SQUARE: Scalable Quorum-Based Atomic Memory with Local Reconfiguration

International audienceInternet applications require more and more resources to satisfy the unpredictable clients needs. Specifically, such applications must ensure quality of service despite bursts of load. Distributed dynamic self-organized systems present an inherent adaptiveness that can face unpredictable bursts of load. Nevertheless quality of service, and more particularly data consistency, remains hardly achievable in such systems since participants (i.e., nodes) can crash, leave, and join the system at arbitrary time. The atomic consistency guarantees that any read operation returns the last written value of a data and is generalizable to data composition. To guarantee atomicity in message-passing model, mutually intersecting sets (a.k.a.quorums) of nodes are used. The solution presented here, namely SQUARE, provides scalability, load-balancing, fault-tolerance, and self-adaptiveness, while ensuring atomic consistency. We specify our solution, prove it correct and analyse it through simulations. \\ Les applications utilisées via internet nécessitent de plus en plus de ressources afin de satisfaire les besoins imprévisibles des clients. De telles applications doivent assurer une certaine qualité de service en dépit des pics de charge. Les systèmes distribués dynamiques capable de s'auto-organiser ont une capacité intrinsèque pour supporter ces pics de charge imprévisibles. Cependant, la qualité de service et plus particulièrement la cohérence des données reste très difficile à assurer dans de tels systèmes. En effet, les participants, ou noeuds, peuvent rejoindre, quitter le système, et tomber en panne de façon arbitraire. La cohérence atomique assure que toute lecture renvoie la dernière valeur écrite et la relation de composition la préserve. Afin de garantir l'atomicité dans un modèle à passage de message, des ensembles de noeuds s'intersectant mutuellement (les quorums) sont utilisés. La solution présentée ici, appelée SQUARE, est exploitable à grande échelle, permet de balancer la charge, tolère les pannes et s'auto-adapte tout en assurant l'atomicité. Nous spécifions la solution, la prouvons correcte et la simulons pour en analyser les performances

A Semantic Overlay for Self- Peer-to-Peer Publish/Subscribe

International audiencePublish/Subscribe systems provide a useful platform for delivering data (events) from publishers to subscribers in an anonymous fashion in distributed networks. In this pa-per, we promote a novel design principle for self-* dynamic and reliable content-based publish/subscribe systems and perform a comparative analysis of its probabilistic and de-terministic implementations. More specifically, we present a generic content-based publish/subscribe system, called DPS (Dynamic Publish/Subscribe). DPS combines classi-cal content-based filtering with self-* (self-organizing, self-configuring, and self-healing) subscription-driven cluster-ing of subscribers. DPS gracefully adapts to failures and changes in the system while achieving scalable events deliv-ery. DPS includes a variety of fault-tolerant deterministic and probabilistic content-based publication/subscription schemes. These schemes are targeted toward scalability, and aim at reducing and distributing the number of mes-sages exchanged. Reliability and scalability of our system are shown through analytical and experimental evaluation

SAM: Self* Atomic Memory for P2P Systems

We propose an implementation of self-adjusting and self-healing atomic memory in highly dynamic systems exploiting peer-to-peer (p2p) techniques. Our approach, named SAM, brings together new and old research areas such as p2p overlays, dynamic quorums and replica control. In SAM, nodes form a connected overlay. To emulate the behavior of an atomic memory we use intersected sets of nodes, namely quorums, where each node hosts a replica of an object. In our approach, a quorum set is obtained by performing a deterministic traversal of the overlay. The SAM overlay features self-* capabilities: that is, the overlay self-heals on the fly when nodes hosting replicas leave the system and the number of active replicas in the overlay dynamically self-adjusts function of the object load. In particular, SAM pushes requests from loaded replicas to less solicited replicas. If such replicas do not exist, the replicas overlay self-adjusts to absorb the extra load without breaking the atomicity. We propose a distributed implementation of SAM where nodes exploit only a restricted local view of the system, for the sake of scalability. We provide a complete specification of our system and prove that it implements object atomicity. / Ce rapport présente une mémoire atomique auto-ajustable et auto-réparante en systèmes hautement dynamiques. Nous proposons une implémentation de celle-ci basée sur l'utilisation de techniques égales-à-égales (p2p). Cette solution appelée SAM, rassemble des thématiques de recherches aussi bien anciennes que récentes telles que les couches de communication p2p, les quorums dynamiques et la réplication contrôlée. Les noeuds de SAM forment un sur-graphe connecté. Une copie de chaque objet est répliquée à différents noeuds, appelés réplicas. Afin d'assurer l'atomicité de ces objets, nous utilisons des quorums, ensembles intersectés de réplicas. Ces quorums sont obtenus via une traversée déterministe effectuée au sein du graphe de communication. De plus ce graphe possède des propriétés auto-* : Celui-ci s'auto-répare à la volée lorsque des réplicas quittent le système et le nombre de réplicas s'auto-ajuste en fonction de la charge. Plus particulièrement, SAM réparti automatiquement la charge en distribuant les requêtes effectuées sur des noeuds surchargés à d'autres noeuds. Si tous les noeuds sont surchargés alors le sur-graphe s'auto-ajuste pour absorber la charge induite en garantissant l'atomicité. Dans ce rapport nous proposons une implementation distribuée de SAM où chaque noeud ne possède qu'une connaissance locale du système, permettant ainsi son utilisation à grande échelle. Nous spécifions formellement cet algorithme et prouvons qu'il satisfait la propriété d'atomicité des objets

QoT-Driven Optical Control and Data Plane in Multi-Vendor Disaggregated Networks

A novel disaggregated network architecture with independent PCE and optical control based on GNPy is proposed and experimentally validated over a network including two independent OLSs for total 1400 km, ROADM whiteboxes and pluggable transceivers

Experimental Demonstration of Partially Disaggregated Optical Network Control Using the Physical Layer Digital Twin

Optical communications and networking are fast becoming the solution to support ever-increasing data traffic across all segments of the network, expanding from core/metro networks to 5G/6G front-hauling. Therefore, optical networks need to evolve towards an efficient exploitation of the infrastructure by overcoming the closed and aggregated paradigm, to enable apparatus sharing together with the slicing and separation of the optical data plane from the optical control. In addition to the advantages in terms of efficiency and cost reduction, this evolution will increase network reliability, also allowing for a fine trade-off between robustness and maximum capacity exploitation. In this work, an optical network architecture is presented based on the physical layer digital twin of the optical transport used within a multi-layer hierarchical control operated by an intent-based network operating system. An experimental proof of concept is performed on a three-node network including up to 1000 km optical transmission, open re-configurable optical add & drop multiplexers (ROADMs) and whitebox transponders hosting pluggable multirate transceivers. The proposed solution is based on GNPy as the optical physical layer digital twin and ONOS as intent-based network operating system. The reliability of the optical control decoupled by the data plane functioning is experimentally demonstrated exploiting GNPy as open lightpath computation engine and software optical amplifier models derived from the component characterization. Besides the lightpath deployment exploiting the modulation format evaluation given a generic traffic request, the architecture reliability is tested mimicking the use case of an automatic failure recovery from a fiber cut