Timing Protocols

The Precision Time Protocol (PTP) provides a greater degree of clock accuracy for networked devices, allowing clocks to be synchronized locally in increments of less than a microsecond. PTP uses a master-slave hierarchy similar to that used by NTP. The most precise clock available is referred to as the master clock, and slave devices use the signal from the master to synchronize their own clocks.

The master clock sends out a sync message (referred to as an announce message in IEEE 1588-2008) at a regular interval. The slave clock responds with a time-stamped delay request message in order to measure and compensate for packet delays between the devices. The slave then receives a message from the master specifying when the delay message was received, which allows the slave to calculate final values for clock synchronization. Synchronization is maintained by the regular exchange of PTP packets between master and slave.

Note: Arista switches do not support setting of the system clock using PTP. System clock synchronization is best supported by the NTP service on the PTP grandmaster.
PTP is disabled globally by default. The following steps are required to enable PTP on an interface: