Cisco SIP IP Phone User Manual

B-34
Cisco SIP IP Phone Administrator Guide
AppendixB SIP Call Flows
Call Flow Scenarios for Successful Calls
17. REFER—Cisco SIP IP phone B
to Cisco SIP IP phone A
Cisco SIP IP phone B sends a REFER message to Cisco SIP IP phone A. The
REFER message contains the following information:
• Refer-To: C
• Replaces: B
• Referred-By: B
The REFER message indicates that the user (recipient) should contact a third
party for use in transferring parties.
18. 501 Not Implemented—
Cisco SIP IP Phone A to
Cisco SIP IP Phone B
Cisco SIP IP phone A sends a 501 Not Implemented message to Cisco SIP IP
phone B. This message indicates that the REFER message is not supported and
that Cisco SIP IP phone B should failover to Bye/Also.
19. BYE—Cisco SIP IP phone B to
Cisco SIP IP phone A
Cisco SIP IP phone B sends a BYE message to Cisco SIP IP phone A. The BYE
message includes the following information:
• Also: C
This message indicates that the 501 Not Implemented message was received in
response to a REFER message.
20. 200 OK—Cisco SIP IP phone A
to Cisco SIP IP phone B
Cisco SIP IP phone A sends a SIP 200 OK message to Cisco SIP IP phone B. The
200 OK response notifies Cisco SIP IP phone B that the BYE request has been
received.
21. BYE—Cisco SIP IP phone B to
Cisco SIP IP phone C
Cisco SIP IP phone B sends a SIP BYE request to Cisco SIP IP phone C.
22. 200 OK—Cisco SIP IP phone C
to Cisco SIP IP phone B
Cisco SIP IP phone C sends a SIP 200 OK message to Cisco SIP IP phone B. The
200 OK response notifies Cisco SIP IP phone B that the BYE request has been
received.
23. INVITE—Cisco SIP IP phone A
to Cisco SIP IP phone C
Cisco SIP IP phone A sends a SIP INVITE request to Cisco SIP IP phone C. The
INVITE request contains the following information:
• Requested-By: B
This message indicates that the INVITE was requested by Cisco SIP IP phone B.
24. 100 Trying—Cisco SIP IP phone
C to Cisco SIP IP phone A
The Cisco SIP IP phone C sends a SIP 100 Trying response to Cisco SIP IP phone
A. The 100 Trying response indicates that the INVITE request has been received
by Cisco SIP IP phone C.
25. 180 Ringing—Cisco SIP IP
phone C to Cisco SIP IP phone A
Cisco SIP IP phone C sends a SIP 180 Ringing response to Cisco SIP IP phone A.
26. 200 OK—Cisco SIP IP phone C
to Cisco SIP IP phone A
Cisco SIP IP phone C sends a SIP 200 OK response to Cisco SIP IP phone A. The
200 OK response notifies Cisco SIP IP phone A that the connection has been
made.
27. ACK—Cisco SIP IP phone A to
Cisco SIP IP phone C
Cisco SIP IP phone A sends a SIP ACK to Cisco SIP IP phone C. The ACK
confirms that Cisco SIP IP phone A has received the 200 OK response from
Cisco SIP IP phone C.
A two-way RTP channel is established between Cisco SIP IP phone A and Cisco SIP IP phone C.
Step Action Description

Cisco SIP IP Phone Specifications

General

Brand	Cisco
Model	SIP IP Phone
Category	IP Phone
Language	English