To measure and adjust offsets using 1PPS:
sfptpdshould be running between master and slave servers, and should be synchronized before the 1PPS value is measured and applied.
- The master 1PPS output should be connected to a single slave 1PPS input.
- On the slave server, for a short period such as 5 minutes, observe the 1PPS mean offset value from the pps_off_mean file to identify the mean offset value. Refer to 1PPS Statistical Data for instructions on reading the 1PPS statistical data files.
- On all slaves on the same network segment, configure
sfptpdwith knowledge of the mean 1PPS offset.
- If the initial observed 1PPS offset is a negative value, then all subsequent offsets should be added as positive values to the ptp_rx_latency option. The ptp_tx_latency option in this case should be zero.
- If the initial observed 1PPS offset is a positive value, then all subsequent offsets should be added as positive values to the ptp_tx_latency option. The ptp_rx_latency option in this case should be zero.
- Continue to observe the 1PPS compensated mean offsets.
- Repeat steps 3-5 adding or subtracting the 1PPS mean offset (doubled) value each time to the last applied value until the observed 1PPS mean value is as close to zero as possible.