RightFax T38 with stcapp controlled FAX

Answered Question
Jul 6th, 2009
User Badges:

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

stcapp


voice class codec 1

codec preference 1 g711alaw

codec preference 2 g711ulaw


voice-port 0/3/0

cptone CH

timeouts ringing infinity

caller-id enable


dial-peer voice 415800 pots

service stcapp

port 0/2/0


dial-peer voice 415801 voip

description TEST T38

preference 1

voice-class codec 1

incoming called-number 415800

fax protocol t38 ls-redundancy 0 hs-redundancy 0 fallback cisco

no vad


WORKAROUND:

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

preference 1

destination-pattern 415800

port 0/2/0


--> 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 ?



Correct Answer by Nicholas Matthews about 7 years 8 months ago

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.


-nick

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 4 (1 ratings)
Loading.
Correct Answer
Nicholas Matthews Wed, 07/08/2009 - 06:53
User Badges:
  • Red, 2250 points or more

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.


-nick

DANIEL COHEN-LAROQUE Wed, 07/08/2009 - 22:47
User Badges:

Hi Nick,


thanks for your reply. Now I understand the protocol mismatch error...


For FXS/SCCP on voice gateways, I see following advantages: 1. customer can control line parameter directly from CUCM (like MGCP), and 2. SRST support (not possible with MGCP, right?)


I guess it makes sense to keep SCCP, and had transtation/partition to redirect inbound T38 calls from the rightfax SIP trunk to VGs via H323 (already configured for PSTN).


Actions

This Discussion