NTP协议全称网络时间协议(Network Time Procotol)。它的目的是在国际互联网上传递统一、标准的时间。具体的实现方案是在网络上指定若干时钟源网站,为用户提供授时服务,并且这些网站间应该能够相互比对,提高准确度。
NTP 最早是由美国Delaware大学的Mills教授设计实现的,从1982件最初提出到现在已发展了将近20年,2001年最新的NTPv4精确度已经达到了200毫秒。对于实际应用,又有确保秒级精度的SNTP(简单的网络时间协议)。
NTP是一个跨越广域网或局域网的复杂的同步时间协议,它通常可获得毫秒级的精度。RFC2030[Mills 1996]描述了SNTP(Simple Network Time Protocol),目的是为了那些不需要完整NTP实现复杂性的主机,它是NTP的一个子集。通常让局域网上的若干台主机通过因特网与其他的NTP主机同步时钟,接着再向局域网内其他客户端提供时间同步服务。
NTP协 议是OSI参考模型的高层协议,符合UDP传输协议格式,拥有专用端口123。
随着时间的推移, 计算机的时钟会倾向于漂移。 网络时间协议 (NTP) 是一种确保您的时钟保持准确的方法。它为路由器、交换机、工作站和服务器之间提供了一种时间同步的机制。所以NTP Server经常应用于一些有时间同步要求的IT系统环境中。
一、服务端设置
Mac OS X Server似乎默认就有了,只说一下Linux下如何设置。
在Ubuntu Linux中应用NTP Server非常方便:
1. 安装
sudo apt-get install ntp
2. 配置
配置文件是/etc/ntp.conf
a. 找到server一项,添加你喜欢的Time Server
server time.asia.apple.com iburst dynamic
server time.asia.apple.com iburst dynamic
b. 设置权限,我的所有restrict条目如下
- restrict -4 default kod notrap nomodify nopeer noquery
- restrict -6 default kod notrap nomodify nopeer noquery
-
- # Local users may interrogate the ntp server more closely.
- restrict 127.0.0.1 www.5a520.cn
- restrict ::1
-
- # Clients from this (example!) subnet have unlimited access, but only if
- # cryptographically authenticated.
- #restrict 192.168.123.0 mask 255.255.255.0 notrust
- restrict 192.168.0.0 mask 255.255.255.0
restrict -4 default kod notrap nomodify nopeer noquery
restrict -6 default kod notrap nomodify nopeer noquery
# Local users may interrogate the ntp server more closely.
restrict 127.0.0.1
restrict ::1
# Clients from this (example!) subnet have unlimited access, but only if
# cryptographically authenticated.
#restrict 192.168.123.0 mask 255.255.255.0 notrust
restrict 192.168.0.0 mask 255.255.255.0
3. 重启ntp服务器
/etc/init.d/ntp restart
4. 查看服务器是否工作正常
在服务器运行
ntpq -p
二、工作站同步
好了,测试一下吧,假设你的新服务器IP地址为192.168.0.7。在客户端运行如下命令:
ntpdate -u 192.168.0.7
同步成功后,将会显示如下:
6 Mar 15:44:24 ntpdate[9921]: adjust time server 192.168.0.7 offset -0.007277 sec
三、交换机同步
Cisco IOS
- ciscorouter> enable
- password: *********
- ciscorouter# config t
- ciscorouter(config)# ntp update-calendar
- ciscorouter(config)# ntp server 192.168.0.4
- ciscorouter(config)# ntp server 192.168.0.7
- ciscorouter(config)# exit
- ciscorouter# wr mem
ciscorouter> enable
password: *********
ciscorouter# config t
ciscorouter(config)# ntp update-calendar
ciscorouter(config)# ntp server 192.168.0.4
ciscorouter(config)# ntp server 192.168.0.7
ciscorouter(config)# exit
ciscorouter# wr mem
Dell 6248
- dell6248-corner>en
- dell6248-corner#configure
- dell6248-corner(config)#sntp server 192.168.0.7
- dell6248-corner(config)#
dell6248-corner>en
dell6248-corner#configure
dell6248-corner(config)#sntp server 192.168.0.7
dell6248-corner(config)#
四、一些常见的时间服务器
210.72.145.44 ── (国家授时中心服务器IP地址)
133.100.11.8 ── 日本 福冈大学
time-a.nist.gov 129.6.15.28 ── NIST, Gaithersburg, Maryland
time-b.nist.gov 129.6.15.29 ── NIST, Gaithersburg, Maryland
time-a.timefreq.bldrdoc.gov 132.163.4.101 ── NIST, Boulder, Colorado
time-b.timefreq.bldrdoc.gov 132.163.4.102 ── NIST, Boulder, Colorado
time-c.timefreq.bldrdoc.gov 132.163.4.103 ── NIST, Boulder, Colorado
utcnist.colorado.edu 128.138.140.44 ── University of Colorado, Boulder
time.nist.gov 192.43.244.18 ── NCAR, Boulder, Colorado
time-nw.nist.gov 131.107.1.10 ── Microsoft, Redmond, Washington
nist1.symmetricom.com 69.25.96.13 ── Symmetricom, San Jose, California
nist1-dc.glassey.com 216.200.93.8 ── Abovenet, Virginia
nist1-ny.glassey.com 208.184.49.9 ── Abovenet, New York City
nist1-sj.glassey.com 207.126.98.204 ── Abovenet, San Jose, California
nist1.aol-ca.truetime.com 207.200.81.113 ── TrueTime, AOL facility, Sunnyvale, California
nist1.aol-va.truetime.com 64.236.96.53 ── TrueTime, AOL facility, Virginia
五、使用Python脚本来获取时间
- #!/usr/bin/python
- from socket import *
- import struct,os,time,sys
-
- # Script to set Linux hardware clock (/usr/sbin/hwclock) from an NTP
- # time server. Run as "setclock.py" to simply print the time from
- # the NTP server. Run as "setclock.py --set" to set the Linux
- # hardware clock (as the super user, of course).
-
- # Based on Simon Foster's simple SNTP client from ASPN Python cookbook.
- # Adapted by Paul Rubin; this script lives at:
- # http:
-
- time_server = ('time.apple.com', 123)
- # time.apple.com is a stratum 2 time server. (123 is the SNTP port number).
- # More servers info can be found at
- #
- # http:
- #
- # Note it's considered antisocial to use a stratum 1 server (like NIST)
- # for purposes like this which don't need extreme accuracy (i.e. syncing
- # your own big NTP network). See www.ntp.org for more info.
- #
- # You could also use time.windows.com (Microsoft server) which syncs
- # all Windows XP machines everywhere, so it can presumably handle lots
- # of clients.
-
- # number of seconds between NTP epoch (1900) and Unix epoch (1970).
- TIME1970 = 2208988800L # Thanks to F.Lundh
-
- client = socket( AF_INET, SOCK_DGRAM )
- data = '\x1b' + 47 * '\0'
- client.sendto(data, time_server)
- data, address = client.recvfrom( 1024 )
- if data:
- print 'Response received from', address,'\n'
- t = struct.unpack( '!12I', data )[10]
- if t == 0:
- raise 'invalid response'
- ct = time.ctime(t - TIME1970)
- print 'Current time = %s\n' % ct
- if len(sys.argv) > 1 and sys.argv[1] == "--set":
- os.system("/usr/sbin/hwclock --set '--date=%s'"% ct)
- else:
- raise 'no data returned'
#!/usr/bin/python
from socket import *
import struct,os,time,sys
# Script to set Linux hardware clock (/usr/sbin/hwclock) from an NTP
# time server. Run as "setclock.py" to simply print the time from
# the NTP server. Run as "setclock.py --set" to set the Linux
# hardware clock (as the super user, of course).
# Based on Simon Foster's simple SNTP client from ASPN Python cookbook.
# Adapted by Paul Rubin; this script lives at:
# http://www.nightsong.com/phr/python/setclock.py
time_server = ('time.apple.com', 123)
# time.apple.com is a stratum 2 time server. (123 is the SNTP port number).
# More servers info can be found at
#
# http://www.eecis.udel.edu/~mills/ntp/servers.htm
#
# Note it's considered antisocial to use a stratum 1 server (like NIST)
# for purposes like this which don't need extreme accuracy (i.e. syncing
# your own big NTP network). See www.ntp.org for more info.
#
# You could also use time.windows.com (Microsoft server) which syncs
# all Windows XP machines everywhere, so it can presumably handle lots
# of clients.
# number of seconds between NTP epoch (1900) and Unix epoch (1970).
TIME1970 = 2208988800L # Thanks to F.Lundh
client = socket( AF_INET, SOCK_DGRAM )
data = '\x1b' + 47 * '\0'
client.sendto(data, time_server)
data, address = client.recvfrom( 1024 )
if data:
print 'Response received from', address,'\n'
t = struct.unpack( '!12I', data )[10]
if t == 0:
raise 'invalid response'
ct = time.ctime(t - TIME1970)
print 'Current time = %s\n' % ct
if len(sys.argv) > 1 and sys.argv[1] == "--set":
os.system("/usr/sbin/hwclock --set '--date=%s'"% ct)
else:
raise 'no data returned'
上面这个脚本原址在这里,
http://www.nightsong.com/phr/python/setclock.py,
http://www.bt285.cn,
http://www.guihua.org。使用方式如下:
$ python setclock.py
Response received from ('17.151.16.23', 123)
Current time = Fri Mar 6 16:03:19 2009