Video on Demand (VOD) is evolving and growing rapidly. As a result, transport, content, and service offerings are changing the fundamental economics and operational efficiency of Video on Demand networks. On Demand services of a few premium movies and HBO On Demand are giving way to the NFL on Demand, Nickelodeon on Demand, Everything on Demand. Content distribution networks comprised of a small array of catchers directly connected to the back end of a small video server farm are evolving into full fledged propagation services and hierarchical storage models. The streaming network has evolved from a network with streaming servers directly connected to ASI ports to a GbE based transport network. Services are expanding from traditional transactional, free, and subscription services to include a new variety of On Demand service offerings. Everything from reality TV, to advertising, to personal ads is becoming available on line. With each of the elements of the On Demand system dissected into its pieces, the paper will put these elements together in a single cohesive view of optimal On Demand network topologies based on the evolution of transport, content and service type.