Installing and Administering Internet Services

Chapter 7 285
Configuring the Network Time Protocol (NTP)
Getting Started with NTP
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
problems with this option is that many people are protected behind
firewalls and cannot use the public time servers.
There are several public time servers that you can access. HP provides a
public time server. It is located in Cupertino, California. This one is best
to use if you are located in North America. Below are 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 may implement its own hierarchy of NTP time servers,
including stratum-1 servers. If your administrative domain is part of an
enterprise-wide internet, you should check for available NTP resources
in your enterprise. If your administrative domain does not have access to
lower-stratum time servers, there are NTP servers on the Internet that
are willing to provide public time synchronization. (Many stratum-1 and
stratum-2 servers can be used only by permission of the administrator of
the system; you should always check with the administrator before using
an NTP server on the Internet.) A list of primary (stratum 1) and
secondary (stratum 2) public time servers can be found at the following
URL: http://www.eecis.udel.edu/~mills/ntp/servers.htm.
Local Clock Impersonators
If you are behind a firewall, not connected to the internet, and cannot
justify the expense of a radio receiver, you can still have a time server.
You can declare your NTP machine as a time server. This machine can
serve time within a closed domain. This is the least recommendedoption.
Because the server is isolated, it has no way to synchronize to the real
time. Beware, using this option will cause problems if you ever connect
outside of your domain.