[Freeswitch-users] Issues with T.38 on outgoing fax (sofia T38 invite failed)

Kevin Olbrich ko at sv01.de
Sun Dec 3 23:00:49 UTC 2017 

I just had a talk about this with our carrier and the problems seems on
their side.
This will not be fixed anytime soon, so they said it would be best, if we
use T.38 inside and t38-to-g711 when connecting to them.

I tried to set this in the incoming dialplan:


>
> <include>
>   <extension name="public_did">
>     <condition field="destination_number" expression="^\+(\d+)$|\d+$">
>       <action application="set" data="domain_name=$${domain}"/>
>       <action application="t38_gateway" data="peer"/>
>       <action application="bridge" data="sofia/internal/${
> destination_number}@192.168.31.11"/>
>     </condition>
>   </extension>
> </include>
>


IP 192.168.31.11 is an asterisk machine, connecting the T.38 ATAs at
various locations.


> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 2017-12-03 23:43:49.128433 [DEBUG]
> switch_ivr_bridge.c:1614 (sofia/internal/%2B491122334455 at 192.168.31.11)
> State Change CS_CONSUME_MEDIA -> CS_EXCHANGE_MEDIA
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 2017-12-03 23:43:49.128433 [DEBUG]
> switch_core_state_machine.c:584 (sofia/internal/%
> 2B491122334455 at 192.168.31.11) Running State Change CS_EXCHANGE_MEDIA (Cur
> 2 Tot 2)
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 2017-12-03 23:43:49.128433 [DEBUG]
> switch_core_state_machine.c:653 (sofia/internal/%
> 2B491122334455 at 192.168.31.11) State EXCHANGE_MEDIA
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 2017-12-03 23:43:49.128433 [DEBUG]
> mod_sofia.c:631 SOFIA EXCHANGE_MEDIA
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 2017-12-03 23:43:49.148489 [DEBUG]
> sofia.c:7084 Channel sofia/internal/%2B491122334455 at 192.168.31.11
> entering state [received][100]
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 2017-12-03 23:43:49.148489 [DEBUG]
> sofia.c:7094 Remote SDP:
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 v=0
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 o=- 1512309774 1512309778 IN IP4
> 192.168.31.11
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 s=Asterisk
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 c=IN IP4 192.168.31.11
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 t=0 0
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 m=image 4663 udptl t38
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 a=T38FaxVersion:1
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 a=T38MaxBitRate:14400
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 a=T38FaxTranscodingMMR
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 a=T38FaxTranscodingJBIG
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 a=T38FaxRateManagement:transferredTCF
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 a=T38FaxMaxDatagram:784
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 a=T38FaxUdpEC:t38UDPRedundancy
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 2017-12-03 23:43:49.148489 [DEBUG]
> switch_core_media.c:4028 sofia/internal/%2B491122334455 at 192.168.31.11 T38
> REFUSE on request
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 2017-12-03 23:43:49.148489 [DEBUG]
> sofia.c:8007 Reinvite resulted in codec negotiation failure.
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 2017-12-03 23:43:49.168441 [DEBUG]
> sofia.c:7077 Channel sofia/internal/%2B491122334455 at 192.168.31.11
> skipping state [ready][488]
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 2017-12-03 23:43:49.168441 [DEBUG]
> sofia.c:7084 Channel sofia/internal/%2B491122334455 at 192.168.31.11
> entering state [received][100]
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 2017-12-03 23:43:49.168441 [DEBUG]
> sofia.c:7094 Remote SDP:
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 v=0
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 o=- 1512309774 1512309779 IN IP4
> 192.168.31.11
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 s=Asterisk
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 c=IN IP4 192.168.31.11
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 t=0 0
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 m=image 4663 udptl t38
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 a=T38FaxVersion:1
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 a=T38MaxBitRate:14400
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 a=T38FaxTranscodingMMR
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 a=T38FaxTranscodingJBIG
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 a=T38FaxRateManagement:transferredTCF
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 a=T38FaxMaxDatagram:784
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 a=T38FaxUdpEC:t38UDPRedundancy
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 2017-12-03 23:43:49.168441 [DEBUG]
> switch_core_media.c:4028 sofia/internal/%2B491122334455 at 192.168.31.11 T38
> REFUSE on request
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 2017-12-03 23:43:49.168441 [DEBUG]
> sofia.c:8007 Reinvite resulted in codec negotiation failure.
> ac858869-5320-48fb-b100-1a4a9c3d0851 2017-12-03 23:43:49.188433 [DEBUG]
> switch_rtp.c:7271 Correct audio ip/port confirmed.
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 2017-12-03 23:43:49.188433 [DEBUG]
> sofia.c:7077 Channel sofia/internal/%2B491122334455 at 192.168.31.11
> skipping state [ready][488]
> ac858869-5320-48fb-b100-1a4a9c3d0851 2017-12-03 23:43:49.208437 [DEBUG]
> sofia.c:7084 Channel sofia/external/anonymous at 87.234.1.183 entering state
> [ready][200]
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 2017-12-03 23:43:49.208437 [DEBUG]
> switch_rtp.c:7271 Correct audio ip/port confirmed.
> 7fb3d04b-31f4-4539-a13e-aeaea7a194e8 2017-12-03 23:44:33.188445 [NOTICE]
> sofia.c:1012 Hangup sofia/internal/%2B491122334455 at 192.168.31.11
> [CS_EXCHANGE_MEDIA] [NORMAL_CLEARING]
>


What I need is:

FAX ATA (T.38) -> Asterisk (T.38) -> FreeSWITCH (T.38 to audio GW, refuse
T.38 on A-leg) -> Carrier (audio)

Carrier (audio) -> FreeSWITCH (audio to T.38, refuse T.38 on B-leg) ->
Asterisk (T.38) -> FAX ATA (T.38)

Asterisk is sending Re-INVITES as seen in the log above. Seems like I miss
some settings in my dialplan?

Kevin

2017-12-02 16:36 GMT+01:00 Kevin Olbrich <ko at sv01.de>:

> I need to note that all components are SIP based, no other tech involved.
>
> Kevin
>
> 2017-12-02 13:41 GMT+01:00 Kevin Olbrich <ko at sv01.de>:
>
>> Hi,
>>
>> thanks for the link but I was unable to find information on how to
>> configure my installation of FreeSwitch 1.6 to make things work.
>>
>> I think I need to explain a little bit more on what I am planning to do:
>> FreeSwitch will be used as a SBC to the carrier. It's firewall is limited
>> to the carriers network on the first interface.
>> The second interface is a local subnet where an Asterisk 13 server (PBX)
>> is located, connecting the phones and ATAs (last with T.38 support).
>> For asterisk it is only necessary so set (FAXOPT(gateway)=yes) to have it
>> detect CNG on audio and query both legs for T.38 (or receive a request in
>> advance).
>> It then decides if it goes to passthru mode or transcode.
>>
>> As far as I understand the FreeSwitch docs, there are these options
>> (located in dialplan default before bridge):
>>
>>> <action application="set" data="fax_enable_t38=true"/> <!-- Enable t.38
>>> for this call -->
>>> <action application="set" data="fax_enable_t38_request=true"/> <!--
>>> Enable t38_gateway to send a t.38 reinvite when a fax tone is detected. If
>>> using t38_gateway peer then you need to export this variable instead of set
>>> -->
>>> <action application="set" data="execute_on_answer=t38_gateway self"/>
>>> <!--Execute t38_gateway on answer. self or peer. self: send a reinvite back
>>> to the a-leg. peer reinvite forward to the b-leg -->
>>
>>
>> <action application="export" data="fax_enable_t38=true"/> <!-- Required
>>> as of v1.6 -->
>>> <action application="export" data="t38_passthru=true"/>
>>
>>
>> *What I would like to accomplish is getting as much as T.38 I can get.*
>> The ATA should always be able to negotiate T.38 with Asterisk (which seems
>> to work atm), FreeSwitch should then negotiate T.38 if Asterisk or the
>> carrier asks for it (no CNG detection).
>> I am not sure if I can just enable t38_gateway and passthru, this case is
>> not listed on confluence or the old wiki. Even if I do, it does not work.
>>
>> FreeSwitch might need to transcode T.38 to audio for our backup carrier
>> who does not support T.38.
>>
>> Kind regards,
>> Kevin
>>
>> 2017-12-02 9:20 GMT+01:00 Raúl Alexis Betancor Santana <
>> rbetancor at gmail.com>:
>>
>>> Some carriers gateways doesn't like a T.38 invite on advance, usually
>>> the order that gives better results for faxing are first invite on
>>> PCMU/PCMA (or any other supported codec) and then re-invite to T.38.
>>>
>>> Take a look at how gonicus gofaxip do-it (https://github.com/gonicus/go
>>> faxip)
>>>
>>> On Fri, Dec 1, 2017 at 10:21 PM, Kevin Olbrich <ko at sv01.de> wrote:
>>>
>>>> Hi!
>>>>
>>>> Our carrier supports T.38 for outgoing faxes. I am trying to send faxes
>>>> like this:
>>>>
>>>> originate {origination_caller_id_name='kevin',origination_caller_id_nu
>>>>> mber='+49123456789',ignore_early_media=true,absolute_codec_s
>>>>> tring='PCMA,PCMU',fax_use_ecm=true,fax_enable_t38=true,fax_e
>>>>> nable_t38_request=true}sofia/gateway/carrier_1/+4912121212
>>>>> &txfax(/opt/faxout.tif)
>>>>
>>>>
>>>>
>>>> Log:
>>>>
>>>> 668fd128-f2f5-4af5-9536-6780762c2efa 2017-12-01 21:38:57.513164
>>>>> [DEBUG] sofia_glue.c:1295 sofia/external/+4912121212 sending invite
>>>>> version: 1.6.19 -36-7a77e0b 64bit
>>>>> 668fd128-f2f5-4af5-9536-6780762c2efa Local SDP:
>>>>> 668fd128-f2f5-4af5-9536-6780762c2efa v=0
>>>>> 668fd128-f2f5-4af5-9536-6780762c2efa o=FreeSWITCH 1512130268
>>>>> 1512130270 IN IP4 123.123.123.123
>>>>> 668fd128-f2f5-4af5-9536-6780762c2efa s=FreeSWITCH
>>>>> 668fd128-f2f5-4af5-9536-6780762c2efa c=IN IP4 123.123.123.123
>>>>> 668fd128-f2f5-4af5-9536-6780762c2efa t=0 0
>>>>> 668fd128-f2f5-4af5-9536-6780762c2efa m=image 30466 udptl t38
>>>>> 668fd128-f2f5-4af5-9536-6780762c2efa a=T38FaxVersion:0
>>>>> 668fd128-f2f5-4af5-9536-6780762c2efa a=T38MaxBitRate:14400
>>>>> 668fd128-f2f5-4af5-9536-6780762c2efa a=T38FaxFillBitRemoval
>>>>> 668fd128-f2f5-4af5-9536-6780762c2efa a=T38FaxRateManagement:transfe
>>>>> rredTCF
>>>>> 668fd128-f2f5-4af5-9536-6780762c2efa a=T38FaxMaxBuffer:2000
>>>>> 668fd128-f2f5-4af5-9536-6780762c2efa a=T38FaxMaxDatagram:400
>>>>> 668fd128-f2f5-4af5-9536-6780762c2efa a=T38FaxUdpEC:t38UDPRedundancy
>>>>> 668fd128-f2f5-4af5-9536-6780762c2efa
>>>>> 668fd128-f2f5-4af5-9536-6780762c2efa 2017-12-01 21:38:57.533158
>>>>> [DEBUG] sofia.c:7084 Channel sofia/external/+4912121212 entering state
>>>>> [calling][0]
>>>>> 668fd128-f2f5-4af5-9536-6780762c2efa 2017-12-01 21:38:57.673120
>>>>> [DEBUG] sofia.c:6294 sofia/external/+4912121212 T38 invite failed
>>>>> 668fd128-f2f5-4af5-9536-6780762c2efa 2017-12-01 21:38:57.673120
>>>>> [DEBUG] sofia.c:7077 Channel sofia/external/+4912121212 skipping state
>>>>> [ready][488]
>>>>
>>>>
>>>>
>>>> Carrier confirmed that T.38 is possible... What could be the cause for
>>>> this? How can I enforce T.38 instead of falling back to g711a (hangup on
>>>> failed invite)?
>>>>
>>>> Thanks.
>>>>
>>>> Kind regards,
>>>> Kevin
>>>>
>>>> ____________________________________________________________
>>>> _____________
>>>> Professional FreeSWITCH Consulting Services:
>>>> consulting at freeswitch.org
>>>> http://www.freeswitchsolutions.com
>>>>
>>>> Official FreeSWITCH Sites
>>>> http://www.freeswitch.org
>>>> http://confluence.freeswitch.org
>>>> http://www.cluecon.com
>>>>
>>>> FreeSWITCH-users mailing list
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>>>> http://lists.freeswitch.org/mailman/listinfo/freeswitch-users
>>>> UNSUBSCRIBE:http://lists.freeswitch.org/mailman/options/free
>>>> switch-users
>>>> http://www.freeswitch.org
>>>>
>>>
>>>
>>> ____________________________________________________________
>>> _____________
>>> Professional FreeSWITCH Consulting Services:
>>> consulting at freeswitch.org
>>> http://www.freeswitchsolutions.com
>>>
>>> Official FreeSWITCH Sites
>>> http://www.freeswitch.org
>>> http://confluence.freeswitch.org
>>> http://www.cluecon.com
>>>
>>> FreeSWITCH-users mailing list
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>>
>>
>
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