This document describes the behavior of the Session Initiation Protocol (SIP) dialer in the Cisco Unified Contact Center Enterprise (UCCE) environment when the gateway sends a Call Progress Analysis (CPA) UPDATE message before the 200 Ok OFF HOOK event.
Cisco recommends that you have knowledge of these topics:
- Cisco UCCE
- Cisco UCCE Release 8.x SIP or Skinny Client Control Protocol (SCCP) dialer
The information in this document is based on the Cisco UCCE outbound dialer.
The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.
The SIP dialer cancels calls and a Code 2 error (DIAL_ERROR) message appears when the gateway sends the update message for the CPA analysis before the 200 Ok for the off-hook message.
This image illustrates the process flow:
The dialer cancels the call because it does not see the 200 Ok message for the original invite that comes from the gateway.
This behavior is expected if the call is an actual voice, an answering machine, a fax machine, or a similar type of call. In this situation, Telco must send the ISDN Q.931 CONNECT message so that the gateway can generate the 200 Ok message and forward it to the dialer.
However, in some cases, Telco cannot complete the call and conveys the reason to the gateway with Special Information Tones (SITs). This response is followed by a recorded announcement that describes the problem.
When these tones are sent instead of the ISDN Q.931 CONNECT message, the gateway CPA processing module detects it and sends an SIP UPDATE message to the dialer instead of the 200 Ok message, which causes the dialer to cancel the calls with the false Code 2 error. In addition, the gateway establishes the media path and passes the announcement message to the dialer.
In order to correct the dialer behavior in regards to SIT calls, you must install ES_4 on the Version 9.0(4) code. Refer to Cisco bug ID CSCuj55253 for more information.