STIR/SHAKEN is the US framework that lets carriers cryptographically attest that a caller ID has not been spoofed. The originating carrier signs each call with an attestation level of A, B or C. Calls with weak or no attestation are more likely to be labeled as spam or blocked.
Attestation depends on the carrier knowing the customer and their right to use the number, which is why an offshore floor's choice of US carrier affects how its calls are treated.
What the attestation levels mean
A, full attestation, means the carrier knows the customer and confirms they are allowed to use the calling number. B, partial attestation, means the carrier knows the customer but cannot confirm the number. C, gateway attestation, means the carrier is only passing the call along, typically from an international or unknown source. Analytics engines use this signal, among others, when deciding whether to warn the consumer.
Why it matters from Pakistan or India
A floor in Lahore dialing US numbers usually routes through a US carrier on a SIP trunk. If that carrier has verified the floor's account and numbers, calls can carry strong attestation. If calls enter through a route that cannot vouch for them, they may arrive with weak attestation and be treated as suspicious. Ask the carrier which level your calls carry and why.
Common mistakes
Assuming A attestation guarantees the call will not be labeled. Reputation and calling patterns still count.
Displaying numbers the business does not own or control. Carrier and FCC rules on this are strict and still changing, so confirm with your carrier and counsel.
Buying the cheapest route without asking how calls are signed.
How it shows up in reports
Most dialers do not show attestation directly. The effect shows up as a lower connect rate on a route or carrier. If one trunk connects worse than another on the same list at the same hour, ask both carriers how they are signing your calls. Rules and enforcement in this area are still developing, so confirm the current position with your carrier and counsel.