> Easy fix. It should be opt-in to accept a call that is routed through one of these.
Easier (and correct) fix: Telecoms operators should not be permitted to provide transit to a call that's routed through one of these.
> I know they allow it so some grandma in rural France that still uses a dial phone on a copper line that hasn't been touched since 1962...
This doesn't make sense. Even my inexpensive Mikrotik switches can augment packets with the ID of the port that they originated from. I do not believe for even a second that Telecoms Grade switching equipment is unable to do the same. The fact that that grandma can send and receive calls tells you that both that that equipment exists and that it knows what port her phone is connected to.
> I do not believe for even a second that Telecoms Grade switching equipment is unable to do the same
Mikrotik is a young spring chick compared to the dinosaurs in telecom.
> I do not believe for even a second that Telecoms Grade switching equipment is unable to do the same.
The example should rather have been some telecom carrier in Africa or India. Telco equipment is expensive, the technology is ridiculously complex and getting companies especially in less well-off regions to replace aging stuff and updating it to modern standards is next to impossible. Think about it, the globally connected phone system includes countries where you get 10 GBit/s symmetric fiber in your home and it includes countries where people don't even have running water because they're so poor.
The fact that we in Western countries can have a realtime conversation with someone in the Saharan desert or in an Indian village that requires days worth of travel [1] is nothing short of a miracle.
[1] https://www.aljazeera.com/gallery/2024/5/8/an-election-booth...