Clock Synchronization Using Codeword Markers
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Solution Overview
Problem
Existing clock synchronization protocols in networked computer systems, such as IEEE1588, incur additional network overhead and bandwidth requirements due to the insertion of specific frames, which limits their ability to achieve sub-nanosecond accuracy in high-performance applications with numerous network nodes.
Innovation Solution
A method that utilizes codeword markers (CWMs) to calculate time offset and roundtrip delay by recording specific timestamps during datastream transmissions between a master and slave computer, allowing for clock synchronization without additional overhead, leveraging the unused bits in CWMs for timestamp insertion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If specific frames are inserted from MAC for clock synchronization (IEEE1588), then clock synchronization accuracy is improved, but network overhead and bandwidth consumption increase
Solution Approach 1:
The patent merges clock synchronization functionality with existing Ethernet data transmission by embedding timestamps within codeword markers that are already part of the data stream. This eliminates the need for separate synchronization frames, thereby reducing network overhead while maintaining synchronization accuracy.
Solution Approach 2:
The codeword marker is designed to serve multiple functions: it acts as both an Ethernet protocol element for data transmission and a carrier for clock synchronization timestamps. This multi-functionality allows the same signal to perform both data communication and time synchronization without requiring additional dedicated bandwidth.
2Reliability
If specific frames are inserted from MAC for clock synchronization, then clock synchronization is achieved, but additional bandwidth is required
Solution Approach 1:
The synchronization process is merged into the existing data transmission bandwidth by utilizing codeword markers that are already present in the Ethernet stream. This approach eliminates the need for dedicated synchronization bandwidth while ensuring reliable clock synchronization between master and slave computers.
3Measurement precision
If sub-nanosecond accuracy is required for high performance applications, then measurement precision is improved, but network overhead increases due to additional synchronization frames
Solution Approach 1:
The patent achieves sub-nanosecond accuracy by embedding precise timestamps within existing codeword markers in the data stream. This method provides the required measurement precision without increasing network overhead, as the timestamps are carried within the normal data transmission infrastructure rather than through additional synchronization traffic.
Data Source
AI summary
Aspects of the present disclosure includes a method and program product for clock synchronization of a networked computer system. The method records a time (t1) when a first codeword marker in a datastream is sent from a master computer to a slave computer and records a second time (t2) when the slave computer receives the first codeword marker. The method includes recording a third time (t3) when a third codeword marker in a datastream is sent from the slave computer to the master computer. The method includes recording a fourth time t4 when the master receives the third codeword marker from the slave. The method calculates a time offset θ, according to;θ=(t2-t1)+(t4-t3)2,and a roundtrip delay δ, according to δ=(t4−t1)−(t3−t2). The clock in the slave computer is synchronized with a clock in the master computer using θ and δ.