Performance Characterization and Profiling of Chained CPU-bound Virtual Network Functions

The increased demand for high-quality Internet connectivity resulting from the growing number of connected devices and advanced services has put significant strain on telecommunication networks. In response, cutting-edge technologies such as Network Function Virtualization (NFV) and Software Defined Networking (SDN) have been introduced to transform network infrastructure. These innovative solutions offer dynamic, efficient, and easily manageable networks that surpass traditional approaches. To fully realize the benefits of NFV and maintain the performance level of specialized equipment, it is critical to assess the behavior of Virtual Network Functions (VNFs) and the impact of virtualization overhead. This paper delves into understanding how various factors such as resource allocation, consumption, and traffic load impact the performance of VNFs. We aim to provide a detailed analysis of these factors and develop analytical functions to accurately describe their impact. By testing VNFs on different testbeds, we identify the key parameters and trends, and develop models to generalize VNF behavior. Our results highlight the negative impact of resource saturation on performance and identify the CPU as the main bottleneck. We also propose a VNF profiling procedure as a solution to model the observed trends and test more complex VNFs deployment scenarios to evaluate the impact of interconnection, co-location, and NFV infrastructure on performance

High time-resolved measurements of fine aerosol (PM2.5) in a hot-spot area during wintertime: multi-wavelength optical absorption properties and source apportionment

Black Carbon (BC) is the main absorber of solar radiation among the aerosol components, it influences cloud processes, and alters the melting of snow and ice cover. Although it is one of the most important individual climate-warming components, uncertainties on the radiative forcing related to BC-radiation interaction still cover more than one order of magnitude. Moreover, weakly absorbing organic material (brown carbon, BrC) in the form of particle coating or as particle as-is can be considered a further important contributor to aerosol absorption. The peculiarity of BrC is that it is very effective in the absorption of short-\u3bb radiation whereas its contribution to aerosol absorption is negligible in the red or near-IR bands. It is noteworthy that BC and BrC can also be used for source apportionment purposes (e.g. they can be helpful for the discrimination between fossil fuels combustion vs. biomass burning). Thus, aerosol absorption properties possibly related to mixing and/or size information, and BC content are currently of great interest. Moving in this frame, a multi-\u3bb polar photometer (PP_UniMI) has been developed at the Department of Physics of the University of Milan in the last years. The instrument is based on the measurement on the scattering plane of the light transmitted and scattered in the forward and back hemispheres by unloaded and loaded samples using a rotating photodiode. Data reduction aiming at the determination of the sample absorbance follows Petzold et al. (2004) and therein cited literature. Currently, PP_UNIMI allows performing 4-\u3bb measurements (870, 633, 532, 405 nm) on aerosol collected on different substrates, including aerosol collected with high-time resolution using a streaker sampler. Such sampler collects aerosol segregated in two size-classes (fine and coarse) on a rotating frame with hourly resolution. The set-up of the instrument was validated against independent measurements carried out using a Multi-Angle Absorption Photometer for what concerns the red-light results, considering possible artefact effects shown in Vecchi et al. (2013). The results presented here are related to the analysis of the high time-resolved trends of multiwavelength aerosol absorption properties measured on the fine aerosol fraction during a field campaign performed in Milan (Italy) in November 2015 (see an example in Figure 1). Such data will be used to test the possibility of applying source apportionment models based on optical properties (es. Aethalometer model) using off-line hightime resolved data. It is also noteworthy that equivalent BC can be quantified from the polar photometer measurements at 635 nm using a suitable mass absorption coefficient. Such information will be joined to the elemental components (Na-Pb) detected by Particle-Induced X-ray Emission technique carried out at the INFN-LABEC in Florence to perform receptor modelling analysis (e.g. Positive Matrix Factorization). The results of the source apportionment using such data will be also presented

Effects of Road Dust Suppressants on PM Levels in a Mediterranean Urban Area

The abatement of road dust emissions is currently a major challenge for sustainable transportation, causing exceedances of limits on particulate matter (PM) and high population exposures to mineral dust and metals. Mitigation measures have been proposed such as improved street cleaning and the use of dust suppressants. This study evaluated, for the first time, the effectiveness of calcium-magnesium acetate (CMA) and MgCl2 in reducing road dust emissions in a Mediterranean city. During a two-month campaign, a typical urban road in the city of Barcelona was sprayed, and changes in PMx levels and components were monitored at four traffic sites and one background monitoring sites. The integrated results indicate no statistically significant effectiveness of dust suppressants on PM10 and PM2.5-10 levels. Episodic reductions of Al, K, Mg, Cr, Li, Cu, and Zn were observed during CMA applications, but they were not systematically statistically significant over different stations and spreading days. MgCl2 days showed lower PM10 mean concentrations, but these reductions were not statistically significant and were not supported by significant drops in mineral and brake-wear metals. Based on our literature review, it can be postulated that the higher the road dust loading, the higher the dust suppressant effectiveness

Saharan dust impact in central Italy: An overview on three years elemental data records

In southern European countries, Saharan dust may episodically produce significant increases of PM10, which may also cause the exceedance of the PM10 daily limit value established by the European Directive (2008/50/EC). The detection with very high sensitivity of all the elements that constitute mineral dust makes PIXE technique a very effective tool to assess the actual impact of these episodes. In this work, a review of long-term series of elemental concentrations obtained by PIXE has been accomplished with the aim of identifying the occurrence of Saharan dust transport episodes over long periods in Tuscany and characterising them in terms of composition and impact on PM concentration, tracing back their contribution to the exceedances of the PM10 limit value. The impact of the different Saharan intrusions on PM10 showed a very high variability. During the most intense episodes (which occurred with a frequency of few times per year) the calculated soil dust concentration reached values as high as 25\u201330 \u3bcg m 123, to be compared with background values of the order of 5 \u3bcg m 123. The Saharan dust contribution was decisive to cause the exceedance of the PM10 daily limit value in the 1\u20132% of the days considered in the present work

impact of traffic flows and meteorological events on the hourly elemental composition of fine and coarse particles at an urban site

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