NTP Reference Clock Statistics

I run four NTP Stratum 1 servers with attached reference clocks. Below this introduction are graphs that show performance statistics about them, as well as some other internal and external NTP servers that I monitor.

tick, tock, toe, and cesium are dedicated NTP servers, built from Soekris net4501 single-board computers with 133MHz AMD "Elan" processors (486 class). That may not seem like much horsepower, but these little guys have a secret weapon: a very high resolution timer that can be used to get timekeeping accuracy far better than any normal PC.

In addition, these Soekrises (Soekri?) have been modified to replace the normal crystal oscillator with a synthesizer driven by an external high stability source which makes them almost immune to temperature variations and other errors.

I've written up details on how to convert the net4501 computers for high performance timekeeping.

Here are details about the four servers:


The charts below show the offset of each of the internal servers, as well as some internal and external servers, referenced to cesium. All the internal machines are on their own 100 Mb Ethernet switch, which connects to the house GigE network, so network traffic and delays are low, and these systems represent probably the best an NTP network can do using standard networking hardware. There's also a chart, for what it's worth, showing what cesium thinks is the offset of the HP 5061A clock that drives it.

The "current day" charts show performance for the current day since 0 UTC (updated hourly). The next set of charts shows the preceding seven full days, plus the current day. The final charts show 30 days of data. (Here are the tools I used to generate these plots.)

One of my externally-visible stratum 2 servers, meow.febo.com is part of the pool.ntp.org project. Statistics about meow are here.

Current Day


Last Week


Long Term