A video conferencing testbed on ATM: design, implementation and optimizations

This paper describes our experiences with the design and implementation of a very high-end video conferencing testbed on an ATM network. Our system is built on an IBM RISC System/6000 equipped with prototype hardware for video and audio capture and compression, and an IBM 100 Mb/s ATM adapter. In our early experiments we used UDP/IP running over ATM Adaptation Layer 5 (AAL5) for data transfer between peers. Our initial experiences with the system indicated that the overall system performance did not match our expectations even though most of the video, audio, and network processing was performed in hardware. A thorough profiling of the system revealed that the protocol processing and data handling overheads in the end-host are responsible for the poor video/audio quality. Based on these observations, we have proposed and implemented changes to the protocol data path that can significantly improve the performance of the system. Although we discuss our solution in the context of a video conferencing application, our approach is general and can be applied to many other applications. It is particularly useful for applications that are required to handle large volumes of time-critical data, such as multimedia servers.