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Designing blockchain-based applications is a tedious task. Compared to traditional software engineering, software architects cannot rely on previous experiences or proven practices, often formalized as software patterns. Also, the selection of an adequate blockchain technology is difficult without deep knowledge of the technology. This paper introduces Harmonica, a framework for the design and implementation of a blockchain-based application. This framework is divided in three parts: a decision-making engine to recommend a blockchain technology and blockchain-based software patterns relying on requirements, a configurator to generate code stubs and configuration files, and a knowledge base to support those tools.

International audience; With the popularity of software defined networking architectures, the growing complexity of its use cases dictates the need for better auditability especially for security. In this paper, we aim at facilitating high-level management-plane policy configuration conformance auditing and their reflection in the data plane, to detect missing or spurious flow rules with respect to security policies. To this end, we propose an efficient conformance checking approach based on an intentional northbound interface as well as traces of management, control and data plane. Leveraging a proof-of-concept implementation of our approach, we compare its conformance-checking runtime and precision against a direct method on virtual topologies and find that it significantly improves scalability. We conclude by proposing directions for further enhancements extending the techniques presented herein.

International audience; Blockchain has been praised for its capacity to hold data in a decentralized and tamper-proof way. It also supports the execution of code through blockchain’s smart contracts, adding automation of actions to the network with high trustability. However, as smart contracts are visible by anybody on the network, the business data and logic may be at risk, thus companies could be reluctant to use such technology. This paper aims to propose a pattern that allows the execution of automatable legal contract clauses, where its execution states are stored in an on-chain smart-contract and the logic needed to enforce it wraps it off-chain. An engine completes this pattern by running a business process that corresponds to the legal contract. We then propose a pattern-based solution based on a real-life use case: transportation of refrigerated goods. We argue that this pattern guarantees companies pseudonymity and data confidentiality while ensuring that an audit trail can be reconstituted through the blockchain smart-contract to identify misbehavior or errors. This paper paves the way for a future possible implementation of the solution described, as well as its evaluation.

International audience; Companies trying to build new solutions using blockchain are confronted with a plethora of available concurrent technologies that have many control knobs which require fine-tuning by experts. Exiting studies that build decision models for blockchain adoption or selection lack an automated way to use non-functional requirements to provide recommendations. This article, extended from previous works, introduces BLADE (BLockchain Automated DEcision Engine), a decision support tool for blockchain to better take into account high level requirements and preferences for recommendations. From documentations, white papers and academic papers, a knowledge base of blockchain solutions is constructed. This allows BLADE to execute an automated multi-criteria decision process giving the most relevant solution based on requirements and preferences, extracted from the ISO 25010 software quality standard. An implementation of this tool is performed within a web platform allowing the easy capture of user requirements and preferences for recommendation. Finally, the proposed approach is validated on a supply chain management case study. This study is a first step in order to design a solution allowing the design and implementation of end-to-end blockchain applications. While still limited in scope, BLADE will include more blockchain alternatives and more flexible requirements inputs in future work.; Les entreprises souhaitant déployer des solutions basées sur la blockchain sont confrontées à une pléthore de technologies concurrentes ayant chacun un grand nombre de paramètres propres devant être ajustés par un expert. Les études existantes proposant des modèles de décision pour blockchain ne proposent pas de solution pour le choix des paramètres assurant la mise en oeuvre automatique des exigences non-fonctionnelles. Cet article, version étendue de précédents travaux, présente BLADE (BLockchain Automated DEcision Engine), un outil d'aide à la décision pour blockchain permettant de mieux prendre en compte les exigences de haut niveau et préférences. Tout d'abord, une base de connaissances de solutions blockchain est construite à partir de documentations, de livres blancs et de travaux de recherche académiques. Celle-ci permet à BLADE d'exécuter un processus de décision multicritère automatisé donnant la solution la plus pertinente à partir d'exigences et préférences, extraites de la norme de qualité logicielle ISO 25010. L'implémentation de cet outil est ensuite réalisée au sein d'une plateforme web permettant la saisie aisée des exigences et des préférences de l'utilisateur. Enfin, l'approche proposée est validée grâce à un cas d'étude de gestion de chaîne logistique. Cette étude est une première étape afin de concevoir une solution permettant la conception et l'implémentation d'applications blockchain de bout-en-bout.

Today, over-the-top video streaming is gaining a lot of popularity. In this respect, the virtual content delivery network (CDN) is perceived as a key enabler to circumvent the technical challenges faced by content providers to deliver high-quality content over the Internet. Here, the authors investigate how the two main actors of the video delivery chain--the CDN operator and the ISP--can benefit from network and server virtualization to negotiate dynamic service-level agreements that reduce CDN capital expenditures and operating expenses, while generating more revenue for the ISP. First, the authors present a dataset used to simulate dynamic distributed traffic consumption. Second, they discuss the steps required to deploy and operate a virtual CDN deployed on an ISP's network. Furthermore, they present evaluation results of the proposed solution, based on simple models. Lastly, they elaborate on operational parameters that are used to further optimize the solution. This article is part of a special issue on advancing multimedia distribution.

With advent of 5G, the classical mobile network business model is shifting from a network-operator-oriented business to a more open system with several actors. In this context, the Network Slice provider will play the role of an intermediate entity between the vertical service provider and the resource provider. To deploy a network slice, the network slice provider will require a brokering mechanism, which allows it to lease resources from different providers in a secure and private way. In this paper we propose a broker design based on Blockchain technology, providing a mechanism that secures and ensures anonymous transactions. This work was partially funded by the European Union’s Horizon 2020 research and innovation program under the 5G-Transformer project (grant no. 761536). Dr. Ksentini is corresponding author.

International audience; Increasing over-the-top video consumption endangers the sustainability of content delivery over the Internet. Internet Service Providers (ISP) face difficulties in competing on value-added services with content providers and Content Delivery Network (CDN) operators. In this respect, we propose a new model for the collaboration between content delivery stakeholders, so that CDN operators can deploy their software in ISP infrastructures leveraging on Network Function Virtualization (NFV). As the ISP network topology and utilization is deemed confidential, we use a high-level Service Level Agreement (SLA) for the negotiation of both computing resources and connectiv-ity, allowing the ISP to optimize server selection, while providing at the same time sufficient flexibility to the CDN operators for content delivery. Furthermore, we present a linear programming formulation for the VNF Service Chain Embedding and an heuristic to increase problem tractability with a small cost overhead. Finally , we validate the efficiency of the proposed service chain model for virtual CDN management.

The switch in video delivery from traditional medium to Over-The-Top (OTT) based services has been a game changer for stakeholders of the media delivery ecosystem. It has changed the value chain enabling Content Delivery Networks and Content Providers to take the lion's share at the expense of Internet/Network Service Providers. Even if establishing collaboration between them naturally appears as the key to provide good Quality of Service to the end-users, they struggle in finding efficient and fair ways to do so. This paper directly tackles this problem and proposes a new model for content delivery actors to collaborate over a Virtualized Infrastructure, fairly balancing the revenue stream created. We list the main challenges and the new technical opportunities to solve them, among which the deployment of a distributed Network Function Virtualization (NFV) platform at the edge of the Internet Service Provider's network where a virtual Content Delivery Network (vCDN) is proposed to be deployed. Furthermore, we apply a game-theoretic analysis to study different ISP-CDN collaboration models and identify optimality conditions for our proposed CDN-as-a-Virtual-Network-Function approach.

International audience; Increasing over-the-top video consumption makes the delivery of content unsustainable in the current Internet. The Internet Service Providers (ISP) have a hard time competing on value-added services with content providers and content delivery networks (CDN). We propose a new model of collaboration between content delivery actors where CDNs can deploy their software in Internet Service Providers' infrastruc-tures as NFV modules. As the ISP network state has to be kept private, a high-level SLA is used to negotiate both computing resources and connectivity, leaving it up to the ISP to optimize server placement and routes. The contribution of this paper is to formalize this problem as a Service Function Chaining Embedding problem, and to propose an algorithm to optimize the Service Function Chain to improve embedding probability and decrease consumed bandwidth in the process.

International audience; Background: This paper belongs to the series of research documents describing the progress in the specification and development of the T-NOVA framework offering a marketplace for virtual network functions. T-NOVA is an international research project co-funded by the European Commission.Objective: Although, the idea of having a marketplace enabling buying, composing, and deploying “virtual” services on the fly is promising, its implementation or prototyping remains far from realization. This is mainly due to the limitations in the existing cloud computing platforms on top of which the services should be built.Method: In this paper, we discuss the T-NOVA approach and in particular some of the Virtual Network Functions (VNFs) that have been developed in this context. Special attention is paid to the design and specification of the VNFs as well as the related technical challenges that were faced when deployed within the marketplace.Results: Real-world considerations for handling VNF Lifecycles, Monitoring and Networking have also been discussed. We have highlighted two examples of Service Chaining where several VNFs are combined through the T-NOVA Marketplace to create added-value services. Some experiments and test results are also provided.Conclusion: In this paper, we have provided an overview on the T-NOVA Platform with a special focus on the deployment and performances of a wide variety of Virtual Network Functions implemented during the project. It is expected that the challenges and opportunities described in this paper will help foster innovation around NFV and will help pave the way for practitioners and researchers alike to further extend the use of Network Function virtualization in the future.

Objective To determine the possibility of obtaining good pregnancy rates (PRs) after freezing and thawing cocultured blastocysts. Design Human blastocysts were frozen first according to a protocol available from literature. Two other protocols including the addition of glycerol were designed to improve the results. Setting All the patients were under clinical management at the Institut Rhonalpin pour l'Etude de la Reproduction Humaine in Lyons, France. Patients Patients involved in the in vitro fertilization program have had their supernumerary embryos frozen according to the three protocols presented here. Main Outcome Measures Embryo recovery after freezing and thawing. Clinical and ongoing pregnancies after embryo transfer (ET). Results A protocol including sucrose addition and reduction of steps in the preparation of the blastocysts for freezing gave us a 21% PR per transfer (15 ongoing) of 101 transfers (106 thawings). Conclusions Freezing of cocultured human blastocysts allow good PRs. This can represent an alternative for repeated failures of ETs at early stages.

Preliminary results are presented concerning the first clinical application of cocultures of human embryos. In the experimental group, the embryos were cultured and transferred on day 5 post-insemination. Blastocyst formation was not dependent upon the stimulation regimen. Long term or ultrashort stimulation of the ovaries after gonadotrophin releasing hormone analogue gave 55-60% blastocyst formation. Serum was not necessary to obtain blastocysts. When the embryos were cocultured, we observed an increase in the implantation rates per embryo in the pregnant patients. However, a real increase in the pregnancy rate per transfer was observed in a population of patients who had had repeated failures of embryo transfer. This observation is discussed as possibly bypassing an effect of uterine motility, but the overall beneficial effect has to be assessed in a double blind randomized study. It is probable that improvements will not be observed for all the indications for in vitro fertilization.