DTMF issues on incoming call over SIP

[iflylow74]

I'm having an unusual problem with a two factor authorization system we have on our campus. Our phone system consists of:

CUCM 10.5---SIP Trunk----CUBE----SIP Provider

                  ---SIP Trunk----CUBE----SIP Provider

(we have two gateways connecting to our provider)

We moved from PRI to SIP about three months ago and initially had issues with DTMF not working when dialing off campus. After some changes to our dtmf-relay config in our dial peers,  that seems to have been working fine for at least a month or more.

The auth system we are using is called Duo and strangely enough I found out a few weeks ago, it had been purchased by Cisco.

The Duo system can be setup so that when logging into our campus system, Duo will call the users desk phone and ask them to press a button to confirm they are trying to log in. The DTMF press works sometimes and fails on others. I've noticed on the calls where the DTMF button press was ignored, the recording being played by Duo has already began and is partially through the first sentence when you answer. The longer you let the phone ring, the farther into the recording Duo will be.

It seems like the Duo system starts the recording even before the call is answered at the desk phone. I'm guessing there is a signalling issue somewhere. I've experimented by having it call my cell and it seems to work every time so I believe it to be an issue with our CUCM system somewhere.

Any help would be greatly appreciated!

[R0g22]

So what is the issue really ? It is with DTMF i suppose but you also mention that the recording plays early. The second part might not be an issue but just how things work if this is SIP. Calls going to Duo should be early media where in the RTP packets start flowing even before the call actually connects.
What is the DTMF mechanism in use currently and how is Duo integrated ? What DTMF mechanism does Duo support ?

[iflylow74]

Hi Nipun, thank you for your response.

I am relatively new to CUCM so I'll do my best to answer your questions.

Yes, we are using SIP.

The issue lies with the DTMF not being recognized by Duo but I've noticed it doesn't happen on every call. When Duo starts playing the recording before the call is answered, the button press is ignored every time.

When the recording correctly starts playing after you answer the call, the button press is accepted every time.

The dial peers on our CUBE gateways are using dtmf-relay rtp-nte.

I'm honestly not sure what DTMF mechanism Duo is using, we are working on finding that out now. So are you saying it is common for the recording (in this case) to start before the call is answered when using SIP?

I am currently working with TAC so I hope to have a resolution soon.

[jonathan.salter]

What codec is the call getting negotiated at? G729 causes issues with DTMF tones.

[R0g22]

Only if the DTMF are pure in-band, CUCM does not support them.

[iflylow74]

After working with TAC, we've determined that the call manager is sending DTMF in-band correctly so we are now looking at our SIP provider and Duo to see what we can find.