8 research outputs found

    Analysis domain model for shared virtual environments

    Get PDF
    The field of shared virtual environments, which also encompasses online games and social 3D environments, has a system landscape consisting of multiple solutions that share great functional overlap. However, there is little system interoperability between the different solutions. A shared virtual environment has an associated problem domain that is highly complex raising difficult challenges to the development process, starting with the architectural design of the underlying system. This paper has two main contributions. The first contribution is a broad domain analysis of shared virtual environments, which enables developers to have a better understanding of the whole rather than the part(s). The second contribution is a reference domain model for discussing and describing solutions - the Analysis Domain Model

    Rendezvous Point Selection In Multicast Networks

    Get PDF
    Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2005Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2005Bu çalışmada, günümüzde kullanılan seyrek tarzlı çoklu aktarım algoritmalarının bir eksiği olan ve dinamik üyelere sahip çoklu aktarım gruplarında daha belirgin olarak gözlemlenen çoklu gönderim ağacına bağlı servis kalitesinde düşme problemi üzerinde durulmaktadır. Günümüzde kullanılan seyrek tarzlı çoklu gönderim algoritmalarında, merkez düğüm seçilmesi yönetimsel olarak yapılmaktadır ve durağan bir seçim yöntemidir. Bu nedenle, zamanla çoklu aktarım grubuna yeni alıcılar ve kaynaklar üye olduklarında ya da ayrıldıklarında, yönetimsel olarak seçilen merkez düğümlü çoklu aktarım ağaçlarında servis kalitesi düşer. Beklenen servis kalitesine tekrar ulaşabilmek için, yeni bir merkez düğüm seçilmeli ve çoklu gönderim ağacı yeni bulunan merkez düğüme göre oluşturulmalıdır. Bu çalışmada, var olan protokollerden PIM-SM çoklu gönderim protokolü ile merkez düğümün dinamik değişmesine olanak veren SCMP çoklu gönderim protokolü incelenmiş, birbirleriyle karşılaştırılmış ve merkez düğümün yer değiştirilmesinin sağladığı avantajlar ve dezavantajlar farklı tipteki ağlar ve çoklu aktarım senaryoları üzerinde denenerek belirlenmeye çalışılmıştır. Ayrıca, yapılan bu çalışma sırasında esnek bir çoklu gönderim senaryo üreteci geliştirilmiştir.In this study, the focus is on the problem of the degradation of the multicast trees used in sparse mode multicast protocols, which have dynamic members, due to inefficiency in the location of the core (rendezvous) router as time proceeds. In sparse mode multicast protocols, the rendezvous point is chosen administratively and it is a static selection method unresponsive to the changes in the network dynamics. Therefore, when new sources or receivers join/leave the multicast group by time, the quality of service(QoS) provided by the multicast tree degrades. A better rendezvous point should be selected to prevent this problem and a new multicast tree must be reconstructed rooted at the new RP. In this study, PIM-SM protocol,with static RP, is compared with SCMP protocol which enables the RP to be changed. The advantages and the disadvantages of dynamic RP relocation process is investigated for different type of networks and multicast scenarios. During this work, a flexible multicast scenario generator is developed and used.Yüksek LisansM.Sc

    Análisis de requerimiento de QoS sobre redes IP Multicast

    Get PDF
    El presente trabajo de Tesis propone presentar un análisis sobre los protocolos y mecanismos que permiten el manejo y administración de requerimientos de calidad de servicio, QoS, sobre flujos de datos IP Multicast. Dentro de estos podemos citar el caso de los requermientos aditivos como son el delay y el jitter, y requerimientos no aditivos como lo son el ancho de banda y la capacidad de almacenamiento en los buffers de los elementos de la red. El trabajo comienza con una descripción de las tecnologías IP Multicast, IP MPLS, IP Multicast sobre redes IP MPLS, Aggregated Multicast Tree, también se presenta una breve descripción de las metodologías de compresión de vídeo sobre redes IP. La Tesis culmina con un análisis de distintos protocolos y mecanismos que proporcionan el soporte de calidad de servicio sobre flujos de datos IP Multicast.Facultad de Informátic

    Mobilidade de emissores e receptores em redes com suporte de multicast

    Get PDF
    Mestrado em Engenharia Electrónica e TelecomunicaçõesEste trabalho de investigação pretende apresentar, desenvolver e avaliar uma nova solução para a mobilidade de terminais em redes IP com suporte Multicast. Tendo em conta que são cada vez mais frequentes aplicações multimédia, tais como, vídeo-conferências, IPTV, entre muitas outras, as quais requerem uma elevada largura de banda e penalizam a eficácia da rede, é necessário desenvolver trabalho nesta temática a qual se encontra ainda, nos nossos dias, pouco aprofundada. O IP Multicast consiste no envio de apenas um pacote de dados mesmo que essa informação seja pedida por vários receptores da rede. Para isso, baseiase no conceito de grupo. Os elementos da rede, que fazem parte da chamada árvore de distribuição desse grupo multicast, replicam o pacote de forma a enviar uma cópia do mesmo sempre que o caminho para os receptores divergir. Com o advento da tecnologia e tendo em conta as redes de próxima geração, verifica-se que estas são essencialmente baseadas no conceito de mobilidade. Por mobilidade entende-se a capacidade de um terminal se conectar a um outro elemento (Access Router) da rede. A solução apresentada pretende oferecer de forma eficiente e transparente suporte ao movimento dos terminais minimizando os tempos de disrupção associados. Efectuou-se uma análise às soluções existentes e tendo em conta a convergência das mesmas, para resolver problemas relacionados com mobilidade de terminais multicast, uma nova solução centrada em Agentbased é apresentada. A proposta apresentada foi testada recorrendo ao simulador NS2, demonstrando a eficiência e escalabilidade desta solução de mobilidade em redes multicast. ABSTRACT: This research work aims to produce, develop and evaluate a new solution to the mobility of terminals in IP Multicast networks. Since, multimedia applications, such as, video-conferences, IPTV, and many others, are, nowadays, more common and because these applications require a lot of bandwidth and reduce the network efficiency, it is necessary to work on this subject which is not, yet, very developed. IP Multicast allows sending only one data packet even if such information is requested by several receivers on the network. For that, it is based on the concept of group. The elements on the network, which are part of the multicast delivery tree for that group, replicate the packet, when the path to receivers differ, in order to send one copy for each one. With the advent of technology and taking into account next generation networks, we see that they are essentially based on the concept of mobility. The concept of mobility means the ability of a terminal to connect to another element (Access Router) on the network. The presented solution aims to efficiently and transparently support terminals movement minimizing the correspondent disruption time. Analyzing current solutions and taking into account their convergence, in order to solve multicast terminals mobility issues, a new Agent-based solution is presented. The proposal was tested using the simulator NS2, demonstrating the efficiency and scalability of this mobility solution in multicast networks

    A Secure and Efficient Communications Architecture for Global Information Grid Users via Cooperating Space Assets

    Get PDF
    With the Information Age in full and rapid development, users expect to have global, seamless, ubiquitous, secure, and efficient communications capable of providing access to real-time applications and collaboration. The United States Department of Defense’s (DoD) Network-Centric Enterprise Services initiative, along with the notion of pushing the “power to the edge,” aims to provide end-users with maximum situational awareness, a comprehensive view of the battlespace, all within a secure networking environment. Building from previous AFIT research efforts, this research developed a novel security framework architecture to address the lack of efficient and scalable secure multicasting in the low earth orbit satellite network environment. This security framework architecture combines several key aspects of different secure group communications architectures in a new way that increases efficiency and scalability, while maintaining the overall system security level. By implementing this security architecture in a deployed environment with heterogeneous communications users, reduced re-keying frequency will result. Less frequent re-keying means more resources are available for throughput as compared to security overhead. This translates to more transparency to the end user; it will seem as if they have a “larger pipe” for their network links. As a proof of concept, this research developed and analyzed multiple mobile communication environment scenarios to demonstrate the superior re-keying advantage offered by the novel “Hubenko Security Framework Architecture” over traditional and clustered multicast security architectures. For example, in the scenario containing a heterogeneous mix of user types (Stationary, Ground, Sea, and Air), the Hubenko Architecture achieved a minimum ten-fold reduction in total keys distributed as compared to other known architectures. Another experiment demonstrated the Hubenko Architecture operated at 6% capacity while the other architectures operated at 98% capacity. In the 80% overall mobility experiment with 40% Air users, the other architectures re-keying increased 900% over the Stationary case, whereas the Hubenko Architecture only increased 65%. This new architecture is extensible to numerous secure group communications environments beyond the low earth orbit satellite network environment, including unmanned aerial vehicle swarms, wireless sensor networks, and mobile ad hoc networks

    Consistency Algorithms and Protocols for Distributed Interactive Applications

    Full text link
    The Internet has a major impact not only on how people retrieve information but also on how they communicate. Distributed interactive applications support the communication and collaboration of people through the sharing and manipulation of rich multimedia content via the Internet. Aside from shared text editors, meeting support systems, and distributed virtual environments, shared whiteboards are a prominent example of distributed interactive applications. They allow the presentation and joint editing of documents in video conferencing scenarios. The design of such a shared whiteboard application, the multimedia lecture board (mlb), is a main contribution of this thesis. Like many other distributed interactive applications, the mlb has a replicated architecture where each user runs an instance of the application. This has the distinct advantage that the application can be deployed in a lightweight fashion, without relying on a supporting server infrastructure. But at the same time, this peer-to-peer architecture raises a number of challenging problems: First, application data needs to be distributed among all instances. For this purpose, we present the network protocol RTP/I for the standardized communication of distributed interactive applications, and a novel application-level multicast protocol that realizes efficient group communication while taking application-level knowledge into account. Second, consistency control mechanisms are required to keep the replicated application data synchronized. We present the consistency control algorithms “local lag”, “Timewarp”, and “state request”, show how they can be combined, and discuss how to provide visual feedback so that the session members are able to handle conflicting actions. Finally, late-joining participants need to be initialized with the current application state before they are able to participate in a collaborative session. We propose a novel late-join algorithm, which is both flexible and scalable. All algorithms and protocols presented in this dissertation solve the aforementioned problems in a generic way. We demonstrate how they can be employed for the mlb as well as for other distributed interactive applications

    ACADEMIC HANDBOOK (UNDERGRADUATE) COLLEGE OF ENGINEERING (CoE)

    Get PDF
    corecore