Fax T38 over SIP trunks

streamfx · Post by **streamfx** » 18 Jan 2010 21:38

Are there any specific config parameters for making a OT Fax server work over a OXE with SIP trunks? i160512. I made sure IP->Fax Param->T38 only is enabled.

The faxes just fail to send/receive.

cavagnaro · Post by **cavagnaro** » 19 Jan 2010 12:00

Be sure to be using G711 as codec for the SIP Trunk

streamfx · Post by **streamfx** » 19 Jan 2010 16:01

For both my External SIP TG to the carrier and the OTUC Fax Gateway are set to: IP Compression Type + G 711
The carrier told me they dont directly support T38 but support "T38 passthrough" whatever that may mean.

freedom · Post by **freedom** » 19 Jan 2010 16:10

Check your ip-domain settings. perhaps the ip-domains used are still on internal-external domain compression 'default'.
Default means USE compression.

Also try to make a trace of a fax call:
motortrace 2
traced

Have a look at the compression type(s) offered in the call.

You could also check the external sip gateway setting 'trunk group compression type only' (something like this, don't know the exact nae by heart...) to forcethat only G711 is offered for the call.