Facilitating multicast in VoD systems by content pre-placement and multistage batching

We propose a novel, scalable video on demand delivery approach that attempts to take advantage of multicast in hierarchical distribution networks. Using a typical IPTV network as an example, we assume that each level of the network has the ability to store videos and attempt to pre-populate different portions of videos at each of these levels. Pre-population of portions of videos, enable the requests from one level to be batched in next higher level and thus enables the use of multicast as the delivery mechanism. We formulate the problem of identifying what portions of videos to pre-populate and where, as an optimization problem and propose two approaches, DWaFiL and WaFiL. While both these approaches use the predicted demand for videos to determine the placement solution, DWaFiL also takes users´ session duration into account. We overcome errors in demand predictions and short term popularity fluctuations using a small LRU cache in each location. Using traces from large scale commercial VoD deployment, we show that our approach is able to aggregate requests at each of the levels, reduce load on individual nodes, and outperform popular alternatives such as caching and replication in terms of scalability and server bandwidth. For example, our proposed scheme achieves up to ~27% aggregation in a single level and reduces aggregated bytes transfer from all nodes by ~25%. Finally, we analyse the dependency between different parameters and the performance of our scheme by experimenting with different parameter values.