MSL NTP Server
The Network Time Protocol (NTP(external link)) is a mechanism for synchronising the time on computers. NTP can synchronise the time on two computers with a typical accuracy of tens of milliseconds.
Using Network Time Synchronisaton
Network Time Protocol (NTP) is a robust timing method for synchronising a computer's clock with UTC. It is one of the oldest protocols on the internet.
Most operating systems, such as Linux, MacOS and Windows, are able to synchronise their time using NTP or a similar method (assuming appropriate permissions are enabled) and users should consult the appropriate documentation as to how this can be done.
To determine their time offset from UTC by NTP, client computers repeatedly make network requests to at least one, and preferably more, NTP servers and use an algorithm(external link) to determine the 'best' reference clock. This limits the accuracy of NTP-derived time offsets to around half the roundtrip network delay – usually in the order of milliseconds (ms).
The Internet Engineering Task Force (IETF) have published a Best Practice guide on implementing Network Time Protocol (NTP) in RFC8633(external link)(external link).
For robustness, NTP clients should be configured to use:
- redundant sources of time (RFC8633 §3.2(external link)) and, if possible,
- a diversity of timing sources (RFC8633 §3.3(external link)).
Further background information on NTP can be found on the main NTP website http://www.ntp.org/(external link)(external link)(external link).
MSL NTP servers
The MSL Stratum 1(external link) NTP servers are synchronised using phase and frequency signals from the New Zealand Time Standard – UTC(MSL) – which is based on caesium atomic clocks. NTP server time is typically stable with respect to UTC(MSL) to around 1 microsecond, but variability in the network delays limits the accuracy for remote clocks/clients to milliseconds.
The individual servers are collected into a 'pool(external link)' which provides a single point of access. Routing of NTP requests to a server is managed by a load-balancer running on our corporate IT infrastructure which distributes requests using round-robin scheduling. The servers in the pool are managed by Measurement Standards Laboratory. Using a pool provides NTP clients/users access to an NTP server, with a fixed name/IP address, while allowing Time Standards staff to take individual servers offline as necessary.
Accessing MSL NTP servers
The MSL NTP pool can be accessed from computers in the NZ internet region via the name pool.msltime.measurement.govt.nz or IP address 161.65.172.9. NTP requests from outside the NZ internet domain are geo-blocked.
The servers are publicly available to all connections from within NZ. Please note, these servers only respond to NTP and Simple Network Time Protocol (SNTP) requests. They do not respond to "datetime" requests.
To avoid overloading the MSL NTP pool, please limit access to three client machines and direct any additional clients to these, which will then be Stratum 2(external link) servers.
In November 2022 support for the legacy address/names 131.203.16.6, msltime.irl.cri.nz and msltime1.irl.cri.nz was discontinued. Support for the NTP server names msltime.measurement.govt.nz and msltime1.measurement.govt.nz will continue for the foreseeable future as aliases of pool.msltime.measurement.govt.nz. It is strongly recommended users update their NTP configuration to use pool.msltime.measurement.govt.nz or 161.65.172.9 to access the MSL NTP service.
Registering use of MSL NTP servers
The MSL NTP pool is currently open-access but serious users are strongly encouraged to register their use by sending the (static) IP address of their server(s) and a contact email address to info@measurement.govt.nz(external link) to receive service notifications and in case we need to restrict access in the future. To avoid overloading the MSL NTP pool, please limit access to three client machines and direct any additional clients to these, which will then be Stratum 2(external link) servers.
Please Note: Only users who register via mailto:info@measurement.govt.nz will be informed of any changes in availability or operation of the MSL NTP service. For this reason use of a generic email address (e.g. info@organisation.org.nz), rather than a specifc individual (for instance rowan.smith@organisation.org.nz), is advised. Organisations should also periodically review and update their information as necessary.
Please contact us if you have any queries about this service.