In retrospect, while NTP has been a technical adventure in its own right by providing the means for accurate and dependable time synchronization, NTP has also been an enabling technology for practical uses of synchronized clocks. Using NTP for timestamping stock trades, radio and television broadcast programs, and distributed data acquisition readily springs to mind, but as Liskov pointed out [54], synchronized clocks are vital to some important distributed algorithms and could improve performance in others.
Near the end of the first decade of the new century, it is quite likely that precision timekeeping technology has evolved about as far as it can given the realities of available computer hardware and operating systems. Using specially modified kernels and creative interface devices, Poul-Henning Kamp and I have demonstrated that computer time in a modern workstation can be disciplined within some tens of nanoseconds relative to a precision source such as a cesium or rubidium frequency standard [40]. While not many computer applications would justify such heroic means, the demonstration suggests that the single most useful option for high-performance timekeeping in a modern workstation may be a temperature-compensated system clock oscillator.
It is likely that future deployment of public NTP services might well involve an optional secure timestamping service, perhaps for a fee. This agenda is being pursued as a commercial enterprise. In fact, several NIST servers are now being equipped with timestamping services. This makes public key authentication a vital component of such a service, especially if the Sun never sets on the service area.
One of the most fascinating developments in network timekeeping is the application of the technology in planetary and deep-space missions.Perhaps the most interesting lesson to learn from the adventure is, as the timekeeping and security functions are so intertwined on Earth, the timekeeping and navigation functions are so intertwined in space.
Parting Shots
Internet timekeeping is considered by some to be a hobby, and even I have revealed a likeness to amateur radio. There seems no other explanation why the volunteer timekeeper corps has continued so long to improve the software quality, write clock drivers for every new radio that comes along, and port the stuff to new hardware and operating systems. The generals in the army have been revealed in the narrative here, but the many soldiers of the trench must be thanked as well, especially when the hardest job is convincing the boss that time tinkering is good for business. A list of important contributors is available at http://www.ntp.org and on the copyright page in the NTP software documentation.
We are done here.
