Defragmentation with Reroutable Backup Paths in Toggled 1+1 Protection Elastic Optical Networks

Takaaki SAWA  Fujun HE  Takehiro SATO  Bijoy Chand CHATTERJEE  Eiji OKI  

IEICE TRANSACTIONS on Communications   Vol.E103-B   No.3   pp.211-223
Publication Date: 2020/03/01
Publicized: 2019/09/03
Online ISSN: 1745-1345
DOI: 10.1587/transcom.2019EBP3075
Type of Manuscript: PAPER
Category: Network Management/Operation
rerouting,  path exchanging,  1+1 path protection,  hitless defragmentation,  elastic optical networks,  

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This paper proposes a defragmentation scheme using reroutable backup paths in toggled-based quasi 1+1 path protected elastic optical networks (EONs) to improve the efficiency of defragmentation and suppress the fragmentation effect. The proposed scheme can reallocate spectrum slots of backup paths and reroute of backup paths. The path exchange function of the proposed scheme makes the primary paths become the backup state while the backup paths become the primary. This allows utilization of the advantages of defragmentation in both primary and backup paths. We formulate a static spectrum reallocation problem with rerouting (SSRR) in the toggled-based quasi 1+1 path protected EON as an integer linear programming (ILP) problem. The decision version of SSRR is proven to be an NP-complete problem. A heuristic algorithm is introduced to solve the problem for large networks networks where the ILP problem is not tractable. For a dynamic traffic scenario, an approach that suppresses the fragmentation considering rerouting and path exchanging operations is presented. We evaluate the performances of the proposed scheme by comparing it to the conventional scheme in terms of dependencies on node degree, processing time of network operations and interval time between scheduled defragmentations. The numerical results obtained from the performance evaluation indicate that the proposed scheme increases the traffic admissibility compared to the conventional scheme.