The analysis of tasks of development and reengineering of computer networks of information-control (I&C) systems of critical technologies (CT) using opened network technologies and the commercial network equipment is executed. Formal tasks of development and reengineering of computer networks I&C systems of CT are formulated and the initial data, necessary for their decision are analyzed. The principles of profile formation bases of the computer networks based on open standards, variants of a network structure and their choice are considered in view of the requirements showed to reliability, quality of service, to functional and other characteristics of computer networks. These procedures can be realized as the tool utilities, which allowing to automate the process of computer systems designing.