Microsoft

Mastering the Windows Time Service

If you manage Windows 2000 and Active

Directory, you should know that the Win2K Time Service is key to

ensuring that the Kerberos security protocol and other Windows 2000

services work correctly. All machines in a Windows 2000 forest need to

have the correct time. This article will explain the details and show

you how to configure and troubleshoot the Time Service.How does time synchronization work?The

Windows 2000 Time Service (w32time.dll) is installed by default on all

Windows 2000 computers. The Time Service starts automatically on

computers that are part of a domain and can be started manually on

other machines.When a computer joined to a domain is booted,

the Time Service is enabled. As the Net Logon service looks for a

domain controller (DC) and is authenticated, the computer sends a

request to get the time and waits until the DC responds. Once it

receives the time from the DC, the Time Service will perform the

following:
  • If the local clock is behind the current DC time, the Time Service changes the local time immediately.
  • If the local clock is faster than three minutes, the Time Service changes the local time immediately.
  • If the local clock is less than three minutes fast, the Time Service slows the clock down to bring it into synchronization.
The

Time Service then attempts synchronization every 45 minutes until all

clocks are synchronized three times. Once properly synchronized, the

Time Service will resynchronize time every eight hours. If you have

Active Directory (AD) configured, all other machines in your forest

will synchronize to your time server, as shown in Figure A.

Before configuring the Time Service, you need

to become familiar with some of the command-line tools you’ll use to

work with it. We’ll start with the Net Time command.Configuring Net TimeIn order to properly configure Net Time, you need to know the syntax. If you open a command prompt and type net time /?, you’ll see the syntax shown in Figure B.

Table A breaks down the list of

options available for the Net Time command. You’ll use this command to

have one of your domain controllers synchronize to an external

authority and then provide time information to the rest of the domain.

Table A

Net Time options

Description

Net Time

Displays the time of your time server

Net Time \\computername

Displays the computer name time

Net Time /DOMAIN:domainname

Displays the time on a DC domain name

Net Time /domain/set

Sets computer time to match time on Domain Controller

Net Time /RTSDOMAIN:domainname

Displays the time on a time server in the domain name

Net Time /querysntp

Displays the SNTP source for the time server

Net Time /setsntp:ntpserver

Sets the SNTP source for the time server

Net Time /setsntp

Clears the SNTP source for the time server

Net Time options

To display the time of a Windows 2000 machine, follow these steps:
  1. From the Start menu, select Programs | Accessories | Command Prompt.
  2. Type a command such as net time \\kiev, as we’ve done in Figure C.
To set the external Simple Network Time Protocol (SNTP) time server:
  1. From the Start menu, select Programs | Accessories | Command Prompt.
  2. Type a command such as net time /setsntp:ntp2.usno.navy.mil, as shown in Figure D.
Here are the steps for querying the SNTP name:
  1. From the Start menu, select Programs | Accessories | Command Prompt.
  2. Type a command such as net time /querysntp, as shown in Figure E.

Troubleshooting the Windows 2000 Time Service

The

w32tm tool is used to troubleshoot any problems that might occur during

or after the configuration of the Time Service. When troubleshooting,

make sure to stop the Time Service before using this tool. Not doing so

will cause a port error in the Event Viewer.

Furthermore, in

order for the Time Service to work properly, you will need to have port

123 opened on your firewall. Otherwise, you can’t synchronize to an

external time source. To access the syntax of the troubleshooting tool,

type w32tm /? from a command prompt.

Table B shows a detailed list of command options available for the W32tm command.

Table B

W32TM parameter

Description

-tz

Print the local time zone information and exit

-s computer

Force the given computer (or local computer if none is given) to resynchronize, then exit

-adj

Set the computer's system clock frequency to the last frequency determined during synchronization, then exit

-adjoff

Set the computer's system clock frequency to the system default, then exit

-source

Choose a

synchronization source, then exit. Note that a source is chosen before

each synchronization, so this is useful only in showing that a source

could be found. Remember to use -v to see the output.

-once

Do only one

synchronization, then exit. Otherwise, run continuously as a client,

synchronizing the local clock until ctrl-c is pressed.

The following options can be used in conjunction with the above:

-test

Prevent the time on the local system from actually being modified

-v

Print out a verbose

description of what the program is doing. This is usually needed since

otherwise the program produces no output. The exceptions are -s and -tz.

-p

-P set the server port

-period

set the sync period just as in the registry. That is:

0=once a day

65535=once every 2 days

65534=once every 3 days

65533=once every week (7 days)

65532=once every 45 min (3/day)

65531=once every 45 min until we get one good sync, then once every day

W32tm command options

To test the synchronization of a computer:

From the Start menu, select Programs | Accessories | Command Prompt.
  1. Type net stop w32time.
  2. Type w32tm –once –test –v (Figure F).

You will have to stop and start the service every time you make a

change to the Time Service. You must have Administrator rights to stop

and start services.

To stop the W32 Time Service:

  1. From the Start menu, select Programs | Accessories | Command Prompt.
  2. Type net stop w32time.

To start the W32 Time Service:

  1. From the Start menu, select Programs | Accessories | Command Prompt.
  2. Type net start w32time.

To stop and start the service using the Windows 2000 graphical user interface (GUI):

  1. From the Start menu, select Programs | Administrative Tools | Computer Management.
  2. Select Services And Applications.
  3. Select Services and highlight Windows Time.
  4. Right-click to stop or start the service.
I have provided you with a brief look at the

Windows Time Service. For more information, you can also reference

the following resources:

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