This book investigates the problem of reducing operating cost for a video streaming content delivery network (CDN), including both the CDN's energy and traffic costs. It first introduces the key issues and design choices of representative real-world CDNs, and discusses the energy saving techniques for data centers and CDNs. Then, based on a measurement study on a large video streaming CDN, it reveals an inherent conflict between improving a video streaming CDN's energy efficiency for energy saving, and maintaining the CDN's ISP-friendly server selection policy. Further, it discusses a cost-aware capacity provisioning algorithm that not only allows the service capacity of a CDN's server clusters in numerous ISPs to be dynamically planned, but also means that the overall operating cost, including both the energy consumptions and the cross-ISP traffics, can be further optimized. In addition it uses the workload derived from real-world measurement and also implements real values of theactual power and bandwidth prices to evaluate the capacity provisioning algorithm, showing that it can significantly reduce the overall operating cost of a video streaming CDN, and effectively avoid frequent server switches. Lastly, the book outlines a number of potential research directions regarding cost-aware content delivery. The measurement, analysis, and optimization methodologies and results presented in this book are of particular interest to researchers in the Internet and networking area.