# Evaluating the Functioning Quality of Data Transmission Networks in the Context of Cyberattacks
## 2 Related Work  
To develop a mechanism for evaluating cyberattack actions and their impact on the functioning quality of data transmission networks, we will briefly review the existing approaches to evaluating the functioning quality of modern data transmission networks used to ensure the stable operation of automated control systems for technological processes. The stated requirement for the use of a data transmission network allows one to distinguish, among a lot of quality indicators, which are standardized by the ITU-T, ETSL, 3 GPP and IETF recommendations and existing locally produced directive documents, only those indicators that conform with the requirements imposed by the control system of technological processes for the information exchange process. Among such indicators, we can choose:  
* data transmission path capacity, characterized by the average data transmission speed;
* the probability of data loss, estimated by the value of the probability of packet loss;
* data delay time, calculated as the average delivery time of a message (data packet) and jitter of the specified time. In this case, the mechanism, which is under development, should take into account the randomness of flows transmitted in modern technological data transmission networks and their features, among which the main ones are significant nonstationarity and pulsations with long-term dependencies, explained by the existence of self-similarity (fractality) in the data flow [9; 10; 11; 12]. In [10; 13; 14; 15; 16; 17], an approach is proposed for the calculation of the packet loss probability, based on the usage of fundamental expressions, obtained for queuing systems M/M/1, taking into account the flow categorization and the claim operation discipline with the introduction of equalizing coefficients, considering the traffic variability [13], the Hurst index [10; 14] and related parameters [15; 16; 17]. These works surely make a noticeable contribution to the development of the methods of teletraffic theory, but they do not take into account the impact of cyberattacks on packets losses. The works [18; 19; 20; 21; 22] are focused on the calculation of the probabilistic and temporal characteristics of the data transmission network, such as the average data transmission speed, average queueing time and delay time jitter. In this case, the main attention in calculating the required values is given to taking into account the self-similarity of the transmitted data flow. In our opinion, the analysis of calculation methods has been carried out more completely in [22], where relations for determining the distribution functions of the data delay time, taking into account the categorization of the transmitted flows and their self-similarity. In this case, the distribution functions of the waiting time and the service time are approximated by exponential distributions. At the same time, the analysis of the Laplace-Stieltjes transformation of the service and waiting time distribution function given in [21; 22] shows that this distribution is not exponential, therefore the delay time distribution is not exponential either; this distribution is defined as an integral convolution of the service and waiting time distributions. Besides that, the results given in these works do not take into account how results of the cyberattack implementation by a malefactor influence the value of the calculated parameters. To evaluate the functioning quality of DTNs and to evaluate the protection mechanisms of telecommunication networks, in [7; 8; 23] it is proposed to use a complex of GERT models that allows one to estimate the average time and dispersion of the metadata file transmission time, organization and delivery time of control transfer commands to a software client of the telecommunication network.