5,630 research outputs found
On the stability of two-chunk file-sharing systems
We consider five different peer-to-peer file sharing systems with two chunks,
with the aim of finding chunk selection algorithms that have provably stable
performance with any input rate and assuming non-altruistic peers who leave the
system immediately after downloading the second chunk. We show that many
algorithms that first looked promising lead to unstable or oscillating
behavior. However, we end up with a system with desirable properties. Most of
our rigorous results concern the corresponding deterministic large system
limits, but in two simplest cases we provide proofs for the stochastic systems
also.Comment: 19 pages, 7 figure
Citation and peer review of data: moving towards formal data publication
This paper discusses many of the issues associated with formally publishing data in academia, focusing primarily on the structures that need to be put in place for peer review and formal citation of datasets. Data publication is becoming increasingly important to the scientific community, as it will provide a mechanism for those who create data to receive academic credit for their work and will allow the conclusions arising from an analysis to be more readily verifiable, thus promoting transparency in the scientific process. Peer review of data will also provide a mechanism for ensuring the quality of datasets, and we provide suggestions on the types of activities one expects to see in the peer review of data. A simple taxonomy of data publication methodologies is presented and evaluated, and the paper concludes with a discussion of dataset granularity, transience and semantics, along with a recommended human-readable citation syntax
A Stochastic Evolutionary Growth Model for Social Networks
We present a stochastic model for a social network, where new actors may join
the network, existing actors may become inactive and, at a later stage,
reactivate themselves. Our model captures the evolution of the network,
assuming that actors attain new relations or become active according to the
preferential attachment rule. We derive the mean-field equations for this
stochastic model and show that, asymptotically, the distribution of actors
obeys a power-law distribution. In particular, the model applies to social
networks such as wireless local area networks, where users connect to
access-points, and peer-to-peer networks where users connect to each other. As
a proof of concept, we demonstrate the validity of our model empirically by
analysing a public log containing traces from a wireless network at Dartmouth
College over a period of three years. Analysing the data processed according to
our model, we demonstrate that the distribution of user accesses is
asymptotically a power-law distribution.Comment: 15 pages, 1 figur
Estimating Self-Sustainability in Peer-to-Peer Swarming Systems
Peer-to-peer swarming is one of the \emph{de facto} solutions for distributed
content dissemination in today's Internet. By leveraging resources provided by
clients, swarming systems reduce the load on and costs to publishers. However,
there is a limit to how much cost savings can be gained from swarming; for
example, for unpopular content peers will always depend on the publisher in
order to complete their downloads. In this paper, we investigate this
dependence. For this purpose, we propose a new metric, namely \emph{swarm
self-sustainability}. A swarm is referred to as self-sustaining if all its
blocks are collectively held by peers; the self-sustainability of a swarm is
the fraction of time in which the swarm is self-sustaining. We pose the
following question: how does the self-sustainability of a swarm vary as a
function of content popularity, the service capacity of the users, and the size
of the file? We present a model to answer the posed question. We then propose
efficient solution methods to compute self-sustainability. The accuracy of our
estimates is validated against simulation. Finally, we also provide closed-form
expressions for the fraction of time that a given number of blocks is
collectively held by peers.Comment: 27 pages, 5 figure
Predicting the Impact of Measures Against P2P Networks on the Transient Behaviors
The paper has two objectives. The first is to study rigorously the transient
behavior of some P2P networks whenever information is replicated and
disseminated according to epidemic-like dynamics. The second is to use the
insight gained from the previous analysis in order to predict how efficient are
measures taken against peer-to-peer (P2P) networks. We first introduce a
stochastic model which extends a classical epidemic model and characterize the
P2P swarm behavior in presence of free riding peers. We then study a second
model in which a peer initiates a contact with another peer chosen randomly. In
both cases the network is shown to exhibit a phase transition: a small change
in the parameters causes a large change in the behavior of the network. We
show, in particular, how the phase transition affects measures that content
provider networks may take against P2P networks that distribute non-authorized
music or books, and what is the efficiency of counter-measures.Comment: IEEE Infocom (2011
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,
Kyot
3D Printing: Digital Infringement & Digital Regulation
3D printing is a rapidly-growing technology that enables creation of three-dimensional solid objects made from a digital Computer Aided Design (“CAD”) file. Patent law issues are particularly relevant and uncertain in the realm of 3D printing. Thus, analysis of the Patent Act is needed to better understand direct infringement (of either the use of a 3D printer, of a CAD file, or under the doctrine of equivalents), indirect infringement, and contributory infringement in the context of 3D printing. A key issue in this analysis is whether a CAD file should be viewed as making the object itself, since 3D printing involves creation of CAD files that can print the physical object at the press of a button. As the rapidly growing field of 3D printing blurs the line between the digital and physical world, it makes sense to develop new regulations and reform existing ones. Moreover, digital regulation must address cross-border digital commerce since separate steps of the 3D printing value chain be easily performed in multiple countries or by multiple actors, and easily transmitted across borders
3D Printing: Digital Infringement & Digital Regulation
3D printing is a rapidly-growing technology that enables creation of three-dimensional solid objects made from a digital Computer Aided Design (“CAD”) file. Patent law issues are particularly relevant and uncertain in the realm of 3D printing. Thus, analysis of the Patent Act is needed to better understand direct infringement (of either the use of a 3D printer, of a CAD file, or under the doctrine of equivalents), indirect infringement, and contributory infringement in the context of 3D printing. A key issue in this analysis is whether a CAD file should be viewed as making the object itself, since 3D printing involves creation of CAD files that can print the physical object at the press of a button. As the rapidly growing field of 3D printing blurs the line between the digital and physical world, it makes sense to develop new regulations and reform existing ones. Moreover, digital regulation must address cross-border digital commerce since separate steps of the 3D printing value chain be easily performed in multiple countries or by multiple actors, and easily transmitted across borders
- …