OBi202 Settings Tweak for Faxing with Callcentric?

[telecomm]

We send faxes using OBi202 and Callcentric.  Many of them go through, but sometimes we have trouble.  I am wondering if there are any configuration settings I can play with on the OBi202 that might increase the chances of more successful sending. 
Here is what Callcentric states, but I am not sure where to go in the OBi202 to make changes regarding T.32 and/or passthrough.

T.38
Enable T.38
Disable echo cancellation and echo suppression
If available enable re-INVITE for faxes

Pass through
Try using the G711 codecs as these would offer more bandwidth
Disable echo cancellation and echo suppression
Disable NSE, usually on Cisco/Linksys devices

[SteveInWA]

Faxing over VoIP is not very reliable, no matter which settings you tweak.  Two settings you can change on your fax machine, not on your OBi, (in addition to the settings Callcentric recommended) are to limit the fax speed to 9600bps, and to turn OFF fax error correction.  It seems contradictory, but fax error correction is terribly crude:  when an error is detected, the sending fax machine has to re-transmit a large chunk of the data, and if the error rate is consistently above the threshold, it will keep flailing, trying to resend the page.  So, it is not "correcting" any errors via extra data bits being sent for that purpose; it is simply re-sending the same stuff.

If this is something you need to do for business on a frequent basis, and it can impact your business if it fails, I recommend using a commercial fax gateway service provider.  In that scenario, you typically email the document to the service provider as a JPEG or PDF, and their high-performance fax servers send the fax for you over suitable telephone service.

[telecomm]

Thanks Steve!  Here is what Callcentric came back with:

--- Codec Profile ---

G726R32 Enable: Unchecked
Fax Event Enable: Checked
T38Enable: Uncheck

*Please note that you will need to uncheck either the "ObiTALK Settings" column to edit the subsequent fields.

--- ITSP Service ---

X_DnsSrv: Leave checked but uncheck ObiTALK Settings column
X_DnsSrvAutoPrefix: Leave checked but uncheck ObiTALK Settings column

Faxing over VoIP is not very reliable, no matter which settings you tweak.  Two settings you can change on your fax machine, not on your OBi, (in addition to the settings Callcentric recommended) are to limit the fax speed to 9600bps, and to turn OFF fax error correction.  It seems contradictory, but fax error correction is terribly crude:  when an error is detected, the sending fax machine has to re-transmit a large chunk of the data, and if the error rate is consistently above the threshold, it will keep flailing, trying to resend the page.  So, it is not "correcting" any errors via extra data bits being sent for that purpose; it is simply re-sending the same stuff.

If this is something you need to do for business on a frequent basis, and it can impact your business if it fails, I recommend using a commercial fax gateway service provider.  In that scenario, you typically email the document to the service provider as a JPEG or PDF, and their high-performance fax servers send the fax for you over suitable telephone service.

[MrTom]

In that scenario, you typically email the document to the service provider as a JPEG or PDF, and their high-performance fax servers send the fax for you over suitable telephone service.

I would hope that the gateway service provider would provide an encryption key so you can encrypt all the emails sent to them to fax. Since emails are an unencrypted transmission method, they go against what faxing stands for in the first place, security. So you may as well just email the document in the first place.