Spectracom NetClock 9489 - Page 122

other higher stratum servers. If a peer loses all reference clocks or fails, the other peers continue
to provide time to other clients on the network.
NTP Servers at the same Stratum level
If NetClock 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, NetClock
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, NetClock 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 NetClock 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 reference, NetClock will report to
the network (via the NTP time stamps) that it is one less Stratum than its selected reference NTP
Server.
E X A M P L E :
If NetClock is configured to receive time from one or more Stratum1 NTP Servers, with no other
higher priority input references available, NetClock will report to the network that it is a Stratum2
Server.
In order for NetClock to use other NTP servers as a valid time reference to synchronize the Sys
tem Time, the input Reference Priority Setup table must be configured to allow NTP as an avail
able reference. For more information on the input Reference Priority table, refer to
"Configuring Input Reference Priorities" on page163.
Holdover
If NetClock 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), NetClock will then go into the Holdover mode. It will remain in Hol
dover mode until any enabled and 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 ref
erence becomes available before the Holdover period expires, Time Sync will be lost and
shortly thereafter, NTP will report to the network that it is now at Stratum15. A status of
Stratum15 will cause the network to ignore NetClock as an NTP time reference.
For more information about Holdover, see "Holdover Mode" on page210.
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CHAPTER 2 • NetClock User Reference Guide Rev. 16
2.15 Configuring NTP