Using the WWVB Signal for Time Synchronization
We all rely on the time to keep our days scheduled. Wristwatches, wall clocks and even the DVD player all tell us the time but on occasion, this is not accurate enough, especially when time needs to be synchronized.
There are many technologies that require extremely accurate precision between systems, from satellite navigation to many internet applications, accurate time is becoming increasingly important.
However, achieving precision is not always straight forward, especially in modern computer networks. While all computer systems have inbuilt clocks, these are not accurate time pieces but standard crystal oscillators, the same technology used in other electronic clocks.
The problem with relying on system clocks like this is that they are prone to drift and on a network consisting of hundreds or thousands of machines, if the clocks are drifting at a different rate – chaos can soon ensue. Emails are received before they are sent and time critical applications fail.
Atomic clocks are the most accurate time pieces around but these are large scale laboratory tools and are impractical (and highly expensive) to be used by computer networks.
However, physics laboratories like the North American NIST (National Institute of Standards and Time) do have atomic clocks which they broadcast time signals from. These time signals can be used by computer networks for the purpose of synchronization.
In North America, the NIST broadcasted time code is called WWVB and is transmitted out of Boulder, Colorado on long wave at 60Hz. The time code contains the year, day, hour, minute, second, and as it is a source of UTC, any leap seconds that are added to ensure parity with the rotation of the Earth.
Receiving the WWVB signal and using it to synchronize a computer network is simple to do. Radio reference network time servers can receive this broadcast throughout North America and by using the protocol NTP (Network Time Protocol).
A dedicated NTP time server that can receive the WWVB signal can synchronize hundreds and even thousands of different devices to the WWVB signal ensuring each one is to within a few milliseconds of UTC.
