Most current management systems employ graphic-user-interface displays to visualize the networks being managed. Some networks are so large that it is difficult to display all network elements in a single window alone, and therefore, the hierarchical multi-window style presentation is commonly used. This form of presentation has disadvantages, however, including the fact that window manipulations are complex. Our approach (bifocal network visualization) is able to display both the context and any detail of a network within a single window, and overcomes the disadvantages of hierarchical multi-window presentation. We implemented this bifocal network visualization on a workstation using a frame buffer memory called DUALQUEST that is able to generate images in real-time and is simple to operate. This paper describes bifocal network visualization and its implementation. Furthermore, we present an experiment to compare our interface with conventional hierarchical multi-window presentation.