2,698 research outputs found

    A Survey of Green Networking Research

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    Reduction of unnecessary energy consumption is becoming a major concern in wired networking, because of the potential economical benefits and of its expected environmental impact. These issues, usually referred to as "green networking", relate to embedding energy-awareness in the design, in the devices and in the protocols of networks. In this work, we first formulate a more precise definition of the "green" attribute. We furthermore identify a few paradigms that are the key enablers of energy-aware networking research. We then overview the current state of the art and provide a taxonomy of the relevant work, with a special focus on wired networking. At a high level, we identify four branches of green networking research that stem from different observations on the root causes of energy waste, namely (i) Adaptive Link Rate, (ii) Interface proxying, (iii) Energy-aware infrastructures and (iv) Energy-aware applications. In this work, we do not only explore specific proposals pertaining to each of the above branches, but also offer a perspective for research.Comment: Index Terms: Green Networking; Wired Networks; Adaptive Link Rate; Interface Proxying; Energy-aware Infrastructures; Energy-aware Applications. 18 pages, 6 figures, 2 table

    Investigation of the tolerance of wavelength-routed optical networks to traffic load variations.

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    This thesis focuses on the performance of circuit-switched wavelength-routed optical network with unpredictable traffic pattern variations. This characteristic of optical networks is termed traffic forecast tolerance. First, the increasing volume and heterogeneous nature of data and voice traffic is discussed. The challenges in designing robust optical networks to handle unpredictable traffic statistics are described. Other work relating to the same research issues are discussed. A general methodology to quantify the traffic forecast tolerance of optical networks is presented. A traffic model is proposed to simulate dynamic, non-uniform loads, and used to test wavelength-routed optical networks considering numerous network topologies. The number of wavelengths required and the effect of the routing and wavelength allocation algorithm are investigated. A new method of quantifying the network tolerance is proposed, based on the calculation of the increase in the standard deviation of the blocking probabilities with increasing traffic load non-uniformity. The performance of different networks are calculated and compared. The relationship between physical features of the network topology and traffic forecast tolerance is investigated. A large number of randomly connected networks with different sizes were assessed. It is shown that the average lightpath length and the number of wavelengths required for full interconnection of the nodes in static operation both exhibit a strong correlation with the network tolerance, regardless of the degree of load non-uniformity. Finally, the impact of wavelength conversion on network tolerance is investigated. Wavelength conversion significantly increases the robustness of optical networks to unpredictable traffic variations. In particular, two sparse wavelength conversion schemes are compared and discussed: distributed wavelength conversion and localized wavelength conversion. It is found that the distributed wavelength conversion scheme outperforms localized wavelength conversion scheme, both with uniform loading and in terms of the network tolerance. The results described in this thesis can be used for the analysis and design of reliable WDM optical networks that are robust to future traffic demand variations

    A congestion aware ant colony optimisation-based routing and wavelength assignment algorithm for transparent flexi-grid optical burst switched networks

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    Optical Burst Switching (OBS) over transparent exi-grid optical networks, is considered a potential solution to the increasing pressure on backbone networks due to the increase in internet use and widespread adoption of various high bandwidth applications. Both technologies allow for more e cient usage of a networks resources. However, transmissions over exi-grid networks are more susceptible to optical impairments than transmissions made over xed-grid networks, and OBS suers from high burst loss due to contention. These issues need to be solved in order to reap the full benets of both technologies. An open issue for OBS whose solution would mitigate both issues is the Routing and Wavelength Assignment (RWA) algorithm. Ant Colony Optimisation (ACO) is a method of interest for solving the RWA problem on OBS networks. This study aims to improve on current dynamic ACO-based solutions to the Routing and Wavelength Assignment problem on transparent exi-grid Optical Burst Switched networks

    Application of advanced on-board processing concepts to future satellite communications systems

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    An initial definition of on-board processing requirements for an advanced satellite communications system to service domestic markets in the 1990's is presented. An exemplar system architecture with both RF on-board switching and demodulation/remodulation baseband processing was used to identify important issues related to system implementation, cost, and technology development

    On the Conditions that Justify Dynamic Reconfigurability in WDM-TDMA Optical Access Networks

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    [EN] In a passive optical network with a hybrid wavelength division multiplexing time division multiple-access scheme, implementing reconfigurable wavelength assignment is complex; hence the need to determine the conditions for which the capacity improvements justify requiring reconfigurability over adopting a more inexpensive fixed wavelength assignment. Fixed and reconfigurable approaches to wavelength assignment are modeled and evaluated under nonstationary traffic conditions. The performance improvement is obtained in terms of bit rate gain relative to the nominal bandwidth and depends on the number of wavelength channels as well as the magnitude of the load offered by the optical network units. In addition, frame delay and frame loss in relation to the bit rate performance are obtained for Pareto and exponentially distributed traffic. Simulations show that when introducing reconfigurability, typical peak bit rate gains with respect to the fixed case are 17%, and maxima of 175% are potentially possible when traffic demands are particularly uneven.This work was supported by the EC 7th Framework Program: Architectures for fLexible Photonic Home and Access networks (ALPHA), under contract ICT CP-IP 212 352, from the Generalitat of Valencia under contract ACOMP/2010/196. The authors thank the Performability Engineering Research Group (PERFORM) at the University of Illinois at Urbana-Champaign for developing the software tool Mobius.García Roger, D.; Artundo Martínez, I.; Ortega Tamarit, B. (2011). On the Conditions that Justify Dynamic Reconfigurability in WDM-TDMA Optical Access Networks. Journal of Optical Communications and Networking. 3(4):259-271. https://doi.org/10.1364/JOCN.3.000259S25927134A highly flexible and efficient passive optical network employing dynamic wavelength allocation. (2005). Journal of Lightwave Technology, 23(1), 277-286. doi:10.1109/jlt.2004.838811Maier, M., Herzog, M., & Reisslein, M. (2007). STARGATE: the next evolutionary step toward unleashing the potential of WDM EPONs [Topics in Optical Communications]. IEEE Communications Magazine, 45(5), 50-56. doi:10.1109/mcom.2007.358848Urban, P. J., Huiszoon, B., Roy, R., de Laat, M. M., Huijskens, F. M., Klein, E. J., … de Waardt, H. (2009). High-Bit-Rate Dynamically Reconfigurable WDM–TDM Access Network. Journal of Optical Communications and Networking, 1(2), A143. doi:10.1364/jocn.1.00a143Glatty, R., Guignard, P., & Chanclou, P. (2009). Fair Resource Distribution Within the Flexible WDMA/TDMA Optical Access Network Based on GPON Infrastructure. Journal of Optical Communications and Networking, 1(2), A17. doi:10.1364/jocn.1.000a17Roy, R., Manhoudt, G., & van Etten, W. (2008). Optical-router-based dynamically reconfigurable photonic access network. Journal of Optical Networking, 8(1), 51. doi:10.1364/jon.8.000051Koonen, T., Steenbergen, K., Janssen, F., & Wellen, J. (2001). Photonic Network Communications, 3(3), 297-306. doi:10.1023/a:1011411600793Homa, J., & Bala, K. (2008). ROADM Architectures and Their Enabling WSS Technology. IEEE Communications Magazine, 46(7), 150-154. doi:10.1109/mcom.2008.4557058Strasser, T., & Taylor, J. (2008). ROADMS Unlock the Edge of the Network. IEEE Communications Magazine, 46(7), 146-149. doi:10.1109/mcom.2008.4557057Leland, W. E., Taqqu, M. S., Willinger, W., & Wilson, D. V. (1994). On the self-similar nature of Ethernet traffic (extended version). IEEE/ACM Transactions on Networking, 2(1), 1-15. doi:10.1109/90.282603Kramer, G., Mukherjee, B., & Pesavento, G. (2002). Photonic Network Communications, 4(1), 89-107. doi:10.1023/a:1012959023043Skubic, B., Jiajia Chen, Ahmed, J., Wosinska, L., & Mukherjee, B. (2009). A comparison of dynamic bandwidth allocation for EPON, GPON, and next-generation TDM PON. IEEE Communications Magazine, 47(3), S40-S48. doi:10.1109/mcom.2009.4804388Papadimitriou, G. I., & Pomportsis, A. S. (1999). Self-adaptive TDMA protocols for WDM star networks: a learning-automata-based approach. IEEE Photonics Technology Letters, 11(10), 1322-1324. doi:10.1109/68.789731Linardakis, C., Leligou, H. C., Stavdas, A., & Angelopoulos, J. D. (2005). Using explicit reservations to arbitrate access to a metropolitan system of slotted interconnected rings combining TDMA and WDMA. Journal of Lightwave Technology, 23(4), 1576-1585. doi:10.1109/jlt.2005.844198Kanonakis, K., & Tomkos, I. (2010). Improving the efficiency of online upstream scheduling and wavelength assignment in hybrid WDM/TDMA EPON networks. IEEE Journal on Selected Areas in Communications, 28(6), 838-848. doi:10.1109/jsac.2010.100809McGarry, M. P., Reisslein, M., & Maier, M. (2006). WDM Ethernet passive optical networks. IEEE Communications Magazine, 44(2), 15-22. doi:10.1109/mcom.2006.1593545Dhaini, A. R., Assi, C. M., Maier, M., & Shami, A. (2007). Dynamic Wavelength and Bandwidth Allocation in Hybrid TDM/WDM EPON Networks. Journal of Lightwave Technology, 25(1), 277-286. doi:10.1109/jlt.2006.886683Chihchung Chen, Chengkuo Lee, & Yen-Jyh Lai. (2003). Novel voa using in-plane reflective micromirror and off-axis light attenuation. IEEE Communications Magazine, 41(8), S16-S20. doi:10.1109/mcom.2003.122271

    Energy Implications of Photonic Networks With Speculative Transmission

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    Speculative transmission has been proposed to overcome the high latency of setting up end-to-end paths through photonic networks for computer systems. However, speculative transmission has implications for the energy efficiency of the network, in particular, control circuits are more complex and power hungry and failed speculative transmissions must be repeated. Moreover, in future chip multiprocessors (CMPs) with integrated photonic network end points, a large proportion of the additional energy will be dissipated on the CMP. This paper compares the energy characteristics of scheduled and speculative chip-to-chip networks for shared memory computer systems on the scale of a rack. For this comparison, we use a novel speculative control plane which reduces energy consumption by eliminating duplicate packets from the allocation process. In addition, we consider photonic power gating to reduce processor chip energy dissipation and the energy impact of the choice between semiconductor optical amplifier and ring resonator switching technologies. We model photonic network elements using values from the published literature as well as determine the power consumption of the allocator and network adapter circuits, implemented in a commercial low leakage 45 nm CMOS process. The power dissipated on the CMP using speculative networks is shown to be roughly double that of scheduled networks at saturation load and an order of magnitude higher at low loads

    Spectrum Utilization and Congestion of IEEE 802.11 Networks in the 2.4 GHz ISM Band

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    Wi-Fi technology, plays a major role in society thanks to its widespread availability, ease of use and low cost. To assure its long term viability in terms of capacity and ability to share the spectrum efficiently, it is of paramount to study the spectrum utilization and congestion mechanisms in live environments. In this paper the service level in the 2.4 GHz ISM band is investigated with focus on todays IEEE 802.11 WLAN systems with support for the 802.11e extension. Here service level means the overall Quality of Service (QoS), i.e. can all devices fulfill their communication needs? A crosslayer approach is used, since the service level can be measured at several levels of the protocol stack. The focus is on monitoring at both the Physical (PHY) and the Medium Access Control (MAC) link layer simultaneously by performing respectively power measurements with a spectrum analyzer to assess spectrum utilization and packet sniffing to measure the congestion. Compared to traditional QoS analysis in 802.11 networks, packet sniffing allows to study the occurring congestion mechanisms more thoroughly. The monitoring is applied for the following two cases. First the influence of interference between WLAN networks sharing the same radio channel is investigated in a controlled environment. It turns out that retry rate, Clear-ToSend (CTS), Request-To-Send (RTS) and (Block) Acknowledgment (ACK) frames can be used to identify congestion, whereas the spectrum analyzer is employed to identify the source of interference. Secondly, live measurements are performed at three locations to identify this type of interference in real-live situations. Results show inefficient use of the wireless medium in certain scenarios, due to a large portion of management and control frames compared to data content frames (i.e. only 21% of the frames is identified as data frames)

    Telecommunications Networks

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    This book guides readers through the basics of rapidly emerging networks to more advanced concepts and future expectations of Telecommunications Networks. It identifies and examines the most pressing research issues in Telecommunications and it contains chapters written by leading researchers, academics and industry professionals. Telecommunications Networks - Current Status and Future Trends covers surveys of recent publications that investigate key areas of interest such as: IMS, eTOM, 3G/4G, optimization problems, modeling, simulation, quality of service, etc. This book, that is suitable for both PhD and master students, is organized into six sections: New Generation Networks, Quality of Services, Sensor Networks, Telecommunications, Traffic Engineering and Routing
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