An extended desktop multimedia conference system named FREDERIC (File Retrieval Engineering on Distributed EnviRonment and Interactive Communication system) has been developed for international cooperative work by sharing CAD and image data among multi-point users. This paper describes the basic network design concept of utilizing the Internet as a best-effort service and ISDN as a high-speed guaranteed service. Service system requirements and designs were developed to access common databases and collaborative work of multimedia information those are shared by customers with desktop computers and to allow remote offices to use a plant walkthrough system. The performance of the prototype system especially focused on the file transmission time which is the key factor in developing and constructing the system. By applying the image compression technology of multi-tone entropy coding, it is shown that the short time CAD data transfer to meet the requirements can be achieved.