Fog computing arises as a complement to cloud computing where computing and storage are provided in a decentralized way rather than the centralized approach of the cloud paradigm. In addition, blockchain provides a decentralized and immutable ledger which can provide support for running arbitrary logic thanks to smart contracts. These facts can lead to harness smart contracts on blockchain as the basis for a decentralized, autonomous, and resilient orchestrator for the resources in the fog. However, the potentially vast amount of geographically distributed fog nodes may threaten the feasibility of the orchestration. On the other hand, fog nodes can exhibit highly dynamic workloads which may result in the orchestrator redistributing the services among them. Thus, there is also a need to dynamically support the network connections to those services independently of their location. Software Defined Networking (SDN) can be integrated within the orchestrator to carry out a seamless service management. To tackle both aforementioned issues, the S-HIDRA architecture is proposed. It integrates SDN support within a blockchain-based orchestrator of container-based services for fog environments, in order to provide low network latency and high service availability. Also, a domain-based architecture is outlined \marev{as potential scenario} to address the geographic distributed nature of fog environments. Results obtained from a proof-of-concept implementation assess the required functionality for S-HIDRA.

翻译：雾计算作为云计算的补充方案应运而生，其通过去中心化方式而非云范式的集中式模式提供计算与存储能力。同时，区块链提供了去中心化且不可篡改的分布式账本，借助智能合约可支持运行任意逻辑。这些特性使得利用区块链上的智能合约构建去中心化、自主且具有弹性的雾资源编排器成为可能。然而，雾节点潜在的庞大规模与地理分布特性可能威胁编排的可行性。另一方面，雾节点可能呈现高度动态的工作负载，导致编排器需要在节点间重新分配服务。因此，还需要动态支持这些服务的网络连接，且不受其位置限制。软件定义网络（SDN）可集成至编排器中实现无缝服务管理。为应对上述两大挑战，本文提出了S-HIDRA架构。该架构将SDN支持集成至基于区块链的容器化服务编排器中，为雾环境提供低网络延迟和高服务可用性。同时，针对雾环境的地理分布特性，本文描绘了一种基于域的架构作为潜在应用场景。概念验证实现的评估结果验证了S-HIDRA所需的功能性。