Designing a Tit-for-Tat Based Peer-to-Peer Video-on-Demand System

Video-on-demand (VoD) is a next-generation Internet appli-cation 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 apply-ing a BitTorrent-like tit-for-tat incentive scheme. We advo-cate the use of a loose structure in P2P VoD applications to achieve high playback rates. In this paper we propose a de-centralized piece dissemination scheme built on loosely cou-pled structures maintained using gossip. Peers are grouped into clusters depending on their playback position. Swarm-ing is performed within the clusters while distributed feed-ing 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