devans@timetools.co.uk.
Best regards
David Evans
http://www.timetools.co.uk
How to Build a NTP Server
NTP, or Network Time Protocol, is a standard Internet
protocol used to distribute accurate time to client
computers. NTP is freely downloadable from the NTP website.
With the addition of an accurate reference clock, you can
build your own highly accurate stratum one NTP Server.
This article describes how to build and configure your very
own stratum one NTP Server. By adding a low-cost GPS or
radio time reference to your Linux machine, you can have
your very own highly accurate time reference. Your NTP
server can be used to synchronize all the machines on your
network to the precise time.
NTP is available as source code for compilation and
configuration on a Linux machine. The source code freely
downloadable from the NTP.org website. Many Linux
distributions, such as Redhat and Debian have a
pre-installed version of NTP. Other distributions may
include it as an installable RPM.
In order to build a stratum one NTP server, you need an
accurate external timing reference. Many timing references
are available, most utilise GPS or national time and
frequency radio sources such as WWVB, DCF77 and MSF. The
Global Positioning System (GPS) is a great timing
reference, since it is available worldwide and the
equipment required for receiving time and positioning
information is very low-cost.
Most GPS receivers have a RS232 serial port that can be
easily interfaced to a PC. The receiver generally provides
continuous time and positioning information in a standard
format known as NMEA. An NTP server can utilise the timing
information provided by a NMEA receiver as an accurate
timing reference. Additionally, some receivers also provide
a highly accurate pulse output that can be utilised by a
NTP server as a highly precise epoch. Any timing pulse
generated by a GPS receiver may need to be converted into a
usable RS232 signal level. This can be achieved by feeding
the pulse into a RS232 driver chip.
Many radio based reference clocks are available that
utilise national time and frequency standards. WWVB is a US
radio time and frequency transmission, DCF77 is transmitted
from Germany, MSF is available throughout the UK. The
advantage of a radio signal as a reference clock for your
NTP server is that you can usually pick up a good signal
indoors, close to the NTP server. In contrast, GPS requires
an antenna with a good view of the sky.
Once you have your NTP server external reference clock
set-up and installed, you need to configure the clock in
the NTP configuration file 'ntp.conf'. This usually
involves finding and specifying the reference clock code
for your timing reference. Once configured, your NTP server
will act as an accurate source of time for your network
time clients.
Most modern computers operating systems can utilise NTP to
synchronize time. Linux and Unix machines can utilise the
NTP distribution itself. Modern Windows operating systems
such as XP and 2003 have pre-installed SNTP clients that
can point to the IP address or DNS name of a NTP server for
synchronisation. Many network devices such as routers and
switches can also utilise your NTP server for
synchronization.
----------------------------------------------------
Dave Evans is a technical author with a background in NTP
Server solutions and telecommunications. Dave provides a
technical authoring service to NTP reference clock and NTP
server manufacturers. Dave has also provided a
configuration, installation and repair service for computer
timing systems. Find out more about ntp server systems at:
http://www.timetools.co.uk/ntp-servers/ntp-server-s5000.htm
