In this paper, we propose a novel loopback approach in a two-level streaming architecture to exploit collaborative client/proxy buffers for improving the quality and efficiency of large-scale
streaming applications. At the upper level we use an overlay to deliver video from a central server to proxy servers, at the lower level a proxy server delivers video with the help of collaborative caches. In particular, a proxy server and its clients in a local domain cache different portions of a video and form delivery loops. In each loop, a single video stream originates at the proxy, passes through a number of clients, and is passed back to the proxy. As a
result, with limited bandwidth and storage space contributed by collaborative clients, we are able to significantly reduce the requirements of network bandwidth, I/O bandwidth, and cache space at a proxy. Furthermore, we develop local repair schemes to address the client failure issues for enhancing server quality and eliminating most repairing load at servers. For popular videos, our local repair schemes are able to handle most of single-client failures without service disruption and retransmissions from a central server. Our analysis and simulations have shown the efficacy of loopback in various settings.