sfptpd will failover from PTP to NTP if there are active PTP alarms:
See PTP Alarms for a description of alarms.
If alarm conditions clear,
sfptpd will resume synchronization using PTP.
The selection_holdoff_interval (seconds) can be set to prevent immediate failover caused when only one or two PTP packets are not received.
sfptpd will NOT failover to NTP because of synchronization accuracy.