Designing a tit-for-tat based peer-to-peer video-on-demand system

Video-on-demand (VoD) is a next-generation Internet application of increasing interest allowing users to start watching a movie almost instantaneously by downloading the video on-the-fly. Provided that all users contribute to the system, shifting to the P2P paradigm allows efficient broadcast with a limited-bandwidth source. In VoD applications pieces are downloaded in order. This prevents us from directly applying a BitTorrent-like tit-for-tat incentive scheme. We advocate the use of a loose structure in P2P VoD applications to achieve high playback rates. In this paper we propose a decentralized piece dissemination scheme built on loosely coupled structures maintained using gossip. Peers are grouped into clusters depending on their playback position. Swarming is performed within the clusters while distributed feeding ensures that less advanced clusters get missing pieces from more advanced ones. Our simulations demonstrate that structured dissemination improves from 61% to 77% the achievable playback rate.