# Recent Advances in Evolving Computing Paradigms: Cloud, Edge, and Fog Technologies
## 4 Challenges and Opportunities
### Fog Computing: Open Challenges
The diversified nature of edge devices has to be emphasized by the fog architecture at the device as well as the network levels. Utilizing heterogeneous devices in a diverse fog setting with varying application demands is strenuous. Numerous IoT devices from diverse hardware and software vendors add to the complexity factor. When the edge lacks computational resources, it can be acquired and assigned from among the fog nodes setting up a common pool of computing, network, and storage resources, availed by applications as per demand. The heterogeneity of fog devices and resources in the dynamic fog setting enables resource scheduling and allocation to be more challenging than that of the cloud, with utilizing idle resources being fog's top priority. * Security and privacy  
The heterogeneity of devices makes the fog framework vulnerable to various attacks due to its deployment in a not-so-secure setting. As fog nodes are positioned between the cloud and end-users, fog computing is susceptible to security issues. Assuring the privacy of sensitive data originating from sensors is critical. The fog-based Distributed Denial of Service (DDoS) attack is highly destructive, as diverse malignant devices overwhelm resource-limited end devices with fake service requests. Another such attack is the Man-in-the-Middle Attack (MMA), which discloses sensitive private data. The physical components of IoT devices can also be attacked, referred to as a physical attack based on the protection level and implemented location. * QoS  
The fog framework encompasses devices from the cloud to the edge, and the fog nodes are to provide end-to-end services adhering to users' service-specific QoS features. The fog system is entitled to manage the distribution of computing and storage to the cloud while orchestrating heterogeneous edge devices. Hence, it is necessary to dynamically integrate cloud servers and fog devices. * Blockchain and Software-Defined Networking (SDN)  
Figure 13: Fog computing—open challenges. In fog-based IoT settings, blockchain technology can provide a secure framework for controlling data and information exchanges amongst independently operating devices. To improve privacy and security, blockchain offers the safe transmission and storage of digitally signed documents. As a result, an additional study into this technology is critical in order to offer and improve methods for securely transmitting data between IoT devices, utilizing a trustworthy approach such as a time-stamped contractual handshake. Furthermore, Software Defined Networking (SDN) is a networking technology that may be used in conjunction with fog technology to enable effective data exchange and resource collaboration. SDN may also bring intelligence to fog-based IoT networks, among other things. SDN may also be utilized to protect fog-based IoT infrastructures. The authors, for example, developed a hybrid network design for smart cities that included SDN with blockchain. As a result, research into SDN and its integration with blockchain would be helpful in providing an efficient architecture for sustainable smart cities. Latency management Latency control is required in fog computing to guarantee an acceptable level of Quality of Service. As a result, research into various latency management techniques would aid in delivering services with the least amount of delay and ensuring a higher QoS throughout the system. The estimate of resources is another key topic in fog computing. It aids in allocating computing resources depending on various policies, allowing for the correct allocation of resources for future computation. In order to attain the necessary QoS, a comprehensive study into various resource estimate policies in terms of multiple aspects such as user attributes and experienced Quality of Experience (QoE) would be useful.