**4.3 Large number of fog nodes**

Fog computing supports a very large number of IoT devices with cloud paradigms. Due to the large number of IoT devices that are widely distributed, FC has a large number of FNs to support these IoT devices. Fog nodes, sometimes called fog servers, include servers, routers, gateways, and IoT devices with routing, storage, and computing capabilities.

### **4.4 Support for mobility**

It is essential for many Fog applications to communicate directly with mobile devices and therefore support mobility techniques since a good percentage of the devices on the edge of the network are not stationary, for example, wearables, drones, and self-driven cars. FC must have robust mobile support capability for efficient edge computing. Mobile devices, like automobiles and drones, always change location quickly and depend on FN's critical services for operational efficiency and decisionmaking. This will depend on the capability of the fog network to offer these services without a drop in the quality of services rendered as these devices move from one location to another [33].

## **4.5 Real-time interactions**

An important feature of FC design is the need for real-time support for edge devices. FC is designed to greatly reduce the latency in communication between IoT and the cloud [34]. Fog applications involve real-time interactions rather than batch processing. Fog computing enables real-time interactions between end devices and fog nodes by ensuring it operates at the lowest possible latency. The real-time feature of the fog supports gaming, healthcare, automotive, aviation, streaming, and security systems.

#### **4.6 Heterogeneity**

IoT comprises different devices, including Fog nodes deployed in various environments from different vendors and technologies. Fog Computing, as a platform of high virtualization, yields computation, storage, and networking services, bridging the gap between edge devices and the cloud. While standardization has not been achieved across various FC computing paradigms like deployment methods, orchestration strategies, and equipment designs, there is beginning to be convergence between enterprises of similar interests [31]. Fog computing must continue to grow in accommodating heterogeneous vendors for equipment and application. It is also necessary to have communication protocols that will assist in interoperability.
