ATT cell phones Inbound DTMF not recognized by UCX IVR

[andercom]

Hi all, I have a customer with multiple UCX 250's R6 all updated, each with an Allstream SIP trunk. Recently they have received complaints that some callers can't navigate the IVR via touchtone. After some experimentation, we found that the problem only occurs when using ATT cell phones(all other carriers work fine). When a digit is pressed, the system doesn't respond as though anything was pressed. The same cell phone can call a different company (like a bank) and has no problem. These systems and the sip trunks have been in service for at least 2 years each and have only developed an issue in the last week. this doesn't feel like a problem with the Emetrotel UCX, but I would like to know if there are any tweaks I can make to affect what might be an issue outside the customer's relm.

 

[ucxguy]

For SIP trunks, the most common method of handling DTMF digits is RFC2833. When this method is used (I'll make the assumption that this is the method you configured for the Allstream SIP trunks), the DTMF detection is done at the PSTN gateway (i.e., at the far end) and DTMF digits are sent as frames indicating that there is a DTMF digit and which one. So, the DTMF detection is handled by the gateway that is used by the SIP trunk provider as the connection to PSTN, not by the UCX system. DTMF detection would be done by the UCX system only if the DTMF method used by the SIP trunk was set to "inband" - this method is the least reliable and as such is not recommended.

 

[andercom]

Thanks For the info. I did have RFC2833 protocol set for the sip trunk and it was confirmed that the Allstream gateway was as well. For what it's worth, the problem 'magically' went away later that day and hasn't returned. I hate not knowing.