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Unformatted text preview: Contracts: Practical Contribution Incentives for P2P Live Streaming Michael Piatek * Arvind Krishnamurthy * Arun Venkataramani † Richard Yang David Zhang × Alexander Jaffe * Abstract PPLive is a popular P2P video system used daily by mil- lions of people worldwide. Achieving this level of scala- bility depends on users making contributions to the sys- tem, but currently, these contributions are neither verified nor rewarded. In this paper, we describe the design and implementation of Contracts , a new, practical approach to providing contribution incentives in P2P live stream- ing systems. Using measurements of tens of thousands of PPLive users, we show that widely-used bilateral in- centive strategies cannot be effectively applied to the live streaming environment. Contracts adopts a different ap- proach: rewarding globally effective contribution with improved robustness. Using a modified PPLive client, we show that Contracts both improves performance and strengthens contribution incentives. For example, in our experiments, the fraction of PPLive clients using Con- tracts experiencing loss-free playback is more than 4 times that of native PPLive. 1 Introduction System collapse due to large-scale reductions in user contributions is a major concern for PPLive, which is one of the most widely deployed live streaming services on the Internet today, serving more than 20 million active users spread across the globe. Using peer-to-peer (P2P) as the core technique, PPLive achieves cost-effective live video distribution by providing a small amount of seed bandwidth to a few participants, with the rest of the dis- tribution being performed by users relaying data. Thus, the availability and scalability of PPLive depends cru- cially on the contributions of its users. The current PPLive design neither verifies nor rewards contributions, creating the potential for strategic users to restrict their contribution, degrading robustness. This is particularly true in environments where capacity is lim- ited or priced by usage. Furthermore, when developing an open live video streaming standard, relying on closed systems with proprietary protocols is not feasible. In this paper, we explore how to provide practical contribution incentives for P2P live streaming, using PPLive as a concrete example. Although incentives have been studied extensively in the case of widely deployed file-sharing systems (e.g., [1, 16, 22]), live streaming presents unique challenges. For instance, clients cannot be rewarded with faster downloads once they are receiv- ing data at the broadcast rate (since additional data has * U. of Washington; † U. of Mass; Yale; × PPLive. not yet been produced). While some recent proposals have considered contribution incentives in a live stream- ing setting (e.g., ), they do not take into account sev- eral practical considerations of deployed systems, such as client heterogeneity and operation under bandwidth constraints. We provide an examination of live stream-constraints....
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This note was uploaded on 02/23/2012 for the course CS 591 taught by Professor Dongyanxu during the Fall '10 term at Purdue University-West Lafayette.
- Fall '10