Network Path Symmetry for Time Synchronization
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Solution Overview
Problem
Network path asymmetry in time synchronization protocols like PTP can lead to inaccurate delay calculations and time offset calculations, causing synchronization issues between clocks in distributed electronic systems.
Innovation Solution
Building forwarding information at network devices to ensure that timing messages follow the same network path in both directions between a clock source and a clock sink, achieving path symmetry and preventing message loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple network paths are used for data communications between electronic devices, then network path redundancy and load distribution are improved, but network path asymmetry occurs causing inaccurate time offset calculations
Solution Approach 1:
The patent segments the time synchronization process into distinct phases: forward path establishment (using join messages) and backward path usage (for timing messages). This segmentation allows the system to maintain multiple network paths for redundancy while ensuring that timing-critical messages traverse a consistent, symmetric path, thus resolving the contradiction between path redundancy and measurement precision.
Solution Approach 2:
The patent performs preliminary actions by establishing forwarding information and path symmetry before timing messages are exchanged. The join messages are sent in advance to configure the network paths, ensuring that when timing messages are later transmitted, they follow the predetermined symmetric path. This preliminary configuration prevents path asymmetry from affecting time offset calculations while maintaining overall network redundancy.
2Device complexity
If forwarding information is not built in intermediate network devices, then device complexity is reduced, but timing messages are lost and time synchronization fails
Solution Approach 1:
The patent implements self-service by enabling intermediate network devices to automatically build and maintain their own forwarding information through the join message mechanism. When a join message is received, the intermediate device autonomously creates the necessary forwarding entries without requiring manual configuration or complex centralized management. This self-service approach maintains reliable timing message delivery while minimizing the operational complexity of forwarding information management.
3Productivity
If ECMP routing is used for load distribution, then network throughput is improved, but path asymmetry causes inaccurate delay calculations
Solution Approach 1:
The patent applies local quality by differentiating the treatment of different message types within the network. Data traffic can utilize ECMP routing for load distribution and high throughput, while timing messages are assigned a special quality attribute that routes them through the symmetric path established by join messages. This local differentiation allows the network to simultaneously achieve high productivity for data traffic and high measurement precision for synchronization traffic.
Data Source
AI summary
In some examples, a first network device including a first time clock sends, over a first network path, a first timing message of a time synchronization process to synchronize the first time clock and a second time clock that is connected to a second network device. The first network device receives an indication associated with a second timing message of the time synchronization process, where the second timing message is to be sent from the second time clock. Based on receiving the indication, the first network device sends a first join message to a first intermediate network device that is part of the first network path, and a second join message to a second intermediate network device that is part of a second network path different from the first network path. The first network device receives, over the first network path, the second timing message sent by the second time clock, the second timing message communicated over the first network path based on the forwarding information built in the first intermediate network device and the second network device.