IEEE Std C37.238-2011 pdf download – IEEE Standard Profile for Use of IEEE 1588™ Precision Time Protocol in Power System Applications.
profile: The set of allowed Precision Time Protocol (PTP) features applicable to a device. Precision Time Protocol (PTP) communication: Information used in the operation of the protocol, transmitted in a PTP message over a PTP communication path. Precision Time Protocol (PTP) communication path: The signaling path portion of a particular network enabling direct communication among ordinary and boundary clocks. Precision Time Protocol (PTP) message: One of the message types defined in IEEE Std 1588-2008. Precision Time Protocol (PTP) port: A logical access point of a clock for PTP communications to the communications network. preferred grandmaster clock: A grandmaster-capable device that is intended to be the best or backup grandmaster in the network. Typically a preferred grandmaster has an independent connection to a recognized standard time source. There should be at least two preferred grandmaster clocks in a system. recognized standard time source: A recognized standard time source is a source external to Precision Time Protocol (PTP) that provides time and/or frequency as appropriate that is traceable to the international standards laboratories maintaining clocks that form the basis for the International Atomic Time (TAI) and Universal Coordinated Time (UTC) timescales. Examples of these are Global Positioning System (GPS), NTP, and National Institute of Standards and Technology (NIST) timeservers. residence time: The time difference between ingress and egress time stamps for an IEEE C37.238 Sync message. slave-only clock: An ordinary clock that is not currently capable of Precision Time Protocol (PTP) Master state. stability: A measure of how the mean of the time or frequency error between the clock under test and a perfect reference clock varies with respect to variables such as time, temperature, etc. See: accuracy.
synchronized clocks: Two clocks are synchronized to a specified uncertainty if they have the same epoch, and their measurements of the time of a single event at an arbitrary time differ by no more than that uncertainty. syntonized clocks: Two clocks are syntonized if the duration of the second is the same on both, which means the time as measured by each advances at the same rate. They may or may not share the same epoch. timeout: A mechanism for terminating requested activity that, at least from the requester’s perspective, does not complete within the specified time. timescale: A linear measure of time from an epoch. TimeInaccuracy: A device’s estimate of current worst-case time error (its magnitude) between time that the device provides and traceable time.