## 4 Experimental Results
### Creating the Fault-Tolerant SDN in CAs Environment  
Considering the above, it is possible to formulate requirements for a fault-tolerant SDN control loop, which includes three main levels:  
1. The transmission level control loop;
2. Infrastructure for monitoring and managing OpenFlow;
3. Inter controller communication infrastructure. The complexity of the functioning of this circuit lies in the formation of conditions for initiating SDN recovery processes when various CAs are implemented by an attacker. To increase the SDN resilience in CAs environment, a protection system is needed (Figure 25), which is based on a network recovery algorithm that distinguishes two levels:  
Figure 23: Dependence of the SDN resilience probability on the CA implementation time for Structure 2. Figure 22: Dependence of the SDN resilience probability on the CA implementation time for Structure 1.  
the transmission level; the management level. The main components of the proposed protection system are a database of SDN configurations and decision blocks built using a neural network. When they are conducting a CA, an attacker performs a series of sequential actions, upon detection of which the protection system should signal to the network administrator, and also recommend the use of a counteraction scenario. At the same time, the characteristics of the CA for the SDN levels will be different. For example, the \"Hacking/Crashing of the controller\" attack aimed at a soft switch will be characterized by an increase in traffic passing through the controller, an increase in the delay or no response from the controller, and, accordingly, for the controller, an increase in the processor load, the number of requests and so on. In this case, it is obvious that the conditions for the response of software switches and controllers should be divided into CA features. To create the SDN resilient system in a CAs environment, a client-server structure has been developed, which consists of agents operating on software routers and a server operating on a controller (Figure 26). The OvS Agent runs on the software router, and the server of the failover system is deployed on the controller, which interact via the OpenFlow protocol. Figure 26: Generalized structure of the system for ensuring resilience of the SDN segment. Figure 25: A variant of creating the SDN protection system in the CA conditions. The OvS agent (Figure 27) is a complete SDN anomaly analyzer based on the LSTM neural network for software routers. At the same time, having determined the most probable attack scenario, the OvS Agent offers the option for the network administrator to launch a countermeasure (recovery) scenario. Further, after the decision has been made, the selected scenario is executed by the official. The procedure is loaded from the configuration database, automatic settings are made and a connection to the backup controller is made when the complete reconfiguration mode is selected. The server of the failover system is launched in two versions: server-master and server-slave versions. For their joint work, a synchronization service is implemented, which is responsible for switching controllers among themselves, as well as mirroring service information necessary for making decisions in a recovery scenario. To determine the CA, as well as in the OvS Agent, an LSTM network is used, the training data set for which will differ from that used by the agent. Conducted CAs can be directed at various elements of the network and cause different consequences. Thus, an important factor is the absence of contradictions between the executed counteraction scenarios by the agent and the system server, even if there is no OpenFlow control channel between them.