Zhichen Xu

RITA: receiver initiated just-in-time tree adaptation for rich media distribution

Application-level multicast networks overlaid on unicast IP networks are increasingly gaining in importance. While there have been several proposals for overlay multicast networks, very few of them focus on the stringent requirements of real-time applications such as streaming media. We propose RITA (Receiver Initiated Timely Adaptation) framework for an efficient overlay multicast infrastructure. RITA is based on a combination of landmark clustering and RTT measurements, and is particularly suitable for multimedia real-time applications. Our goal is to balance the network-oriented goals of building an efficient multicast tree with the application-oriented goals of providing good QoS with minimal disruptions. Using accurate global soft state information tables, our approach promptly constructs and reconfigures high quality trees. A distinguishing feature of our approach is that the tree reconfiguration is initiated just-in-time by the application client at the receiver when the media quality falls below a specific threshold. The goal is to achieve dynamic tree reconfiguration with very low switching delay such that end users do not perceive any application performance degradation.

Service adaptive multicast for media distribution networks

Multicast technology is highly efficient for the large scale multimedia content service delivery. Its efficiency is maximized when all the service recipients have identical needs. In reality however, the end users may have a heterogeneous set of requirements for different service levels as well as different service components, depending on their system and network capabilities. We propose the notion of service adaptive multicast (SAM) that balances the tradeoffs between providing individualized service to each client and maintaining an efficient overlay multicast tree structure. The novel aspects of our approach are (a) the ability to augment and transform existing paths into service paths with the desired attributes; and (b) integration of two tree maintenance processes: a receiver-initiated just-in-time adaptation of the multicast service tree driven by application/user perceived QoS, and a demand-driven tree maintenance process geared towards long-term tree quality. We demonstrate the performance of our approach using simulations of large client population.