The paper addresses a particular type of IT infrastructure development. It discusses the architecture of the Corporation’s network data processing centre of IT infrastructure, which is designed to provide reliable, scalable and available communication with the network at both the physical and logical levels following the requirements of the enterprise. To ensure the proper network services for application programs, the network architecture should be designed considering the security system architecture, which sets specific requirements at the structural (devices) and logical (configurations) levels. The following requirements were met when designing the network architecture: availability, security, scalability, manageability, support, consolidation, and interoperability. The paper discusses an example of a data transmission network for Ukrtelecom, the national electronic communications operator. The Corporation’s network is logically divided into security zones using perimeter protection services. Seven main security zones have been established in the Corporation. A method of extreme partial flows is presented to optimise the technical parameters of the network. The algorithm of the iterative method of extreme flows for determining the data transmission network throughput for a given load in directions is described, allowing the determination of the optimum load distribution by the maximum flow of communication lines and network nodes for each direction. The method enables measuring the TN throughput for a given load across the directions and determining the optimum load distribution by the maximum flow of communication lines and network nodes for each direction.