On the impact of incentives in eMule, analysis and measurements of a popular file-sharing application

Motivated by the popularity of content distribution and file sharing applications that nowadays dominate Internet traffic, we focus on the incentive mechanism of a very popular, yet not very well studied, peer-to-peer application, eMule. In our work, we recognize that the incentive scheme of eMule is more sophisticated than current alternatives (e.g., BitTorrent) as it uses a general, priority-based, time-dependent queuing discipline to differentiate service among cooperative users and free-riders. In this paper, we describe a general model of such an incentive mechanism and analyze its properties in terms of application performance. We validate our model using both numerical simulations (when analytical techniques become prohibitive) and with a measurement campaign of the live eMule system. Our results, in addition to validating our model, indicate that the incentive scheme of eMule suffers from starvation. Therefore, we present an alternative scheme that mitigates this problem, and validate it through numerical simulations and a second measurement campaign.