We are facing a problem with CUCM 8.0(3) and 8.6(2a) when a remote destination calls in from an H.323 gateway to a busy IP phone. The mobile phone with the remote destination number just gets a ringback tone (Q.931 Alerting) as if the IP phone would not be busy. If the same mobile phone is not configured as a remote destination and calls in to the busy IP phone, it will get a busy tone (Q931 Disconnect with reason "user busy").
I have a found the following similar bug in the bug tool:
CSCts24630 - CUCM does not forward busy tone when RD in PSTN returns busy across MGCP DescriptionSymptom:
CAllManager does not provide busy tone to caller when remote destination in PSTN is busy. Remote destination sends disconnect message to CUCM with cause code 'user busy', however, CUCM does not forward this signal to caller and caller continues hearing ringback.
When MGCP gateway is involved, and remote destination in PSTN is busy.
8.6(2.99000.92), 8.6(2.98000.56), 8.6(2.98000.24)
8.6(2.11001.1), 8.6(1.21013.1), 8.5(1.13900.4)
Has anyone faced CSCts24630 and upgraded to a fixed version? If so could you please check if you get a busy tone when calling from a remote destination?
By the way, does anyone if CSCts24630 should be fixed in 126.96.36.19900-2?
Any feedback is appreciated and many thanks in advance
I have opened a TAC service request for the problem and we have found a solution for the problem.
The problem is caused by CUCM because it tries to provide the busy tone with the Annunciator which results in an ISDN Alerting message with Inband Info instead of a Disconnect message with cause "user busy".
If you configure a Media Resource Group List/Media Resource Group that does not contain an Annunciator and assign it to the Gateway config in CUCM, the Disconnect message with "user busy" will be sent out immediately and you should hear the busy tone on your mobile.
Extract of the mail from TAC:
"I have checked the logs, and I could see the call coming in from the PSTN and the calling number is recognized as a Remote Destination.
Once the CallManager finds the destination device is busy it will tell the CellProxy about that and then try to invoke annunciator to play the busy tone :
11:35:06.496 |CellProxy( 298): ccDisconnReq.cv = 17 set MobilityEvent = MOBILITY_EVENT_PLAY_ANNOUNCEMENT - active_CcDisconnReq |1,100,13,13587.4^10.1.10.8^*
The Annunciator is allocated to play busy tone for Remote Destination parties and when CUCM detects that the calling party is part of Remote Destination Profile, it does consider as an "internal" calling party and play the busy tone through the Annunciator. If you try to call the same busy phone from the internal IP Phone extension, the Annunciator will here play the busy tone directly to the IP Phone.
This is why we see different behavior as compared to other calls from PSTN.
Can you please configure the MRGL associated with the H.323 Gateway so that it does not contain any Annunciator resource and see if it fixes the issue?
By doing this, we will play directly Busy Tone through the H.323 gateway and the Disconnect (User Busy) message."