Processus collaboratif pair à pair

Le processus collaboratif pair à pair () décrit une forme décentralisée de travail collaboratif reposant sur des principes proches des réseaux informatique pair-à-pair. Les collaborateurs ne sont pas soumis à une autorité hiérarchique et chacun est libre de contribuer sans sélection préalable. Ils sont unis par un projet commun ou un bien commun que peut produire le groupe. Enfin, il n'existe pas de collaborateurs indispensables, même s'il peut exister des plus ou moins gros contributeurs. Références * Catégorie:Organisation sociale Catégorie:Travail

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Optimal Scheduling of Peer-to-Peer File Dissemination

Jochen Mundinger

Peer-to-peer (P2P) overlay networks such as BitTorrent and Avalanche are increasingly used for disseminating potentially large files from a server to many end users via the Internet. The key idea is to divide the file into many equally-sized parts and then let users download each part (or, for network coding based systems such as Avalanche, linear combinations of the parts) either from the server or from another user who has already downloaded it. However, their performance evaluation has typically been limited to comparing one system relative to another and typically been realized by means of simulation and measurements. By contrast, we provide an analytic performance analysis that is based on a new uplink-sharing version of the well-known broadcasting problem. Assuming equal upload capacities, we show that the minimal time to disseminate the file is the same as for the simultaneous send/receive version of the broadcasting problem. For general upload capacities, we provide a mixed integer linear program (MILP) solution and a complementary fluid limit solution. We thus provide a lower bound which can be used as a performance benchmark for any P2P file dissemination system. We also investigate the performance of a decentralized strategy, providing evidence that the performance of necessarily decentralized P2P file dissemination systems should be close to this bound and therefore that it is useful in practice.

2007

Chargement

Analysis of Peer-to-Peer File Dissemination amongst Users of Different Upload Capacities

Jochen Mundinger

In recent years, overlay networks have proven an effective way of disseminating a file from a single source to a group of end users via the Internet. A number of algorithms and protocols have been suggested, implemented and studied. In particular, much attention has been given to peer-to-peer (P2P) systems such as BitTorrent, Slurpie, SplitStream and Bullet. The key idea is that the file is divided into M parts of equal size and that a given user may download any one of these either from the server or from a peer who has previously downloaded it. More recently, a scheme based on network coding has been suggested. Here, users download linear combinations of file parts rather than individual file parts. Performance evaluation of such systems has typically been limited to comparing one system relative to another. Our results give the minimal time required to fully disseminate a file of M parts from a server to N end users. In the scheduling literature this completion time is referred to as makespan. We thus provide a lower bound which can be used as a performance benchmark for any P2P file dissemination system.

2006

Chargement

Analysis of peer-to-peer file dissemination

Jochen Mundinger

In recent years, overlay networks have proven a popular way of disseminating potentially large files from a single server S to a potentially large group of N end users via the Internet. A number of algorithms and protocols have been suggested, implemented and studied. In particular, much attention has been given to peer-to-peer (P2P) systems such as BitTorrent, Slurpie, SplitStream, Bullet and Avalanche. The key idea is that the file is divided into M parts of equal size and that a given user may download any one of these -- or, for Avalanche, linear combinations of these -- either from the server or from a peer who has previously downloaded it. However, performance analysis of P2P systems for file dissemination has typically been limited to comparing one system relative to another and typically been realized by means of simulations and measurements. We give the minimal time to fully disseminate the file of M parts from a server to N end users in a centralized scenario. In the scheduling literature this completion time is referred to as makespan. We thereby provide a lower bound which can be used as a performance benchmark for any P2P file dissemination system. We also investigate the part of the loss in efficiency that is due to the lack of centralized control in practice. Using simulation as well as direct computation, we show that even a simple and natural randomized strategy disseminates the file in an expected time that grows with N in a similar manner to the minimal time achieved with a centralized controller. This suggests that the performance of necessarily decentralized P2P file dissemination systems should still be close to our performance bound.

2006

Chargement

Économie planifiée

La « planification impérative de l'économie » est dirigée, généralement à l’échelle d’un État, au moyen d’un plan fixant les objectifs de production sur une période annuelle ou pluriannuelle. Autrem

Production par les pairs sur la base des biens communs

La production par les pairs sur la base des biens communs (en anglais : , CBPP) est un modèle de production socio-économique dans lequel un grand nombre de personnes travaillent en coopération (géné

Socialisme

alt=Drapeau rouge du socialisme|vignette|Le drapeau rouge est le principal symbole du socialisme et du communisme à leur commencement.Le mot socialisme recouvre un ensemble très divers de courants de

CS-487: Industrial automation

This course consists of two parts:

architecture of automation systems, hands-on lab
handling of faults and failures in real-time systems, including fault-tolerant computing