If you’ve worked on a domain, you know how important it is to have all of your servers and clients running at exactly the same time. When they get out of sync things get ugly.
You can use the w32tm command-line tool to diagnose problems occurring with Windows Time.
From an elevated command prompt type:
w32tm /query /source
This command will display the time source that the computer is currently using for synchronization. If the machine is a part of an Active Directory domain, it should be getting it’s time from a Domain Controller.
If you want to force the server to sync with its time source, the command is:
w32tm /resync
Looking at the screenshot above you can see that there are a number of line items returned which may not make immediate sense to you so we will go through each one of them:
What is Leap Indicator:
Think of “leap”, the way you think about leap years. This field is used to keep Coordinated Universal Time (UTC) and the International Atomic Time (TAI) in sync. Leap seconds are occasionally added or subtracted because of slight variations in Earth’s rotation speed. The actual adjustment of the system clock for leap seconds is handled by the Windows Time service.
The “Leap Indicator” in the output of the w32tm /query /source command is a field that indicates whether a leap second should be inserted or deleted in the last minute of the current month.
Here are the possible values for the Leap Indicator:
0: No warning, which means no leap second will be inserted or deleted.
1: Last minute of the day has 61 seconds, which means a leap second will be inserted.
2: Last minute of the day has 59 seconds, which means a leap second will be deleted.
3: Alarm condition (clock not synchronized), which means the system time could not be synchronized with the network time protocol (NTP) server.
What is Stratum:
Stratum” refers to the level in the hierarchy of time sources.
Stratum 0: These are high-precision timekeeping devices such as atomic clocks, GPS, or other radio clocks
Stratum 1: These are computers that are directly connected to Stratum 0 devices. They are the primary network time servers
Stratum 2: These are computers that are synced to Stratum 1 servers over a network
Stratum 3: These are computers that are synced to Stratum 2 servers, and so on
What is Root Delay:
“Root Delay” and “Root Dispersion” are parameters that provide information about the quality of the time synchronization.
Root Delay is the round-trip packet delay from a client to a stratum 1 server. It gives a crude estimate of the worst-case time transfer error between a client, or higher stratum server acting as a client, and a stratum 1 server. It’s essentially the network latency. The root delay is also used in clock steering algorithms to identify false tickers, that is servers with bad time or one’s that are sitting on the other side of a highly asymmetric network path.
What is Root Dispersion:
Root Dispersion tells you how much error is added due to other factors. One factor is the error introduced by a client due to the inaccuracy of its clock frequency. Using NTP the higher stratum can set its clock to the lower stratum server, but if its clock frequency is off, then an error is introduced.
If you really need to go deep on this, root dispersion is calculated this way:
Dispersion = DR×(t4–t1)+timestamping errors
- DR is the drift rate of client clocks time and is equal to the fractional frequency error
- t1 and t4 are timestamps gathered during an NTP request and response
- timestamping errors term includes things like the errors due to the finite resolution of the clock, and delays in reading the clock when fetching a timestamp.
What is ReferenceID:
The “ReferenceID” in the output of the w32tm /query /source command is a field that provides information about the time source.
If the time source is an NTP server, the ReferenceID is typically the IP address of the NTP server.
If the time source is the local system clock, the ReferenceID is usually “LOCL”.
This field helps you identify the specific time source that your system is using for synchronization. It’s particularly useful when you’re troubleshooting time synchronization issues or when you want to verify that your system is using the correct time source.
What is Last Successful Sync Time:
As the name suggests, this is the last time that there was a successful synchronization of the time.
What is Source:
This tells you where the computer is getting its time synchronized from. If the computer is in an Active Directory that really should be a domain controller as it is in our screen shot above.
What is Poll Interval:
The “Poll Interval” in the output of the w32tm /query /source command refers to the frequency at which the Windows Time service (W32Time) synchronizes the system clock with the time source.
The poll interval is expressed as a power of two in seconds. For example, a poll interval of 6 corresponds to 2^6 or 64 seconds. This means that the system clock would be synchronized with the time source every 64 seconds.
It’s important to note that the actual poll interval can vary based on network conditions and system load. The Windows Time service dynamically adjusts the poll interval to optimize the trade-off between time accuracy and network traffic.
If you want to manually configure the poll interval, you can do so by modifying the SpecialPollInterval registry key. However, please be aware that incorrect modifications to the Windows Registry can cause serious problems, so this should only be done by an experienced user or system administrator.
Can VMware Tools Override Time Sync of a Member Server?
Yes, VMware Tools can override the time synchronization of a member server, even if it’s coming from a Domain Controller.
VMware Tools has its own time synchronization feature, which can be enabled or disabled. If enabled, it can cause the guest operating system’s time to sync with the host machine, potentially overriding the time sync from the Domain Controller.
However, in an Active Directory environment, it’s generally recommended to let the Domain Controller manage time synchronization, as it’s crucial for services like Kerberos authentication.
If you want to disable the time synchronization feature of VMware Tools, you can add the following lines to your virtual machine’s advanced configuration options1:
tools.syncTime = “0”
time.synchronize.continue = “0”
time.synchronize.restore = “0”
time.synchronize.resume.disk = “0”
time.synchronize.shrink = “0”
time.synchronize.tools.startup = “0”
time.synchronize.tools.enable = “0”
This will effectively disable VMware Tools’ time synchronization, allowing the Domain Controller to manage time sync.
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