Partage de fichiers | EPFL Graph Search

Le partage de fichiers est une technique de transfert de fichier consistant à distribuer ou à donner accès, à distance, à des données numériques à travers un réseau informatique. Il peut s'agir de fichiers de toutes sortes : logiciels, livres, vidéo, audio etc. Deux techniques de partage de fichiers existent actuellement :

l'hébergement centralisé (modèle client-serveur) permet de stocker les données sur un serveur de fichiers unique et d'y accéder sur celui-ci depuis un autre ordinateur (dit le client).
la technique pair-à-pair qui consiste à mettre des données en partage suivant un modèle de réseau informatique où chaque ordinateur client est aussi un serveur;

Le partage en pair-à-pair Partage de fichiers en pair à pair Pair à pair Le partage centralisé Ce type de partage existe tant sur des réseaux fermés qu'ouverts. Le plus connu est l'Hébergement Internet, sur un serveur de fichiers faisant partie du World wide web. La transmission et l'accès aux don

Denial-of-service resilience in peer-to-peer file sharing systems

Dan Mihai Dumitriu, Willy Zwaenepoel

Peer-to-peer (p2p) file sharing systems are characterized by highly replicated content distributed among nodes with enormous aggregate resources for storage and communication. These properties alone are not sufficient, however, to render p2p networks immune to denial-of-service (DoS) attack. In this paper, we study, by means of analytical modeling and simulation, the resilience of p2p file sharing systems against DoS attacks, in which malicious nodes respond to queries with erroneous responses. We consider the filetargeted attacks in current use in the Internet, and we introduce a new class of p2p-network-targeted attacks. In file-targeted attacks, the attacker puts a large number of corrupted versions of a single file on the network. We demonstrate that the effectiveness of these attacks is highly dependent on the clients’ behavior. For the attacks to succeed over the long term, clients must be unwilling to share files, slow in removing corrupted files from their machines, and quick to give up downloading when the system is under attack. In network-targeted attacks, attackers respond to queries for any file with erroneous information. Our results indicate that these attacks are highly scalable: increasing the number of malicious nodes yields a hyperexponential decrease in system goodput, and a moderate number of attackers suffices to cause a near-collapse of the entire system. The key factors inducing this vulnerability are (i) hierarchical topologies with misbehaving “supernodes,” (ii) high path-length networks in which attackers have increased opportunity to falsify control information, and (iii) power-law networks in which attackers insert themselves into high-degree points in the graph. Finally, we consider the effects of client counter-strategies such as randomized reply selection, redundant and parallel download, and reputation systems. Some counter-strategies (e.g., randomized reply selection) provide considerable immunity to attack (reducing the scaling from hyperexponential to linear), yet significantly hurt performance in the absence of an attack. Other counter-strategies yield little benefit (or penalty). In particular, reputation systems show little impact unless they operate with near perfection.

2005

The Advent of the Sharing Culture and its Effect on Product Pricing

Maryam Razeghian Jahromi, Thomas Alois Weber

Empirical observations suggest that consumers' propensity towards sharing varies with culture and the individuals' socio-demographic characteristics. In an economy with overlapping generations of heterogeneous consumers, we study optimal dynamic selling by a durable-goods monopolist in equilibrium. Feasible dynamic pricing strategies include second-degree price discrimination offering intertemporal consumption bundles in the form of rental and/or purchase options. We find that as the population's peer-trade propensity increases, possibly due to a cultural shift from private ownership to collective consumption, the durable-goods monopolist's optimal strategy shifts from unbundling (offering exclusively rentals), via mixed bundling (offering the options of rental and purchase side-by-side), to pure bundling (offering purchase only). We show that an increase in peer-trade propensity has an ambiguous effect on the firm's profit. Cultural shifts from low to high peer-trade propensity may be delayed by a firm's attempts to artificially disable sharing markets by offering overly low rental rates. However, beyond a certain threshold of peer-trade propensity, the firm prefers a cultural transition to an access-based economy. The underlying reason is that the asset base of a sharing economy ultimately depends on the firm's output, so that a portion of the anticipated rents from sharing can be captured by the durable-goods monopolist.

2019

Extending Peer-to-Peer Networks for Approximate Search

Ion Constantinescu, Alain Mowat, Roman Schmidt, Michael Ignaz Schumacher

Peer-to-Peer (P2P) networks are used worldwide for many applications such as file sharing or news servers. There are many different implementations available, each with its pros and cons. In this paper, we propose a way to enable approximate queries in a P2P network by using a special encoding function and error correcting codes. The encoding function maintains neighborhood relationships so that two similar inputs will result in two similar outputs. The error correcting code is then used to group the similar encoded values around special codewords. In this manner, similar content is located as close as possible in the network. The algorithm is tested in a simulated environment on a HyperCube type network overlay in order to see if it can be a viable solution in a real network.

2008

Denial-of-service resilience in peer-to-peer file sharing systems

Dan Mihai Dumitriu, Willy Zwaenepoel

2005