This
article describes how to configure Windows to act as an authoritative time
server using NTP (Network Time Protocol).
Computer time synchronisation is highly
important in modern computer networks, precision and time synchronization is
critical in many applications, particularly time sensitive transactions. Just
imagine buying an airline seat only to be told at the airport that the ticket
was sold twice because it was purchased afterwards on a computer that had a
slower clock!
Modern computers do have internal clocks
called Real
Time Clock chips (RTC) that provide time and date information. These
chips are battery backed so that even during power outages,
they can maintain time but personal computers are not designed to be perfect
clocks. Their design has been optimized for mass production and low-cost rather
than maintaining accurate time.
For
many applications, this is can be quite adequate, although,
quite often machines need time to be synchronised with other PC’s
on a network and when computers are out of sync with
each other problems can arise such as sharing network files or in some
environments even fraud!
Microsoft
Windows (2000 and above) has a time synchronisation
utility built into the operating system called Windows
Time (w32time.exe) which can be configured to operate as a network time
server. It can be configured to both synchronise a network using the internal
clock or an external time source.
Note: Microsoft strongly recommends that you configure a time
server with a hardware source rather than from the internet where there is no
authentication.
To configure Windows Time service to use the
internal hardware clock, first check that w32time is located in the system
services list in the registry, to check:
Click Start, Run then type regedit then
click ok.
Locate and then click the following registry entry:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time
It is highly recommended that you back up
the registry as serious problems may occur if you modify the registry
incorrectly, modifications to the registry are done at your own risk.
Note: the following instructions are based
on Windows 2000 other versions of Windows may differ.
To begin configuration for an internal
clock, click on the following subkey:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Parameters
In the right pane, right-click ReliableTimeSource,
then click Modify.
In Edit DWORD Value, type 1 in the Value
Data box, then click OK
Exit Registry Editor
To restart the Windows Time Service click
Start, Run (or alternatively use the Command Prompt facility).
Type: net stop w32time && net start w32time
Then press enter.
To reset the local computers’ time, type the following on all
computers except for the time server which must not be synchronised with itself:
w32tm ?s
To configure the Windows Time service to
use an external time source, click Start, Run and type regedit then click OK.
Locate the following subkey:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Parameters
In the right pane, right-click Type then
click Modify, in edit Value type NTP in the Value data box then click OK.
Now in the right pane, right click
ReliableTimeSource, then click Modify.
In the Edit DWORD Value box, under Value
Data, type 0, then click OK.
Right-click NtpServer in the right pane
then click Modify.
In Edit Value, type the Domain Name System (DNS),
each DNS must be unique.
Now click Ok.
For Windows 2000 Service Pack 4 only, set the time correction
settings to do this locate:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Parameters
In the right pane, right-click
MaxAllowedClockErrInSecs, then Modify in the Edit DWORD Value box, , type a
time in seconds max number of seconds difference between the local clock and
the time received from the NTP server in order to be considered a valid new
time.
Click
OK.
To set the poll intervals locate:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Parameters
In the right pane, right-click Period, then
click Modify.
In the Edit DWORD Value box, under Value
Data, type 24 then OK
Exit Registry Editor
Click Start, then Run then type the following and press Enter:
Net stop w32time && net start w32time
To reset the local computers’ time, type the following on all
computers except for the time server which must not be synchronised with itself:
Network Time Protocol (NTP) is an Internet
protocol used for the transfer of accurate time, providing time information
along so that a precise time can be obtained
To enable the Network Time Protocol;
NTPserver, locate and click:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\TimeProviders\NtpServer\
In the right pane, right-click Enabled, then click Modify.
In the Edit DWord Value box, type 1 under Value data, then click
OK.
Now go back and click on
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Parameters\NtpServer
In the right pane, right-click NtpServer, then Modify, in the Edit
DWORD Value under Value Data type In the right pane, right-click NtpServer,
then Modify, in the Edit DWORD Value under Value Data type the Domain Name System (DNS),
each DNS must be unique and you must append 0×1 to the end of each DNS name
otherwise changes will not take effect.
Now click Ok.
Locate and click the following
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\TimeProviders\NtpClient\SpecialPollInterval
In the right pane, right-click SpecialPollInterval, then click
Modify.
In the Edit DWORD Value box, under Value Data, type the number of
seconds you want for each poll, ie 900 will poll every 15 minutes, then click
OK.
To configure the time correction settings, locate:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\config
In the right pane,
right-click MaxPosPhaseCorrection, then Modify, in the Edit DWORD Value box,
under Base, click Decimal, under Value Data, type a time in seconds such as
3600 (an hour) then click OK.
Now go back and click:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\config
In the right pane, right-click MaxNegPhaseCorrection, then Modify.
In the Edit DWORD box under base, click Decimal, under value data
type the time in seconds you want to poll such as 3600 (polls in one hour)
Exit Registry Editor
Now to restart windows time service, click Start, Run (or
alternatively use the command prompt facility) and type:
net stop w32time && net start w32time
And on each computer, other than the time server , type:
W32tm/ -s
And that’s it your time server should be
now up and running.
About the author
Richard N Williams is a technical author and a
specialist in the telecommunications and network time synchronisation industry
helping to develop dedicated time server products. Please visit us for
more information about a GPS time server or other NTP server
Tags: accurate time, airline seat, clock chips, external time, hardware clock, hardware source, internal clock, internal clocks, internal hardware, microsoft windows 2000, modern computers, network time protocol, network time server, real time clock, sensitive transactions, source note, time source, time synchronization, w32time