Distributed PTP Transparent Clock for Network Synchronization
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Solution Overview
Problem
Precision Time Protocol (PTP) systems face accuracy issues due to Packet Delay Variation (PDV) in network synchronization, particularly in high-accuracy applications, which requires additional latency and design complexity when implementing Boundary Clock (BC) or Transparent Clock (TC) functions in transport networks.
Innovation Solution
A distributed Transparent Clock method that measures and communicates the residence time of PTP packets across network elements via optical, electrical, or wireless channels, allowing for improved clock synchronization accuracy by compensating for variable queueing and processing delays without the need for protocol termination at each node.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Boundary Clock or Transparent Clock functions are implemented in transport networks to mitigate Packet Delay Variation, then clock synchronization accuracy is improved, but additional data path latency and design complexity are introduced
Solution Approach 1:
The patent segments the Transparent Clock function into distributed components across multiple network elements. Each network element independently measures residence time for PTP packets passing through it, and collectively they provide end-to-end delay compensation without requiring a single complex TC device. This segmentation reduces individual device complexity while maintaining synchronization accuracy.
Solution Approach 2:
The patent extracts the protocol termination function from the transport network, allowing PTP packets to pass through transparently without being terminated at each node. Only residence time measurement is performed, while the actual PTP protocol processing is handled by endpoint devices. This extraction reduces design complexity by removing queuing, discard, scheduling and classification functions from transport network elements.
2Measurement precision
If Boundary Clock or Transparent Clock functions are implemented to compensate for Packet Delay Variation, then clock recovery accuracy is improved, but additional data path latency is introduced
Solution Approach 1:
The patent extracts the protocol termination and processing functions from the data path, allowing PTP packets to traverse the transport network without being stopped for queuing, scheduling, or classification. Only lightweight residence time stamping is performed in-line, minimizing data path latency while still enabling accurate delay compensation for clock recovery.
Solution Approach 2:
The patent enables PTP packets to skip through the transport network elements without full protocol processing at each node. By performing only residence time measurement and leaving the packets to rush through to endpoints for termination, the system minimizes latency while maintaining the ability to compensate for delay variation.
3Measurement precision
If transport equipment terminates IEEE 1588 protocol at client interface to support phase synchronization, then synchronization accuracy is improved, but support for multiple independent client clock domains becomes complicated
Solution Approach 1:
The patent extracts the protocol termination function from transport network elements and relocates it to endpoint devices. This allows transport equipment to handle multiple independent client clock domains transparently without the complexity of terminating and managing multiple PTP instances, while still enabling synchronization accuracy through distributed residence time measurement.
Solution Approach 2:
The patent introduces distributed residence time measurement as an intermediary function that operates independently of protocol termination. This mediator provides the necessary delay compensation information without requiring the transport equipment to terminate or manage multiple client clock domains, thus maintaining both accuracy and adaptability.
4Measurement precision
If transport network synchronizes to customer's client signals to distribute synchronization, then synchronization accuracy is improved, but independence of transport network management is reduced
Solution Approach 1:
The patent extracts the protocol termination and clock domain management functions from transport network elements, allowing them to operate independently while still providing accurate synchronization. Transport networks perform only residence time measurement and forward PTP packets to endpoints that handle synchronization, maintaining both accuracy and management independence.
Data Source
AI summary
A distributed Precision Time Protocol (PTP) Transparent Clock (TC) provides a TC function based on overall residence time in a network at a server layer. That is, the server layer operates as a distributed TC for a corresponding client layer. A transport network includes a first node connected to a first client device; and a second node connected to a second client device over a server layer, wherein the first client device communicates to the second client device via a client layer, wherein the first node and the second node are synchronized to one another, and wherein the first node and the second node are configured to implement a distributed transparent clock on a PTP packet at the client layer, the distributed transparent clock includes a correction field in the PTP packet based on a residence time in the transport network at the server layer.