The Importance of Accurate Time on Computer Networks
The synchronization of time on computers and networks is often vitally important. Without it, the time on individual computers will slowly drift away from each other at varying degrees until potentially each has a significantly different time. In systems that rely on ordered events occurring at specific times or logging of events, this can be a real problem. For instance, transactions generated by a computer with a system time slower than another computer may log a transaction as being received before the other computer even though it was generated after it.
Sequencing Critical Operations and Events
In a control environment, with distributed PLC’s, each performing an individual task on a specific job, without synchronization, they will not complete their tasks in an ordered manner. Also wireless sensor networks need accurate time so that events can be logged correctly.
A mechanism is required to disseminate accurate time around a network to computers and network devices in order to maintain order.
The NTP and SNTP Protocols
The Network Time Protocol (NTP) was introduced to provide just such a mechanism. It provided complex algorithms to maintain a high degree of time synchronization of computers on a network. Time clients obtain highly precise timing information from a time server in order to calibrate their own internal system time. In this manner all the computers and devices on a network can operate on the same accurate time. NTP is available on most operating systems, including Linux with ports for Windows 7 and Windows Server 2008.
A NTP server appliance is a hardware device that synchronizes to a hardware clock, such as GPS or a radio time and frequency broadcast. The device maintains a highly precise time reference and provides a network with an accurate source of time.
The Linux and Unix Operating Systems
NTP was originally developed for the Linux operating system. It is generally available for most versions of Linux as an installable module. Indeed most distributions provide NTP in the default install.
Windows 7, 8 and Server 2008 Operating Systems
Microsoft utilize a version of NTP called Simple Network Time Protocol (SNTP) in their Windows 7, 8 and Server 2008 operating systems. SNTP is as the name suggests a simplified version of the full-blown NTP protocol. Many of the algorithms used in NTP to maintain a very precise time have been simplified or removed from SNTP. The Windows time application runs as a service and is called ‘Windows Time’ in the service list. The program file is ‘w32time.exe’. SNTP allows a computer to synchronize to a full-blown NTP server. There are no difference in the actual exchange of information between NTP and SNTP. A port of the full NTP suite of programs can be built for Windows operating systems which allows much more robust timing.
Synchronizing Network Infrastructure and Devices
Many network infrastructure appliances and devices can utilize the network time protocol, including routers and switches, CCTV cameras and DVR’s. Most only require the IP address of a NTP server to be specified.
TimeTools SR9210 NTP network time server obtains very accurate time from a hardware clock reference, such as GPS or radio. It maintains a very accurate time on its internal real-time clock and provides a network with a time reference. It can easily synchronize network time clients to within a few milliseconds of the correct time. The unit has impeccable green credentials consuming only 5 watts. The quality and reliability of the appliance is further demonstrated by the provision of a 5-year warranty.
TimeTools is a leading manufacturer of GPS clock systems and network time appliances for synchronizing servers, workstations and other network devices. For more than a decade, TimeTools has been supplying high-quality, great value, timing equipment to large, high-profile, companies around the world.