Loss of PTP Link Network Connection

Enhanced PTP User Guide (UG1602)

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1.1 English

If the network connection to the external master clock is lost at any point, an alarm is triggered in the corresponding PTP sync module. It can no longer be selected as the time source, unless all other sync modules are in the alarm state (for example at startup):

  • If other sync modules are instantiated and functioning correctly, sfptpd will select one of them as the time source.
  • If no other sync module is available, sfptpd continues to discipline all clocks in the system including the system clock.

    sfptpd maintains a clock frequency correction file for each clock in a server:

    • If the LRC is a supported PTP adapter, sfptpd will continue to discipline the LRC using the LRC frequency correction file. sfptpd will ensure that other clocks, hardware or system, will continue to synchronize to the LRC.
    • When there is no supported PTP adapter in the server, or if the LRC is the system clock, sfptpd will continue to discipline the system clock using the system clock frequency correction file.

Following restoration of the network link, the PTP sync modules receives PTP packets and the alarm is no longer triggered. It is eligible for selection as a time source, and sfptpd will resume normal discipline procedure.