w32time service provides time for Windows. Since Windows XP NTP (Network Time Protocol) is supported. Prior to that it was only SNTP (Simple NTP).
Non domain joined computers (including servers) use SNTP.
Any Windows machine can be set up to sync time in one of four ways: (1) no syncing! (2) sync from specified NTP servers (3) sync via domain hierarchy (i.e. members sync from a DC in the domain; DCs sync from PDC of the parent domain/ forest root domain) (4) use either of the above (i.e. NTP and domain hierarchy). Default mechanism on domain joined computers is domain hierarchy (the setting is called
NT5DS). Stand-alone machines have the default as
NTP servers (the setting is called NTP; the default server is time.windows.com though you can change it (and probably recommended that you change it?)).
For machines that are off and on the domain – e.g. laptops – it is better to set their time sync mechanism as any. They needn’t always have contact with the DC to sync time.
When specifying NTP time servers you also specify flags. Check this post for an explanation of the flags. There are four possible flags: 0x01
SpecialInterval; 0x02 UseAsFallbackOnly; 0x04
UseAsFallbackOnlymeans the server is only used if the others are unavailable. Check out this post for an example of this.
SpecialIntervallets you change how often the NTP server is polled. By default the interval is determined by Windows based on the quality of time samples, but you can use the above flag and set a registry key
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\TimeProviders\NtpClient\SpecialPollIntervalto change the polling interval.
- I am not sure what the other two flags do. The
Clientflag seems to be a commonly used one. Some posts/ articles use it, others don’t. The default time.windows.com setting uses this flag as well as the
p.s. To turn on w32tm debugging check out this link.