Motivated by the increasing availability of media content in the Internet, improvements of network bandwidth in the Internet backbone and the availability of faster “last mile” connections, such as cable modems and DSL (digital subscriber lines) services, users are becoming increasingly interested in watching movies or TV broadcasts, listening to radio or music, or viewing lectures over the Internet. Consequently, streaming media content (i.e., audio and video) is becoming a significant fraction of the total traffic in the Internet and demands for effective as well as efficient media delivery infrastructures. To this purpose, the streaming content distribution networks (SCDNs) have lastly conveyed huge interest. An SCDN is an overlay network aiming at improving the streaming-based delivery of content to the end users (or clients) in the Internet, in which popular content may be cached or replicated at a number of servers, placed closer to some of the client populations. Being an emergent technology, SCDNs have to face several technical open issues related to the internal content distribution infrastructure, content management policies, content discovery mechanisms, redirection mechanisms, and delivery of media streaming.