## 2 Operational Technology Networks Specifics  
A significant difference between classical IT networks and OT networks is their purpose and related use. OT networks have the main purpose of controlling and monitoring the industrial process, whereas IT networks aim mainly at data transmission (by nature non-critical in comparison with OT networks). Another distinction is the elements and components of the individual networks themselves. IT networks use end stations (laptops, desktop PCs, mobiles, tablets, etc.). Network elements and infrastructure provide data transfer mainly between end-user elements using data stored on servers (located and connected to the Internet). On the other hand, OT networks typically use specific devices with a well-defined purpose to provide/monitor a specific activity within an industrial process. These can be single active/passive elements (actuators and sensors), control PLCs, HMIs (providing visualization of the current process status to the operator), or SCADA/DCScomponents. Another difference is the data transmitted itself and the typical orientation of the data flow. Within \(\Pi\), it is mainly the use of data obtained from higher layers (Internet) and its local modification/processing/consumption by the user. OT networks mainly generate data from sensors and perform operations by actuators. Thus, the data occurring in an industrial network mainly contains data acquired from sensors (temperature, pressure, speed--numerical data), and based on these data, actuators (motors, pumps, valves--binary state I/O) are activated/deactivated [4]. Another major difference is the security of individual networks. IT networks are evolving at a very fast pace, the lifetime of equipment within IT networks is typically 3-5 years (servers, workstations, laptops and network components), and the frequency of updates is also very high. Systems and software are regularly updated and upgraded to improve performance, security, and functionality. In terms of basic requirements, the priority is security, i.e., confidentiality of data, followed by data integrity, with availability (CIA triad) coming in third. Thus, it is necessary to transfer the data primarily in a confidential manner (encryption), ensuring their integrity (preserving the content without modification), followed by their availability (slight delays and outages are tolerated to provide more critical services--there is no security risk not to deliver the message immediately). In contrast, OT networks are completely identical in these aspects. Development within OT is slow and gradual, equipment lifetimes are typically 10-20 years (i.e., decades), so the frequency of updates is conducted at large intervals (industrial process is affected--creating downtime and slowing production efficiency). Systems often require long-term stability and reliability, which means that updates or changes are made less frequently to avoid the risk of disrupting critical operations [4]. In terms of basic requirements, the priority is data and service availability, followed by integrity and thirdly confidentiality (AIC triad). It is, therefore, necessary to have available data from the industrial process at all times to be able to monitor and manage the process adequately and in a timely manner. This is important because of the nature of OT networks, where critical parts are controlled and where there is a risk of malfunction or danger to human health in the event of a process disturbance (nuclear power plants, thermal power plants, etc.). It is also necessary that data integrity is preserved, and only after these tears are preserved is the safety considered. IT and OT networks differ in the nature of the services they provide in terms of their importance. They differ in terms of priorities and especially in terms of the security of the data transmitted. They also differ in the subject/scope of the data transmitted. They also differ in the individual elements of the network.