The objective of this book is to provide timely and comprehensive coverage of the principles, technology, practice, and future of traffic grooming in op- cal networks. Traffic grooming considerations are already shaping new switch designs and standards, including next generation Synchronous Optical N- work/Synchronous Digital Hierarchy (SONET/SDH) and Generic Framing Procedure (GFP), are affecting future optical network technologies, and are creating new business opportunities. Yet information on the topic is sc- tered and there is a shortage of technical sources where relevant material can be accessed in a single location. The motivation for this book was to bridge this gap by providing a single authoritative point of reference to the traffic grooming state of the art. Traffic grooming is a complex subject, involving a number of interrelated concepts, standards, and technologies. It is also a rapidly growing field of study,makingitdifficultforasinglebookoverallaspectsindetail.Tocope with this scope and complexity, this book provides appropriate background information, followed by an in-depth study of a few key issues and challenges. It has been our intention to bring together a broad range of perspectives from preeminent researchers in both academia and industry. We believe that these multiple, diverse points of view add considerable value and make the contents more interesting to the reader.