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Cisco Bug: CSCuq44635 - CUCM sends Maxbitrate=0 causing fax failure

Last Modified

Feb 02, 2017

Products (1)

  • Cisco Unified Communications Manager (CallManager)

Known Affected Releases

9.1(2.12900.1)

Description (partial)

Symptom:
IMS (PSTN)-------ASR------SIP-------CUCM 9.1(2)------SIP--------VG204---------FAX
T.38 fax call fails. 
Description: 
Incoming call from PSTN  to loca fax connected to VG2xx
Voice call is established OK 
Then when the T.38 fax tone is detected, the VG will send a RE-INVITE with T.38 capabilities 
As soon as this dialog is confirmed with 200 OK from CUCM , the VG204 disconnects the call. (immediately after receiving the 200 OK from CUCM)
The reason why the VG disconnects is b/c of this: 
VG sends a RE-INVITE towards CUCM (when it detects the fax tone) containing the maxbitrate=14400 parameter. 
CUCM sends this on to the aggregation. 
In this case, the aggregation responds without this parameter in its 200 OK response.   CUCM in turn sends maxbitrate=0 parameter to the VG. 
The VG does not like this and fails the call.

Conditions:
CUCM 9.1.2.10000
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