State
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... operate in a symmetric mode, in which servers and clients are
indistinguishable, yet maintain a small amount of state information,
or in client/server mode, in which servers need maintain no state ...
... state information,
or in client/server mode, in which servers need maintain no state
other than that contained in the client request. A lightweight
...
... reachability and
variable polling rate mechanisms, is included only to manage the
state information and reduce resource requirements. Since only a
single NTP ...
... This section consists of a formal definition of the Network Time
Protocol, including its data formats, entities, state variables,
events and event-processing procedures. The specification model is
based on the implementation model illustrated in Figure 2.1, but it
...
... State Variables and Parameters ...
...
Following is a tabular summary of the various state variables and
parameters used by the protocol. They are separated into classes of
...
... port number of
the local host. They are included among the state variables to
support multi-homing.
...
...
Following is a list of state variables used by the peer management
and measurement functions. There is one set of these variables for
...
... filter and selection algorithms suggested in Section 4 are
used, the following state variables are defined. There is one set of
these variables for every peer operating in client mode or symmetric
...
... information and returning the message to the client. Servers then
need retain no state information between client requests. Clients
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... messages and each determines that the other is reachable, an
association is formed. One or both peers must be in active state;
that is, sending messages to the other regardless of reachability
...
... that is, sending messages to the other regardless of reachability
status. A peer not in active state is in passive state. If a peer
...
... status. A peer not in active state is in passive state. If a peer
operating in passive state ...
... state. If a peer
operating in passive state discovers that the other peer is no longer
reachable, it ceases sending messages and reclaims the storage and
timer ...
... association. A peer operating in client
mode is always in active state, while a peer operating in server mode
is always in passive state ...
... bit. Then an NTP message is constructed and sent to the
peer. If operating in active state or in passive state and
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... peer. If operating in active state or in passive state and
peer.reach is nonzero (reachable), the peer.timer is reinitialized
...
... NTP.MINPOLL) .
If operating in active state and peer.reach is zero (unreachable),
the peer variables are updated as follows:
...
... result in a new clock source (sys.peer). If sys.peer points to the
peer data structure with the just-updated estimates, the state
variables of that peer are used to update the system state ...