Content Redundancy in BitTorrent

The BitTorrent Peer-to-Peer (P2P) file sharing protocol is a popular way to distribute digital content. It´s a very scalable protocol, where the entry of new peers increases the total capacity of the network, especially after peers have finished their download and remain just as uploaders (known as seeders). Through the monitoring of live Internet swarms we have discovered that there is a significant amount of repeated content being shared. Various publishers tend to publish the same content through different torrent files, creating independent swarms that end up having the exact same content or a large number of common parts. As such, the size of each swarm is smaller than it could be, should there be only one swarm for that content. This affects the performance of BitTorrent and diminishes the opportunities for exploiting locality. By analyzing 3067 swarms, we concluded that there is a significant amount of common content between different swarms. Through our measurement results, we show that this redundancy can be exploited in order to increase data availability and source diversity. By increasing the swarm size through the aggregation of different swarms sharing common content, the swarm´s locality properties are also improved. These results suggest that there can be many advantages for both peers and ISPs if this redundant content is exploited by BitTorrent.