Data Network Clock Synchronization Without Frequent Cross-Domain Queries
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Solution Overview
Problem
In data networks with multiple clock domains, such as Ethernet-based PTP and PCIe-based PTM, frequent queries between domains for time synchronization result in increased network traffic and latency, particularly when PCIe devices need to send time-specific requests to PTP devices, stressing bandwidth resources.
Innovation Solution
Implement synchronization circuitry that periodically calculates the rate of drift between clock domains, allowing nodes to determine the time in another domain based on their own clock domain's time and the calculated drift, reducing the need for frequent network queries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If frequent network queries are used for time synchronization between clock domains, then time accuracy is maintained, but network traffic increases and latency increases
Solution Approach 1:
The system performs preliminary drift rate calculations between clock domains and stores these results for later use. Instead of querying the target clock domain frequently, nodes use the pre-calculated drift rates to estimate time in other domains, significantly reducing network traffic while maintaining acceptable time accuracy.
Solution Approach 2:
The patent introduces drift rate as an intermediary parameter that mediates between different clock domains. Rather than direct querying between domains, nodes use the drift rate (which represents the relative clock frequency difference) to calculate time offsets, reducing the need for direct network communication between clock domains.
2Measurement precision
If frequent network queries are used for time synchronization, then time accuracy is maintained, but latency increases
Solution Approach 1:
The system performs preliminary drift rate calculations and stores them for reuse. When time synchronization is needed, nodes use the pre-calculated drift rates locally rather than initiating new network queries, significantly reducing latency while maintaining time accuracy.
Solution Approach 2:
Nodes perform self-service time calculations using locally stored drift rate information. Instead of relying on external queries to other clock domains, each node can independently calculate time in other domains using its own clock time and the stored drift rate, eliminating query latency.
3Quantity of substance
If infrequent drift calculations are performed, then network traffic is reduced, but time accuracy may deteriorate
Solution Approach 1:
The system performs drift rate calculations periodically at predetermined intervals rather than continuously or on every time query. This periodic approach balances network traffic reduction with maintaining acceptable time accuracy, as the drift rate is updated regularly enough to capture clock frequency changes while avoiding excessive network usage.
Solution Approach 2:
The patent changes the parameter from frequent time queries to periodic drift rate updates. By updating the drift rate parameter less frequently than querying time, the system reduces network traffic while the drift rate value itself encodes time accuracy information that remains valid between updates.
Data Source
AI summary
A network includes a first plurality of nodes operating in a first clock domain based on a first clock source, a second plurality of nodes operating in a second clock domain based on a second clock source, and synchronization circuitry accessible to both of the clock domains without requiring network traffic between the clock domains. The synchronization circuitry is configured to periodically calculate a drift rate between the time of day in the respective clock domains. Each node in one of the clock domains is configured to, when sending a message to a node in the other of the clock domains, calculate a time of day in the other of the clock domains based on an actual time of day in the one of the clock domains and the drift rate, and to include, in the message to the node in the other clock domain, the calculated time of day.