1588 Timestamping Over Multi-Lane Physical Code Sublayers
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Solution Overview
Problem
Existing clock synchronization methods in packet-switched communication networks, such as Precision Time Protocol (PTP), face challenges with asymmetric path delays and variable latencies, which affect the accuracy of clock synchronization across distributed systems.
Innovation Solution
A method and device for time stamping packets in a multilane distribution environment, involving data stream adaptation, placeholder insertion for lane alignment, and timestamping, which adjusts for differences in data rates and buffer fill levels to ensure accurate timing information transmission across multiple lanes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If PTP is used for clock synchronization in packet-switched networks, then sub-microsecond synchronization accuracy can be achieved, but asymmetric path delays and variable latencies degrade the synchronization precision
Solution Approach 1:
The patent applies preliminary action by measuring and characterizing path delays in advance during network initialization or training phases. The system pre-calculates delay compensation values and stores them in lookup tables, enabling accurate timestamp adjustment without requiring continuous complex calculations during normal operation. This pre-characterization of network conditions resolves the issue of asymmetric and variable path delays.
Solution Approach 2:
The patent implements feedback mechanisms where receiving devices send delay information back to transmitting devices, allowing dynamic adjustment of timestamp calculations. The system continuously monitors actual transmission times and adjusts compensation values accordingly, creating a closed-loop system that adapts to changing network conditions and maintains synchronization accuracy despite path delay variations.
2Measurement precision
If data stream adaptation is performed to account for rate differences, then accurate timestamping can be achieved, but processing complexity and latency increase
Solution Approach 1:
The patent segments the data processing function into separate hardware blocks: a rate adaptation block that handles data rate conversion, a placeholder insertion block that manages alignment markers, and a timestamp engine that performs timing operations. This segmentation allows each block to be optimized independently and simplifies the overall processing architecture by distributing complexity across dedicated functional units rather than requiring a monolithic complex processor.
Solution Approach 2:
The patent introduces placeholder alignment markers as intermediary elements inserted into the data stream to synchronize timing information. These placeholders act as mediators between the rate adaptation process and the timestamping operation, providing reference points that enable accurate timestamping even when data rates differ. The placeholders temporarily occupy space in the data stream but are removed or replaced during transmission, minimizing their impact on overall processing complexity.
3Measurement precision
If placeholders are inserted for lane alignment markers, then multilane distribution can be properly synchronized, but data stream length and transmission time increase
Solution Approach 1:
The patent applies local quality by inserting placeholder alignment markers only at specific locations within the data stream where lane synchronization is needed, rather than uniformly throughout the entire stream. The placeholders are strategically placed at boundaries or synchronization points where lane alignment is critical, allowing precise multilane distribution synchronization without unnecessarily increasing the data stream length everywhere. This selective placement minimizes the time penalty while maintaining alignment accuracy where it matters most.
Data Source
AI summary
A physical layer device provides for synchronization of clocks in a communication network. A place holder for an alignment marker is inserted into a frame to be transmitted. Once the placeholder alignment marker is inserted into the frame, no additional data is added to the frame. Transmission of the frame including the placeholder alignment marker may also be delayed to allow data processing in subsequent blocks within a transmit block to complete prior to further processing of the frame including the placeholder alignment marker (e.g., timestamping, MACSec, etc.) to improve timing accuracy with a multi lane distribution environment.