Scalable Multicast Representative Member Selection

Abstract—In multicast applications requiring receiver feedback, the primary impediment to receiver-set scalability stems from the feedback implosion problem. Some applications only need feedback from a single, representative receiver. For example, an adaptive video server may only need to know the video quality for the worst receiver. Soliciting a response from a receiver with the specific metric value is difficult because a receiver does not know the metric value at other receivers and, therefore, cannot assess if it should report its metric value. Previous work in feedback aggregation solicits a response from any single receiver, not a receiver with some particular metric characteristic. In addition, existing solutions exhibit high application specificity, allowing very little protocol control. We propose adaptation of two existing approaches to representative selection: backoff timers and probabilitistic polls. Both adapted approaches are application independent protocols and allow control over the definition of implosion, probability of implosion, and target metric values. We explicitly consider the inherent tradeoff between implosion and delay. Keywords—Multicast, Feedback, Implosion, Probabilistic Polling