## 4 What Is NFV?
### Challenges and Solutions
#### 4.4.1 Core: Challenges and Solutions  
Incorporating NFV into the core of cellular networks introduces new attack surfaces and security vulnerabilities, and these are because of the resource pool based on cloud computing and open network architecture. This can impact the functionality of NFVs [97]. These vulnerabilities can be handled by developing robust security measures such as encryption, authentication, access control, and Intrusion Detection Systems (IDSs) to safeguard NFV infrastructure and VNFs. Regular security audits and updates are also crucial to avoid possible risks [98].  
The virtualization overhead and resource-sharing in NFV infrastructure may cause performance degradation, affecting QoS and Quality-of-Experience (QoE) [97]. By leveraging performance optimization techniques such as selecting the specialized hardware components to upgrade the performance of specific computational tasks, and developing network function offloading mechanisms, the virtualization overhead could be reduced. In addition, optimal performance for critical network functions could be maintained by fine-tuning resource allocation and scheduling algorithms [99].  
NFV implies the integration of diverse hardware and software components from multiple vendors, leading to compatibility challenges and interoperability issues. Along with this, dependency on specific NFV hardware vendors or proprietary solutions may result in vendor lock-in, limiting flexibility and hampering innovation. The following measures could be taken: Set up standardized interfaces and protocols for deploying the NFV to enhance the interoperability between different hardware components from different vendors [97]. Vendor lock-in risks could be tackled by embracing open standards and interoperable solutions. Promote vendor neutrality and flexibility by collaborating with multiple vendors and leveraging open-source NFV initiatives such as OpenStack [100] and OPNFV [101]. Ensure NFV ecosystem compatibility by participating in industry forums and consortia.  
Rapid network expansion or sudden traffic fluctuations may affect the scalability. The scalability could be managed by adapting resource allocation automatically based on  
Figure 11: Power consumption in traditional and virtualized functions. Virtualized functions consume approximately 50% less power compared to traditional network functions [96].  
workload demands and network conditions by implementing dynamic resource orchestration and scaling mechanisms [102]. Using cloud-native architectures and containerization technology, NFV deployments can be made more agile and scalable [103]. To ensure the successful deployment and operation of virtualized cellular networks, operators must address these challenges and implement appropriate solutions.  
In an NFV network environment, it is crucial to have the same level of reliability and availability of network services as in a traditional network environment. Figure 12 shows the mechanism to support the reliability and availability of an NFV-based network. This is achieved through fault prevention, which includes strategies to avoid errors and operational failures; fault detection, which involves identifying and diagnosing failures; and resiliency, which ensures service recovery after a failure through redundancy, migration, and protection of VNFs [104].