Cisco SIP IP Phone User Manual

B-28
Cisco SIP IP Phone Administrator Guide
AppendixB SIP Call Flows
Call Flow Scenarios for Successful Calls
7. 200 OK—Cisco SIP IP phone A
to Cisco SIP IP phone B
Cisco SIP IP phone A sends a SIP 200 OK response to Cisco SIP IP phone B.
8. ACK—Cisco SIP IP phone B to
Cisco SIP IP phone A
Cisco SIP IP phone B sends a SIP ACK to Cisco SIP IP phone A. The ACK
confirms that Cisco SIP IP phone B has received the 200 OK response from
Cisco SIP IP phone A.
User B dials User C.
9. INVITE—Cisco SIP IP phone B
to Cisco SIP IP phone C
Cisco SIP IP phone B sends a SIP INVITE request to Cisco SIP IP phone C. The
INVITE request is an invitation to User C to participate in a call session.
10. 100 Trying—Cisco SIP IP phone
C to Cisco SIP IP phone B
The Cisco SIP IP phone C sends a SIP 100 Trying response to Cisco SIP IP phone
B. The 100 Trying response indicates that the INVITE request has been received
by Cisco SIP IP phone C.
11. 180 Ringing—Cisco SIP IP
phone C to Cisco SIP IP phone B
Cisco SIP IP phone C sends a SIP 180 Ringing response to Cisco SIP IP phone B.
12. 200 OK—Cisco SIP IP phone C
to Cisco SIP IP phone B
Cisco SIP IP phone C sends a SIP 200 OK response to Cisco SIP IP phone B. The
200 OK response notifies Cisco SIP IP phone B that the connection has been
made.
If Cisco SIP IP phone B supports the media capability advertised in the INVITE
message sent by Cisco SIP IP phone A, it advertises the intersection of its own
and Cisco SIP IP phone A’s media capability in the 200 OK response. If
Cisco SIP IP phone B does not support the media capability advertised by
Cisco SIP IP phone A, it sends back a 400 Bad Request response with a 304
Warning header field.
13. ACK—Cisco SIP IP phone B to
Cisco SIP IP phone C
Cisco SIP IP phone B sends a SIP ACK to Cisco SIP IP phone C. The ACK
confirms that Cisco SIP IP phone B has received the 200 OK response from
Cisco SIP IP phone C.
The ACK might contain a message body with the final session description to be
used by Cisco SIP IP phone C. If the message body of the ACK is empty,
Cisco SIP IP phone C uses the session description in the INVITE request.
A two-way RTP channel is established between Cisco SIP IP phone B and Cisco SIP IP phone C.
User B then selects the option to transfer the call to User C.
14. INVITE—Cisco SIP IP phone B
to Cisco SIP IP phone A
Cisco SIP IP phone B sends a mid-call INVITE to Cisco SIP IP 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.
15. 200 OK—Cisco SIP IP phone A
to Cisco SIP IP phone B
Cisco SIP IP phone A sends a SIP 200 OK response to Cisco SIP IP phone B.
16. ACK—Cisco SIP IP phone B to
Cisco SIP IP phone C
Cisco SIP IP phone B sends a SIP ACK to Cisco SIP IP phone C. The ACK
confirms that Cisco SIP IP phone B has received the 200 OK response from
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