IP network based deployments of interactive video-on-demand (VoD) systems are today very limited in scope, but there is a strong belief among telecommunication companies that this market will expand exponentially in the next few years. In this article, we outline the components of VoD architectures and survey the current approaches to their design. We strive to identify the research challenges that must be addressed in the development of design tools that can determine how to expand upon an existing network infrastructure to support video-on-demand. The long tail of content and extensive growth in usage are expected to have a major impact on the streaming and storage requirements of such systems. Hybrid VoD architectures that incorporate peer-to-peer exchange are an extremely promising paradigm, but there are many challenges in developing operational and economically feasible peer-to-peer systems. VoD networks generate sufficient traffic that their impact should be considered in planning general network infrastructure
expansions.
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