Quick Overview

The PSTN sunset refers to the ongoing retirement of legacy copper and TDM voice networks in favor of modern IP infrastructure. In the United States, the FCC has already relaxed key copper-related obligations and is considering additional changes that could accelerate all-IP interconnection. For service providers, the transition is more than a regulatory milestone. It is an opportunity to modernize operations, reduce costs, strengthen security, and create new service revenue.

Ribbon helps service providers migrate POTS and TDM services to IP through a phased approach built on Session Border Controllers, Media Gateways, virtualization and cloud-native software, helping maintain service continuity throughout the transition.

What Is the PSTN Sunset?

The Public Switched Telephone Network (PSTN) has been the foundation of voice communications for decades. Built on copper infrastructure and circuit-switched technology, it powered traditional telephone services commonly known as Plain Old Telephone Service (POTS). Today, service providers are replacing legacy TDM networks with IP-based communications platforms that are more efficient, scalable, secure, and cost-effective to operate. The PSTN sunset is not a single event or nationwide shutdown date. Instead, it is the continued migration away from aging copper infrastructure and legacy voice technologies toward all-IP networking.

Two related forces are driving this transition:

  • Service providers are retiring copper facilities and TDM services based on their own modernization plans.
  • The U.S. Federal Communications Commission (FCC) continues to update regulations that were originally designed for legacy telecommunications networks.

Both trends point in the same direction: the future of voice communications is IP.

What FCC Actions Are Driving the Transition?

Two FCC actions are particularly important for providers operating in the United States.

FCC-19-72

Effective August 2, 2022, FCC-19-72 removed certain requirements for incumbent local exchange carriers (ILECs) to provide new TDM-based services or maintain specific copper facilities for competitors at regulated rates. The order did not establish a national shutdown date for the PSTN. However, it removed regulatory frameworks that had supported legacy network deployments, encouraging providers to accelerate migration planning.

FCC-25-73

In 2025, the FCC adopted FCC-25-73, a Notice of Proposed Rulemaking (NPRM) that proposes ending certain incumbent local exchange carrier interconnection obligations by December 31, 2028. Because this is a proposal rather than a final rule, the requirements are not yet finalized. Even so, the proceeding provides a strong indication of the direction of U.S. telecommunications policy and reinforces the industry's shift toward all-IP interconnection.

For service providers, the message is clear: migration planning should already be underway.

What Are My Compliance Obligations?

Network retirement requires more than replacing technology. Providers must follow established processes designed to protect customers and maintain service continuity.

A successful retirement strategy typically includes:

  • Identify Impacted Services. Inventory all POTS lines, TDM services, and dependent applications, including alarm systems, security systems, elevator phones, fax services, and other devices that may rely on legacy infrastructure.
  • Communicate Early. Notify affected retail and wholesale customers well in advance of planned changes. Communications should clearly explain timelines, service impacts, and available replacement options.
  • Build a Migration Plan. Define the IP-based technologies that will replace legacy services and establish a transition plan that minimizes disruption.
  • Complete Required Filings. Where applicable, submit required certifications and network retirement notifications in accordance with FCC requirements.
  • Execute a Controlled Migration. Move services in phases while maintaining reliability, customer experience, and business continuity.

What Replaces POTS and TDM Services?

Modern communications networks are increasingly built on software-based IP architectures rather than dedicated TDM hardware. The evolution typically follows a progression from physical network functions (PNFs) to virtual network functions (VNFs) and ultimately to cloud-native network functions (CNFs). This transition creates opportunities to reduce operational complexity while improving scalability and service agility. Ribbon supports every stage of that journey.

Secure Interworking Between Legacy and IP Networks

Session Border Controllers and Media Gateways provide secure connectivity between legacy TDM environments and modern IP networks.

Virtualize Core Network Functions

Software-based network functions running on commercial off-the-shelf hardware help reduce infrastructure costs and simplify operations.

Adopt Cloud-Native Architectures

Cloud-native platforms support faster service deployment, automated operations, improved scalability, and long-term infrastructure flexibility.

How Can Providers Migrate Without Disrupting Service?

The most successful migrations are phased rather than abrupt. A gradual transition allows providers to support both legacy and IP users during the migration period while maintaining operational stability. Session Border Controllers play a critical role in this process. In many deployments, SBCs can provide survivability functions and maintain essential calling capabilities if connectivity to a primary communications platform is interrupted. This approach enables providers to modernize infrastructure while reducing operational risk and preserving customer confidence.

Beyond Compliance: Why Modernization Matters

Viewing the PSTN sunset as a regulatory exercise alone can limit its business value. The transition to all-IP networking creates opportunities to improve efficiency, strengthen security, and introduce new revenue-generating services.

  • Modernize: IP-based architectures support greater scalability, simplified operations, and lower total cost of ownership while providing a foundation for future communications services.
  • Secure: Today's threat landscape extends well beyond traditional voice environments. Modern IP architectures support advanced security capabilities, including robocall mitigation, traffic analysis, and real-time threat detection.
  • Monetize: All-IP infrastructure enables providers to deliver services such as SIP trunking, hosted communications, unified communications, HD voice, AI-enabled communications experiences, and wholesale interconnection services.

Why Choose Ribbon?

Ribbon combines proven telecommunications expertise with a portfolio designed for every stage of network modernization. From Media Gateways and Session Border Controllers to virtualized and cloud-native communications platforms, Ribbon helps providers evolve from legacy infrastructure to modern IP networks while protecting service continuity. The goal is not simply to meet regulatory requirements. It is to build a more efficient, secure, and profitable communications network for the future.

Frequently Asked Questions

Is the PSTN Sunset an FCC Mandate?

No. The FCC has not established a single nationwide date for shutting down the PSTN. Instead, it has modified regulations governing legacy infrastructure and proposed additional changes that support the industry's transition to IP.

When Will the PSTN Be Shut Down?

There is no single shutdown date. Network retirement timelines vary by provider, location, and service type. The FCC's proposed December 31, 2028 date relates to specific interconnection obligations rather than a complete shutdown of all services.

What Replaces a POTS Line?

Common replacements include SIP trunking, hosted voice services, and cloud communications platforms connected through Session Border Controllers and Media Gateways. Certain specialized applications should be assessed individually to ensure compatibility.

Does the FCC PSTN Sunset Apply Outside the United States?

No. FCC regulations apply only within the United States. Other countries are managing their own transitions from legacy telecommunications infrastructure according to local regulatory frameworks and timelines.