Cisco 7960 Administrator's Manual page 161

Appendix B SIP Call Flows
Figure B-12 Cisco SIP IP Phone-to Cisco SIP IP Phone 3-Way Calling
IP
SIP IP
Phone
User A
1. INVITE B (Call-ID=1)
2. 180 Ringing
3. 200 OK
4. ACK
2-way RTP channel 1 between Users A and B established
5. INVITE (Call-ID=1, c=IN IP40.0.0.0)
6. 200 OK
7. ACK
User A is on hold. The RTP channel 1 between User A and B is torn down.
12. INVITE A (Call-ID=1, c=IN IP4 IP-User B)
13. 200 OK
User A is taken off hold. The RTP channel 1 between User A and B
is re-established.
User B mixes the RTP channels 1 and 2 and establishes a conference brigde between Users A and C
78-10497-02
IP Network
Proxy Redirect
Server Server
Call Flow Scenarios for Successful Calls
IP
SIP IP
Phone
User B
8. INVITE C (Call-ID=2)
9. 180 Ringing
10. 200 OK
11. ACK
2-way RTP channel 2
between User B and
C is established
Cisco SIP IP Phone 7960 Administrator Guide
IP
SIP IP
Phone
User C
B-53