What is NTP (Network Time Protocol)?

Understanding NTP (Network Time Protocol) is essential for us to ensure accurate time synchronization in the network. This protocol ensures consistent timekeeping between devices. Thus, it plays a vital role in networked devices as it is necessary for various applications.

In this article, I will explain the definition and details of NTP and its capabilities. Let’s dive into the world of time protocols and examine their essential components!

What is NTP Protocol?

NTP Protocol is a protocol designed to synchronize the clocks of workstations on the network.

Version 3 of this protocol is an Internet standard formalized in RFC 1305. The version 4 protocol is an essential revision of the standard in question and is under development but has not yet been formalized in an RFC. A simple version of NTP (SNTP) version 4 is described in RFC 2030.

Also, it uses UDP as the Transport Layer using Port 123. It is designed to withstand the effects of variable delay, in addition to millisecond order accuracy, according to Coordinated Universal Time (UTC).

UTC is propagated through special receivers such as radios, satellites, or modems and is managed by governments of various nations of the world. A limited number of computers are equipped with these receivers and function as a time server.

NT Protocol is one of the oldest Internet protocols still in use. Dave Mills originally designed this protocol from the University of Delaware and is now using the Marzullo Algorithm with a UTC scale, including features like seconds, with a team of volunteers that continue to do so. NTPv4 can be synchronized over the Internet with a maximum difference of 10 milliseconds (1/100 second) and can reach 200 microseconds (1/5000 seconds) or more in local area networks under ideal conditions.

This protocol uses the Clock Stratum Hierarchy System, in which Stratum 1 systems are synchronized with an external clock, such as a GPS Clock or some Atomic Clock. NTP layer two systems derive their time from one or more layer one systems, and note that this is different from the clock layer used in telecommunications systems.

There is a less complicated format that does not require the storage of information about previous communications, known as the Simple Network Time Protocol or SNTP. It has gained popularity in embedded devices and applications where high precision is not required.

NTP Package Description

Description of the NTP/SNTP Version 4 packet format following IP and UDP headers.

• Root delay
• Root Dispersion
• Reference Identifier
• Reference Timestamp (64)
• Originate Timestamp (64)
• Receive Timestamp (64)
• Transmit Timestamp (64)
• Key Identifier (optional) (32)
• Message Digest (optional) (128)

LI (Leap Indicator)

A 2-bit code is used to indicate that a second will be added/removed from the last minute of the current day.

• without modification
• the last minute is 61 seconds
• the last minute is 59 seconds
• alarm condition (clock not synchronized)

Version Number (VN)

It is a 3-bit integer that represents the version number. Version 3 specifies version 3 (IPv4 only) and version 4 for version 4 (IPv4, IPv6, and OSI). If a distinction needs to be made between IPv4, IPv6, and OSI, the encapsulated context should be examined.

Mode

A three-bit integer used to represent the mode is defined as follows:

• reserved
• symmetric active
• symmetric passive
• client
• server
• broadcast
• reserved for NTP control messages
• reserved for private use

Stratum

It is an 8-bit unsigned integer representing the level (layer) of the local server. The defined values ​​are as follows:

• not specified or not available
• primary reference (e.g., radio clock)
• secondary reference (via NTP or SNTP)
• reserved

Poll Interval

An 8-bit signed integer that represents the maximum time interval between two consecutive messages in seconds and is shown as the closest power to 2. Most applications use a range of 6 bits to 10.

Precision

A signed integer that shows the precision of the local clock up to the nearest two powers in seconds.

Conclusion

As a result, NTP synchronizes time across network devices. Also, this protocol includes packet description and capabilities. This information is essential for network administrators and IT professionals. So, if we use it effectively, we ensure consistent timekeeping for organizations. Thus, we support various critical applications.

In addition, the importance of NTP increases as the reliance on interconnected devices and systems increases. Since its importance and role in modern networks is excellent, we should not ignore it.