99 research outputs found

    From Mutually Non-Blocking to Switched Non-Blocking DES

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    National audienceThe mutually non-blocking property of discrete-event systems has been introduced by Fabian and Kumar (1997). In this paper, we extend the property of mutually non-blocking from 2 to 3 elements. We also propose a definition of switched non-blocking system, and we show the mutually non-blocking property is included in the switched non-blocking property. We illustrate the result with an example of protocol conversion with switched specification.La propriété de système à événements discrets mutuellement non-bloquants a été introduite par Fabian and Kumar (1997). Dans ce papier, nous proposons une extension de cette propriété de 2 à 3 éléments. Nous donnons ensuite une définition de système non-bloquant par commutations, et nous montrons que la propriété "mutuellement non-bloquant" est incluse dans celle de "non-bloquant par commutations". Nous illustrons ce resultat à travers un exemple de système de conversion de protocole, dans lequel le protocole commute entre deux spécifications

    Architecture, design, and modeling of the OPSnet asynchronous optical packet switching node

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    An all-optical packet-switched network supporting multiple services represents a long-term goal for network operators and service providers alike. The EPSRC-funded OPSnet project partnership addresses this issue from device through to network architecture perspectives with the key objective of the design, development, and demonstration of a fully operational asynchronous optical packet switch (OPS) suitable for 100 Gb/s dense-wavelength-division multiplexing (DWDM) operation. The OPS is built around a novel buffer and control architecture that has been shown to be highly flexible and to offer the promise of fair and consistent packet delivery at high load conditions with full support for quality of service (QoS) based on differentiated services over generalized multiprotocol label switching

    Design of Routers for Optical Burst Switched Networks

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    Optical Burst Switching (OBS) is an experimental network technology that enables the construction of very high capacity routers using optical data paths and electronic control. In this dissertation, we study the design of network components that are needed to build an OBS network. Specifically, we study the design of the switches that form the optical data path through the network. An OBS network that switches data across wavelength channels requires wave-length converting switches to construct an OBS router. We study one particular design of wavelength converting switches that uses tunable lasers and wavelength grating routers. This design is interesting because wavelength grating routers are passive devices and are much less complex and hence less expensive than optical crossbars. We show how the routing problem for these switches can be formulated as a combinatorial puzzle or game, in which the design of the game board determines key performance characteristics of the switch. In this disertation, we use this formu-lation to facilitate the design of switches and associated routing strategies with good performance. We then introduce time sliced optical burst switching (TSOBS), a variant of OBS that switches data in the time domain rather that the wavelength domain. This eliminates the need for wavelength converters, the largest single cost component of systems that switch in the wavelength domain. We study the performance of TSOBS networks and discuss various design issues. One of the main components that is needed to build a TSOBS router is an optical time slot interchanger (OTSI). We explore various design options for OTSIs. Finally, we discuss the issues involved in the design of network interfaces that transmit the data from hosts that use legacy protocols into a TSOBS network. Ag-gregation and load balancing are the main issues that determine the performance of a TSOBS network and we develop and evaluate methods for both

    Electronic and photonic switching in the atm era

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    Broadband networks require high-capacity switches in order to properly manage large amounts of traffic fluxes. Electronic and photonic technologies are being used to achieve this objective both allowing different multiplexing and switching techniques. Focusing on the asynchronous transfer mode (ATM), the inherent different characteristics of electronics and photonics makes different architectures feasible. In this paper, different switching structures are described, several ATM switching architectures which have been recently implemented are presented and the implementation characteristics discussed. Three diverse points of view are given from the electronic research, the photonic research and the commercial switches. Although all the architectures where successfully tested, they should also follow different market requirements in order to be commercialised. The characteristics are presented and the architectures projected over them to evaluate their commercial capabilities.Peer ReviewedPostprint (published version

    A component-based collaboration infrastructure

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    Groupware applications allow geographically distributed users to collaborate on shared tasks. However, it is widely recognized that groupware applications are expensive to build due to coordination services and group dynamics, neither of which is present in single-user applications. Previous collaboration transparency systems reuse existing single-user applications as a whole for collaborative work, often at the price of inflexible coordination. Previous collaboration awareness systems, on the other hand, provide reusable coordination services and multi-user widgets, but often with two weaknesses: (1) the multi-user widgets provided are special-purpose and limited in number, while no guidelines are provided for developing multi-user interface components in general; and (2) they often fail to reach the desired level of flexibility in coordination by tightly binding shared data and coordination services. In this dissertation, we propose a component-based approach to developing group- ware applications that addresses the above two problems. To address the first prob- lem, we propose a shared component model for modeling data and graphic user inter- face(GUI) components of groupware applications. As a result, the myriad of existing single-user components can be re-purposed as shared GUI or data components. An adaptation tool is developed to assist the adaptation process. To address the second problem, we propose a coordination service framework which systematically model the interaction between user, data, and coordination protocols. Due to the clean separation of data and control and the capability to dynamically "glue" them together, the framework provides reusable services such as data distribution, persistence, and adaptable consistency control. The association between data and coordination services can be dynamically changed at runtime. An Evolvable and eXtensible Environment for Collaboration (EXEC) is built to evaluate the proposed approach. In our experiments, we demonstrate two benefits of our approach: (1) a group of common groupware features adapted from existing single- user components are plugged in to extend the functionalities of the environment itself; and (2)coordination services can be dynamically attached to and detached from these shared components at different granules to support evolving collaboration needs

    A Discrete Event Systems Approach for Protocol Conversion

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    A Protocol mismatch occurs when heterogeneous networks try to communicate with each other. Such mismatches are inevitable due to the proliferation of a multitude of networking architectures, hardware, and software on one hand, and the need for global connectivity on the other hand. In order to circumvent this problem the solution of protocol conversion has been proposed. In this paper we present a systematic approach to protocol conversion using the theory of supervisory control of discrete event systems, which was partially first addressed by Inan. We study the problem of designing a converter for a given mismatched pair of protocols, using their specifications, and the specifications for the channel and the user services. We introduce the notion of converter languages and use it to obtain a necessary and sufficient condition for the existence of protocol converter and present an effective algorithm for computing it whenever it exists

    On-board B-ISDN fast packet switching architectures. Phase 2: Development. Proof-of-concept architecture definition report

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    For the next-generation packet switched communications satellite system with onboard processing and spot-beam operation, a reliable onboard fast packet switch is essential to route packets from different uplink beams to different downlink beams. The rapid emergence of point-to-point services such as video distribution, and the large demand for video conference, distributed data processing, and network management makes the multicast function essential to a fast packet switch (FPS). The satellite's inherent broadcast features gives the satellite network an advantage over the terrestrial network in providing multicast services. This report evaluates alternate multicast FPS architectures for onboard baseband switching applications and selects a candidate for subsequent breadboard development. Architecture evaluation and selection will be based on the study performed in phase 1, 'Onboard B-ISDN Fast Packet Switching Architectures', and other switch architectures which have become commercially available as large scale integration (LSI) devices

    Current Transducer for IoT Applications

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    The evolution of communication technology and the reduction of its costs have driven several advances in measurement systems. Points that could not be measured before can now be monitored. Points with difficulty to reach or with major security restrictions can begin to have their quantities measured and informed to control centers. This chapter presents one of these evolutions showing a current transducer (CT), which can measure this magnitude, make an initial treatment of the signal, and transmit it to a panel or control center. Besides, this current transducer does not require an energy source to operate, being self-powered by the current it is measuring. Because it is inexpensive, it can be spread through the facilities, supplying the current at various points of the observed electrical network. With signal treatment, useful information can be inserted in this device so that it informs already preprocessed elements to reading devices, becoming part of the world of IoT. This article presents its use in motor condition monitoring at the Pimental hydroelectric power plant

    Time-Synchronized Optical Burst Switching

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    Optical Burst Switching was recently introduced as a protocol for the next generation optical Wavelength Division Multiplexing (WDM) network. Currently, in legacy Optical Circuit Switching over the WDM network, the highest bandwidth utilization cannot be achieved over the network. Because of its physical complexities and many technical obstacles, the lack of an optical buffer and the inefficiency of optical processing, Optical Packet Switching is difficult to implement. Optical Burst Switching (OBS) is introduced as a compromised solution between Optical Circuit Switching and Optical Packet Switching. It is designed to solve the problems and support the unique characteristics of an optical-based network. Since OBS works based on all-optical switching techniques, two major challenges in designing an effective OBS system have to be taken in consideration. One of the challenges is the cost and complexities of implementation, and another is the performance of the system in terms of blocking probabilities. This research proposes a variation of Optical Burst Switching called Time-Synchronized Optical Burst Switching. Time-Synchronized Optical Burst Switching employs a synchronized timeslot-based mechanism that allows a less complex physical switching fabric to be implemented, as well as to provide an opportunity to achieve better resource utilization in the network compared to the traditional Optical Burst Switching

    IP multicast over WDM networks

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