Synchronization Model

Enhanced PTP User Guide (UG1602)

Document ID
UG1602
Release Date
2022-10-18
Revision
1.0 English

sfptpd synchronizes local clocks, including the system clock, to a single time source:

  • sfptpd can process multiple time sources including:
    • one or more remote PTP master clocks
    • a 1PPS signal, with an external NTP server providing time of day
    • an external NTP server
    • the clock in a supported local network adapter.

    Each time source is provided by an instance of a sync module. For more information, see Sync Modules.

  • sfptpd selects a time source to use.

    By default, sfptpd automatically selects the best performing time source. For more details, see Sync Module Selection.

  • sfptpd synchronizes a Local Reference Clock (LRC) to the selected time source.

    sfptpd designates one local clock as the Local Reference Clock (LRC), and synchronizes this to the selected external time source.

    The LRC used will depend on the sync module selected as the time source, but the LRC is typically the precision clock on a supported PTP adapter. See the descriptions of sync modules in Sync Modules.

  • sfptpd synchronizes each clock, including the system clock, to the LRC.

    sfptpd runs a clock servo for each additional clock in a server (i.e. for each additional timestamping adapter and for the system clock). sfptpd will measure the difference between each clock and the LRC, and synchronize all clocks to the LRC.

The following figure illustrates the synchronization options supported by sfptpd.

Figure 1. sfptpd Synchronization Model