[bittorrent] paper on BitTorrent overlay properties

Arnaud Legout Arnaud.Legout at sophia.inria.fr
Fri Jul 13 15:03:07 EDT 2007


We are pleased to announce a new technical report on the properties
of the overlay formed by BitTorrent.
The report is available here:

Any feedback is welcome.

Arnaud Legout.

Understanding the Properties of the BitTorrent Overlay

In this paper, we conduct extensive simulations to understand the
properties of the overlay generated by BitTorrent. We start by analyzing
how the overlay properties impact the efficiency of BitTorrent. We focus
on the average peer set size (i.e., average number of neighbors), the
time for a peer to reach its maximum peer set size, and the diameter of
the overlay. In particular, we show that the later a peer arrives in a
torrent, the longer it takes to reach its maximum peer set size. Then,
we evaluate the impact of the maximum peer set size, the maximum number
of outgoing connections per peer, and the number of NATed peers on the
overlay properties. We show that BitTorrent generates a robust overlay,
but that this overlay is not a random graph. In particular, the
connectivity of a peer to its neighbors depends on its arriving order in
the torrent. We also show that a large number of NATed peers
significantly compromise the robustness of the overlay to attacks.
Finally, we evaluate the impact of peer exchange on the overlay
properties, and we show that it generates a chain-like overlay with a
large diameter, which will adversely impact the efficiency of large

Arnaud Legout, Ph.D.

INRIA Sophia Antipolis - Planète  Phone :
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06902 Sophia Antipolis CEDEX      E-mail: arnaud.legout at sophia.inria.fr
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