Differences

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

--- networking:ntp [2021/03/09 21:58] – [NTP Servers] bstafford
+++ networking:ntp [2021/09/23 10:23] (current) – removed bstafford
@@ Line 1: / Line 1: @@
-====== NTP ======
-It is best to use **pool.ntp.org** as an NTP server. This will find the closest available servers for you.
-Also
-  * pool.ntp.org
-  * 0.pool.ntp.org
-  * 1.pool.ntp.org
-  * 2.pool.ntp.org
-  * 3.pool.ntp.org
-More specific are:
-  * ntp0.ja.net (Stratum 1)
-  * ntp1.npl.co.uk (Stratum 2)
-  * time.cloudflare.com (Stratum 3)
-  * uk.pool.ntp.org
-  * 0.uk.pool.ntp.org
-  * 1.uk.pool.ntp.org
-  * 2.uk.pool.ntp.org
-  * 3.uk.pool.ntp.org
-  * europe.pool.ntp.org
-  * 0.europe.pool.ntp.org
-  * 1.europe.pool.ntp.org
-  * 2.europe.pool.ntp.org
-  * 3.europe.pool.ntp.org
-The 0, 1, 2 and 3.pool.ntp.org names point to a random set of servers that will change every hour.
-===== Testing 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>
-Resynchronize the clock
-<code>w32tm /resync</code>
-Show current timezone settings
-<code>w32tm /tz</code>
-List external NTP servers (peers)
-<code>w32tm /query /peers</code>
-**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. That may have changed since then, but it isn't very documented.
-<code>w32tm /config /manualpeerlist:0.nl.pool.ntp.org,1.nl.pool.ntp.org,2.nl.pool.ntp.org,3.nl.pool.ntp.org,0x1 /syncfromflags:MANUAL /reliable:yes /update ; net stop w32time ; net start w32time ; w32tm /query /peers /verbose</code>
-<code>w32tm /config /manualpeerlist:time.cloudflare.com,0x1 /syncfromflags:MANUAL /reliable:yes /update ; net stop w32time ; net start w32time ; w32tm /query /peers /verbose</code>
-===== 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>
-===== NTP Servers =====
-List of Stratum 1 servers
-  * [[http://tf.nist.gov/tf-cgi/servers.cgi|NIST]]
-  * [[http://support.ntp.org/bin/view/Servers/StratumOneTimeServers|ntp.org]]
-National Physics Laboratory hosts two public "Stratum 2" servers. This means their servers sync directly to atomic clocks.
-**DO NOT** configure your system to use Google Public NTP together with non-leap-smearing NTP servers. e.g. do not combine Google NTP with Cloudflare NTP as they [[https://developers.cloudflare.com/time-services/ntp/usage|do not implement leap smearing]]. Smearing is used by Google, AWS, and Facebook NTP servers but not Cloudflare.
-^Operator ^ Server FQDN ^ Server IP ^ Stratum ^ RefID ^ Source Type or FQDN ^ Delay ^ Location ^ Supports iBurst ^
-| Cloudflare | time.cloudflare.com | 162.159.200.1 | 3 | 10.21.8.19 | Internal Cloudflare? | 13.080 | UK | |
-| Cloudflare | time.cloudflare.com | 162.159.200.123 | 3 | 10.21.8.19 | Internal Cloudflare? | 13.896 | UK | |
-| Microsoft | time.windows.com | 51.145.123.29 | 3 | 25.66.230.5 | Internal Microsoft? | 13.896 | UK | |
-| Zen Internet | ntp0.zen.co.uk | 212.23.8.6 | 2 | 195.66.241.3 | ntp1.linx.net | 11.642 |  | |
-| Zen Internet | ntp1.zen.co.uk | 212.23.10.129 | 2 | 85.199.214.99 | server1.quickdrivingtestcancellations.net | 16.948 | UK | |
-| National Physics Laboratory | ntp1.npl.co.uk | 139.143.5.30 | 2 | 139.143.45.169 | ? | 16.457 | UK | |
-| National Physics Laboratory | ntp2.npl.co.uk | 139.143.5.31 | 2 | 139.143.45.169 | ? | 17.329 | UK | |
-| Manchester University | ntp2a.mcc.ac.uk | 130.88.202.49 | 2 | 193.62.22.66 | ntp0.ja.net | 22.581 | UK | |
-| Manchester University | ntp2b.mcc.ac.uk | 130.88.203.13 | 2 | 130.88.203.13 | ntp0.ja.net | 22.282 | UK | |
-| Manchester University | ntp2c.mcc.ac.uk | 130.88.200.6 | 2 | 193.62.22.66 | ntp0.ja.net | 22.135 | UK | |
-| Manchester University | ntp2d.mcc.ac.uk | 130.88.212.143 | 2 | 193.62.22.74 | ntp1.ja.net | 22.771 | UK | |
-| JANET, Harwell | ntp0.ja.net | 193.62.22.66 | 1 | .MSF. | MSF Radio Clock Receiver | 15.981 | UK | |
-| JANET, Harwell | ntp1.ja.net | 193.62.22.74 | 1 | .MRS. | N/A | 26.042 | UK | |
-| JANET, Harwell | ntp2.ja.net | 193.62.22.98 | 2 | 193.62.22.74 | ntp1.ja.net | 22.849 | UK | |
-| JANET, Harwell | ntp3.ja.net | 193.62.22.90 | 1 | .PPS. | N/A | 26.305 | UK | |
-| JANET, Harwell | ntp4.ja.net | 193.62.22.82 | 1 | .DCFa. | DCF77 | 17.528 | UK | |
-| Google | time.google.com | time1-time4  | 1 |  |  |  | | Yes |
-| Google | time1.google.com | 216.239.35.0  | 1 | .GOOG. | N/A | 20.393 | | Yes |
-| Google | time2.google.com | 216.239.35.4 | 1 | .GOOG. | N/A | 20.399 | | Yes |
-| Google | time3.google.com | 216.239.35.8 | 1 | .GOOG. | N/A | 20.514 | | Yes |
-| Google | time4.google.com | 216.239.35.12 | 1 | .GOOG. | N/A | 22.899 | | Yes |
-| Facebook | time.facebook.com | time1-time5  | 1 |  |  |  | | Yes |
-| Facebook | time1.facebook.com | 129.134.28.123 | 1 | .FB... | N/A | 25.595 | | Yes |
-| Facebook | time2.facebook.com | 129.134.29.123 | 1 | .FB... | N/A | 16.803 | | Yes |
-| Facebook | time3.facebook.com | 129.134.25.123 | 1 | .FB... | N/A | 12.037 | | Yes |
-| Facebook | time4.facebook.com | 129.134.26.123 | 1 | .FB... | N/A | 18.341 | | Yes |
-| Facebook | time5.facebook.com | 129.134.27.123 | 1 | .FB... | N/A | 16.546 | | Yes |
-| Apple | time.apple.com | 17.253.108.253 (and others)  | 1 | .SHM. |  | 17.343 | | Yes |
-| Apple | time.euro.apple.com | 17.253.34.125 (and others) | 1 | .SHM. |  |  9.889 | | Yes |
-| Leo Bodnar Electronics | ntp1.leontp.com | 51.155.16.62 | 1 | .GPS. | N/A | 36.932 | UK | |
-| Leo Bodnar Electronics | ntp5.leontp.com | 85.199.214.98 | 1 | .GPS. | N/A | 16.523 | UK | |
-| Leo Bodnar Electronics | ntp6.leontp.com | 85.199.214.99  | 1 | .GPS. | N/A | 15.949 | UK | |
-| Leo Bodnar Electronics | ntp7.leontp.com | 85.199.214.100 | 1 | .GPS. | N/A | 16.002 | UK | |
-| Leo Bodnar Electronics | ntp8.leontp.com | 85.199.214.101 | 1 | .GPS. | N/A | 16.595 | UK | |
-| Leo Bodnar Electronics | ntp9.leontp.com | 85.199.214.102 | 1 | .GPS. | N/A | 15.965 | UK | |
-| Xentex IT Solutions | ntp.xtx.cloud | 81.133.66.177 | 1 | .PPS. | N/A | 24.301 | UK | |
-More information on Google's NTP offering can be found [[https://developers.google.com/time/faq|here]]. Google 'smear' a leap second over the course of a the hour either side of the leap second. Do not mix NTP servers that 'smear' and NTP servers that do not 'smear'.
-Google uses its own NTP servers (see above) for its public DNS servers (see below). If you cannot configure multiple servers, ''time.google.com'' will automatically select an appropriate Google server nearby.
-===== 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]]