What is NTP and PTP?

March 26, 2024

In computer network applications, time serves as the fundamental basis for seamless interaction of network services. A comprehensive business operation strictly adheres to a precise temporal logic, leaving no room for time errors or deviations that may lead to grave consequences. In any time-sensitive network environment, synchronization becomes imperative in order to ensure smooth system functionality. This article aims to introduce you to the world of networking and shed light on common approaches employed for achieving impeccable time synchronization.

What is Time Server?

Time servers are essential for time synchronization, as they acquire a standard clock signal from geosynchronous satellites of the GNSS (Global Navigation Satellite System), such as GPS. These time servers then transmit this information over a TCP/IP network to provide accurate, secure, reliable, and versatile time services to network devices (users).

What is Network time Protocol(NTP)?

How do we synchronize our devices after the time server has obtained the standard reference time?

One of the earliest standards for clock synchronization in networks was achieved through the utilization of the Network Time Protocol (NTP), which is based on Internet Protocol (IP) and User Datagram Protocol (UDP). The relevant standards are defined in RFC1305. NTP serves to synchronize clocks between clients and servers, facilitating highly accurate time correction with a precision on the order of milliseconds. NTP servers receive precise Coordinated Universal Time from authoritative clock sources such as atomic clocks or GPS systems, while clients request and obtain time information from these servers. NTP timing is widely supported by commonly used devices including computers, servers, and cameras, making it the most prevalent method employed for achieving accurate time synchronization.

What is Simple Network Time Protocol (SNTP）？

Another branch of NTP development is SNTP (Simple Network Time Protocol), which simplifies many algorithms and steps of NTP to gain efficiency, making it suitable for clients with less time accuracy. However, the time accuracy of SNTP is not as good as that of NTP. SNTP and NTP share the same format of network packets but differ in how the system handles their contents for time synchronization. They are essentially two different approaches to time synchronization. While a full-featured NTP client achieves high accuracy, an SNTP client is only recommended for simple applications where accuracy and reliability are not critical.

What is Precision Time Protocol(PTP)?

PTP (Precision Time Protocol) is a time synchronization protocol used for high-precision frequency synchronization and phase synchronization between network nodes, with sub-microsecond time synchronization accuracy, which can meet the high-precision time synchronization requirements of radio and television networks, urban rail transit, wireless access networks and other scenarios. IEEE 1588 is the basic protocol of PTP, which specifies the principles and message interaction processing specifications for high-precision clock synchronization in networks. specifies the principles and message interaction processing specifications used for high-precision clock synchronization in the network, which was initially applied to industrial automation and is now mainly used for bridging LANs.

Therefore, PTP is also known as IEEE 1588, or 1588 for short. 1588 is divided into two versions, 1588v1 and 1588v2. 1588v1 can only achieve sub-millisecond time synchronization accuracy, while 1588v2 can achieve sub-microsecond synchronization accuracy, and can achieve both phase synchronization and frequency synchronization. Currently, the 1588v2 is more widely used than the 1588v1.

Precision Time Protocol (PTP) and Network Time Protocol (NTP) are often compared, and they differ in the following aspects:

What is Difference between PTP and NTP?

	NTP	PTP
Communication Methods	NTP uses a client-server architecture where the client requests time updates from a specified NTP server.	PTP uses a master-slave architecture where the master clock distributes time information to the slave clocks, allowing for more accurate synchronization of clocks.
Standardization & Applications	Part of the IEEE1588 standard, which mainly used in applications that require very high time synchronization accuracy, such as industrial control, financial transaction	Based on IP and UDP, the relevant standards are defined in RFC1305 and is mainly suitable for occasions that do not require high time synchronization accuracy, such as ordinary office environments.
Time Stamping	Software timestamps, which may be affected by processing time, limiting their accuracy, especially in high-precision applications.	Hardware timestamps to provide finer time resolution for environments with high network traffic and variable latency
Time synchronization Accuracy	Millisecond	Sub-microseconds/Nanoseconds Support
Frequency synchronization	Not support	Support
Phase synchronization	Support	Support
Description	Phase synchronization is achieved by transmitting phase signals through NTP messages, but it cannot meet the micro-second/ nanosecond time synchronization accuracy requirements of finance and power.	Through the PTP message transmission frequency and phase information, and hardware together to achieve high-precision time synchronization. With the advancement of hardware and software technology, the accuracy of PTP can reach tens of nanoseconds or even higher.

Applications of Time Synchronization Protocol?

Data Center

Data centers require NTP/PTP synchronization to ensure time domain operation of the cluster. Synchronization is essential for virtual machine computing. The chronology of log events is important for examining error logic. Time and date are critical for automated backups and SQL conversion rollbacks. Weak synchronization makes IT/IoT risks unstable.

Banks

The Bank’s IT department utilizes data center clusters to operate in synchronized time domains that demand microsecond precision. The seamless functioning of electronic payment systems and credit card operations relies on robust security measures and transaction registries stored in databases. Timestamps play a crucial role in the long-term preservation of signatures and data sealing. While the accuracy requirement is only one-tenth of a second, there are stringent demands for trusted time references. RFC 3161, along with its timestamps, serves as undeniable proof for financial transactions. Banking IT infrastructures necessitate resilient automated overnight backup systems.

Smart Grid

The implementation of smart grid scenarios, such as relay protection and timely fault recovery in power networks, necessitates precise time synchronization among power devices to ensure swift fault recovery. Currently, the industry has established two 1588v2 power network standards, namely IEEE C37.238 and IEC 61850-9-3, which offer an Ethernet communication architecture specifically designed for power networks.

Automatic Driving

The nanosecond level and the PTP IEEE1588 profile AES67/IEEE 802.1AS are utilized by autonomous vehicles for automatic driving. Vehicle queuing is among the range of features that self-driving cars may adopt, enabling a group of vehicles to travel closely, safely, and at high speeds. Each car in the queue can establish wireless communication with others. Moreover, synchronization plays a crucial role in autonomous AI-powered vehicles as it offers an alternative to GNSS positioning systems based on multiple LiDAR sensors and object recognition. This synchronized solution provides protection against GNSS interference/spoofing attacks.

Industrial Field

Automation of industrial networks in order to ensure automated production, the requirements of the industrial terminals have a unified time, between the equipment to reach a high-precision time synchronization, the industry currently exists in two 1588v2 industrial network standards, IEEE 802.1AS and IEC 62439-3.

Video/Mass Media

With the requirement of large bandwidth for HD video broadcasting, the media network (such as the network of TV stations) has gradually shifted to IP from the traditional SDI (Serial Digital Interface) network, and therefore IP network is also used to deliver 1588v2 messages to each media terminal to ensure HD video broadcasting by each media terminal. Currently there are two industry standards, SMPTE ST-2059 and AES 67.