PTP State Transitions

This section outlines various PTP state event notification transitions for single WPC and Dual WPC NICs with and without secondary source.

Single and Dual WPC with a Secondary Source

Scenario	Sync state	GNSS state	ptp Lock state	ptp clock class	OS clock state	Notes
Initial State	LOCKED	SYNCHRONIZED	LOCKED	6	LOCKED	The ptp4l, phc2sys , ts2phc processes are auto-restarted when they are stopped, so the processes move from interim states to final states upon auto-restart.
PTP4l stop/kill (process gets auto restarted)	HOLDOVER -> LOCKED	SYNCHRONIZED	HOLDOVER -> LOCKED	6	HOLDOVER ->LOCKED	sync state: The interim state is HOLDOVER. The final state upon ptp4l auto restart is LOCKED. Ptp lock state: The interim state is HOLDOVER, and the final state is LOCKED. OS clock state: The interim state is HOLDOVER, and the final state is LOCKED.
ts2phc stop/kill	LOCKED	ANTENNA-DISCONNECTED -> SYNCHRONIZED	LOCKED	6	LOCKED	For GNSS, the interim state is ANTENNA-DISCONNECTED, and the final state is SYNCHRONIZED upon the ts2phc process restart.
phc2sys stop/kill	HOLDOVER ->LOCKED	SYNCHRONIZED	FREERUN ->LOCKED	6	HOLDOVER ->LOCKED	sync state: The interim state is HOLDOVER, and the final state is LOCKED upon ptp4l auto restart. Ptp lock state: The interim state is FREERUN, and the final state is LOCKED. OS clock state: The interim state is HOLDOVER, and the final state is LOCKED.
GNSS cable disconnect	HOLDOVER	ANTENNA-DISCONNECTED	HOLDOVER	7	LOCKED
GNSS cable disconnect and Holdover period expired	FREERUN -> LOCKED	FAILURE-NOFIX	FREERUN->LOCKED	6	LOCKED	At the end of GNSS, the Holdover period expires and GNSS transitions from ANTENNA-DISCONNECTED to FAILURE-NOFIX. Because of the PTP secondary source, the sync state transitions from FREERUN to LOCKED, the PTP state transitions from FREERUN to LOCKED, and DU sync to the secondary source.
GNSS cable restore	HOLDOVER -> LOCKED	SYNCHRONIZED	HOLDOVER -> LOCKED	6	LOCKED	DU sync to the GNSS signal
Timing pod restart	FREERUN -> LOCKED	SYNCHRONIZED	FREERUN->LOCKED	6	LOCKED	sync state: The interim state is FREERUN, and the final state is LOCKED. Ptp lock state: The interim state is FREERUN, and the final state is LOCKED.

Table 1. Single WPC with no secondary source

Scenario	Sync state	GNSS state	ptp Lock state	ptp clock class	OS clock state	Notes
Initial State	LOCKED	SYNCHRONIZED	LOCKED	6	LOCKED	The ptp4l, phc2sys, and ts2phc processes get auto-restarted when they are stopped, so the processes move from the interim states to the final states upon auto-restart.
PTP4l stop/kill (process gets auto restarted)	HOLDOVER -->LOCKED	SYNCHRONIZED	HOLDOVER -> LOCKED	6	HOLDOVER ->LOCKED	sync state: The Interim state is HOLDOVER, and the final state is LOCKED upon ptp4l auto restart. Ptp lock state: The interim state is HOLDOVER, and the final state is LOCKED. OS clock state: The interim state is HOLDOVER, and the final state is LOCKED.
ts2phc stop/kill	LOCKED	ANTENNA-DISCONNECTED -> SYNCHRONIZED	LOCKED	6	LOCKED	For GNSS, the interim state is ANTENNA-DISCONNECTED, and the final state is SYNCHRONIZED upon ts2phc process restart.
phc2sys stop/kill	HOLDOVER->LOCKED	SYNCHRONIZED	FREERUN ->LOCKED	6	HOLDOVER ->LOCKED	sync state: The Interim state is HOLDOVER, and the final state is LOCKED upon ptp4l auto restart. Ptp lock state: The interim state is FREERUN, and the final state is LOCKED. OS clock state: The interim state is HOLDOVER, and the final state is LOCKED.
GNSS cable disconnect	HOLDOVER	ANTENNA-DISCONNECTED	HOLDOVER	7	LOCKED
GNSS cable disconnect and Holdover period expired	FREERUN	FAILURE-NOFIX	FREERUN	248	LOCKED	At the end of GNSS, the Holdover period expires and GNSS transitions from ANTENNA-DISCONNECTED to FAILURE-NOFIX.
GNSS cable restore	FREERUN->LOCKED	FAILURE-NOFIX->SYNCHRONIZED	FREERUN -> LOCKED	248->6	LOCKED	DU sync to the GNSS signal
Timing pod restart	FREERUN->LOCKED	SYNCHRONIZED	FREERUN->LOCKED	6	LOCKED	sync state: The Interim state is FREERUN, and the final state is LOCKED. Ptp lock state: The interim state is FREERUN, and the final state is LOCKED.