Offloading video servers: P2P and/or caches?

Using a decentralized content distribution scheme is appealing when considering the potentially enormous amount of data generated by high quality video on demand (VoD) services. There is, unfortunately, little information available about which form of content delivery would yield maximum benefit and how it should be configured to achieve that, given a certain cost structure and request distribution. In this paper we investigate the properties of a VoD streaming system, where the clients download stored videos from dedicated servers, but want to start watching them while downloading. We analyze how the servers can be offloaded by a P2P data distribution network, and whether adding network caches can further optimize the system, or not. We show that the parameters of the P2P scheme can be set in an optimal way, though, we notice that even a large deviation from the optimum doesn't decrease the offloading performance significantly. The offloading can be increased at the expense of the startup delay, but by adding caches we can achieve both high performance and low startup delays.