[nsporillo]

This is only possible if the call transits through all IP networks. If the call at any point goes over TDM, and out of band shaken is not implemented, then the signature is lost.

End to end authenticated calls is the ideal state, but I don't think we're fully there yet.

[harrall]

Definitely not even close to fully there yet but getting the VoIP providers to do it is an important step.

Rolling this out is like when the world first rolled out DKIM/SPF for email. You need to reach a critical mass of adoption before the data is useful.