SIP to ITSP and DTMF issue

[Sinisa Hreljac]

Hi,

after switching to SIP with our ITSP we have issues with some calls where no DTMF can be used.

Some clients are reporting that they cannot go through menus on our IVR (incoming calls from PSTN), and also we have same problem with some outgoing calls to someone others IVR. The fact is that we have problem with only few PSTN numbers so it looks like there is something between our ITSP and their ITSP provider.

Configuration is: CUCM <-> CUBE <-> ITSP

I have done outgoing call to two remote (someone elses) IVR, one call in which DTMF is working and other where is not working.

Invite from our CUBE to ITSP is for both call in same format .

However, in non working scenario, we have 200 OK w/SDP response from ITSP but with no telephony-event in SDP:

v=0
o=BroadWorks 1053387527 1 IN IP4 x.x.x.x
s=-
c=IN IP4 x.x.x.x
t=0 0
m=audio 26168 RTP/AVP 8
a=rtpmap:8 PCMA/8000
a=sendrecv
a=bsoft: 1 image udptl t38

In working scenario, we have 180 Ringing w/SDP response 

v=0
o=- 1601965225 2 IN IP4 x.x.x.x
s=SBC call
c=IN IP4 x.x.x.x
b=AS:64
t=0 0
m=audio 25918 RTP/AVP 8 101
a=sendrecv
a=rtpmap:101 telephone-event/8000
a=ptime:20

In dial-peer configuration for outgoint calls to PSTN we have:

 dtmf-relay rtp-nte sip-kpml

and in incoming dial-peer from PSTN to CUBE:

dtmf-relay rtp-nte sip-kpml

no dtmf-interworking

Is this something that we can fix with CUBE configuration changes or it is ITSP problem?

Thanks!

[Mohammed al Baqari]

Keep DTMF interworking on. Also, make sure that you are matching the right
dial peer and use RTP-NTE force keyword to ensure its applied. Let us know
how it goes

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[TONY SMITH]

Looks similar to an issue we had with Etisalat, some calls they use RTP-NTE and some calls it's inband.  I don't think we ever found a good solution, in theory locally registered DSPs should deal with it.  

[Sinisa Hreljac]

Unfortunately, we dont have locally DSPs on CUBEs

[TONY SMITH]

Looking at the documents, maybe the DSPs don't need to be local.  What it actually says is "Transcoding resources must be available and registered with the CUBE accordingly."

https://www.cisco.com/c/en/us/support/docs/unified-communications/unified-border-element/200412-DTMF-Relay-and-Interworking-on-CUBE.html#anc36

As I say I never found a good answer when DTMF method varies from one call to the next.  And it doesn't help that in some contexts you can't explicitly configure inband, it's only implied when no other method is specified.  So you can set inband except as the only method.

I'm hoping the answer will pop up here and I can use it myself.

[Sinisa Hreljac]

Hi,

in outgoing calls that I provide SDPs there are two dialpeers involved:

#10 - from CUCM to CUBE:

dtmf-relay rtp-nte sip-kpml

and #80 - from CUBE to PSTN:

dtmf-relay rtp-nte sip-kpml

There is no DTMF interworking disabled. What do you mean with "force keyword"? Where should I put it?

[Mohammed al Baqari]

Hi,

On the dial-peer connecting to your ITSP use this command 'voice-class sip
dtmf-relay force rtp-nte'. This is a hidden command so just paste it as it
is.

This will force your ITSP to use RTP-NTE.

Also, during an active call, run the command 'show call active voice brief'
and try to identify your call using called and calling numbers. Then make
sure that the PID is the dial-peer which you are expecting to match. This
is important to make sure that dial-peer is matched with the command
properly.

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[Sinisa Hreljac]

Thanks to pointing me to that hidden command.

However, in meantime our ITSP just make some changes in their side so now DTMF for problematic outgoing calls are working OK.

Now we have to find how to resolve DTMF issue for incoming call from clients as this is something that we can't reproduce

Incoming and outgoing calls are matching correct dial-peers...that is checked allready.

So, for incoming dial-peer from PSTN I have "no dtmf-interworking", so I will delete that line to see if it will help.

[Mohammed al Baqari]

Yes please. Also, use the same hidden command to use RTP-NTE.

[Sinisa Hreljac]

Hi,

wasn't helpfull for theese clients, but ITSP did something on their side and now it is wotking. Thanks anyway.