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Eiji Oki - One of the best experts on this subject based on the ideXlab platform.
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Defragmentation based on route partitioning in 1 1 protected elastic optical networks
Computer Networks, 2020Co-Authors: Bijoy Chand Chatterjee, Eiji OkiAbstract:Abstract In survivable elastic optical networks (EONs), spectrum fragmentation is one of the major obstacles to efficiently use spectrum resources. Efficient Defragmentation approaches are indispensable to reduce spectrum fragmentation in survivable EONs, where both full 1 + 1 protected and quasi 1 + 1 protected services exist. The full 1 + 1 protected service offers full reliability without causing any traffic disturbance, where the backup path is not allowed to be reallocated, i.e., 1 + 1 path protection is always maintained. Whereas, the quasi 1 + 1 protected service compromises the reliability if any failure occurs on a primary path while its corresponding backup path is being reallocated. When full 1 + 1 protected and quasi 1 + 1 lightpaths are mixed in EONs, the network operators need to consider them to achieve thorough Defragmentation carefully. This paper presents and investigates Defragmentation based on route partitioning intending to reduce the spectrum fragmentation and blocking probability in 1 + 1 protected EONs, where both full 1 + 1 protected and quasi 1 + 1 protected services exist. A Defragmentation scheme that focuses on minimizing the retuning interference on the full 1 + 1 protected lightpaths is introduced; the retuning interference occurs when a full 1 + 1 protected lightpath cannot be retuned to fill in a gap left by an expired lightpath due to the interference of another lightpath that prevents it from being moved further. We define a route partitioning optimization problem to minimize the interference on full 1 + 1 lightpaths in 1 + 1 protected EONs considering both full 1 + 1 protected and quasi 1 + 1 protected lightpaths. We formulate the problem as an integer linear programming (ILP) problem. The decision version of route partitioning problem in 1 + 1 protected EONs is proved as an NP-complete problem. We develop a heuristic algorithm for the case where the ILP is not tractable. We provide an online Defragmentation algorithm for dynamic traffic. The effectiveness of the introduced Defragmentation scheme with route partitioning is demonstrated through a simulation study.
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Defragmentation using reroutable backup paths in toggled 1 1 path protected elastic optical networks
Asia-Pacific Conference on Communications, 2018Co-Authors: Takaaki Sawa, Bijoy Chand Chatterjee, Takehiro Sato, Eiji OkiAbstract:This work proposes a Defragmentation scheme using reroutable backup paths in toggled-based quasi 1+1 path protected elastic optical networks to enhance the efficiency of Defragmentation and suppress the fragmentation effect. The proposed scheme allows both reallocation of spectrum slots of backup paths and rerouting of backup paths. By using the path exchanging approach in the proposed scheme, the primary paths become the backup path while the backup path becomes the primary path. This allows to utilize the advantages of Defragmentation in both primary and backup paths. Considering rerouting and path exchanging, we present to the key idea to formulate the proposed scheme as an integer linear programming (ILP) problem. A heuristic algorithm is introduced to solve the problem for large networks, when ILP is not tractable. For a dynamic traffic scenario, an approach that suppresses the fragmentation considering rerouting and path exchanging operations is presented. The numerical results indicate that the blocking probability using the proposed scheme is suppressed compared to the conventional scheme.
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Defragmentation Scheme Based on Exchanging Primary and Backup Paths in 1+1 Path Protected Elastic Optical Networks
IEEE ACM Transactions on Networking, 2017Co-Authors: Seydou Ba, Bijoy Chand Chatterjee, Eiji OkiAbstract:In elastic optical networks (EONs), a major obstacle to using the spectrum resources efficiently is the spectrum fragmentation. In the literature, several Defragmentation approaches have been presented. For 1+1 path protection, conventional Defragmentation approaches consider designated primary and backup paths. This exposes the spectrum to fragmentations induced by the primary lightpaths, which are not to be disturbed in order to achieve hitless Defragmentation. This paper proposes a Defragmentation scheme using path exchanging in 1+1 path protected EONs. We exchange the path function of the 1+1 protection with the primary toggling to the backup state, while the backup becomes the primary. This allows both lightpaths to be reallocated during the Defragmentation process, while they work as backup, offering hitless Defragmentation. Considering path exchanging, we define a static spectrum reallocation optimization problem that minimizes the spectrum fragmentation while limiting the number of path exchanging and reallocation operations. We then formulate the problem as an integer linear programming (ILP) problem. We prove that a decision version of the defined static reallocation problem is NP-complete. We present a spectrum Defragmentation process for dynamic traffic, and introduce a heuristic algorithm for the case that the ILP problem is not tractable. The simulation results show that the proposed scheme outperforms the conventional one and improves the total admissible traffic up to 10%.
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route partitioning scheme for elastic optical networks with hitless Defragmentation
IEEE\ OSA Journal of Optical Communications and Networking, 2016Co-Authors: Bijoy Chand Chatterjee, Satoru Okamoto, Naoaki Yamanaka, Andrea Fumagalli, Eiji OkiAbstract:Hitless Defragmentation has been introduced as an approach to limit the spectrum fragmentation in elastic optical networks without traffic disruption. It facilitates the accommodation of new requests by creating large spectrum blocks as it moves active lightpaths (retuning) to fill in gaps left in the spectrum by expired ones. Nevertheless, hitless Defragmentation witnesses limitations for gradual retuning with the conventionally used first-fit allocation. The first-fit allocation stacks all lightpaths to the lower end of the spectrum. This leads to a large number of lightpaths that need to be retuned and are subject to interfering with each other's retuning. This paper proposes a route partitioning scheme for hitless Defragmentation in order to increase the admissible traffic in elastic optical networks. The proposed scheme uses route partitioning with the first-last fit allocation to increase the possibilities of lightpath retuning by avoiding the retuning interference among lightpaths. The first-last fit allocation is used to set a bipartition with one partition allocated with the first fit and the second with the last fit. Lightpaths that are allocated on different partitions cannot interfere with each other. Thus, the route partitioning avoids interference among lightpaths when retuning. We define the route partitioning problem as an optimization problem to minimize the total interference. We then introduce an integer linear programming problem (ILP) that yields an optimal routing and partitioning. We prove that the route partitioning problem is non-deterministic polynomial-time hard (NP-hard). We present a heuristic algorithm for large networks, where the ILP used to represent the route partitioning is not tractable. The simulation results show that the proposed route partitioning scheme using the first-last fit outperforms the conventional first-fit allocation for hitless Defragmentation in term of allowable traffic.
S J B Yoo - One of the best experts on this subject based on the ideXlab platform.
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demonstration of online spectrum Defragmentation enabled by openflow in software defined elastic optical networks
Optical Fiber Communication Conference, 2014Co-Authors: Cen Chen, Zuqing Zhu, Mingyang Zhang, Yan Shao, Lei Liu, S J B YooAbstract:We propose and experimentally demonstrate a control-plane framework to realize online spectrum Defragmentation (DF) in software-defined elastic optical networks. Experimental results show that the spectrum DF enabled by OpenFlow reduces the blocking probability effectively.
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spectrum Defragmentation algorithms for elastic optical networks using hitless spectrum retuning techniques
Optical Fiber Communication Conference, 2013Co-Authors: Mingyang Zhang, Yawei Yin, Zuqing Zhu, Roberto Proietti, S J B YooAbstract:We propose several algorithms to achieve hitless bandwidth Defragmentation using spectrum retuning in elastic optical networks. Two retuning techniques, spectrum sweeping and hop tuning, are studied. Simulation results show that the hop tuning technique achieves better Defragmentation performance.
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quasi hitless Defragmentation technique in elastic optical networks by a coherent rx lo with fast tx wavelength tracking
International Conference on Photonics in Switching, 2012Co-Authors: Roberto Proietti, Ke Wen, Yawei Yin, S J B YooAbstract:This paper proposes a technique to realize quasi-hitless Defragmentation in elastic optical networks. The technique exploits fast tunable lasers in the transponders and a rapid TX wavelength tracking scheme at the RX based on an athermal AWG and a PD-array. The propose scheme can potentially achieve Defragmentation operation with a service disruption time below 400ns.
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dynamic on demand Defragmentation in flexible bandwidth elastic optical networks
Optics Express, 2012Co-Authors: Yawei Yin, Ke Wen, David J Geisler, Ruiting Liu, S J B YooAbstract:While flexible bandwidth elastic optical networking is a promising direction for future networks, the spectral fragmentation problem in such a network inevitably raises the blocking probability and significantly degrades network performance. This paper addresses the spectral Defragmentation problem using an auxiliary graph based approach, which transforms the problem into a matter of finding the maximum independent set (MIS) in the constructed auxiliary graph. The enabling technologies and Defragmentation-capable node architectures, together with heuristic Defragmentation algorithms are proposed and evaluated. Simulation results show that the proposed min-cost Defragmentation algorithms can significantly reduce the blocking probability of incoming requests in a spectrally fragmented flexible bandwidth optical network, while substantially minimizing the number of disrupted connections.
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demonstration of spectral Defragmentation in flexible bandwidth optical networking by fwm
IEEE Photonics Technology Letters, 2011Co-Authors: David J Geisler, Ke Wen, Yawei Yin, Ryan P. Scott, Nicolas K Fontaine, Shuo Chang, S J B YooAbstract:Flexible bandwidth elastic optical networking is an attractive solution for efficiently matching allocated bandwidth with link demand, but suffers from inevitable spectral fragmentation. In this letter, we discuss spectral Defragmentation in flexible bandwidth networks using four-wave mixing (FWM) and wavelength selective switch (WSS)-based wavelength conversion blocks. Simulations show a Defragmentation degree of one (i.e., the number of Defragmentation blocks equals one) results in 71% and 47% reductions in blocking probability under high offered load (680 Erlangs) and low offered load (220 Erlangs), respectively. Further reductions in blocking probability result from an increased Defragmentation degree. Experimental results show spectral Defragmentation over 500 GHz of bandwidth for a Defragmentation degree of one, validating FWM- and WSS-based spectral Defragmentation in flexible bandwidth networks.
Limei Peng - One of the best experts on this subject based on the ideXlab platform.
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protection lightpath based hitless spectrum Defragmentation for distance adaptive elastic optical networks
Optics Express, 2016Co-Authors: Chao Wang, Gangxiang Shen, Limei PengAbstract:Spectrum Defragmentation can improve spectrum utilization for an elastic optical network (EON). However, most of the existing studies have focused on Defragmentation for working lightpaths, which may affect upper-layer network services. This paper considers protection lightpath-based hitless spectrum Defragmentation for distance adaptive elastic optical networks. Without affecting working lightpaths, but defragmenting spectra for protection lightpaths, we expect to achieve truly hitless spectrum Defragmentation for an EON. Shared backup path protection (SBPP) technique is employed as a representative network protection technique to evaluate the benefit of the proposed Defragmentation scheme. To smooth the network spectra for future arriving lightpath requests so as to reduce bandwidth blocking probability (BBP), we propose two Defragmentation triggering mechanisms, namely, Defragmentation upon blocking (BTD) and batch Defragmentation (BD). For each of them, we also propose two spectrum Defragmentation algorithms, namely, Defragmentation with sequentially releasing and re-establishing protection lightpaths (SR-D) and Defragmentation with jointly releasing and re-establishing protection lightpaths (JR-D). The performances of these proposed algorithms are evaluated from perspectives of BBP and average number of reconfigurations per successfully established lightpath service (ANR). Simulation results show that compared to the case without Defragmentation, the proposed scheme is effective to reduce BBP, which trades off with ANR.
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protection path based hitless spectrum Defragmentation in elastic optical networks shared backup path protection
Optical Fiber Communication Conference, 2015Co-Authors: Chao Wang, Gangxiang Shen, Bowen Chen, Limei PengAbstract:We propose two protection path-based spectrum Defragmentation algorithms to improve the spectrum utilization for an elastic optical network with shared backup path protection (SBPP). Results show that the proposed algorithms can significantly improve spectrum efficiency compared to the case without Defragmentation.
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protection path based hitless spectrum Defragmentation for elastic optical networks 1 1 path protection
2014 Asia Communications and Photonics Conference (ACP), 2014Co-Authors: Chao Wang, Gangxiang Shen, Limei PengAbstract:We propose a protection path-based spectrum Defragmentation approach to improve the spectrum utilization of an elastic optical network under the 1+1 path protection technique. Results show that the proposed approach can significantly improve spectral efficiency compared to the case without Defragmentation.
Bijoy Chand Chatterjee - One of the best experts on this subject based on the ideXlab platform.
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Defragmentation based on route partitioning in 1 1 protected elastic optical networks
Computer Networks, 2020Co-Authors: Bijoy Chand Chatterjee, Eiji OkiAbstract:Abstract In survivable elastic optical networks (EONs), spectrum fragmentation is one of the major obstacles to efficiently use spectrum resources. Efficient Defragmentation approaches are indispensable to reduce spectrum fragmentation in survivable EONs, where both full 1 + 1 protected and quasi 1 + 1 protected services exist. The full 1 + 1 protected service offers full reliability without causing any traffic disturbance, where the backup path is not allowed to be reallocated, i.e., 1 + 1 path protection is always maintained. Whereas, the quasi 1 + 1 protected service compromises the reliability if any failure occurs on a primary path while its corresponding backup path is being reallocated. When full 1 + 1 protected and quasi 1 + 1 lightpaths are mixed in EONs, the network operators need to consider them to achieve thorough Defragmentation carefully. This paper presents and investigates Defragmentation based on route partitioning intending to reduce the spectrum fragmentation and blocking probability in 1 + 1 protected EONs, where both full 1 + 1 protected and quasi 1 + 1 protected services exist. A Defragmentation scheme that focuses on minimizing the retuning interference on the full 1 + 1 protected lightpaths is introduced; the retuning interference occurs when a full 1 + 1 protected lightpath cannot be retuned to fill in a gap left by an expired lightpath due to the interference of another lightpath that prevents it from being moved further. We define a route partitioning optimization problem to minimize the interference on full 1 + 1 lightpaths in 1 + 1 protected EONs considering both full 1 + 1 protected and quasi 1 + 1 protected lightpaths. We formulate the problem as an integer linear programming (ILP) problem. The decision version of route partitioning problem in 1 + 1 protected EONs is proved as an NP-complete problem. We develop a heuristic algorithm for the case where the ILP is not tractable. We provide an online Defragmentation algorithm for dynamic traffic. The effectiveness of the introduced Defragmentation scheme with route partitioning is demonstrated through a simulation study.
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Defragmentation using reroutable backup paths in toggled 1 1 path protected elastic optical networks
Asia-Pacific Conference on Communications, 2018Co-Authors: Takaaki Sawa, Bijoy Chand Chatterjee, Takehiro Sato, Eiji OkiAbstract:This work proposes a Defragmentation scheme using reroutable backup paths in toggled-based quasi 1+1 path protected elastic optical networks to enhance the efficiency of Defragmentation and suppress the fragmentation effect. The proposed scheme allows both reallocation of spectrum slots of backup paths and rerouting of backup paths. By using the path exchanging approach in the proposed scheme, the primary paths become the backup path while the backup path becomes the primary path. This allows to utilize the advantages of Defragmentation in both primary and backup paths. Considering rerouting and path exchanging, we present to the key idea to formulate the proposed scheme as an integer linear programming (ILP) problem. A heuristic algorithm is introduced to solve the problem for large networks, when ILP is not tractable. For a dynamic traffic scenario, an approach that suppresses the fragmentation considering rerouting and path exchanging operations is presented. The numerical results indicate that the blocking probability using the proposed scheme is suppressed compared to the conventional scheme.
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Defragmentation Scheme Based on Exchanging Primary and Backup Paths in 1+1 Path Protected Elastic Optical Networks
IEEE ACM Transactions on Networking, 2017Co-Authors: Seydou Ba, Bijoy Chand Chatterjee, Eiji OkiAbstract:In elastic optical networks (EONs), a major obstacle to using the spectrum resources efficiently is the spectrum fragmentation. In the literature, several Defragmentation approaches have been presented. For 1+1 path protection, conventional Defragmentation approaches consider designated primary and backup paths. This exposes the spectrum to fragmentations induced by the primary lightpaths, which are not to be disturbed in order to achieve hitless Defragmentation. This paper proposes a Defragmentation scheme using path exchanging in 1+1 path protected EONs. We exchange the path function of the 1+1 protection with the primary toggling to the backup state, while the backup becomes the primary. This allows both lightpaths to be reallocated during the Defragmentation process, while they work as backup, offering hitless Defragmentation. Considering path exchanging, we define a static spectrum reallocation optimization problem that minimizes the spectrum fragmentation while limiting the number of path exchanging and reallocation operations. We then formulate the problem as an integer linear programming (ILP) problem. We prove that a decision version of the defined static reallocation problem is NP-complete. We present a spectrum Defragmentation process for dynamic traffic, and introduce a heuristic algorithm for the case that the ILP problem is not tractable. The simulation results show that the proposed scheme outperforms the conventional one and improves the total admissible traffic up to 10%.
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route partitioning scheme for elastic optical networks with hitless Defragmentation
IEEE\ OSA Journal of Optical Communications and Networking, 2016Co-Authors: Bijoy Chand Chatterjee, Satoru Okamoto, Naoaki Yamanaka, Andrea Fumagalli, Eiji OkiAbstract:Hitless Defragmentation has been introduced as an approach to limit the spectrum fragmentation in elastic optical networks without traffic disruption. It facilitates the accommodation of new requests by creating large spectrum blocks as it moves active lightpaths (retuning) to fill in gaps left in the spectrum by expired ones. Nevertheless, hitless Defragmentation witnesses limitations for gradual retuning with the conventionally used first-fit allocation. The first-fit allocation stacks all lightpaths to the lower end of the spectrum. This leads to a large number of lightpaths that need to be retuned and are subject to interfering with each other's retuning. This paper proposes a route partitioning scheme for hitless Defragmentation in order to increase the admissible traffic in elastic optical networks. The proposed scheme uses route partitioning with the first-last fit allocation to increase the possibilities of lightpath retuning by avoiding the retuning interference among lightpaths. The first-last fit allocation is used to set a bipartition with one partition allocated with the first fit and the second with the last fit. Lightpaths that are allocated on different partitions cannot interfere with each other. Thus, the route partitioning avoids interference among lightpaths when retuning. We define the route partitioning problem as an optimization problem to minimize the total interference. We then introduce an integer linear programming problem (ILP) that yields an optimal routing and partitioning. We prove that the route partitioning problem is non-deterministic polynomial-time hard (NP-hard). We present a heuristic algorithm for large networks, where the ILP used to represent the route partitioning is not tractable. The simulation results show that the proposed route partitioning scheme using the first-last fit outperforms the conventional first-fit allocation for hitless Defragmentation in term of allowable traffic.
Chao Wang - One of the best experts on this subject based on the ideXlab platform.
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protection lightpath based hitless spectrum Defragmentation for distance adaptive elastic optical networks
Optics Express, 2016Co-Authors: Chao Wang, Gangxiang Shen, Limei PengAbstract:Spectrum Defragmentation can improve spectrum utilization for an elastic optical network (EON). However, most of the existing studies have focused on Defragmentation for working lightpaths, which may affect upper-layer network services. This paper considers protection lightpath-based hitless spectrum Defragmentation for distance adaptive elastic optical networks. Without affecting working lightpaths, but defragmenting spectra for protection lightpaths, we expect to achieve truly hitless spectrum Defragmentation for an EON. Shared backup path protection (SBPP) technique is employed as a representative network protection technique to evaluate the benefit of the proposed Defragmentation scheme. To smooth the network spectra for future arriving lightpath requests so as to reduce bandwidth blocking probability (BBP), we propose two Defragmentation triggering mechanisms, namely, Defragmentation upon blocking (BTD) and batch Defragmentation (BD). For each of them, we also propose two spectrum Defragmentation algorithms, namely, Defragmentation with sequentially releasing and re-establishing protection lightpaths (SR-D) and Defragmentation with jointly releasing and re-establishing protection lightpaths (JR-D). The performances of these proposed algorithms are evaluated from perspectives of BBP and average number of reconfigurations per successfully established lightpath service (ANR). Simulation results show that compared to the case without Defragmentation, the proposed scheme is effective to reduce BBP, which trades off with ANR.
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protection path based hitless spectrum Defragmentation in elastic optical networks shared backup path protection
Optical Fiber Communication Conference, 2015Co-Authors: Chao Wang, Gangxiang Shen, Bowen Chen, Limei PengAbstract:We propose two protection path-based spectrum Defragmentation algorithms to improve the spectrum utilization for an elastic optical network with shared backup path protection (SBPP). Results show that the proposed algorithms can significantly improve spectrum efficiency compared to the case without Defragmentation.
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protection path based hitless spectrum Defragmentation for elastic optical networks 1 1 path protection
2014 Asia Communications and Photonics Conference (ACP), 2014Co-Authors: Chao Wang, Gangxiang Shen, Limei PengAbstract:We propose a protection path-based spectrum Defragmentation approach to improve the spectrum utilization of an elastic optical network under the 1+1 path protection technique. Results show that the proposed approach can significantly improve spectral efficiency compared to the case without Defragmentation.