What will happen to T.38 fax at the border of 2 providers?

Question

Asterisk

Good time everyone.
We took a SIP trunk from one of the providers from the big three OPPSs. But it turned out that in our region we are the first client for them who takes telephony via SIP, so they don’t have any use cases. And as always there was a question with faxes through SIP. In principle, everything goes through G.711a, including to the network of other providers. But the inquisitive mind of 2 engineers does not allow to sit still. And I wanted to try T.38.
Before starting the experiments, I had a theoretical question that our provider cannot answer. And what will happen to T.38 at the border of our provider and another provider? What happens if our ISP sends a T.38 fax to an ISP's network where T.38 is not supported? There is at least one such provider in our region.
From our side we use:
- asterisk
- eltex tau-8.ip
- eltex tau-32m.ip
I don't know what the provider has.

Answer 1

Depends on what kind of interface they have with another provider. If SS7, then the fax will pass without problems. If by VOIP - there may be nuances. But for the most part, operators from the big three are joined by SS7.