Marinho P. Barcellos

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This paper discusses the design and implementation of Simmcast, an object-oriented framework for network simulation with specific support for group communication. The design of the framework is focused towards simplicity and extensibility. The aim is to allow a spectrum of experiments ranging from evaluation of abstract group communication models to(More)
Reliable sender-based one-to-many protocols do not scale well due mainly to implosion caused by excessive rate of feedback packets arriving from receivers. We show that this problem can be circumvented by making the sender poll the receivers at carefully planned timing instants, so that the arrival rate of feedback packets is not large enough to cause(More)
In its simplest form, multicast communication is the process of sending data packets from a source to multiple destinations in the same logical multicast group. IP multicast allows the efficient transport of data through wide-area networks, and its potentially great value for the Grid has been highlighted recently by a number of research groups. In this(More)
BitTorrent has become one of the most popular Internet applications, given the number of users and the fraction of the Internet traffic it consumes. Its wide adoption has exposed some potential problems, like selfish peer behavior. Related research efforts so far have focused on modeling the dynamics of swarms, as well as devising incentive mechanisms that(More)
BitTorrent is a P2P file-sharing protocol that can be used to efficiently distribute files such as software updates and digital content to very large numbers of users. In a previous paper, we have shown that vulner-abilities can be exploited to launch Denial-of-Service attacks against BitTorrent swarms, which can substantially increase download times and(More)
BitTorrent is probably the most popular file sharing protocol nowadays. Since it is a complex protocol which was created mostly as an engineering effort, there have been attempts to evaluate and understand the behavior of Bit-Torrent, exposing drawbacks and identifying opportunities for improvement. Simulation(al) and experimental evaluation are two(More)
In many aspects of human activity, there has been a continuous struggle between the forces of centralization and decentralization. Computing exhibits the same phenomenon; we have gone from mainframes to PCs and local networks in the past, and over the last decade we have seen a centralization and consolidation of services and applications in data centers(More)