I'm having some trouble with a T.38 fax call being torn down cleanly. Call setup is normal, the transition from G.711 to T.38 is normal and the fax transmission is successful. When the gateway attempts to renegotiate to G.711 CUCM rejects the invite with a 415 Unsupported Media Type.
fax-device -> VG400 -> CUCM -> CUBE -> PRI
SIP signaling:
VG400 Invite to CUCM, CUCM Invite to CUBE, PRI call setup completes, SIP call setup completes as G.711
6 seconds later CUBE Invite to CUCM attempting T38 version 0. CUCM Invite to VG400, VG400 responds 200 OK.
Fax transmits for 1 min 25 seconds
CUBE Invite to CUCM attempting G.711. CUCM responds 415 Unsupported Media Type
CUCM tears down the call. CUCM BYE to CUBE with Reason: Q.850;cause=47, CUCM BYE to VG400 with Reason: Q.850;cause=47
Configuring the CUBE to send a SIP Bye message when terminating the T30 leg, without deescalating the call back to G.711, would be ideal.
