Tag: Network Monitoring

Seminar at IRISA-University Rennes1

A Survey on Fault Detection and Localization in WDM Optical Networks by Elias A. Doumith.

Abstract: Recent advances in WDM technology enable an optical fiber to carry up to 200 wavelengths operating at 40 Gbps each. In such networks, service disruptions caused by network faults (e.g., fiber cut, amplifier dysfunction) may lead to high data losses. Therefore, it is mandatory for a network operator to be able to find such faults promptly. Fault detection and localization in meshed WDM networks have been deeply investigated in the literature. Numerous schemes have been proposed to achieve fast but accurate failure localization. In this field, four main paradigms have proved their mettle, namely link-based, cycle-based, trail-based, and tree-based monitoring schemes. The aim of this seminar is to introduce the aforementioned monitoring schemes, describe the proposed approach for an optimized utilization of the network resources, and provide a comparative study of their deployment cost.


Invited paper for presentation in RELABIRA 2012

Double-link Failure Localization Based on the Monitoring Trail Concept in WDM Networks by Elias A. Doumith and Sawsan Al Zahr.

Abstract: As traffic demands are continuously increasing, core networks must be able to react almost instantaneously to any single, even multiple, failure(s) in order to prevent huge data losses. Even though the probability of simultaneous multiple failures is very small, the time needed to repair a single failure ranges from several hours (for landline fibers) to several weeks (for submarine fibers). During this period, the network is vulnerable to any new failure that may occur in the network. Therefore, designing survivable WDM networks against multiple failures requires efficient and accurate detection and localization mechanisms. In this paper, we extend the monitoring trail concept in order to detect and unambiguously localize any single- and double- link failure in the network. Compared to our previously proposed MEMOTA algorithm, the improved MEMOTA++ algorithm benefits from an improved trail reconfiguration algorithm in order to reduce its execution time. Numerical simulations have been carried out using the Deutsche Telekom and the Geant-2 European networks. We show that a monitoring solution able to localize any double-link failure in the Deutsche Telekom network is 122% more expensive than the one able to localize any single-link failure, but remains 10.9% more economical than the traditional link-based monitoring solution.


Accepted paper for presentation in ONDM 2012

A Novel Meta-Heuristic Approach for Optical Monitoring-Tree Design in WDM Networks by Elias A. Doumith, Sawsan Al Zahr, and Maurice Gagnaire.

Abstract: Thanks to recent advances in WDM technologies, an optical fiber is capable to carry up to 200 wavelengths operating at 40 Gbps each. In such high speed networks, service disruptions caused by network failures (e.g., fiber cut, amplifier dysfunction) may lead to high data losses. A network operator should be able promptly locate such failures, in order to perform fast restoration. Hence, an efficient fault detection and localization mechanism is mandatory for reliable network designing. In previous work, we have introduced the concept of monitoring trees (m-trees) to achieve fast link failure detection and localization. We have proposed an integer linear program (ILP) approach for the design of an m-tree solution that minimizes the number of required optical monitors, while achieving unambiguous failure detection and localization. In this paper, we propose a novel approach, based on the well known simulated annealing meta-heuristic, for m-tree design in WDM networks. Simulations conducted in this study show the same results as the ILP approach at much lower computation time. Our proposal can thus be applied to large-sized and very large-sized networks.


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