Flash crowd in a file sharing system based on random encounters

Ilkka Norros, Balakrishna Prabhu, Hannu Reittu

    Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientificpeer-review

    Abstract

    BitTorrent revolutionized the technique of distributing a very large file to a very large number of recipients. The file is chopped into small chunks that the recipients can immediately upload further. In the original design, a "tracker" keeps certain centralized control over the chunk transfer process. This paper studies a BitTorrent-like "information diffusion" system that has a fully distributed and symmetric architecture. The peers join a Distributed Hash Table -based overlay network and contact each other randomly. This kind of designs have been implemented and analysed recently. A trackerless BitTorrent system has been introduced which can be regarded as one based on random encounters - - the participating nodes contact each other at random and download missing chunks. On the analytical front, Massoulie and Vojnovic showed that a random encounter based system has surprisingly good performance without any chunk preference strategies, with the condition that each peer gets its first chunk from a sufficiently uniform distribution. In this paper, we focus on a scenario where this condition cannot be guaranteed, and show that a "rare chunk phenomenon" easily occurs, if both the encounters and the chunk selection are random. Classic urn models give some mathematical understanding of this phenomenon. We then discuss various techniques for alleviating the rare chunk problem and propose a simple distributed chunk selection policy that reduces the imbalance in the distribution of chunks within the network.
    Original languageEnglish
    Title of host publicationInterperf '06: Proceedings from the 2006 workshop on Interdisciplinary systems approach in performance evaluation and design of computer & communications sytems
    PublisherAssociation for Computing Machinery ACM
    Number of pages10
    ISBN (Print)978-1-59593-503-8
    DOIs
    Publication statusPublished - 2006
    MoE publication typeA4 Article in a conference publication
    EventWorkshop on Interdisciplinary Systems Approach in Performance Evaluation and Design of Computer and Communications Systems, Inter-Perf 2006 - Pisa, Italy
    Duration: 14 Oct 200614 Oct 2006

    Conference

    ConferenceWorkshop on Interdisciplinary Systems Approach in Performance Evaluation and Design of Computer and Communications Systems, Inter-Perf 2006
    CountryItaly
    CityPisa
    Period14/10/0614/10/06

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