# An Overview of Fog Computing and Edge Computing Security and Privacy Issues
## 2 Fog Computing Overview  
Unlike traditional cloud computing, fog computing--also known as fogging--focuses more on decentralization of the computer structure, located in between the devices that produces the actual data and the cloud. In fog computing the focus is on lowering the cloud computation capability to the edge of the network to be able to provide faster services to the users including communication service and software services. This comes handy in providing cloud solutions for high mobility technologies such as Internet of things (IoT) and vehicular ad hoc networks (VANET). Rather than having the devices connect through complex network infrastructure in fog computing the devices are normally connected directly to their destination. As a result, the connection will have much lower latency and better quality of service. The concept of fog computing was proposed by Cisco Systems. Fog computing system was not introduced to replace cloud computing, rather it was introduced to fill the services gaps of cloud computing [9; 10]. According to Cisco Systems, fog computing is a virtual platform that offers computation, storage and networking services to end devices from cloud computing data centers which are not specifically located at the network edge. Fog is different from cloud in a way that it has got end users closer to it as compared to cloud, to provide them services and respond to their demands in less amount of time. In cloud computing, computing, control and storage data are transported to the centralized cloud, whereas in fog computing, central and local computing, storage, and network management is balanced [11]. According to [12], fog computing is defined as a distributed computing technology where maximum operations are performed by virtualized and non-virtualized edge devices. It has some similar characteristics with cloud including non-latency aware processing and ability to store useful data for a longer time period by existing between the users and the cloud. The basic architecture of fog computing is similar to cloud computing, but its lower layers contain special components that are able to detect rare time response efficiently. Due to this feature, fog computing is used to control and improve health care department, traffic pattern, parking system and much more. Fog computing consists of disseminated framework consisting of a keen gadget that has certain application services outside the system. In other words, it gives authority to the gadgets to handle their associations and tasks any way they prefer best. Basically, fog computing is a focal layer residing between the cloud and the equipment, possessing enhanced information handling, investigation and capacity, which is achieved by reducing the amount of information to be transferred to the cloud [13]. Fog computing provides an improved administration and smooth client experience. It is basically a combination of hardware and software systems which has the power to monitor, control, and analyze data with extremely low latency [14]. In addition, Fog computing does not provide a permanent storage. It reduces the load on cloud by deleting unnecessary data into its computational storage, which also minimizes  
Figure 1: Cloud services level compression. the cost. Fog devices are slightly different from the cloud devices in terms of their position and application for which they are installed. Some of the differentiating factors include:  
* If the deployment purpose of the device is customization of the end network services or sensing some data then the device is categorized as a fog device, otherwise it is a cloud device. * If the device has limited computational capability and sensing ability, then it is classified as fog device. Some of the features of fog computing include:  
* Awareness regarding the location of edge. * Very low latency. * Mobility support. * Real-time services. * Good interactions. * Heterogeneous nature. * Inseparability.