Network Time Protocol 30 Years Later
The Egyptians had large black obelisks to track the movement of the sun.
The Greeks had a water powered escapement mechanism, which transferred rotational energy into intermittent motions.
The Chinese had a mercury powered escapement mechanism, developed in the 10th century.
Today we have modern clocks, and we also have network time protocol.
The tracking of time grew in importance alongside the sophistication of society. Ancient societies needed time keepers to regulate growing aspects of their civilizations–including business, political, even social activities. These mechanisms grew more sophisticated throughout the centuries, until the advent of mechanical clocks using wheels and balance springs.
Today, much of the world operates under a standard 24-hour day, kept track with sophisticated instruments located in various places around the world. There have been attempts to circumvent this, as well as the number of days per week. For instance,
- The Soviet Union (between 1929 and 1931) attempted (and failed) to enforce five and six days weeks.
- After the French Revolution, French revolutionaries tried to institute a 10-hour clock.
Keeping track of time seems very stable today and technology helps. The working 31 Global Positioning System satellites all have an atomic clock built in. This helps not just for a safety valve in case the ones on Earth malfunction but for GPS systems in cars and on cell phones.
When the Internet started to gain steam in the 1980s, a method called Network Time Protocol (NTP) was instituted to keep the clocks between computer systems in sync. It is one of the oldest Internet protocols used today. It was designed by David Mills at the University of Delaware and has applications for computer to computer communication.
The NTP synchronizes all included computers within a few milliseconds of Coordinated Universal Time. While it’s usually described in terms of a client-server model, it can be seen as a peer-to-peer model where both computers consider the other a potential time source.
The NTP is built on a hierarchy of communicating clocks. They are called “stratums,” which refers to the closeness each computer is to the time server. The scale goes from one to 15, with one being the most accurate.
The NTP time server starts with stratum 0. This stratum includes NTP clocks that are highly accurate. An NTP clock in this category includes atomic time-keeping devices, GPS satellites, or radio clocks. An NTP clock in this category has a very accurate pulse-per-second that communicates the time stamp to the connecting computers.
An NTP GPS clock in this category would relay that information to the connecting computers in Stratum 1. These computers would then relay the information to connecting computers in Stratum 2. Therein and so forth all the way down to Stratum 15.
NTP operates on a clock synchronization algorithm. This algorithm involves a synchronized response when a computer is requesting information from multiple computers on a server.
For instance, an NTP time clock in Stratum 4 might request information from multiple computers in Stratum 3. Because the response from the multiple computers may be delayed by certain amounts in real time, the NTP time clock that is requesting the responses must compute their return–called the round trip delay mechanism.
NTP time clocks are useful for clock synchronization especially in companies and while there are other protocols set for clock synchronization, NTP is still widely used.