IQ-RUDP: Coordinating Application Adaptation with Network Transport

• Authors: Qi He;Karsten Schwan
• Venue: HPDC '02 Proceedings of the 11th IEEE International Symposium on High Performance Distributed Computing
• Year: 2002

Our research addresses the efficient transfer of large data across wide-area networks, focusing on applications like remote visualization and real-time collaboration. To attain high performance in the real-time exchange of data across collaborating machines and end users, we are developing and evaluating methods and techniques for coordinating application-level with network transport-level adaptations of data communication. Specifically, complementingprevious work on TCP-friendly communication and on adaptive transport protocols, our approach is to strongly coordinate application-level with transport-level changes in communication behavior, so as to best meet application needs without violating fairness in network resource usage. The approach is evaluated with the IQ-ECho middleware, which implements the distribution of scientific data to remote collaborators. Using IQ-ECho, application-level adaptations like selective data down-sampling are triggered by transport-level information provided by the instrumented IQ-RUDP protocol underlying IQ-ECho's communications. The application- to network-layer exchange of information necessary for such coordinated adaptations is implemented with ECho attributes, which provide a lightweight way for an application to provide quality of service information and to describe its adaptation to the transport layer, and for IQ-RUDP to share network status information with an application. In addition to triggering application-level adaptations and reacting to certain changes in network state, IQ-RUDP also re-adapts its own communication behavior after an application adaptation has been performed, in part to remain fair to other network flows. Such transport-level reactions can be performed at higher rates and with smaller overheads than possible at application level. Coordination in adaptation avoids conflicts due to mismatched application vs. transport-level adaptations, and it avoids over-reaction due to changes performed simultaneously at multiple levels. In addition, by permitting IQ-RUDP to adjust its behavior independently, mismatches in the application- vs. network-level granularities of adaptation can be ameliorated. Finally, since IQ-RUDP can adapt independently, it can compensate for application-level adaptations that made decisions based on obsolete information.