An efficient P2P content distribution system based on altruistic demand and recoding dissemination

Peer-to-peer (P2P) content distribution systems based on random linear combination coding schemes outperform traditional block forwarding and source coding systems but have large storage requirements and high computation and communication overheads. To resolve this problem, this paper presents an efficient and scalable P2P content dissemination system based on novel altruistic demand and recoding dissemination mechanisms. In the proposed approach, the shared-content file is segmented and encoded using Reed-Solomon code at a seed. Downstream peers wishing to obtain the file utilize an altruistic demand mechanism to issue demand requests for coded blocks which are useful not only to themselves but also to their neighbors. Upon receiving these requests, the upstream peers utilize a recoding dissemination mechanism to provide the downstream peers with either an existing useful coded block or a new coded block produced using a Lagrange polynomial interpolation method. The two mechanisms rapidly increase the diversity of the coded blocks within the network and therefore provide an effective solution to the missing last block problem. In addition, it is shown that the proposed content distribution system demonstrates a substantial improvement over P2P systems based on random linear combination coding in terms of a lower storage requirement, reduced computation and communication costs, and an improved download efficiency.