Clock Synchronization via Midpoint Rate Ratio in gPTP Networks
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Solution Overview
Problem
In multi-node networks, accurately measuring propagation delay (Pdelay) is challenging due to broadcast communication, leading to incorrect neighbor rate ratio calculations and clock synchronization issues in the generalized Precision Time Protocol (gPTP).
Innovation Solution
A method and system that utilize three synchronization/follow-up message pairs to directly measure the neighbor rate ratio between a primary and non-primary clock, setting a midpoint value for non-primary clock control and adjusting the phase of the primary clock, thereby synchronizing the non-primary clock with the primary clock without relying on Pdelay measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Pdelay measurements are performed in a multi-node broadcast network, then clock synchronization is attempted, but the propagation delay measurement becomes inaccurate due to multiple devices receiving and processing messages
Solution Approach 1:
The patent segments the clock synchronization process into distinct phases: a first phase using Pdelay measurements for initial synchronization, and a second phase using a calculated addend value for refined synchronization. This segmentation allows the system to benefit from both approaches while mitigating their individual weaknesses in broadcast networks
Solution Approach 2:
The patent introduces an intermediary calculated addend value that acts as a correction term between the Pdelay measurement and the final synchronization adjustment. This addend compensates for the inaccuracies introduced by broadcast message processing, serving as a mediator that reconciles the rough initial measurement with the need for precise synchronization
2Reliability
If Pdelay measurements are used to calculate neighbor rate ratio in multi-node networks, then clock synchronization is performed, but incorrect Pdelay values lead to incorrect neighbor rate ratio calculations
Solution Approach 1:
The patent implements a feedback mechanism where the system continuously monitors synchronization performance and dynamically adjusts the addend value based on observed timing discrepancies. This feedback loop ensures that even if initial Pdelay measurements are inaccurate, the system can converge to accurate synchronization by learning from actual performance data
Solution Approach 2:
The patent changes the synchronization parameter from relying solely on Pdelay measurements to using a composite parameter that includes the calculated addend value. This parameter transformation allows the system to maintain reliability while improving the precision of neighbor rate ratio calculations by incorporating correction factors
3Reliability
If standard gPTP synchronization is used in bandwidth-constrained networks like 10Base-TL, then clock synchronization is achieved, but the exchange of multiple message pairs consumes excessive bandwidth
Solution Approach 1:
The patent applies partial action by using only one or two message pairs for synchronization instead of the full sequence required by standard gPTP. The calculated addend value compensates for the reduced message exchange, allowing the system to achieve adequate synchronization with less bandwidth consumption, which is critical for constrained networks like 10Base-TL
Data Source
AI summary
A method is provided for synchronizing a non-primary clock to a primary clock in a network. The aspects include receiving a first, a second, and a third message pair, each including a sync message with an estimated time the sync message was transmitted and a follow-up message with an actual time the sync message was transmitted. The aspects include, responsive to the second message pair, setting a neighbor rate ratio between the primary clock and the non-primary clock to a midpoint value for non-primary clock control based on an ingress timestamp delta and an egress timestamp delta. The aspects include, responsive to the third message pair, fixing a phase value of the primary clock by setting an expected primary clock time value to a current timestamp of the primary clock without modification of the midpoint value. The aspects include adjusting the non-primary clock responsive to at least the midpoint value.