Contents

Introduction

Prerequisites

Requirements

Components Used

Conventions

CPA Software Overview

Typical CPA call flow

New x-cisco-cpa application body

CPA parameter set

CPA CLI

Related Information

Introduction

This document discusses Call Progress Analysis (CPA), the new digital signal processor (DSP) algorithm that analyzes the time-division multiplexing (TDM) voice stream to look for special information tones (SITs), fax/modem tones, human speech, and answering machines.

Prerequisites

Requirements

There are no specific requirements for this document.

Components Used

This document is not restricted to specific software and hardware versions.

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.

Conventions

Refer to Cisco Technical Tips Conventions for more information on document conventions.

CPA Software Overview

Call Progress Analysis (CPA) is the new DSP algorithm that analyzes the TDM voice stream to look for SITs, fax/modem tones, human speech, and answering machines. CPA also passes information to Cisco IOS®.

There is a new SIP application type, x-cisco-cpa, for callers to request a CPA operation and for the gateway to relay information to the caller. CPA is supported only on the TDM gateway where one of the call legs is terminated.

CPA is initiated when SIP INVITE is sent with x-cisco-cpa application/content body. While the call is in progress, DSP analyzes the incoming voice stream. DSP identifies the type of voice stream based on statistical voice patterns or specific tone frequencies. The gateway sends SIP UPDATE with x-cisco-cpa, which contains the CPA result. Based on this CPA result, the caller decides the next step, such as to transfer the call or terminate the call. CPA does not interfere with the existing SIP protocol.

Typical CPA call flow

This diagram depicts the typical CPA call flow.

New x-cisco-cpa application body

These are the application bodies for the new x-cisco-cpa:

- Within SIP INVITE—Dialer > Cisco IOS: Tells Cisco IOS to activate the CPA algorithm for this call.

- Within SIP 18x—Cisco IOS > Dialer: Tells the Dialer whether or not CPA is enabled for this call.

- Within SIP UPDATE—Cisco IOS > Dialer: Tells the Dialer the CPA result.

New x-cisco-cpa application body in SIP INVITE

--uniqueBoundary

Content-Type: application/x-cisco-cpa

Content-Disposition: signal;handling=optional

Events=FT,Asm,AsmT,Sit

CPAMinSilencePeriod=<int16>

CPAAnalysisPeriod=<int16>

CPAMaxTimeAnalysis=<int16>

CPAMinValidSpeechTime=<int16>

CPAMaxTermToneAnalysis=<int16>

--uniqueBoundary--

New x-cisco-cpa application body in SIP 18x

--uniqueBoundary

Content-Type: application/x-cisco-cpa

Content-Disposition: signal;handling=optional

event=enabled

--uniqueBoundary--

New x-cisco-cpa application body in SIP UPDATE

Content-Disposition: signal;handling=optional

Content-Type: application/x-cisco-cpa

CSeq: 102 UPDATE

Max-Forwards: 70

event=detected

status=FT

CPA parameter set

This table shows the CPA parameters, their default value, the definition of each parameter, and the method by which each parameter is configured.

CPA CLI

All the CPA related CLI commands need to be configured under the voice service voip mode. In order to enable CPA support in the global gateway configutaion, enter this CLI command:

[default | no] cpa

These are the commands used to configure various CPA parameters through the CLI:

Note: Values in x-cisco-cpa body overwrite CLI values.

cpa timing live-person

cpa timing timeout

cpa timing term-tone

cpa timing silent

cpa timing valid-speech

cpa timing noise-period

cpa threshold active-signal

cpa threshold noise-level min

cpa threshold noise-level max

This is an example for the CPA configuration through the CLI:

#

!

voice service voip

cpa

cpa timing silent 375

cpa timing live-person 2500

cpa timing timeout 3000

cpa timing noise-period 100

cpa timing valid-speech 112

cpa timing term-tone 15000

cpa threshold noise-level max -50dBm0

cpa threshold noise-level min -60dBm0

cpa threshold active-signal 15db

!

In order to debug the CPA configuration, issue these commands in order to capture useful information:

- show call history voice

- show call active voice

Additional debug information can be collected with the following commands and the PCM capture:

- debug voip hpi all

- debug ccsip messages

Related Information

- Voice Enhancement Features for Cisco IOS Release 12.4(24)T Cisco IOS Release 12.4 Command References

- Technical Support & Documentation - Cisco Systems