09-25-2008 02:06 AM - edited 03-15-2019 01:32 PM
Dear All,
We have a setup like this:
CUCM6 --> SIP Trunk --> CUBE --> SIP Trunk --> SIP SP
We have a fax machine attached to an MGCP gateway that is trying to send/receive a T38 fax-relay fax across this infrastructure.
The call setup proceeds and connects but the fax is never transmitted/received. A debug of CCSIP messages reports "488 NOT ACCEPTABLE MEDIA".
Here are the configs:-
MGCP Gateway Config (fax machine attached here)
ccm-manager fallback-mgcp
ccm-manager redundant-host x.x.x.x
ccm-manager mgcp
ccm-manager music-on-hold
ccm-manager config server x.x.x.x
ccm-manager config
!
mgcp
mgcp call-agent x.x.x.x 2427 service-type mgcp version 0.1
mgcp dtmf-relay voip codec all mode nse
mgcp rtp unreachable timeout 1000 action notify
mgcp modem passthrough voip mode nse
mgcp package-capability rtp-package
mgcp package-capability sst-package
mgcp package-capability pre-package
no mgcp package-capability res-package
no mgcp package-capability fxr-package
no mgcp timer receive-rtcp
mgcp sdp simple
mgcp fax rate 9600
mgcp rtp payload-type g726r16 static
mgcp bind control source-interface Vlan2
mgcp bind media source-interface Vlan2
mgcp rtp payload-type nse 101
mgcp rtp payload-type nte 100
!
SIP Config on CUBE:
voice service voip
address-hiding
allow-connections sip to sip
redirect ip2ip
fax protocol t38 nse force ls-redundancy 0 hs-redundancy 0 fallback pass-through g711ulaw
sip
bind control source-interface GigabitEthernet0/0
bind media source-interface GigabitEthernet0/0
early-offer forced
midcall-signaling passthru
g729 annexb-all
dial-peer voice 200 voip
description ** outgoing call to CUCM **
destination-pattern 44T
rtp payload-type cisco-fax-relay 101
rtp payload-type nse 99
rtp payload-type nte 100
modem passthrough nse codec g711ulaw
session protocol sipv2
session target ipv4:x.x.x.x
dtmf-relay rtp-nte
codec transparent
fax-relay sg3-to-g3
fax rate 9600
fax protocol t38 nse force ls-redundancy 0 hs-redundancy 0 fallback pass-through g711ulaw
!
dial-peer voice 300 voip
description ** incoming dial peer **
rtp payload-type cisco-fax-relay 101
rtp payload-type nse 99
rtp payload-type nte 100
modem passthrough nse codec g711ulaw
session protocol sipv2
incoming called-number .
dtmf-relay rtp-nte
codec g711ulaw
fax-relay sg3-to-g3
fax rate 9600
fax protocol t38 nse force ls-redundancy 0 hs-redundancy 0 fallback pass-through g711ulaw
!
dial-peer voice 400 voip
description ** outgoing call to SIP SP **
destination-pattern 9T
rtp payload-type cisco-fax-relay 101
rtp payload-type nse 99
rtp payload-type nte 100
modem passthrough nse codec g711ulaw
session protocol sipv2
session target ipv4:x.x.x.x
dtmf-relay rtp-nte
codec transparent
fax-relay sg3-to-g3
fax rate 9600
fax protocol t38 nse force ls-redundancy 0 hs-redundancy 0 fallback pass-through g711ulaw
My SIP SP tells me that I am not sending a RE-INVITE to his messages and this is why its failing.
Can anyone provide some more help?
Thanks,
10-01-2008 05:47 AM
Some MGCP call agents do not properly pass those portions of Session Description Protocol (SDP) messages that advertise T.38 and NSE capabilities. As a result, gateways that are controlled by these call agents are unable to use NSEs to signal T.38 fax relay to other gateways that use NSEs. As of Cisco IOS Release 12.2(13)T, you can configure gateways to use T.38 fax relay and NSEs even though those gateways may be unable to negotiate those attributes by themselves at the time of call setup.The mgcp fax t38 gateway force command provides a way to ensure gateway-controlled T.38 fax relay between an MGCP gateway and another gateway. The other gateway in the negotiation can be an H.323, Session Initiation Protocol (SIP), or MGCP gateway. Both gateways must be configured to use NSEs to signal T.38 fax relay mode switchover. On H.323 and SIP gateways, use the fax protocol t38 nse force command to specify the use of NSEs for T.38 fax relay. On MGCP gateways, use the mgcp fax t38 gateway force command.
10-03-2008 01:49 AM
Thanks I had tried that but no joy.
My SIP SP says that he supports T38 according to RFC4612 and RFC3363. He does not support fax switchover using NSE.
Has anyone had any luck in getting T38 over SIP to work? Thanks.
11-11-2008 07:35 AM
For those who may be interested I finally managed to get t38 fax from MGCP to SIP working.
Firstly, it seems that super g3 does not like operating at super g3 speeds across SIP, therefore I had to ensure that any super g3 fax machine operated at g3 speeds. In mgcp the command is mgcp fax-relay sg3-to-g3 and in sip it is fax-relay sg3-to-g3 under the dial peer or in global config.
Secondly my SIP SP does not support nse for the switchover from a voice call to a t38 fax call. NTE's are supported and a debug of ccsip messages shows that my provider uses a payload value of 101.
So, with this information I was able to add the following commands to my mgcp gateway:-
MGCP Gateway
============
no mgcp fax t38 inhibit
mgcp package-capability fxr-package
mgcp default-package fxr-package
mgcp fax rate 9600
mgcp rtp payload-type nte 101
and these commands to my SIP gateway:-
SIP Gateway
===========
voice service voip
fax protocol t38 ls-redundancy 0 hs-redundancy 0 fallback none
fax-relay sg3-to-g3
Regards,
02-27-2009 08:03 PM
Hi.
I have a fax connected to a VG224. The VG224 is configured as MGCP. Call flow is:
VG224-->H323 Cube-->SIP-->SIP provider.
Would this work or do I have to configure a SIP trunk in UCM first, then have the VG224 send fax to the SIP trunk, then to the CUBE and out the SIP trunk?
Thank you.
02-27-2009 09:20 PM
Hi Vince,
This will be heavily dependent on your SIP provider's fax support. Many providers do not support T38, etc.
You can try this configuration on the VG224 and on the cube (providing that you remove all other configuration):
voice service voip
fax protocol pass-through g711ulaw
hth,
nick
11-13-2011 06:54 AM
Hi Nicolas,
I understand that Cisco Fax passthrough solution support NSE (Cisco proprietary).
What are the options if the remote gateway is non-Cisco and G729 is used for voice calls?
Is there an industry standard for Fax passthrough that uses NTE for interoperability?
Thanks
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