IEEE/ACM Transactions on Networking (TON)
| Hi-index | 0.00 |
Proxies are emerging as an important way to reduce user-perceived latency and network resource requirements in the Internet. While relaying traffic between servers and clients, a proxy can cache resources in the hope of satisfying future client requests directly at the proxy. However, existing techniques for caching text and images are not appropriate for the rapidly growing number of continuous media streams. In addition, high latency and loss rates in the Internet make it difficult to stream audio and video without introducing a large playback delay. To address these problems, we propose that, instead of caching entire audio or video streams (which may be quite large), the proxy should store a {\em prefix\/} consisting of the initial frames of each clip. Upon receiving a request for the stream, the proxy immediately initiates transmission to the client, while simultaneously requesting the remaining frames from the server. In addition to hiding the latency between the server and the proxy, storing the prefix of the stream aids the proxy in performing {\em workahead smoothing\/} into the client playback buffer. By transmitting large frames in advance of each burst, workahead smoothing substantially reduces the peak and variability of the network resource requirements along the path from the proxy to the client. We describe how to construct a smooth transmission schedule, based on the size of the prefix, smoothing, and playback buffers, without increasing client playback delay. Through experiments with MPEG-1 and MPEG-2 traces, we show how a few megabytes of buffer space at the proxy can offer substantial reductions in the bandwidth requirements of variable-bit-rate video. Drawing on these results, we present guidelines for allocating buffer space for each stream, and how to effectively share buffer and bandwidth resources among multiple clients and streams.