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)
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)
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)
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)
The widespread adoption of P2P applications in environments beyond ordinary file sharing demands the fulfillment of several security requirements. Important steps have been taken towards security in P2P systems, with relevant mechanisms being proposed in the past to address specific vulnerabilities. However, existing approaches lack flexibility, since they(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)
Grid computing can be characterized as a distributed infrastructure that is a collection of computing resources within or across locations that are aggregated to act as a unified processing resource. In some of the anticipated future grid applications, the same data will be transmitted to multiple sites. It is widely accepted that this can be, in theory,(More)
Simulation has been of paramount importance to the development of novel Internet protocols. Such an approach typically focuses on one of three domains: wireless and other link-layer technologies, routing protocols, and transport-layer mechanisms and protocols. Existing techniques can tackle well simulation at layers 2, 3 and 4 of the TCP/IP architecture,(More)