THE TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. Although ITU-T Recommendations are non-binding, they are widely used because they guarantee the interconnectivity and interoperability of networks and enable telecommunication services to be provided worldwide. The regulatory and policy functions of ITU-T are performed by the World Telecommunication Standardization Assembly (WTSA) and by the Telecommunication Standardization Advisory Group (TSAG), supported by Study Groups and their Working Parties. © ITU 2010 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU.