Inter-domain policy violations in multi-hop overlay routes: Analysis and mitigation

The Internet is a complex structure arising from the interconnection of numerous autonomous systems (AS), each exercising its own administrative policies to reflect the commercial agreements behind the interconnection. However, routing in service overlay networks is quite capable of violating these policies to its advantage. To prevent these violations, we see an impending drive in the current Internet to detect and filter overlay traffic. In this paper, we first present results from a case study overlay network, constructed on top of PlanetLab, that helps us gain insights into the frequency and characteristics of the different inter-domain policy violations. Further, we investigate the impact of two types of overlay traffic filtering that aim to prevent these routing policy violations: blind filtering and policy-aware filtering. We show that such filtering can be detrimental to the performance of overlay routing. We next consider two approaches that allow the overlay network to realize the full advantage of overlay routing in this context. In the first approach, overlay nodes are added so that good overlay paths do not represent inter-domain policy violations. In the second approach, the overlay acquires permits from certain ASes that allow certain policy violations to occur. We develop a single cost-sharing framework that allows the incorporation of both approaches into a single strategy. We formulate and solve an optimization problem that aims to determine how the overlay network should allocate a given budget between paying for additional overlay nodes and paying for permits (transit and exit) to ASes. We illustrate the use of this approach on our case study overlay network and evaluate its performance under varying network characteristics.     

Fast-flux hunter: a system for filtering online fast-flux botnet

Fast-flux networks is a domain name system (DNS) technique used by botnets, which is hiding some attack like phishing and malware delivery sites behind associate dynamical network of compromised hosts acting as proxies, that sometimes hosts malicious content. Detection of fast-flux networks continues to be a difficult issue attributable to the similar behavior between these networks and alternative legitimate infrastructures, like server farms and content distribution networks. This study seeks to improve the detection and prediction of the unknown “zero-day” online fast-flux botnet. This improvement will be achieved using a new system called the fast-flux hunter (FFH), which supports a new adaptive evolving fuzzy neural network algorithm. The FFH system is a hybrid between the supervised and unsupervised online knowledge-based learning systems. The core mechanism of the FFH is based on the inherent feature of the fast-flux networks. It uses a collection of DNS traffic information. The FFH is able to scan over 7615 domain records and extract 14 distinct features for each domain. The FFH decreases the classification method’s error rate. The FFH has a detection accuracy rate of approximately 98 % and is compatible with life-long learning systems, footprint-consuming memory, and high-speed systems.

     

PGD-Based Computational Vademecum for Efficient Design, Optimization and Control

In this paper we are addressing a new paradigm in the field of simulation-based engineering sciences (SBES) to face the challenges posed by current ICT technologies. Despite the impressive progress attained by simulation capabilities and techniques, some challenging problems remain today intractable. These problems, that are common to many branches of science and engineering, are of different nature. Among them, we can cite those related to high-dimensional problems, which do not admit mesh-based approaches due to the exponential increase of degrees of freedom. We developed in recent years a novel technique, called Proper Generalized Decomposition (PGD). It is based on the assumption of a separated form of the unknown field and it has demonstrated its capabilities in dealing with high-dimensional problems overcoming the strong limitations of classical approaches. But the main opportunity given by this technique is that it allows for a completely new approach for classic problems, not necessarily high dimensional. Many challenging problems can be efficiently cast into a multidimensional framework and this opens new possibilities to solve old and new problems with strategies not envisioned until now. For instance, parameters in a model can be set as additional extra-coordinates of the model. In a PGD framework, the resulting model is solved once for life, in order to obtain a general solution that includes all the solutions for every possible value of the parameters, that is, a sort of computational vademecum. Under this rationale, optimization of complex problems, uncertainty quantification, simulation-based control and real-time simulation are now at hand, even in highly complex scenarios, by combining an off-line stage in which the general PGD solution, the vademecum, is computed, and an on-line phase in which, even on deployed, handheld, platforms such as smartphones or tablets, real-time response is obtained as a result of our queries.     

A formal approach to the specification and the behavior validation of real-time systems based on rewriting logic

Design of real time and concurrent systems requires formal approaches in order to facilitate verification and validation at each step. Methods based on formal logic have been previously suggested but they often work only in a specific domain and are generally only possible with specialized users. In an attempt to overcome these two restrictions, this paper proposes a method based on rewriting logic. A grounding in theory is not a prerequisite for users. The method integrates modularity and abstraction and follows the main principles of an object-oriented approach. Different tools are available: a graphical editor for the specification of the structure and the behavior of the objects, an inference engine for rule validation and a generator of prototypes.     

Permutation flowshop scheduling problems with maximal and minimal time lags

In this paper, we study permutation flowshop problems with minimal and/or maximal time lags, where the time lags are defined between couples of successive operations of jobs. Such constraints may be used to model various industrial situations, for instance the production of perishable products. We present theoretical results concerning two-machine cases, we prove that the two-machine permutation flowshop with constant maximal time lags is strongly NP-hard. We develop an optimal branch and bound procedure to solve the m$m$-machine permutation flowshop problem with minimal and maximal time lags. We test several lower bounds and heuristics providing upper bounds on different classes of benchmarks, and we carry out a performance analysis.     

On the Capacity of Mid-latitude High Frequency Ionospheric Channel

In this paper we consider the theoretical characterization of the ionospheric transmission. More accurately, we derive a closed form expression of the average capacity for Mid-latitude High Frequency (HF) ionospheric channels. Heretofore, this problem has been studied for Rayleigh channels when each tap of the impulse response has a Rayleigh distribution without characterizing the variance of this distribution. In this paper, we extend these works to HF ionospheric channels by evaluating the variance of the amplitude attenuation versus the Doppler spread and then the channel capacity. For a multipath HF ionospheric channel, we model the Doppler phenomenon as a Gaussian profile which is suggested for HF environments. Finally, we derive a closed form expression of the average channel capacity using the probability density function (pdf) of the instantaneous impulse response. Numerical results on both simulated and real measured data are derived at the end of the paper.     

Effect of Beeswax on the Rheological Characteristics of Soft Paraffin

The effect of beeswax on the rheological characteristics of soft paraffin was investigated. The rheological parameters considered were the flow pattern, structural viscosity, yield value, plastic viscosity, coefficients B and M of thixotropic breakdown and structural recovery. Evidence is presented to show that beeswax affects markedly the rheological characteristics of soft paraffin.     

Structural and optical studies on ortho-hydroxy acetophenone azine thin films

The bulk material and deposited thin films of ortho-hydroxy acetophenone azine (o-HAcPhAz) were identified by X-ray diffraction (XRD) to be single phase polycrystalline of the monoclinic structure. The unit cell lattice constants were determined to be a = 1.578 nm, b = 1.394 nm and c = 0.64 nm, as well as its plane angles as = 90°, = 123.8° and = 90°. FTIR spectra of the bulk and thin films of the compound under investigation were assigned in the wave number range 4000–500 cm^–1. It was revealed that they were similar to each other. The optical constants (the refractive index, n, and the extinction coefficient, k) of the compound thin films were determined from the measured transmittance, T, and reflectance, R, at normal incidence of light in the spectral range 200–2100 nm. The plot of the absorption coefficient () versus h, gave three intense bands and a shoulder which were designated as A (232.3 nm), B (299.5 nm) and C (440.6 nm, 404.8 nm, sh). The observed A and B bands were attributed to * transitions, while the C-bands were attributed to * (n). The optical high frequency dielectric constant (₁, ₂) as well as the real and imaginary parts of the optical conductivity (₁, ₂) were determined. The plots of both ₁, ₂, ₁ and ₂ versus h reveal the same obtained optical transitions. Also, the relationships between both of surface, volume and surface/volume energy losses against h gave the same optical transtions.     

Potentiodynamic and cyclic voltametric studies on the Passivity of Tin in neutral phosphate buffer

Passivity of tin has been investigated in phosphate buffer (pH 6.7) using potentiodynamic and cyclic voltammetric techniques. The formation of thin transparent electronically conducting passive film on which O₂ is evolved in the transpassive range is indicated. The solution remains clear. Potentiodynamic measurements performed from −1.2 to 2.5 V (SCE) and backward at scan rates between 1 and 100 mV/sec give one anodic peak. In the reverse scanning, two cathodic peaks appear at low scan rates and disappear completely at higher rates. Values of the open dircuit potential, the corrosion potentials Ecor (forward and reverse), the anodic peak potential Ep and the anodic peak cd Ip are recorded. The results are compared with our previous work in neutral chloride, bromide, iodide, and sulphate solutions. Thermodynamic data are used to predict the possible oxidized species constituting the anode film. Cyclic voltammetric measurements have been carried out in the potential range between H₂ and O₂ evolution, and in limited potential ranges at scan rates between 1 and 200 mV/sec. One anodic peak is detected in all cases. While a short arrest and a cathodic peak appear in the results between H₂ and O₂ evolution, two distinct cathodic peaks appear up to 100 mV/sec in the results taken between –1.2 and −0.224 V. Plots of Ip vs the square root of scan rate are linear, and indicate diffusion-controlled kinetics for the reactions initiating passivity. Linear relations are observed for Ep vs log scan rate indicating the irreversible nature of the anodic processes. While the formation of SnO and SnO₂ is predicted from thermodynamics at potentials more negative than Ep, the formation of Sn(OH)₄ is predicted at potentials more positive than Ep. The conclusions drawn from the results obtained with the two different techniques are generally the same. The results are compared with and discussed on the light of previous work using cyclic voltammetry.