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Cisco Bug: CSCvt49769 - CUCM - Call not clearing on the line(SCCP) because of race condition in MGCP to SCCP call flow

Last Modified

Sep 18, 2020

Products (1)

  • Cisco Unified Communications Manager (CallManager)

Known Affected Releases

10.5(2.10000.5) 11.5(1.10000.6) 12.0(1.10000.10) 12.5(1.10000.22)

Description (partial)

Symptom:
Call between SCCP and MGCP. Before (blind) transfer is completed from SCCP device, MGCP side disconnects the call. Before this disconnect is processed, SCCP side hits transfer button for 2nd time to complete transfer. To complete the transfer pause req is sent to MGCP side process and to process disconnect timer is started in MGCP side. This timer expires while MGCP is in pause state hence no action is taken. We see a deadlock happening here after the timer expires -  because to blind transfer we are waiting for the join to happen( which doesn’t happen as call is disconnected by MGCP side) and due to disconnect we are waiting for the timer to expire so that the saved signals can be processed(but the process is moved to paused state because of transfer)

Subsequent calls to the line would fail if busy trigger is set to 1 even though there is no active call on that line.

Conditions:
1.	Call between MGCP and SCCP
2.	MGCP side disconnects the call while SCCP side is blind transferring the call.
3.	While disconnect from MGCP is processed, SCCP hits transfer again to complete transfer.
4.	Busy trigger on SCCP is set to 1.
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