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This shows you the differences between two versions of the page.

--- networking:ntp [2021/07/07 07:23] – bstafford
+++ networking:ntp [2021/09/23 10:23] (current) – removed bstafford
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-====== NTP ======
-  * There is a dedicated page for [[networking:ntp_pools|public NTP servers]].
-  * There is a dedicated page to [[infoblox:ntp|Infoblox NTP]].
-**DO NOT** use burst or iburst against public NTP servers unless they are announced they accept it (e.g. don't use it against *.ntp.org servers). More details [[networking:ntp#burst_and_iburst|here]].
-**DO NOT** configure your system to use leap-smearing NTP servers as well as non-leap-smearing NTP servers at the same time. e.g. do not combine Google NTP with Cloudflare NTP. See [[ntp_pools#leap_smearing|here]].
-NTP overview from an NTP [[https://www.eecis.udel.edu/~mills/ntp.html|author]] and there is a best practice guide [[https://tools.ietf.org/id/draft-ietf-ntp-bcp-13.html|here]].
-===== NTP Timezones =====
-  * [[https://www.iana.org/time-zones|IANA's page on timezones]]
-  * [[https://en.wikipedia.org/wiki/List_of_tz_database_time_zones|List of Timezones]]
-  * [[https://en.wikipedia.org/wiki/List_of_time_zone_abbreviations|List of Timezone Abbreviations]]
-===== Windows NTP =====
-**REMEMBER** It is important to note that W32Time will only actively synchronize with one time source at a time, even though you are able to list more than one time source. ([[https://docs.microsoft.com/en-gb/archive/blogs/w32time/configuring-the-time-service-ntpserver-and-specialpollinterval|source]])
-Most NTP implementations would poll all the servers to choose the best sample, but as of Server 2008, Windows doesn't.
-==== Test Windows NTP ====
-You can test NTP manually using Windows using the following command (where 192.168.1.1 is the IP of the NTP server).
-<code>w32tm /stripchart /dataonly /computer:192.168.1.1</code>
-==== Resync Windows NTP ====
-Resynchronize the clock
-<code>w32tm /resync</code>
-==== Show Windows NTP Timezone ====
-Show current timezone settings
-<code>w32tm /tz</code>
-==== Show Windows NTP External Servers ====
-List external NTP servers (peers)
-<code>w32tm /query /peers</code>
-or
-<code>w32tm /query /peers /verbose</code>
-==== Stop and Start Windows NTP ====
-<code>net stop w32time</code>
-<code>net start w32time</code>
-==== Manually set Windows NTP ====
-<code>w32tm /config /manualpeerlist:0.uk.pool.ntp.org,1.uk.pool.ntp.org,2.uk.pool.ntp.org,3.uk.pool.ntp.org,0x1 /syncfromflags:MANUAL /reliable:yes /update </code>
-===== Linux NTP =====
-==== Set Linux Time ====
-<code>sudo date -s "22 JUN 2020 13:11:30"</code>
-==== Check Status ====
-Check status of NTP on Ubuntu 16.04+
-<code>timedatectl status</code>
-If NTP is not on, try the following command
-<code>sudo timedatectl set-ntp on</code>
-===== Show NTP Status =====
-<code>ntpstat</code>
-<code>ntpq -pn</code>
-<code>ntpq -p</code>
--p prints peers and -n means it will print IP and not FQDN
-The * character is used to mark which peer you are currently synced to.
-===== Refid =====
-From [[https://www.meinbergglobal.com/english/info/ntp-refid.htm|here]].
-Reference ID (refid) is a 32-bit code identifying the particular server or reference clock.  The interpretation depends on the value in the stratum field.
-For packet stratum 0 (unspecified or invalid), this is a four-character ASCII [RFC1345] string, called the "kiss code", used for debugging and monitoring purposes.
-For stratum 1 (reference clock), this is a four-octet, left-justified, zero-padded ASCII string assigned to the reference clock.  The authoritative list of Reference Identifiers is [[https://www.iana.org/assignments/ntp-parameters/ntp-parameters.xhtml|maintained by IANA]]; however, any string beginning with the ASCII character "X" is reserved for unregistered experimentation and development.  The identifiers in the list below have been used as ASCII identifiers:
-^ ID ^ Clock Source ^
-| INIT | Initialising. NTP Server not yet reached. |
-| LOCL | The local system clock |
-| LCL | undisciplined local clock |
-| LOCL | Undisciplined local clock |
-| GOOG | means it is using one of Google's time clocks |
-| FB.. | means it is using Facebook time servers |
-| MRS | is a multi-reference clock |
-| SHM | means Shared Memory Driver |
-| ATOM | with ATOM PPS |
-| DCFa | DCF77 (with amplitude modulation) |
-| DCFp | DCF77 (with phase modulation/pseudo random phase modulation) |
-| GPSs | GPS (with shared memory access - Meinberg) |
-| GPSi | GPS (with interrupt based access - Meinberg) |
-| GLNs | GPS/GLONASS (with shared memory access - Meinberg) |
-| GLNi | GPS/GLONASS (with interrupt based access - Meinberg) |
-| GOES | Geosynchronous Orbit Environment Satellite |
-| GPS | Global Position System |
-| GAL | Galileo Positioning System |
-| PPS | Generic pulse-per-second |
-| IRIG | Inter-Range Instrumentation Group |
-| WWVB | LF Radio WWVB Ft. Collins, CO 60 kHz |
-| DCF | LF Radio DCF77 Mainflingen, DE 77.5 kHz |
-| HBG | LF Radio HBG Prangins, HB 75 kHz |
-| MSF | LF Radio MSF Anthorn, UK 60 kHz |
-| JJY | LF Radio JJY Fukushima, JP 40 kHz, Saga, JP 60 kHz |
-| LORC | MF Radio LORAN C station, 100 kHz |
-| TDF | MF Radio Allouis, FR 162 kHz |
-| CHU | HF Radio CHU Ottawa, Ontario |
-| WWV | HF Radio WWV Ft. Collins, CO |
-| WWVH | HF Radio WWVH Kauai, HI |
-| NIST | NIST telephone modem |
-| ACTS | NIST telephone modem |
-| USNO | USNO telephone modem |
-| PTB | European telephone modem |
-| MRS | Multi Reference Sources |
-===== Burst and iBurst =====
-Using the burst option against a public server is considered abuse. Do not use this option with public NTP servers. Use it only for applications within your own organization.
-Burst and iBurst are only relevant if the NTP Servers you are synchronising to actually support these features, if not they can be switched off.
-The 'burst' option is used to increase the average quality of time offset statistics. At every poll interval, when the NTP server responds, the system will send a burst of up to eight packets instead of the usual one packet. For use with the server command to improve the average quality of the time-offset calculations as well as accurately measure jitter with long poll intervals.
-The 'iburst' option is used to improve the time taken for initial synchronization. When the NTP server is unreachable, the NTP client sends a burst of eight packets instead of the usual one packet and then shorten the time until the first sync. The packet spacing is normally 2 seconds. The iburst mode continues to send frequent NTP queries until the server responds and time synchronization starts. After the first minute, the iburst mode typically synchronizes the clock so that queries need to be sent at intervals of 64 seconds or more.
-Microsoft only support Simple Network Time Protocol (sntp) which is compatible with NTP clients but does not offer all the functionality of NTP (including Burst and iBurst). Microsoft servers will just ignore the burst and iburst options.