OSF DCE Administration Guide--Core Components

OSF DCE Administration Guide—Core Components
setting the time. The user sets the inaccuracy based on local experience with NTP.
The null provider may be useful for sites that already have a radio clock that is
managed by NTP. Make the node with the radio clock a DTS server and use the null
time-provider.
26.1.1 Getting the Time from Local NTP Time Sources
Run the DTS server on a node that is running an NTP clock driver with a clock and the
null time-provider. Specify the inaccuracy in a manner that is consistent with the time
source; for instance, a radio clock. Other DTS servers will take the time from this
source. In this case, since the system is connected to a time source, it is an NTP Stratum
1 server.
Observe the rules and advisories that follow:
• Rule—If this is the only local time source (radio clock) in the subnetwork, ensure
that no other DTS node gives the time to NTP. If, however, there are other local time
sources, this restriction does not apply.
• Rule—Do not run the null time-provider if there is no local time source.
• Advisory—Use a very small poll rate, about 1 second.
• Advisory—Since NTP makes the adjtime() system call, be aware that the local node
will occasionally have an unspecified inaccuracy.
Figure 26-1 shows how a DTS server/client with a local time source takes time from an
NTP Stratum 1 server.
Figure 26-1. Local Time Source
NTP
server
client server
NTP
client
stratum 3 stratum 2
DTS
DTS
server
stratum 1
NTP
server
DTS
dts_null_provider.c
26.1.2 Getting the Time from Remote NTP Time Sources
Run the DTS server with the NTP time-provider (dts_ntp_provider.c) on a node with
access to an NTP server. Specify the inaccuracy in a manner that is consistent with local
NTP experience.
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