46 research outputs found
Clustering and Sharing Incentives in BitTorrent Systems
Peer-to-peer protocols play an increasingly instrumental role in Internet
content distribution. Consequently, it is important to gain a full
understanding of how these protocols behave in practice and how their
parameters impact overall performance. We present the first experimental
investigation of the peer selection strategy of the popular BitTorrent protocol
in an instrumented private torrent. By observing the decisions of more than 40
nodes, we validate three BitTorrent properties that, though widely believed to
hold, have not been demonstrated experimentally. These include the clustering
of similar-bandwidth peers, the effectiveness of BitTorrent's sharing
incentives, and the peers' high average upload utilization. In addition, our
results show that BitTorrent's new choking algorithm in seed state provides
uniform service to all peers, and that an underprovisioned initial seed leads
to the absence of peer clustering and less effective sharing incentives. Based
on our observations, we provide guidelines for seed provisioning by content
providers, and discuss a tracker protocol extension that addresses an
identified limitation of the protocol
Clustering and Sharing Incentives in BitTorrent Systems
Peer-to-peer protocols play an increasingly instrumental role in Internet content distribution. Consequently, it is important to gain a full understanding of how these protocols behave in practice and how their parameters impact overall performance. We present the first experimental investigation of the peer selection strategy of the popular BitTorrent protocol in an instrumented private torrent. By observing the decisions of more than 40 nodes, we validate three BitTorrent properties that, though widely believed to hold, have not been demonstrated experimentally. These include the clustering of similar-bandwidth peers, the effectiveness of BitTorrent's sharing incentives, and the peers' high average upload utilization. In addition, our results show that BitTorrent's new choking algorithm in seed state provides uniform service to all peers, and that an underprovisioned initial seed leads to the absence of peer clustering and less effective sharing incentives. Based on our observations, we provide guidelines for seed provisioning by content providers, and discuss a tracker protocol extension that addresses an identified limitation of the protocol
A framework for highly reconfigurable P2P trackers
The increasing use of Peer to Peer (P2P) applications, usually ruled by selfish behaviors, is posing new challenges to the research community. As contributions of this work we firstly devise a general framework underpinning the development of highly reconfigurable P2P trackers. Following that, a novel tracker architecture is proposed and several illustrative and enhanced tracker configurations are described. As result, the devised solution turns possible that flexible, programmable and adaptive peer selection mechanisms can be introduced at the P2P application level.
The proposed solution assumes the general framework of one of the most popular P2P solutions, in this case a BitTorrent-like approach. As illustrative examples of the proposed framework capabilities, several straightforward and easy to deploy tracker configuration examples are presented, including methods for qualitative differentiation of swarm peers and advanced P2P Traffic Engineering mechanisms fostering the collaboration efforts between ISPs and P2P applications. Both the framework and the devised tracker configurations are validated resorting to simulation experiments.(undefined
Small Is Not Always Beautiful
Peer-to-peer content distribution systems have been enjoying great
popularity, and are now gaining momentum as a means of disseminating video
streams over the Internet. In many of these protocols, including the popular
BitTorrent, content is split into mostly fixed-size pieces, allowing a client
to download data from many peers simultaneously. This makes piece size
potentially critical for performance. However, previous research efforts have
largely overlooked this parameter, opting to focus on others instead. This
paper presents the results of real experiments with varying piece sizes on a
controlled BitTorrent testbed. We demonstrate that this parameter is indeed
critical, as it determines the degree of parallelism in the system, and we
investigate optimal piece sizes for distributing small and large content. We
also pinpoint a related design trade-off, and explain how BitTorrent's choice
of dividing pieces into subpieces attempts to address it
Swarming Overlay Construction Strategies
Swarming peer-to-peer systems play an increasingly instrumental role in
Internet content distribution. It is therefore important to better understand
how these systems behave in practice. Recent research efforts have looked at
various protocol parameters and have measured how they affect system
performance and robustness. However, the importance of the strategy based on
which peers establish connections has been largely overlooked. This work
utilizes extensive simulations to examine the default overlay construction
strategy in BitTorrent systems. Based on the results, we identify a critical
parameter, the maximum allowable number of outgoing connections at each peer,
and evaluate its impact on the robustness of the generated overlay. We find
that there is no single optimal value for this parameter using the default
strategy. We then propose an alternative strategy that allows certain new peer
connection requests to replace existing connections. Further experiments with
the new strategy demonstrate that it outperforms the default one for all
considered metrics by creating an overlay more robust to churn. Additionally,
our proposed strategy exhibits optimal behavior for a well-defined value of the
maximum number of outgoing connections, thereby removing the need to set this
parameter in an ad-hoc manner
Modeling and Control of Rare Segments in BitTorrent with Epidemic Dynamics
Despite its existing incentives for leecher cooperation, BitTorrent file
sharing fundamentally relies on the presence of seeder peers. Seeder peers
essentially operate outside the BitTorrent incentives, with two caveats: slow
downlinks lead to increased numbers of "temporary" seeders (who left their
console, but will terminate their seeder role when they return), and the
copyright liability boon that file segmentation offers for permanent seeders.
Using a simple epidemic model for a two-segment BitTorrent swarm, we focus on
the BitTorrent rule to disseminate the (locally) rarest segments first. With
our model, we show that the rarest-segment first rule minimizes transition time
to seeder (complete file acquisition) and equalizes the segment populations in
steady-state. We discuss how alternative dissemination rules may {\em
beneficially increase} file acquisition times causing leechers to remain in the
system longer (particularly as temporary seeders). The result is that leechers
are further enticed to cooperate. This eliminates the threat of extinction of
rare segments which is prevented by the needed presence of permanent seeders.
Our model allows us to study the corresponding trade-offs between performance
improvement, load on permanent seeders, and content availability, which we
leave for future work. Finally, interpreting the two-segment model as one
involving a rare segment and a "lumped" segment representing the rest, we study
a model that jointly considers control of rare segments and different uplinks
causing "choking," where high-uplink peers will not engage in certain
transactions with low-uplink peers.Comment: 18 pages, 6 figures, A shorter version of this paper that did not
include the N-segment lumped model was presented in May 2011 at IEEE ICC,
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An automated framework for the management of P2P traffic in ISP infrastructures
Peer-to-Peer (P2P) is nowadays a widely used paradigm underpinning the deployment of several Internet services and applications. However, the management of P2P traffic aggregates is not an easy task for Internet Service Providers (ISPs). In this perspective, and considering an expectable proliferation in the use of such ap- plications, future networks require the development of smart mechanisms fostering an easier coexistence between P2P applications and ISP infrastructures. This paper aims to contribute for such research efforts presenting a framework incorporating useful mechanisms to be activated by network administrators, being also able to operate as an automated management tool dealing with P2P traffic aggregates.This work has been partially supported by FCT - Fundacao para a Ciencia e Tecnologia Portugal in the scope of the project: UID/CEC/00319/2013
Context aware programmable trackers for the next generation Internet
This work introduces and proposes the concept of context
aware programmable trackers for the next generation Internet. The pro-
posed solution gives ground for the development of advanced applications
based on the P2P paradigm and will foster collaborative efforts among
several network entities (e.g. P2P applications and ISPs). The proposed
concept of context aware programmable trackers allows that several peer
selection strategies might be supported by a P2P tracker entity able to
improve the peer selection decisions according with pre-defined objectives
and external inputs provided by specific services. The flexible, adaptive
and enhanced peer selection semantics that might be achieved by the
proposed solution will contribute for devising novel P2P based services
and business models for the future Internet