Dandelion: Cooperative Content Distribution with Robust Incentives
Content distribution via the Internet is becoming increasingly popular. To be cost-effective, commercial content providers are considering the use of peer-to-peer (P2P) protocols such as BitTorrent to save on bandwidth costs and to handle peak demands. However, when an online content provider uses a P2P protocol, it faces a crucial issue: how to incentivize its clients to upload to their peers. This paper presents Dandelion, a system designed to address this issue in the case of paid content distribution. Unlike previous solutions, most notably BitTorrent, Dandelion provides robust (provably non-manipulable) incentives for clients to upload to others. In addition, unlike systems with tit-for-tat-based incentives, a client is motivated to upload to its peers even if the peers do not have content that interests the client. A client that honestly uploads to its peers is rewarded with credit, which can be redeemed for various types of rewards, such as discounts on paid content. In designing Dandelion, we trade scalability for the ability to provide robust incentives. The evaluation of our prototype system on PlanetLab demonstrates the viability of our approach. A Dandelion server that runs on commodity hardware with a moderate access link is capable of supporting up to a few thousand clients. These clients can download content at rates comparable to those of BitTorrent clients.