NTP: It's About Time - Page 2
The specifics of setting up time synchronization and using NTP on a system will depend on the platform(s) you are using. In most instances, setup is simply a case of installing (and if necessary compiling) the NTP software, loading it, and pointing it at a reliable time source. Depending on how many other devices you want to synchronize, you can then configure NTP on other devices to also point to the reliable time source, or to the original server that is receiving time. In turn, other servers can be configured to receive time from these other servers, creating a stratum model of your own.
The question of which time source to point to is an interesting one. As with many things related to the Internet, time servers are maintained, added to, and amended by people and organizations on a voluntary basis. As such, neither the availability nor the accuracy of the servers and/or service is guaranteed. It would be easy to assume that the Stratum-1 time sources are completely accurate, but it's not always the case. A survey conducted by individuals at MIT in 1999 found that a large number of the Stratum-1 servers were issuing the wrong timein one case, by over six years!
Setting Up NTP
Setting Up an NTP Time Server
Synchronizing your systems with one of these public time servers may be appropriate if all your systems have access to a public NTP time server, but in practicality it may not be possible. A more reliable, secure, and self-sufficient option is to create a reference time server of your own, and then use it to provide time to servers across your enterprise. To create an NTP time server, you will first need a mechanism for ascertaining accurate time, such as a radio receiver or GPS time receiver. These devices commonly come as either plug-in expansion cards or as external devices that plug into the RS-232 port on the system in question. Prices start at a few hundred dollars and go up from there. Using these devices, the local clock on the system is kept accurate. NTP software can then be used to communicate this time to the operating system and other servers.
Although time serving is designed to be a low-overhead service, if you have many clients who will require synchronization, consider creating a dedicated time server or purchasing a purpose-made time server in a box system. The only drawback is that these can easily cost in excess of $5,000. This strategy may sound expensive, but when you consider the money often invested in other areas of network management and resilience, it is still quite reasonable.
As systems become more and more distributed, the importance of having accurate time across the enterprise will increase accordingly. Network Time Protocol fulfills this need in a relatively simple and easy to implement manner. //
Drew Bird (MCT, MCNI) is a freelance instructor and technical writer. He has been working in the IT industry for 12 years and currently lives in Kelowna, B.C., Canada. You can e-mail Drew at firstname.lastname@example.org.