 Q13/15, SO vari- ous versions of any given document are available for download at any one time. Even though a single version (usually the latest) might be shown to be in force, that does not mean that the in- force version is reflected in the devices sitting in your network. Generally, the implementation of these standards in everyday products tends to lag by a significant period-up to several years. This is because it takes time for the component vendors who make os- cillators, phase-locked loop (PLL), servos, stacks, clocks, physical layer (PHY) devices, Global Navigation Satellite System (GNSS) chipsets, and SO on to update their designs and then test, cer- tify, and manufacture newer versions of their products. Then the equipment vendors need to incorporate these new devices into later generations of their products, which may require a complete redesign or re-spin of the current hardware design. Once the hardware is done, it is followed by engineering of the required support in software, performing validation testing, performance tuning, and finally shipping to the operator. Just be aware that there is some significant lag in adoption of new features and measures. Over the past few years, there has also been change in the way the ITU-T distributes its recom- mendations. Historically, each recommendation had to be read in combination with several amend- ments, corrections (corrigenda), errata, and revisions. This made it difficult for the casual reader to consume, as there was rarely a single document that contained the complete text of a single recommendation. Recently, however, the ITU-T has moved to a system whereby it re-releases updated recommenda- tions in full, with change bars indicating alterations to the text. In this way, an amendment to a re- commendation now contains the full text, whereas previously it contained just the changes to the original text. This approach makes it much easier for the reader. Additionally, many recommendations contain annexes and appendixes. The difference between them i