NTP [Network Time Protocol]
Unit 4, 2-8 South St
Rydalmere, NSW 2116
T: 13 14 91
F: 1800 659 025
W: www.simplextime.com.au
NTP definition & Application
Document: NTP.doc Issued: October 2008
The ability to monitor and configure NTP clocks from one computer workstation means less
visual inspection and a real time saving by maintenance personnel.
If your organization spreads across multiple sites or buildings and has an existing Wide Area
Network (WAN) cost savings can be realized by not having to install site wide hard wired
control cabling and Master clocks.
Note:
1. The accuracy of the NTP at the end device is dependant on the device itself, the speed
of the network and accuracy, the stratum of the chain of NTP servers, and version of
the NTP protocol and supporting latency correction algorithms. Typically the error is
less than 500 milliseconds or 0.5 seconds.
2. When the LAN is not available NTP devices generally keep running but only
synchronise with a time source when they can access the configured NTP server
through the LAN.
3. It choosing an NTP clock solution you may need additional LAN access points to
service each NTP clock device. This is an IT matter
Q: What is NTP?
A: Network Time Protocol (NTP) is a protocol that provides a reliable way of propagating the
current time over TCP/IP based networks. The time that is published over NTP is the UTC
time. UTC time is referenced as the time at Greenwich Mean Time without any form of Day
Light Saving or Time Zone adjustment.
The NTP protocol compensates for the transmission delay experienced between connected
NTP strata nodes to maintain accurate time.
NTP protocol has evolved and improved in accuracy since its inception in 1985. These
improvements have brought about the need for new compliance standards. As such there are a
few versions of NTP in use. Care needs to be taken when selecting NTP products to ensure
version compatibility. The newer version NTP protocols have been designed to accommodate
the older NTP version end devices.
It has become the de facto standard for synchronising Internet computers and other networked
devices to Universal Coordinated Time (UTC), which is accomplished by having these
devices reference a common time source – i.e., an atomic clock or a network time server.
NTP uses TCP/IP Port 123 for communication. It is essential that the LAN/WAN firewall or
router to permit transmission on Port 123 to ensure proper communication with the NTP
server(s).
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