The NTP subnet in New Zealand

The Network Time Protocol (NTP) is used to synchronise the clocks of a significant percentage of the computers that make up the internet. Occasional large adjustments made to the local clock of our department’s main NTP server (kaka) lead us to investigate the state of the NTP subnet in New Zealand. We examined the structure of the NTP subnet within New Zealand, recorded performance information for over 350 New Zealand NTP servers and investigated the reasons for the occasional large adjustments made to kaka’s clock. The overall NTP performance figures for New Zealand NTP servers compare favourably with those reported in a world-wide study of NTP performance. However, the lack of any primary NTP servers in New Zealand, and the concentration of all secondary servers at a single site, were major factors in the occasional large adjustments made on kaka. Also, a feature of the NTP filtering algorithm was a factor in some of the large adjustments. At a more detailed level, several cases were found in which an NTP configuration could be improved. Our overall conclusion is that the accuracy of NTP in New Zealand could be improved by installing two or three primary servers, backed up by several secondary servers.