# Network Slicing for mMTC and URLLC Using Software-Defined Networking with P4 Switches
## 1 Introduction  
Numerous studies have investigated next-generation mobile communication network technologies, such as network architectures, communication protocols, information security and smart applications [1, 2]. The performance of Internet of Things (IoT), in which connected devices transfer sensor data over the internet, is a key consideration in the development of fifth-generation (5G) networks. At the dawn of the era of 5G communication networks in 2020, the number of connected IoT devices had already reached 50 billion; each person had an average of 10.3 connected devices (Figure 1). By 2030, the number of IoT device nodes is expected to grow to 80 billion, and each person is expected to have an average of 20.5 connected devices [2]. The International Telecommunication Union Radio-communication Sector divided 5G communication services into three categories: mMTC (massive machine-type communication), URLLC (ultra-reliable low-latency communication) and eMBB (enhanced mobile broadband) [3, 4]. Figure 2 displays the nine service quality requirements, such as latency, and the corresponding importance of these requirements for each of the three categories, as indicated by the length of the radial bars [5]. mMTC and URLLC have two extremely different service quality requirements of scalability and reliability with low latency, respectively. Fifth generation and future communication networks should be able to integrate  
block is a multi-layer architecture comprising the service layer, network function layer, and infrastructure layer. The right control block is a centrally processed network unit, called the network slice controller, which monitors and manages the functions between any two of the three layers in the left block so as to efficiently coordinate the multiple coexisting network slices [5; 9]. SDN is a promising technology for network softwarization for realizing 5G NS. Potential network slices can be defined in accordance with the relevant requirements of each SDN user. SDN can include artificial intelligence algorithms and provide flexible and programmable applications or services [10; 11]. The Open Network Foundation [12] defined SDN as 'The physical separation of the network control plane from the forwarding plane, and where a control plane controls several devices.' This separation of the control plane from the data plane enables SDN to flexibly and centrally control the entire network and to quickly respond to changes in network conditions, business, markets, and user demands. The major difference between contemporary network operations and SDN is the creation of a virtualized control plane that can execute intelligent management decisions for network functions, remediating the gap between service delivery and network management (Figure 4) [13]. With an SDN, network control can be achieved directly and programmatically through a standardized southbound interface. For instance, the commonly used OpenFlow protocol [14] defines a communication mechanism between the controller in the control plane and the forwarding components in the data plane. Figure 4: Contemporary network and SDN. Figure 3: The 5G NS architecture. The state information of all packets in the network relies on the actions of the controller rather than those of the OpenFlow switches in the data plane, substantially increasing the burden on the SDN controller [15]. The processing delay between the SDN controller and switches and the control channel bottleneck [16; 17] may reduce the scalability, reliability, and security of 5G NS. Several advanced interface protocols for the SDN controller and switches have been proposed to provide enhanced state forwarding rules and enable data plane switches to obtain persistent state information, such as OpenState [18], programming protocol-independent packet processors (P4) [19], protocol-oblivious forwarding [20], stateful data plane architecture [21], and stateful network-wide abstractions for packet processing [22].