See The Data Behind AT&T, Verizon, and Other TDM Turndown Case Studies

Major carriers across the globe are executing their TDM turndown strategies at varying paces, creating a complex landscape for enterprises and service providers to navigate. This comprehensive overview examines why do it, announced timelines, completed migrations, and lessons learned from carrier implementations worldwide. Here are the latest TDM Turndown Case Studies as of December 1, 2024.

The TDM Turndown Motivation – Infrastructure Support Challenges

According to Rob Jodrie, Director of Technical Support at Syncworks, network operators face mounting pressure to migrate from TDM due to critical support challenges. “Much of the TDM network is comprised of systems that were manufacturer discontinued (MD) years ago,” explains Jodrie. “Operators are forced to procure parts from the ‘gray market’ in an attempt to keep this equipment limping along.” 

Additional Key Concerns Include:

• Discontinued equipment with limited replacement parts
• Unreliable gray market components at premium prices
• Excessive power consumption compared to modern systems
• Limited alarm surveillance capabilities
• Critical services dependencies (E-911, SS7 call processing)

This industry insight directly aligns with the following carrier migration timelines and their associated TDM turndown case studies. Aging infrastructure increasingly impacts network reliability and operational costs. These negative draws will continue to deepen with time.

TDM Turndown Case Studies

AT&T Network Evolution

AT&T’s TDM turndown case study represents one of the industry’s most ambitious transitions. The carrier has filed to decommission TDM services across multiple states¹:

• California: 13,000 business customers migrated by Q3 2023
• Texas: 15,000 TDM circuits decommissioned as of Q4 2023
• Florida: Migration completion scheduled for Q4 2024
• Expected completion of nationwide TDM turndown: 2026²

Verizon’s Migration Strategy

One of the TDM turndown case studies is Verizon’s. Their approach emphasizes customer communication and phased implementation:

• Completed migration of 150,000 business customers across six states³
• Northeast corridor migration: 89% complete as of Q1 2024
• Projected completion date for copper retirement: 2025⁴
• Investment in fiber infrastructure: $4.5 billion allocated⁵

CenturyLink/Lumen Technologies

Following their merger and rebranding, Lumen has accelerated their TDM turndown:

• 18 states completed TDM-to-IP transition
• 1.2 million voice lines migrated⁶
• Rural market strategy includes fixed wireless alternatives
• Target completion date: 2027⁷

International Carrier Implementations

British Telecom (BT)

• Digital Voice transition affecting 29 million lines
• £12 billion fiber investment program
• Complete PSTN switch-off by December 2025⁸

Deutsche Telekom

• IP migration completed in 2019
• 20 million customers transitioned
• Three-year implementation timeline⁹

Implementation Challenges and Solutions

AT&T’s Approach

• Dedicated migration teams by region
• Customer communication 24 months before transition
• Specialized support for critical infrastructure customers
• Regular FCC filing updates on progress¹⁰

Verizon’s Methodology

• Proactive circuit auditing
• Customer premise equipment assessment
• Security system verification process
• Emergency services coordination¹¹

Lessons Learned from Completed Migrations

1. Pre-Migration Assessment
   • Average discovery of 23% more active circuits than initially documented
   • Critical timing dependencies often overlooked
   • Security systems frequently overlooked in initial assessments
2. Customer Communication
   • 24-month notice proven most effective
   • Regular status updates reduce support calls
   • Dedicated support teams improve customer satisfaction
3. Implementation Timing
   • Average migration timeline: 18-36 months
   • Critical infrastructure requiring additional 6-12 months
   • Weather considerations for outdoor equipment replacement

References

For detailed migration planning guidance, refer to our Network Migration Planning Guide, and for business impact analysis, see our Enterprise Impact & Implementation Case Studies.

About Us Syncworks

For over twenty years, Syncworks has been evaluating, testing, designing, and implementing timing networks for telecom, cable, utility, and enterprise customers in the US and the Caribbean. We are a well-known and trusted partner and critical supplier to major network operators. As a diamond partner to Microchip and a skilled integrator of other vendor products, we can provide options for the most performant, resilient, and economical timing network possible. We specialize in ensuring that critical networks can survive disruptions like GPS jamming and spoofing. And we provide expert support, sparing, and repairs for everything we install leveraging the largest inventory of related products and components in the industry. 

Syncworks is a value-added stocking reseller of network sync and timing equipment for critical infrastructure companies. SyncCare and Field Services ensure your network equipment is flawlessly executed and supported.  

Our 10,000 sq. ft. warehouse stocks and ships critical equipment and replacements for networks all across the USA and the Caribbean. With expertise from GPS signal to our new output expansion panels, we an experience and trusted guide. Our tight-knit crew of engineers and field services technicians work together to efficiently and effectively bring your network to Stratum 1 standards.

Syncworks delivers the highest level of expertise to every project and offers a complete menu of network synchronization products and services. Our flagship product, the TimeProvider® 4100, is a gateway clock that accepts multiple inputs from Global Navigation Satellite Systems (GNSS), Synchronous Ethernet (SynE), and 1588 PTP Grandmaster Clock and E1/T1 digital transmission links.  

As a Microchip Diamond Partner, we maintain the largest and most diversified stocking supply of Microchip network sync & timing products to meet our customers’ every need when it comes to sync and timing technology.  

For more information, contact sales@syncworks.com or call (904) 280-1234

Sunsetting Time Division Multiplexing (TDM)

TDM Turndown: Network Migration Planning Guide from Syncworks

The telecommunications industry’s TDM turndown represents one of the most significant infrastructure migrations in network history. As carriers decommission Time Division Multiplexing (TDM) networks worldwide, engineering teams face increasingly complex challenges in maintaining service continuity while transitioning to IP-based solutions. This comprehensive TDM Turndown: Network Migration Planning Guide addresses the essential requirements and protocols for successful migration, based on data from recent carrier implementations.

Requirements Checklist for TDM Migration

Network Assessment Phase

• Circuit inventory and classification by type and criticality
• Peak traffic pattern analysis across voice and data services
• Timing dependencies for synchronous applications
• Interface compatibility across vendor platforms
• Current synchronization topology and requirements mapping

Synchronization Architecture

Transitioning from TDM to packet-based networks fundamentally changes timing distribution methods. Current TDM networks use hierarchical synchronization distribution with Stratum timing standards, requiring careful planning for:

1. Precision Time Protocol (PTP) IEEE 1588v2
   • Grandmaster clock deployment strategy
   • Boundary clock positioning
   • Transparent clock implementation
   • Application-specific PTP profiles
2. Synchronous Ethernet (SyncE)
   • Physical layer frequency distribution
   • Enhanced Synchronization Status Messaging (ESMC)
   • Clock quality level monitoring
   • Hybrid SyncE/PTP deployment options

Protocol Migration Pathways

AT&T’s recent migration of 30,000 circuits revealed the importance of systematic protocol transition:

1. Circuit Assessment
   • E1/T1 circuit mapping and dependencies
   • DS3/E3 high-capacity link inventory
   • SONET/SDH ring topology documentation
   • Multiplexing hierarchy verification
2. Packet Network Preparation
   • MPLS infrastructure validation
   • Circuit Emulation Service (CES) testing
   • QoS policy implementation
   • Network timing distribution verification

TDM Turndown: Network Migration Planning Guide: Risk Mitigation Strategies

Critical Systems Protection

1. Emergency Services Infrastructure
   • PS-ALI database transition planning
   • E911 circuit redundancy requirements
   • Call center failover procedures
   • Location service accuracy validation
2. Industrial Control Systems
   • SCADA network transition requirements
   • RTU compatibility assessment
   • Control center communication pathways
   • Backup system verification protocols

Testing and Validation

Based on CenturyLink’s successful migration framework:

1. Pre-migration baseline metrics
2. Interface compatibility testing
3. Timing accuracy verification
4. End-to-end service validation
5. Failover scenario testing

Migration Execution Framework

Phase 1: Network Preparation

• Packet network infrastructure deployment
• Timing distribution solution implementation
• QoS policy configuration
• Monitoring system establishment

Phase 2: Service Migration

• Circuit-by-circuit transition scheduling
• CPE upgrade coordination
• Protocol conversion deployment
• Service testing and validation

Phase 3: Legacy Decommissioning

• TDM equipment power-down procedures
• Circuit discontinuation process
• Equipment removal scheduling
• Documentation updates

TDM Turndown: Network Migration Planning Guide Success Metrics

1. Network Performance Indicators
   • Packet loss rates < 0.001%
   • Jitter < 5ms
   • Timing accuracy within 1.5μs
   • Service availability > 99.999%
2. Migration Progress Tracking
   • Circuits migrated vs. total inventory
   • Equipment decommissioning status
   • Customer cutover completion rates
   • Issue resolution timing

For real-world implementation examples and business impact analysis, including ROI calculations and enterprise case studies, refer to our companion articles:

• Planning Guide
• TDM Case Studies
• Enterprise Impact & Implementation

About Us Syncworks

For over twenty years, Syncworks has been evaluating, testing, designing, and implementing timing networks for telecom, cable, utility, and enterprise customers in the US and the Caribbean. We are a well-known and trusted partner and critical supplier to major network operators. As a diamond partner to Microchip and a skilled integrator of other vendor products, we can provide options for the most performant, resilient, and economical timing network possible. We specialize in ensuring that critical networks can survive disruptions like GPS jamming and spoofing. And we provide expert support, sparing, and repairs for everything we install leveraging the largest inventory of related products and components in the industry. 

Syncworks is a value-added stocking reseller of network sync and timing equipment for critical infrastructure companies. SyncCare and Field Services ensure your network equipment is flawlessly executed and supported.  

Our 10,000 sq. ft. warehouse stocks and ships critical equipment and replacements for networks all across the USA and the Caribbean. With expertise from GPS signal to our new output expansion panels, we an experience and trusted guide. Our tight-knit crew of engineers and field services technicians work together to efficiently and effectively bring your network to Stratum 1 standards.

Syncworks delivers the highest level of expertise to every project and offers a complete menu of network synchronization products and services. Our flagship product, the TimeProvider® 4100, is a gateway clock that accepts multiple inputs from Global Navigation Satellite Systems (GNSS), Synchronous Ethernet (SynE), and 1588 PTP Grandmaster Clock and E1/T1 digital transmission links.  

As a Microchip Diamond Partner, we maintain the largest and most diversified stocking supply of Microchip network sync & timing products to meet our customers’ every need when it comes to sync and timing technology.  

For more information, contact sales@syncworks.com or call (904) 280-1234