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# Copyright (c) 2009, 2011, Oracle and/or its affiliates. All rights reserved.

# Since in general, all NTP servers can be NTP clients and vice

# versa, all of the information in the /etc/inet/ntp.client file

# applies to NTP server setup as well. However, a certain kind

# NTP server, called a Stratum 1 server, has one or more devices

# designed to provide very accurate time to the server. These 

# devices are configured using the "server" keyword, just as the

# servers used by the client are, but instead of a hostname or 

# IP address, a format resembling an IP address is used. The first

# two octets of "127.127" are used to designate that this 

# line is referring to a clock and not an network NTP server. 

# The next octet is used to designate which type of device is used. 

# And the last octet is used to specify a unit number if more than

# one is used. Notice that the resulting number looks like the 

# localhost address, it is not the same. The real localhost

# address (127.0.0.1) does not have the second octet of 127 as

# the hardware clock designator does. 

#

# XType Device    RefID          Description

# -------------------------------------------------------

#  1    local     LCL            Undisciplined Local Clock

#  3    pst       WWV            PSTI/Traconex WWV/WWVH Receiver

#  4    wwvb      WWVB           Spectracom WWVB Receiver

#  5    true      TRUE           TrueTime GPS/GOES Receivers

#  6    irig      IRIG           IRIG Audio Decoder

#  7    chu       CHU            Scratchbuilt CHU Receiver

#  8    parse     ----           Generic Reference Clock Driver

#  9    mx4200    GPS            Magnavox MX4200 GPS Receiver

# 10    as2201    GPS            Austron 2201A GPS Receiver

# 11    arbiter   GPS            Arbiter 1088A/B GPS Receiver

# 12    tpro      IRIG           KSI/Odetics TPRO/S IRIG Interface

# 13    leitch    ATOM           Leitch CSD 5300 Master Clock Controller

# 17    datum     DATM           Datum Precision Time System

# 18    acts      ACTS           NIST Automated Computer Time Service

# 19    heath     WWV            Heath WWV/WWVH Receiver

# 20    nmea      GPS            Generic NMEA GPS Receiver

# 21    gpsvme                   GPS VME

# 22    atom      PPS            PPS Clock Discipline

# 26    hpgps     GPS            Hewlett Packard 58503A GPS Receiver

# 27    arc       MSFa           Arcron MSF Receiver

# 28    shm                      Shared memory driver

# 29    palisade                 Palisade

# 30    oncore                   Oncore

# 31    jupiter                  Jupiter GPS

# 32    chronolog                Chronolog

# 33    dumbclock                Dumbclock

# 34    ulink                    Ulink

# 35    pcf                      PCF

# 36    wwv                      WWV Audio

# 37    fg                       FG

# 38    hopfser                  HOPF Serial

# 39    hopfpci                  HOPF PCI

# 40    jjy                      JJY

# 41    tt560                    TT560

# 42    zyfer                    ZYFER

# 43    ripencc                  RIPEENCC

# 44    neoclock4x               NEOCLOCK 4X

# While all the current refclock drivers are configured and compiled,

# not all the actual hardware can be supported on all systems. The

# gpsvme driver can only be expected to work on systems with a VME 

# bus. The WWV audio driver can only be used on systems with audio

# input. 

#  

# In general, refclock type 1, the LOCAL clock is not necessary and

# should not be configured. It should only be used when either there

# is some other process being used to synchronize the clock, such as

# with hardware with vendor provided drivers, or when it is desired

# that a server without access to a real NTP time source needs to 

# act as a multicast or broadcast server. The LOCAL clock should not

# be configured as a "backup" to other external servers. 

# Some of the devices have tuning parameters, called "fudge" factors, 

# that can be set on the server line.  See the ntpd documentation.