Reducing Content Distribution Time in P2P-based Multicast Using Rateless Codes

In this paper a novel protocol for application level multicast, that is designed so as to exploit the advantages offered by rateless coding, is proposed. With rateless coding a set of k packets can be used to generate an arbitrary number of coded packets. Any set of slightly more than k coded packets can be used by a node in the network to recover the information. The proposed protocol is based on a simple encoding and relaying policy that is able to reduce the average decoding delay in an application level multicast overlay. Moreover, no prior knowledge of the network topology is required thus making the solution very simple and general. The performance of the novel protocol is analyzed employing synthetic instances of random graphs. This study, besides showing the advantages of the proposed technique, permits to get a deeper insight into the behavior of rateless codes in complex networks. Moreover, the proposed protocol is evaluated on real topologies, obtained crawling a widespread p2p video streaming application. The proposed protocol turns out to be very efficient with a significant gain in terms of decoding delay on both synthetic and real networks.