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

Configuring NTP
Getting Started with NTP
Chapter 464
The public stratum-2 servers provides time service for all clients. Also,
their access policies are less restrictive than the stratum-1 servers. The
errors displayed while connecting your machine with the public time
server (or ISP) denotes the quality of the network service.
This makes the distinction between stratum-1 and stratum-2 almost
meaningless for most purposes.
Unlike other applications (such as FTP, DNS, NFS, Sendmail) which can
tolerate huge delays in packet, NTP is sensitive to the network service
quality. Therefore, in addition to the quality of the time servers, you
must ensure that the network is fast and is not overloaded. A minor
delay in the network can be harmful for your time service. Delays shows
up immediately in the dispersion figures.
If you can afford time delays in the time service upto milliseconds, then
pay special attention to the network service quality. If you can afford
time delays in time service upto microseconds, you must abandon the
network time servers and choose a radio clock for each NTP client.
You can evaluate different public time servers from the stratum-2 list.
Following is the stratum-2 listing of the an HP machine which was
provided in the Silicon Valley for public use in North America.
ntp-cup.external.hp.com (192.6.38.127)
Location: Cupertino CA (SF Bay area) 37:20N/122:00W
Synchronization: NTPv3 primary (GPS), HP-UX
Service Area: West Coast USA
Access Policy: open access
Contact: [e-mail]
Note: no need to notify for access, go right ahead!
If you are located in Silicon Valley, you can ping this time server and
notice that the time server is 5 milliseconds.
/usr/sbin/ping ntp-cup.external.hp.com 64 5
PING ntp-cup.external.hp.com: 64 byte packets
64 bytes from 192.6.38.127: icmp_seq=0. time=5. ms
64 bytes from 192.6.38.127: icmp_seq=1. time=4. ms
64 bytes from 192.6.38.127: icmp_seq=2. time=4. ms
64 bytes from 192.6.38.127: icmp_seq=3. time=5. ms
64 bytes from 192.6.38.127: icmp_seq=4. time=5. ms
----ntp-cup.external.hp.com PING Statistics---
5 packets transmitted, 5 packets received, 0% packet loss
round-trip (ms) min/avg/max = 4/4/5