The internetworking capability of a network is typically provided transparently by protocols below the network application interface. However, network designs have been implemented in which the internetwork function is limited or absent. This paper describes one way to add transparent internetworking to such systems without affecting the existing network hardware and software. The solution consists of using application-level software and gateways that project a domain structure onto application names in such a way that neither the applications nor the underlying protocols need be aware of internetworking. A research prototype of this internetworking scheme has been implemented in the context of the NETBIOS application interface; the paper discusses its key features and the lessons learned. Copyright © 1987 by The Institute of Electrical and Electronics Engineers, Inc.