Recent changes in the production and use of multimedia content have fostered development of new ways to distribute this material to consumers. In particular, the increasing demand for this content has led to the design and deployment of new content distribution networks. The latest examples of these networks take advantage of new technological underpinnings. For example, they typically make use of larger, less expensive storage, and many incorporate peer-to-peer distribution technologies. The key challenges in designing this new generation of content distribution networks involve responding to changes in not only memory and network resources, but also content availability and popularity. This letter discusses the key design constraints for modern content distribution networks and some of the ways that these constraints can be met by innovative combinations of resource control algorithms. It also describes how a simulation environment is used to analyze some of these techniques in the context of video distribution requirements.