What STIR/SHAKEN is
The originating carrier signs the calling number and puts the signature in the SIP Identity header. The terminating carrier verifies it and tells the subscriber whether the number can be trusted. The US and Canada use it against caller ID spoofing; France, the UK and others are rolling out similar schemes.
Attestation A, B, C
- A — full: the carrier knows the customer and their right to the number.
- B — partial: the customer is known but the number is not verified (e.g. via a customer PBX).
- C — gateway: the carrier only received the call from elsewhere (international gateway).
The whole call
The full SIP exchange with a ladder and SDP analysis is in the SIP log analyzer.