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

Available Time Sources
The most common time distribution mechanisms from which you can draw time are:
• Public time server (phone or modem) via the Internet
• Local clock impersonators
• Radio receiver – Terrestrial and satellite broadcast
Public Time Server
You can connect to public time servers via the Internet free of charge for a limited time.
Public time servers also provide dial-up access through a modem. This is the cheapest
and most popular method. One of the main disadvantage of this option is that all the
networks cannot use the public time server because they are protected behind firewalls.
Many other time servers are available that you can access. HP provides a public time
server, which is located in Cupertino, California. You can use this time server if you
are located in North America. The following lists the details for this time server:
ntp-cup.external.hp.com (192.6.38.127)
Location: Cupertino, CA (SF Bay Area) 37:20N/122:00W
Synchronization: NTP3 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!
NOTE: An enterprise can implement its own hierarchy of NTP time servers, including
the stratum-1 servers. If your administrative domain is part of an enterprise-wide
Internet, you must verify for available NTP resources in your enterprise. If your
administrative domain does not have access to lower-stratum time servers, NTP servers
on the Internet are available that provide public time synchronization. You can use
stratum-1 and stratum-2 servers only with the permission of the administrator; you
must always check with the administrator before using an NTP server on the Internet.
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.
Getting Started with NTP 47