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IMC '05, 2005 Internet Measurement Conference — Abstract
Pp. 49–62 of the Proceedings
Characterizing Unstructured Overlay Topologies in Modern P2P File-Sharing Systems
Daniel Stutzbach and Reza Rejaie, University of Oregon; Subhabrata Sen, AT&T Labs—Research
Abstract
During recent years, peer-to-peer (P2P) file-sharing systems have
evolved in many ways to accommodate growing numbers of
participating peers. In particular, new features have changed the
properties of the unstructured overlay topology formed by these
peers. Despite their importance, little is known about the
characteristics of these topologies and their dynamics in
modern file-sharing applications.
This paper presents a detailed characterization of P2P
overlay topologies and their dynamics, focusing on the modern
Gnutella network. Using our fast and accurate P2P crawler,
we capture a complete snapshot of the Gnutella network
with more than one million peers in just a few minutes.
Leveraging more than 18,000 recent overlay snapshots, we
characterize the graph-related properties of individual
overlay snapshots and overlay dynamics across hundreds
of back-to-back snapshots. We show how inaccuracy in
snapshots can lead to erroneous conclusions—such as a
power-law degree distribution. Our results reveal that while the
Gnutella network has dramatically grown and changed in
many ways, it still exhibits the clustering and short path
lengths of a small world network. Furthermore, its overlay
topology is highly resilient to random peer departure and even
systematic attacks. More interestingly, overlay dynamics lead
to an “onion-like” biased connectivity among peers where
each peer is more likely connected to peers with higher
uptime. Therefore, long-lived peers form a stable core
that ensures reachability among peers despite overlay
dynamics.
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