Couche transport

Résumé

thumb|Position de la couche transport dans le modèle ISO et dans TCP-IP En réseaux, la couche dite de transport constitue la quatrième couche du modèle OSI. Cette couche regroupe l'ensemble des protocoles chargés de la gestion des erreurs et du contrôle des flux réseaux. Les deux principaux protocoles utilisés sont les protocoles TCP et UDP. Définition OSI (ISO 7498-1) Modèle OSI La couche transport gère les communications de bout en bout entre processus. Cette couche est souvent la plus haute couche où on se préoccupe de la correction des erreurs. C'est-à-dire que le service de niveau transport consiste généralement en un service en mode connecté offrant le transfert de messages ou d'octets bruts ordonnés sans corruption, pertes, ou duplication. En particulier, c'est le service offert par les protocoles TCP. Principe de fonctionnement Multiplexage / Démultiplexage La couche transport implémente le multiplexage afin de permettre à plusieurs processus

Source officielle

https://fr.wikipedia.org/wiki/Couche_transport

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Consensus protocol have seen increased usage in recent years due to the industry shift to distributed computing. However, it has traditionally been implemented in the application layer. We propose to move the consensus protocol in the transport layer, to offer reliable ordered delivery of messages to applications. Our implementation builds on R2P2, a novel RPC framework for datacenter applications. It can run both using Linux UDP sockets or kernel bypass using DPDK. We observe tail latency increase of only 10 μs and a throughput loss of only 13% compared to the unreplicated application, showing that easy-to-use consensus can also have high performance.

2019

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EPFL1997

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We study the effect of deployment of low cost, low power micro base stations along with macro base stations on energy consumption and capacity of downlink LTE. [1] studied this problem, using spectral area efficiency as the performance metric. We show that the analysis proposed in [1] is inaccurate as the traffic layer specifications of LTE networks is not included in the analysis. We also investigate the effect of user association and frequency band allocation schemes on energy consumption and capacity of LTE networks. Specifically, we add the following three important elements to the analysis proposed in [1]: a traffic layer analysis that take both the physical and traffic layer specifications of LTE downlink into account; a threshold-based policy to optimally associate users to base stations; and an allocation scheme to better allocate the frequency band to macro and micro base stations. We investigate all combinations of these elements through numerical evaluation and observe that 1. there are important differences between traffic layer and physical layer analysis, 2. threshold-based user association policy improve the traffic capacity of the network by up to 33% without affecting the energy profile of the network, and 3. considerable energy saving and capacity gain can be achieved thought a careful allocation of the frequency band to macro and micro base stations. Finally, we determine the optimal network configuration and show that up to 46% saving in energy can be achieved compared to the case that no micro base stations are deployed in the network.

Acm Order Department, P O Box 64145, Baltimore, Md 21264 Usa2011

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