK response from Phone A.
illustrates a successful call between Cisco SIP IP phones in which two parties are in a call,
User A calls User B.
User B answers the call.
User C calls User B.
User B accepts the call from User C.
User B switches back to User A.
User B hangs up, ending the call with User A.
User B is notified of the remaining call with User C.
User B answers the notification and continues the call with User C.
Appendix B SIP Call Flows
OL-7890-01