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diff --git a/docs/system/ntp.rst b/docs/system/ntp.rst index 95ff0692..0836f2fa 100644 --- a/docs/system/ntp.rst +++ b/docs/system/ntp.rst @@ -1,19 +1,56 @@ .. _ntp: +### NTP -=== +### -there are 3 default NTP server set. You are able to change them. +:abbr:`NTP (Network Time Protocol`) is a networking protocol for clock +synchronization between computer systems over packet-switched, variable-latency +data networks. In operation since before 1985, NTP is one of the oldest Internet +protocols in current use. -.. code-block:: none +NTP is intended to synchronize all participating computers to within a few +milliseconds of :abbr:`UTC (Coordinated Universal Time)`. It uses the +intersection algorithm, a modified version of Marzullo's algorithm, to select +accurate time servers and is designed to mitigate the effects of variable +network latency. NTP can usually maintain time to within tens of milliseconds +over the public Internet, and can achieve better than one millisecond accuracy +in local area networks under ideal conditions. Asymmetric routes and network +congestion can cause errors of 100 ms or more. - set system ntp server 0.pool.ntp.org - set system ntp server 1.pool.ntp.org - set system ntp server 2.pool.ntp.org +The protocol is usually described in terms of a client-server model, but can as +easily be used in peer-to-peer relationships where both peers consider the other +to be a potential time source. Implementations send and receive timestamps using +:abbr:`UDP (User Datagram Protocol)` on port number 123. -To set up VyOS as an NTP responder, you must specify the listen address and optionally the permitted clients. +NTP supplies a warning of any impending leap second adjustment, but no +information about local time zones or daylight saving time is transmitted. -.. code-block:: none +The current protocol is version 4 (NTPv4), which is a proposed standard as +documented in :rfc:`5905`. It is backward compatible with version 3, specified +in :rfc:`1305`. - set system ntp listen-address 192.168.199.1 - set system ntp allow-clients address 192.168.199.0/24 +Configuration +============= + +.. cfgcmd:: set system ntp server '<address | fqdn>' + + Configure one or more servers for synchronisation. Server name cen be either + an IP address or :abbr:`FQDN (Fully Qualified Domain Name)`. + + There are 3 default NTP server set. You are able to change them. + + * 0.pool.ntp.org + * 1.pool.ntp.org + * 2.pool.ntp.org + +.. cfgcmd:: set system ntp listen-address '<address>' + + Setup VyOS as an NTP responder, you must specify the `<address>` and + optionally the permitted clients. Multiple listen addresses can be + configured. + +.. cfgcmd:: set system ntp allow-clients address '<address>' + + List of networks or client addresses permitted to contact this NTP server. + Multiple networks can be configured. |