NTP Server NTP Server

What is NTP Server?


What is an NTP Server?

An NTP server is a device or software application that acts as a time server, providing accurate time information to other devices on the network. It receives time signals from reliable sources, such as atomic clocks or GPS satellites, and distributes this time information to other devices using the NTP protocol.

What is NTP Protocol?

The NTP protocol is a hierarchical protocol that allows devices to synchronize their clocks with a reference time source. It operates in a client-server architecture, where the NTP server acts as the time server and the client devices synchronize their clocks with the server. The NTP protocol uses a combination of algorithms and statistical methods to adjust the client clocks to match the reference time source with high accuracy.

Learn More What is NTP? – Network Time Protocol


How Does NTP Server Work?

When a client device wants to synchronize its clock with an NTP server, it sends a request to the server. The server responds with a timestamp indicating the current time. The client device then adjusts its clock based on the time difference between its current time and the server’s timestamp. This process is repeated periodically to ensure continuous time synchronization.

NTP servers can be categorized into two types: primary servers and secondary servers. Primary servers obtain time information directly from reliable sources, such as atomic clocks or GPS satellites. Secondary servers, also known as stratum 2 servers, synchronize their clocks with primary servers. This hierarchical structure ensures that time information is distributed accurately and reliably across the network.

Here’s how it works:

  1. Time Source Selection: NTP servers select their time source, which can be atomic clocks, GPS, or other trusted NTP servers.
  2. Stratum Levels: NTP operates with the concept of stratum levels, with Stratum 0 being the most accurate source (e.g., atomic clocks) and Stratum 15 being the least accurate.
  3. Synchronization: NTP servers exchange time information with each other, adjusting their own clocks to align with the most accurate source.
  4. Client Synchronization: Devices connected to the NTP server, known as clients, periodically sync their time with the NTP server, ensuring accurate time across the network.
  5. Error Correction: NTP employs algorithms to identify and correct time discrepancies, ensuring ongoing synchronization.

NTP Server Pools

NTP server pools are a collection of NTP servers that work together to provide time synchronization services. These pools consist of multiple servers located in different geographic locations. The client devices can connect to any server within the pool, ensuring redundancy and reliability. If one server becomes unavailable, the client devices can automatically switch to another server in the pool.

Using NTP server pools is beneficial for organizations that require high availability and accuracy in time synchronization. By connecting to multiple servers within the pool, the client devices can maintain accurate time even if some servers are offline or experiencing issues.

To harness the power of NTP servers, you can start by specifying the domain name “pool.ntp.org.” This instructs the system to locate the nearest available server, optimizing your network’s timekeeping.

For those who need to diversify their server sources, you can use the prefixes 0, 1, or 2 to specify different pools of servers. Here are some examples:

  • 0.pool.ntp.org
  • 1.pool.ntp.org
  • 2.pool.ntp.org

Global NTP Time Zones

NTP servers are available on almost every continent, offering a rich resource for time synchronization. As of 2017, Europe boasts 2732 servers, North America offers 944, Asia provides 243, and Oceania contributes 109. That’s a grand total of 4106 servers ready to serve your timekeeping needs.

You can further fine-tune your time synchronization by specifying continental zones in the domain name, such as:

  • europe.pool.ntp.org
  • north-america.pool.ntp.org
  • asia.pool.ntp.org

If you require even more granularity, consider specifying specific country zones, like:

Common European Pool Zones:

  • uk.pool.ntp.org (UK)
  • de.pool.ntp.org (Germany – Deutschland)
  • fr.pool.ntp.org (France – Française)
  • es.pool.ntp.org (Spain – España)
  • it.pool.ntp.org (Italy – Repubblica Italiana)
  • nl.pool.ntp.org (Netherlands – Nederland)
  • no.pool.ntp.org (Norway – Norge)
  • pt.pool.ntp.org (Portugal – Portuguesa)
  • se.pool.ntp.org (Sweden – Sverige)

Common North American Pool Zones:

  • us.pool.ntp.org (USA)
  • ca.pool.ntp.org (Canada)

Common Asian Pool Zones:

  • ae.pool.ntp.org (United Arab Emirates)
  • cn.pool.ntp.org (China)
  • in.pool.ntp.org (India)
  • sa.pool.ntp.org (Saudi Arabia)

For each of these zones, you can specify a 0, 1, or 2 prefix if multiple server names are required. For instance:

  • 0.uk.pool.ntp.org
  • 1.uk.pool.ntp.org
  • 2.uk.pool.ntp.org

Google Public NTP Servers

Google, with its worldwide data centers, has introduced its own public NTP servers. These servers employ innovative leap-smearing technology to gracefully insert leap seconds over a period, unlike traditional methods that can cause disruptions. However, it’s crucial to note that using Google’s leap-smearing servers alongside non-leap-smearing servers is not recommended, as it can result in time discrepancies.

Google’s public NTP servers are accessible through the following domain names:

  • time1.google.com
  • time2.google.com
  • time3.google.com
  • time4.google.com

Configuring NTP Clients for Seamless Time Synchronization

For Windows

Configuring Windows to use a public NTP server is straightforward:

  1. Open the Control Panel.
  2. Click the “Date and Time” icon.
  3. Select the “Internet Time” tab.
  4. Click the “Change settings…” button.
  5. Check the box “Synchronize with an Internet time server.”
  6. Enter the domain name or IP address of the desired NTP server next to “Server.”

If you can’t find the “Internet Time” tab, your PC may be part of a domain. In such cases, it will synchronize with the domain controller, which must be configured to synchronize with an NTP server.


For Linux and Unix

Most Linux and Unix systems use the standard NTP distribution (ntpd). Configure the ntpd daemon by editing the /etc/ntp.conf file. Add servers using the server configuration command, as follows:

server 0.uk.pool.ntp.org
server 1.uk.pool.ntp.org
server 2.uk.pool.ntp.org

After making changes, restart the ntpd daemon with the command “sudo service ntp reload.”

Best Practices for NTP Server Usage

To make the most of public NTP servers while maintaining network integrity, follow these best practices:

  • Limit your queries to public NTP servers to reasonable intervals, depending on your system’s requirements.
  • Avoid configuring NTP clients to request time from a server more frequently than once every four seconds, as exceeding this rate may trigger a denial of service (DoS) flag.
  • Opt for local time references whenever possible to minimize network latency.
  • Never hard-code public NTP servers into devices.

Public NTP servers are valuable assets, often managed by volunteers, but they come with no guarantees of availability or accuracy. To ensure a robust and reliable source of time for your organization, consider installing a local time reference.

For those seeking a dependable source of time synchronization, TimeTools, a UK-based manufacturer of NTP servers and precision timing equipment, offers a range of solutions based on GPS and multi-GNSS technology. Their products provide a reliable, accurate, and traceable source of time within your network, ensuring precision and efficiency.

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