At a glance
- PSTN copper is retiring – Telecom carriers are rapidly phasing out analog copper lines, requiring urgent migration for voice, alarm, and elevator circuits.
- Cross-border trust required – STIR/SHAKEN frameworks now enforce cryptographic call authentication tokens to stop spoofed numbers across international borders.
- Prevent spam call flagging – Unauthenticated or C-attestation enterprise outbound calls risk aggressive carrier blocking or "Spam Likely" labeling.
- Specialized circuit conversion – Life-safety lines, fire alarms, and POS terminals require certified cellular or All-IP bridge appliances with battery backup.
- Best practice – Audit carrier signing certificates and achieve Full Attestation (Level A) across all outbound corporate DIDs before PSTN shutoff dates.
The telecommunications industry is completing its historic shift from legacy Time Division Multiplexing (TDM) copper infrastructure to all-IP voice networks. At the same time, call authentication standards are evolving to address global fraud. The Cross Border Call Authentication Governance Authority (CBCA-GA) secured official Secure Telephone Identity Governance Authority (STI-GA) interoperability approval in September 2026, establishing a framework to verify international calling traffic. This guide examines how the all-IP transition impacts business lines, how cross-border STIR/SHAKEN works, and how to prevent outbound business calls from being flagged as spam.
The All-IP Transition: Why Copper TDM Is Dead
For over a century, public telecommunications relied on copper wire pairs and Time Division Multiplexing (TDM) over analog Plain Old Telephone Service (POTS) and digital T1/PRI circuits. That era has definitively closed.
Under Federal Communications Commission (FCC) regulatory relief orders, incumbent local exchange carriers (ILECs) like AT&T, Verizon, and Lumen are no longer obligated to maintain legacy copper networks. Central offices are decommissioning aging Class 5 digital switches and replacing them with high-density IP routers. To encourage migration, carriers have increased tariffs on remaining analog copper lines by 200% to 500% over the last four years.
For business enterprises, remaining analog circuits—such as building elevator phones, fire alarm panels, emergency call boxes, security gates, and legacy fax machines—must be converted to all-IP cellular or broadband POTS replacement gateways to ensure continuity and avoid steep tariff penalties.
Why Domestic STIR/SHAKEN Left an International Vulnerability
In 2021, the FCC mandated the STIR/SHAKEN framework across US telecommunications networks to combat caller ID spoofing and illegal robocalling. STIR/SHAKEN uses cryptographic public-key certificates to sign SIP call headers, assigning one of three attestation ratings:
- Full Attestation (A-Level): The service provider knows the customer’s identity and confirms they have the verified legal right to use that telephone number. Displays as verified caller ID.
- Partial Attestation (B-Level): The provider verifies the call originated from a known customer, but cannot verify the customer owns the specific caller ID number presented.
- Gateway Attestation (C-Level): The provider merely received the call from an external gateway or transit carrier with zero visibility into origin. Frequently tagged as “Spam Likely” or blocked.
While domestic STIR/SHAKEN significantly reduced spoofing originating inside the United States, fraudulent call syndicates quickly shifted operations overseas. Because foreign carriers generally lacked digital certificates recognized by the US STI-GA, international calls entering US border gateways could only receive C-Level gateway attestation.
This created substantial collateral damage for legitimate multinational enterprises. Outbound calls placed by overseas support teams, international suppliers, and regional offices in Canada, Europe, or Asia were routinely tagged as “Fraud Risk” or blocked outright by US mobile operators.
The CBCA-GA Breakthrough: Cross-Border Call Authentication
To establish trust across international voice boundaries, global telecommunications leaders established the Cross Border Call Authentication Governance Authority (CBCA-GA). Founding members of the oversight committee include industry giants:
- Bandwidth
- Microsoft
- RingCentral
In September 2026, the CBCA-GA secured official STI-GA interoperability approval. This approval allows cross-border cryptographic tokens to be recognized mutually between participating international networks and the US Secure Telephone Identity Governance Authority root of trust.
When an authorized enterprise user in London or Toronto initiates an outbound call to a customer in New York via a CBCA-participating carrier, the originating carrier cryptographically signs the call with a validated CBCA token. Upon reaching the US gateway, the terminating carrier verifies the signature against the STI-GA trust anchor. The call retains its A-Level Attestation, displaying a verified caller name rather than a spam warning on the recipient’s mobile phone.
The Direct Business Impact of Authentication Gaps
Call authentication directly impacts contact rates and operational efficiency:
Answer Rate Collapse: Industry telecommunications data demonstrates that unauthenticated or unverified outbound business calls achieve average answer rates between 4% and 8%. In contrast, calls displaying verified caller ID names achieve answer rates between 18% and 26%.
FCC Verification Mandates: The FCC has proposed regulations requiring terminating voice service providers to pass verified caller name data on all A-level authenticated calls. Carriers are tightening filtering algorithms, meaning unauthenticated enterprise traffic faces an increasing probability of call blocking.
Brand Protection: Without cryptographic authentication, bad actors can spoof your company’s published telephone numbers. When customers receive fraudulent calls displaying your caller ID, brand reputation and customer trust suffer immediate damage.
5 Questions to Ask Your VoIP Provider Today
To ensure your corporate calling traffic remains verified and accessible throughout the all-IP transition, review these questions with your business phone provider:
- 1. What is your all-IP retirement timeline for remaining TDM trunks? Confirm when your provider will discontinue legacy PRI connections and migrate remaining traffic to pure SIP trunking.
- 2. Does your network participate in the CBCA-GA cross-border framework? Verify whether calls originating from your international branches receive authenticated token pass-through when terminating in the United States and Canada.
- 3. What percentage of our outbound calls achieve A-Level attestation? Request monthly attestation metrics within your administrative reporting dashboard to verify your numbers are properly registered.
- 4. Do you support Rich Call Data (RCD) and Branded Calling? Inquire whether your provider supports transmitting your verified business name and company logo directly to terminating mobile handsets.
- 5. What is your remediation procedure for erroneous spam labels? If your primary numbers are mistakenly flagged as “Spam Likely” by wireless carrier analytics engines (such as Hiya, First Orion, or T-Mobile Scam Shield), how quickly can the provider resolve the registration error?
Frequently Asked Questions
Why are our outbound business calls labeled “Spam Likely”?
If your VoIP provider lacks an authorized STIR/SHAKEN certificate, routes traffic through low-cost secondary wholesale gateways, or has not registered your numbers in carrier analytics registries, terminating mobile networks assign low reputation scores, resulting in spam warnings.
Does STIR/SHAKEN completely eliminate robocalls?
No. STIR/SHAKEN does not determine whether call content is desirable; it verifies that the caller has legal authorization to use the displayed caller ID number. However, by establishing cryptographic accountability, it allows carriers and law enforcement to trace and disconnect fraudulent callers quickly.
How does the all-IP transition affect fire alarms and elevators?
Analog copper lines provided their own electrical loop current, allowing emergency elevator and fire alarm systems to operate during local power failures. All-IP POTS replacement appliances must include dual cellular/broadband connectivity and battery backup systems meeting NFPA 72 fire code requirements.
