HP-UX Internet Services Administrator's Guide (May 2010)

Setting up a Spectracom Netclock/2
The following steps describe how to set up a Spectracom Netclock/2:
1. Install and connect the WWVB receiver to a serial port on the HP-UX machine.
2. Append the following entries in the /etc/ntp.conf file:
server 127.127.4.1 minpoll 3 maxpoll 4
# no fudge required
# fudge 127.127.26.1 time1 -0.930 #s800
3. Create the following symbolic link:
/usr/bin/ln -s /dev/tty0p0 /dev/wwvb1
Location of Time Source
You must always select a time server that is physically close to your network; otherwise,
it may lead to poor network connectivity and delays. You must also consider the
network path that a packet needs to travel, because if a time server is physically close
but takes excessive number of hops to reach, you may experience network delays.
If applications on the network need to be accurate to the millisecond, you must consider
the dispersion measurements and the network service quality. Dispersion is a
measurement of the time server quality and network quality.
NOTE: Dispersion is high if the network is slow or overloaded, irrespective of the
quality of the time server of network.
The time server that returns a quick response to the ping command is the most
appropriate time server.
Figure 4-1 shows the time difference between the NTP client and the NTP time servers
situated physically in different places.
Figure 4-1 Survey of Best Time Servers
The best primary server for the NTP client located in California is the time server
situated in New York because the ping command response time is only 5 millisecond.
The ping command response time for the time server in Australia takes 500
Getting Started with NTP 49