Domain Time Sync – AVD Test

Time synchronization is one of the most important dependencies of Windows. A time protocol is responsible for determining the best available time information and converging the clocks to ensure that a consistent time is maintained across systems. By default, Windows supports a tolerance of plus or minus five minutes for clocks. If the time variance exceeds this setting, clients will be unable to authenticate and in the case of domain controllers, replication will not occur. To avoid this, Windows implements a time synchronization system based on Network Time Protocol (NTP).

NTP is a fault-tolerant, highly scalable time protocol and it is used for synchronizing computer clocks by using a designated reference clock. A reference clock is some device or machinery that spits out the current time. The special thing about these things is accuracy. Reference clocks must be accurately following some time standard. NTP will compute some additional statistical values based on the current time reported by the reference clock, which will describe the quality of time it sees. Among these values are: offset (or phase), jitter (or dispersion), frequency error, and stability. Thus each NTP server will maintain an estimate of the quality of its reference clocks and of itself.

This test reports the time difference between the reference clock and that of the target environment, and thus helps assess the quality of time seen by the Azure virtual desktop. With the help of this test, you can also easily determine whether the reference time changed recently.

Target of the test : An Azure Virtual Desktop

Agent deploying the test : An internal agent.

Outputs of the test : One set of results for the Session Host chosen

Configurable parameters for the test

Parameters	Description
Test Period	How often should the test be executed.
Host	The host for which the test is to be configured.
Port	The default port is NULL.
NTP Server	By default, this parameter is set to none indicating that the default designated reference clock would be used to synchronize the server clock. In Microsoft Windows, the Windows Time service automatically synchronizes your computer's internal clock with other clocks in the network. The time source for this synchronization varies, depending on whether the computer is joined to an Active Directory domain or to a workgroup. If the computers belong to an Active Directory domain, the Windows Time service configures itself automatically by using the Windows Time service that is available on domain controllers. The Windows Time service configures a domain controller in its domain as a reliable time source and synchronizes itself periodically with this source. This is why, if the Windows server being monitored is part of a domain, you need not disturb the default setting none of this parameter. When the computers are part of a workgroup on the other hand, you must manually configure the time synchronization settings. You must identify a computer as a locally reliable time source by configuring the Windows Time service on that computer to use a known accurate time source, either by using special hardware or by using a time source that is available on the Internet. You can configure all other workgroup computers manually to synchronize their time with this local time source. This is why, if the Windows server being monitored is part of a workgroup, you will have to manually specify the hostname or the IP address of the computer that should be used as the local time source, against this parameter.

Measurements made by the test

Measurement	Description	Measurement Unit	Interpretation
NTP offset	Indicates the time difference between the local clock and the designated reference clock.	Secs	For a tiny offset, NTP will adjust the local clock; for small and larger offsets, NTP will reject the reference time for a while. In the latter case, the operating system's clock will continue with the last corrections effective while the new reference time is being rejected. After some time, small offsets (significantly less than a second) will be slewed (adjusted slowly), while larger offsets will cause the clock to be stepped (set anew). Huge offsets are rejected, and NTP will terminate itself, believing something very strange must have happened.