With the advent of Internet of Things (IoT) connecting billions of mobile and stationary devices to serve real-time applications, cloud computing paradigms face some significant challenges such as high latency and jitter, non-supportive location-awareness and mobility, and non-adaptive communication types. To address these challenges, edge computing paradigms, namely Fog Computing (FC), Mobile Edge Computing (MEC) and Cloudlet, have emerged to shift the digital services from centralized cloud computing to computing at edges. In this article, we analyze cloud and edge computing paradigms from features and pillars perspectives to identify the key motivators of the transitions from one type of virtualized computing paradigm to another one. We then focus on computing and network virtualization techniques as the essence of all these paradigms, and delineate why virtualization features, resource richness and application requirements are the primary factors for the selection of virtualization types in IoT frameworks. Based on these features, we compare the state-of-the-art research studies in the IoT domain. We finally investigate the deployment of virtualized computing and networking resources from performance perspective in an edge-cloud environment, followed by mapping of the existing work to the provided taxonomy for this research domain. The lessons from the reviewed are that the selection of virtualization technique, placement and migration of virtualized resources rely on the requirements of IoT services (i.e., latency, scalability, mobility, multi-tenancy, privacy, and security). As a result, there is a need for prioritizing the requirements, integrating different virtualization techniques, and exploiting a hierarchical edge-cloud architecture.

随着物联网（IoT）的出现，连接数十亿个移动和固定设备以服务于实时应用，云计算范例面临着一些重大挑战，例如高延迟和抖动，不支持位置的感知和移动性以及自适应通信类型。为了应对这些挑战，出现了边缘计算范例，即雾计算（FC），移动边缘计算（MEC）和Cloudlet，以将数字服务从集中式云计算转移到边缘计算。在本文中，我们从功能和支柱的角度分析了云计算和边缘计算范例，以确定从一种类型的虚拟化计算范例到另一种虚拟化计算范例的过渡的主要动力。然后，我们将重点放在计算和网络虚拟化技术上，这是所有这些范例的本质，虚拟化功能，资源丰富性和应用程序要求是在IoT框架中选择虚拟化类型的主要因素。基于这些功能，我们比较了IoT领域的最新研究。最后，我们从边缘云环境中的性能角度研究了虚拟化计算和网络资源的部署，然后将现有工作映射到该研究领域提供的分类法中。审查得出的教训是，虚拟化技术的选择，虚拟化资源的放置和迁移取决于IoT服务的要求（即，延迟，可伸缩性，移动性，多租户，隐私和安全性）。结果，需要优先考虑需求，集成不同的虚拟化技术以及利用分层边缘云架构。