HP-UX Internet Services Administrator's Guide (August 2003)

Configuring NTP
Getting Started with NTP
Chapter 460
Local Clock Impersonators
You can use a local clock impersonator in either of the following
instances:
• If you are behind a firewall.
• If you are not connected to the Internet.
• If you cannot afford a radio receiver.
You can declare your NTP machine as a time server, and this machine
can serve time within a closed domain. Because this time server is
isolated, it does not synchronize with the real time.
IMPORTANT Using this option may cause problems if you are always connected
outside your domain.
To set up the local clock impersonator, add the following entry to the
/etc/ntp.conf file:
server 127.127.1.1 minpoll 3 maxpoll 4
Radio Receiver
The radio receiver is the most accurate and expensive time distribution
mechanism. Radio receiver provides a stable time and is not affected by
network delays, congestion, or outrages. Some of the popular radio
receiver methods are: GPS (Global Positioning System), WWV
(Terrestrial North America), and DCF77 (Terrestrial Europe).
You must consider the cabling options when you select the radio receiver.
Antenna cables are very expensive and RS232 cabling has a limited
range.
The official HP supported GPS receivers are HP58503 driver#26 and
Trimble Palisade driver#29. The only supported WWVB receiver is
Spectracom Netclock/2 driver#4. DCF77 (AM and FM) signals radiate
from Frankfurt Germany. DCF77 receivers are not officially supported by
HP.
Setting up an HP58503A GPS Receiver
The following steps describe how to set up an HP58503A GPS: