## 2 Architectures of 5G and 6G Networks
These findings collectively highlight that, while SDN enables centralized policy enforcement and rapid reconfiguration, its inherent vulnerabilities--such as susceptibility to controller attacks, scalability constraints, and reliance on secure communication channels--must be systematically addressed to ensure resilient and secure network deployments. * **Network Function Virtualization (NFV):** Network Function Virtualization departs from the legacy model of deploying network services on vendor-specific, specialized hardware (e.g., physical firewalls, load balancers). Instead, NFV allows service providers to instantiate Virtual Network Functions (VNFs) on commodity hardware, thereby lowering capital and operational expenses while boosting service innovation [13]. Common VNFs can include virtual firewalls (vFWs), virtual intrusion detection systems (vIDSs), virtual evolved packet cores (vEPCs), and other middleboxes that are crucial to mobile network operations. Despite these advantages, NFV presents new security challenges. Malicious actors can exploit hypervisor-level vulnerabilities to escape virtual machine boundaries-- commonly referred to as \"VM escape\" attacks--thus compromising co-resident VNFs on the same physical host. Additionally, misconfigurations in network slicing and resource allocation can cause inter-tenant interference, enabling attackers to eavesdrop on or disrupt neighboring slices [14]. These challenges necessitate rigorous isolation mechanisms, secure VNF lifecycle management, and automated detection of anomalous VNF behaviors using ML techniques. A recent large-scale NFV deployment in a European telecom operator's 5G infrastructure showed that flexible resource allocation helped meet diverse Quality of Service demands for enterprise and consumer applications [15]. Nevertheless, continuous scanning detected hypervisor-level vulnerabilities that could have been exploited to intercept VNF traffic. As a response, the operator integrated a dynamic VNF placement algorithm combined with real-time anomaly detection, effectively segregating critical virtual functions from non-critical ones and reducing the potential attack surface. Therefore, NFV reduces hardware dependencies, simplifies network updates, and enables rapid deployment of virtual security tools. However, it introduces security risks such as hypervisor vulnerabilities, VM escape attacks, and threats from shared infrastructure. Its complexity demands strong isolation and continuous monitoring to prevent misconfigurations and inter-tenant breaches. * **Edge Computing:** Edge computing (often referred to as multi-access edge computing, MEC) pushes computational and storage resources toward the network edge to minimize latency and optimize bandwidth usage [16]. Rather than routing all data to centralized data centers, edge nodes--installed in base stations, local data centers, or on-premise facilities--process large volumes of data closer to end users. This architectural shift is particularly beneficial for latency-sensitive use cases such as virtual/augmented reality, autonomous driving, and mission-critical IoT operations. However, with resources distributed across numerous, geographically dispersed nodes, attackers gain multiple entry points to the broader network. These edge sites often have fewer on-site security measures compared to large central data centers [17]. A compromised edge node could, in the worst case, enable lateral movement into the core network or facilitate the injection of false data into aggregated analytics streams. Securing edge infrastructures thus requires advanced intrusion detection and prevention strategies tailored especially for resource-constrained environments, along with strong encryption, robust access controls, and trusted hardware attestation to verify the integrity of edge devices. A 2021 pilot project in a smart city environment illustrating the advantages and vulnerabilities of edge computing in 5G was presented in [18].