With rapid advances in networking technology, video data has become an inseparable part of many applications. In particular, video on demand (VoD) is a core technology for important applications such as digital libraries, distance learning, corporate training, public information systems, electronic commerce, and entertainment, for example. A typical VoD service allows remote users to playback a video from a large collection of videos stored on one or more servers. In response to a service request, a video server delivers the video to the user in an isochronous video stream.
The growing popularity of wireless networks on the one hand, combined with the need for ubiquitous access to VoD resources on the other hand, presents challenges with respect to communicating the ever-increasing amount of data available from video servers to a growing user base.
For example, problems may arise when there are sudden instances of high demand for data, such as videos. For instance, the death of the popular singer Michael Jackson caused a period of great interest in his videos. When an event like this arises, the substantial increase in demand for the related videos may significantly impact normal access to other regular videos and data.
Various approaches have been used for disseminating large amounts of data, such as video streams, to a large number of users. One such approach is multicast technology, which allows many users to share a popular server stream. However, this approach generally requires all users to watch the same data at an appointed time, and therefore cannot be started at a user's convenience “on demand”.