LC-RTP (loss collection RTP): reliability for video caching in the Internet

The increasing amount of audio-visual (AV) content that is offered by web sites leads to a network bandwidth and storage capacity problem. Caching is one of the techniques that can ease this problem. But even in a caching system the distribution of data (i.e. the AV content) should be bandwidth-efficient. Furthermore the delivery to the end-user must regard the restrictions implied by real-time data. This paper describes LC-RTP, an efficient and simple reliable multicast protocol that complies with RTP. Its deployment would require neither changes to the network infrastructure nor to existing end-user presentation software. It provides lossless transmission of AV content into cache servers and concurrently, lossy real-time delivery to end-users using multicast. It achieves reliability by retransmission. The traffic increase is minimal because the transmission of the AV content and any caching will take place while the end-user is served. Support for multicast in the distribution system ensures that all cache servers of a multicast group can cache an AV content while transmitting it to a consumer. Finally we present the results of long distance file transmissions in order to show that LC-RTP performs well and meets the requirements for lossless transmission of AV content.