Proxy caching algorithms and implementation for time-shifted TV services

The increasing popularity of multimedia streaming applications introduces new challenges in content distribution networks (CDNs). Streaming services such as Video on Demand (VoD) or digital television over the Internet (lPTV) are very bandwidth-intensive and cannot tolerate the high start-up delays and poor loss properties of today's Internet. To solve these problems, caching (the initial segment of) popular streams at proxies could be envisaged. This paper presents a novel caching algorithm and architecture for time-shifted television (tsTV) and its implementation, using the IETF's Real-Time Streaming Protocol (RTSP). The algorithm uses sliding caching windows with sizes depending on content popularity and/or distance metrics. The caches can work in stand-alone mode as well as in co-operative mode. This paper shows that the network load can already be reduced considerably using small diskless caches, especially when using co-operative caching. A prototype implementation is detailed and evaluated through performance measurements. Copyright (C) 2007 John Wiley & Sons, Ltd.