DTMF issue when calls are blind transferred

[mjm23]

I have a contact center with inbound call flow go through SBC-->SM-->AAEP(MPP)-->CM. DTMF works fine when call is still within AAEP. the fun part happens when the AAEP blind transfers calls to a VDN which has an option to leave a voicemail by pressing 1 when agents aren't available. Whenever callers press 1, the CM don't receive any DTMF entries. Is there something I need to change in the IVR app? Or is there any configs I need to look at the components I have (SBC, SM, AAEP, CM)?

Appreciate your help.

 

[kyle555]

AAEP can listen in-band and for 2833 DTMFs. So, regardless of configurations, there are technically possible scenarios if a caller has home phone service through their cableco and have an old modem and only do in-band DTMF. When that's the case, there are callers who could DTMF to AAEP but never to CM.

If you can call in to AAEP and get DTMF to work and you can call another DID through the SBC to the VDN to recognize DTMF, then you know it's the transfer that's bugging you.

You're using refer handling on the SBC for the AAEP transfer, right? When the REFER gets translated to a new call inward to CM, what's the SDP offered?
What's the SDP offered to the carrier when you get the call setup in the VDN?

 

[mjm23]

After the blind transfer has been made from AAEP to CM, I see repeated reINVITE requests from the carrier. Not sure why. Maybe because the AAEP sent out a BYE response and the session got disconnected? But the line is still alive. Its just the key I pressed arent recognized by the CM. Can this be mitigated?

 

[kyle555]

yes. test a DID direct to the VDN to confirm it's a transfer issue.
Then, in the server interworking profile that's on your SIP Trunk Server facing the carrier, let me know if Refer handling is on.
And, what SBC release are you on? cat /etc/sbce-version for the exact release.

 

[mjm23]

Thanks for the response kyle555. Direct to VDN works with no DTMF issues. Our SBC is running on 8.0.1.0-10-17555. And yes, refer handling is turned on in the internetworking profile of the carrier.

 

[kyle555]

so, does the new invite from the refer transfer from AAEP generate the same SDP/DTMF stuff as a straight call?

I've supported some big EPs on SBCs with that for years and it has its problems with fancier call flows, but the refer handling is fairly solid. certainly as far as DTMF stuff goes. I've got callback assist on CM too so I know the touchtones pass.

 

[mjm23]

Thanks for the inputs kyle555. I managed to make it work. I changed the DTMF Support parameter in the SBCE from none to SIP Only.