NTP keeps precision time by applying small adjustments to to system clock periodically (See also Q: 5.1.6.1.). However, some clock implementations do not allow small corrections to be applied to the system clock, and there is no standard interface to monitor the system clock's quality.

Therefore a new clock model is suggested that has the following features (See also [RFC 1589]):

Two new system calls to query and control the clock: ntp_gettime() and ntp_adjtime()

The clock keeps time with a precision of one microsecond.[1] In real life operating systems there are clocks that are much worse.

Time can be corrected in quantities of one microsecond, and repetitive corrections accumulate.[1] The UNIX system call adjtime() does not accumulate successive corrections.

The clock model maintains additional parameters that can be queried or controlled. Among these are:

A clock synchronization status that shows the state of the clock machinery (e.g. TIME_OK).Several clock control and status bits that control and show the state of the machinery (e.g. STA_PLL). This includes automatic h

here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss ntp offset value the workings and policies of this site About Us Learn more

Ntp Offset Is Over Critical Threshold

about Stack Overflow the company Business Learn more about hiring developers or posting ads with us Stack Overflow ntp dispersion Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 6.2 million programmers, just like you, helping http://www.ntp.org/ntpfaq/NTP-s-algo-kernel.htm each other. Join them; it only takes a minute: Sign up NTP offset error from real time up vote 1 down vote favorite I'm working on a project where I need to find out the maximum offset an NTP synchronized clock can be from UTC. If I run ntpdc -c loopinfo it outputs an offset, is this the http://stackoverflow.com/questions/21732056/ntp-offset-error-from-real-time offset error from actual time? also if I run ntpq -p it will show offset for each of the peers what is this offset? which of these can I use to find the maximum offset error from real time? Thank you. synchronization offset ntp share|improve this question asked Feb 12 '14 at 15:23 user3302253 62 add a comment| 2 Answers 2 active oldest votes up vote 1 down vote I think you are looking for the output of ntpq -c kerninfo or ntptime $ ntpq -c kerninfo associd=0 status=0615 leap_none, sync_ntp, 1 event, clock_sync, pll offset: 0.336481 pll frequency: -32.762 maximum error: 0.136773 estimated error: 0.000231 kernel status: pll nano pll time constant: 10 precision: 1e-06 frequency tolerance: 500 pps frequency: 0 pps stability: 0 pps jitter: 0.000 calibration interval 4 calibration cycles: 0 jitter exceeded: 0 stability exceeded: 0 calibration errors: 0 Or use ntptime: S ntptime ntp_gettime() returns code 0 (OK) time d6a66a56.372c300c Wed, Feb 12 2014 16:47:02.215, (.215518749), maximum error 141773 us, estimated error 231 us, TAI offset

Start here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies of this site About Us Learn more about Stack Overflow the company Business Learn http://serverfault.com/questions/427339/why-should-i-care-about-ntp-kernel-statistics more about hiring developers or posting ads with us Server Fault Questions Tags Users Badges Unanswered Ask Question _ Server Fault is a question and answer site for system and network administrators. Join them; it only takes a http://www.akadia.com/services/ntp_synchronize.html minute: Sign up Here's how it works: Anybody can ask a question Anybody can answer The best answers are voted up and rise to the top Why should I care about NTP Kernel statistics? up vote 7 down vote ntp offset favorite I'ved noticed that munin graphs a few bits of information about timing/kernel statistics that I've never quite understood. Most of my servers seem to stay close to 0, which I presume is good, but one of them is slowly but steadily getting more and more negative on one of the graphs. Munin graphs the following statistics over time: NTP kernel PLL estimated error (secs) NTP kernel PLL frequency (ppm + 0) NTP kernel PLL offset (secs) ntp estimated error NTP timing statistics for system peer Here's an example from munin's docs: http://demo.munin-monitoring.org/time-year.html Searching around the web for a concise, understandable definition of NTP turns up nothing (except for a bunch of Nagios and Munin graphs), and searching Server Fault turns up a ton of answers that presume the reader knows something about NTP already. Stack Overflow defines it thusly: NTP stands for Network Time Protocol, and it is an Internet protocol used to synchronize the clocks of computers to some time reference. But that seems a little obtuse—does this affect, say, a web server, encryption, or database synchronization? What is NTP, and why should I care? Are there any stats in particular I should make sure don't get out of control? monitoring ntp share|improve this question asked Sep 14 '12 at 3:58 geerlingguy 98211121 1 Which one is steadily decreasing? If PLL frequency, it's just the crystal aging (or temperature changes). –David Schwartz Sep 14 '12 at 4:05 That's the one. It used to go + and - a lot, now it is just really slowly going into the negative territory. Currently at '-20.0'. –geerlingguy Sep 14 '12 at 17:55 add a comment| 1 Answer 1 active oldest votes up vote 3 down vote accepted NTP is a protocol that synchronizes the system clock (usually there is a daemon running on *nix boxes). In shor

NTP is organised in a hierarchical client-server model. In the top of this hierarchy there are a small number of machines known as reference clocks. A reference clock is known as stratum 0 and is typically a cesium clock or a Global Positioning System (GPS) that receives time from satellites. Attached to these machines there are the so-called stratum 1 servers (that is, stratum 0 clients), which are the top level time servers available to the Internet, that is, they are the best NTP servers available. Note: in the NTP lingo measure for synchronization distance is termed as stratum: the number of steps that a system lies from a primary time source. Following this hierarchy, the next level in the structure are the stratum 2 servers which in turn are the clients for stratum 1 servers. The lowest level of the hierarchy is made up by stratum 16 servers. Generally speaking, every server syncronized with a stratum n server is termed as being at stratum n+1 level. So, there are a few stratum 1 servers which are referenced by stratum 2 servers, wich in turn are refenced by stratum 3 servers, which are referenced by stratum 4 and so on. NTP servers operating in the same stratum may be associated with others in a peer to peer basis, so they may decide who has the higher quality of time and then can synchronise to the most accurate. In addition to the client-server model and the peer to peer model, a server may broadcast time to a broadcast or multicast IP addresses and clients may be configured to synchronise to these broadcast time signals. So, at this point we know that NTP clients can operate with NTP servers in three ways: in a client-server basis in a peer to peer mode sending the time using broadcast/multicast How does it work Whenever ntpd starts it checks its configuration file (/etc/ntp.conf) to determine syncronization sources, authentication options, monitoring options, access control and other operating options. It also checks the frequency file (/etc/ntp/drift) that contains the latest estimate of clock frequency error. If specified, it will also look for a file containing the authentication keys (/etc/ntp/keys). Note that the path and/or name of these configuration files may vary in your system. Check the -c command line option. Once the NTP daemon is up and running, it will operate by exchanging packets (time and sanity check exchanges) with its configured servers at poll intervals and its behaviour will depend on the delay between the local time and

© Copyright 2019|winbytes.org.