described in Section 4 usually picks the peer at the lowest stratum and
minimum synchronization distance among all those available, unless that
peer appears to be a falseticker. The result is that the algorithms all
work to build a minimum-weight spanning tree relative to the primary
reference time servers and thus a hierarchical-master-slave
synchronization subnet.
Primary-Clock Procedure
When a primary reference source such as a radio clock is connected to
the host, it is convenient to incorporate its information into the data
base as if the clock were represented as an ordinary peer. In the
primary-clock procedure the clock is polled once a minute or so and the
returned timecode used to produce a new update for the local clock. When
peer.timer decrements to zero for a primary clock peer, the transmit
procedure is not called; rather, the radio clock is polled, usually
using an ASCII string specified for this purpose. When a valid timecode
is received from the radio clock, it is converted to NTP timestamp
format and the peer variables updated. The value of peer.leap is set
depending on the status of the leap-warning bit in the timecode, if
available, or manually by the operator. The value for peer.peeraddr,
which will become the value of sys.refid when the clock-update procedure
is called, is set to an ASCII string describing the clock type (see
Appendix A).
begin primary-clock-update procedure
<$Eroman peer.leap~<<-~"from"~radio~or~operator>; /* copy
variables */
<$Eroman peer.peeraddr~<<-~ASCII~identifier>;
<$Eroman peer.rec~<<-~radio~timestamp>;
<$Eroman peer.reach~<<-~1>;
call clock-filter(<$Eroman {sys.clock~-~peer.rec,~0,~1~<<
<<~peer.precision}>); /* process sample */
call clock-update; /* update local
clock */
end primary-clock-update procedure;
Initialization Procedures
The initialization procedures are used to set up and initialize the
system, its peers and associations.
Initialization Procedure
The initialization procedure is called upon reboot or restart of the NTP
daemon. The local clock is presumably undefined at reboot; however, in
some equipment an estimate is available from the reboot environment,
such as a battery-backed clock/calendar. The precision variable is
determined by the intrinsic architecture of the local hardware clock.
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