A software pattern is a reusable solution to address a commonly occurring problem within a given context when designing software. Using patterns is a common practice for software architects to ensure software quality. Many pattern collections have been proposed for a large number of application domains. However, because of the technology's recentness, there are only a few available collections with a lack of extensive testing in industrial blockchain applications. It is also difficult for software architects to adequately apply blockchain patterns in their applications, as it requires deep knowledge of blockchain technology. Through a systematic literature review, this paper has identified 120 unique blockchain-related patterns and proposes a pattern taxonomy composed of multiple categories, built from the extracted pattern collection. The purpose of this collection is to map, classify, and describe all the available patterns across the literature to help readers make adequate decisions regarding blockchain pattern selection. This study also shows potential applications of those patterns and identifies the relationships between blockchain patterns and other non-blockchain software patterns.

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.

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.

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 connectivity, 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.