A cooperative packet recovery protocol for multicast video

In this paper we describe a protocol that improves the quality of multicast video or audio transmissions by recovering lost packets. The protocol is applied to a corporate intranet, and measurements indicate that significant improvements in audio/video quality are achieved. A unique characteristic of this protocol is that it can be used on current MBone sessions without changing the operation of the source or receivers. The improvement in quality can be restricted to a subset of the receivers, so that a service provider, that does not necessarily generate content, can use the protocol to improve reception for its own customers. A second unique characteristic is that only a small fraction of the receivers that obtain the benefits of the protocol are active participants. As a result the problems associated with large multicast groups, such as the number of control messages, is reduced. Finally, because of the differences between data and voice or video communications, many of the network parameters that vary between or during connections are changed rather than predicted. This is a much simpler operation.