Mathematical analysis of scheduling policies in peer-to-peer video streaming networks

Las redes de pares son comunidades virtuales autogestionadas, desarrolladas en la capa de aplicación sobre la infraestructura de Internet, donde los usuarios (denominados pares) comparten recursos (ancho de banda, memoria, procesamiento) para alcanzar un fin común. La distribución de video representa la aplicación más desafiante, dadas las limitaciones de ancho de banda. Existen básicamente tres servicios de video. El más simple es la descarga, donde un conjunto de servidores posee el contenido original, y los usuarios deben descargar completamente este contenido previo a su reproducción. Un segundo servicio se denomina video bajo demanda, donde los pares se unen a una red virtual siempre que inicien una solicitud de un contenido de video, e inician una descarga progresiva en línea. El último servicio es video en vivo, donde el contenido de video es generado, distribuido y visualizado simultáneamente. En esta tesis se estudian aspectos de diseño para la distribución de video en vivo y bajo demanda. Se presenta un análisis matemático de estabilidad y capacidad de arquitecturas de distribución bajo demanda híbridas, asistidas por pares. Los pares inician descargas concurrentes de múltiples contenidos, y se desconectan cuando lo desean. Se predice la evolución esperada del sistema asumiendo proceso Poisson de arribos y egresos exponenciales, mediante un modelo determinístico de fluidos. Un sub-modelo de descargas secuenciales (no simultáneas) es globalmente y estructuralmente estable, independientemente de los parámetros de la red. Mediante la Ley de Little se determina el tiempo medio de residencia de usuarios en un sistema bajo demanda secuencial estacionario. Se demuestra teóricamente que la filosofía híbrida de cooperación entre pares siempre desempeña mejor que la tecnología pura basada en cliente-servidor

Применение жидкостных моделей к анализу одноранговой сети

The application of the fluid models to the analysis of the streams in information and communication networks is presented. The models, considered in the paper, take into account the specificities of widespread P2P networks (peer-to-peer), used for file-sharing, parallel computing, IP telephony, video streaming, etc. The review of the main types of P2P networks and their associated analytical models are presented in the paper. The fluid models, presented in the paper, describe network traffic in terms of the changes over time data stream rates between users and in terms of the number of network users. The first model is a system of ordinary differential equations and allows to analyze the average file download time. The second model is the extension of the first model and is represented in the form of partial differential equation. It takes into account a random amount of data requested by users. It can be used to analyze both the transient state and steady state during the download. This model is suitable to study the behavior of the system with a large number of users. In addition to the average download time the second model, taking into account the population in the network, allows to analyze such parameters of the network performance as the number of leechers and seeders in the network.В статье показано применение жидкостных моделей к анализу потоков в инфокоммуникационных сетях. Модели, исследованные в статье, учитывают особенности получивших широкое распространение одноранговых Р2Р-сетей, использующихся для обмена файлами, параллельных вычислений, IP-телефонии, передачи потокового видео и др. В статье проведён обзор основных типов P2P-сетей и связанных с ними аналитических моделей. В построенных в статье жидкостных моделях сетевой трафик описывается в терминах изменения во времени скоростей потоков данных между пользователями и числа пользователей сети. Первая модель представляет собой систему обыкновенных дифференциальных уравнений и позволяет анализировать среднее время загрузки файла. Вторая модель в виде дифференциального уравнения в частных производных является расширением первой и учитывает случайный объем данных, запрашиваемых пользователями. Она может быть использована для анализа как устойчивого состояния системы при загрузке, так и неустановившегося состояния, и подходит для исследования поведения системы при большом числе пользователей. Помимо среднего времени загрузки файла вторая модель, учитывающая состав присутствующих в сети пользователей, позволяет анализировать такие показатели эффективности сети, как число личеров и сидов в сети

Social Software, Groups, and Governance

Formal groups play an important role in the law. Informal groups largely lie outside it. Should the law be more attentive to informal groups? The paper argues that this and related questions are appearing more frequently as a number of computer technologies, which I collect under the heading social software, increase the salience of groups. In turn, that salience raises important questions about both the significance and the benefits of informal groups. The paper suggests that there may be important social benefits associated with informal groups, and that the law should move towards a framework for encouraging and recognizing them. Such a framework may be organized along three dimensions by which groups arise and sustain themselves: regulating places, things, and stories

Cognitive networking techniques on content distribution networks

First we want to design a strategy based on Artificial Intelligence (AI) techniques with the aim of increasing peers download performance. Some AI algorithms can find patterns in the information available to a peer locally, and use it to predict values that cannot be calculated by means of mathematical formulas. An important aspect of these techniques is that can be trained in order to improve its interpretation of the local available information. With this process they can make more accurate predictions and perform better results. We will use this prediction system to increase our knowledge about the swarm and the peers who are part of it. This global knowledge increase can be used to optimize the algorithms of BitTorrent and can represent a great improvement in peers download capacity. Our second challenge is to create a reduced group of peers (Crowd) that focus their efforts on improving the condition of the swarm through collaborative techniques. The basic idea of this approach is to organize a group of peers to act as a single node and focus them on getting all pieces of the content they are interested in. This involves avoiding, as far as possible, to download pieces that any of the members already have. The main goal of this technique consists of reaching as quickly as possible a copy of the content distributed between all members of the Crowd. Getting a distributed copy of the content is expected to increase the availability of parts and reduce dependence on the seeds (users who have the complete content), which would represent a great benefit for the whole swarm. Another aspect that we want to investigate is the use of a priority system among members of the Crowd. We consider that in certain situations to prioritize the Crowd peers at expense of regular peers can result in a significant increase of the download ratio

CHORUS Deliverable 2.2: Second report - identification of multi-disciplinary key issues for gap analysis toward EU multimedia search engines roadmap

After addressing the state-of-the-art during the first year of Chorus and establishing the existing landscape in multimedia search engines, we have identified and analyzed gaps within European research effort during our second year. In this period we focused on three directions, notably technological issues, user-centred issues and use-cases and socio- economic and legal aspects. These were assessed by two central studies: firstly, a concerted vision of functional breakdown of generic multimedia search engine, and secondly, a representative use-cases descriptions with the related discussion on requirement for technological challenges. Both studies have been carried out in cooperation and consultation with the community at large through EC concertation meetings (multimedia search engines cluster), several meetings with our Think-Tank, presentations in international conferences, and surveys addressed to EU projects coordinators as well as National initiatives coordinators. Based on the obtained feedback we identified two types of gaps, namely core technological gaps that involve research challenges, and “enablers”, which are not necessarily technical research challenges, but have impact on innovation progress. New socio-economic trends are presented as well as emerging legal challenges