PTP Clock Source Recovery Logic for Faster Sync Restoration
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Solution Overview
Problem
Existing PTP clock source selection methods fail to function effectively in certain scenarios, leading to instability and prolonged recovery times in network synchronization, particularly during local changes or restarts of network devices.
Innovation Solution
A method and network device that determine the state of PTP clock source reception after local changes, allowing immediate use as a candidate master without waiting for a predetermined restoration time, using a state machine or timestamp-based offset analysis to assess stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the network device waits for the predetermined restoration time before using the PTP clock source as a candidate master, then the stability of the PTP clock source is improved, but the recovery time of the PTP clock synchronization is prolonged
Solution Approach 1:
The patent applies dynamics by making the waiting time adaptive rather than fixed. The network device dynamically adjusts whether to wait for the predetermined restoration time based on the determined cause of reception interruption. When the cause is a local change, the device skips the waiting period and immediately uses the PTP clock source. When the cause is external, the device waits for the full restoration time. This dynamic adjustment resolves the contradiction by optimizing recovery speed without compromising stability in scenarios where it matters.
Solution Approach 2:
The patent changes the parameter of waiting time based on the state of the network device. By determining whether the reception interruption is caused by local change or external factors, the system adjusts the effective waiting time parameter: either 0 (immediate use) or the full predetermined restoration time. This parameter change allows the system to achieve fast recovery when safe to do so while maintaining stability when necessary.
2Loss of time
If the network device immediately uses the PTP clock source as a candidate master after reception recovery, then the recovery time is reduced, but the stability of PTP clock synchronization deteriorates
Solution Approach 1:
The patent applies local quality by applying different stability assurance measures to different scenarios. Instead of uniformly waiting for the full restoration time in all cases, the system applies the waiting period only when the interruption was caused by external factors. When the interruption was caused by local change, the system immediately resumes using the PTP clock source without the waiting period. This localized application of stability measures resolves the contradiction by maintaining stability only where external disruptions require it.
Solution Approach 2:
The system dynamically adjusts the stability assurance mechanism based on the determined cause of interruption. The decision logic dynamically selects between two approaches: immediate resumption (when locally caused) or delayed resumption with full waiting period (when externally caused). This dynamic behavior allows the system to achieve fast recovery when safe while maintaining stability when necessary.
3Device complexity
If the existing PTP clock source selection method is used, then the device complexity is low, but the robustness of PTP clock synchronization deteriorates in certain scenarios
Solution Approach 1:
The patent applies preliminary action by determining the cause of reception interruption before making the clock source selection decision. The system performs the state determination and cause analysis in advance, before selecting whether to wait for restoration time or immediately use the PTP clock source. This preliminary assessment enables the system to handle various scenarios robustly without adding significant complexity to the selection process.
Solution Approach 2:
The system incorporates feedback by determining the state of the network device and the cause of reception interruption based on information from the PTP protocol interaction and local state monitoring. This feedback mechanism allows the system to adapt its behavior to the actual situation, improving robustness without requiring complex external control systems.
Data Source
AI summary
A method and a network device are disclosed for precision time protocol (PTP) clock synchronization. According to an embodiment, the network device determines whether the network device is in one of a first state where a reception of an announce message from a PTP clock source is interrupted due to a local change at the network device, and a second state where the PTP clock source is restored after a predetermined restoration time, or the reception of the announce message from the PTP clock source is recovered after the local change. When determining that the network device is in one of the first state and the second state, the network device uses the PTP clock source as a candidate PTP master, without waiting for the predetermined restoration time.