47,965 research outputs found
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 torrents
Securing Peer-to-Peer Overlay Networks
Overlay networks are virtual networks, which exist on top of the current Inter net architecture, and are used in support of peer-to-peer (P2P) applications. The virtualization provides overlays with the ability to create large, scalable, decentral ized networks with efficient routing. Many implementations of overlay networks have come out of academic research. Each provides a unique structure and routing configuration, aimed at increasing the overall network efficiency for a particular ap plication. However, they are all threatened by a similar set of severe vulnerabilities.
I explore some of these security deficiencies of overlay network designs and pro pose a new overlay network security framework Phyllo. This framework aims to mitigate all of the targeted security problems across a majority of the current overlay implementations, while only requiring minimal design changes. In order to demonstrate the validity of Phyllo, it was implemented on top of the Pastry overlay architecture. The performance and security metrics of the network with the pro posed framework are evaluated against those of the original in order to demonstrate the feasibility of Phyllo
Redes overlay peer-to-peer baseadas em SIP
As redes Peer-to-peer (P2P) tem vindo a ganhar popularidade na internet, devido ao aumento do número de utilizadores e de serviços de natureza distribuída, como a partilha de ficheiros, e as chamadas de voz sobre IP (VoIP). A criação deste tipo de redes, baseando-se em soluções abertas como o SIP, pode facilitar a criação de novos tipos de serviços, assim como
permitir uma mais fácil integração de diferentes serviços.
Neste trabalho foi desenvolvida uma implementação JAVA, capaz de criar redes P2PSIP com um ou dois níveis hierárquicos.
A comunicação entre os nós da rede P2P, ´é feita através de um protocolo totalmente baseado em SIP. Como algoritmos a utilizar
pelo overlay P2P, foram implementados o algoritmo Chord e EpiChord. Para comprovar o funcionamento da implementação JAVA, foram efectuados testes num ambiente real, recorrendo a
uma topologia de rede emulada com o CORE
Physics-inspired Performace Evaluation of a Structured Peer-to-Peer Overlay Network
In the majority of structured peer-to-peer overlay networks a graph
with a desirable topology is constructed. In most cases, the graph is
maintained by a periodic activity performed by each node in the graph
to preserve the desirable structure in face of the continuous change
of the set of nodes. The interaction of the autonomous periodic
activities of the nodes renders the performance analysis of such
systems complex and simulation of scales of interest can be
prohibitive. Physicists, however, are accustomed to dealing with
scale by characterizing a system using intensive variables,
i.e. variables that are size independent. The approach has proved its
usefulness when applied to satisfiability theory. This
work is the first attempt to apply it in the area of distributed
systems. The contribution of this paper is two-fold. First, we
describe a methodology to be used for analyzing the performance of
large scale distributed systems. Second, we show how we applied the
methodology to find an intensive variable that describe the
characteristic behavior of the Chord overlay network, namely, the
ratio of the magnitude of perturbation of the network (joins/failures)
to the magnitude of periodic stabilization of the network
Converging an Overlay Network to a Gradient Topology
In this paper, we investigate the topology convergence problem for the
gossip-based Gradient overlay network. In an overlay network where each node
has a local utility value, a Gradient overlay network is characterized by the
properties that each node has a set of neighbors with the same utility value (a
similar view) and a set of neighbors containing higher utility values (gradient
neighbor set), such that paths of increasing utilities emerge in the network
topology. The Gradient overlay network is built using gossiping and a
preference function that samples from nodes using a uniform random peer
sampling service. We analyze it using tools from matrix analysis, and we prove
both the necessary and sufficient conditions for convergence to a complete
gradient structure, as well as estimating the convergence time and providing
bounds on worst-case convergence time. Finally, we show in simulations the
potential of the Gradient overlay, by building a more efficient live-streaming
peer-to-peer (P2P) system than one built using uniform random peer sampling.Comment: Submitted to 50th IEEE Conference on Decision and Control (CDC 2011
Peer to peer multicast overlay for smart content delivery
Tese de Mestrado Integrado. Engenharia Informática e Computação. Faculdade de Engenharia. Universidade do Porto. 201
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