k-clique Communities in the Internet AS-level

A signicant challenge for researchers analysing the Internet AS-level topology graph is how to interpret the global organization of the graph as the coexistence of its structural blocks (communities) associated with more highly interconnected parts. While a huge number of papers have already been published on the issue of community detection, very little attention has so far been devoted to the discovery and interpretation of Internet communities at the various levels of abstractions. We believe that by discovering and interpreting a priori these unknown building blocks (i.e. communities), this will then pave the way for new types of analysis which are crucial in understanding of the structural and functional properties of the Internet at least at the AS level of abstraction. We thus propose a novel type of analysis of the Internet AS-level topology graph by exploiting the k-clique community denition. First, we show that detected communities can be described by a tree representation. Then we show the presence of two classes of k-clique communities: those that are strictly aected by the nesting process which is embedded in the k-clique community denition, and, on the other hand, those that appear as branches in the tree. We conclude our analysis by highlighting the properties that characterize k-clique communities with dierent k values by exploiting both geographical data and information related to IXPs

k-dense Communities in the Internet AS-Level Topology

Extracting a set of well connected subgraphs as com- munities from the Internet AS-level topology graph is crucially important for assessing the performance of protocols and routing algorithms, for designing ecient networks, and for evaluating the impact of failures. A huge number of community extraction methods have been proposed in the literature, among which the k-core decomposition and the k-clique community extraction methods. The former method is computationally e- cient, but it only discovers coarse-grained and loosely connected communities. On the other hand, k-clique can extract ne-grained and tightly connected communities, but is NP hard and therefore useless for analyzing the Internet AS-level topology graph. In the paper we inves- tigate the Internet structure by exploiting an ecient algorithm for extracting k-dense communities, where a k-clique community implies a k-dense community, which in turn implies a k-core community. The paper provides two innovative contributions. The rst is the application of the k-dense method to the Internet AS-level topology graph - obtained from the CAIDA, DIMES and IRL datasets - to identify well- connected communities and to analyze how these are connected to the rest of the graph. The second contribution relates to the study of the most well-connected communities with the support of two additional datasets: a geographical dataset (which lists, for each AS, the countries in which it has at least one geographical location) and the IXP dataset (which maintains, for each IXP, its geographical position and the list of its participants). We found that the k-max- dense community holds a central position in the Internet AS-level topology graph structure since its 101 ASs (less than the 0.3% of Internet ASs) are involved in more than 39% of all Internet connections. We also found that those ASs are connected to at least one IXP and have at least one geographical location in Europe (only 70.3% of them have at least one additional geographical location outside Europe)

k-Dense communities in the Internet AS-level topology graph

In this paper we investigate the structure of the Internet by exploiting an efficient algorithm for extracting k-dense communities from the Internet AS-level topology graph. The analyses showed that the most well-connected communities consist of a small number of ASs characterized by a high level of clusterization, although they tend to direct a lot of their connections to ASs outside the community. In addition these communities are mainly composed of ASs that participate at the Internet Exchange Points (IXPs) and have a worldwide geographical scope. Regarding k-max-dense ASs we found that they play a primary role in the Internet connectivity since they are involved in a huge number of Internet connections (42% of Internet connections). We also investigated the properties of three classes of k-max-dense ASs: Content Delivery Networks, Internet Backbone Providers and Tier-1s. Specifically, we showed that CDNs and IBPs heavily exploit IXPs by participating in many of them and connecting to many IXP participant ASs. On the other hand, we found that a high percentage of connections originated by Tier-1 ASs are likely to involve national ASs which do not participate at IXPs

An Assessment of a Model for Error Processing in the CMS Data Acquisition System

The CMS Data Acquisition System consists of O(20000) interdependent services. A system providing exception and application-specific monitoring data is essential for the operation of such a cluster. Due to the number of involved services the amount of monitoring data is higher than a human operator can handle efficiently. Thus moving the expert-knowledge for error analysis from the operator to a dedicated system is a natural choice. This reduces the number of notifications to the operator for simpler visualization and provides meaningful error cause descriptions and suggestions for possible countermeasures. This paper discusses an architecture of a workflow-based hierarchical error analysis system based on Guardians for the CMS Data Acquisition System. Guardians provide a common interface for error analysis of a specific service or subsystem. To provide effective and complete error analysis, the requirements regarding information sources, monitoring and configuration, are analyzed. Formats for common notification types are defined and a generic Guardian based on Event-Condition-Action rules is presented as a proof-of-concept

The Impact of IXPs on the AS-level Topology Structure of the Internet

The AS-level topology of the Internet has been quite a hot research topic in the last few years. However, only a small number of studies have been developed that give a structural interpretation of this graph. Such an interpretation is crucially important in order to test protocols and optimal routing algorithms, to design efficient networks, and for failure detection purposes. Moreover, most research does not highlight the role that IXPs have on the AS-level structure of the Internet, although their role is recognized as fundamental. The initial contribution of this study is an analysis of the most important AS-level topologies that are publicly found on the web and an analysis of the topology obtained when they are merged. We compiled structural information from this topology making considerable use of the k-core decomposition technique to delineate various particular classes of nodes. Next, we associated node properties with a reasonable modus operandi of the ASs on the Internet. The second contribution is a study of the impact that ASs connected to IXPs and BGP connections crossing IXPs have on the AS-level topology. To achieve this, we developed a procedure to gather reliable information related to IXPs and their participants

Effective Maxwell's equations in general periodic microstructures

We study the time harmonic Maxwell equations in a meta-material consisting of perfect conductors and void space. The meta-material is assumed to be periodic with period $\eta > 0$; we study the behaviour of solutions $(E^{\eta}, H^{\eta})$ in the limit $\eta \to 0$ and derive an effective system. In geometries with a non-trivial topology, the limit system implies that certain components of the effective fields vanish. We identify the corresponding effective system and can predict, from topological properties of the meta-material, whether or not it permits the propagation of waves

Lineamientos generales para una propuesta didáctica de Filosofía Política

Al enseñar filosofía surge una serie de preguntas ineludibles: qué enseñar, cómo y para qué. En este trabajo intentaremos responder a estos interrogantes didácticos, centrándonos específicamente en la enseñanza de la Filosofía Política en el Bachillerato de Bellas Artes.En particular, en el presente artículo se propondrán ciertos lineamientos con el objetivo de incluir una unidad de Filosofía Política en los programas de séptimo año de la mencionada institución empleando como marco teórico a la hermenéutica de Gadamer, la cual representa a nuestro entender un enriquecimiento de la modalidad histórica propuesta por G. Obiols y A. Cerletti para la enseñanza de la filosofía

La actualidad de la retórica: el análisis de las pasiones en los discursos políticos

La retórica en tanto disciplina vinculada a la práctica argumentativa ha sido obviada históricamente de los planes de estudio de lógica de los colegios secundarios. Excede a nuestra intención dar cuenta de las razones por las cuales esto ha sucedido pero entendemos que este tipo de análisis es un complemento necesario de un estudio comprehensivo de las prácticas argumentativas, en el marco del enfoque pragma dialéctico adoptado hace unos años en algunos colegios preuniversitarios de la Universidad Nacional de La Plata.Colegio Nacional "Rafael Hernández

General guidelines for a didactical proposal of political philosophy

Al enseñar filosofía surge una serie de preguntas ineludibles: qué enseñar, cómo y para qué. En este trabajo intentaremos responder a estos interrogantes didácticos, centrándonos específicamente en la enseñanza de la Filosofía Política en el Bachillerato de Bellas Artes. En particular, en el presente artículo se propondrán ciertos lineamientos con el objetivo de incluir una unidad de Filosofía Política en los programas de séptimo año de la mencionada institución empleando como marco teórico a la hermenéutica de Gadamer, la cual representa a nuestro entender un enriquecimiento de la modalidad histórica propuesta por G. Obiols y A. Cerletti para la enseñanza de la filosofía.Why, how and what to teach are some inescapable questions when trying to impart philosophy. In this study, we aimed to answer these questions by focusing on the school teaching of Political Philosophy at the Bachillerato de Bellas Artes. Particularly, we propose some guidelines with the aim of including a Political Philosophy subject in the last degree of that institution. We used Gadamer’s hermeneutics as the theoretical framework, which represents an improvement to the G. Obiols’and A. Cerletti’s historical approach.Bachillerato de Bellas Artes "Prof. Francisco A. De Santo