Windows 2019 time service - sincronizing to best of three

Occasional Contributor

 

I recently had a problem at a client of mine where one of their DCs syncronized its clock to an ntp server which was incorrect. ( www.ntppool.org/scores/ shows the moment the time was incorrect.... an hour out). It caused problems for a few hours as that affected their building management systems which sync their clocks with the DC. In the morning lights didn't automatically switch on and aircon systems started late due to the time difference

 

The MS documentation says that the service will establish the most accurate clock to use as its source, but doesn't indicate if this occurs on every clock check or just once on service-startup? I always have two ntp sources configured on DCs. In this case the time service seems to have just consulted one and shifted its clock back by a full hour in one jump.

 

My question is, is there any way to get it to query, say, 3 ntp servers and only have it make changes if at least two of the three coincide, thus avoiding the problem of an ntp server returning a wildly incorrect value for a brief time?

 

5 Replies

Looks like the better connection is going to win.

 

The Windows Time service synchronizes time between computers within the hierarchy, with the most accurate reference clocks at the top. If more than one time source is configured on a computer, Windows Time uses NTP algorithms to select the best time source from the configured sources based on the computer's ability to synchronize with that time source.

 

How the Windows Time Service Works | Microsoft Docs

 

 

@Dave Patrick  yeah, it does look like the fastest responder wins. Not exactly the best logic to be following. I haven't found any way to improve the situation either. I'll keep digging and post something here if I find a solution.

I'd think we would always want the better connection to win.

 

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eh?
A node which responds faster but which is wrong is not better than a slower responding one which is correct.

Haven't run into any of them yet but I certainly would not use them again. Many others to choose from.

NIST Internet Time Service

 

also report the broken ones here.

internet-time-service@nist.gov

 

(please don't forget to mark helpful replies)