NTP Introduction

NTP stands for Network Time Protocol, which is the standard way of distributing time over the Internet. The software and protocols are freely available.

The way NTP works is that your client (desktop, laptop, etc) is configured to contact a number of servers that respond with what they think the time is. The client processes each response to reduce the inaccuracies that have crept in during transmission and then combines the answers it receives using a clever algorithm to converge on the most accurate time it can.

NTP has the concept of a ‘stratum’, which represents how many steps away the server is from a reference clock that provides a source of known time. Reference clocks such as atomic clocks are called stratum 0 devices and every step away from them adds one to the stratum. For example a server directly connected to a reference clock is a stratum 1 server, a server that gets it time from one or more stratum 1 servers is a stratum 2 server, and so on. So a stratum 1 server is as good as it gets. Nowadays many stratum 1 servers are connected to differential GPS receivers that pick up time signals from GPS satellites as their stratum 0 time source.

The way the Internet is designed means that any stream of packets that travels a long distance is inevitably going to see some packets lost, others delayed and possibly some corrupted. The Internet copes with these failures pretty well but it does make it more complex for precision signalling as required for time synchronisation. So the more accurate your time needs, the closer you need your servers to be and the lower stratum the better, to reduce the delays and inconsistencies that reduce the accuracy of time.

The NTP servers that people connect to are normally provided by volunteers as there are virtually no official NTP providers. A few countries have scientific laboratories responsible for the national time standard that also provide NTP but the NTP service is normally a nice to have feature rather than a core service. In New Zealand the Measurement Standards Laboratory provide a stratum 1 NTP server connected to their Caesium clock.

Since the turn of the century the demands on NTP providers has increased as a result of several environmental changes. The telephone networks that used to provide time as part of the telephone signal have now moved to IP networks that do not have timing built in. And there has been the huge proliferation of consumer devices that use the Internet and are consumers of NTP services. Yet none of this has been matched by a corresponding increase in NTP service provision. NTP is basically one of those forgotten little corners of the Internet that we actually all rely on a daily basis.

Our provision of these servers is intended to redress this imbalance within NZ and we hope others consider taking similar steps too.

If you are interested you should also read the Wikipedia page on Time in New Zealand and possibly pay a visit to the Carter Observatory as they both explain the history very well.