The article reflects the views of the authors on the method for the operational calculation of the indicator of the functioning of special-purpose information and telecommunication networks of the tactical level of control according to the criterion of "network availability". Improvement of weapons and military equipment, forms and methods of combat, as well as a change in views on command and control, put forward ever more stringent requirements for the information and telecommunication system in general and for its elements in particular. The problems of development, planning of combat use and operation of information and telecommunication networks of the tactical control level are their heterogeneity, since they use heterogeneous transmission systems (radio and wire) together. The characteristic features of the planning, deployment and operation of information and telecommunication networks of the tactical control level are a high degree of uncertainty in the characteristics of their functioning and the lack of initial data in planning, which necessitates the improvement of the methodological basis for conducting operational calculations. Based on the analysis of ITU-T recommendations, scientific publications and the practice of combat use of the defense forces, it becomes clear that the operational calculation of individual criteria and indicators of the functioning of information and telecommunication systems of the tactical control level needs to be improved, since these systems have their own characteristic features. The material presented in the article makes it possible to develop new approaches to solving the problem of a reasonable calculation of the required bandwidth of the access node of the information and telecommunications network of the tactical control link. The significance and value of this study lies in the fact that in the conditions of continuous improvement of the forms and methods of warfare, high dynamism of changes in the states of information and telecommunication systems of the tactical control level, the correct choice of the apparatus for assessing the decisions made should play a decisive role in shortening the deployment planning cycle and sustainable functioning of the system management.