= Miscellaneous Commands and Options
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== Related Links

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== Commands and Options

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// A subset of the tos options is described on the ntp.conf manual page.
// If you change this, be very sure to keep that synchronized.

[[tos]]
+tos+ [+ceiling+ 'ceiling' | +floor+ 'floor' | +maxclock+ 'maxclock' | +maxdist+ 'maxdist' | +minclock+ 'minclock' | +mindist+ 'mindist' | +minsane+ 'minsane' | +orphan+ 'stratum' | +orphanwait+ 'delay']::
  This command alters certain system variables used by the clock
  selection and clustering algorithms. The default values of these
  variables have been carefully optimized for a wide range of network
  speeds and reliability expectations. Very rarely is it necessary to
  change the default values; but, some folks can't resist twisting the
  knobs. It can be used to select the quality and quantity of peers used
  to synchronize the system clock and is most useful in dynamic server
  discovery schemes. The options are as follows:
  +ceiling+ 'ceiling';;
    Specify the maximum stratum (exclusive) for acceptable server
    packets. The default is 16. See the link:discover.html[Automatic
    Server Discovery] page for further details.
  +floor+ 'floor';;
    Specify the minimum stratum (inclusive) for acceptable server
    packets. The default is 1. See the link:discover.html[Automatic
    Server Discovery] page for further details.
  +maxclock+ 'maxclock';;
    Specify the maximum number of servers retained by the server
    discovery schemes. The default is 10, which should typically be changed.
    This should be an odd number (to most effectively outvote
    link:ntpspeak.html[falsetickers]) typically two or three more than
    +minclock+, plus the number of +pool+ entries.  The pool entries
    must be added as +maxclock+, but not +minclock+, also counts the +pool+
    entries themselves.  For example, +tos maxclock 11+ with four +pool+ lines
    would keep 7 associations.  See the link:discover.html[Automatic Server
    Discovery] page for further details.
  +maxdist+ 'maxdistance';;
    Specify the synchronization distance threshold used by the clock
    selection algorithm. The default is 1.5 s. This determines both the
    minimum number of packets to set the system clock and the maximum
    roundtrip delay. It can be decreased to improve reliability or
    increased to synchronize clocks on the Moon or planets.
  +maxdisp+ 'maxdispersion';;
    Specify the maximum dispersion used by the clock synchronization
    algorithm. The default is 16 s.  This is also the dispersion
    assigned to missing data. See RFC 5905 for discussion.
  +minclock+ 'minclock';;
    Specify the number of servers used by the clustering algorithm as
    the minimum to include on the candidate list. The default is 3. This
    is also the number of servers to be averaged by the combining
    algorithm.
  +mindist+ 'mindistance';;
    Specify the minimum distance used by the selection and anticlockhop
    algorithm. Larger values increase the tolerance for outliers;
    smaller values increase the selectivity. The default is .001 s. In
    some cases, such as reference clocks with high jitter and a PPS
    signal, it is useful to increase the value to insure the
    intersection interval is always nonempty.
  +minsane+ 'minsane';;
    Specify the number of servers used by the selection algorithm as the
    minimum to set the system clock. The default is 1 for legacy
    purposes; however, for critical applications the value should be
    somewhat higher (e.g. 3) but less than +minclock+.
  +orphan+ 'stratum';;
    Specify the orphan stratum with default 16. If less than 16 this is
    the stratum assumed by the root servers. See the
    link:orphan.html[Orphan Mode] page for further details.
  +orphanwait+ 'delay';;
    Specify the delay in seconds from the time all sources are lost
    until orphan parent mode is enabled with default 300 s (five
    minutes). During this period, the local clock driver and the modem
    driver are not selectable, unless marked with the +prefer+ keyword.
    This allows time for one or more primary sources to become reachable
    and selectable before using backup sources, and avoids transient use
    of the backup sources at startup.

+dscp+ 'dscp'::
  This command specifies the Differentiated Services Code Point (DSCP)
  value that is used in sent NTP packets. The default value is 46 for
  Expedited Forwarding (EF).

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