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

Configuring NTP
Getting Started with NTP
Chapter 462
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 highif the network is slow oroverloaded, 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 7-1 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
NTP Time Server in NY
86ms roundtrip PING time
NTP Time Server in Australia
500ms roundtrip PING time
NTP Time Server in CA
5ms roundtrip PING time
Your NTP
Time Client