In the thesis, we study the f-cast rearrangeability of the Banyan-type network with crosstalk constraint. Let n, j, x and c be nonnegative integers with 0leq jleq n+1, 0leq xleq n and f=2^{j}. B_{n}(x,p,c) is the Banyan-type network with, 2^{n+1} inputs, 2^{n+1} outputs, x extra-stages, and each connection containing at most c crosstalk switches. We give the necessary and sufficient condictions for f-cast rearrangeable Banyan-type networks B_{n}(x,p,c). We show that (a) B_{n}(0,p,0) is f-cast rearrangeable nonblocking if and only if pgeq2^{lceil frac{n+j+1}{2} rceil}. (b) B_{n}(0,p,c) is f-cast rearrangeable nonblocking if and only if pgeq2^{lfloorfrac{n+j+1}{2} rfloor} for 1leq cleq n+1. (c) B_{n}(x,p,0) is f-cast rearrangeable nonblocking if and only if pgeqmax{2^{j+1}, 2^{lceil frac{n+j-x+1}{2} rceil}} for 0leq jleq n. (d) B_{n}(x,p,c) is 2^{n+1}-cast rearrangeable nonblocking if and only if pgeq2^{n+1} for 0leq cleq n+x+1. (e) B_{n}(x,p,n+x+1) is f-cast rearrangeable nonblocking if and only if pgeqmax{2^{j}, 2^{lfloor frac{n+j-x+1}{2} rfloor}}. (f) B_{n}(n,p,c) is f-cast rearrangeable nonblocking if and only if pgeqleft{ 2^{j} & if n+1geq jgeq n. 2^{lceil frac{j+1}{2} rceil} & if lfloor frac{j+1}{2} rfloorgeq jgeq0. for 1leq cleq n+x. (g) B_{n}(x^{prime},p,c) is f-cast rearrangeable nonblocking if and only if pgeqleft{ 2^{j} & if n+1geq jgeq n. 2^{lfloor frac{n+j-x+1}{2} rfloor} & if lfloor frac{n+j-x+1}{2} rfloorgeq jgeq0. for 1leq cleq n+x and 1leq x^{prime}leq n-1.

No description available.

The Unidata Program Center is an organization working with the University Center for Atmospheric Research (UCAR), in Colorado. It provides a broad variety of meteorological data, which is used by researchers in many real-world applications. This data is obtained from observation stations and distributed to various universities worldwide, using Unidata’s own Internet Data Distribution (IDD) system, and software called the Local Data Manager (LDM). The existing solution for data distribution has many limitations, like high end-toend latency of data delivery, increased bandwidth usage at some nodes, poor scalability for future needs and manual intervention for adjusting to changes or faults in the network topology. Since the data is used in so many applications, the impact of these limitations is often substantial. This thesis removes these limitations by suggesting improvements in the IDD system and the LDM. We present new algorithms for constructing an application-layer data distribution network. This distribution network will form the basis of the improved LDM and the IDD system, and will remove most of the limitations given above. Finally, we perform simulations and show that our algorithms achieve better average end-to-end latency as compared to that of the existing solution. We also compare the performance of our algorithms with a randomized solution. We find that for smaller topologies (where the number of nodes in the system are less than 38) the randomized solution constructs efficient distribution networks. However, if the number of nodes in the system increases (more than 38), our solution constructs efficient distribution networks than the randomized solution. We also evaluate the performance of our algorithms as the number of nodes in the system increases and as the number of faults in the system increases. We find that even if the number of faults in the system increases, the average end-to-end latency decreases, thus showing that the distribution topology does not become inefficient.

Multicast is a bandwidth efficient mechanism to provide wireless services for a group of nodes. Providing reliable wireless multicast is challenging due to channel fading. This thesis investigates cooperation among receiving nodes to enhance the reliability of wireless multicast. A time division based cooperative multicast strategy is proposed, and the optimal scheduling scheme is found to maximize the system throughput. It is shown that the optimal relay number is bounded by a threshold, and the optimal time allocation can be found using an efficient algorithm. Numerical results show that the proposed strategy can enhance network performance when the average channel condition between receiving nodes is better than that of the direct link. To provide incentive for cooperation, this thesis further studies the interactions among selfish nodes using game theoretic approaches. The cooperative multicast process is modeled as a repeated game and the desired cooperation state which satisfies the absolute fairness and the Pareto optimality criteria is found. A Worst Behavior Tit-for-Tat incentive strategy is designed to enforce cooperation and its effectiveness is studied under both the perfect and the imperfect monitoring scenarios. To address the issue of imperfect monitoring, an interval based estimation method is proposed. Simulation results show that the proposed strategy can enforce cooperation efficiently even the monitoring is imperfect. / Signal and Image Processing

IP multicast is an efficient means of sending to a group. Our protocol is built on top of the existing static hosts IP unicast and multicast forwarding services to avoid triangle routing which always occurs in Mobile IP. Relying only on the existing multicast service model and reconstructing the delivery tree every time a multicast member and/or source move is not always a good solution. By applying the ideas of bi-directional tunneled multicast [3], our protocol attempts to hide host mobility from all other members of the group. Therefore, the multicast distribution tree will not be updated for the sake of member location change. Furthermore, our protocol has near shortest delivery paths like remote subscription protocol [3]. Our protocol can also adapt to the fluctuation of both host movement and the number of mobile members (i.e., having mobility and scalability properties). According to our protocol, the tunnel convergence problem resulting from bi-directional tunneling will be solved. By changing service range ``R', we can trade off the advantages and disadvantages of both bi-directional tunneling and remote subscription (they are the extremes of RBMoM). We measure the system performance and cost in different service range, topology size and mobile population density through simulation. According to the results of our simulation, we believe our protocol has much better performance without using the current Mobile IP multicast solutions.

Wireless Ad hoc Network is a self-organizing network. It consists of many mobile nodes and it is a dynamic topology network. It is an impermanent wireless network. It is not an infrastructure-based network, and can be deployed in a short time. Therefore, it can be highly used in some emergency situations, such as, in emergency rescue actions, in military ¡Ketc. As a result, multicast plays an important role here. But before putting it into applications, we have to consider some problems such as scalability, control overhead, data delivery ratio, and routing delay. Some approaches we have learned can¡¦t resolve these problems. So, here we propose a new multicast routing protocol. It¡¦s a kind of core-based multicast protocols. First, we divide whole network into several sub-networks called as cluster, and pick up a node as the cluster core node from each cluster, and this cluster core node will manage all member nodes in this area. All cluster core nodes will connect to each other. Source node in each cluster will send messages to the it¡¦s cluster core-node and then the cluster core node will forward this message to other cluster core-nodes. Finally, the messages will be sent to the destination, member nodes of a multicast session. In this multicast routing protocol, we reduce control packets by localization and lower control overhead. With localization, every nodes only have information from near-by nodes, and this reduce the delay time of routing effectively. More, localization does not increase too much nodes when a message travels from A to B and raise the data delivery ratio. And because of localization, whole network is scalability.

No description available.

It is widely accepted that group communication (multicast) is a powerful abstraction that can be used whenever a collection of distributed processes cooperate to achieve a common goal such as load-sharing or fault-tolerance. Due to the uncertainties inherent to distributed systems (emerging from communication and/or process failures), group communication protocols have to face situations where, for instance, a sender process fails when a multicast is underway or where messages from different senders arrive in an inconsistent order at different destination processes. Further complications arise if processes belong to multiple groups. In this thesis, we make use of logical clocks [Lamport78] to develop the concept of Causal Blocks. We show that Causal Blocks provide a concise method for deducing ordering relationships between messages exchanged by processes of a group, resulting in simple methods for dealing with multiple groups. Based on the Causal Blocks representation, we present a protocol for total order message delivery which has constant and low message space overhead (Le. the protocol related information contained in a multicast message is small). We also present causal order protocols with different trade-offs between message space overhead and speed of message delivery. Furthermore, we show how the Causal Blocks representation can be used to easily deduce and maintain reliability information. Our protocols are faulttolerant: ordering and liveness are preserved even if group membership changes occur (due to failures such as process crashes or network partitions). The total order protocol, together with a novel flow control mechanism, has been implemented over a set of networked Unix workstations, and experiments carried out to analyse its performance in varied group configurations.

Com a popularização da rede global, a Internet, as aplicações colaborativas ganharam destaque, sendo imprescindíveis nas mais diversas atividades pessoais e comerciais. Os avanços tecnológicos modernos trouxeram novas demandas de aplicações, com a inclusão de diversas funcionalidades em ambientes cooperativos como, por exemplo, a distribuição de dados multimídia sobre redes de comunicação. Entretanto, quando estas ferramentas são aplicadas em ambientes coletivos com muitos usuários, o uso das mesmas é deteriorado pelas limitações da rede. Protocolos Multicast possibilitam o uso destas aplicações colaborativas em razão de proporcionarem a redução do uso da rede para atividades coletivas, possibilitando a interação com dezenas, centenas ou milhares de usuários simultaneamente. Na medida em que as ferramentas colaborativas ganham espaço entre os usuários, surge também a necessidade do emprego de segurança entre grupos de usuários. Os grupos devem ser capazes de estabelecer comunicações Multicast seguras em que apenas os membros autorizados sejam hábeis a acessar os conteúdos veiculados pelo grupo. São exemplos de aplicativos que exigem Multicast seguro: videoconferências confidenciais, sincronismo de tabelas financeiras entre matriz e filiais, distribuição de vídeo e áudio para um grupo de assinantes, dentre inúmeras outras utilizações. A proteção do conteúdo do grupo é alcançada por meio de criptografia e as chaves devem ser atualizadas quando do ingresso de novo usuário ou na hipótese de desistência de algum membro do grupo. As técnicas de gerenciamento de chaves devem ser eficientes, tanto no aspecto de segurança, quanto no que pertine ao desempenho. Devem, ainda, possibilitar a sua utilização em grupos com quantidades massivas de usuários. Os objetivos do presente trabalho são, em suma, estudar os esquemas de gerenciamento de chaves de grupo, propor uma nova técnica cujo foco seja a minimização do uso dos recursos de rede em ambientes limitados, simular os modelos avaliados pelo simulador de rede NS-2 e analisar os impactos destes esquemas em aplicações colaborativas. Para tanto, desenvolveu-se um módulo para o NS-2 que permitiu ao simulador prover suporte ao gerenciamento de chaves, e, ainda, construíram-se dois aplicativos auxiliares para a geração de cenários e análise de resultados em simulações NS-2. / With the popularization of the Internet, collaborative applications have been gaining marketshare, becoming intrinsic to a wide range of personal and commercial activities. Modern technological improvement brought new demands for these applications, such as the inclusion of new features in cooperative environments, such as the distribution of multimedia data over communication networks. However, when these tools are applied to collective environments with many users, their usability is hindered by the network limits. Multicast protocols allow the use of these collaborative applications, since they reduce the necessary network bandwidth, allowing the interaction with tens, hundreds or thousands of users simultaneously. As collaborative tools become more popular among users, there comes also the problem of security in user groups. The groups must be able to establish secure multicast communications in which only the authorized members can access the content distributed to the group. Examples of applications which demand secure multicast are confidential videoconferences, synchronization of financial tables between the headquarter and filials, distribution of video and audio to a group of users, among many others. The protection of group contents is achieved by cryptography and the keys must be updated whenever a new users joins or leaves the group. The techniques for key management must be eficient, in terms of security and performance, and also be passible of use in groups with massive amounts of users. The goals of this work are: to study the group key management systems, to propose a new technique whose focus is to minimize the use of network resources in limited environments, to simulate the models evaluated by the network simulator NS-2 and to analyze the impacts of these systems in collaborative applications. For that, a module for NS-2 has been developed that allows the simulator to provide support to key management and, moreover, two auxiliar applications were written to generate the scenarions and analyse the simulations returned by NS-2.

Com a popularização da rede global, a Internet, as aplicações colaborativas ganharam destaque, sendo imprescindíveis nas mais diversas atividades pessoais e comerciais. Os avanços tecnológicos modernos trouxeram novas demandas de aplicações, com a inclusão de diversas funcionalidades em ambientes cooperativos como, por exemplo, a distribuição de dados multimídia sobre redes de comunicação. Entretanto, quando estas ferramentas são aplicadas em ambientes coletivos com muitos usuários, o uso das mesmas é deteriorado pelas limitações da rede. Protocolos Multicast possibilitam o uso destas aplicações colaborativas em razão de proporcionarem a redução do uso da rede para atividades coletivas, possibilitando a interação com dezenas, centenas ou milhares de usuários simultaneamente. Na medida em que as ferramentas colaborativas ganham espaço entre os usuários, surge também a necessidade do emprego de segurança entre grupos de usuários. Os grupos devem ser capazes de estabelecer comunicações Multicast seguras em que apenas os membros autorizados sejam hábeis a acessar os conteúdos veiculados pelo grupo. São exemplos de aplicativos que exigem Multicast seguro: videoconferências confidenciais, sincronismo de tabelas financeiras entre matriz e filiais, distribuição de vídeo e áudio para um grupo de assinantes, dentre inúmeras outras utilizações. A proteção do conteúdo do grupo é alcançada por meio de criptografia e as chaves devem ser atualizadas quando do ingresso de novo usuário ou na hipótese de desistência de algum membro do grupo. As técnicas de gerenciamento de chaves devem ser eficientes, tanto no aspecto de segurança, quanto no que pertine ao desempenho. Devem, ainda, possibilitar a sua utilização em grupos com quantidades massivas de usuários. Os objetivos do presente trabalho são, em suma, estudar os esquemas de gerenciamento de chaves de grupo, propor uma nova técnica cujo foco seja a minimização do uso dos recursos de rede em ambientes limitados, simular os modelos avaliados pelo simulador de rede NS-2 e analisar os impactos destes esquemas em aplicações colaborativas. Para tanto, desenvolveu-se um módulo para o NS-2 que permitiu ao simulador prover suporte ao gerenciamento de chaves, e, ainda, construíram-se dois aplicativos auxiliares para a geração de cenários e análise de resultados em simulações NS-2. / With the popularization of the Internet, collaborative applications have been gaining marketshare, becoming intrinsic to a wide range of personal and commercial activities. Modern technological improvement brought new demands for these applications, such as the inclusion of new features in cooperative environments, such as the distribution of multimedia data over communication networks. However, when these tools are applied to collective environments with many users, their usability is hindered by the network limits. Multicast protocols allow the use of these collaborative applications, since they reduce the necessary network bandwidth, allowing the interaction with tens, hundreds or thousands of users simultaneously. As collaborative tools become more popular among users, there comes also the problem of security in user groups. The groups must be able to establish secure multicast communications in which only the authorized members can access the content distributed to the group. Examples of applications which demand secure multicast are confidential videoconferences, synchronization of financial tables between the headquarter and filials, distribution of video and audio to a group of users, among many others. The protection of group contents is achieved by cryptography and the keys must be updated whenever a new users joins or leaves the group. The techniques for key management must be eficient, in terms of security and performance, and also be passible of use in groups with massive amounts of users. The goals of this work are: to study the group key management systems, to propose a new technique whose focus is to minimize the use of network resources in limited environments, to simulate the models evaluated by the network simulator NS-2 and to analyze the impacts of these systems in collaborative applications. For that, a module for NS-2 has been developed that allows the simulator to provide support to key management and, moreover, two auxiliar applications were written to generate the scenarions and analyse the simulations returned by NS-2.