8,658 research outputs found

    Control Plane Strategies for Elastic Optical Networks

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    Framework for waveband switching in multigranular optical networks: part I-multigranular cross-connect architectures

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    Optical networks using wavelength-division multiplexing (WDM) are the foremost solution to the ever-increasing traffic in the Internet backbone. Rapid advances in WDM technology will enable each fiber to carry hundreds or even a thousand wavelengths (using dense-WDM, or DWDM, and ultra-DWDM) of traffic. This, coupled with worldwide fiber deployment, will bring about a tremendous increase in the size of the optical cross-connects, i.e., the number of ports of the wavelength switching elements. Waveband switching (WBS), wherein wavelengths are grouped into bands and switched as a single entity, can reduce the cost and control complexity of switching nodes by minimizing the port count. This paper presents a detailed study on recent advances and open research issues in WBS networks. In this study, we investigate in detail the architecture for various WBS cross-connects and compare them in terms of the number of ports and complexity and also in terms of how flexible they are in adjusting to dynamic traffic. We outline various techniques for grouping wavelengths into bands for the purpose of WBS and show how traditional wavelength routing is different from waveband routing and why techniques developed for wavelength-routed networks (WRNs) cannot be simply applied to WBS networks. We also outline how traffic grooming of subwavelength traffic can be done in WBS networks. In part II of this study [Cao , submitted to J. Opt. Netw.], we study the effect of wavelength conversion on the performance of WBS networks with reconfigurable MG-OXCs. We present an algorithm for waveband grouping in wavelength-convertible networks and evaluate its performance. We also investigate issues related to survivability in WBS networks and show how waveband and wavelength conversion can be used to recover from failures in WBS networks

    Performance analysis of realistic optical time division multiplexed wavelength routed networks

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    Application of optical time division multiplexing (OTDM) in wavelength routed optical networks greatly enhances the flexibility of bandwidth assignment because OTDM provides time division sub-channels in a wavelength to match the processing speed of electronic devices. Different types of such OTDM wavelength-routed (OTDM-WR) networks, assuming different levels of sophistication of the OTDM technology, have been proposed. The performance of these OTDM-WR networks improves with the time-slot routing capability of the intermediate nodes of the network. However, as the transmission rate increases up to hundreds of gigabits per wavelength channel, electronic processing of the time slots limits the achievable performance of the OTDM-WR networks. All-optical signal processing can overcome the electronics bottleneck, but the available all-optical signal processing capability is rather limited and cannot yet utilize the full potential of time-slot routing. Even with such limitations, current technologies, such as fast wavelength converters and micro-electromechanical system (MEMS) optical switches, can significantly enhance the performance of existing wavelength-routed networks by adding the OTDM capability, albeit limited. We develop time-slot routing schemes that require fast wavelength converters only and study the performance of these schemes by simulations on Manhattan street networks and a network with the topology of the AT&T North America OC-48 fiber network.published_or_final_versio

    Ethernet - a survey on its fields of application

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    During the last decades, Ethernet progressively became the most widely used local area networking (LAN) technology. Apart from LAN installations, Ethernet became also attractive for many other fields of application, ranging from industry to avionics, telecommunication, and multimedia. The expanded application of this technology is mainly due to its significant assets like reduced cost, backward-compatibility, flexibility, and expandability. However, this new trend raises some problems concerning the services of the protocol and the requirements for each application. Therefore, specific adaptations prove essential to integrate this communication technology in each field of application. Our primary objective is to show how Ethernet has been enhanced to comply with the specific requirements of several application fields, particularly in transport, embedded and multimedia contexts. The paper first describes the common Ethernet LAN technology and highlights its main features. It reviews the most important specific Ethernet versions with respect to each application field’s requirements. Finally, we compare these different fields of application and we particularly focus on the fundamental concepts and the quality of service capabilities of each proposal

    Trends in Computer Network Modeling Towards the Future Internet

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    This article provides a taxonomy of current and past network modeling efforts. In all these efforts over the last few years we see a trend towards not only describing the network, but connected devices as well. This is especially current given the many Future Internet projects, which are combining different models, and resources in order to provide complete virtual infrastructures to users. An important mechanism for managing complexity is the creation of an abstract model, a step which has been undertaken in computer networks too. The fact that more and more devices are network capable, coupled with increasing popularity of the Internet, has made computer networks an important focus area for modeling. The large number of connected devices creates an increasing complexity which must be harnessed to keep the networks functioning. Over the years many different models for computer networks have been proposed, and used for different purposes. While for some time the community has moved away from the need of full topology exchange, this requirement resurfaced for optical networks. Subsequently, research on topology descriptions has seen a rise in the last few years. Many different models have been created and published, yet there is no publication that shows an overview of the different approaches.

    Burst switched optical networks supporting legacy and future service types

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    Focusing on the principles and the paradigm of OBS an overview addressing expectable performance and application issues is presented. Proposals on OBS were published over a decade and the presented techniques spread into many directions. The paper comprises discussions of several challenges that OBS meets, in order to compile the big picture. The OBS principle is presented unrestricted to individual proposals and trends. Merits are openly discussed, considering basic teletraffic theory and common traffic characterisation. A more generic OBS paradigm than usual is impartially discussed and found capable to overcome shortcomings of recent proposals. In conclusion, an OBS that offers different connection types may support most client demands within a sole optical network layer

    NASA JSC neural network survey results

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    A survey of Artificial Neural Systems in support of NASA's (Johnson Space Center) Automatic Perception for Mission Planning and Flight Control Research Program was conducted. Several of the world's leading researchers contributed papers containing their most recent results on artificial neural systems. These papers were broken into categories and descriptive accounts of the results make up a large part of this report. Also included is material on sources of information on artificial neural systems such as books, technical reports, software tools, etc
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