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Using NTP on a Windows LAN

I've recently been ask just how my NTP is configured to get the high performance it does on a Windows-based LAN.  Many of the ideas here came from discussions with Dave Hart about how my Windows NTP could be improved given some of settings and controls in recent versions of NTP.

Basic configuration

I'm working with a GPS-driven reference clock (stratum-1 server).  This started life as a FreeBSD PC NTP server based around an old Pentium system I had to hand, went through a phase of running with Windows-based stratum-1 servers, and currently has an Intel Atom-based FreeBSD PC NTP server in addition to the Windows ones.  You can see the current performance here.

Time is served from the stratum-1 server over a LAN to the other PCs, with one desktop PC being served via wireless, as shown on the diagram below:

GPS 18 LVC
 parallel RS-232
    GPS18 LVC
puck on roof
GPS 18x LVC
puck indoors
GPS 18 LVC
 parallel RS-232 
|| || ||        ||
Internet 
backup ==>
sources   
  PC Pixie
 Stratum-1 server 
FreeBSD 8.0
PC Feenix
 Stratum-1 server 
Win XP Home
----------- NTP
peer
---------- PC Stamsund
 Stratum-1 server 
Win-8
     Serial => USB
converter
| | |        ||
Cable modem 
ISP: Virgin Media 
<==>  100Mb/s and 1Gb/s LAN <==> WiFi
| | | |     || |
Internet 
backup ==>
sources 
 PC Bacchus 
NTP client
Win 2000
 PC Alta 
Stratum-1 server
Win-7
    PC Hydra
 NTP client 
Win-7
PC Narvik
NTP client
Win XP Pro
PC Puffin
NTP Client
 Vista Home 
 

NTP configuration files

Please note that only the server/peer part of the configuration files are shown here.  There intention is simply to show how time progresses through this particular system, it's not a tutorial on NTP configuration.  All systems also have Internet servers specified as backup servers, with the servers set to be polled no more than one every 1024 seconds.

Stratum-1 GPS/PPS-synched servers

PC Pixie FreeBSD 8.0 system - stratum-1 PC (192.168.0.3) ntpd 4.2.4p5-a (1)

# The GPS receiver on COM1 at 4800 baud
#
# minpoll 4 = use 16-second sampling
# maxpoll 4 = and don't increase it
# mode 0 = use any statements
# mode 1 = use $GPRMC statements
# flag1 1 = enable PPS processing
# flag3 1 = enable Kernel PPS discipline
#
server 127.127.20.1 mode 0 minpoll 4 maxpoll 4 prefer
fudge 127.127.20.1 flag1 1 flag3 1 refid PPS
#
# Local stratum-1 network servers
# minpoll 5 = use 32-second sampling
# maxpoll 5 = and don't increase it
#
server 192.168.0.2 iburst minpoll 5 maxpoll 5
server 192.168.0.7 iburst minpoll 5 maxpoll 5
#
#	Internet backup servers
#	maxpoll 10 = use 1024s sampling
#	minpoll 10 = and don't decrease it
#
server 0.uk.pool.ntp.org  iburst  minpoll 10  maxpoll 10
server 1.uk.pool.ntp.org  iburst  minpoll 10  maxpoll 10
server 2.uk.pool.ntp.org  iburst  minpoll 10  maxpoll 10

PC Feenix - Windows-XP 32-bit stratum-1 PC (192.168.0.2) - ntpd 4.2.6-o

# ref-clock driver
server 127.127.22.1 minpoll 4 # PPS - serialpps.sys
server 127.127.20.1 minpoll 4 prefer # NMEA serial port
peer 192.168.0.7 maxpoll 6 # Stamsund
#
server  0.uk.pool.ntp.org  minpoll 10
server  1.uk.pool.ntp.org  minpoll 10

PC Stamsund - Windows-7 32-bit stratum-1 PC (192.168.0.7) - ntpd 4.2.6p2-RC5-o

# ref-clock driver
server 127.127.22.1 minpoll 4 # PPS - serialpps.sys
server 127.127.20.1 minpoll 4 prefer # NMEA serial port
peer 192.168.0.2 maxpoll 6 # Feenix
#
server  0.uk.pool.ntp.org  minpoll 10
server  1.uk.pool.ntp.org  minpoll 10

NTP Clients

PC Bacchus- Windows 2000

server 192.168.0.2 iburst maxpoll 5 # Feenix
server 192.168.0.3 iburst maxpoll 5 prefer # Pixie
server 192.168.0.7 iburst maxpoll 5 # Stamsund
#
server  0.uk.pool.ntp.org  minpoll 10
server  1.uk.pool.ntp.org  minpoll 10

PC Gemini - Windows Vista

server 192.168.0.2 iburst maxpoll 5 # Feenix
server 192.168.0.3 iburst maxpoll 5 # Pixie
server 192.168.0.7 iburst maxpoll 5 # Stamsund
#
server  0.uk.pool.ntp.org  minpoll 10
server  1.uk.pool.ntp.org  minpoll 10

PC Hydra - Windows-7 64-bit

server 192.168.0.2 iburst minpoll 5 maxpoll 5 prefer # Feenix
server 192.168.0.3 iburst minpoll 5 maxpoll 5 # Pixie
server 192.168.0.7 iburst minpoll 5 maxpoll 5 # Stamsund
#
server  0.uk.pool.ntp.org  minpoll 10
server  1.uk.pool.ntp.org  minpoll 10

PC Narvik - Windows XP

server 192.168.0.2 iburst maxpoll 5 # Feenix
server 192.168.0.3 iburst maxpoll 5 # Pixie
server 192.168.0.7 iburst maxpoll 5 # Stamsund
#
server  0.uk.pool.ntp.org  minpoll 10
server  1.uk.pool.ntp.org  minpoll 10

 

NTP versions for particular systems

The current NTP version are as follows:
You can see that most systems are running a relatively recent version of NTP, at the time of writing 4.2.4p5-RC5, although that likely to change of you are reading this much after June 2010.  The exceptions are:

PC Feenix

Hasn't been upgraded as it's a 24 x 7 system, and there's no urgent need to upgrade.

PC Hydra & PC Puffin

These PCs are running Windows Vista, which appears to have a much better performance with NTP 4.2.4 than with later versions.  This has been logged with the NTP team but is as yet unresolved.  Because of the earlier version of NTP, it is necessary to specify both minpoll and maxpoll in the server lines to ensure that the servers are polled at 32-second intervals.

PC Pixie

This is the FreeBSD 8.0 system and is running the version of NTP which came with the OS download.  It works very well, so I see no need to change.  Because of the earlier version of NTP, it is necessary to specify both minpoll and maxpoll in the server lines to ensure that the Internet servers are polled no more frequently than once every 1024 seconds.

 
Copyright © David Taylor, Edinburgh   Last modified: 2015 Jan 18 at 09:32