What ntp server can i use

Evaluating our options on a ridiculously short timeframe, Packet stood out as an interesting choice, though we were a little apprehensive at first if their setup would be too unusual compared to more familiar options. After a quick chat with some of the friendly staff at Packet, we were off to the races to see if we could get everything migrated in less than a week of nights and weekends. Working with the Packet system has been fascinating and extremely productive.

Despite having done this sort of work for several decades, it was a surprise how mixing familiar capabilities, APIs and abstractions opened new ways for quickly building and managing powerful, reliable and scalable infrastructure. How do I join pool. Information for vendors The mailing lists Additional links.

An NTP server that acquires its time directly from a reference clock occupies a stratum that is one level higher than that of the reference clock. Resources that acquire time from the NTP server are two steps away from the reference clock, and therefore occupy a stratum that is two higher than the most accurate time source, and so on.

As a computer's stratum number increases, the time on its system clock may become less accurate. Therefore, the stratum level of any computer is an indicator of how closely that computer is synchronized with the most accurate time source.

When the W32Time Manager receives time samples, it uses special algorithms in NTP to determine which of the time samples is the most appropriate for use. The time service also uses another set of algorithms to determine which of the configured time sources is the most accurate. When the time service has determined which time sample is best, based on the above criteria, it adjusts the local clock rate to allow it to converge toward the correct time.

If the time difference between the local clock and the selected accurate time sample also called the time skew is too large to correct by adjusting the local clock rate, the time service sets the local clock to the correct time. This adjustment of clock rate or direct clock time change is known as clock discipline. The Windows Time Service Manager is responsible for initiating the action of the NTP time providers included with the operating system.

The Windows Time Service Manager controls all functions of the Windows Time service and the coalescing of all time samples. In addition to providing information about the current system state, such as the current time source or the last time the system clock was updated, the Windows Time Service Manager is also responsible for creating events in the event log. These time samples are then passed to the Windows Time Service Manager, which collects all the samples and passes them to the clock discipline subcomponent.

The clock discipline subcomponent applies the NTP algorithms which results in the selection of the best time sample. The clock discipline subcomponent adjusts the time of the system clock to the most accurate time by either adjusting the clock rate or directly changing the time.

If a computer has been designated as a time server, it can send the time on to any computer requesting time synchronization at any point in this process. Time protocols determine how closely two computers' clocks are synchronized. A time protocol is responsible for determining the best available time information and converging the clocks to ensure that a consistent time is maintained on separate systems.

NTP is an Internet time protocol that includes the discipline algorithms necessary for synchronizing clocks. NTP is a fault-tolerant, highly scalable time protocol and is the protocol used most often for synchronizing computer clocks by using a designated time reference. NTP time synchronization takes place over a period of time and involves the transfer of NTP packets over a network.

NTP packets contain time stamps that include a time sample from both the client and the server participating in time synchronization. NTP relies on a reference clock to define the most accurate time to be used and synchronizes all clocks on a network to that reference clock.

UTC is independent of time zones and enables NTP to be used anywhere in the world regardless of time zone settings. NTP includes two algorithms, a clock-filtering algorithm and a clock-selection algorithm, to assist the Windows Time service in determining the best time sample. The clock-filtering algorithm is designed to sift through time samples that are received from queried time sources and determine the best time samples from each source. The clock-selection algorithm then determines the most accurate time server on the network.

This information is then passed to the clock discipline algorithm, which uses the information gathered to correct the local clock of the computer, while compensating for errors due to network latency and computer clock inaccuracy.

The NTP algorithms are most accurate under conditions of light-to-moderate network and server loads. As with any algorithm that takes network transit time into account, NTP algorithms might perform poorly under conditions of extreme network congestion.

The Windows Time service is a complete time synchronization package that can support a variety of hardware devices and time protocols. To enable this support, the service uses pluggable time providers. A time provider is responsible for either obtaining accurate time stamps from the network or from hardware or for providing those time stamps to other computers over the network. The NTP provider is the standard time provider included with the operating system. NtpServer output provider. This is a time server that responds to client time requests on the network.

NtpClient input provider. This is a time client that obtains time information from another source, either a hardware device or an NTP server, and can return time samples that are useful for synchronizing the local clock.

Although the actual operations of these two providers are closely related, they appear independent to the time service. Starting with Windows Server, when a Windows computer is connected to a network, it is configured as an NTP client.

Also, computers running the Windows Time service only attempt to synchronize time with a domain controller or a manually specified time source by default. These are the preferred time providers because they are automatically available, secure sources of time. Within an AD DS forest, the Windows Time service relies on standard domain security features to enforce the authentication of time data.

The security of NTP packets that are sent between a domain member computer and a local domain controller that is acting as a time server is based on shared key authentication. The Windows Time service uses the computer's Kerberos session key to create authenticated signatures on NTP packets that are sent across the network.

Public time servers are often maintained by volunteers. They provide no guarantee of availability or accuracy. You use them at your own risk. Also, many NTP authentication and security mechanisms cannot be used with public time servers, which may leave your systems open to abuse. If your organisation requires an accurate and reliable source of time, you should seriously consider installing a local time reference.

Important: TimeTools cannot be held responsible for the availability or operation of the public NTP servers listed on this page. TimeTools Limited. DY5 3LG. United Kingdom. You can also use the prefix 0, 1 or 2 to specify different pools of servers, if multiple server names are required: 0. If you wish, you can specify continental zones in the domain name, as follows: europe. For instance: 0. Google Public Network Time Servers Google have recently revealed that they have implemented public NTP with load balancers and atomic clocks in their world-wide data centres.

Googles public NTP servers use the following domain names: time1. Ideally, NTP servers would be located in three geographically disparate locations. This group of primary masters would be the source for time for the enterprise. They would be considered hidden masters because they would only provide services to the secondary stratum servers. This configuration would allow those servers to provide time to collocated secondary masters that are actually providing services to an organization.

The primary masters remain hidden and are only accessed by the NTP infrastructure that provides services elsewhere. That supply chain should allow you to provide accurate time across your organization and have multiple sources corroborating an accurate time source. Locations that have more devices needing to have their time synchronized can add additional Stratum 2 or Stratum 3 servers and have them rely on the secondary masters as well as each other to further distribute the load on a system and providing services to a larger group of NTP clients.

By setting up an internal NTP service on the latest revision of stable code and standardizing its use, the viability of time-based network attacks or processes that are dependent on time are harder to co-opt. The identification of the order of events in a compromise becomes easier because the times in the logs can now be systems of record.

For law enforcement and other investigative agencies, accurate NTP services can be very constructive in evaluating evidence and sequencing a chain of events. As attacks become more sophisticated, our team of network analysts at CERT increasingly finds Internet-facing services that aren't well deployed within a network.

As Mark Langston wrote in his recent post on DNS Best Practices , many of these services make up the foundation for the security and operation of internal and external network applications. This is the latest in a series of blog posts offering best practices on these foundational structures to help government agencies and other enterprises address hidden sources of vulnerabilities within their networks.

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If you do decide to configure you own, please consider the following best practices: Standardize to UTC time. Within an enterprise, standardize all systems to coordinated universal time UTC. Standardizing to UTC simplifies log correlation within the organization and with external parties no matter what time zone the device being synchronized is located in.