There are two supported protocols in Red Hat Enterprise Linux for synchronization of computer clocks over a network. The older and more well-known protocol is the Network Time Protocol (NTP). In its fourth version, NTP is defined by IETF in RFC 5905. The newer protocol is the Precision Time Protocol (PTP), which is defined in the IEEE 1588-2008 standard.
The reference implementation of NTP is provided in the ntp package. Starting with Red Hat Enterprise Linux 7.0 (and now in Red Hat Enterprise Linux 6.8) a more versatile NTP implementation is also provided via the chrony package, which can usually synchronize the clock with better accuracy and has other advantages over the reference implementation. PTP is implemented in the linuxptp package.
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