| 1. |
- Aparicio Pardo, Ramon, et al.
(författare)
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Balancing CapEx reduction and network stability with stable routing-virtual topology capacity adjustment (SR-VTCA)
- 2013
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Ingår i: Optical Switching and Networkning Journal. - : Elsevier. - 1573-4277 .- 1872-9770. ; 10:4, s. 343-353
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the merits of the SR–VTCA (stable routing–virtual topology capacity adjustment) approach as a mechanism to find a beneficial trade-off between network stability and reduction in capital expenditures (CapEx). These are two main objectives for the entities that own the optical infrastructure, such as network operators (NOs), and those also acting as Internet service providers (ISPs). The SR–VTCA scheme is a novel approach to adapt transparent optical networks to time-varying traffic by adjusting the number of lightpaths between node pairs, while keeping the IP routing unchanged. Lightpath bundling (LB) and anycast (AS) switching are combined in SR–VTCA operation to advertise lightpath additions/removals to the IP layer as mere adjustments (increments or decrements) in the capacity, allowing to keep the IP routing stable, and thus, simplifying control plane operations. On the contrary, a fully-reconfigurable (FR) network design, where IP routing can be also modified, would increase the burden in the control plane, but at a higher CapEx reduction, since the optical infrastructure is used more efficiently. In this work, we investigate the CapEx overprovision introduced by SR–VTCA with respect to a FR scheme. In order to do this, SR–VTCA planning problem is first modeled as a MILP formulation. A heuristic procedure based on traffic domination is then proposed to solve large instances of the problem. Exhaustive experiments are conducted comparing the SR–VTCA solutions obtained by the aforementioned MILP and heuristic proposal with solutions found by other optimization methods presented in the literature to solve the FR planning problem. Finally, the results show that SR–VTCA can achieve similar results to the FR case in terms of CapEx reduction, while a huge number of IP reroutings are saved by maintaining IP stability. Thus, SR–VTCA provides an advantageous balance between CapEx overprovisioning and the control plane overhead associated with IP rerouting.
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| 2. |
- Dzanko, Matija, et al.
(författare)
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Dedicated path protection for optical networks based on function programmable nodes
- 2018
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Ingår i: Optical Switching and Networkning Journal. - : Elsevier BV. - 1573-4277 .- 1872-9770. ; 27, s. 79-87
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Tidskriftsartikel (refereegranskat)abstract
- Due to the constantly increasing volumes and tightening reliability requirements of network traffic, survivability is one of the key concerns in optical network design. Optical "white box" nodes based on the Architecture on Demand (AoD) paradigm allow for self-healing of nodal component failures due to their architectural flexibility and the ability to employ idle components for failure recovery. By incorporating node-level survivability with network-level protection from link failures, resiliency of optical networks can be significantly improved. To this end, we propose a survivable routing algorithm for AoD-based networks called Dedicated Path Protection with Enforced Fiber Switching (DPP-EFS), which combines self-healing at the node level with dedicated path protection at the network level. The algorithm aims at improving the self-healing capabilities of the nodes by increasing the percentage of fiber switching (FS). Namely, fiber-switched lightpaths require a minimal amount of processing within the node (i.e. only signal switching), while other aspects of processing (e.g. demultiplexing, bandwidth virtualization) and the related components (i.e. demultiplexers, splitters, wavelength selective switches) remain unused and may be used as redundancy. On the other hand, lightpaths that are not eligible for FS have to be re-routed to alternative, longer paths in order to allow for FS between certain ports within the node. Therefore, the proposed algorithm pursues an advantageous trade-off between the increase of the number of idle components which can be used as redundancy at the node level and the unwanted length increase of lightpaths re-routed to render components redundant. For particular cases when DPP-EFS is not able to reduce the mean down time (MDT) in the network merely by increasing the percentage of fiber switching, we propose an algorithm for Dedicated Path Protection with Fixed Shortest Path routing and added Redundancy (DPP-FSP-RED) which adds additional spare components at strategic nodes to ensure that all connections have at least one redundant node component along their path. Simulation results show a significant reduction in MDT with minimal extra capital expenses.
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| 3. |
- Jirattigalachote, Amornrat, et al.
(författare)
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Dynamic provisioning strategies for energy efficient WDM networks with dedicated path protection
- 2011
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Ingår i: Optical Switching and Networkning Journal. - : Elsevier BV. - 1573-4277 .- 1872-9770. ; 8:3, s. 201-213
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Tidskriftsartikel (refereegranskat)abstract
- Energy consumption in optical backbone networks is increasing due to two main reasons: (i) the exponential growth of bandwidth demands, and (ii) the increase in availability requirements in order to guarantee protection of the ultra high capacity optical channels provided by wavelength division multiplexing (WDM) networks. Although state of the art reliability mechanisms are very efficient in guaranteeing high availability, they do not consider the impact of the protection resources on the network's energy consumption. Dedicated (1:1) path protection (DPP) is a well-known mechanism that provides one extra link-disjoint path for the protection of a connection request. This secondary path is reserved and maintained in an active mode even though it is not utilized most of the time. This means that in-line optical amplifiers and switching nodes/ports are always consuming power even when they are not used to reroute any primary traffic. Moreover secondary paths are on average longer than their respective primary paths. These observations motivated us to investigate the energy savings, when all unused protection resources can be switched into a low-power, stand-by state (or sleep mode) during normal network operation and can be activated upon a failure. It is shown that significant reduction of power consumption (up to 25%) can be achieved by putting protection resources into sleep mode. Moreover, in order to enhance this energy saving figure, this paper proposes and evaluates different energy-efficient algorithms, specifically tailored around the sleep mode option, to dynamically provision 1:1 dedicated path protected connection. The trade-off between energy saving and blocking probability is discussed and an efficient mechanism to overcome this drawback is devised. Our results reveal that a 34% reduction of energy consumption can be obtained with a negligible impact on the network's blocking performance.
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| 4. |
- Jirattigalachote, Amornrat, et al.
(författare)
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Sparse power equalization placement for limiting jamming attack propagation in transparent optical networks
- 2011
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Ingår i: Optical Switching and Networkning Journal. - : Elsevier BV. - 1573-4277 .- 1872-9770. ; 8:4, s. 249-258
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Tidskriftsartikel (refereegranskat)abstract
- The latest advances in Wavelength Division Multiplexing (WDM) technology are making it possible to build all-optical transparent WDM networks, which are expected to be able to satisfy the rapid growth of today's capacity demand. However, the transparency of such networks makes them highly vulnerable to deliberate attacks, specifically targeting the physical layer. Physical-layer attacks, such as high-power jamming, can cause severe service disruption or even service denial, enhanced by their capability to propagate through a transparent optical network. Several attack-aware routing and wavelength assignment algorithms have been proposed to reduce the possible disruption caused by high-power jamming attacks. However, even with network planning approaches which take network security, specifically physical-layer attacks, into account, resilience to deliberate attacks in such scenarios remains an issue. In this paper, we propose the use of wavelength-selective attenuators as power equalizers inside network nodes to limit the propagation of high-power jamming attacks. Due to the increased cost of optical switching nodes associated with the addition of power equalizers, we aim at minimizing their number through sparse power equalization placement. We developed a set of greedy algorithms to solve what we call the Power Equalization Placement (PEP) problem with the objective of minimizing the number of power equalizers needed to reduce, to a desired level, the propagation of high-power jamming attacks for a given routing scheme. We further improved upon these results by proposing a GRASP (Greedy Randomized Adaptive Search Procedure) heuristic with a somewhat longer execution time, but with significantly superior results. The performance evaluation results indicate that the proposed GRASP heuristic can achieve the same attack propagation reduction as can be obtained by equipping all nodes with power equalizers by placing them at less than 50% of the nodes on average, potentially yielding significant cost savings.
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| 5. |
- Klinkowski, Miroslaw, et al.
(författare)
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An overview of routing methods in optical burst switching networks
- 2010
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Ingår i: Optical Switching and Networking. - : Elsevier BV. - 1872-9770 .- 1573-4277. ; 7:2, s. 41-53
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Tidskriftsartikel (refereegranskat)abstract
- In this article we present a survey of routing methods in Optical Burst Switching (OBS) networks We begin with a description of routing approaches and follow the discussion with a detailed classification of routing algorithms in OBS. Afterwards, we discuss common OBS network loss models that are frequently used in routing optimization. As examples of such application, we present a linear and a non-linear formulation of a multi-path routing optimization problem with an indication on convenient resolution methods The presented algorithms are appropriate for proactive load balancing routing and aim at the improvement of network-wide burst loss performance To compare performance results, both methods are evaluated by simulation in a set of unified network scenarios (C) 2010 Elsevier B.V. All rights reserved.
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| 6. |
- Kunert, Kristina, 1976-, et al.
(författare)
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Providing Efficient Support for Real-Time Guarantees in a Fibre-Optic AWG-Based Network for Embedded Systems
- 2017
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Ingår i: Optical Switching and Networkning Journal. - Amsterdam : Elsevier. - 1573-4277 .- 1872-9770. ; 24, s. 47-56
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Tidskriftsartikel (refereegranskat)abstract
- High-performance embedded systems running real-time applications demand communication solutions providing high data rates and low error probabilities, properties inherent to optical solutions. However, providing timing guarantees for deadline bound applications in this context is far from basic due to the parallelism inherent in multiwavelength networks and often bound to include a large amount of pessimism. Assuming deterministic medium access, an admission control algorithm using a schedulability analysis can ensure deadline guarantees for real-time communication. The traffic dependency analysis presented in this paper is specifically targeting a multichannel context, taking into consideration the possibility of concurrent transmissions in these types of networks. Combining our analysis with a feasibility analysis in admission control, the amount of guaranteed hard real-time traffic could be shown to increase by a factor 7 in a network designed for a radar signal processing case. Using this combination of analysis methods will render possible an increased amount of hard real-time traffic over a given multichannel network, leading to a more efficient bandwidth utilization by deadline dependent applications without having to redesign the network or the medium access method.
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| 7. |
- Li, Shuo, et al.
(författare)
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Improving throughput and effective utilization in OBS networks
- 2015
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Ingår i: Optical Switching and Networkning Journal. - : Elsevier. - 1573-4277 .- 1872-9770. ; 18, s. 222-234
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Tidskriftsartikel (refereegranskat)abstract
- This paper considers two important performance measures that have not received much attention in performance studies of optical burst switching (OBS) networks. The first is the so-called effective utilization which is the proportion of link capacity used by bursts that eventually reach their destinations. The second considers the throughput of individual source-destination pairs that may indicate unfairness and starving connections. Using these performance measures, we evaluate a new proposed contention resolution strategy called EBSL, which is a combination of the Emulated-OBS wavelength reservation scheme, with the two contention resolution strategies - Burst Segmentation and Least Remaining Hop-count First (LRHF). The results show that EBSL can prevent congestion collapse of throughput and effective utilization, and reduce the blocking probability under heavy load conditions. We then add deflection routing to EBSL to further increase the throughput under light and medium traffic load. Finally, we replace LRHF by a fairer version of LRHF in EBSL to provide insights into fairness efficiency and tradeoffs. Overall, we demonstrate that OBS can be enhanced to overcome its known traffic congestion related weaknesses of low throughput, ineffective utilization and unfairness.
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| 8. |
- Mahloo, Mozhgan, et al.
(författare)
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PON versus AON : Which is the best solution to offload core network by peer-to-peer traffic localization
- 2015
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Ingår i: Optical Switching and Networkning Journal. - : Elsevier BV. - 1573-4277 .- 1872-9770. ; 15:0, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Video streaming and video-on-demand are gaining popularity nowadays which dictates a need of bandwidth upgrade for Internet users. Many next generation optical access network architectures have been proposed to meet high capacity requirement on a per-user basis. However, the capacity upgrade in access networks, may lead to a huge traffic growth in the aggregation/core network. One way to avoid this problem is to keep the traffic locally (i.e., inside the access network area) as much as possible. It can be obtained by using locality-aware peer-to-peer (P2P) applications for content distribution and has the potential to offload the core segment. However, various optical access network architectures accommodate the P2P traffic in different ways. Thus, it is important to study these differences in order to identify the best architecture option for capacity offloading in the core network, energy efficiency and network resource utilization. By deploying a proper architecture in the access segment along with an efficient traffic locality aware strategy, the extra investment and capacity upgrade of the expensive core network resources needed to support the future traffic expansion can be minimized. However, to the best of our knowledge this kind of assessment is so far not available. Therefore, in this paper, we analyze the efficiency of supporting locality-aware P2P video distribution algorithm in three main types of optical access network architectures, i.e., active optical network (AON), wavelength division multiplexing passive optical network (WDM PON) and time/wavelength division multiplexing PON (TWDM PON). Our goal is to provide important design guidelines for the next generation broadband access architectures, while minimizing the need for the core network upgrade. We obtain this objective by utilizing the unique characteristics of each access network architecture in accommodating P2P video delivery applications. We have done an extensive literature study and for the first time we have compared performance of these architectures with respect to the amount of the traffic on the links in different aggregation levels, power consumption taking into account sleep mode functionality at the user premises, and required switching capacity in the nodes. Our results reveal that both active and passive architectures have good ability to localize P2P traffic, whereas they show distinct performance with respect to the other aforementioned aspects. This is caused by the different number of aggregation levels, link capacity, and resource allocation protocols. Considering the overall performance evaluation, it is shown that TWDM PON is the most promising option for the future broadband access, where locality-aware P2P video distribution is applied, thanks to its low energy consumption and required switching capacity of the network equipment needed to deliver this service. This conclusion is against the general intuition because of the PON׳s centralized control plane and passive infrastructure without switching capability in the field. Our unexpected conclusion can be of particular interest to operators as it is perfectly aligned with next generation optical access architecture identified by Full Service Access Networks (FSAN).
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| 9. |
- Mahloo, Mozhgan, et al.
(författare)
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Protection cost evaluation of WDM-based next generation optical access networks
- 2013
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Ingår i: Optical Switching and Networkning Journal. - : Elsevier BV. - 1573-4277 .- 1872-9770. ; 10:1, s. 89-99
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Tidskriftsartikel (refereegranskat)abstract
- New technologies and advanced network devices make it possible to move towards high capacity access networks able to satisfy the growing traffic demand. Wavelength division multiplexing (WDM) is considered as one of the promising technologies for the next generation access networks since it offers higher bandwidth and longer reach compared to the current technologies (such as time division multiplexing (TDM) based networks). However, the migration to a new technology is typically based on an overall techno-economic study which should assure the network operator that the new implementation is cost effective and profitable while able to provide the required services to the users. Another important aspect in the access network design is the network reliability performance, which can be improved by providing a certain level of protection for equipment and/or infrastructure with high failure impact ratio in order to prevent a big number of the users being affected by a single failure. The cost of protection should be carefully evaluated since providing the backup resources may be too expensive for a network operator. In this paper, we investigate the capital and operational expenditures for two next generation optical access (NGOA) networks based on the WDM technology in dense urban areas. Three scenarios with different splitting ratios are studied for each technology, with and without protection. The aim of this work is to investigate the impact of providing protection on the total cost of NGOA networks. The results show that in the dense urban areas the fibers and digging costs are highly shared among the end users but still vary according to the splitting ratios for different scenarios and the fiber layout. It also can be seen that with a proper fiber layout design, minor extra investment for protection of NGOA networks can make a significant saving on failure related operational cost and that operational expenditures depend significantly on the fiber layout.
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| 10. |
- Natalino, Carlos, Dr. 1987-, et al.
(författare)
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Energy- and fatigue-aware RWA in optical backbone networks
- 2019
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Ingår i: Optical Switching and Networkning Journal. - : ELSEVIER SCIENCE BV. - 1573-4277 .- 1872-9770. ; 31, s. 193-201
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Tidskriftsartikel (refereegranskat)abstract
- Connection provisioning in Wavelength Division Multiplexing (WDM) networks needs to account for a number of crucial parameters. On the one hand, operators need to ensure the connection availability requirements defined in Service Level Agreements (SLAs). This is addressed by selecting an appropriate amount of backup resources and recovery strategies for the connections over which services are provisioned. Services requiring less strict availability requirements can be routed over unprotected lightpaths. Services with more strict availability requirements are provisioned over protected lightpaths in order to cope with possible failures in the network. Another important aspect to consider during the provisioning process is energy efficiency. Green strategies leverage on setting network devices in Sleep Mode (SM) or Active Mode (AM) depending on whether or not they are needed to accommodate traffic. However, frequent power state changes introduce thermal fatigue which in turn has a negative effect on the device lifetime. Finally, in multi-period traffic scenarios, it is also important to minimize the number of reconfigurations of lightpaths already established in the network in order to avoid possible traffic disruptions at higher layers. The work presented in this paper tackles the connection provisioning paradigm in an optical backbone network with a multi-period traffic scenario. More specifically the paper looks into the interplay among (i) energy efficiency, (ii) thermal fatigue, and (iii) lightpath reconfiguration aspects. To this end, the Energy and Fatigue Aware Heuristic with Unnecessary Reconfiguration Avoidance (EFAH-URA) is introduced, showing that it is possible to balance the three aspects mentioned above in an efficient way. When compared to the pure energy-aware strategies, EFAH-URA significantly improves the average connection availability for both unprotected and protected connections. On the other hand, it is done at the expense of reduced energy saving.
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