Network Time Protocol (NTP)

1
Network Time Protocol (NTP)

• ??? ???????? ????????
• ??????????????????????????????????
• ????????????????? ????????????????????
• u4606308_at_cm.edu

2
Overview

• Introduction
• Stratum
• ntpd on Linux
• Dimension 4 on Windows
• ntp on router

3
Introduction

• ???????? David L. Mills ???? University of
  Delaware ????????? 1985
• ???? protocol ????????????????????????????????????
  ????? packet-switched
• ??????????????? UDP ?? port 123
• ??????????????????????????????????????????????

4
Why ntp ?

• Transaction Processing.
• Network fault isolation, reporting and restores.
• Network monitoring, measurement and control.
• Distributed multimedia stream synchronization.
• Research experiment setup.
• Security mechanisms.

5
ntp packet
6
Global Positioning System

• ???????? ????????????? ??????????
  ??????????????????????????????????????????????????
  ?????
• ????????????? ????????????????????????
  ????????????????????????????????????
• ???????????????????????????? ?????????????????????
  ??????????????????? atomic clock
  ???????????????????????????????
• ????????????? ??????? ???????? GPS
  ????????????????????????????????????????? 340
  ??????????

7
Atomic Clock

• ???????? National Institute of Standards and
  Technology (NIST)
• ?????????????????? ??????????????????? 1 ????????
  1 ??????
• ?????????? Quantum Mechanics ?????????????????????
  ?? Atomic resonator
• ??????????? SI ??? 1 ?????? ??????????????????????
  ?????????????????? 133 9,192,631,770 ?????
• http//en.wikipedia.org/wiki/Atomic_clock

8
Atomic Clock
9
Stratum

• ????????????????????????????
• ?????????????????????? GPS ?????????? stratum 1
  ???????????????????????
• ?????????????????????? stratum 1 ???????????????
  stratum 2, stratum 3, stratum 4,5,6 ???????? ?
• ??????????????????????????????????????????????????
  ? stratum 1,2,3 ??? 4 ????????????????????????????
  ??? ANSI

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Stratum
11
Stratum
12
Stratum

• Stratum 1 ???? slip 1 ????? ??? 72 ???
  ????????????????????? 1 ?????? ??? 1,557 ??
• Stratum 2 ???? slip 1 ????? ??? 7 ???
  ????????????????????? 1 ?????? ??? 153 ?? 117 ???
• Stratum 3 ???? slip 1 ????? ??? 6 ????
  ????????????????????? 1 ?????? ??? 33 ??? 8
  ???????
• Stratum 4 ????????????????????????????
  ?????????????????????????????????

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Stratum
Stratum 0
Stratum 1
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ntpdate

• ???????????? Linux ????????????????????? protocol
  ntp
• ??????
• ntpdate 192.168.1.1
• ??????????????????????????????????????????? ????
  ????? crontab
• ?????????????????????????????????
• ntpd ??????

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Network Time Protocol Daemon (ntpd)

• ???? daemon ??????????????????????????????????????
  ?
• ??????????????????????????????????????????????????
  ????????????????????
• ???????????????????????????????????????? ntp
• ??????????????????????????????????????????????????
  ???????????????????????????????????????????????

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?????????? ntpd

• ????????????????????? ntpd ???
• /etc/ntp.conf
• ntpd ???? daemon ?????????????????????? restart
  ????????????????
• /etc/rc.d/init.d/ntpd restart
• ?????? ntpd ???????????????????????????????????
• /sbin/chkconfig ntpd on

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ntp.conf

• ???????? server ??????????????

????????????? ip ??? server ?????????????????????
????
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ntp.conf

• ???????????????????????????????????

????? ip ??? network ????????????????????????????
?
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?????????????????? ntpd

• /usr/bin/ntpstat

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?????????????????? ntpd

• /usr/sbin/ntpq -p
• /usr/sbin/ntpdc -p

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?????????????????? ntpd

• /usr/sbin/ntptrace

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??????? ntp client ?? windows

• Dimension 4 http//www.thinkman.com
• ???? freeware ??????????Install
  ???????????????????

23
??????? ntp client ?? windows

• ????? ntp server ????????????????

??????????
24
??????? ntp client ?? windows

• ??????????????????? ?

ip ???? ??????? server
???????(optional)
protocol ????? SNTP
????????(optional)
25
??????? ntp client ?? windows

• ????????????

????? server
?????????? server
??????????????
?????????????????
26
??????? ntp client ?? windows

• ???????? history ???????????????

27
??????? ntp client ?? windows

• ???????? history ???????????????

28
??????? ntp client ?? windows

• ???????? history ???????????????

29
??????? ntp client ?? windows

• ???????? history ???????????????

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ntp on Cisco router
31
ntp on Cisco router
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ntp on Cisco router
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• http//www.cisco.com
• http//www.thaicert.nectec.or.th
• http//www.cis.udel.edu/mills/ntp/html/index.html
  
• http//www.pool.ntp.org
• http//www.ntp-servers.com
• http//ntp.isc.org/bin/view/Servers/WebHome

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• Q A