The heterogeneous, geographically distributed infrastructure of fog computing poses challenges in data replication, data distribution, and data mobility for fog applications. Fog computing is still missing the necessary abstractions to manage application data, and fog application developers need to re-implement data management for every new piece of software. Proposed solutions are limited to certain application domains, such as the IoT, are not flexible in regard to network topology, or do not provide the means for applications to control the movement of their data. In this paper, we present FReD, a data replication middleware for the fog. FReD serves as a building block for configurable fog data distribution and enables low-latency, high-bandwidth, and privacy-sensitive applications. FReD is a common data access interface across heterogeneous infrastructure and network topologies, provides transparent and controllable data distribution, and can be integrated with applications from different domains. To evaluate our approach, we present a prototype implementation of FReD and show the benefits of developing with FReD using three case studies of fog computing applications.

翻译：雾计算异构、地理分布的基础设施给雾应用的数据复制、数据分发及数据迁移带来了挑战。目前雾计算仍缺乏管理应用数据的必要抽象机制，应用开发者需为每个新软件重新实现数据管理功能。现有解决方案局限于特定应用领域（如物联网），在网络拓扑方面缺乏灵活性，或未提供应用控制其数据移动的手段。本文提出FReD——面向雾计算的数据复制中间件。FReD作为可配置的雾数据分发基础组件，支持低延迟、高带宽及隐私敏感型应用。该中间件能在异构基础设施与网络拓扑间提供统一数据访问接口，实现透明可控的数据分发，并可集成不同领域的应用。为评估方案有效性，我们实现了FReD原型系统，并通过三个雾计算应用案例研究展示了基于FReD开发的显著优势。