are part of the transport layer. Note that this recommendation is still being worked on and is not yet published, SO it is not yet available for public download. G.8260: Definitions and Terminology for Synchronization in Packet Networks ITU-T G.8260 provides the definitions, terminology, and abbreviations used across the recommend- ations on timing and synchronization in packet networks. From the scope of the recommendation: It includes mathematical definitions for various synchronization stability and quality met- rics for packet networks, and also provides background information on the nature of packet timing systems and the impairments created by packet networks. This recommendation contains definitions of numerous concepts that are covered in this book, al- though G.8260 addresses the topic somewhat more mathematically than here. Although it is not a very long document, it goes to the next level of complexity in explaining concepts. This recom- mendation includes the following main topics: Definition of terms, such as different forms of time error Nature of packet timing systems, including the definition of significant instants Differences between packet-based and physical layer timing systems Classes of packet clocks, including packet master and packet slaves Two-way timing protocols and the flow of timing from master to slave Packet timing signal equipment interface characterization Most importantly, G.8260 defines the following terms: packet master clock, packet slave clock, and packet timing signal. There is also an appendix outlining packet measurement metrics such as MTIE and TDEV as well as information on filtering and packet selection. This recommendation is a source for further information on topics covered in "Chapter 5. Clocks, Time Error, and Noise". A revision (with full text including all amendments) was published in 2020. Link to recommendation: https://handle.itu.int/11.1002/1000/14206. G.8265: Architecture and Requirements for Packet-Based Frequency Delivery ITU-T G.8265 describes the archite