10,732 research outputs found
Graffiti Networks: A Subversive, Internet-Scale File Sharing Model
The proliferation of peer-to-peer (P2P) file sharing protocols is due to
their efficient and scalable methods for data dissemination to numerous users.
But many of these networks have no provisions to provide users with long term
access to files after the initial interest has diminished, nor are they able to
guarantee protection for users from malicious clients that wish to implicate
them in incriminating activities. As such, users may turn to supplementary
measures for storing and transferring data in P2P systems. We present a new
file sharing paradigm, called a Graffiti Network, which allows peers to harness
the potentially unlimited storage of the Internet as a third-party
intermediary. Our key contributions in this paper are (1) an overview of a
distributed system based on this new threat model and (2) a measurement of its
viability through a one-year deployment study using a popular web-publishing
platform. The results of this experiment motivate a discussion about the
challenges of mitigating this type of file sharing in a hostile network
environment and how web site operators can protect their resources
Smart PIN: utility-based replication and delivery of multimedia content to mobile users in wireless networks
Next generation wireless networks rely on heterogeneous connectivity technologies to support various rich media services such as personal information storage, file sharing and multimedia streaming. Due to users’ mobility and dynamic characteristics of wireless networks, data availability in collaborating devices is a critical issue. In this context Smart PIN was proposed as a personal information network which focuses on performance of delivery and cost efficiency. Smart PIN uses a novel data replication scheme based on individual and overall system utility to best balance the requirements for static data and multimedia content delivery with variable device availability due to user mobility. Simulations show improved results in comparison with other general purpose data replication schemes in terms of data availability
Exploring heterogeneity of unreliable machines for p2p backup
P2P architecture is a viable option for enterprise backup. In contrast to
dedicated backup servers, nowadays a standard solution, making backups directly
on organization's workstations should be cheaper (as existing hardware is
used), more efficient (as there is no single bottleneck server) and more
reliable (as the machines are geographically dispersed).
We present the architecture of a p2p backup system that uses pairwise
replication contracts between a data owner and a replicator. In contrast to
standard p2p storage systems using directly a DHT, the contracts allow our
system to optimize replicas' placement depending on a specific optimization
strategy, and so to take advantage of the heterogeneity of the machines and the
network. Such optimization is particularly appealing in the context of backup:
replicas can be geographically dispersed, the load sent over the network can be
minimized, or the optimization goal can be to minimize the backup/restore time.
However, managing the contracts, keeping them consistent and adjusting them in
response to dynamically changing environment is challenging.
We built a scientific prototype and ran the experiments on 150 workstations
in the university's computer laboratories and, separately, on 50 PlanetLab
nodes. We found out that the main factor affecting the quality of the system is
the availability of the machines. Yet, our main conclusion is that it is
possible to build an efficient and reliable backup system on highly unreliable
machines (our computers had just 13% average availability)
Revisiting Content Availability in Distributed Online Social Networks
Online Social Networks (OSN) are among the most popular applications in
today's Internet. Decentralized online social networks (DOSNs), a special class
of OSNs, promise better privacy and autonomy than traditional centralized OSNs.
However, ensuring availability of content when the content owner is not online
remains a major challenge. In this paper, we rely on the structure of the
social graphs underlying DOSN for replication. In particular, we propose that
friends, who are anyhow interested in the content, are used to replicate the
users content. We study the availability of such natural replication schemes
via both theoretical analysis as well as simulations based on data from OSN
users. We find that the availability of the content increases drastically when
compared to the online time of the user, e. g., by a factor of more than 2 for
90% of the users. Thus, with these simple schemes we provide a baseline for any
more complicated content replication scheme.Comment: 11pages, 12 figures; Technical report at TU Berlin, Department of
Electrical Engineering and Computer Science (ISSN 1436-9915
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