NetBorder Call Analyzer Answering Machine Detection - Cisco Voice Gateway

Here are some suggestions on how to setup a Cisco voice gateway to handle call requests from the NCA. This is not an exhaustive guide, thus we recommend this to be done by someone familiar with Cisco.

You can always refer to the Cisco documentation for more details.

You basically need to setup a VoIP dial peer on the Cisco router to allow it to communicate with the NCA. One or more Plain Old Telephony (POT) dial peers also have to be added for the interface(s) with the PSTN. We are not going to get into details on the settings of these POTs dial peers because it all depends on your configuration, numbering plan and telco provider.

Here are the commands to create the VoIP dial peer:

• dial-peer voice [number] voip

• destination-pattern (1)

• session target ipv4 [NCA ip address and port]

• codec (2)

• rtp payload-type cisco-codec-fax-ind 99 (3)

• rtp payload-type nte 96 (3)

• voice-class codec [unique class tag]

• session protocol sipv2 

• dtmf-relay rtp-nte (4)

• no vad (5)

Notes:

(1) Enter a number or a pattern(regular expression) that has to be matched for the calls using this dial-peer.

(2) codec used i.e. G729

(3) 

• Cisco by default uses some payloads in the dynamic range (96-127) for proprietary codecs (ex 96 is reserved to fax relay by default). A symptom of this is Cisco as an UAS not sending SDP answers with a telephone-events (RFC2833)

• From CISCO Dual Tone Multifrequency Relay for SIP calls Using Named Telephone Events (NTE) - Configuring DTMF Relay and NTE Payload Type

  • rtp payload-type [type] [number] List of types

  • The nte keyword chooses the type of payload in the Named Telephony Event (RFC2833) packet. Number values are 96 through 127; the default value is 101.

  • Note Reserved values ( 96, 97, 100, 121, 122, 123, 125, 126, and 127) cannot be configured for the rtp-nte payload value unless they are freed by reassigning them to any other values that are within the 96 through 127 range.

  • To make a Cisco Gateway work with a product that always start at 96 for RFC2833 (telephony-events) as stated above means that you need to reassign fax relay to something other than 96 and set the nte type to payload 96.

(4)  DTMF tones are encoded in the NTE format and transported in the same RTP channel as the voice.

(5) It's important to disable Voice Activity Detection (VAD), also referred to as silence suppression.