The application envisaged for high speed packet switched networks have diverse and demanding transport requirements that are not satisfied by current communications software implementations. In addition, existing communication interfaces for distributed programs are not general enough to express the communication patterns and control required for distributed applications. This Multimedia Applications Development (MAD) system is designed to address these problems mentioned above. It is intended as a platform for implementing and experimenting with protocols and their implementation, network service access methods, and communication primitives for constructing distributed multimedia applications. It is expected that the research will yield real applications that can be used with a campus ATM environment, and that the results will provide deeper insights into how the communication needs of applications can be satisfied more effectively