Achieving high-bitrate overlay live streaming with proxy helpers

Meeting a high bitrate requirement (say, 1 Mbps) in overlay live streaming is challenging. We consider the design and optimization of an overlay network formed by distributed proxies for high-bitrate live streaming. The video stream is divided into substreams and pushed via multiple trees to all the proxy servers with users. To effectively overcome bandwidth bottlenecks, we employ proxy helpers to provide rich path diversity. They do not have any attached users, and hence may forward any arbitrary subset of the substreams. In this way, the helpers serve as “stepping stones” to provide full streams to the servers. A critical issue is how to best use the proxy helpers to minimize delay meeting a certain streaming rate requirement. We first model the network by capturing various delay and bandwidth components. We formulate the problem and show that it is NP-hard. We then propose an efficient algorithm called Stepping-Stones. Our results based on simulation on real Internet topologies show that the algorithm outperforms other overlay protocols by effectively making use of helpers to achieve low delay and high streaming rate.