OTN Clock Synchronization via Delay Measurement
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Solution Overview
Problem
Current network element clock synchronization methods, such as GPS and NTP, fail to achieve microsecond accuracy required for precise packet delay, jitter, and throughput measurements, leading to increased costs and complexity due to the need for GPS receivers and limitations in latency estimation.
Innovation Solution
The method utilizes Optical Transport Network (OTN) delay measurements to synchronize network element clocks by transmitting time-stamped packets and adjusting clocks based on delay measurements, eliminating the need for GPS synchronization and providing microsecond accuracy without relying on NTP.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS synchronization is used to achieve microsecond accuracy, then clock synchronization precision is improved, but device complexity and cost increase due to requiring GPS receivers at each network element
Solution Approach 1:
The patent introduces an intermediary approach by using NTP servers as mediators to provide time reference information to network elements. Instead of requiring direct GPS receivers at each network element, the NTP servers act as intermediaries that distribute synchronized time information through standard network protocols, thereby reducing device complexity while maintaining synchronization capability
Solution Approach 2:
The patent replaces the mechanical/GPS-based synchronization system with an electronic/software-based NTP system. By substituting physical GPS receivers with network-based time protocol software, the solution eliminates hardware complexity while achieving the required microsecond-level synchronization accuracy through software implementation
2Device complexity
If NTP protocol is used to synchronize network element clocks, then device complexity is reduced, but measurement precision deteriorates due to unknown latency between network elements
Solution Approach 1:
The patent implements feedback mechanisms by having network elements send time-stamped packets to NTP servers and receiving correction information based on measured round-trip delays. The NTP servers calculate timing offsets and provide feedback adjustments to network elements, enabling continuous refinement and compensation for network latency variations to achieve microsecond accuracy
Solution Approach 2:
The patent applies preliminary action by having network elements perform advance time synchronization with NTP servers before conducting packet delay measurements. This preliminary synchronization establishes a known reference time baseline, allowing subsequent measurements to be accurately correlated despite network latency variations
Data Source
AI summary
The present disclosure provides Network Element (NE) clock synchronization using Optical Transport Network (OTN) delay measurement systems and methods such as described in ITU-T G.709 (December 2009) “Interfaces for the Optical Transport Network (OTN)” and G.798 (October 2010) “Characteristics of optical transport network hierarchy equipment functional blocks”. OTN provides a Delay Measurement (DM) function to measure fiber path latency between two network elements to within microsecond accuracy. The convergence of packet switching and OTN transport into the same network element allows the sharing of this information between the two applications. The OTN delay measurement value can be used to synchronize two network element clocks to within microsecond accuracy without the need for a costly GPS synchronization solution or reduced accuracy NTP solutions.