Where to use NTP/PTP Time Servers?
What is Time Server?
A time server is a computer that reads the actual time from a reference clock and distributes it to clients using a computer network. Time servers can use GPS or atomic clocks as time references and can be dedicated devices or existing network servers with additional software.
Network Time Protocol (NTP) / Precision Time Protocol (PTP)
The Network Time Protocol (NTP) is a networking protocol for clock synchronization between computer systems over packet-switched, variable-latency data networks.
NTP is intended to synchronize all participating computers to within a few milliseconds of Coordinated Universal Time (UTC). It uses the intersection algorithm, a modified version of Marzullo’s algorithm, to select accurate time servers and is designed to mitigate the effects of variable network latency.
NTP can usually maintain time to within tens of milliseconds over the public Internet, and can achieve better than one millisecond accuracy in local area networks under ideal conditions. Asymmetric routes and network congestion can cause errors of 100 ms or more.
The Simple Network Time Protocol (SNTP) was developed as a simplified version of NTP, eliminating the need for long-term storage of state. SNTPv4, which includes features from NTPv4, was merged into the main NTPv4 standard in 2010. While SNTP is interoperable with NTP, its simple algorithms provide less accurate time synchronization.
Both Network Time Protocol (NTP) and Simple Network Time Protocol (SNTP) are popular methods to synchronise clocks across a Local Area Network (LAN) with accuracy to the millisecond range. Greater precision is required however in many industrial applications of time synchronisation. Wherever processes require that level of accuracy, such as within automation and control systems, measurement and automatic test systems, power generation, transmission and distribution systems, and telecommunications, Precision Time Protocol (PTP) is the solution.
With the needs of network design becoming more widespread in many industries, the need for accurate timing is deepening.
When there are many IEDs (Intelligent Electronic Devices) on a network with their own clocks this becomes difficult to coordinate, so central time servers become useful. Proper precision timing on a network can maintain a very accurate source of time to keep all IEDs in sync, often within 100ns. Uses for accurate time are many, especially in scenarios where digital instructions need to be executed at the right time or data is being transferred at high rates. Installations also regularly include event logging as a key feature.
Getting the exact time an event occurred is important in many industries where faults need to be traced. The speed of electricity makes this especially important for the power sector, which also uses precise timing for phase measurement, multi-rate billing accuracy, locating faults on transmission lines, relay testing and more. In some cases a network will need to be synced across many miles. In such cases, GNSS based timing is often the only cost effective option.
