I have a RightFax connected to a CUCM v6 through a SIP trunk. VGs are configured for T38 with fallback cisco protocol. Some faxes are connected directed on FXS on VG, and controlled by CUCM via STCAPP service protocol.
OK: from RightFax --> Fax Rx/Tx to/from PSTN work OK.
PROBLEM: from RightFax --> Fax Rx/Tx to/from STCAPP fax cannot negotiate T38 (see attached wireshark trace: not acceptable media)
Here is the config:
stcapp register capability 0/3/0 both
stcapp ccm-group 1
voice class codec 1
codec preference 1 g711alaw
codec preference 2 g711ulaw
timeouts ringing infinity
dial-peer voice 415800 pots
dial-peer voice 415801 voip
description TEST T38
voice-class codec 1
incoming called-number 415800
fax protocol t38 ls-redundancy 0 hs-redundancy 0 fallback cisco
I managed to send fax by forcing the CUCM to reroute to the VG via H323, by inserting a new route pattern (9.415800 predot) and a creating an additional dial-peer on the VG:
dial-peer voice 415802 pots
--> SUCCESS !! T38 is negotiated correctly
--> Does anyone having an idea of what can cause this problem ?
--> Does anyone having succeeded in making T38 call to STCAPP controlled fax in a similar set-up ?
SCCP does not support protocol based T38. You would need to use SIP/H323/MGCP for this functionality to work.
As well, there are almost no additional features gained by a fax machine for a SCCP controlled port rather than MGCP. Or SIP/H323 if you don't mind configuring things on the gateway.