Faxing via iPECS SLT over SIP trunks problem

[takeapart88]

We are Faxing via an iPECS SLT over SIP trunks. Its very unreliable; sometimes we receive faxes sometimes not. Outbound faxing usually fails. This did not happen when using ISDN. Is there any settings in iPECS that can help with this or is it just that SIP does not like FSK? Thanks.

 

[Odycon]

To use Faxing over SIP trunks ensure that the codec is locked to G711. Anything less & the compression will kill the fax.
This can be found under SIP Data / SIP CO Attributes / External CODEC Priority Configuration. Only set the 1st priority.
Also set the Board Based Attribute for the Sequence of the SIP G/W, turn off RTP security & turn on T38 enable.

See how that goes

 

[montyzummer]

t38 is the critical part to this, you need to remember sip is a protocol and not a standard like isdn , so first question you need to ask does your sip provider support T38 if not you are never going to get this to be stable, if they dont fax to email is a well known feature on most sip providers , for outgoing the analogue line side of the BB circuit will need to be utilised.

APSS (SME)
ACSS (SME)