[CentOS-devel] Use of PTPd on CentOS 6
Claudio Scordino
claudio at evidence.eu.com
Mon Jan 18 09:22:21 UTC 2016
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) <https://en.wikipedia.org/wiki/Precision_Time_Protocol>
exist:
- PTPd <http://ptpd.sourceforge.net>:
- Apparently, this is the original implentation
- Apparently, it is still maintained <http://www.github.com/ptpd/ptpd>
- PTPd2 <http://ptpd2.sourceforge.net>:
- A new version meant to supersede the previous implementation
- Apparently unmaintained
- For CentOS 6, available only in the EPEL repositories
- PTPv2d <http://code.google.com/p/ptpv2d>:
- A further implementation
- Unmaintained as well
- linuxptp <http://linuxptp.sourceforge.net>:
- A specific implementation for Linux
- Maintained
- Available on the CentOS repositories
- Suggested by the RedHat documentation for both RedHat 6
<https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Deployment_Guide/ch-Configuring_PTP_Using_ptp4l.html>
and RedHat 7
<https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/System_Administrators_Guide/sec-Using_PTP.html>
My questions follow:
- Why does the RedHat documentation suggest the use of linuxptp
<https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Deployment_Guide/s1-Installing_PTP.html>
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
<http://linuxptp.sourceforge.net/> ?
- 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 ?
Many thanks for any hint.
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