MCA: a rate-based end-to-end multicast congestion avoidance scheme

We propose MCA, a rate-based end-to-end multicast congestion avoidance scheme. Congestion avoidance [6] is different from congestion control in the sense that our scheme detects and responds to network congestion without necessarily inducing packet loss. Our scheme is a single-rate scheme and operates endto-end, i.e., it goes at the rate allowed by the worst congested receiver and does not expect packet marking or other support from intermediate bottlenecks. Congestion is detected autonomously at receivers using the concept of “accumulation” and simple thresholding techniques proposed in our recent unicast work [8]. Congestion feedback to senders can be in the form of single-bit congestion indication (CIs) or as a multi-bit output rate measure. The feedback is sparse in the sense that at most one feedback is generated per measurement period (unlike multiple loss indications generated during packet loss). The source implements two key blocks: a filtering block to discriminate between competing feedback from receivers, and a congestion response block which implements a rate-increase/decrease policy. The two different feedback models (bit-based or explicit rate-based) leads to two different schemes: bit-based and explicit rate-based schemes. Simulation results show that both schemes avoid the drop-to-zero problem and are fair with unicast congestion avoidance schemes.