Sunsetting Time Division Multiplexing (TDM)

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 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

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

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 article on TDM turndown enterprise strategies.

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