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Cisco Bug: CSCup50971 - No Audio after blind conf or xfer via SIP trunk with Early Media PRACK

Last Modified

Mar 04, 2018

Products (1)

  • Cisco Unified Communications Manager (CallManager)

Known Affected Releases


Description (partial)

Ad-Hoc Conference with a PSTN participant fails to cut audio through and leads to media inactivity detection and call clearing.

The same no audio cut through is also observed with the blind transfer case when a SCCP Phone or a 79XX SIP Phone is used to initiate the Blind Transfer.

When a SCCP Phone or a 79XX SIP Phone initiates an Adhoc 3 way Conference where the end user invites a PSTN destination via SIP Trunks connected to CUBE and then to a SIP Service Provider.

SIP Service Provider does not support UPDATE method so between UCM and CUBE leg we can not utilize the UPDATE method to update the media upon invoking the Conference Bridge.

The invited PSTN destination call requires early Media with 183 session progress and the Conference Initiator attempts a blind conference where he/she invokes the conference while the PSTN destination is still ringing.

The conference bridge is invoked however audio between the conference bridge and the CUBE is never cut through.

The same failure is observed when a Blind Transfer is initiated to an Off-net PSTN Destination via a SIP Trunk with the similar conditions as the previous adhoc conference, the same results are observed where upon completing the blind transfer even after the PSTN destination answers the call audio is not cut through.
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