SODON: a high availability multi-source content distribution overlay

Abstract

Multi-source content distribution and file download systems such as BitTorrent and Edonkey emerge as a better scheme than the traditional ftp systems in distributing files to very large scale systems. However, a major drawback of those systems is that they largely rely on a tracker server to maintain state information of a horde. Furthermore, if the peer holding all the pieces of a file leaves the system, there is a high probability that the other peers cannot download the entire file. We propose a scalable and highly available P2P multi-source content distribution system called SODON to solve those problems. SODON distributes all the pieces of a file from a seed to a number of carefully selected sub-seeds in order to guarantee a complete set of pieces that are available for a long time. The sub-seeds also work as sub-trackers to maintain the horde state information. As a result, the original tracker server is not overwhelmed by a large population of download requests. Our traces on BitTorrent and simulation result show that SODON is feasible to build, and the sub-seeding and sub-tracking schemes effectively reduce the tracker load while offering a comparatively high availability of shared files