Clarifying Fog Computing and Networking: 10 Questions and Answers

Clarifying Fog Computing and Networking: 10 Questions and Answers By Mung Chiang, Sangtae Ha, Chih-Lin I, Fulvio Risso, and Tao Zhang 1. What Is Fog Computing and How Is It Different from Edge Computing? Fog computing is an end-to-end horizontal architecture that distributes computing, storage, control, and networking functions closer to users along the cloud-to-thing continuum. The word “edge” may carry different meanings. A common usage of the term refers to the edge network as opposed to the core network, with equipment such as edge routers, base stations, and home gateways. In that sense, there are several differences between fog and edge. First, fog is inclusive of cloud, core, metro, edge, clients, and things. The fog architecture will further enable pooling, orchestrating, managing, and securing the resources and functions distributed in the cloud, anywhere along the cloud-to-thing continuum, and on the things to support end-to end services and applications. Second, fog seeks to realize a seamless continuum of computing services from the cloud to the things rather than treating the network edges as isolated computing platforms. Third, fog envisions a horizontal platform that will support the common fog computing functions for multiple industries and application domains, including but not limited to traditional telco services. Fourth, a dominant part of edge is mobile edge, whereas the fog computing architecture will be flexible enough to work over wireline as well as wireless networks. 2. Is Fog Just a Smaller Cloud? First, the size of the fog is flexible — it can range from a single small fog node to large fog systems comparable to existing clouds, depending on the application needs. While fog will bring many cloud-like services closer to end users and can have smaller footprints than the cloud, it has a different vision from that of smaller or mini clouds. Mini-clouds tend to be designed as isolated computing platforms. Fog envisions a seamlessly integrated cloud-fog-thing architecture to enable computing anywhere along the cloud-to-things continuum. Fog-to-cloud and fog-to-fog interactions will therefore be a focus of an end-to-end fog computing architecture to distribute computing functions, and then manage, pool, orchestrate, and secure the distributed resources and functions. Fog may form a hierarchical architecture between the cloud and the things, with fog nodes at different architectural levels collaborating with each other to support end-to-end applications. Fog also concerns the control of cyber-physical systems and D2D communication, in addition to computation and storage in clouds, big or small. 3. Is Fog Equivalent to IoT? Fog is an architecture. The Internet of Things (IoT) often refers to a set of services and applications. An architecture decides the allocation of functionalities. It formulates and answers questions such as “who does what, and at what timescale and location?” An architecture supports many applications, some in existence today and others more futuristic. For example, TCP/IP represents an Internet architecture. It includes several key principles, such as addressing, and allocation of functionalities, such as congestion-independent, hop-by hop routing, and congestion-dependent, end-to-end session control. Applications that leverage TCP/IP have come from a wide and increasing range: from the web to emails and from P2P to video streaming. The relationship between fog and IoT is similar to that between the Internet architecture and the web applications. Fog also supports other areas of applications, such as those in fifth generation (5G) cellular or embedded artificial intelligence. 4. Is Fog for Computation, or Communication, or Control? Fog is an umbrella term that includes an architecture for computation, an architecture for communication, an architecture for storage, and an architecture for control (both control of the network itself and networked control in cyber-physical systems). For example, fog computing explores new ways to decompose a computational task so as to match an underlying computation substrate that is heterogeneous (in hardware and software capabilities), volatile (in availability, mobility, and security), and constrained (by bandwidth or battery). Fog communication explores how devices may talk to each other despite intermittent global connectivity. Fog control explores how clients might crowd-sense network conditions and self-configure, and how to leverage small and almost deterministic latency to enable feedback control loops. 5. What Are the Unique Advantages Offered by Fog? Unique advantages that are potentially offered by fog can be summarized with an acronym: “SCALE.” These advantages in turn enable new services and business models, and may help broaden revenues, reduce cost, or accelerate product rollouts. Security: While fog faces unique security challenges, it also offers certain advantages. In particular, by reducing the distance that information ne