Fast download but eternal seeding: The reward and punishment of Sharing Ratio Enforcement

Abstract

Abstract-Many private BitTorrent communities employ Sharing Ratio Enforcement (SRE) schemes to incentivize users to contribute their upload resources. It has been demonstrated that communities that use SRE are greatly oversupplied, i.e., they have much higher seeder-to-leecher ratios than communities in which SRE is not employed. The first order effect of oversupply under SRE is a positive increase in the average downloading speed. However, users are forced to seed for extremely long times to maintain adequate sharing ratios to be able to start new downloads. In this paper, we propose a fluid model to study the effects of oversupply under SRE, which predicts the average downloading speed, the average seeding time, and the average upload capacity utilization for users in communities that employ SRE. We notice that the phenomenon of oversupply has two undesired negative effects: a) Peers are forced to seed for long times, even though their seeding efforts are often not very productive (in terms of low upload capacity utilization); and b) SRE discriminates against peers with low bandwidth capacities and forces them to seed for longer durations than peers with high capacities. To alleviate these problems, we propose four different strategies for SRE, which have been inspired by ideas in social sciences and economics. We evaluate these strategies through simulations. Our results indicate that these new strategies release users from needlessly long seeding durations, while also being fair towards peers with low capacities and maintaining high systemwide downloading speeds.

Systemic Risk and User-Level Performance in Private P2P Communities

“…In general, slow peers need to seed 4 times as long as fast peers, which is the same as the ratio between the upload capacity of a fast and a slow peer. This result is also consistent with our previous theoretical results [10].…”

“…This paper is based on two previous papers [10], [18] with extensions including demonstrating detailed measurement results, unifying the analysis of SRE-based and credit-based private communities, analyzing the systemic risk of SRE-based private communities, as well as the influence of swarm popularity.…”

Dissecting Darknets

“…From Figure 12, it is noticeable that the seeding time is much longer than the leeching time; around 50% of members leeched for less than 70 days, and around 50% seeded for more than 1100 days, which means that users seed for around 15 times longer than they leech. This result is consistent with our previous findings [Chen et al 2010a[Chen et al , 2010b and the theoretical results of Jia et al [2011aJia et al [ , 2011b.…”

On the sustainability of credit-based P2P communities

“…In [9,10] another kinds of extended considerations have been done, different from ours, mainly focusing on remedy schemes avoiding crashes or crunches. We did not aim at proposing further mechanisms for preventing systemic risk, as the already developed ones can be applied in the communities we have considered.…”

“…Note that sustained status is usually temporary, which could be held for both short term or longer term. On the other hand, crash and crunch are both definitive, they can only be fixed with external interventions [9,19].…”