Technical data

Configuring and Managing NTP
12.1 Key Concepts
Indicate client mode with the server declaration in the configuration file. For
example:
server 18.72.0.3
• Broadcast mode
This mode indicates that the local server will send periodic broadcast
messages to a client population at the broadcast/multicast address specified.
This specification normally applies to the local server operating as a sender.
Indicate this mode with a broadcast declaration in the configuration file. For
example:
broadcast 18.72.0.255
12.2 NTP Service Startup and Shutdown
The NTP service can be shut down and started independently of TCP/IP Services.
The following files are provided:
• SYS$STARTUP:TCPIP$NTP_STARTUP.COM allows you to start up the NTP
service independently.
• SYS$STARTUP:TCPIP$NTP_SHUTDOWN.COM allows you to shut down the
NTP service independently.
To preserve site-specific parameter settings and commands, create the following
files. These files are not overwritten when you reinstall TCP/IP Services:
• SYS$STARTUP:TCPIP$NTP_SYSTARTUP.COM can be used as a repository
for site-specific definitions and parameters to be invoked when the NTP
service is started.
• SYS$STARTUP:TCPIP$NTP_SYSHUTDOWN.COM can be used as a
repository for site-specific definitions and parameters to be invoked when the
NTP service is shut down.
12.3 Configuring Your NTP Host
The NTP configuration file TCPIP$NTP.CONF contains a list of hosts your system
will use for time synchronization. Before configuring your host, you must:
1. Select time sources.
2. Obtain the IP addresses or host names of the time sources.
3. Obtain the version number of NTP that the hosts are running.
To ensure reliable synchronization, select multiple time sources that you are
certain provide accurate time and are synchronized to an Internet time server.
To minimize common points of failure, avoid synchronizing:
• The local host to another peer at the same stratum unless the latter is
receiving time from a lower stratum source to which the local host cannot
connect
• More than one host in a particular administrative domain to the same time
server outside that domain
To simplify configuration file maintenance, avoid configuring peer associations
with higher stratum servers.
12–4 Configuring and Managing NTP