8
Time Servers and the Importance of Synchronisation.
Category: UncategorizedThis article explains the importance of time synchronisation in modern computer networks and explores NTP (Network Time Protocol) and how it is used.
Time
servers are like other computer servers in the sense they are usually located
on a network. A time server gathers timing information, usually from an
external hardware source and then synchronises the network to that time.
Often time
servers are synchronised to a UTC (Coordinated Universal time) source which is
the global standard time scale and allows computers all over the world to
synchronised to exactly the same time. This has obvious importance in
industries where exact timing is crucial such as the stock exchange or airline
industry.
There are
various sources that a time server can use as a timing reference. The Internet
is an obvious source, however, internet timing references from the Internet
such as nist.gov and windows.time can not be authenticated, leaving the time
server and therefore the network vulnerable to security threats.
There are
authenticated alternatives to the Internet, the most common being to use the
GPS network. As the Global Positioning System is reliant on knowing exactly
what time it is to ensure reliable location information, this information can
be utilised by a time server.
A simple
GPS antenna connected to the time server will allow the GPS timing reference to
be regularly checked by the time server. A GPS time server will be accurate to
within a few hundred
nanoseconds (a nanosecond = a billionth of a second).
There
are also a number of national radio broadcasts such as the WWVB signal from
Colorado in the US , the MSF signal from Cumbria in the UK and the DCF-77 signal
from Frankfurt in Germany.
These
radio signals are limited in their range though and even in major cities such
as London it can be difficult to receive a decent enough signal.
Most
timing servers use NTP (Network Time protocol) there are other protocols
available but NTP is predominately used and is thought of as the standard for
timing protocols. NTP has been around for over 25 years and is currently on
version 4 but is always being updated which is probably why it is by fat the
most common timing protocol.
NTP time servers work within the TCP/IP suite and rely on
UDP (User Datagram Protocol). A less complex form of NTP - Simple Network Time
Protocol (SNTP) is used in some devices and applications where high accuracy
timing is not as important and is also included as standard in Windows software
(although more recent versions of Microsoft Windows have the full NTP installed
and the source code is free and readily available on the Internet from ntp.org).
About the author
Richard N Williams is a technical author and a
specialist in the telecommunications and network time synchronisation industry
helping to develop dedicated time server products. Please visit us for
more information about a GPS time server or other NTP
products.
Tags: computer servers, coordinated universal time, dcf 77, exact timing, external hardware, global positioning system, gps antenna, gps network, gps timing, hardware source, nanoseconds, network time protocol, radio broadcasts, radio signals, time servers, time source, time synchronisation, timing reference, wwvb signal