![]() Ambient environmental conditions affect clock accuracy and a mobile device can move from one ambient condition to the next which may interfere with its ability to keep time accurately. Additionally, clocks in mobile devices may not be very accurate to begin with. Battery powered devices also have certain power modes which stop all applications from running, which interferes with W32time's ability to discipline the clock and maintain accurate time. These settings will consume more battery power than expected and can interfere with power saving modes available in Windows for such devices. As per our recommendation, keeping accurate time requires the clock to be disciplined once a second, which correlates to the Clock Update Frequency. For example, the path could change due to changes in network topology, or packets being routed through devices that have different interface speeds.įor battery powered devices, both mobile and portable, you must consider different strategies. If the path the NTP packet takes going to the server takes a different amount of time to return, the accuracy is affected. NTP uses calculations to adjust the time that assume the network path is symmetrical. Symmetrical NTP communication - It is critical that the connection for NTP communication is symmetrical.In some cases, firmware updates might be needed for accurate time. However, if the client computer clock's oscillator is not stable, then more fluctuations in between adjustments can occur and the algorithms Windows uses to condition the clock don't work accurately. It does not step the time changes, but rather slows or speeds up the local clock so that you approach the accurate time quickly and stay accurate between NTP requests. NTP uses multiple samples from potentially multiple NTP servers to condition and discipline your local computers clock. Stable client clock - A stable client clocks assures that the natural drift of the oscillator is containable.If the time reference is not properly maintained, or operated by a potentially malicious party, you could expose your domain to time based attacks. It also must be accessible because disruptions in the connection will interfere with time synchronization. The same goes for time, and if your source clock isn't stable, then the entire chain of synchronized clocks is affected and magnified at each stage. The analogy goes, if you have two boats on the water, and you are trying to measure the altitude of one compared to the other, your accuracy is best if the source boat is very stable and not moving. This usually means installing a GPS device or pointing to a Stratum 1 source, taking #3 into account. Solid Source Clock - The source clock in your domain needs to be stable and accurate.In every case for accurate time, there are three critical factors: To see the stratum of a client, use w32tm /query /status. Also, W32time only accepts time from stratum 15 or below. While a lower stratum often indicates a more accurate clock, it is possible to find discrepancies. Stratum 2 talk to stratum 1 servers, stratum 3 to stratum 2 and so on. Stratum 1 is reserved for the highest-level clock, and stratum 0 is reserved for the hardware assumed to be accurate and has little or no delay associated with it. Stratum is a concept used in both the NTP and Hyper-V providers, and its value indicates the clocks location in the hierarchy. ![]() Since Hyper-V guests will have at least two Windows Time providers to choose from, the host time and NTP, you might see different behaviors with either Domain or Standalone when running as a guest. For 1 ms accuracy, you can't depend on a remote time sources. Network traffic loads and asymmetrical network paths may reduce the accuracy of the time synchronization. Like all remotely located time references, network outages, may prevent synchronization. This name is resolved by your DNS Server, which should point to a Microsoft owned resource. Standalone machines are configured to use by default. See the [Specify a Local Reliable Time Service Using GTIMESERV section below. The hierarchy resolves to the PDC or a DC in the root forest, or a DC with the GTIMESERV domain flag, which denotes a Good Time Server for the domain. In a domain, there is a hierarchical layer of time strata, whereby each DC points to a parent DC with a more accurate time stratum. Domain members synchronize with a master clock determined by the domain hierarchy and a scoring system. Domain Hierarchyĭomain and Standalone configurations work differently.ĭomain members use a secure NTP protocol, which uses authentication to ensure the security and authenticity of the time reference. The windows time provider plugin model is documented on TechNet.
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