Fragmentation Metrics in Spectrally-Spatially Flexible Optical Networks

Lechowicz, Piotr; Tornatore, Massimo; Włodarczyk, Adam; Walkowiak, Krzysztof

doi:10.1007/978-3-030-38085-4_21

Cited by 10 publications

(16 citation statements)

References 19 publications

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“…To the best of our knowledge, even though several fragmentation metrics have been proposed in EON (e.g., external fragmentation, Shannon entropy or access blocking probability [5,12,22]), there is lack of investigation on the definition of network fragmentation metrics in SS-FONs, except our recent work [11]. SS-FONs introduce the additional spatial dimension, and it should be addressed in the fragmentation metrics.…”

Section: Related Workmentioning

confidence: 99%

“…The above-mentioned papers have not considered the impact of SCC on the network fragmentation and BBP. In our recent work [11], we studied various fragmentation metrics for SS-FONs with and without SCC, showing that relaxing SCC reduces blocking probability, and as a consequence, allows the allocation of more traffic in the network.…”

Section: Related Workmentioning

confidence: 99%

“…This work is an extension of [11], which was a top-scored paper at ONDM 2019. The main novelties in this work compared to [11] are the introduction of B-SChs concept, the proposal of the FA-BSC fragmentation-aware algorithm that leverages this concept, and evaluation of the algorithm's performance considering SS-FON with and without SCC. Conducted experiments show that FA-BSC minimizes the network fragmentation when compared to the reference fragmentation-aware algorithms.…”

Section: Related Workmentioning

confidence: 99%

“…In this section, we present the SS-FON model and the notation required to define fragmentation metrics. Then we introduce several fragmentation metrics (many of them are adapted from EONs) to evaluate link fragmentation in SS-FONs [11], namely, External Fragmentation (EF), Shannon Entropy (SE), access blocking probability (ABP) [5,12,22], root of sum of squares (RSS), root mean square factor (RMSF) [23].…”

Section: Fragmentation Metricsmentioning

confidence: 99%

“…These devices have lower complexity, and hence lower cost, but they are also characterized by limited or no switching flexibility in the spatial dimension [3,10]. Thus, in SS-FONs, it is important to investigate the impact of SCC on fragmentation and blocking probability when compared to the case when SCC is not enforced [11].…”

Section: Introductionmentioning

confidence: 99%

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Fragmentation metrics and fragmentation-aware algorithm for spectrally/spatially flexible optical networks

Lechowicz

Tornatore

Włodarczyk

et al. 2020

J. Opt. Commun. Netw.

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Spectrally/spatially-flexible optical networks (SS-FONs) are a promising solution to cope with future traffic requirements in optical backbone networks. SS-FONs exploit the spatial dimension to increase network capacity while preserving resource management flexibility, as they still operate within a flex-grid composed of small frequency slots (slices). Flex-grid allows realizing transmission using super-channels (SChs) that comprise a set of contiguous slots. In this paper, we focus on spectral SChs, i.e., a SCh realized only on one spatial mode on each fiber. In SS-FONs, setting up and tearing down multiple lightpath requests within flex-grid may result in spectrum fragmentation, and, in turn, blocking of requests. In this work, we investigate several fragmentation metrics in SS-FON. The problem of identifying appropriate metrics to measure fragmentation has been investigated in single-core elastic optical networks (EONs), but, to the best of our knowledge, there is lack of such investigation for SS-FONs. Therefore, we propose several fragmentation metrics for SS-FON. We introduce the concept of bordering super-channels (B-SChs), i.e., SChs whose spectrum is allocated at the "border" of already allocated spectrum slots that are promising SChs to be chosen to minimize fragmentation. The investigation of all candidate B-SCh for a request allows us to find the one which minimizes network fragmentation, and, in turn spectrum waste. Hence, we propose a fragmentation-aware algorithm with bordering super-channels (FA-BSC) that assigns optical resources to dynamic requests utilizing information from the proposed fragmentation metrics and the set of candidate B-SChs. Experiments on a representative network topology show that the investigation of multiple B-SChs in the fragmentation-aware algorithm reduces the blocking probability when compared to the reference fragmentation-aware algorithms. Finally, we analyze the impact of a spatial continuity constraint on the network fragmentation.

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