ix: Definitions relating to clock equipment, synchronization networks, clock modes of operation, clock characterization, and some SDH-specific terms Phase variation and impairments, and the specification of them Clock measurement Appendix II, "Definitions and properties of frequency and time stability quantities," which cov- ers Allan deviation (ADEV), modified ADEV (MDEV), time deviation (TDEV), time interval error (TIE), and maximum time interval error (MTIE) This recommendation is good background reading to get a different explanation of the common terms and concepts used in synchronization and timing. The fact that it is not very hard to read (at least most of it) makes it a handy aid to the learning process. Link to recommendation: https://www.itu.int/rec/T-REC-G.810/en 8.2.1 End-to-End Network Performance These recommendations belong to a collection that defines the end-to-end network performance of a group of clocks and network elements carrying frequency with physical methods. They also go back a long way in time and have barely been updated for the last 20 years. G.823: The Control of Jitter and Wander Within Digital Networks Which Are Based on the 2048 kbit/s Hierarchy ITU-T G.823 covers the network limits for jitter and wander for traffic and synchronization net- works based on the 2048-kbps hierarchy. The electrical characteristics of these interfaces are defined in G.703. From the introduction to the recommendation: An excessive amount of jitter and wander can adversely affect both digital (e.g. by genera- tion of bit errors, slips and other abnormalities) and analogue signals (e.g. by unwanted phase modulation of the transmitted signal). It is therefore necessary to set limits on the maximum magnitude of jitter and wander, and the corresponding minimum jitter and wander tolerance at network interfaces, in order to guarantee a proper quality of the transmitted signals and a proper design of the equipment. This recommendation includes the following main topics, annexes, and appendixes: Network limits 