What is Carrier Transparency?
What is Carrier Transparency?
Section titled “What is Carrier Transparency?”Carrier transparency is made up of three core mechanisms: call blocking, call labels, and caller name (CNAM) registration. Together, these give consumers and businesses more information about who is calling and why. None of these mechanisms are foolproof, but they represent meaningful progress in reducing spam and fraud calls across North American networks.
Call Labels From Carriers
Section titled “Call Labels From Carriers”Carriers display warning labels on incoming calls to help consumers decide whether to answer. Common warning labels include:
- Fraud Risk
- High Risk
- Potential Scam
- Potential Fraud
- Scam Likely
In addition to risk labels, carriers also apply intent labels to indicate the nature of a call. These can specify an organization or even a department:
- Survey
- Non-profit
- Political
- Charity
- Informational
- Telemarketing
Call-Blocking Notifications
Section titled “Call-Blocking Notifications”When a call is blocked, SIP headers include notification codes that provide some insight into why:
| SIP Code | Meaning |
|---|---|
| 603 | Call blocked — no explanation provided |
| 607 | Recipient rejected the call |
| 608 | Upstream intermediary rejected the call (contact info provided for remediation) |
SIP 608 is the most actionable, as it includes contact information that can be used to request removal from a block list.
CNAM Registration
Section titled “CNAM Registration”Businesses can register their phone number with CNAM databases to display a recognizable name on the recipient’s caller ID. This increases answer rates and reduces the likelihood of being labeled as spam.
For more detail on how CNAM works, see What is CNAM?