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linuxtimestampredhatcentos6ptpd

Use of PTPd on RedHat/CentOS

I need to create a reliable and accurate synchronization between two CentOS 6 machines connected through a direct Ethernet connection.

I've seen that on Linux several implementation of the IEEE 1588 Precision Time Protocol (PTP) exist:

  • PTPd:
    • Apparently, this is the original implentation
    • Source code available on GitHub (appparently, still maintained almost unmaintained)
  • PTPd2:
    • A new version meant to supersede the previous implementation
    • Apparently unmaintained
    • For CentOS 6, available only in the EPEL repositories
  • PTPv2d:
    • A further implementation
    • Unmaintained as well
  • linuxptp:
    • A specific implementation for Linux
    • Maintained
    • Available on the CentOS repositories
    • Suggested by the RedHat documentation for both RedHat 6 and RedHat 7

My questions follow:

  • Why does the RedHat documentation suggest the use of linuxptp for RedHat 6 (based on Linux kernel 2.6) despite the linuxptp documentation says that a Linux kernel version 3.0 or newer is needed ?
  • Which are differences between PTPd2 and Linuxptp in terms of reliability and timing accuracy ?
  • Which one should I prefer on CentOS 6 and on CentOS 7, respectively ?
  • Why either PTPd2 and Linuxptp do not synchronize immediately and often need me to start/stop the service several times or manually change system time through date to make the machine synchronize ?
Solution

  • Linuxptp works on RH6 thanks to RedHat backporting PTP support, as explained here. Indeed, it is the only choice, as the other packages have not been maintained.