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1

Whose fault is it? Correctly attributing outages in cloud services

Adriani Matteo, Naldi Maurizio

Annals of Computer Science and Information Systems

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2019

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Vol. 18

433--440

EN

Cloud availability is a major performance parameter in cloud Service Level Agreements (SLA). Its correct evaluation is essential to SLA enforcement and possible litigation issues. Current methods fail to correctly identify the fault location, since they include the network contribution. We propose a procedure to identify the failures actually due to the cloud itself and provide a correct cloud availability measure. The procedure employs tools that are freely available, i.e. traceroute and whois, and arrives at the availability measure by first identifying the boundaries of the cloud. We evaluate our procedure by testing it on three major cloud providers: Google Cloud, Amazon AWS, and Rackspace. The results show that the procedure arrives at a correct identification in 95% of cases. The cloud availability obtained in the test after correct identification lies between 3 and 4 nines for the three platforms under test.

2

Wybrane aspekty badań symulacyjnych strat w rzeczywistych łączach satelitarnych

Wilk-Jakubowski J. Ł.

Prace Naukowe Akademii im. Jana Długosza w Częstochowie. Technika, Informatyka, Inżynieria Bezpieczeństwa

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2018

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T. 6

135--151

PL

Na konkurencyjność oraz innowacyjność gospodarki światowej wpływa stan zaawansowania technologii TIK. Jednym z rozwiązań podnoszenia jakości świadczonych usług jest dążenie do optymalizacji współczesnych systemów łączności satelitarnej. Z punktu widzenia ich pracy, w celu zapewnienia zadowalającej pracy łącza satelitarnego konieczna jest odpowiednia moc nadajnika. W praktyce moc ta uzależniona jest od wielu czynników, jak chociażby: współrzędne geograficzne miejsca odbioru, ukształtowanie terenu, częstotliwość, lokalizacja anteny (ustawienie anteny), tłumienie sygnału w wolnej przestrzeni, wymagany poziom dostępności łącza. Czynniki te przekładają się na bilans energetyczny łącza satelitarnego, który uzależniony jest ponadto od parametrów technicznych systemu (zwłaszcza: apertury anteny, sprawności anteny oraz całkowitych strat w łączu). W artykule przeanalizowano wpływ całkowitych strat w łączu w zakresie 0,1-0,7 dB na jakość odbioru mikrofalowego sygnału satelitarnego w obszarze Kielc (z uwzględnieniem szumów interferencyjnych), co pozwala przedstawić wpływ tych strat na odbiór sygnału w skrajnie niekorzystnych warunkach.

EN

To ensure satisfactory operation of satellite links in the direction of the satellite-to-earth is essential to get an adequate power of the transmitter. In practice, this power depends on many factors such as: geographical coordinates, terrain, frequency, antenna aperture, antenna efficiency, coupling loss, the signal attenuation in space – in the atmosphere, the required level of availability of bandwidth, etc. Moreover in order to ensure a correct balance, properly conducted link budget requires consideration of extreme weather conditions (precipitation etc.). It is necessary to determine the required transmitter power (or antenna performance) as a function of many factors. The article analyzes the impact of the coupling loss on the receiving satellite signal and presents the results of modeling of these losses in the actual satellite links.

3

An Optimized Propagation Model based on Measurement Data for Indoor Environments

Morocho-Yaguana M., Ludeňa-González P., Sandoval F., Poma-Vélez B., Erreyes-Dota A.

Journal of Telecommunications and Information Technology

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2018

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nr 2

69--75

EN

Propagation is an essential factor ensuring good coverage of wireless communications systems. Propagation models are used to predict losses in the path between transmitter and receiver nodes. They are usually deﬁned for general conditions. Therefore, their results are not always adapted to the behavior of real signals in a speciﬁc environment. The main goal of this work is to propose a new model adjusting the loss coeﬃcients based on empirical data, which can be applied in an indoor university campus environment. The Oneslope, Log-distance and ITU models are described to provide a mathematical base. An extensive measurement campaign is performed based on a strict methodology considering different cases in typical indoor scenarios. New loss parameter values are deﬁned to adjust the mathematical model to the behavior of real signals in the campus environment. The experimental results show that the model proposed oﬀers an attenuation average error of 2.5% with respect to the losses measured. In addition, comparison of the proposed model with existing solutions shows that it decreases the average error signiﬁcantly for all scenarios under evaluation.

4

The study of thermal connecting of telecommunication optical fibers (SiO2: GeO2) and EDF (SiO2: Al2O3, Er) fibers

Ratuszek M., Ratuszek M. J., Hejna J.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2013

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Vol. 61, nr 1

279-286

EN

This paper presents the research on optimization of the splicing process in the electric arc of telecommunication optical fibers and erbium doped EDF fibers. The results of the calculations of diffusion coefficients GeO2 in telecommunication optical fibers and diffusion coefficients Er and Al2O3 (together) in the fiber EDF are presented. Diffusion coefficients were determined for the fusion temperature in the electric arc ?2000°C, on the basis of changes, along the splice, of spliced thermoluminescence intensity profiles of the fibers. On the basis of knowledge of diffusion coefficients simulation calculation of loss joints of MC SMF fiber (Matched Cladding Single Mode Fiber - SiO2: GeO2) and NZDS SMF (Non Zero Dispersion Shifted - Single Mode Fiber - SiO2: GeO2) with EDF (Erbium Doped Fiber - SiO2: Al2O3, Er) was performed and presented as a function of diffusion time. Experimental studies of optimization of thermal connected MC SMF and NZDS SMF with EDF were presented and compared with theoretical results. This paper presents the results of microscopic observations of defects and diffusion, and X-ray microanalysis in the spliced areas of single-mode telecommunication optical fibers: MC SMF, NZDS-SMF and erbium doped active single mode optical fibers. Studies were performed with the use of the scanning electron microscope JSM5800LV and JSM6610A microscope equipped with EDS X-ray spectrometer. Results showing the influence of heating time on the diffusion of core dopants and the formation of deformations in the splice areas were presented.

5

Reflectometric measurements of thermally expanded core area

Ratuszek M., Zakrzewski Z., Majewski J.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2010

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Vol. 58, nr 4

513-517

EN

In this work an analysis method of one-way optical time domain reflectometer (OTDR) measurements has been presented. This method uniquely confirms mode field radii matching in diffusion transit area of the thermally expanded core (TEC) of thermally connected single mode telecommunication fibers. A comparison of reflectometric measurements with theoretical calculations of losses in TEC areas has been demonstrated.