This document describes results in timing synchronization performance on a setup with two ptp slaves and a ptp master. Data were collected from the ptp4l slave algorithm internal metrics and log files and therefore graphed.
For this measurement campaign two different slaves were used. The main difference between them is the availability of hardware timestamping on the ethernet phy:
- RaspberryPi3 (software only timestamp)
- Variscite imx7-var-som board (hardware timestamp enabled)
The graphs below represent, on a per second base, the following informations:
- The master offset value tracks the measured offset from the master (in nanoseconds).
- States of the clock servo: s0 is unlocked, s1 is clock step, and s2 is locked.
- The freq value represents the frequency adjustment of the clock (in parts per billion, ppb).
- The path delay value represents the estimated delay of the synchronization messages sent from the master (in nanoseconds).
The below pictures show the graph of the output data of ptp4l of 15 hours run.
Calculated offsets:
rms | min | max |
---|---|---|
21.5us | -448us | 797us |
Calculated offsets:
rms | min | max |
---|---|---|
16.5us | -99us | 84us |
Calculated offsets:
rms | min | max |
---|---|---|
12.3us | -790us | 790us |
Calculated offsets:
rms | min | max |
---|---|---|
3.2us | -34us | 43us |