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Clock synchronization is a topic in computer science and engineering that aims to coordinate otherwise independent clocks. Even when initially set accurately, real clocks will differ after some amount of time due to clock drift , caused by clocks counting time at slightly different rates.
These are high-precision timekeeping devices such as atomic clocks, GNSS (including GPS) or other radio clocks, or a PTP-synchronized clock. [29] They generate a very accurate pulse per second signal that triggers an interrupt and timestamp on a connected computer. Stratum 0 devices are also known as reference clocks.
Manual sync only. NIST Automated Computer Time Service (ACTS) [27] +1-303-494-4774 +1-808-335-4721; Windows computer with dialup modem. ntpd with NIST/USNO/PTB Modem Time Services driver; ClockWatch Pro for Windows [22] USNO Master Clock modem time [28] +1-202-762-1594 Computer with Bell 212A or CCITT V.22 compatible modem US Naval Observatory ...
The Precision Time Protocol (PTP) is a protocol for clock synchronization throughout a computer network with relatively high precision and therefore potentially high accuracy. . In a local area network (LAN), accuracy can be sub-microsecond – making it suitable for measurement and control systems.
In a two-way time transfer system, the two peers will both transmit and receive each other's messages, thus performing two one-way time transfers to determine the difference between the remote clock and the local clock. [4]: 118 The sum of these time differences is the round-trip delay between the two nodes. It is often assumed that this delay ...
Telecommunication networks rely on the use of highly accurate primary reference clocks which are distributed network-wide using synchronization links and synchronization supply units. Ideally, clocks in a telecommunications network are synchronous, controlled to run at identical rates, or at the same mean rate with a fixed relative phase ...
A GPS outage however is not initially an issue because clocks can go into holdover, [15] allowing the interference to be alleviated as much as the stability of the oscillator providing holdover will allow. [4] The more stable the oscillator, the longer the system can operate without GPS.
PPS signals are used for precise timekeeping and time measurement. One increasingly common use is in computer timekeeping, including NTP.Because GPS is considered a stratum-0 source, a common use for the PPS signal is to connect it to a PC using a low-latency, low-jitter wire connection and allow a program to synchronize to it.