Safran VersaSync User Manual page 133

If VersaSync is configured to obtain time from other NTP Servers at the same
Stratum level (i.e., NTP Peers) but is currently using a different input reference as
its selected reference, VersaSync will report to the network (via the NTP time
stamps) that it is a Stratum 1 time server. Should, however, all input references
except the other NTP server(s) become unavailable, VersaSync will then drop to
a Stratum 2 time server (with System Time being derived from the NTP time pack-
ets being received from the other NTP Peers.
NTP Servers at a higher Stratum level
If VersaSync is configured to obtain time from another NTP Server at a higher
Stratum level (i.e., NTP Servers), and it is using that NTP Server as its selected ref-
erence, VersaSync will report to the network (via the NTP time stamps) that it is
one less Stratum than its selected reference NTP Server.
In order for VersaSync to use other NTP servers as a valid time reference to syn-
chronize the System Time, the input Reference Priority Setup table must be con-
figured to allow NTP as an available reference. For more information on the input
Reference Priority table, refer to
page 173.
Holdover
If VersaSync is synchronized to another NTP Server or reference, and that server
or reference subsequently loses sync or becomes unavailable (with no other
higher priority input references being present and valid), VersaSync will then go
into the
valid input reference becomes available again, or until the Holdover period
expires, whichever occurs first.
During Holdover mode, NTP will remain at the same Stratum level it was before
entering the Holdover mode and can continue to be the reference to the network.
However, if no input reference becomes available before the Holdover period
expires, Time Sync will be lost and shortly thereafter, NTP will report to the net-
work that it is now at Stratum 15. A status of Stratum 15 will cause the network to
ignore VersaSync as an NTP time reference.
For more information about Holdover, see
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E X A M P L E :
If VersaSync is configured to receive time from one or more Stratum 1 NTP Servers,
with no other higher priority input references available, VersaSync will report to the net-
work that it is a Stratum 2 Server.
Holdover mode. It will remain in Holdover mode until any enabled and
2.8 Configuring Network Settings
"Configuring Input Reference Priorities" on
"Holdover Mode" on page 219.
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