PyNet Labs- Network Automation Specialists

What is NTP – Network Time Protocol?

Last Updated : June 27, 2023
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Let’s uncover what is NTP by exploring its feature and functionality. Time synchronization is of utmost importance for modern computer networks, as various network management, security, planning, and debugging techniques require accurate time measurement for determining the timing of events. The task of safeguarding precise time can be difficult due to the tendency of a computer’s clock to deviate by a few seconds or minutes on a daily basis.

Each computer is equipped with a hardware clock that is responsible for keeping track of the current time. However, its accuracy is compromised by the phenomenon of clock frequency drift. The Network Time Protocol (NTP) is a popular protocol utilized for time synchronization. Numerous individuals employ NTP software to synchronize their devices with NTP servers to resolve issues related to time synchronization. It is utilized by various network devices such as servers, switches, routers, and computers to synchronize time across the network.

Before getting into more details, let’s first understand “What is NTP“.

What is NTP (Network Time Protocol)?

As the most used protocol for synchronizing clocks over networks, NTP is ideal for distributed computing environments. One of the most critical needs of every organization is tracking time accurately. It’s a technique for synchronizing clocks that is utilized to solve the problem of pinpoint accuracy. It’s a protocol for keeping computers in various parts of the world over the internet in sync with each other’s clocks.

NTP is more than just a protocol; it’s a whole system that allows precise synchronization of time over public and private networks. The main goal of NTP is to have all of the network computers within a millisecond or two of Coordinated Universal Time. It’s really precise and reliable.

Now we have a basic understanding of What is NTP, now let’s further understand the working of NTP.

How NTP works?

The Network Time Protocol consists mainly of three components:

  • The NTP software program is commonly referred to as a daemon in Unix systems and a service in Windows operating systems.
  • The protocol responsible for the exchange of time values between servers and clients.
  • collection of algorithms that manipulate time values in order to either accelerate or decelerate the system clock.
Working of NTP

An NTP client refers to a system that aims to align its clock with that of a server, while an NTP server refers to the system that sends back a response in terms of true time.

The size of a timestamp is 64 bits, with 32 bits allocated for the number of seconds and an additional 32 bits allocated for the fraction of seconds. When a client initiates a packet, as mentioned above, the client sends the request with the timestamp.

So, it means we consider our time as the wrong time and server time as the true time. Due to an incorrect time setting, the client must adjust their timing based on the response provided by the NTP server.

Now let’s understand with an example –

  • Let’s assume a client sends the request at the wrong time, i.e. (assuming T1 = 50 sec)
  • The server gets the request, let’s assume at T2 = 80 sec because of some internet connectivity issues.
  • The server might get busy at the time of sending back the accurate time, so it sends back the request to the client at a time T3; let’s say T3 = 90 sec.
  • The client receives the time from the server; let’s assume at T4 = 70 sec.
  • Now, Delay can be calculated as follows:

(T4-T1) – (T3-T2) = (70 – 50) – (90 – 80) = 10 seconds.

  • At this point, the client has estimated the elapsed time it took for the server’s answer to reach the client as:

10 / 2 = 5 seconds (We divided by 2 as it is a two-way communication).

  • Now, the client adds 5 seconds to the time when the server sends the accurate time, i.e., T3 (90 + 5 = 95).
  • Now to calculate the delay, the client now knows he has to subtract the time at which he gets the response from the server and the time at which the server sends the response, i.e., T3 – T4 = 95 – 70 = 25.
  • Hence 25 is the delay that the client faces. So, the client will add 25 seconds to its clock.

That’s how NTP is calculated manually.

To understand Network Time Protocol better, one should also have knowledge of Stratum Levels. Let’s understand what Stratum levels are.

What are Stratum Levels?

Stratum levels are the separation degrees of UTC that follow a strict hierarchy.

Various Stratum Levels
  • Stratum 0: Stratum 0 is Earth’s primary source time reference, which obtains accurate UTC through a special satellite network. Because of this, clocks in stratum 0 are considered to be the standard by which all other clocks are measured. The GPS Clock and the Atomic Clock are two such examples.
  • Stratum 1: Stratum 1 devices and systems must be connected directly to Stratum 0 for an accurate time. It is also known as the main server.
  • Stratum 2: The second layer of time servers relies on Stratum 1 for accurate time.
  • Stratum 3: These computers are connected to servers in Stratum 2, where they may get accurate time.

Accuracy in determining the current time decreases as one moves down the NTP hierarchy. There are a total of 16 levels in the NTP hierarchy, with Level 16 denoting a device that is not synced.

Features of NTP

Here are some of the most fundamental features of the network time protocol:

  • NTP offers a reference clock that serves as the standard against which all other synchronization activities are measured. This time or clock serves as the standard by which all others are organized. Since its inception, this function has been served by the coordinated universal time (UTC), which is widely recognized as the global time reference.
  • NTP is a technology for synchronization that will automatically seek reliable time servers. Error accumulation in synchronization may be mitigated by combining data from many sources. Network time protocols attempt to identify and discard time sources that consistently provide wildly off values.
  • In other words, NTP can be easily scalable. There might be a large number of reference clocks in each synchronization network. Additionally, each network node may broadcast time information in both directions (point-to-point) or in a single direction only (hierarchical).
  • It’s safe to rely on NTP. By picking the most suitable candidate for synchronization, it is possible to get results with a precision of up to one millisecond.
  • When a network’s connection not working properly, Network Time Protocol may help by using past data to correct the time or account for a time difference.

These are some of the features of Network Time Protocol.

Frequently Asked Questions

Q1 – What is the NTP protocol?

NTP stands for Network time protocol used to synchronize different machines’ time. By providing a standardized method for clock synchronization, NTP enables seamless coordination and consistency across networked systems.

Q2 – Is NTP TCP or UDP protocol?

NTP uses UDP protocol and uses port 123 for communication via messages between the client and the server. NTP utilizes UDP as its transport protocol due to its low latency and simplicity, making it suitable for time synchronization purposes.

Q3 – What is an example of an NTP server? is the best example of an NTP server.

Q4 – Why do we use NTP?

NTP is important because it ensures that all devices on a network have the same accurate time, which is essential for many applications and services that rely on timestamps, such as logging, encryption, authentication, and scheduling.


In this blog, we have covered what is NTP, its working, and its features. NTP is a vital protocol for synchronizing the clocks of computers over a network. It has been in operation since 1985 and is one of the oldest Internet protocols in current use. NTP uses a hierarchical system of time sources and servers to provide accurate and consistent timekeeping for various applications. NTP can also enhance security, network acceleration, and file system updates that depend on precise timestamps. We hope you liked the information provided here. If you are looking to learn “What is NTP?” in detail, then you can join PyNet Labs’ CCNA Training.

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