Cisco SIP IP Phone User Manual

B-16
Cisco SIP IP Phone Administrator Guide
AppendixB SIP Call Flows
Call Flow Scenarios for Successful Calls
7. 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 0.0.0.0. This places the call in hold.
8. 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.
9. 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.
The RTP channel between Cisco SIP IP phone A and Cisco SIP IP phone B is torn down.
10. 200 OK—Cisco SIP IP phone B
to Cisco SIP IP phone C
Cisco SIP IP phone B sends a SIP 200 OK response to Cisco SIP IP phone C. The
200 OK response notifies Cisco SIP IP phone C that the connection has been
made.
11. ACK—Cisco SIP IP phone C to
Cisco SIP IP phone B
Cisco SIP IP phone C sends a SIP ACK to Cisco SIP IP phone B. The ACK
confirms that Cisco SIP IP phone C has received the 200 OK response from
Cisco SIP IP phone B.
The ACK might contain a message body with the final session description to be
used by Cisco SIP IP phone B. If the message body of the ACK is empty,
Cisco SIP IP phone B 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.
12. INVITE—Cisco SIP IP phone B
to Cisco SIP IP phone C
Cisco SIP IP phone B sends a mid-call INVITE to Cisco SIP IP phone C with
new SDP session parameters (IP address), which are used to place the call on
hold.
Call_ID=2
SDP: c=IN IP4 0.0.0.0
To establish the call between phone B and phone C, the IP address of phone B is
inserted into the c= SDP field.
13. 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.
14. 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 RTP channel between Cisco SIP IP phone B and Cisco SIP IP phone C is torn down.
15. 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 the
same call ID as the previous INVITE (sent to Cisco SIP IP phone A) and new
SDP session parameters (IP address), which are used to reestablish the call.
Call_ID=1
SDP: c=IN IP4 181.23.250.2
16. 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.
Step Action Description

Cisco SIP IP Phone Specifications

General

Brand	Cisco
Model	SIP IP Phone
Category	IP Phone
Language	English