This book offers deep industrial insight into the development of DSL technologies and their related applications in the telecommunications industry. It compiles the expertise of industry specialists from various perspectives, including chip designers, information theorists, systems engineers, service providers and more. It addresses in a rigorous manner specific issues that have been fundamental in the success of DSL technology, including insights into the theory that sustains DSL development, constraints, and challenges. It also offers a vast array of information not currently in the public domain, including the results of many years of practical experience that has never before been put to paper.