scholarly journals Preface to the December 2015 issue

2015 ◽  
Author(s):  
Héctor Cancela
Keyword(s):  
Distributed Computing ◽  
Computer Science ◽  
Optical Networks ◽  
Mobile Devices ◽  
Wdm Networks ◽  
Domain Name ◽  
Historical Climate ◽  
Quality Of Protection ◽  
Security Models

We are glad to present the last issue of 2015, completing Volume 18 of the CLEI Electronic Journal. This issue is comprised by the following regular papers.The first paper, “Quality of Protection on WDM networks: A Recovery Probability based approach”, by M. D. Rodas-Brítez and D. P. Pinto-Roa, features a proposal of a new quality of protection (QoP) paradigm for Wavelength Division Multiplexing optical networks. The new approach is flexible, allowing the network administrator to define and select a set of protection levels, based on recovery probabilities which measure the degree of conflict among primary lightpaths sharing backup lightpaths. To show the interest of the approach, a Genetic Algorithm is used to design a routing strategy by multi-objectiveoptimization, minimizing the number of blocked requests, the number of services without protection, the total differences between the requested QoP and the assigned QoP, and the network cost.The second paper, “Towards Scalability for Federated Identity Systems for Cloud-Based Environments”, by A.A. Pereira, J. B. M. Sobral and C. M. Westphall, addresses scalability issues in identity management for cloud computing environments. The authors propose an adapted sticky-session mechanism, as an alternative approach to the more common distributed memory approach, and discuss the implications in therms of computational resources, throughput and overall efficiency. The following work, “Formal Analysis of Security Models for Mobile Devices, Virtualization Platforms, and Domain Name Systems”, by G. Betarte and C. Luna,tackles security models for security-critical applications in three areas: mobile devices, virtualization platforms, and domain name systems. The authors develop formalizations using the Calculus of Inductive Constructions, to study different usual variants of security models in these platforms and their properties.The last paper of this issue is “Digi-Clima Grid: image processing and distributed computing for recovering historical climate data”, by authors S. Nesmachnow, G. Usera and F. Brasileiro. This paper reports an experience of implementing semi-automatic techniques for digitalizing and recovering historical climate records applying parallel computing techniques over distributed computing infrastructures, which was applied to Uruguayan historical climate data.As we complete now the eighteenth year of continued existence of CLEIej, we thank the regional community for its continued support, and we encourage researchers working in computer science and its applications to consider submitting their work to CLEIej, as the the leading electronic, open access journal in Computer Science in Latin America.

scholarly journals Differentiated quality-of-protection provisioning with probabilistic-shared risk link group in survivable flexi-grid optical networks

2014 ◽  
Vol 53 (6) ◽  
pp. 066111
Author(s):  
Yongli Zhao ◽  
Jinyan Liu ◽  
Jie Zhang ◽  
Bowen Chen ◽  
Chen Ma ◽  
...  
Keyword(s):  
Optical Networks ◽  
Link Group ◽  
Quality Of Protection ◽  
Shared Risk

Role of Self Phase Modulation and Cross Phase Modulation on Quality of Signal in Optical Links

2019 ◽  
Vol 13 ◽  
Author(s):  
Karamjit Kaur ◽  
Anil Kumar
Keyword(s):  
Optical Networks ◽  
Phase Modulation ◽  
Input Power ◽  
Wdm Networks ◽  
Signal Power ◽  
Optical Links ◽  
System Parameters ◽  
Quality Of Transmission ◽  
The Impact

Background: In WDM networks, there is a crucial need to monitor signal degradation factors in order to maintain the quality of transmission. This is more critical in dynamic optical networks as non-linear impairments are network state dependent. Moreover, PLIs are accumulative in nature, so the overall impact is increased tremendously as the length of signal path is increased. The interactions between different impairments along the path also influence their overall impact. Objective: Among the different impairments, the present work focus on phase modulations owing to intensities of signals themselves as well as the neighboring signals. It includes the influence of SPM, SPM and XPM, system parameters like signal power, wavelength and fiber parameters like attenuation coefficient, dispersion coefficient and their influence on Q-value and BER. Method: The analysis is done through a single and two-channel transmitter system with varied power, wavelengths and system parameters. The corresponding optical spectrums are analysed. Result & Conclusion: It has been found that SPM and XPM pose broadening effect on spectrum without any effect on temporal distributions. The magnitude of signal power is among the parameters significantly influencing the broadening of spectrum. Higher is the power, more is the magnitude of broadening. It has been found that in order to neglect the impact of input power; its magnitude must be kept below 20 mW. Also, the dispersion and attenuation value need to be carefully as they pose counteracting effect to SPM and XPM for certain values and hence can be used as compensation measure without any additional cost.

scholarly journals Quality of Protection on WDM networks: A Recovery Probability based approach

2015 ◽  
Author(s):  
Marcelo Rodas-Brítez ◽  
Diego Pinto-Roa
Keyword(s):  
Genetic Algorithm ◽  
Optical Fibers ◽  
Wdm Networks ◽  
New Paradigm ◽  
Generic Level ◽  
Network Cost ◽  
Quality Of Protection ◽  
Resource Distributions ◽  
Probability Concept

WDM networks survivability needs a flexible quality of protection (QoP) due to the variety of existing connection demands, lack of fair resource distributions under traditional QoP and optimal resources assignment. Thus, this paper proposes a new paradigm of QoP based on generic levels of protection where the set of protection levels can be defined as the network administrator needs, i.e., a flexible QoP approach whose particular case is the traditional or non-flexible QoP approach. Essentially, the proposed generic level is based on the recovery probability concept which measures the grade of conflict among primary lightpaths that share backup lighpaths for link failure recovery. In order to study how this strategy impacts on the network cost, a Genetic Algorithm is proposed. It calculates the primary and backup lightpaths, considering a multi-objective optimization on the basis of lexicographical sorting approach. The Genetic Algorithm minimizes the number of blocked requests, the number of services without protection, the total differences between the requested QoP and the assigned QoP, and the network cost; all of which by considering the optical fibers used and subject to the wavelength usage as constraint. The experimental results indicate that the proposed approach –flexible QoP– is a promising strategy where the network cost, the number of requests and QoP levels are contradictory objective functions in environments with homogeneous and heterogeneous QoP requirements.

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