ernational SDO, the European Telecommunica- tions Standards Institute (ETSI) is a regional SDO, and the American National Standards Institute (ANSI) is more like a national SDO. There are more than 200 SDOs developing standards for the information and communication technology (ICT) sector alone. Of course, in search of mutual goals, many of these standards bodies frequently collaborate with each other. A standard can be defined as a set of technical specifications that specifies common design re- quirements for a product, process, service, or system. Some standards might be backed by interna- tional treaty law, some by government legislation, and others might have no legal force at all. Some organizations, such as the ITU, totally avoid the concept of compulsion and refer to their specifica- tion documents as recommendations. This chapter covers some of these organizations and their contributions toward defining standards in the fields of both telecommunications and time synchronization. 4.1 International Telecommunication Union The ITU, as the United Nations specialized agency for ICT, develops and publishes international telecommunications recommendations (standards). The ITU has representation from 193 member states and membership of over 900 companies, universities, and international and regional organizations. As the ITU says about itself: Established over 150 years ago in 1865, ITU is the intergovernmental body responsible for coordinating the shared global use of the radio spectrum, promoting international coopera- tion in assigning satellite orbits, improving communication infrastructure in the developing world, and establishing the worldwide standards that foster seamless interconnection of a vast range of communications systems. From broadband networks to cutting-edge wireless technologies, aeronautical and maritime navigation, radio astronomy, oceanographic and satellite-based earth monitoring as well as converging fixed-mobile phone, Internet and broadcasting technologies, ITU is committed to connecti