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Cisco Unified IP Phone 7960G and 7940G Administration Guide for Release 8.0 (SIP)
OL-7890-01
Appendix B SIP Call Flows
Call Flow Scenarios for Successful Calls
Figure B-1
Successful Setup and Disconnect
Step
Action
Description
1.
Setup—PBX A to Gateway 1
Call setup is initiated between PBX A and Gateway 1. Setup includes
the standard transactions that take place as User A attempts to call
User B.
2.
INVITE—Gateway 1 to Cisco SIP IP phone
Gateway 1 maps the SIP URL phone number to a dial peer. The dial
peer includes the IP address and the port number of the SIP-enabled
entity to contact. Gateway 1 sends a SIP INVITE request to the
address it receives as the dial peer, which, in this scenario, is the IP
phone. In the INVITE request:
•
The IP address of the phone is inserted in the Request-URI field.
•
PBX A is identified as the call session initiator in the From field.
•
A unique numeric identifier is assigned to the call and is inserted
in the Call-ID field.
•
The transaction number within a single call leg is identified in the
CSeq field.
•
The media capability that User A is ready to receive is specified.
•
The port on which the gateway is prepared to receive the RTP
data is specified.
3.
Call Proceeding—Gateway 1 to PBX A
Gateway 1 sends a Call Proceeding message to PBX A to
acknowledge the Call Setup request.
IP
3. Call Proceeding
6. Alerting
8. Connect
12. Disconnect
1. Setup
PBX A
SIP IP Phone
User B
User A
GW1
IP Network
4. 100 Trying
11. BYE
5. 180 Ringing
7. 200 OK
2. INVITE
2-way RTP channel
2-way voice path
10. ACK
14. 200 OK
9. Connect ACK
13. Release
15. Release Complete
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