2 research outputs found

    Principais características do handoff da camada 3 em redes sem fio

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    Initially mobility was possible only between similar networks. With the arrival of new devices that offer several types of wireless network interfaces, this mobility was extended which brought new problems, such as slow and loss of connection during the transition between networks. This transition, known as handoff, can be especially complex because of the peculiarities of the various interfaces. Thus, in this work a bibliographical revision of this situation is presented and of the several proposals presents in the literature with subjects that permeate the several nets Wireless, being analyzed among others: some important concepts for the understanding and discussing with larger emphasis the problems and the improvements presented recently in the studies of Handoff, and more specifically, what includes the handoff of the layer 3 of OSI model.Inicialmente a mobilidade era possível apenas entre as redes semelhantes. Com a chegada dos novos dispositivos, que agora disponibilizavam vários tipos de interfaces de rede sem fio, esta mobilidade foi estendida trazendo novos problemas de lentidão e desconexão durante a transição entre as redes. Esta transição, conhecida como handoff, pode ser complexa principalmente devido às particularidades existentes nas diferentes interfaces dos dispositivos. Assim sendo, neste trabalho é apresentada uma revisão bibliográfica desta situação e das várias propostas presentes na literatura com questões que permeiam as diversas redes Wireless, sendo analisado entre outros: alguns conceitos importantes para o entendimento e discutindo com maior ênfase os problemas e as melhorias apresentadas recentemente nos estudos do handoff, e mais especificamente, o que abrange o handoff da camada 3 do modelo OSI

    Pro-collaborative mobile systems in next generation IP networks

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    Computing system designs of today take on either the interactive or the proactive form. Motivated by the user’s desire to make his/her computing experience more intelligent and personalised, the progression from interactive (human-centred) to proactive (human-supervised) is evident. It can be observed that current research mainly emphasises the user as the dominant focus of a user-system interaction. Consider a model that we called the opponent-process model. It contains two processes, one representing the user and the other the system, where both processes are capable of dominating each other, though working collaboratively towards a predefined task. We argue the necessity to design computing systems which are balanced in this model, such that the system process, at times, becomes the dominant process. We refer to this as the pro-collaborative design form. We dissect mobility into the notion of a nomadic user and the notion of a nomadic system. The examination into the nomadic user problem space reveals the potential for applying the pro-collaborative approach in optimising handoff management. Significant performance advantages can be obtained with our proposed S-MIP framework, based on the pro-collaborative design, when compared with established handoff latency optimisation schemes. The key differentiator lies in its indicative approach in addressing handoff ambiguity. Instead of passively anticipating through prediction as to when a mobile user might cross network boundaries (user-dominant), the system actively indicates to the user when, where and how to handoff (system-dominant). This eliminates the handoff ambiguity. Regarding the notion of a nomadic system, that is, the ability to move services offered by computing systems to arbitrary points in the Internet, we explore the idea of the dynamic extension of network services to a mobile user on-demand. Based on the pro-collaborative form, we develop the METAMORPHOSE architecture which facilitates such a dynamic service extension. By assuming the proliferation of programmable network switches and computational resources within the Internet, we re-examine how ‘loose’ service agreements between network services providers can be, to achieve such borderless moving-service offerings. The viability of the pro-collaborative form is reflected through our design and implementation of protocols and architectures which address the notion of nomadic user and nomadic system
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