Network Probe Time Synchronization via Passive PTP Eavesdropping
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Solution Overview
Problem
Existing network monitoring and testing equipment face challenges in synchronizing free-running clocks with a remote master clock, particularly in distributed communication networks, where precise time correlation of network packets is necessary for accurate network testing and analysis.
Innovation Solution
A method for correlating the time of a free-running clock in a network probe to a network-connected master clock involves the probe participating in an exchange of timing messages, recording specific message transmission and reception times, and transmitting these values to a remote test server for computing a probe time offset, allowing for synchronization of probe timestamps with the master clock without active clock synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If active clock synchronization is performed by the probe, then time correlation accuracy is improved, but device complexity and operational overhead increase
Solution Approach 1:
The patent introduces a remote test server as an intermediary that performs the time correlation calculation. Instead of the probe actively synchronizing its clock, the probe passively records timestamps and transfers them to the server, which then computes the time offset and corrected timestamps. This mediator approach reduces probe complexity while maintaining measurement precision.
Solution Approach 2:
The probe creates a copy of the timing information by recording local timestamps and transferring them to the remote server. The server then creates a corrected version of the timestamps by applying the calculated time offset. This copying approach allows the probe to remain simple while achieving accurate time correlation through the server's processing.
2Measurement precision
If the probe actively synchronizes its clock with the master clock, then time synchronization accuracy is improved, but network traffic and operational complexity increase
Solution Approach 1:
The patent extracts the time synchronization calculation from the probe and relocates it to the remote test server. The probe only performs simple timestamp recording and data transfer, while the server performs the complex time offset calculation. This extraction reduces the network traffic required for synchronization while maintaining accuracy.
Solution Approach 2:
Instead of continuously exchanging synchronization messages, the probe copies timing information (timestamps) to the server periodically. The server then processes this copied data to compute time offsets and generate corrected timestamps, reducing the frequency and volume of network traffic compared to active continuous synchronization.
3Device complexity
If the probe uses a free-running clock, then device simplicity is maintained, but time correlation with master clock deteriorates
Solution Approach 1:
The remote test server acts as a mediator that bridges the free-running probe clock and the master clock. The server receives timestamps from the probe's free-running clock, calculates the time offset by comparing with master clock information, and provides corrected timestamps. This allows the probe to maintain simplicity while achieving accurate time correlation through the server's mediation.
Solution Approach 2:
The probe copies its free-running clock timestamps to the server, which then creates a corrected version of these timestamps by applying the calculated time offset. This copying approach allows the probe to use a simple free-running clock while the server generates accurate time-correlated timestamps, maintaining both simplicity and precision.
Data Source
AI summary
The invention relates to time synchronization between network testing elements in distributed network monitoring and testing systems, and provides a method for synchronizing packet timestamps generated by a network probe with a free running clock to a master clock connected at a different location of the network. In one implementation, the probe eavesdrops on a PTP message exchange between the master and a remote slave device, recording message reception times according to it free running clock and transmitting relevant timing information to a rest server for determining the probe clock offset and updating the probe packet timestamps.