I have CUCM 7.0.2, this is call flow:
SIP)(with callback feature)--CCM7--GW2811(MGCP)--PRI(QSIG)--HICOM(HIPATH 400)--ANALOG PHONE
and the problem is that:
When I make a call to a phone that is in a busy third SIP phone does not understand the state of the phone, but will hear the busy tone in the logs but I can see that he does not understand the state of the phone. Receiving a SDP message "SIP 183 Session Progress" and not a "SIP 486 Busy Here".
How can I configure CUCM to translate the message "SIP 183 Session Progress" to "SIP 486 Busy Here"?
Is it a bug or a limitation of the third-party SIP devices?
I can see in the debug of the GW that first remote PBX sends a CALL PROC ( with busy tone) and after 30 sec. sends the signal busy that understands the SIP third-party as "SIP 486 Session Progress".