# ML-Based 5G Network Slicing Security:
## 3 Network Slicing and Its Paradigms  
Network slicing is one of the key features of the 5G mobile network, which boosts the performance of complete architecture. 5G differs from 1G to 4G mobile networks; it offers various other services with mobile broadband services such as mMTC and URLLC. To offer multiple heterogeneous services from a single platform which is flexible in nature, the flexibility is provided by a network slicing mechanism in which one physical network is divided into multiple logical networks to offer these services simultaneously. Each network slice creation is done in four phases: softwarization, virtualization, orchestration, and management. These slices use generic resources to serve users and specific applications. SDN and NFV play a significant role in slicing to make the 5G network more scalable  
Figure 2: Evolution of network slicing: A timeline.  
and reliable. Network slicing deals with three prominent use cases: the first enhances mobile broadband (eMBB) for those applications which require high bandwidth to offer Ultra-HD video communication. This use case increases the traffic load on mobile networks. The second massive machine type communication (mMTC) offers connectivity between millions of devices. This use case does not increase traffic but increases the magnitude of mobile networks. The last service is ultra-reliable low latency communication (URLLC) which applies to connectivity, remote surgery, industry 4.0, etc. in vehicles to everything (V2X). This use case needs very low latency connectivity [16].  
The network slicing architectural framework is based on three categories, as mentioned in Figure 3.  
* Radio Access Network (RAN) slicing: In the 4G network, one extra en-gNB master node is added to benefit the cloudification in the 5G network. The next-generation RAN is dynamic and scalable, adding or releasing the requirement's network functions. It also balances the load over the slice and manages the resources over the slice [47]. Implementation of RAN in network slicing can be done through logical abstraction of physical resources such as base stations (master eNB and secondary en-gNB) packet data network gateway (PDN-GW), home subscriber server (HSS), serving gateway (S-GW), mobility management entity (MME) [48].
* Core Network (CN) slicing: The 4G network works on centralized architecture without a fully isolated control and data plane. The problems with such centralized architectures are its single point of failure and traffic congestion, etc. The core slicing developed in 3 GPP isolates the control and data plane, effectively supporting mobile broadband services and massive and mission-critical IoT services. The core network architecture includes the following network functions: access and mobility management functions, authentication server functions, unified data management functions, data storage functions, session management functions, user equipment, user data plane functions, policy control functions, and RAN [49].  
Network slicing involves three layers: As shown in Figure 4.  
* The Service Instance layer offers the services to the end-user or subscriber based on their request. Each service in the service instance layer is represented as an 'instance'.
* The Network Slice Instance layer includes the network slices, which are customized with all the network features and are provided to the service instance.
* The Resource layer is a pool of all the virtual and physical resources which are required by the network slices to serve the services of the service instance.  
Figure 3: 5G network slicing architectural framework.