This book presents a comprehensive description of most important state-of-the-art fundaments and system details in the field of digital communications, networking and (network) security. This includes both cable and wireless networks. It describes several subjects which are key aspects in the development and understanding of the current and emergent services. In order to support the requirements of the new services, the proposed book addresses the means that allow improving digital communications and networks. The focus of the book is on the key requirements of emergent services.