PTP Clock Quality Testing via Reverse Sync Messages
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Solution Overview
Problem
Existing methods for testing recovered clock quality in networked systems, such as those using Precision Time Protocol (PTP), require separate physical interfaces and are limited by layer two network constraints, making them infeasible in applications like automobile electronic control units and unable to test boundary clocks effectively.
Innovation Solution
A system that uses the same or different physical network interface for both synchronization and testing, allowing a test device to operate as a PTP master and receive reverse synchronization messages from a slave device to quantify synchronization errors, enabling clock synchronization error measurement without a separate test interface and across multiple boundary clocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate physical interface is used for testing recovered clock quality, then testing capability is improved, but device complexity and production cost increase
Solution Approach 1:
The existing synchronization interface is made multi-functional by enabling it to perform both its original synchronization function and an additional testing function. The test device operates as a PTP master that can both synchronize slave clocks and test recovered clock quality through reverse synchronization messages, eliminating the need for separate test interfaces.
Solution Approach 2:
The testing function is merged with the existing synchronization interface rather than being implemented as a separate physical interface. The same network interface that receives synchronization messages is also used to send reverse synchronization messages for testing, combining two functions into one interface.
2Adaptability or versatility
If layer two messages are used for testing, then network compatibility is improved, but measurement capability deteriorates due to immutability constraints
Solution Approach 1:
Instead of having the test device send test messages to the slave, the approach is inverted: the slave device sends reverse synchronization messages back to the test device. This allows the slave to provide clock information that enables the test device to quantify synchronization errors, working around the immutability constraint of layer two messages.
Solution Approach 2:
Reverse synchronization messages act as an intermediary mechanism that enables testing without requiring mutable layer two messages. The slave device embeds clock information in these messages, allowing the test device to perform measurements while maintaining compatibility with the existing network protocol structure.
3Device complexity
If a single test system is connected to one boundary clock, then device simplicity is improved, but testing coverage deteriorates for remaining boundary clocks and slaves
Solution Approach 1:
The system implements feedback by having each boundary clock and slave device send reverse synchronization messages to the test device. This feedback mechanism allows the test device to receive clock information from multiple devices and evaluate the recovered clock quality of each device in the network, achieving comprehensive testing coverage.
Solution Approach 2:
Each boundary clock and slave device in the network performs self-service by autonomously sending reverse synchronization messages to the test device. This eliminates the need for the test system to actively query each device, as each device automatically provides its clock information for testing purposes.
Data Source
AI summary
A system for testing recovered clock quality includes a test device for operating as a timing synchronization protocol master for communicating with a device under test functioning as a timing synchronization protocol slave or a timing synchronization protocol boundary clock to synchronize a clock of the device under test with a clock of the test device. The system further includes a recovered clock quality tester for receiving, from the device under test, a reverse synchronization message including clock information and for using the clock information to quantify a synchronization error between the clock of the device under test and the clock of the test device.