The rapid increase of content delivery over the Internet has lead to the proliferation of content distribution networks (CDNs). Management of CDNs requires algorithms for request routing, content placement, and eviction in such a way that user delays are small. Our objective in this work is to design feasible algorithms that solve this trio of problems. We abstract the system of front-end source nodes and back-end caches of the CDN in the likeness of the input and output nodes of a switch. In this model, queues of requests for different pieces of content build up at the source nodes, which route these requests to a cache that contains the content. For each request that is routed to a cache, a corresponding data file is transmitted back to the source across links of finite capacity. Caches are of finite size, and the content of the caches can be refreshed periodically. A requested but missing item is fetched to the cache from the media vault of the CDN. In case of a lack of adequate space at the cache, an existing, unrequested item may be evicted from the cache in order to accommodate a new item. Every such cache refresh or media vault access incurs a finite cost. Hence the refresh periodicity allowed to the system represents our system cost. In order to obtain small user delays, our algorithms must consider the lengths of the request queues that build up at the nodes. Stable policies ensure the finiteness of the request queues, while good polices also lead to short queue lengths. We first design a throughput-optimal algorithm that solves the routing-placement eviction problem using instantaneous system state information. The design yields insight into the impact of different cache refresh and eviction policies on queue length. We use this and construct throughput optimal algorithms that engender short queue lengths. We then propose a regime of algorithms which remedies the inherent problem of wastage of capacity. We also develop heuristic variants, and we study their performance. We illustrate the potential of our approach and validate all our claims and results through simulations on different CDN topologies.

Le grand nombre d’appareils connectés combiné au volume croissant de trafic ont poussé les réseaux dans leurs derniers retranchements. Pour résoudre ce problème, l’approche “Software-Defined Networking” (SDN) qui découple le plan de contrôle du plan de données a été proposée. OpenFlow est un nouveau protocole qui réalise le concept SDN. Pour traiter ces flux, OpenFlow utilise des listes de règles sur les commutateurs. Ces règles sont utilisées pour déterminer les actions dans le réseau. Ceci permet de simplifier la mise en place de services réseaux complexes mais soulève la question de savoir quelles règles définir et où les placer dans le réseau afin d’en respecter ses contraintes. Dans cette thèse, nous nous concentrons sur le problème de placement de règles dans OpenFlow (ORPP) et proposons une abstraction de type boite noire afin de masquer la gestion du réseau. Tout d'abord, nous formalisons le problème de placement de règles et faisons une étude des solutions existantes. Les solutions existantes sont cependant inefficaces car elles reposent majoritairement sur le concept du plus court chemin. Nous proposons de relaxer le problème en autorisant l’utilisation de chemins arbitraires et proposons deux algorithmes complémentaires : OFFICER et aOFFICER. L'idée générale d’OFFICER et aOFFICER est d’utiliser les chemins les plus efficaces pour le trafic de haute importance et autoriser le trafic de plus basse importance à suivre des détours. Ces deux propositions sont évaluées en utilisant des traces de trafic. Finalement, nous appliquons le principe de la boite noire pour améliorer les performances d'un service de diffusion de contenus dans les réseaux cellulaires / The massive number of connected devices combined with an increasing traffic push network operators to their limit by limiting their profitability. To tackle this problem, Software-Defined Networking (SDN), which decouples network control logic from forwarding devices, has been proposed. An important part of the SDN concepts is implemented by the OpenFlow protocol that abstracts network communications as flows and processes them using a prioritized list of rules on the network forwarding elements. While the abstraction offered by OpenFlow allows to implement many applications, it raises the new problem of how to define the rules and where to place them in the network while respecting all requirements, which we refer as the OpenFlow Rules Placement Problem (ORPP). In this thesis, we focus on the ORPP and hide the complexity of network management by proposing a black box abstraction. First, we formalize that problem, classify and discuss existing solutions. We discover that most of the solutions enforce the routing policy when placing rules, which is not memory efficient in some cases. Second, by trading routing for better resource efficiency, we propose OFFICER and aOFFICER, two frameworks that select OpenFlow rules satisfying policies and network constraints, while minimizing overheads. The main idea of OFFICER an aOFFICER is to give high priority for large flows to be installed on efficient paths, and let other flows follow default paths. These proposals are evaluated and compared to existing solutions in realistic scenarios. Finally, we study a use case of the black box abstraction, in which we improve the performance of content delivery services in cellular networks