Streaming Flow Analyses for Prefetching in Segment-Based Proxy Caching to Improve Delivery Quality

Abstract

Segment-based proxy caching schemes have been effectively used to deliver streaming media objects. However, this approach does not always guarantee continuous delivery because the to-be-viewed segments may not be cached in the proxy in time. The potential consequence is the playback jitter at the client side due to the proxy delay in fetching these uncached segments, thus we call the problem proxy jitter. Aiming at improving the media delivery quality for segment-based caching schemes, in this paper we propose two simple and effective prefetching methods, namely, look-ahead window based prefetching and active prefetching to address the problem of proxy jitter. We focus on presenting streaming flow analyses on proxy and network resource utilizations and consumptions, performance potentials and limits of the two prefetching methods for different segment-based schemes under different network bandwidth conditions. Our study also provides some new insights into relationships between proxy caching performance and the quality of streaming. For example, we show that the objective of improving the byte hit ratio in a conventional proxy and the unique objective of minimizing the proxy jitter to deliver streaming media objects can have conflicting interests. Trace-driven simulations show the effectiveness of our prefetching methods, and further confirm our analyses.

College of William and Mary