FXS extension and cloud PBX

[PrismaComputer]

Hello,

I know this has been already discussed here:
https://www.3cx.com/community/threads/fxs-gateway-for-3cx.50369/

But 4 questions:

1. Are there any updates regarding this scenario (FXS extension for a cloud hosted PBX)
2. Why 3CX limits the provisioning method to local LAN (in the office) What's the technical background?
3. Why is it not possible to allow use of FXS extension outside the LAN (Remote extensions using Direct SIP or STUN)? What's the technical background?
4. We set up (as workaround) a "normal" extension with a Grandstream HT812, allowed extension outside the LAN, and analogue FAX (inbound AND outbound) works perfectly. Did everybody do this before? What downside do we have to expect?

 

[leejor]

There is no technical reason why a SIP ATA won't work when using a hosted PBX. You will just have to set it up manually. The only reason that I can think of for this being the case (not officially supported), is demand, or lack thereof. The majority of users probably make use of SIP sets. It may not be worth the time testing compatibility of ATAs for every situation. Someone at 3CX would have to provide the definitive answer.

 

[PrismaComputer]

"you will just have to set it up manually" - yes, sure.
But it's not possible to allow use of FXS extension outside the LAN (Remote extensions using Direct SIP or STUN will be blocked).

With "normal" extensions you're able to disable the security setting "Disallow use of extension outside the LAN (Remote extensions using Direct SIP or STUN will be blocked) ". Within a FXS extension this setting does not exist. That's the main problem, and that's why we used a "normal" extension.

And, therefore the question: Are the any downsides to expect from FXS over "normal" extension?

 

[leejor]

Honestly, I have not yet encountered an ATA being blocked when using STUN, all of the "remote" ones i use personally, are used that way. I have not had any use for Direct SIP when using 3CX so i can't comment on it's use. Perhaps in newer 3CX versions, for security reasons, there are now restrictions on how they can be deployed. I know that many try to use a Fax machine (extension), on an ATA remotely, and that is blocked because of endless issues.

 

[eddv123]

The main issue with FAX (especially T.38) is that conversions add delay which effects the FAX tones and in a lot of cases cause the FAX to fail.

By conversions I mean T.30 to IP then potentially back again in the provider network and back to IP and the T.30 at the other FAX machine.

Adding STUN for example adds another network and conversion into the mix and increases the chance of failure.

I can personally say that analogue telephones should not be an issue but save yourself the headache and use a VPN to the cloud instead, they are very easy to setup and are offered by most now.

If you are still wanting to try this the I think you would have more chance of success by using G.711 pass through than T.38.