demobilized.
<$Eroman peer.reach~<<-~roman peer.reach~<< <<~1>;
/* update reachability */
if (<$Eroman peer.reach~=~0> and <$Eroman peer.config~=~0>)
begin
demobilize association;
exit;
endif
If valid data have been shifted into the filter register at least once
during the preceding two poll intervals (low-order bit of peer.reach set
to one), the valid data counter is incremented. After eight such valid
intervals the poll interval is incremented. Otherwise, the valid data
counter and poll interval are both decremented and the clock-filter
procedure called with zero values for offset and delay and
NTP.MAXDISPERSE for dispersion. The clock-select procedure is called to
reselect the synchronization source, if necessary.
if (<$Eroman peer.reach~&~6~!=~0>) /* test
two low-order bits (shifted) */
if (<$Eroman peer.valid~<<~roman NTP.SHIFT>) /* valid
data received */
<$Eroman peer.valid~<<-~roman peer.valid~+~1>;
else <$Eroman peer.hostpoll~<<-~roman
peer.hostpoll~+~1>;
else begin
<$Eroman peer.valid~<<-~roman peer.valid~-~1>; /*
nothing heard */
<$Eroman peer.hostpoll~<<-~roman peer.hostpoll~-~1>);
call clock-filter(0, 0, NTP.MAXDISPERSE);
call clock-select; /* select clock
source */
endif
call poll-update;
end transmit procedure;
Receive Procedure
The receive procedure is executed upon arrival of an NTP message. It
validates the message, interprets the various modes and calls other
procedures to filter the data and select the synchronization source. If
the version number in the packet does not match the current version, the
message may be discarded; however, exceptions may be advised on a case-
by-case basis at times when the version is changed. If the NTP control
messages described in Appendix B are implemented and the packet mode is
6 (control), the control-message procedure is called. The source and
destination Internet addresses and ports in the IP and UDP headers are
matched to the correct peer. If there is no match a new instantiation of
the protocol machine is created and the association mobilized.
begin receive procedure
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