I don't hear Ringback from UCCX

[Waldo Roca Martin]

Hi

I need some help please. 

We contract a new SIP Service provider and I have this problem. 

This is the problem: When I call from mobile to UCCX IVR.  It tranfer the call to agent and we don't hear the ringback tone on Mobile. 

This is the flow: MOBILE ---> SBC SERVICE PROVIDER --SIP->OUR SBC ---> UCCX -Transfer to- CUCM. 

We use UCCX only for IVR. 

Some test. 

If we call from mobile to CUCM internal IP Phone the RINGBACK is OK. 

If we call from mobile to CUCM interna IP phone and it transfert directly to other IP phone the RINGBACK is OK

If we call internally from CUCM IP phone to IVR Route Point we can hear the RINKBACK When UCCX transfers the call to agent. Note that I  hear RINGBACK not MOH. The  Network Hold Audio Source are None for CTI ports in control group. 

I would like to know if the ringback signal is sending by UCCX, I haven't had the oportunity to check the traces yet

I think it could be a 180 RINGING issue may be SP expect 183 with SDP because they have not media to send the RINGBACK. But the fact that if we call directly to CUCM and works and if we call to UCCX IVR fails.. confusing to me because in both case the 180 RINGING is sending by CUCM, Right?

Thank you 

Best Regards

[Waldo Roca Martin]

Hi

Finally we solved using MTP on the trunk to SBC. This post explain the issue. 

https://supportforums.cisco.com/discussion/12305351/no-ringback-sip-provider-after-unity-transfer

When an MTP is involved in a call flow, the dynamics of the call flow changes because MTP stays in the media path. So there is never a break in media and no inactive SDP attribute is sent. The flow looks like below:

CUBE------Media------MTP------------Media-------Unity connection

When the new destination is dialled and transfer is committed, the call flow stays the same

CUBE-------------media----MTP--------media---------IP phone

if there is no MTP, the media path is between CUBE and the IP Phone directly hence when media changes, CUCM has to update it by sending RE-INVITE to CUBE ( it is this re-INVITE that has the inactive DSP which your provider is not responding well too). If MTP is involved, CUCM keeps the media leg between MTP and CUBE from beginning to end; when necessary, it just updates another leg of MTP between MTP and CUBE. UPDATE messages does not include any SDP, so there is no way an inactive attribute can be sent.

This is the flow without an MTP

CUBE-------------media-----Unity connection

When the new destination is dialled and transfer is committed, the call flow stays the same

CUBE-------------no media-----Unity connection

CUBE-------------media-----Transferred destination

I wondering if there is any way to fix this without use MTP, may be on the SBC. 

Best Regards 

[Jakub Stroinski]

Can you share your trunk config and your SBC config (obfuscating the sensitive info)? You should not be required to have MTP on the trunk

[Waldo Roca Martin]

Hi

Thank you for your answer. We use Acme Packet and I have not access to it. I am mor interesting to verify what this happend. After we'll worry to fix it. 

So I can not share mutch information. But this is the flow from CUCM (Athached on the file). 

SBC -----------------> CUCM

In one point when UCCX transfer the call to Operator. CUCM sends a delay offer  Re-INVITE (Time=8.836669) but there is not any information about early media after this re-invite, no 180, no 183. is that normal?

Thank you

Best Regards