Abstract: Time synchronization technology is widely used in industrial automation, precision measurement and control, and military command information system. The IEEE 1588 precision time protocol provides sub-microsecond network time synchronization to meet the high precision measurement and control needs of the industry. White Rabbit（WR） time synchronization is a distributed time synchronization solution based on synchronous ethernet, IEEE 1588v2 protocol and all Digital Dual Mixer Time Difference（DDMTD）, which provides sub-nanosecond synchronization accuracy. The SAE AS6802 protocol is a high-precision, fault-tolerant, development-ready clock synchronization protocol that provides Time-Triggered Ethernet（TTE） with a globally synchronized clock of the required accuracy and a wide range of distributed determinism. This article reviews the research and development of these three time synchronization technologies, analyzes the advantages and disadvantages of the three technologies, and looks forward to the future development trend of network time synchronization technology.

Key words: network time synchronization, IEEE 1588, White Rabbit（WR）, SAE AS6802

摘要： 时间同步技术广泛应用于工业自动化、精密测量与控制、军队指挥信息化系统等领域。IEEE 1588精密时间协议提供亚微秒级的网络时间同步，能够满足工业领域的高精度测量和控制需求。White Rabbit时间同步技术（WR）是基于同步以太网、IEEE 1588v2协议和全数字双混频鉴相器技术（DDMTD）的一种分布式时间同步方案，能够提供亚纳秒级的同步精度。SAE AS6802协议是一种高精度、可容错、具有开发潜力的时钟同步协议，可为时间触发以太网（Time-Triggered Ethernet，TTE）提供所需精度的全局同步时钟。回顾了这三种时间同步技术的研究发展状况，并分析了其优缺点，展望了未来网络时间同步技术可能面临的挑战和发展趋势。

关键词: 网络时间同步, IEEE 1588, White Rabbit, SAE AS6802