CUBE, CUCM & DTMF

[Gordon Ross]

I have a standard setup:

CUCM <=> CUBE <=> ITSP

In my CUBE's config, I have:

voice service voip
 address-hiding
 dtmf-interworking rtp-nte
 mode border-element
 allow-connections sip to sip

...

voice class codec 1
 codec preference 1 g711alaw

...

And all my dial-peers have:

dial-peer voice XXXX voip

  voice-class codec 1

  dtmf-relay rtp-nte

...

I would assume that this means CUBE will force DTMF to be RFC 2833 (along with G7.11 a-law audio codec).

But if CUCM has no MTP configured on the trunk, DTMF does not work. With a call from CUCM to the ITSP,  in the CUBE debugs I see:

007441: Jan 10 17:30:05.662: //177692/E42212000000/SIP/Info/info/2080/sipSPI_ipip_store_channel_info: negotiated dtmf not available, using dialpeer config dtmf = 6

And DTMF spectacularly fails to work. But G.711 a-Law works a treat.

If I set the Early Offer support on the SIP Profile for the trunk in CUCM to be "Best Effort (no MTP)" then DTMF works wonderfully.

006741: Jan 10 17:19:42.009: //177607/70333A000000/SIP/Info/info/32/sipSPIDoDTMFRelayNegotiation: RTP-NTE DTMF relay option

Simple question: Why?

If I've specified RFC 2833 DTMF everywhere in CUBE, surely it should negotiate it with all endpoints, regardless of whether they are using early or late offer media?

Thanks,

Gordon.

[Rajan]

Hi Gordon,

In the first scenario where dtmf is not working what is the DTMF setting on the sip trunk?

I guess the CUCM is unable to do dtmf negotiation in this case whereas in the Second scenario works fine mainly due to the early offer and not because of the MTP.

//Unified CM does not need to insert an MTP to create an outbound Early Offer call over a SIP trunk if the inbound call to Unified CM is received by any of the following means:

On a SIP trunk using Early Offer
On an H.323 trunk using Fast Start
On an MGCP trunk
From a SIP-based IP phone registered to Unified CM
From newer SCCP-based Cisco Unified IP Phone models registered to Unified CM//

With the "Early Offer support (insert MTP if needed)" selected, the CUCM wont insert MTPs as the capable phones themselves provide their capabilities to send in the early offer SDP. With this and the other side CUBE providing rtp-nte as per the configuration, dtmf negotiation seems to be successful.

HTH
Rajan

[Chris Deren]

Does the DTMF fail to work on inbound or outbound calls? if inbound what system is it hitting that requires DTMF input? Unity, CCX, CVP, etc?