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 implementations of the IEEE 1588 Precision Time Protocol (PTP) exist:

• PTPd:
  • Apparently, this is the original implentation
  • Apparently, it is still maintained
• PTPd2:
  • A new version meant to supersede the previous implementation
  • Apparently unmaintained
  • Available only in the EPEL repositories as ptpd package
    
• 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:

• Does the ptpd package provided by EPEL refer to the ptpd or to the ptpd2 project ? (the EPEL package is called "ptpd" while the included binary is called "ptpd2"...)
  
• Why does EPEL provide PTPd2 while RedHat suggests and already provides linuxptp on its own repositories ? Which are differences between PTPd2 and Linuxptp in terms of reliability and timing accuracy ?

Many thanks and best regards.