A consumer sizes a typical cable system based upon the number of channels that can be accessed. Cable systems that are capable of delivering everything ‘on demand’ must be sized differently. The size of an on-demand system is related to the amount of media (movies, switched broadcast, live broadcast, etc.) in the on-line library. Systems capable of delivering any content ‘on demand’ present the experience of having an infinite number of channels. Channel-oriented delivery systems and media-oriented delivery systems have significant differences. Media-oriented delivery systems need to offer generic, high level delivery and transport functionality to the service and application control subsystems that manage the media. This is in contrast to channel-based delivery systems that only need to assign a service to a channel. This paper presents an architectural and functional introduction to media-oriented delivery systems, including the ramifications to access control, bandwidth management, network management, and media transformation subsystems.