PTPd was the original implementation. It had no support for real hardware
timestamps. Some device drivers supplied “SW synchronized” hardware stamps that
were fudged to be in the kernel clock time domain. This was driver specific and
was not well documented or supported. Richard Cochran started trying to create
and expose the kernel interface we used today, and the PTPd project wasn’t
interested.
He wrote linuxptp at this time, and got the current hardware timestamp
implementation upstream. It is possible at some point PTPd started implementing
use of the PHC subsystem since then, I am not aware.
PTPd2 was started sometime after PTPd and was intended to support v2 of the
protocol, which at the time PTPd did not support (I have no idea if it does
now). I don’t think this version was maintained for very long. It also did not
support hardware timestamping.
As Ledda mentioned, RedHat backported the interface into their RHEL6.4 kernel,
which has allowed them to enable support LinuxPTP.
For Linux, I don’t think any other PTP daemon is as capable as LinuxPTP, though
I could be mistaken as I have since stopped researching the alternatives.
If you have configured ptp4l and phc2sys correctly, they should synchronize
fairly quickly. You’d have to show the configuration and output of these two
commands for us to further help you.
Regards,
Jake
From: Claudio Scordino [mailto:clau...@evidence.eu.com]
Sent: Monday, January 18, 2016 1:22 AM
To: linuxptp-devel@lists.sourceforge.net
Subject: [Linuxptp-devel] Use of PTP on CentOS 6
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 ?
* Why when I run ptp4l and phc2sys, the machines do not synchronize
immediately and often need me to start/stop the services several times or
manually change system time through date to make the machine synchronize ?
Many thanks and best regards.
------------------------------------------------------------------------------
Site24x7 APM Insight: Get Deep Visibility into Application Performance
APM + Mobile APM + RUM: Monitor 3 App instances at just $35/Month
Monitor end-to-end web transactions and take corrective actions now
Troubleshoot faster and improve end-user experience. Signup Now!
http://pubads.g.doubleclick.net/gampad/clk?id=267308311&iu=/4140
_______________________________________________
Linuxptp-devel mailing list
Linuxptp-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/linuxptp-devel
