Client, Server, Or Global Error - Cisco 7960G Administrator's Manual

Call Flow Scenarios for Failed Calls
Step Action
Setup—PBX A to Gateway 1
1.
INVITE—Gateway 1 to Cisco SIP IP
2.
phone
3. Call Proceeding—Gateway 1 to PBX A
4. 100 Trying—Cisco SIP IP phone to
Gateway 1
180 Ringing—Cisco SIP IP phone to
5.
Gateway 1
6. Alerting—Gateway 1 to PBX A
CANCEL (Ring Timeout)—Gateway 1 to
7.
Cisco SIP IP phone
8. Disconnect—Gateway 1 to PBX A
Release Complete—Gateway 1 to PBX A Gateway 1 sends a Release Complete message to PBX A, and the call
9.
200 OK—Cisco SIP IP phone to
10.
Gateway 1
Release Complete—Gateway 1 to PBX A Gateway 1 sends a Release Complete message to PBX A, and the call
11.

Client, Server, or Global Error

Figure B-20
4xx, 5xx, or 6xx response.
Cisco SIP IP Phone Administrator Guide, Release 6.x and 7.x
B-50
Description
Call setup is initiated between PBX A and Gateway 1. Setup includes the
standard transactions that take place as A attempts to call B.
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 A is ready to receive is specified.
The port on which the gateway is prepared to receive the RTP data is
•
specified.
Gateway 1 sends a Call Proceeding message to PBX A to acknowledge
the Call Setup request.
The phone sends a SIP 100 Trying response to Gateway 1. The response
indicates that the INVITE request has been received.
The phone sends a SIP 180 Ringing response to Gateway 1. The response
indicates that the user is being alerted.
Gateway 1 sends an Alert message to PBX A.
Because Gateway 1 did not return an appropriate response within the time
allocated in the INVITE request, Gateway 1 sends a SIP CANCEL
request to the gateway 2. A CANCEL request cancels a pending request
with the same Call-ID, To, From, and CSeq header field values.
Gateway 1 sends a Disconnect message to PBX A.
session attempt terminates.
The phone sends a SIP 200 OK response to Gateway 1. The response
confirms that A has received the 486 Busy Here response. The call
session attempt terminates.
session terminates.
illustrates an unsuccessful call in which User A initiates a call to User B and receives a class
Appendix B SIP Call Flows