Can't Find Answer about Fax via T.38

[jpatel]

There is tons of information out there but I cannot seem to get the answer I need. Even when calling Flowroute (our SIP provider).
We are wondering, if we set up a analog POTS fax machine, via an ATA device, can we send fax to another analog fax?
I want to understand the basic flow of traffic, i.e. Analog fax--> T.38 modem/ATA --> 3CX --> Flowroute -?-> Analog Fax.
Is this possible or does the receiver have to have a T.38 fax machine?

It seems like such a basic question that I can't find the answer to.

 

[cobaltit]

You are over thinking it.You have no control over the receiving device or the carrier it's on. The receiving end doesn't know or care how the fax is sent.

 

[eddv123]

As @cobaltit has said the receiving FAX machine will be oblivious to how the FAX is sent, however a few points I would ensure you follow as in some circumstances FoIP can be a little fiddly to deploy.

* Get a supported Gateway device from 3CX for the sake of simplicity: https://www.3cx.com/voip-gateways/

* Your options for send FAX currently are T.38 and G711 pass-through, if you want to use T.38 ensure your provider supports this. According to this link https://www.3cx.com/partners/sip-trunks/usa/ Flowroute states "not working" for FAX.

* Only setup in local LAN mode or VPN to hosted system (not via SBC or STUN.

I would confirm point 2 with Flowroute as they may of made some changes (I am not familiar with how updated that link is) however it might explain why they could not answer your questions.

 

[jpatel]

@cobaltit, @eddv123 thanks for the info. Flowroute claims to support T.38, I just couldn't get an answer about if I send FoIP will an analog machine receive the fax. Why do you recommend not using a cloud instance for the ATA, we mainly work off of PBXExpress or other cloud based solutions?

 

[eddv123]

Why do you recommend not using a cloud instance for the ATA

Firstly because it is not supported by 3CX, but secondly FAX is very sensitive to delay and lost packets (which could then lead to failure of sending FAX) setting up the device via SBC or STUN adds more risk of this happening due to addition of conversions in the call path of the FAX:

Each >> is a potential conversion/traversal for FAX:

Sending FAX/media gateway >> Local IP network >> SBC or STUN connection >> 3CX >> Trunk provider >> Provider network/PSTN >> Receiving end provider >> IP network or direct to analogue FAX.

Where I have known (and have done this myself) with 3CX it is very messy, and at least for me required a lot of manual changes/tweaks to settings such as Transmission speeds etc.

 

[jpatel]

@eddv123 What are your recommendations for someone reliant on faxing via machine, but has a Cloud based PBX? what all options do you purpose as a solid fix or alternative to a traditional Fax?

 

[eddv123]

Where you can I would move to e-FAX online FAX service, if for reasons of business (Solicitors for example have a legal requirement over here to send in FAX format) that absolutely stipulates you must have a FAX machine I would use a VPN tunnel.

This is easily said, however the provider must support hosted software firewalls on their solution so you can build the VPN to site, I have done this with Google (custom build) and V1: https://www.virtual1.com/

For any type of gateway I always recommend Patton, but have used Grandstream ATA's in the past when Patton are not available.

 

[cobaltit]

@cobaltit, @eddv123 thanks for the info. Flowroute claims to support T.38, I just couldn't get an answer about if I send FoIP will an analog machine receive the fax. Why do you recommend not using a cloud instance for the ATA, we mainly work off of PBXExpress or other cloud based solutions?

Seems like you might still be missing the point. How you send the fax (T.38, g.711, web fax service, etc) has no bearing on the receiver's ability to receive the fax. So yes to answer your question, any method you can use to successfully send a fax, including T.38, can be used to fax to ANY other fax destination, including an analog fax.

Regarding my recommendation, we give our customers the option of keeping a POTS line or we sell them a 'store and forward' ATA using our fax service. Anything else is just rolling the device. The recommendation by @eddv123 removes some of the potential errors but FoIP is just not reliable for anyone who depends on faxes, especially multi-page faxes. It's great for the occassional fax and we have a lot of success receiving faxes via T.38 and 3CX but sending faxes is not something VoIP does wel.

 

[jpatel]

@cobaltit Do you still use ATA if you're installing a cloud instance of 3CX? or recommend POTS at that point?

 

[cobaltit]

If losing one fax because it's time sensitive would cost your client more than $50-60/month then we keep an analog line or use our 'store and forward' ATA. The way our ATA works it the machine faxes to the ATA and then the ATA sends it via HTTPS up to the data center. The data center then processes the fax from there. For incoming it's transferred via HTTPS to the ATA and then the ATA 'calls' the fax machine to deliver. HTTPS is designed for IP networks so it's much more reliable.

I basically tell customers if you care about faxes, do one of those two things. If they insist on trying it with an regular ATA we do it and the first time they complain I make them do one of the two options I mentioned. For cloud, one of the two options is my only recommendation unless there either happens to be a VPN in place or we are putting one in place for a 'local' (as far as 3CX is concerned" install. While we have edge cases where we've manually configured ATA's we try to keep our environments fully 3CX supported and only stray as a last resort.