098-00720-000 Revision B – April, 2016
SyncServer 600 Series User’s Guide
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Chapter 4
Navigation Windows
Table 4-4. NTPd SysInfo Parameter Descriptions
Parameter
Description
System Peer
The IP address of the clock source. The source is selected by the NTP daemon
that is most likely to provide the best timing information based on: stratum,
distance, dispersion and confidence interval. The address of the local
SyncServer Hardware Clock can be viewed in the hardware reference clock
section of the NTP associations page.
System Peer
Mode
The relationship of the SyncServer to a system peer, usually a "client".
Depending the configuration, the mode can be:
Client
: A host operating in this mode sends periodic messages regardless of
the reachability state or stratum of its peer. By operating in this mode the
host, usually a LAN workstation, announces its willingness to be
synchronized by, but not to synchronize the peer.
Symmetric Active
: A host operating in this mode sends periodic messages
regardless of the reachability state or stratum of its peer. By operating in this
mode the host announces its willingness to synchronize and be synchronized
by the peer.
Symmetric Passive
: This type of association is ordinarily created upon
arrival of a message from a peer operating in the symmetric active mode and
persists only as long as the peer is reachable and operating at a stratum level
less than or equal to the host; otherwise, the association is dissolved.
However, the association will always persist until at least one message has
been sent in reply. By operating in this mode the host announces its
willingness to synchronize and be synchronized by the peer.
A host operating in client mode (a workstation, for example) occasionally sends
an NTP message to a host operating in server mode (the SyncServer), perhaps
right after rebooting and at periodic intervals thereafter. The server responds by
simply interchanging addresses and ports, filling in the required time information
and returning the message to the client. Servers need retain no state information
between client requests, while clients are free to manage the intervals between
sending NTP messages to suit local conditions.
In the symmetric modes, the client/server distinction (almost) disappears.
Symmetric passive mode is intended for use by time servers operating near the
root nodes (lowest stratum) of the synchronization subnet and with a relatively
large number of peers on an intermittent basis. In this mode the identity of the
peer need not be known in advance, since the association with its state variables
is created only when an NTP message arrives. Furthermore, the state storage
can be reused when the peer becomes unreachable or is operating at a higher
stratum level and thus ineligible as a synchronization source.
Symmetric active mode is intended for use by time servers operating near the
end nodes (highest stratum) of the synchronization subnet. Reliable time service
can usually be maintained with two peers at the next lower stratum level and one
peer at the same stratum level, so the rate of ongoing polls is usually not
significant, even when connectivity is lost and error messages are being returned
for every poll.
