Call Progress Analysis Over IP-to-IP Media Session
The Call Progress Analysis Over IP-IP Media Session feature enables the detection of automated answering systems and live human voices on outbound calls and communicates the detected information to the external application. Typically, call progress analysis (CPA) is extensively used in contact center deployments in conjunction with the outbound Session Initiation Protocol (SIP) dialer, where CPA is enabled on the Cisco Unified Border Element (CUBE), and digital signal processors (DSP) perform the CPA functionality.
Call Progress Analysis
Call progress analysis (CPA) is a DSP algorithm that analyzes the Real-Time Transport Protocol (RTP) voice stream to look for special information tones (SIT), fax or modem tones, human speech, and answering machine tones. CPA also passes the voice information to Cisco IOS or CUBE.
CPA is initiated on receiving a new SIP INVITE with x-cisco-cpa content. While a call is in progress, the DSP or the Xcoder analyzes the incoming voice or media stream. The DSP identifies the type of voice stream based on statistical voice patterns or specific tone frequencies and provides the information to the CUBE. The CUBEnotifies the dialer with a SIP UPDATE with x-cisco-cpa content along with the detected event. Based on the report, the caller (dialer) can decide to either transfer the call or terminate the call.
To use the CPA functionality, you must enable CPA and configure CPA timing and threshold parameters.
SIP Message |
Direction of Message |
Meaning |
---|---|---|
18x or 200 |
Cisco IOS to dialer |
CUBE informs the dialer if CPA is enabled for a call or not. |
New INVITE |
Dialer to Cisco IOS |
Dialer requests Cisco IOS or the CUBE to activate the CPA algorithm for this session. |
UPDATE |
Cisco IOS to dialer |
Cisco IOS or the CUBE notifies the dialer about the detected event. |
CPA Events
CPA Event |
Definition |
---|---|
Asm |
Answer machine |
AsmT |
Answer machine terminate tone |
CpaS |
Start of the Call Progress Analysis |
FT |
Fax/Modem tone |
LS |
Live human speech |
LV |
Low volume or dead air call |
SitIC |
Special information tone IC -- Intercept -- Vacant number or Automatic Identification System (AIS) |
SitNC |
SIT tone NC—No Circuit (NC), Emergency, or Trunk Blockage |
SitVC |
SIT tone VC—Vacant Code |
SitRO |
SIT tone RO—Reorder Announcement |
SitMT |
Miscellaneous SIT Tone |