# Development of Intelligent Core Network for Tactile Internet and Future Smart Systems
## 3 System Structure
The final layer is the application layer, which defines the services and applications that are required by system operators. The three layers of the system are connected through the system management and orchestration interface. This interface is responsible for managing the operation of the first two layers based on the business application in the higher layer. The management and control tasks of the interface are performed through APIs. The management and orchestration interface is connected to the first layer through APIs to perform, the system configuration and monitoring of status and performance. Also, the software and parameters of the second layer can be fetched at any time by the managing interface through APIs. The link between the application layer and the management and orchestration interface allows the interface to perform network slicing for each application or map it to an existing slice [6]. In order to perform these critical and various tasks, the management and orchestration interface employs SDN/NFV technologies. SDN technology is one way that is used to overcome the problem of one millisecond round trip delay concerned with the Tactile Internet system and the future 5G cellular system. Moreover, SDN provides efficient solutions for achieving network flexibility and efficiency. The core network of cellular network will be based on SDN technology [32]. SDN works based on the separation of the data plane and the control plane. The two plans are linked through the OpenFlow interface protocol. Figure 4 illustrates the end-to-end structure of our proposed Tactile Internet system. The end-to-end system structure consists of user devices, RAN (eNBs), cloud units, access switches,  
Figure 3: Multi-level cloud layers for Tactile Internet system. OpenFlow switches, Middleboxes, and, finally, SDN controller. Each base station (eNB) is connected to the network through an access switch, which powerfully performs packet classification on traffic from user devices. The access switches is software switches such as Open vSwitch [33]. The whole network is connected through OpenFlow switches that manage data packets and forward traffic based on their flow tables. Middleboxes are commodity hardware that represents a way for the network operators to add extra functionalities, such as firewall and network address translation. The major requirements of the functions and services that are introduced by these Middleboxes are the efficient use of resources and the system protection from attacks. All of these elements represent the data plane of the network. The last part of the system is the central controller (SDNC), which represents the control plane of the network. By means of programming and control logic, SDNC can execute functions and operations in the control plane. SDNC maintains the global information of the edge and core network devices include; OpenFlow switches, access switches, Middleboxes, RAN, and cloud units. SDNC manages and controls the edge and core network devices mentioned through the OpenFlow protocol. Table 1 contains some of the existing controllers that can be used as an SDNC with the OpenFlow protocol. Functionally, switches that are used in the tactile system can be viewed as a packet forwarding devices with single or multiple flow tables [34]. Two types of switches are deployed in the OpenFlow based network, pure switches, and hybrid switches. Pure switches support only OpenFlow and fully depended on the SDNC. In the other side, hybrid switches, which are more commercial, have the ability to support OpenFlow with the traditional operations and protocols. OpenFlow protocol is the signaling standard used for the communication between SDNC and OpenFlow switches. In other words, the instructions from SDNC to other network devices are transferred through the OpenFlow protocol [35]. Each OpenFlow node communicates with the SDNC via a secured OpenFlow channel.