RE: NTP server ?
"Petro, Erno" <Erno.Petro@Compaq.com>
Szia Tibi,
Az alabbi infot a "DIGITAL TPC/IP Services for OpenVMS management" cimu
alkotasbol olloztam ki.
ovms_clock_sec
10.1.3 How the OpenVMS System Maintains the System Clock
index_x_438The OpenVMS system clock is maintained as a software timer with a
resolution of 100 nanoseconds, updated at 10 millisecond intervals. A clock
update is triggered when a register, loaded with a predefined value, has
decremented to zero. Upon reaching zero, an interrupt is triggered that
reloads the register, thus repeating the process.
The smaller the value loaded into this register, the more quickly it reaches
zero and triggers an update. The clock runs more quickly in such an
instance. A larger value means more time between updates; therefore, the
clock runs more slowly. ntp_how
10.1.4 How NTP Makes Adjustments to System Time
index_x_439index_x_440Once NTP has selected a suitable synchronization
source, NTP compares the source's time with that of the local clock. If NTP
determines that the local clock is running ahead of or behind the
synchronization source, NTP uses a general drift mechanism to slow down or
speed up the clock as needed. NTP accomplishes this by issuing a series of
new ticks. For example, if NTP detects that the local clock is drifting
ahead by +0.1884338 second, it issues a series of new ticks in an effort to
reduce the difference between the synchronization source and the local
clock.
NTP maintains a record of the resets it makes along with informational
messages in the NTP log file, TCPIP$NTP.LOG. See Section
<file:///E:/axpdocmar00/axpdocmar00_2/NETWORK/TCPIP50A/MANAGE/6526profile_01
6.html#ntp_log_sec> 10.5 for more details about event logging and help in
interpreting an NTP log file.
state_sec
10.2.2 Valid Configuration Statements and Options
index_x_451The following are valid NTP configuration statements:
* peer address [key ID] [version number] [prefer] [minpoll interval]
[maxpoll interval]
* server address [key ID] [version number] [prefer ]
* broadcast address [key ID] [version number] [ttl nn]
The following describes the options to the peer, server, and broadcast
commands.
key ID For all packets sent to the address, includes authentication
fields encrypted using the specified key identifier, an unsigned 32-bit
integer. The default is no encryption.
version number Specifies the version number to be used for outgoing
NTP packets. Version 1, 2, and 3 are the choices. The default is 3.
prefer Marks the server as preferred. This host will be chosen for
synchronization among a set of correctly operating hosts.
ttl nn Used only with broadcast mode. It specifies the time-to-live
to use on multicast packets.
minpoll interval Specifies the minimum polling interval for
NTP messages, in seconds to the power of two. The allowable range is 4 (16
s) to 14 (16384s) inclusive. Not applicable to reference clocks. The default
is 6 (64s).
maxpoll interval Specifies the maximum polling interval, in
seconds, for NTP messages. The allowable range is 4 (16 s) to 14 (16384s)
inclusive. The default is 10 (1024s). (Does not apply to reference clocks.)
* broadcastclient address
Directs the local server to listen for broadcast messages at the broadcast
address of the local network. The default address is the subnet address with
the host file bits set to ones. Upon hearing a broadcast message for the
first time, the local server measures the nominal network delay using a
brief client/server exchange with the remote server, then enters the
broadcastclient mode, in which it listens for and synchronizes to succeeding
broadcast messages. Note, to avoid accidental or malicious disruption in
this mode, both the local and remote servers should operate using
authentication and the same trusted key and key identifier.
* multicastclient address
Directs the local server to listen for multicast messages at the group
address of the global network. This command operates like the
broadcastclient command, but uses IP multicasting.
* driftfile file_name location
Specifies the name of the file used to record the frequency offset of the
local clock oscillator. If the file exists, it is read at startup to set the
initial frequency offset, then updated hourly with the current frequency
computed by the NTP server.
If the file does not exist or the driftfile command is not specified in the
configuration file, the initial frequency offset is assumed zero. If the
file does not exist but the driftfile keyword is specified without a
parameter, the default, SYS$SPECIFIC:[TCPIP$NTP]TCPIP$NTP.DRIFT, will be
used.
In these cases, it may take some hours for the frequency to
stabilize and the residual timing errors to subside.
The drift file TCPIP$NTP.DRIFT consists of a single floating-point number,
which records the frequency of the offset measured in parts-per-million
(PPM).
* enable auth | bclient | monitor | pll | stats
disable auth | bclient | monitor | pll | stats
These commands provide a way to enable or disable various server options.
auth Enables synchronization with unconfigured peers only if the
peer has been correctly authenticated using a trusted key and key
identifier. The default is enable.
bclient Enables the server to listen for messages from
broadcast or multicast servers. The default is disable.
monitor Enables the monitoring facility. The default is
enable.
pll Enables the server to adjust its local clock by means of
NTP. If disabled, the local clock free-runs at its intrinsic time and
frequency offset. This flag is useful in case the local clock is controlled
by some other device or protocol and NTP is used only to provide
synchronization to other clients. In this case, the local clock driver is
used. The default is enable.
stats Enables the statistics facility. The default is enable.
ntpconf_sec
10.2.3 Sample NTP Configuration File
index_x_452A sample of the NTP configuration template follows:
# Copyright (c) Digital Equipment Corporation, 1998
#
# Example NTP Configuration File
#
# Rename this template to TCPIP$NTP.CONF.
#
# See the DIGITAL TCP/IP Services for OpenVMS Management manual for
# additional commands and detailed instructions on using this
# configuration file.
#
# The Network Time Protocol (NTP) provides synchronized timekeeping
# among a set of distributed time servers and clients. The local
# OpenVMS host maintains an NTP configuration file, TCPIP$NTP.CONF, of
# participating peers. TCPIP$NTP.CONF is maintained in the
# SYS$SPECIFIC:[TCPIP$NTP] directory.
#
# As the system manager populating this file, you must determine the
# peer hosts with which the local hosts should negotiate and
# synchronize. Include at least one (but preferably three)
# hosts that you are certain have the following characteristics:
#
# * provide accurate time
# * synchronize to Internet Time Servers (if they are not
# themselves Internet Time Servers)
#
# The NTP configuration file is not dynamic, and therefore requires
# restarting NTP after being edited to make the changes take effect.
# However, you can make run-time configuration requests interactively
# using the TCPIP$NTPDC utility.
# Your NTP configuration file should always include the following
# driftfile entry. The driftfile is the name of the file that stores
# the clock drift (also known as frequency error) of the system clock.
driftfile SYS$SPECIFIC:[TCPIP$NTP]TCPIP$NTP.DRIFT
# Sample peer entries follow. Replace them with your own list of
# hosts and identify the appropriate association mode. If you
# specify multiple hosts, NTP can choose the best source with which to
# synchronize. This also provides reliability in case one of the hosts
# becomes unavailable.
# Identify each peer with a DNS host name or with an IP address
# in dotted-quad notation.
peer 18.72.0.3
peer 130.43.2.2
peer 16.1.0.22
peer parrot
# The following commands let you use NTP with
# another time service such as DTSS. If enabled (by removing #),
# NTP will not set the system clock.
# server 127.127.1.0 prefer
# fudge 127.127.1.0 stratum 0
bottom_015
_____
Emil
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