sport of clock quality and traceability information. Consumer of time and sync: Covers what factors the engineer needs to consider when determ- ining what the end application needs for its timing and synchronous requirements. As described in "Chapter 2. Usage of Synchronization and Timing", synchronization is a process of aligning two or more clocks to the same frequency or time, usually by aligning each of them to a common reference clock. Synchronization enables services such as Positioning, navigation, and timing (PNT) Transmitters broadcasting on single frequency networks (SFN) Control and command systems for Internet of things (IoT) or cloud-based applications Coordinated transmission and interference control in a mobile network Phased array antenna applications such as beam-forming This chapter focuses on numerous concepts required to understand synchronization and the com- ponents needed to build a timing distribution network. This chapter covers the definition of a clock, the different types of clocks and sources of clock signals, as well as the different operating modes of the clock. You will learn about the various clock types in the hierarchy of the network chain; meth- ods to trace the reference clock; and how to utilize different timing reference interfaces for accurate timing distribution and measurement. This chapter also covers the difference between frequency and phase synchronization and various time distribution techniques. 3.1 Synchronous Networks Overview Network synchronization involves distributing time and frequency, or synchronizing clocks across different geographies, by using a network. Any number of different network transport technologies, such as those based on fiber, cable, or even radio, can be used to carry timing information either as a physical signal or as data. The main goal is to synchronize all the clocks connected to the network to a single, common frequency and/or time reference. This problem of aligning distributed clocks is widely studied, and various methods are used to