The modern telecommunications world is a complicated place, overloaded with jargon and bewilderingly full of different technical options and opportunities. Many experts are only experts of small domains and within limited geographies. For newcomers it is often difficult to gain a grasp on the basic principles and even harder to unravel the mysterious technical paradoxes and the apparent contradictions of many modern technologies. My greatest hope in writing this book is that you, the reader, will find help and insight amongst its pages. I wish for no greater commendation than your thoughts that you find the subject of A TM presented here in an accessible and readable form. I hope also that the comprehensive glossary will remain with you, as your wayfinder through all that jargon! Martin P. Clark Frankfurt, Germany 20 December 1995 Acknowledgements No book on Asynchronous Transfer Mode (ATM) could fail to recognize the invaluable contribution to this technology and to world standardization as a whole made by the International Telecommunications Union and the ATM Forum, and you will find references to their work throughout the text. Particular copyright extracts are labelled accordingly, but the full texts may be obtained (as relevant) from ITU Sales and Marketing Service, Place des Nations, CH-1211 Geneva 20, Switzerland or from ATM Forum, 2570 West EI Camino Real, Suite 304, Mountain View, California CA 94040, USA.