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Research Projects
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A More Intelligent Use of Seeding Capacity in BitTorrent
Measurement studies have shown that real world BitTorrent (BT) systems have
a high seed capacity. We provide analytical models that explicitly
include the effect of seed capacity in the performance of the
system. Our models indicate that while seed capacity can have a significant
effect on BT performance, it is also easily exploitable by free-riders,
and such free-riding clients exist out in the wild today.
In this work, we propose simple and scalable approaches that make
a more intelligent use of seed capacity by hurting free-riders without
explicit identification while improving the performance of contributing
nodes.
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Multi-Torrent: a Simple BitTorrent Improvement
BitTorrent (BT) has become an extremely popular and successful peer-to-peer
(P2P) file sharing system. Although empirical evidence suggests that most nodes
participate in multiple torrents, surprisingly little research literature
exists on this topic. In this work, we focus on a multi-torrent system, and
specifically on the questions of (a) what incentives could be provided for nodes to
contribute resources as seeds in a multi-torrent environment, and (b) what are the
resulting performance consequences of such behavior, both on the nodes which are
willing to be seeds and on the overall system.
We give evidence of the current system lacking incentives for nodes to stay around
as seeds in a multi-torrent environment. Motivated by that, we propose a cross torrent
based method and then present a simulation-based performance study to illustrate the
benefits of our approach.
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On Multi-Tree-Based Streaming
In this work, we develop and analyze a multi-tree-based scheme for
streaming media in overlay networks. We provide tree construction
algorithms that achieve perfect load balance and derive corresponding
bounds on delay characteristics as well as buffer space requirements.
For our scheme we show that the delay is optimal when the trees are
either 2-ary or 3-ary. We also illustrate the performance characteristics
of our schemes using simulation-based studies, and we extend our schemes
to allow for node churn. Our main goal is to develop an understanding of
playback delay and buffer requirements inherent in all such schemes.
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Multi-path Streaming: Toward Picture-perfect Streaming on the Internet
Quality of service (QoS) in streaming of continuous media (CM) over
the Internet is poor, which is partly due to variations in delays,
bandwidth limitations, and packet losses. Although CM applications can
tolerate some missing data, non-recoverable information loss degrades
these applications' QoS. Consequently, a number of application areas
(e.g., those related to the entertainment industry) have backed away
from streaming of their content over the Internet. Inability to control
the resulting visual and auditory quality of the resulting streamed
presentation is an important reason for such a trend. We believe that
this trend can be reversed. To this end, our work focuses on providing
high quality streaming through the exploitation of multiple paths
existing in the network. By high quality, we mean with significant
bandwidth requirements, of relatively long duration, and without
information loss or hiccups in data delivery.
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© alix - 2008
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