25 research outputs found

    A Fairness Algorithm for High-speed Networks based on a Resilient Packet Ring Architecture

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    IEEE is currently standardizing a spatial reuse ring topology network called the Resilient Packet Ring (RPR, IEEE P802.17). The goal of the RPR development is to make a LAN/MAN standard, but also WANs are discussed. A ring network needs a fairness algorithm that regulates each stations access to the ring. The RPR fairness algorithm is currently being developed with mostly long distances between stations in mind. In this paper we discuss the feedback aspects of this algorithm and how it needs to be changed in order to give good performance if and when RPR is used for high-speed networks and LANs with shorter distances between stations. We discuss different architectural parameters including buffers sizes and distances between stations. We suggest the use of triggers instead of timers to meet the response requirements of high-speed networks. We have developed a discrete event simulator in the programming language Java. The proposed improvements are compared and evaluated using a ring network model that we have built using our simulator. (c) 2002 IEEE. Personal use of this material is permitted

    Design and Analysis of RT-Ring: A Protocol for Supporting Real-Time Communications

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    Distributed applications with quality of service (QoS) requirements are more and more used in several areas (e.g., automated factory networks, embedded systems, conferencing systems). These applications produce a type of traffic with hard timing requirements, i.e., transmissions must be completed within specified deadlines. To handle these transmissions, the communication system must use real-time protocols to provide a communication service that is able to satisfy the QoS requirements of the distributed applications. In this paper, we propose a new real-time protocol, called RT-Ring, able to support transmissions of both real-time and generic traffic over a ring network. RT-Ring provides both network guarantees and high network resource utilization, while ensuring the compatibility with the emerging differentiated service architectures. Network guarantees are fully proved and high network utilization is highlighted by a comparative study with the FDDI protocol. This comparison shows that RT-Ring network capacities are greater than the corresponding FDDI capacities. In fact, by assuming the FDDI frames with a length equal to the RT-Ring slot size and by using the same traffic load we show that the capacities of FDDI are equal to the lower bound capacities of RT-Ring. Index Terms Real-time protocol, quality of service (QoS) traffic, worst case analysis

    Multi-MetaRing fairness control in a WDM folded-bus architecture

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    The paper deals with fairness issues in a slotted, single-hop, WDM (Wavelength Division Multiplexing) optical architecture, based on a folded bus topology, previously proposed as a broadband access system or as a metro network. The peculiar fairness problem arising in this folded bus based architecture is addressed and an extension of the MetaRing protocol to the WDM scenario, named Multi-MetaRing, is proposed. Feasible Multi-MetaRing strategies are defined and analyzed. Both fair access and high aggregate network throughput can be achieved with a low complexity distributed access protocol by properly handling node access through all WDM channel

    Fair and efficient transmission over GBPS dual ring networks

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    The advances in fiber optics technology provide large bandwidth and enable the support of a wide variety of services. New network architectures have been proposed, such as Metaring and Distributed Queue Dual Bus (DQDB), that try to take advantage of the new capabilities. Because of the very small packet transmission time relative to the feedback time a challenging issue in high speed networks is the efficient and fair share of the channel bandwidth among the competing users. In this thesis we first investigate and compare the performance of the Global and Local Fairness Mechanisms (GFM and LFM, respectively). They have been proposed recently for fair bandwidth allocation in high speed dual ring networks employing destination release. (a slot that has been read by its destination is immediately released and can be used again by other nodes). We show the sensitivity of both mechanisms to various system parameters, such as channel bandwidth and ring latency. We introduce the Dynamic Medium Access Control Mechanism (DMAC) which does not suffer from the limitations of GFM and LFM, introduces fairness in a very effective and efficient way, and is insensitive to the network parameters

    Fairness protocols for optical ring networks

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    Orientadores: Nelson Luis Saldanha da Fonseca, Marcos Rogerio SalvadorDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de ComputaçãoResumo: Em redes ópticas em anel com slotting, slots de tamanhos fixos circulam continuamente pelo anel transportando pacotes de dados entre os nós. Em tais redes, um slot, ocupado com pacotes de um nó, tem seu conteúdo removido somente pelo próprio nó de origem. Entretanto, é possível remover o conteúdo do slot no nó de destino, técnica conhecida como remoção no destino, o que permite que um slot seja utilizado mais de uma vez em cada ciclo, o que é conhecido como reutilização espacial. Esta prática aumenta consideravelmente a vazão do anel. Entretanto, se o acesso aos slots não for controlado, injustiças podem ocorrer devido a oportunidades desbalanceadas de acesso ao meio oferecido aos nós. Para previnir um acesso injusto ao meio, a ocupação dos slots é controlada pelos protocolos de controle de acesso ao meio (MAC), que distribuem os slots entre os nós, oferecendo oportunidades justas do acesso ao meio. Os protocolos MAC seguem políticas de justiça, que são regras que determinam a divisão justa dos recursos do anel. Os protocolos MAC que oferecem justiça entre nós são comuns na literatura, entretanto, estes protocolos ignoram a justiça entre conexões TCP (Transmission Control Protocol)o Nesta dissertação, três novos protocolos são apresentados: LCR-SD, TCP-Fair e RVQ. O protocolo LCR-SD distribui a largura de banda baseada na política de justiça entre pares origem-destino, o protocolo RVQ oferece justiça entre conexões TCP e o protocolo de TCP -Fair oferece a justiça entre as conexões TCP mantendo a justiça entre nós. Os protocolos são comparados através de simulações realizadas no Network Simulator (NS-2). Resultados indicam que os protocolos LCR-SD, TCP-Fair e RVQ oferecem uma vazão superior ao protocolo Metaring. Além disso, apresenta-se um estudo sobre o impacto do tamanho dos slots no transporte de tráfego da InternetAbstract: In slotted ring networks, slots of fixed size continuously circulate the ring transferring data packets between nodes. In such networks, a slot occupied by packets from one node, has its content removed only by the source node. However, it is possible to remove the packet content in the destination node, technique known as destination removal, which allows a slot to be used more than once in each cycle, leading to spatial reuse, which increases considerably the throughput. However, if the access to the slots is not regulated, unfairness may occur due to unbalanced medium access opportunities offered to the nodes. To prevent unfair access to the medium, the occupation of the slots is regulated by a Medium Access Control protocol (MAC), which distributes the slots among the nodes, offering fair access opportunities to the medium. MAC protocols comply with fairness policies, which are rules that determine the fair distribution of the ring resources. MAC protocols that offer fairness among nodes are common in the literature, however, these protocols ignore the fairness among TCP (Transmission Control Protocol) connections. In this dissertation, three new protocols are presented: LCR-SD, TCP-Fair and RVQ. The LCR-SD protocol distributes the bandwidth based on the source-destination node fairness policy, the RVQ protocol offers fairness among TCP connections and the TCP-Fair protocol offers fairness among TCP connections and maintains fairness among nodes. The protocols are compared through simulations using the Network Simulator (NS- 2). Results indicate that the protocols LCR-SD, TCP-Fair and RVQ offer a superior throughput compared to the Metaring protocol. Moreover, a study on the impact of the slot size on the transport of Internet traffic is presented.MestradoRedes de ComputadoresMestre em Ciência da Computaçã

    Throughput-Delay Trade-Offs in Slotted WDM Ring Networks

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    International audienceWe analyse the throughput-delay trade-offs that arise in an optical burst-switched slotted WDM ring, where each node can transmit and receive on a subset of the available wavelengths. Specifically, we compare SWING, an access control scheme that combines opportunistic transmission and dynamic reservations, with a purely opportunistic access scheme. By means of analysis, we highlight the shortcomings of the opportunistic scheme in terms of load balancing and fairness. We then evaluate the performance of both schemes by simulation under several traffic scenarios and show that SWING yields a good throughput-delay trade-off
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